Persistent semiquinone radicals enable efficient near-infrared-driven H_2O_2 photosynthesis

Domain: chemistry
Published: 2026-03-02
Editorial outcome: major_revision

Abstract
Photosynthesis of H2O2 under sunlight is a sustainable method; however, most developed photocatalysts utilize limited near-infrared light, which accounts for 52% of the solar spectrum. In typical near-infrared photocatalysts, excited electrons fall into low-energy sub-gap states, reducing the driving force for H2O2 generation. Here, a polydopamine-loaded porphyrin supramolecular photocatalyst efficiently utilizes near-infrared light for H2O2 production from H2O and O2, achieving an apparent quantum yield of 2.8% at 1020 nm. This substantial near-infrared utilization significantly boosts activity under full-spectrum irradiation, with an H2O2 generation rate of 3.37 mM/h and solar-to-chemical conversion efficiency of 2.2%. Persistent semiquinone radicals in polydopamine are demonstrated to enable ultrafast sub-gap electron transfer (ca. 79 fs) from porphyrin to polydopamine and facilitate near-infrared-driven •OOH radical generation, thereby accelerating H2O2 production. This study sheds light on the potential of near-infrared-responsive photocatalysts and offers insights into optimizing their performance for sustainable H2O2 synthesis.

Introduction
Hydrogen peroxide (H2O2) has emerged as a prominent green oxidizing agent with widespread applications in medicine, bleaching, and environmental remediation.1, 2 The current global market for H2O2 is valued at ca. 6 billion dollars, with projections indicating growth to ca. 10 billion dollars by 2030.3 Traditionally, H2O2 is synthesized industrially via the anthraquinone process, which relies on high-pressure conditions, costly palladium catalysts, and explosive hydrogen gas.4 In recent years, photocatalytic methods have gained attention as a sustainable alternative for producing H2O2 using water (H2O), oxygen gas (O2), and sunlight in the presence of suitable photocatalysts. To maximize the utilization of solar energy, the photocatalysts are expected to efficiently harness near-Infrared (NIR, λ > 800 nm) light, which constitutes approximately 52% of the solar spectrum. However, most developed NIR-responsive photocatalysts suffer from significant limitations5, 6,7, 8, including low H2O2 production rate (e.g., ~100 μM/h), a narrow NIR-responsive range (λ < 900 nm), and minimal contribution from NIR light (< 10 %) to overall activity under full-spectrum illumination.

Tetrakis(4-carboxyphenyl) porphyrin (TCPP) supramolecule exhibits remarkable NIR photocatalytic activity for H2O2 production through a novel dual-pathway mechanism.9 Unlike previously reported photocatalysts, which rely solely on oxygen reduction (ORR) for H2O2 generation, the TCPP supramolecule demonstrates both ORR and water oxidation reduction (WOR) to produce H2O2. Specifically, ORR occurs on the pyrrole ring, while WOR is driven by photo-thermal transitions involving the carboxylic groups and peroxy acid intermediates (Figure 1a). Notably, a key feature of the TCPP supramolecular photocatalyst is its light absorption capability extending into the NIR region (up to 1100 nm). Under monochromatic NIR light (940 ± 10 nm), SA-TCPP achieves a H2O2 production rate of 0.15 mM h⁻¹, with an apparent quantum yield (AQY) of up to 1.1%. Despite these advancements, the contribution of NIR-driven activity to the overall photocatalytic performance remains limited. In most NIR-responsive photocatalysts, electrons excited by NIR light primarily transition to sub-gap energy levels (trap states)10, 11, which possess lower energy than the conduction band, reducing the potential driving force for effective H2O2 production (Figure 1b). Consequently, this inherent energy limitation may hinder the efficient utilization of NIR light in TCPP-based systems. Radicals generated within the photocatalyst framework have been reported to smoothly mediate ORR to H2O2 by facilitating the utilization of electrons in the conduction band12. However, the generation of such reactive radicals typically requires UV or visible excitation. Moreover, under NIR irradiation, even when •O2- or HOO• intermediates during H2O2 production are generated by such internally formed radicals, they exhibit a strong tendency toward back reactions originating from rapid electron-hole recombination.

Besides the inherent energy limitation, the high energy barrier for the ORR to H2O2 further constrains the efficient utilization of sub-gap NIR-excited electrons. Thermodynamically, effective ORR requires that the conduction band edge potentials be more negative than the reduction potential of O2 to H2O2 (0.68 V vs. RHE).13 During the actual ORR process, O2 is initially reduced to free or adsorbed •OOH intermediates, followed by the subsequent reduction of these intermediates to H2O2. While the further reduction of •OOH intermediates to H2O2 occurs at potentials around 1 V, their initial formation requires a more negative potential (approximately 0.30 V vs. RHE, based on the average of reported data).14, 15, 16 Accordingly, the ability to form •OOH intermediates using NIR-excited electrons occupying sub-gap states plays a crucial role in the efficient utilization of NIR light for H2O2 production.

This study addresses the challenge of utilizing NIR light for H2O2 photosynthesis by integrating polydopamine (PDA), a well-established full-spectrum absorption material17,18, onto self-assembled TCPP porphyrin supermolecules (SA-TCPP). Although PDA has been employed to promote the photocatalytic H2O2 production19, its use to enhance NIR-driven H2O2 generation remains rare, despite its broad solar-spectrum absorption. Moreover, while radical-mediated fast electron transfer has been reported12, the utilization of the persistent semiquinone radicals intrinsically present in PDA to mediate the transfer of low-energy, NIR-excited sub-bandgap electrons remains poorly understood.

Here, we investigate H2O2 generation from only H2O and O2 using PDA/SA-TCPP composite photocatalysts, demonstrating that NIR-driven ORR contributes nearly 30% to the overall activity. By enhancing NIR utilization, the overall H2O2 generation rate reaches 3.37 mM h-1, with a solar-to-chemical conversion efficiency (SCC) of 2.2%. We elucidate the mechanism by which persistent semiquinone radicals in PDA facilitate rapid transfer of NIR-excited sub-gap electrons in SA-TCPP, promoting the formation of •OOH radicals and H2O2. This work establishes persistent semiquinone radicals as effective electron shuttles for driving NIR-excited sub-gap ORR-to-H2O2 conversion, providing guidance for the design of efficient organic photocatalysts for scalable solar H2O2 production under sunlight.

Results
Theoretical feasibility of semiquinone-mediated sub-gap ORR of SA-TCPP under NIR light

PDA is synthesized via a self-polymerization method using dopamine monomers. The structural composition of the prepared PDA, shown in Figure 1c, includes dihydroxyindole (hydroquinone-type, QH2), and indoledione (quinone-type, Q) units with varying degrees of (un)saturation. This structural characterization is confirmed through the Fourier transform infrared (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS) (Supplementary Fig. 1-3) measurements, consistent with findings reported in the literature.19,20 Scanning electron microscopy (SEM) images in Supplementary Fig. 4 reveal that the prepared PDA exhibits a nanoparticle morphology, with particle sizes ranging from 50 to 250 nm. Electron Paramagnetic Resonance (EPR) is further employed to elucidate the PDA structure. A distinct signal at g = 2.0035 with a line width of 5.5 G is observed for the PDA powder. (Supplementary Fig. 5) This is attributed to the presence of substantial persistent semiquinone radicals (SQ•), consistent with previous reports.21, 22

Ultraviolet-Visible-Near Infrared diffuse reflection spectrum (UV-Vis-NIR DRS) in Supplementary Fig. 6 shows the absorption band edge of the prepared PDA extends up to 1400 nm, attributed to the stacking of indole conjugated structural units. This absorption profile together with the band structure analyses (Supplementary Fig. 6) demonstrates a large overlap with the solar spectrum, encompassing not only the visible light region but also the NIR region, indicating the strong potential of PDA for NIR-light responsiveness.

To further explore the theoretical ORR pathway for H2O2 production on PDA and verify the NIR utilization, Gibbs free energy calculations are performed (Figure 1c). The formation energy of SQ• radicals from QH2 and Q is only 0.38 eV, indicating that the generation of SQ• radicals is highly favorable and supports their persistent presence within the PDA structure. Comparable formation energies (0.2-0.5 eV) have also been reported for other SQ• systems.23 Both the reaction barrier for SQ• radical generation from QH2/Q and the subsequent O2 addition to SQ• to form adsorbed Q*OOH are lower than the energy provided by NIR photons(energy < 1.55 eV), indicating that these steps are energetically accessible under NIR excitation. However, the formation of H2O2 requires the desorption of the *OOH intermediate followed by its reaction with a neighboring SQ• or QH2 unit. In contrast, the subsequent desorption of the *OOH intermediate and its conversion to H2O2 via reaction with neighboring SQ• or QH2 units involves substantially higher activation barriers (TS3-1,2) that exceed the energy accessible under NIR excitation, rendering these steps kinetically unfavorable. EPR measurements are conducted for PDA to examine its NIR-light driven •OOH generation from ORR. The experiment is conducted in the dark and under NIR light irradiation within an anoxic environment, using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as the •OOH radical trapper (Figure 1d). The anoxic environment is specifically used to slow down the O2 reduction on PDA, allowing the accumulation of intermediates. In the dark, PDA exhibits negligible signals of •OOH radicals, indicating that O2 is not spontaneously reduced on PDA. In contrast, a distinct semiquinone radical (SQ•) is observed, consistent with the EPR signals for powders (Supplementary Fig. 5). With NIR irradiation, adduct EPR signals are observed. The signals consist of the SQ• radical adduct, with an intensity 2.6 times as high as that in the dark, along with newly emerged •OOH radicals, as confirmed by simulation results (details in Supplementary Fig. 7). The result suggests •OOH radicals are generated from 1 electron transfer from SQ• radicals to O2. Previous studies have demonstrated that SQ• radicals exhibit high reaction rate constants with O2 (106~108),24, 25 further supporting our observations.

In-situ attenuated total reflectance infrared absorption (ATR-FTIR) spectroscopy is employed to investigate the NIR-light response of the prepared PDA. The experimental setup is illustrated in Supplementary Fig. 8, incorporating a silicon (Si) prism as the IR-transparent element. The absorption changes, determined by subtracting the baseline signal of the pristine PDA surface, provide insights into the surface reactions of PDA with H2O and O2 under NIR irradiation. Under NIR light irradiation (λ > 800 nm), distinct vibrational peaks at 1112 cm⁻¹ and 842 cm⁻¹ are observed. They are attributed to stretching vibrations of the adsorbed •OOH radicals and O-O in the radicals (Supplementary Table S1). Additional in-situ FTIR observations with 18O isotopic labeling further confirm that the observed peak changes belong to •OOH radicals generated onto the PDA surface (Supplementary Fig. 9). Control experiments with different light wavelength cutoff filters verify that this PDA-induced generation of •OOH radicals enables substantial NIR utilization with the light wavelength extending up to 1020 nm (Supplementary Fig. 10).

With increasing irradiation time from 0 to 30 min (Figure 1e), the intensity of the two peaks at 1112 cm⁻¹ and 842 cm⁻¹ increases. However, after the light is turned off, the intensity of these peaks gradually diminishes to nearly negligible levels, indicating that NIR light-induced •OOH generation is highly reversible. Furthermore, the prepared PDA exhibits negligible H2O2 generation under NIR irradiation (Supplementary Fig. 11), suggesting that the generated •OOH radicals cannot be further reduced, reinforcing the high reversibility of •OOH generation under NIR light. Under NIR light irradiation, the QH2 and Q moieties may initially interact to increase the amount of persistent SQ• radicals, which subsequently react with O2 to form •OOH radicals and regenerate Q moieties (as supported by FTIR and 13C solid-state nuclear magnetic resonance (NMR) results in Supplementary Fig. 12-13).

While prior studies reported the H2O2 generation on PDA alone (0.5-1.0 mM h-1 g-1) via •OOH intermediates under sunlight irradiation,26 the current work highlights the facile generation of •OOH radicals on PDA under NIR irradiation. Although PDA cannot directly utilize NIR light to produce H2O2, the efficient generation of •OOH radicals on it under NIR irradiation remains crucial for enabling NIR-driven H2O2 production. In particular, in the case of NIR-driven H2O2 generation on SA-TCPP, •OOH radical formation with the excited sub-gap electrons represents a key rate-limiting step (Figure 1b). Therefore, the facile generation of •OOH radicals presents a promising strategy for enhancing the efficiency of NIR-driven sub-gap H2O2 production on SA-TCPP.

The band structure of SA-TCPP is investigated using UV-Vis-NIR DRS to assess the potential for charge transfer from its sub-bandgap states to PDA. As shown in Figure 1f, SA-TCPP displays a strong absorption band around 730 nm and a weak Urbach tail extending from 730 to 1400 nm. These features correspond to a bandgap energy (Eg) of 1.77 eV and an Urbach sub-bandgap energy (EUrbach) of 1.21 eV (Supplementary Fig. 14). The Urbach energy is typically attributed to trap states within the SA-TCPP structure, which may arise from structural distortions, impurities, and lattice imperfections associated with its amorphous nature (as supported by the XRD results in Supplementary Fig. 15). The relationship between Eg and EUrbach is illustrated in the inset of Figure 1f. These trap states are generally distributed both above the valence band maximum (VBM) and below the conduction band minimum (CBM). Ultraviolet photoelectron spectroscopy (UPS) measurements determine the VBM and the trap state level above the VBM to be 1.79 eV and 1.51 eV, respectively. By subtracting Eg and EUrbach from these values, the CBM and the trap state level below the CBM are calculated to be 0.02 eV and 0.30 eV, respectively (Supplementary Fig. 14).

It is noteworthy that in SA-TCPP, the electrons excited by NIR light predominantly accumulate at the trap state level located below the conduction band minimum (CBM), with a potential of 0.30 V vs. RHE. This value is only 0.02 V lower than the reduction potential of O2 to •OOH radicals (0.32 V), indicating a minimal driving force and, consequently, limited utilization of NIR light for •OOH radical generation. In contrast, PDA exhibits a more favorable energetic alignment: the photon energy of NIR light (< 1.55 eV) is substantially higher than the energy barrier (0.51 eV) required for •OOH radical generation (Figure 1c), enabling efficient 1 electron transfer from persistent semiquinone (SQ•) radicals to O2. Furthermore, the quinone moieties formed in PDA during this process possess a redox potential (Q/SQ•) of 0.52 V vs. RHE (Supplementary Fig. 16 and 17), which is 0.22 V positive relative to the trap state level in SA-TCPP (0.30 V vs. RHE). This favorable potential difference suggests that the transfer of sub-gap electrons from SA-TCPP to PDA is thermodynamically viable. Therefore, coupling SA-TCPP with PDA may enhance NIR light utilization through efficient sub-gap electron transfer, as illustrated in Figure 1g.

Boosting H2O2 Generation under NIR Light by loading PDA on SA-TCPP Photocatalysts

To prepare PDA and SA-TCPP composite photocatalysts (PDA/SA-TCPP), an appropriate amount of the prepared PDA nanoparticles is introduced during the self-assembly process used for fabricating TCPP nanosheets.

Figure 2a, b shows the SEM and atomic force microscope (AFM) images of the prepared PDA/SA-TCPP photocatalysts. In the composite structure, small PDA nanoparticles ranging in size from 50 nm to 250 nm with a thickness of ca. 20-80 nm (Supplementary Fig. 18) are predominantly dispersed onto SA-TCPP nanosheets (Supplementary Fig. 19). The particle size of PDA remains similar to its original dimensions before loading onto the SA-TCPP nanosheets, indicating that the material experiences minimal chemical change during the self-assembly process of TCPP.

Figure 2c presents the FTIR spectrum of PDA/SA-TCPP, alongside the spectra of SA-TCPP and PDA recorded as controls to investigate the formation of PDA loading onto the SA-TCPP nanosheet. Owing to the presence of similar functional groups in both compounds, most peaks in the spectra of PDA and SA-TCPP overlap. Nevertheless, three distinct peaks at 1693 cm⁻¹, 1399 cm⁻¹, and 1176 cm⁻¹ are exclusively attributed to SA-TCPP with minimal interference from PDA. Specifically, the peaks at 1693 cm⁻¹ and 1176 cm⁻¹ correspond to the stretching vibrations of C=O and C-O in the carboxyl groups27, respectively, while the peak at 1399 cm⁻¹ is assigned to C=C stretching vibrations in the pyrrole ring of the porphyrin structure.28 Upon PDA loading, the peaks associated with the carboxyl groups shift by 17 cm⁻¹ and 9 cm⁻¹ to lower wavenumbers, whereas the peaks associated with the porphyrin core remain unchanged. This shift indicates the formation of hydrogen bonds between the SA-TCPP and PDA.29

The formation of hydrogen bonds between PDA and SA-TCPP is further supported by the UV-Vis-NIR DRS spectra. As shown in Figure 2d, pure PDA has a strong and broad absorption spectrum up to 1500 nm, and the Soret band (corresponding to the S0 → S2 transition) of SA-TCPP appears at 357 nm and redshifts to 385 nm after PDA loading. This redshift is likely attributed to the formation of edge-to-edge hydrogen bonds between PDA and SA-TCPP, which enhance the transition dipole moment, facilitate exciton splitting, and lower the energy of the S2 state.30, 31 In addition, isotope-labeled FTIR, solid-state 13C NMR, and XPS measurements further confirm the presence of hydrogen-bond interactions between PDA and SA-TCPP (Supplementary Fig. 20-21). The hydrogen-bonding is expected to contribute to the stabilization of PDA on the SA-TCPP nanosheet during the catalytic reaction

Next, the H2O2 generation activity of the PDA/SA-TCPP photocatalyst is evaluated. The optimal concentration of the PDA/SA-TCPP photocatalyst in the reaction is 4.0 g/L (Supplementary Fig. 22). Figure 3a shows the time-dependent H2O2 generation on PDA/SA-TCPP under Xe lamp irradiation with λ > 420 nm and λ > 800 nm cutoff filters, respectively. Under the visible + NIR light (λ > 420 nm) irradiation, PDA/SA-TCPP exhibits a high H2O2 generation rate of 3.37 ± 0.32 mM/h in the first hour, reaching a cumulative concentration of 11.24 mM after 4 h. Notably, PDA/SA-TCPP achieves a high H2O2 production rate, placing it among the top-performing photocatalytic systems reported to date (Supplementary Table S2).

Under the NIR light (λ > 800 nm) irradiation, PDA/SA-TCPP still achieves a substantial H2O2 generation rate of 0.99 ± 0.30 mM/h in the first hour, with 3.30 ± 0.26 mM accumulated after 4 h. The H2O2 generation continues to increase with reaction time, which is different from the observations for PDA alone where negligible H2O2 generation is detected (Supplementary Fig. 12). In addition, loading PDA onto pre-assembled SA-TCPP nanosheets yielded a photocatalytic H2O2 generation activity comparable to that of the in-situ self-assembled PDA/SA-TCPP system (Supplementary Fig. 23), indicating that the enhanced activity does not originate from the incorporation of PDA during the self-assembly process. By contrast, a physical mixture of PDA and SA-TCPP is prepared, which exhibited less than half the activity of PDA/SA-TCPP (Supplementary Fig. 24). These results clearly indicate that the integration of SA-TCPP with PDA enables efficient NIR photon utilization for H2O2 production in this photocatalytic system.

Figure 3b depicts the AQY of PDA/SA-TCPP measured at different wavelengths (400-1020 nm). In the visible light region (400-800 nm), the average AQY of PDA/SA-TCPP is 22.3 ± 0.2% at 420 nm (Supplementary Fig. 25), which is 1.9 times higher than that of SA-TCPP and competitive among most reported values for H2O2 generation from H2O and O2 (Supplementary Table S2). In the NIR region, the AQY values of PDA/SA-TCPP at 850 nm, 940 nm, and 1020 nm are 7.1 ± 0.1%, 4.8 ± 0.1%, and 2.8 ± 0.1%, respectively, (Supplementary Fig. 26-27), approximately 3.0-4.0 times as high as those of SA-TCPP (1.6% at 850 nm, 0.87% at 940 nm, and N/A at 1020 nm), which are competitive among most reported NIR light-responsive photocatalysts (Supplementary Table S3). The AQY results confirm that the enhanced photocatalytic activity is attributed to the improved NIR photon utilization enabled by PDA loading.

Figure 3c compares the H2O2 generation rates of PDA/SA-TCPP and SA-TCPP under Xe lamp irradiation with different cutoff filters (λ > 420 nm, 420 nm < λ < 800 nm, and λ > 800 nm) to better understand the contribution of NIR light utilization to overall H2O2 generation. Under visible and NIR irradiation (λ > 420 nm), the H2O2 generation rate of the PDA/SA-TCPP (3.37 ± 0.12 mM/h) is ca. 2.5 times higher than that of the SA-TCPP alone (1.35 ± 0.08 mM/h). Under NIR-only irradiation (λ > 800 nm), PDA/SA-TCPP achieves a rate of 0.99 ± 0.06 mM/h, nearly 7.1 times higher than SA-TCPP (0.14 ± 0.03 mM/h), and contributes about 29% to the total activity under λ > 420 nm irradiation, indicating a substantial enhancement in NIR photon conversion efficiency. By contrast, the enhancement under visible light alone (420 nm < λ < 800 nm) is relatively modest at 1.9 times.

Figure 3d compares the long-term H2O2 accumulation between PDA/SA-TCPP, SA-TCPP, and PDA photocatalysts. Leveraging its superior NIR utilization, which also helps minimize H2O2 decomposition, PDA/SA-TCPP accumulates 52.2 mM H2O2 (0.16 wt%) after 24 h irradiation, which is 2.6 times higher than SA-TCPP alone and 130 times relative to pure PDA. It is worth noting that higher H2O2 generation activity on PDA through chemical (thermal-driven) or photochemical pathways has been reported.26 However, such reactions predominantly occur under neutral or alkaline conditions. Under the acidic conditions used in this study, the H2O2 production via chemical and photochemical pathways are determined to be negligible compared with the H2O2 production observed for PDA/SA-TCPP (Supplementary Fig. 28-31). According to the above, the integration of PDA with SA-TCPP significantly enhances overall photocatalytic H2O2 production under broad-spectrum light, primarily due to improved NIR light utilization.

Rapid sub-gap electron transfer enabling efficient NIR Utilization

The NIR photocatalytic activity enhancement mechanism for PDA/SA-TCPP is studied next. In the PDA/SA-TCPP system, the peroxy acid intermediate—similar to that in SA-TCPP—is still observed under irradiation by comparative 13C NMR, 1H NMR, TOF-MS, and FTIR analyses of PDA/SA-TCPP and SA-TCPP after room temperature reaction. (Supplementary Fig. 32) The similarity of the spectra excludes hole transfer from SA-TCPP to PDA, which indicates that holes remain on SA-TCPP. Further scavenger experiments (Supplementary Fig. 33) suggest the contribution of holes to the NIR-driven H2O2 production is nearly half similar as we reported in the SA-TCPP. KPFM measurements (Supplementary Fig. 34) of PDA/SA-TCPP before and after light irradiation further indicate that the photogenerated holes remain predominantly on SA-TCPP rather than transferring to PDA. These accumulated holes may oxidize the carboxyl groups on SA-TCPP to form peroxy acid intermediates (-COOH + 2h+ + H2O → -CO3H + 2H+). Subsequently, the generated -CO3H undergoes thermal hydrolysis—the primary role of heat throughout the photothermal catalytic process, as supported by the data in Supplementary Figure 30-31, thereby regenerating -COOH and yielding H2O2 (-CO3H + H2O → -COOH + H2O2)9. Moreover, PDA loading onto Zn-TCPP, with a similar structure to SA-TCPP, enhances H2O2 generation by eightfold (Supplementary Fig. 35). In-situ XPS shows the electron transfer from SA-TCPP to PDA on light. (Supplementary Fig. 36) The results show that PDA loading promotes electron transfer to accelerate the ORR to H2O2 under visible light, which is consistent with previous studies.32,33 However, while this electron transfer explains the activity boost, it does not account for the much greater enhancement under NIR light (7.4 times) compared to visible light (1.9 times).

We then conduct control experiments to elucidate the effect of PDA on the NIR activity enhancement. We employ capacitance measurements, specifically utilizing Mott-Schottky (M-S) curves (Supplementary Fig. S37), both in the dark and under NIR irradiation, to investigate the transfer of NIR light-excited electrons from SA-TCPP to PDA. Generally speaking, in the M-S curves, the slope at low bias reflects the charge density at defect levels, while the one at high bias reflects the charge density in the band.34 Supplementary Figure 37a shows that in SA-TCPP, the slope of the curve at a low bias (-0.1-0.2 V) remains unchanged before and under irradiation, suggesting most NIR-excited electrons at defect levels recombine with photogenerated holes. In contrast, Supplementary Figure 37b shows that in PDA/SA-TCPP, the slope decreases significantly, accounting for the defect electron density estimated to be 8.1×1016 cm-3 and 1.3×1017 cm-3 before and under NIR irradiation (Supplementary Fig. 37c). Note that for PDA-alone, little contribution to this variation is observed after NIR irradiation (Supplementary Fig. 37d). The increase of defect electron density for PDA/SA-TCPP after NIR light irradiation indicates more NIR light-excited electrons transfer from trap levels to PDA rather than bulk recombination.

To gain further insight into the charge transfer, femtosecond transient absorption spectra (fs-TAS) of PDA/SA-TCPP and SA-TCPP are recorded. (Figure 4a and 4b) The pump wavelength is set at 660 nm (S0 → S1 transition) to more accurately probe electron relaxation and transfer at the trap levels 35, 36. For SA-TCPP, a ground-state bleaching (GSB) signal appears at 779 nm at 20 fs. At longer delay times (> 170 fs), SA-TCPP exhibits an excitonic-state absorption (ESA) signal at 792 nm, and by 550 fs, two additional ESA signals emerge at 824 nm and 858 nm through an intersystem crossing (ISC) process.37, 38 The signals at 779 nm and 792 nm are attributed to the 1T states of SA-TCPP coupling with the electron spin. Notably, the peak intensities of the 824 nm and 858 nm signals remain essentially unchanged with further increasing the decay time, suggesting that photogenerated electrons localized at these trap states hardly undergo transfer and are prone to recombination with valence-band holes.

In contrast, PDA/SA-TCPP displays distinct decay behavior compared to SA-TCPP. The GSB signal shifts to 792 nm. Although trap-state signals also appear at 560 fs, as observed in SA-TCPP, their intensity decreases with increasing delay time. At 640 fs, the peak at 824 nm diminishes, accompanied by the emergence of a new peak at 899 nm. As the delay time further increases to 690 fs, 730 fs, and 790 fs, the trap-state signals continue to decrease, while the 899 nm peak shifts progressively to 944 nm and 1026 nm. This rapid decay likely reflects efficient interfacial electron transfer from SA-TCPP to PDA.39 Meanwhile, the overall signal intensity is an order of magnitude stronger than that of SA-TCPP, highlighting the efficient utilization of trap-state electrons enabled by PDA loading.

Transient absorption kinetics at 824 nm are then compared for SA-TCPP and PDA/SA-TCPP to analyze exciton decay dynamics at trap states with and without PDA loading (Figure 4c). Lifetimes and amplitudes at the fitted wavelengths are summarized in Supplementary Table S4. A bi-exponential model is employed to fit the decay curves, where τ1 corresponds to polaron formation from excitons and τ2 to polaron separation, with an additional constant term accounting for recombination processes beyond the measurement window40. For SA-TCPP, τ1 and τ2 are determined as 380 fs and 225 ps, respectively. In contrast, PDA/SA-TCPP exhibits much faster dynamics, with τ1 of 79 fs and τ2 of 7.14 ps. These results demonstrate that PDA loading drives excitons at the trap states of SA-TCPP to form interfacial polarons instead of bulk polarons. Compared with bulk polaron formation without PDA, interfacial polaron formation is 5-fold faster, and their subsequent dissociation into free charges is 30-fold more efficient. The TRPL results further confirm that the acceleration of charge separation after PDA loading (Supplementary Fig. 38).

A schematic summary of the exciton processes in SA-TCPP and PDA/SA-TCPP together with the calculated absolute energy levels are shown in Figure 4d and Supplementary Fig. 39. The presence of PDA clearly enhances interfacial charge transfer by forming interfacial polarons. Notably, the transferred electrons in PDA/SA-TCPP exhibit a longer recombination lifetime (> 8 ns) compared with those in SA-TCPP (> 2 ns), as indicated by the offset constants of the TAS signals at 1026 nm and 824 nm, respectively (Supplementary Fig. 40). In PDA/SA-TCPP, the transferred electrons on PDA eventually occupy the LUMO states, where they can be further captured. Since the TAS spectra display sequential ESA features at 899 nm, 944 nm, and finally 1026 nm after PDA loading, the 1026 nm peak is attributed to electrons localized in the PDA LUMO states, while the 899 nm signal likely corresponds to the LUMO+2 orbitals. These LUMO+2 states, originating mainly from persistent SQ• radicals (the orange orbital mapping shown in Figure 4d), facilitate electron transfer from trap states of SA-TCPP probably by providing additional electron-pair energy. The acceleration of charge transfer mediated by the SQ•-related LUMO+2 states was further supported by subsequent experimental evidence. The involvement of SQ• in ultrafast sub-gap electron transfer is further supported by TAS measurements performed after suppressing SQ• (Supplementary Fig. 41). Upon SQ• suppression, the interfacial trap-electron transfer process is prolonged, ranging from 570 fs to 820 fs, whereas with SQ•, it ranges from 590 fs to 690 fs. The TAS spectra further demonstrate that the trap-electron transfer proceeds via hydrogen-bonding interactions (Supplementary Fig. 42). Moreover, analyses of the interfacial electron density difference, Bader charge, and density of states are consistent with these observations (Supplementary Fig. 43).

To further verify that the trap electrons in SA-TCPP can be more effectively utilized for •OOH radical generation upon PDA loading and elucidate the role of SQ• radicals on H2O2 production, EPR measurements are carried out in air and anoxic conditions. As shown in Supplementary Fig. 44, PDA/SA-TCPP exhibits a pronounced •OOH radical signal under NIR irradiation, verified by radical-quenching experiments and isotope-labeling FTIR results (supplementary Fig. 45-47), markedly stronger compared with pristine SA-TCPP. The EPR fitting results together with quantitative H2O2 analysis further demonstrate the effective utilization of trap electrons for •OOH radical and H2O2 production is mediated by SQ• (supplementary Fig. 48). In addition, transient photocurrent responses and electrochemical impedance spectroscopy (EIS) measurements (Supplementary Fig. 49 and Table S7) also reveal that PDA loading enhances the transfer of NIR-excited trap electrons from SA-TCPP to PDA. The transferred trap electrons subsequently facilitate the further reduction of •OOH radicals adsorbed on Q moieties of PDA to form C-OOH intermediates (TS-1 in Figure 1c) and then spontaneously hydrolyze to form H2O2, as confirmed by in situ FTIR and in situ Raman analyses (Supplementary Fig. 50). Because this pathway avoids the desorption of •OOH radicals from Q moieties (Figure 1c), the electron transfer for their further reduction will be more favorable than the direct reduction of •OOH radicals in PDA alone. Also note that although the formation of •OOH and H2O2 may consume SQ• by converting it to Q, subsequent electron transfer from SA-TCPP efficiently regenerates SQ•, as illustrated by the quantitative EPR analysis before and after the extended reaction in Supplementary Fig. 51. According to the above discussions, the complete H2O2 production process mediate by SQ• radicals is summarized in Supplementary Fig. 52.

The enhancement of NIR utilization by combining PDA with persistent SQ• radicals is also verified in additional systems. Four NIR-adsorption photocatalysts41,42, including Bi12CoO20, Black-TiO2, (Tetracarboxyphthalocyaninato) cobalt (II), and Zn-TCPP, are selected as model systems. Upon PDA loading, each material exhibits an approximately 2~8-fold increase in photocatalytic activity compared with its pristine counterpart, demonstrating the general applicability of the PDA modification strategy. (Supplementary Fig. 53).

H2O2 generation on PDA/SA-TCPP photocatalysts under simulated and real sunlight

Encouraged by the high NIR-driven H2O2 production originating from rapid charge transfer from the trap states of SA-TCPP to PDA, we further evaluated the performance of PDA/SA-TCPP under both simulated and real sunlight. Figure 5a shows the H2O2 generation activity of PDA/SA-TCPP when the reaction suspension is irradiated and heated solely under simulated sunlight (AM 1.5G). The H2O2 generation rate reached 1.07 ± 0.11 mM h⁻¹, corresponding to an SCC efficiency of 2.2%. This value is nearly twice that of pristine SA-TCPP, and it is competitive among most reported photocatalysts (Supplementary Table S2). Notably, besides the rapid charge transfer, the high SCC may also be owing to the superior NIR photothermal conversion of PDA compared to SA-TCPP alone. In Supplementary Fig. 54 and 55, the solution temperature of PDA/SA-TCPP rapidly increases to 369.45 K within only 40 min of irradiation, nearly 30 K higher than that of SA-TCPP. This intrinsic heating effect also alleviates the need for external thermal input that is otherwise required in standalone SA-TCPP systems to sustain high H2O2 generation activity.

The stability of PDA/SA-TCPP is then examined. In ten consecutive cycles (40 h in total), an average of 3.76 mM H2O2 is produced per cycle without any observable activity decay. (Figure 5b) FTIR spectra and SEM images after the cycling reaction confirm negligible morphological and structural change in PDA/SA-TCPP before and after the stability tests (Supplementary Fig. 56). Long-term operation under AM 1.5G illumination for three extended cycles (72 h, Supplementary Fig. 57) also demonstrated stable performance, with each cycle yielding 14.67 mM H2O2. Motivated by this durability and efficiency, we further evaluated H2O2 generation using a lab-built reaction–evaporation device (Supplementary Fig. 58). Remarkably, the device produced H2O2 at a concentration of 1.6 wt% within 10 h, reaching a commercially relevant level.

Next, we perform outdoor tests under natural sunlight for H2O2 generation in the air to further confirm its robustness. For three consecutive days using the same photocatalyst, the PDA/SA-TCPP powder achieves a SCC efficiency of 1.81% in average, slightly lower than that obtained under laboratory conditions due to solar intensity and solution temperature (Supplementary Fig. 59 and Table 8). Moreover, the photocatalyst film is cast onto a Petri dish with a diameter of 10.8 cm. In particular, the PDA/SA-TCPP powder is ultrasonically dispersed in ethanol, and the resulting suspension is poured into the Petri dish and dried at room temperature to obtain a film. The film exhibits good adhesion to the Petri dish substrate and doesn’t peel off during the outdoor tests. After 1 h reaction under ambient air with simultaneous heating and irradiation by the real sunlight, the H2O2 generation amount still reaches above 1 mM, and the corresponding SCC efficiency is ca. 0.12% for this large area film (Figure 5c). The obtained activity remains relatively high among reported supported systems (Supplementary Table 9). The accumulation amount reaches ca. 4 mM, and the SCC efficiency remains essentially unchanged during an additional 3 h of operation, with the solution temperature stabilizing at ca. 333.15 K. The SCC efficiency also surpasses the average solar-to-biomass conversion efficiency of natural photosynthesis in plants (0.1-1.0%), highlighting the potential of PDA/SA-TCPP for practical solar-driven H2O2 production.43, 44

Given the excellent photocatalytic H2O2 production activity of PDA/SA-TCPP, an integrated system for in-situ H2O2 generation and pollutant degradation is designed, as illustrated in Fig. 5d. Representative pollutants, including methylene blue (MB) and ciprofloxacin (CIP), are employed to evaluate the removal efficiency of the system. In the device, the concentration of in-situ produced H2O2 reaches a stable level of 2.1 ± 0.2 mM during the reaction at a flow speed of 2 mL/min. Within 12 min, nearly 95% of both pollutants are removed, corresponding to a degradation rate of 0.23 min-1 and 0.21 min-1, respectively. (Supplementary Fig. 60) These results demonstrate the effectiveness of the H2O2-producing system for pollutant removal and water purification.

Methods
Materials

Ammonia solution (NH3·H2O, 28-30.0%, Sinopharm Chemical Reagent Co., Ltd.); ethanol, anhydrous (EtOH, ≥99.7%, Sinopharm Chemical Reagent Co., Ltd.); hydrochloric acid (HCl, 36-38.0%, Sinopharm Chemical Reagent Co., Ltd.); sodium hydroxide (NaOH, ≥96.0%, Sinopharm Chemical Reagent Co., Ltd.); isopropanol (IPA, ≥99.7%, Sinopharm Chemical Reagent Co., Ltd.); sodium sulfate (Na2SO4, 99%, Sinopharm Chemical Reagent Co., Ltd.); 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO, 98%, Innochem); nitroblue tetrazolium (NBT, 98%, Innochem); formic acid (HCOOH, 88%, Sinopharm Chemical Reagent Co., Ltd.). All commercial chemicals were used without further purification. Ultrapure water (18.20 MΩ) was used in all experiments.

Preparation of Polydopamine (PDA)

PDA is prepared by a self-polymerization method from dopamine hydrochloride (98%, Beijing InnoChem Science & Technology Corp., Ltd., China).46 In a typical process, 2.0 mL ammonia aqueous solution (NH3·H2O, 28-30%) is added to a 130 mL ethanol solution (30 vol%). The solution is stirred at room temperature for 30 min, and then, 10.0 mL dopamine hydrochloride solution (50.0 mg/mL) is added to the solution. The mixture solution becomes pale brown at first. During stirring, the mixture solution converts into dark brown and then gradually turns into black, indicating the formation of PDA particles. After 48 h of reaction, the PDA is collected by centrifugation (5440 × g) and washed with water three times. The collected solids are dried in a vacuum box at 333.15 K for 12h to obtain the final product.

Preparation of SA-TCPP supermolecule photocatalysts9

Typically, 500.0 mg of meso-Tetra(4-carboxyphenyl) porphyrin (TCPP, 97%, Beijing InnoChem Science & Technology Co, Ltd, China) is fully dissolved with 10.0 mL of 0.5 M KOH aqueous solution. 0.1 M HCl is gradually introduced using a constant-pressure funnel until the pH of the solution reaches 4.0. Subsequently, the suspension is stirred for 72 h to obtain the self-assembled TCPP (SA-TCPP). The resulting precipitate is isolated by centrifugation (5440 × g) and repeatedly washed with ultrapure water until pH ≈ 7.0. The collected SA-TCPP is finally dried under vacuum at 313.15 K prior to further use. Note that to be consistent with the preparation of PDA/SA-TCPP composites, the preparation of SA-TCPP photocatalysts is carried out at room temperature, rather than at 353.15 K in an oil bath as previously reported by us. Though the preparation temperature change leads to different crystallization of SA-TCPP, the H2O2 generation activity of SA-TCPP is similar, probably due to the same short-range ordering (J-aggregation) as verified by the PL spectra (Supplementary Fig. 61).

Preparation of PDA/SA-TCPP composites

Typically, PDA/SA-TCPP composites are prepared by a self-assembly precipitation method at room temperature. The prepared 220.0 mg of PDA and 200.0 mg of TCPP are added into 10.0 mL of 0.5 M NaOH solution, with then 100.0 mL of water is added to the mixture, and the mixture is stirred 2 h to form a transparent dark purple solution.

0.1 M HCl aqueous solution is dropped into the solution by a constant pressure dropping funnel until the pH of the solution decreases to 4.0. Then the black precipitants are formed in the solution, and the final products (PDA/SA-TCPP composites) are centrifuged (5440 × g) and washed with water three times until the pH is 7.0. The obtained PDA/SA-TCPP is dried in a vacuum box at 353.15 K overnight. It is worth noting that the term "PDA/SA-TCPP" mentioned in the article specifically refers to the photocatalyst with an optimal loading amount ratio (mPDA : mSA-TCPP = 1.1: 1). In addition to the optimal PDA loading amount, other mass ratios between PDA and SA-TCPP photocatalysts are prepared, and including the mass ratios of PDA: TCPP are 0.5, 1, 1.2, and 1.5 (Supplementary Fig. 62-64). The sample is denoted as x-PDA/SA-TCPP. Note that the PDA/SA-TCPP are prepared from commercially available chemicals, easily manipulated methods, and common laboratory equipment, indicating good potential for scale-up preparation.

Characterization

The lattice structure is recorded by powder X-ray diffraction (XRD) on a D8 diffractometer equipped with Cu Kα radiation (Bruker AXS, Germany). The sample morphology is characterized using a transmission electron microscope (TEM JEM-2100, JEOL, Japan) operating at an acceleration voltage of 200 kV, and a field-emission scanning electron microscope (FESEM S-4800, Hitachi, Japan). Optical absorption properties in the ultraviolet-visible-near-infrared region are analyzed with a UV-3600 spectrophotometer (Shimadzu, Japan). The bonding information is analyzed by Fourier transform infrared (FTIR) spectroscopy with a Nicolet iS5 instrument (Thermo, USA) employing the KBr pellet method. The band structure is investigated by ultraviolet photoelectron spectroscopy (UPS) using an ESCALAB Xi+ system (Thermo, USA). The related radicals are characterized by electron paramagnetic resonance (EPR) at X-band frequency (9.8 GHz) on a Bruker EMXplus-6/1 spectrometer (Germany).

Photocatalytic H2O2 production tests.

The photocatalytic performance of PDA/SA-TCPP for H2O2 production is evaluated under continuous O2 bubbling (100 mL min-1). The light irradiation is achieved by using a 300 W Xe lamp equipped with a 420 nm cut-off filter (Beijing Perfectlight Technology Co., Ltd, China). In a typical experiment, 0.2000 g photocatalyst is ultrasonically dispersed in 50 mL of water (pH ≈ 4, adjusted by adding 2-3 drops of 0.1 M HCl) in a 100 mL glass bottle. A rubber stopper is capped onto the glass bottle. The rubber stopper is pinned with a PTFE pipe and a needle, which serve as the gas inlet and outlet, respectively.47 The H2O2 activity is evaluated at 353.15 K unless otherwise specified, the temperature shown to cause negligible decomposition of the generated H2O2 (Supplementary Fig. 65-67). Note that despite the decrease in O2 solubility at 353.15 K, the elevated temperature simultaneously enhances the diffusivity of the dissolved O2 and the volume-mass transfer rate of O2 is estimated as ca. 33.8-91.3 mM/h, far exceeding the O2 consumption (1.6 mM/h) based on the H2O2 production rate of PDA/SA-TCPP. (Supplementary Note 1)

Hydrogen peroxide concentrations were determined using the well-established potassium titanium(IV) oxalate spectrophotometric method48,49. In acidic medium, H2O2 reacts with Ti(IV) oxalate to form a yellow Ti-peroxo complex, which exhibits a characteristic absorption at 400 nm. After the desired reaction time, 1.0 mL of solution was filtered through a 0.45 μm syringe filter and mixed with 1.0 mL of 0.02 M Ti(IV) oxalate solution and 3.0 mL of water. The resulting yellow complex was quantified by measuring the absorbance at 400 nm using a UV-3600 spectrophotometer (Shimadzu, Japan). The calibration curve is linear over 0.5-2.0 × 10-3 M (absorbance 0.5-2.0, 1 cm cells), with a precision of ~1% (relative mean deviation 1.1%)50. Although this method can be affected by fluoride ions or colored species, in our system, this interference was eliminated by using ultrapure water (18.20 MΩ). The method shows comparable accuracy to the conventional iodometric method (Supplementary Fig. 65).

Measurements for apparent quantum yield (ΦAQY) and solar-to-chemical conversion efficiency (ηSCC)

The photocatalytic reaction is carried out with a 200.0 mg photocatalyst in a glass bottle containing 50.0 mL of water by a 300 W Xe lamp equipped with a quartz optical fiber as the light source. The bottle is kept at 353.15 K in an oil bath. During the reaction, Xe lamp is set over the reaction solution with a constant distance of 4.0 cm, O2 is bubbled into the bottle. The reaction is performed for 0.5 h with magnetic stirring. The monochromatic light for AQY measurements is obtained using a series of band-pass filters (400 ± 10, 420 ± 10, 490 ± 10, 550 ± 10, 600 ± 10, 650 ± 10, 700 ± 10, 850 ± 10, 940 ± 10, and 1020 ± 10 nm). The photon number entered into the reaction bottle is determined with a UV spectral illuminance meter (OHSP-350 UV, Hangzhou, China).9 The apparent quantum yields for H2O2 generation are determined using the equation:

ΦAQY(%)= (H2O2 formed(mol)×NA×h×C) / (I × A × λ × t) ×100 (1)

where N is the Avogadro constant (6.02 × 1023 mol-1); h is the Planck constant (6.626 × 10-34 J·s); C is the light speed (3.0 × 108 m/s); I is the light intensity (W/m2); A is the irradiation area (0.25π × 10−4 m2); λ is the wavelength of incident light (m), and t is the reaction time (1800 s).

The SCC efficiency for the H2O2 production is determined under AM 1.5G simulated sunlight irradiation (Xe lump with AM 1.5G cut-off filter, Perfect Light, Beijing, China).9 The light intensity is measured by a PL-MW 2000 photoradiometer (Perfect Light, Beijing, China). The ηSCC is determined using the following equation:

ηscc(%) = (ΔG×H2O2formed (mol)) / (t×S×IAM) ×100 (2)

where ΔG is the free energy for H2O2 production (117 kJ/mol); t is the irradiation time, S is the irradiation area (0.25π × 10−4 m2), and IAM is the light intensity (1000 W/m2)

Calculation for the photothermal conversion efficiency

The photothermal conversion efficiencies of the SA-TCPP and PDA/SA-TCPP are determined according to the literature.51 Detailed calculations are given below:

η = (hS×(Tmax-Tsurr) - Qdis) / (I×(1-10−A940)) (3)

hS = - (mD×CD×ln ( (Tm-Tsurr) / (Tmax-Tsurr) )) / t (4)

Where h is the heat transfer coefficient, S is the surface area of the container, and the value of hS is obtained from Eq.(3). Tmax is the maximum steady temperature of the solution (311.45 K for SA-TCPP and 317.15 K for PDA/SA-TCPP), Tsurr is the environmental temperature (288.35 K), I is light power (0.49 W), A940 is the absorbance of the photocatalyst at 940 nm (For SA-TCPP and PDA/SA-TCPP, the absorbance values are 0.17 and 0.60 respectively), QDis is the heat dissipated from the light absorbed by the solvent and container (0.21 W), mD is the mass of the solvent (0.1 g), CD is the specific heat capacity of the solvent (4.2 J/g·K), and t is the irradiation time (900 s).

Electrochemical and PEC measurements

All electrochemical and PEC measurements (photocurrent, Mott-Schottky, and electrochemical impedance) are performed in 0.5 M sodium sulfate solution (pH=6.8 ± 0.2) through the traditional three-electrode system using the CHI 660E electrochemical workstation (Shanghai Chenhua Technology Co., LTD). PDA/SA-TCPP/fluorine-doped tin oxide (FTO) glass (1.5 × 1.0 cm2) is used as a working electrode; a platinum net is employed as a counter electrode (1.5 × 1.5 cm2, Shanghai Chenhua Technology Co., LTD), and a standard Ag/AgCl electrode (EAg/AgCl = 0.210 V vs. RHE, Shanghai Chenhua Technology Co., LTD) is used as a reference electrode. A 300 W Xe lamp is used as the light source. The resistance of the electrochemical cell was measured using the built-in iR test of the electrochemical workstation prior to electrochemical measurements. The obtained cell resistance was 22.7 ± 0.2 Ω, averaged from three independent measurements.

The PDA/SA-TCPP/FTO is used as the working electrode. The electrode is obtained by finely grinding the PDA/SA-TCPP photocatalyst (10 mg) and then ultrasonicating it in 1.0 mL of ethanol for 1 h to form a uniform suspension. Next, 20.0 µl of the well-dispersed suspension is uniformly cast onto an FTO glass by dropping. The PDA/SA-TCPP/FTO is then dried at room temperature for 2 h before use.

Mott-Schottky plots are measured at alternating current (AC) frequencies of 2000 Hz. The electron density of the defect levels is calculated as follows:

1/C2 = (2 / (A2qεNA)) (VDC-Vbi) (5)

where A is the junction area (1.0 cm2), q is the elementary charge (1.6×10-19 C), and ε= ε0 εr is the semiconductor permittivity (ε0 the permittivity of vacuum (8.8 × 10-10 F/cm), εr the relative dielectric constant of the semiconductor (1.13), NA is the electron density at defect level, Vbi is the built-in potential and VDC is the applied DC bias. The plot of 1/C2 vs VDC (Mott-Schottky plot) yields a straight line in the range of small forward DC bias (-0.1 V-0.2 V), NA and Vbi is extracted by fitting the straight line with Eq. (5).

The rotating disk electrode test

The rotating disk electrode (RDE) test is performed on a CHI-750E electrochemical workstation, operated via computer control and a conventional three-electrode setup. The glassy carbon disk coated with the sample serves as the working electrode, while an Ag/AgCl electrode and a platinum mesh electrode are employed as the reference and counter electrodes, respectively.9 The electrolyte consists of 100 mL of 0.5 M Na2SO4 solution containing 80 mg of dopamine hydrochloride (DA·HCl), which is the monomer precursor of polydopamine. Linear sweep voltammetry scans are conducted at a scan rate of 10 mV s⁻¹ under argon saturation across various rotation speeds. After each scan, argon was bubbled for 30 minutes to remove residual oxygen (O2). The average electron transfer number (n) involved in the redox process from SQ• to Q is determined from the slopes of the Koutecky−Levich plots, using the following equations:

j-1 = jk-1 + B-1 ω-1/2 (6)

B = 0.2nFν-1/6CD2/3 (7)

where j is the measured current, jk is the kinetic current density, B is the proportionality coefficient, and ω is the electrode rotating speed (rpm), respectively. F is the Faraday constant (96485 C mol−1), ν is the kinetic viscosity of water (0.01 cm2·s−1), C is the concentration of DAꞏHCl in solution (6.52 × 10−6 mol/cm3 ), and D is the diffusion coefficient (6.5 × 10−6 cm2/ s ) of DAꞏHCl 52.

The calculations of volume-mass transfer rate of O2

The diffusion coefficients of O2 in water at 298.15 K and 353.15 K are calculated according to the Wilke-Chang correlation.53

DAB = (7.4×10−8(φMB)1/2T) / (ηV0.6) (8)

where D is the diffusion coefficient (cm2/s), φ is the solvent association factor (2.26 for water), M is the molecular weight of the solvent (18.0 g/mol), T is the absolute temperature (K), η is the dynamic viscosity (298.15 K: η = 0.890 cP, 353.15 K: η = 0.355 cP), and V is the molar volume of O2 at its boiling point (25.6 cm³/mol)54.

The volume-mass transfer rate of O2 at 353.15 K is calculated according to the diffusion coefficients. In our experimental setup, O2 is continuously bubbled throughout the photocatalytic process. In such a condition, the instantaneous dissolved O2 concentration is not solely governed by temperature-dependent solubility. Instead, the supply of O2 to our photocatalyst is determined by the volume-mass transfer rate of O2, which in the liquid phase can be expressed by the classical gas-liquid mass transfer model as55:

RO2 = (kLa(C∗−C)) / MO2 = (ShDO2× a(C∗−C)) / (L MO2) (9)

where R represents the molar supply rate of O2 per unit volume (mM/h), Ka is the volume-mass transfer coefficient, D is the liquid-phase diffusion coefficients of O2 (6.72×10-5 cm2/s at 353.15 K), Sh is the Sherwood number (10)56, L is a characteristic length (distance from the outlet of the gas-bubbling pipe to the surface of suspended photocatalysts, set in this work as the average of the liquid depth, 2 cm), C∗ is the solubility of O2 in water (4.0 mg/L at 1 atm and 353.15 K), a is gas-liquid interface area ratio (300 - 800 cm-1)57, C is the instantaneous dissolved O2 concentration in water (2.0 mg/L, which is the residual O2 concentration after per minute H2O2 production), and M is the molar mass of oxygen (32 g/mol).

Determination of light intensity

Photocatalytic reactions were carried out using a 300 W xenon lamp equipped with a 420 nm cut-off filter. The average light intensity incident on the reaction area was determined to be 200 mW cm-2. Considering the cross-sectional area of our reactor, the intensity was measured at five representative positions within a circular area of 3 cm radius, including the center (spot A) and four positions at the edge (spots B-E) (Supplementary Fig. 68).

The average light intensity I was calculated using the following weighted equation:

I = (πr12×IA) / πr32 + (π(r22-r12)×(IB+ID)) / (2πr32) + (π(r32-r22)×(IC+IE)) / (2πr32)

The measured light intensities were as follows: spot A, 900 mW cm-2; spot B, 220 mW cm-2; spot C, 57 mW cm-2; spot D, 200 mW cm-2; and spot E, 51 mW cm-2. r1, r2, and r3 correspond to distances of 1 cm, 2 cm, and 3 cm, respectively.

DFT calculation

The DFT calculations are performed on Material Studio with the Dmol3 package.58 The geometry optimization is performed first to relax the reactants and products, respectively, and then, the transition state calculations are carried out to obtain the energy barriers for SQ• with O2 to produce H2O2. For the transition state calculations, the linear synchronous transit/quadratic synchronous transit (LST/QST) method is used. The exchange and correlation functions are treated by the Becke three-parameter Lee−Yang−Parr (B3LYP) level of theory, taking into account the bulk solvent effects of water. The tolerances for geometry optimization and TS calculations are set with the total energy of 5×10-5 Ha/atom, the maximum force of 0.002 Ha/Å, the maximum ionic displacement of 5×10-3 Å, and the maximum root-mean-square (RMS) forces of 0.01 Ha/Å. To calculate the LUMO orbitals of PDA, a structural model consisting of nine moieties containing Q, SQ•, and QH2 units with varying saturation degrees of the indole is constructed. The exchange and correlation functions are also treated by the B3LYP. Geometry optimization is performed with convergence criteria of 1×10⁻⁴ Ha/atom for total energy, 0.02 Ha/Å for maximum force, and 0.05 Å for maximum ionic displacement. Note that, considering the inherent challenges in accurately modelling the exact material under realistic catalytic conditions, the DFT calculations in this work are intended primarily to provide supportive insight for the experimental results.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this work, the authors constructed a composite photocatalyst PDA/SA-TCPP by loading polydopamine (PDA) onto self-assembled TCPP supramolecular structures (SA-TCPP), aiming to enhance the NIR-driven H2O2 photosynthesis efficiency. The manuscript claims that persistent semiquinone radicals (SQ•) in PDA mediate ultrafast sub-bandgap electron transfer (~79 fs) within SA-TCPP, thereby promoting •OOH intermediate formation and ultimately improving H2O2 yield. The experimental data are systematically presented, including material characterization, photocatalytic performance evaluation, transient spectroscopy, and mechanistic discussion. However, the manuscript exhibits notable deficiencies in innovation demonstration, rigor of data interpretation, and directness of mechanistic evidence, with some conclusions appearing overly speculative and lacking sufficient experimental/theoretical support. While showing potential, this work requires major revisions to strengthen logical coherence and data reliability. If the following issues cannot be addressed, acceptance is not recommended.\n1. The manuscript emphasizes \"persistent SQ•-mediated sub-bandgap electron transfer\" as the core innovation, but similar strategies (e.g., radical-mediated H2O2 photosynthesis in organic semiconductors) have been reported (Angew. Chem. Int. Ed. 2025, e202516657. https://doi.org/10.1002/anie.202516657). The authors fail to sufficiently clarify the essential differences between their system and existing ones, particularly neglecting to highlight the unique advantages of combining PDA with porphyrin supramolecules.\n2. Related reports indicate that PDA can rapidly generate •O₂- and convert it into •OOH (Angew. Chem. Int. Ed. 2024, 63, e202319216.). However, this paper focuses on discussing the •OOH radical while neglecting the presence of •O₂-. Therefore, additional quenching experiments need further consideration. Although the conduction band of SA-TCPP is insufficient to generate •O₂-, PDA is capable of doing this.\n3. The discussion focuses exclusively on oxygen reduction reactions while inadequately addressing oxidation reactions.\n4. Although the authors attribute •OOH intermediate formation to persistent SQ•, they neither investigate the persistence of SQ• nor provide direct evidence for SQ• involvement in H2O2 photosynthesis.\n5. Supplementary Figure 19 appears to depict superoxide radicals rather than •OOH, which directly contradicts the authors' emphasis in the manuscript on •OOH as a key intermediate.\n6. The apparent quantum efficiency (AQY) of SA-TCPP should be supplemented. Additionally, comparative analysis with recent high-level works regarding AQY under NIR irradiation is necessary.\n7. Related reports indicate that under dark conditions, the catechol molecules in PDA can be oxidized by •O₂- to form catecholquinone, thereby synthesizing H₂O₂ (Applied Catalysis B: Environment and Energy, 364 (2025) 124863). This non-photocatalytically induced hydrogen peroxide production requires separate discussion from photocatalytic processes.\n8. The increase in temperature will affect the solubility of O₂, which will also have an impact on the formation of H₂O₂. This aspect needs to be discussed.\n9. Performance tests conducted at 353.15 K claim negligible H2O2 decomposition (Supplementary Figure. 38). However, elevated temperature itself might promote non-photocatalytic pathways. Dark reaction controls or low-temperature activity comparisons should be provided to exclude thermal effects. Furthermore, justification is required for why H2O2 decomposition is negligible in this system despite its general susceptibility during photocatalysis.\n10. While the manuscript mentions enhanced photothermal conversion efficiency by PDA (Supplementary Figure. 32-33), it fails to distinguish specific contributions of photothermal effects to reaction rates (e.g., local heating-enhanced O2 diffusion vs. thermal catalytic reactions). Isothermal control experiments are recommended to quantify photothermal effects.\n11. Data on pure PDA should be supplemented and compared with SA-TCPP and PDA/SA-TCPP.\n12. Adding XPS testing further confirms the successful synthesis of PDA.\n13. The loading optimization of PDA/SA-TCPP composites was evaluated solely based on H₂O₂ yield, without considering factors such as light absorption and charge separation efficiency.\n14. The paper mentions that SA-TCPP crystallinity varies with temperature, yet its H₂O₂ production performance remains similar. Further explanation of this phenomenon is required.\n15. Although H₂O₂ yield and SCC efficiency outperform comparable studies, the reaction temperature used is difficult to sustain in practical solar applications. Evaluating performance at room temperature or clarifying the feasibility of elevated temperatures for real-world use is recommended. Additionally, the outdoor SCC efficiency of only 0.12% differs significantly from laboratory conditions, necessitating discussion of practical limitations (e.g., light intensity, temperature, catalyst stability).\n16. Further applications of H2O2 should be discussed.\n17. Comparative experiments are lacking where PDA is loaded onto other infrared catalyst supports to demonstrate the universality or specificity of this strategy.\n18. Does the hydrogen bonding interaction between PDA and SA-TCPP make a substantial contribution to electron transfer?\n19. The figure resolution is insufficient. Higher-quality images should be provided.\n20. Issues exist in reference formatting consistency and outdated citations. The authors should thoroughly check and update relevant literature.", "reviewer_2": "The manuscript reports a PDA/SA-TCPP photocatalyst that achieves efficient H2O2 production under NIR irradiation, with a rate of 0.99 mM h⁻¹ and an AQY of 2.8% at 1020 nm. Photocatalytic H2O2 production is a hot topic and a promising sustainable method for solar-to-chemical energy conversion, yet current progress is limited by low NIR utilization. This work is therefore timely and significant. The loading of PDA with persistent semiquinone radicals is demonstrated to enable ultrafast (∼79 fs) sub-gap electron transfer from porphyrin trap states to PDA, overcoming the high recombination rates of NIR-excited electrons. Moreover, SQ• radicals are reported to promote the formation of •OOH radicals, a rate-limitation intermediate for H2O2 production, extending the NIR response to 1020 nm. These findings provide a new strategy for efficient solar-to-chemical energy conversion and will interest researchers in the field. Overall, the manuscript is well written and of high impact. I recommend acceptance in Nature Communications after minor revisions to address the following comments.\n1. PDA itself has been used in photocatalytic H2O2 production. Please provide more discussion of these results in the introduction to better clarify the novelty of this work. Moreover, to clearly delineate the individual roles of SA-TCPP and PDA within the PDA/SA-TCPP composite for H2O2 generation, supplementary characterization of PDA’s semiconductor properties—including its light absorption characteristics, energy band structure, and corresponding intrinsic photocatalytic H2O2 production performance—should be provided.\n2. The authors attribute the superior NIR performance to persistent SQ• radicals. Will these radicals be consumed during reaction? In fact, SQ• radicals appear to act as intermediates between QH2 and Q, and previous studies (10.1021/acscatal.2c03288) have reported that the cycling between QH2 and Q moieties facilitates the acceleration of O2 reduction to H2O2. This raises the question of how to definitively distinguish whether the mechanism involves cycling between QH2 and Q or between SQ• and Q. Additionally, since PDA can be oxidized by O2 to produce H2O2 even in the absence of light, it is crucial to elucidate the precise mechanism underlying the performance enhancement attributed to PDA.\n3. To better differentiate between purely photocatalytic and thermal effects, the authors should evaluate the activity of PDA, SA-TCPP, and PDA/SA-TCPP under two additional conditions: either under light irradiation at 298 K or in darkness at 353 K, given that the photocatalytic tests were originally performed at 353 K.\n4. The reported AQY values under NIR are impressive, but only calculated AQY data are provided in the SI. Please include the corresponding activity data and specify the light intensity used for each AQY measurements.\n5. Given the promise of PDA with persistent SQ• radicals on the utilization of trap electrons, have the authors tested such materials in other photocatalytic systems to verify the general applicability of this strategy?", "reviewer_3": "This study presents a composite photocatalyst comprising polydopamine (PDA) nanoparticles supported on self-assembled TCPP supramolecular nanosheets (SA-TCPP) for near-infrared (NIR)-driven H2O2 photosynthesis from H2O and O2. The authors attribute the enhanced activity to the role of persistent semiquinone radicals (SQ•) in PDA, which mediate ultrafast sub-gap electron transfer (~79 fs) from SA-TCPP to PDA, thereby promoting the formation of •OOH intermediates. While the experimental data are comprehensive and generally support the conclusions, the work lacks mechanistic depth in several critical areas, and the catalyst design itself does not represent a significant conceptual advance. As such, the reviewer does not recommend publication in Nature Communications:\n1. Stability and Dynamics of SQ• Radicals: Although the cyclic experiments have shown good stability, the chemical persistence and regeneration efficiency of the SQ• radicals under prolonged illumination remain unquantified. To firmly establish the role of SQ• as a durable electron mediator, quantitative EPR analysis of the radical concentration before and after extended reaction cycles is essential.\n2. Interface Characterization: The evidence for hydrogen bonding between PDA and SA-TCPP, based solely on FTIR peak shifts, is indirect. More direct characterization techniques, such as solid-state NMR or high-resolution XPS, are needed to conclusively identify and quantify the nature and strength of these interfacial interactions.\n3. Reaction Mechanism Completeness: The study clearly demonstrates NIR-induced •OOH formation on PDA. However, the subsequent critical step—how the •OOH intermediate is reduced to H₂O₂ via synergy with SA-TCPP—is not elucidated. Identifying whether this step is limited by electron transfer, intermediate desorption, or another factor is crucial for rational optimization.\n4. Ultrafast Electron Transfer Pathway: While fs-TAS data indicate an interfacial electron transfer process, the specific pathway and electronic coupling mechanism for sub-gap electron injection from SA-TCPP trap states to PDA's SQ•/quinone moieties remain unclear. A more detailed theoretical analysis (e.g., electronic structure calculations of the interface) would strengthen this central claim.\n5. Energy Level Diagram Clarification: For a more intuitive comparison, the energy level diagram in Figure 4d should include the calculated absolute energy values (in eV) of the relevant PDA orbitals (e.g., LUMO, LUMO) alongside the trap state levels of SA-TCPP.\n6. Benchmarking Context: In Supplementary Table S2, the photocatalytic performance of reference materials should be compared under standardized conditions. Annotations specifying the light source characteristics (wavelength range, intensity) for each benchmarked catalyst would ensure a fair and accurate comparison.\n7. Mechanistic Discrimination: To robustly distinguish an electron transfer mechanism from potential energy transfer processes, time-resolved photoluminescence (TRPL) spectroscopy comparing the excited-state lifetimes of SA-TCPP and PDA/SA-TCPP would provide complementary evidence.\n8. Photothermal Contribution: The significant photothermal effect of PDA is noted, but its quantitative contribution to the overall H₂O₂ production rate, distinct from the photochemical electron transfer pathway, is not delineated. Controlled experiments under isothermal conditions are needed to deconvolute these effects.\n9. Scalability and Practical Viability: The pathway toward practical application is not addressed. Questions regarding the scalability of catalyst synthesis, the feasibility of fabricating stable catalytic films or membranes, and the design of flow reactors for continuous H₂O₂ production—along with a preliminary techno-economic assessment—should be discussed to evaluate real-world potential.", "reviewer_4": "See attached file"}, "author_response": "Response to Reviewers\nManuscript Title: Near-IR H O Photosynthesis through Rapid Sub-Gap Electron Transfer Mediated by\n2 2\nPersistent Semiquinone Radicals\nManuscript Number: NCOMMS-25-71751\nAuthor: Shuai Dou+, Yaning Zhang+, Jing Xu, Ying Zhang, Yang Lou, Jiawei Zhang, Yuming Dong, Yongfa\nZhu, and Chengsi Pan*\n[The reviewer comments are shown in italic]\n[Responses with the emphasized parts are in BLUE]\n[Revisions in the manuscript and supplementary information are highlighted in PURPLE]\nReviewer #1\nIn this work, the authors constructed a composite photocatalyst PDA/SA-TCPP by loading polydopamine\n(PDA) onto self-assembled TCPP supramolecular structures (SA-TCPP), aiming to enhance the NIR-driven\nH O photosynthesis efficiency. The manuscript claims that persistent semiquinone radicals (SQ•) in PDA\n2 2\nmediate ultrafast sub-bandgap electron transfer (~79 fs) within SA-TCPP, thereby promoting •OOH\nintermediate formation and ultimately improving H O yield. The experimental data are systematically\n2 2\npresented, including material characterization, photocatalytic performance evaluation, transient\nspectroscopy, and mechanistic discussion. However, the manuscript exhibits notable deficiencies in\ninnovation demonstration, rigor of data interpretation, and directness of mechanistic evidence, with\nsome conclusions appearing overly speculative and lacking sufficient experimental/theoretical support.\nWhile showing potential, this work requires major revisions to strengthen logical coherence and data\nreliability. If the following issues cannot be addressed, acceptance is not recommended.\n1. The manuscript emphasizes \"persistent SQ•-mediated sub-bandgap electron transfer\" as the core\ninnovation, but similar strategies (e.g., radical-mediated H O photosynthesis in organic\n2 2\nsemiconductors) have been reported (Angew. Chem. Int. Ed. 2025, e202516657.\nhttps://doi.org/10.1002/anie.202516657). The authors fail to sufficiently clarify the essential\ndifferences between their system and existing ones, particularly neglecting to highlight the unique\nadvantages of combining PDA with porphyrin supramolecules.\nAnswer: Thanks for your comments. We agree that radical-mediated H O photosynthesis in organic\n2 2\nsemiconductor systems, where radicals are generated within the photocatalyst framework, has been\npreviously reported, including the work cited by the reviewer (Zhao. Y, et al., Angew. Chem. Int. Ed. 2025,\n1\n64, e202516657). However, the NIR utilization mechanism and interfacial charge dynamics enabled by\npersistent SQ• radicals in our PDA/SA-TCPP system are fundamentally distinct from existing radical-\nmediated strategies.\nFirst, in most reported radical-mediated systems, the formation of reactive radicals (e.g., H• or C-\ncentered radicals) requires UV or visible excitation to overcome large energy barriers for single-\nelectron generation. (M. Long, et al., Nat. Commun. 2024, 15, 2649) Consequently, these strategies are\ngenerally ineffective under NIR irradiation, including the work cited by the reviewer.\nSecond, in previously reported NIR-driven ORR systems, even when O ⁻• or HOO• intermediates\n2\nare generated, they tend to undergo rapid back reactions to regenerate O rather than being reduced\n2\nto H O . (X. Zhang, et al., Angew. Chem. Int. Ed. 2020, 59, 17356) This behavior originates from fast\n2 2\nrecombination of low-energy NIR-excited charge carriers, which inhibits efficient two-electron transfer\nand makes sustained H O accumulation under NIR light highly challenging.\n2 2\nIn contrast, this bottleneck is overcome through interfacial coupling between porphyrin\nsupramolecules and a persistent radical reservoir (PDA). The semiquinone radicals (SQ•) in PDA arise\nfrom a reversible redox equilibrium of Q and QH with a low activation energy (<0.5 eV) (G. Buettner\n2\net al., Free. Radical. Biol. Med. 2010, 49, 919), making them intrinsically compatible with sub-bandgap\nNIR excitation. Importantly, SQ• species act as highly efficient electron acceptors, extracting NIR-\nexcited electrons from SA-TCPP and suppressing charge recombination. Transient absorption\nspectroscopy reveals that this interfacial charge separation occurs within 79 fs, one to two orders of\nmagnitude faster than the picosecond-scale charge transfer reported in the referenced work. This\nultrafast electron extraction enables sustained reduction of NIR-generated O -•/HOO• intermediates to\n2 2\nof this work does not lie merely in radical-assisted ORR, but in integrating persistent SQ• radicals with\nNIR-responsive porphyrin supramolecules to enable efficient sub-bandgap electron utilization.\nTo address this novelty, we have added the following discussions in the Introduction part in the\nrevised manuscript (Page 2, line 7-13): “Although the promotion of ORR to H O mediated by radicals\n2 2\ngenerated within the photocatalyst structure has been reported12, the generation of such reactive\n2\nradicals typically requires UV or visible excitation. Moreover, under NIR irradiation, even when O -• or\ntoward back reactions originating from rapid electron-hole recombination.”\n2. Related reports indicate that PDA can rapidly generate •O - and convert it into •OOH (Angew. Chem.\nneglecting the presence of •O -. Therefore, additional quenching experiments need further\n2\nconsideration. Although the conduction band of SA-TCPP is insufficient to generate •O -, PDA is capable\n2\nof doing this.\nAnswer: Thanks for your suggestions. We agree with the reviewer that •O - may exist and contribute to\n2\nthe H O generation. As suggested, quenching experiments with Nitrotetrazolium blue chloride (NBT).\n2 2\nNBT has been performed, which selectively reacts with •O - rather than •OOH (H. Zheng, et al., J. Am.\n2 2\nTCPP decreases only slightly from 3.39 to 3.24 mM/h upon addition of 0.05 mM NBT, indicating that\n•O - quenching has a negligible impact on H O generation.\n2 2 2\nThe NBT reagent is also employed to quantitatively evaluate the generation of •O₂⁻ during the\nreaction. (Q. Fang, et al., J. Am. Chem. Soc. 2025, 147, 13667; B. Tang, et al., Angew. Chem. Int. Ed. 2023,\n62, e202309624) The quantitative mechanism is illustrated in Supplementary Fig. Xb. The decrease of\nthe adsorption peak at 259 nm can quantitatively reflect the concentration of •O - generation during the\n2 2\ndecreased, corresponding to the generated amount of •O - far below the common level.(Q. Fang. et\n2\nal, J. Am. Chem. Soc. 2025, 147, 13667; B Tang. et al., Angew. Chem. Int. Ed. 2023, 62, e202309624) The\nquantitative experiment indicates negligible •O - is generated during the H O production.\n2 2 2\nWe think the key factor leading to •OOH rather than •O ⁻ being the dominant reaction intermediate\n2\nin PDA-containing H O production systems, different from the system reported in the reviewer\n2 2\nmentioned literature (L. Ye, et al., Angew. Chem. Int. Ed. 2024, 63, e202319216), is the reaction pH.\nIn the work, the reaction is conducted in pure water at pH = 7. In contrast, in our system, the pH\nis adjusted to approximately 4 by adding HCl, which is necessary to suppress the dissolution of TCPP,\nas demonstrated in our previous study (C. Pan et al., Nat. Energy 2023, 8, 361). According to literature\n3\n(M. Hayyan, et al., Chem. Rev. 2016, 116, 5, 3029), the pKa of •OOH is 4.88 (•OOH→H++•O -, pKa = -lg\n2\n([H+]*[•O -]/[•OOH])). Therefore, if pH = 7, the concentration ratio of [•O -]/[•OOH] will be ca. 100\n2 2\n(102.12), indicating that •O - is the predominant intermediate under neutral conditions. In contrast, at pH\n2\n= 4, the concentration ratio of [•O -]/[•OOH] decreases to ca. 0.1 (10-0.88). indicating that •OOH becomes\n2\nthe thermodynamically favored and more stable intermediate, and its formation is more likely governed\nby electron-proton coupled transfer processes.\nAccording to the above discussion, the following discussion is added in Supplementary Page 58. “In\nprevious PDA-based systems, •O ⁻ is identified as the dominant reactive species responsible for H O\n2 2 2\ngeneration at neutral or alkaline pH.65 In contrast, our reaction is conducted at pH ≈ 4. The acid-base\nequilibrium between •O ⁻ and •OOH shifts markedly: based on a pKₐ value of 4.88 for •OOH66, the\n2\n[•O₂⁻]/[•OOH] ratio decreases from ca. 100 at pH = 7 to ca. 0.1 at pH = 4. As a result, •OOH becomes the\npredominant and thermodynamically more stable intermediate involved in H₂O₂ formation. NBT\nquenching and quantitative experiments (supplementary Fig. 46c-d) demonstrate that the contribution\nof •O - to H O production in the PDA/SA-TCPP system is negligible, further supporting •OOH as the key\n2 2 2\nreaction intermediate under our experimental conditions.”\n2 2 2 2 2\ngeneration on PDA/SA-TCPP with and without •O - radical capture. 0.05 mM NBT is employed as the\n2\nradical capture reagent. (b) Schematic of the •O - trapping mechanism by NBT, (c) UV-Vis absorption\n2\nspectra of the reaction solution with 0.01 mM NBT recorded at different sampling times. (d) The amount\nof •O - generated during the reaction.\n2\n3. The discussion focuses exclusively on oxygen reduction reactions while inadequately addressing\noxidation reactions.\nAnswer: Thanks for your suggestion. In the SA-TCPP alone system (C. Pan, et al., Nat. Energy 2023, 8,\n361), we have demonstrated oxidation reactions in which the carboxyl group on SA-TCPP is initially\noxidized into a peroxy acid intermediate (-COOH + 2h+ + H O → -CO H + 2H+). Subsequently, -CO H\n2 3 3\nundergoes thermal hydrolysis to regenerate the -COOH to form H O (-CO H + H O → -COOH + H O ).\n2 2 3 3 2 2\nIn our present work for PDA/SA-TCPP, TAS results (Figure 4) show electron transfer from SA-TCPP\nto PDA, implying that photogenerated holes remain on SA-TCPP. To probe their role, we have added\ncomparative 13C NMR, 1H NMR, TOF-MS, and FTIR analyses of PDA/SA-TCPP and SA-TCPP after reaction\nin the revised manuscript. SA-TCPP in the composite is selectively dissolved in DMSO to avoid PDA\ninterference, and measurements are conducted at 298.15 K to allow peroxy acid accumulation.\nThe following discussions have been added to the revised manuscript (Page 15, lines 2-6). “The NIR\nphotocatalytic activity enhancement mechanism for PDA/SA-TCPP is studied next. In the PDA/SA-TCPP\nsystem, the peroxy acid intermediate—similar to that in SA-TCPP—is still observed under irradiation by\ncomparative 13C NMR, 1H NMR, TOF-MS, and FTIR analyses of PDA/SA-TCPP and SA-TCPP after room\ntemperature reaction. (Supplementary Fig. 32) The similarity of the spectra excludes hole transfer from\nSA-TCPP to PDA, which indicates that holes remain on SA-TCPP.”\nThe following discussion is added on Supplementary Page 40-41. “Supplementary Fig. 32 compares\nthe formation of the peroxy acid intermediate between PDA/SA-TCPP and SA-TCPP-alone after the\nreaction at 298.15 K. Supplementary Fig. 32a, b present the corresponding 13C and 1H NMR spectra of\nthe SA-TCPP and PDA/SA-TCPP photocatalyst after the reaction. After the reaction, distinct 13C NMR\nresonances attributed to SA-TCPP-COOOH appear at 167.1, 141.3, 129.9, 129.5, and 119.4 ppm, together\n5\nwith characteristic 1H NMR signals at 12.8 ppm, 8.2-7.8 ppm, and 7.0-6.8 ppm, confirming the formation\nof the COOOH groups.\nSupplementary Fig. 32c shows the FTIR spectra of PDA/SA-TCPP and SA-TCPP-alone recorded after\nthe reaction. Two absorption bands at 1633 cm⁻¹ and 1275 cm⁻¹ emerge for PDA/SA-TCPP, belonging to\nthe stretching vibrations of C=O and the bending of O-H in COOOH group, respectively, which is consistent\nwith those observed in the SA-TCPP-only system.\nSupplementary Fig. 32d displays the TOF-MS of PDA/SA-TCPP and SA-TCPP-alone acquired after the\nreaction. After the reaction, peaks at 807, 808, 809, and 810 are observed for both samples. The mass\nincrement of 16 relative to SA-TCPP (m/z peaks at 791, 792, 793, and 794)13 indicates the incorporation\nof 16O atom into the -COOH moiety, confirming the formation of the -COOOH intermediate, in agreement\nwith our previous reports. These results collectively indicate that in the PDA/SA-TCPP system, the holes\nremain on the SA-TCPP to oxidize the carboxyl groups and form the -CO H group, and subsequently, -\n3 2 2\neffect observed in the system using SA-TCPP alone.”\n2 2\non PDA/SA-TCPP photocatalyst and SA-TCPP-alone after reaction at room temperature (298.15 K). To\nexclude 13C NMR, 1H NMR, and TOF-MS interference from PDA, SA-TCPP in the PDA/SA-TCPP composite\nis selectively dissolved using DMSO and subsequently used for further comparison.\n4. Although the authors attribute •OOH intermediate formation to persistent SQ•, they neither (1)\ninvestigate the persistence of SQ• nor (2) provide direct evidence for SQ• involvement in H O\n2 2\nphotosynthesis.\nAnswer: We thank the reviewer for the insightful comment.\n(1) To evaluate the persistence of SQ•, EPR measurements are conducted after the H O production\n2 2\nreaction (Supplementary Fig. 51c). The results show no significant change in the SQ• signal intensity\nafter the reaction, indicating that the persistence of SQ•. This persistence may be attributed to a\ndynamic regeneration process: although the formation of •OOH may transiently consume SQ• by\n7\nconverting it to Q, subsequent electron transfer from SA-TCPP efficiently regenerates SQ•, as illustrated\nin the schematic shown in Supplementary Fig. 52.\nThe following discussions are added in the supplementary information on page 63, “EPR\nmeasurements performed after photocatalytic H O production show that the SQ• signal intensity\n2 2\nremains essentially unchanged, indicating that SQ• is persistent under the reaction conditions. This\napparent stability originates from a dynamic regeneration process, in which transient SQ• consumption\nduring •OOH formation is continuously compensated by electron transfer from photoexcited SA-TCPP\n(Supplementary Fig. 52).”\nSupplementary Figure S51. (c) TEPR spectra of the PDA/SA-TCPP sample before and after 10 cycle\nreaction (stability test in Figure 5b in the main text)\nSupplementary Figure S2. Schematic illustrating the SQ• radical cycle during the H O production.\n2 2\n8\n(2) The involvement of SQ• in NIR-driven H O photosynthesis arises from two key functions: promoting\n2 2\nthe formation of •OOH intermediates and facilitating sub-bandgap electron transfer from SA-TCPP.\nThe following discussions are added on Supplementary Page 60: “To provide direct evidence for the\npromotion of the formation of •OOH intermediates, we have conducted EPR measurements on the\nPDA/SA-TCPP system under anoxic conditions (N bubbling) and in air, together with quantitative H O\n2 2 2\nanalysis. Under N bubbling, EPR spectra reveal a pronounced accumulation of SQ• radicals, which\n2\ncontribute approximately 55% to the overall EPR signal, accompanied by the production of 0.42 mM H O\n2 2\nfor a 4 h reaction (Supplementary Fig. 48a, b). In contrast, when the reaction is performed in air, the EPR\nsignal associated with SQ• decreases dramatically, with its contribution dropping to ca. 21%, while the\namount of generated H O increases by approximately sevenfold (Supplementary Fig. 48c,d). Notably, at\n2 2\nthe same time, the contribution of •OOH to the overall EPR spectra increases substantially. The inverse\ncorrelation between SQ• intensity and H O yield provides strong evidence that SQ• radicals are\n2 2\nactively consumed during NIR-driven H O formation via generating •OOH.”\n2 2\n2 2\non PDA/SA-TCPP under NIR irradiation with N bubbling, (c) and (d) EPR spectra and the corresponding\n2\nphotocatalytic H O production on PDA/SA-TCPP under NIR irradiation with air bubbling.\n2 2\nWe have further investigated the role of SQ• in facilitating sub-bandgap electron transfer from SA-\nTCPP. Previous studies have shown that Fe3+ can strongly coordinate with semiquinone radicals (SQ•),\npairing with their unpaired electrons and quenching SQ• species (C. Liu et al., Acta. Biomater. 2019, 88,\n181). Based on this, “Fe3+ is introduced into the PDA/SA-TCPP composite to selectively complex and\nsuppress SQ• radicals62. EPR measurements (Supplementary Fig. 41a) reveal that complexation with Fe³⁺\nnearly eliminates the SQ• signal. Correspondingly, TAS shows that (Supplementary Fig. 41b), in the\nabsence of SQ•, the sub-bandgap electron transfer from PDA to SA-TCPP is largely impeded, indicating\nthe key role of SQ• in facilitating sub-bandgap electron transfer.” (Supplementary Page 51)\nSupplementary Figure 41. (a) EPR spectra of Fe3+-PDA/SA-TCPP and PDA/SA-TCPP, (b)TAS spectra of Fe3+-\nPDA/SA-TCPP (pump wavelength: 660 nm).\n5. Supplementary Figure 19 appears to depict superoxide radicals rather than •OOH, which directly\ncontradicts the authors' emphasis in the manuscript on •OOH as a key intermediate.\nAnswer: Sorry for the misunderstanding. The EPR spectra of superoxide (•O -) and hydroperoxyl (•OOH)\n2\nradicals are known to be very similar, as the nuclear spin of the H in •OOH has been reported to exert\nonly a negligible influence on the hyperfine coupling constants63,64. Consistently, previous studies have\n10\nshown that the EPR patterns of DMPO-•OOD closely resemble those of DMPO-•OOH. In our work, we\nhave also attempted to detect DMPO-•OOD, and the resulting EPR spectra are indeed very similar to\nthose of DMPO-•OOH, further confirming that the H in •OOH has little effect on the hyperfine splitting.\n(Supplementary Page 57)\nIn our experimental EPR spectra (Supplementary Fig. 45), Peak A is noticeably weaker than the\nothers, making the overall pattern resemble some reported spectra of DMPO-•O - (C. Gu. et al., Nat.\nsimulated DMPO-•OOH spectra. Through spectral fitting in the revised manuscript, we found that this\ndiscrepancy arises from the adduct of SQ• radical signals, whose contribution leads to the apparent\nattenuation of the EPR peak.\nSupplementary Figure 45. EPR spectra of PDA/SA-TCPP recorded in methanol and deuterated methanol.\nGiven the intrinsic difficulty of unambiguously distinguishing •O - and •OOH solely by EPR, we\n2\nfurther performed in-situ FTIR measurements in D O (with DCl to adjust the reaction to pH=4). As shown\n2\nthe Supplementary Fig. 47, the characteristic OOH-related bands exhibit clear isotopic shifts upon D\nsubstitution67, confirming the involvement of •OOH. We attribute the predominance of •OOH rather\nthan •O - to the reaction pH. In our system, the pH is maintained at approximately 4 to prevent\n2\ndissolution of SA-TCPP. According to previous reports66, ORR intermediates predominantly exist as •O -\n2\nunder neutral or alkaline conditions, whereas •OOH is favored in acidic media. Therefore, under our\nexperimental conditions, the ORR intermediates are more reasonably assigned to •OOH rather than •O -.\n2\n(Supplementary Page 59)\nl > 800 nm H O\n2\n*OOH\n.\nu O-O\n.\na\n/\ny\nt\nn\nsi\n*OOD\ne\nt\nn\nI\n1200 1000 800\nWavenumber / cm-1\n2 2\nproduction in H O and D O.\n2 2\n6. The apparent quantum efficiency (AQY) of SA-TCPP should be supplemented. Additionally,\ncomparative analysis with recent high-level works regarding AQY under NIR irradiation is necessary.\nAnswer: As suggested by the reviewers, we have supplemented the AQY of SA-TCPP (Figure 3b) and\ncompared it to the near-infrared light-responsive photocatalyst (Supplementary Table 3). The following\ncomments have been added in the revised manuscript on page 12, lines 18-22. “In the NIR region, the\nAQY values at 850 nm, 940 nm, and 1020 nm are 7.1%, 4.8%, and 2.8%, respectively, approximately 3.0-\n4.0 times as high as those of the SA-TCPP-only photocatalyst (1.6% at 850 nm, 0.87% at 940 nm, and N/A\nat 1020 nm) and surpasses most reported NIR light-responsive photocatalysts (Supplementary Table 3).”\nSA-TCPP\n20\n%\n15\n/\nY\nQ\n5\n0\n400 500 600 700 800 900 1000\nWavelength / nm\nFigure 3b. Apparent quantum yield (AQY) of PDA/SA-TCPP and SA-TCPP for H O generation under light\n2 2\nirradiation using various bandpass filters.\nSupplementary Table 3. The AQY of typical NIR-driven H O -production organic photocatalysts.\n2 2\nMonochromic\nPhotocatalyst Light Source AQY / % Ref.\nWavelength / nm\n13\n850 7.1\n300W Xe lamp with\nPDA/SA-TCPP 940 4.8 This work\nbandpass filters\n1020 2.8\nBCN-OH /Co Monochromatic LED lamp 850 0.8 52\nNi-TphDha\nMonochromatic LED lamp 1000 0.7 54\nCONs\nCo- COFs 900 3.2 55\nbandpass filters\nHCOF 700 0.2 56\nbandpass filters\n7. Related reports indicate that under dark conditions, the catechol molecules in PDA can be oxidized\nby •O - to form catecholquinone, thereby synthesizing H O (Applied Catalysis B: Environment and\n2 2 2\nEnergy, 364 (2025) 124863). This non-photocatalytically induced hydrogen peroxide production\nrequires separate discussion from photocatalytic processes.\nAnswer: Thanks for your comments. We have also noted that dark H O generation on PDA via chemical\n2 2\npathways has been reported, involving the oxidation of catechol moieties to quinone by •O - attack,\n2\nas pointed out by the reviewer (Liu. et al., Applied Catalysis B: Environment and Energy, 2025, 364, 124863).\nHowever, we also note that such reactions are predominantly observed under neutral or alkaline\nconditions, while reports under acidic conditions are rare. This behavior can be rationalized by the pH-\ndependent speciation of semiquinone radicals. Under alkaline conditions, the generated •O - is less\n2\nlikely to react with the negatively charged semiquinone radical anion (SQ•-) because of electrostatic\nrepulsion, favoring its further reduction. In contrast, under acidic conditions, the concentration of\nelectron-rich SQ•- is low (pKₐ of SQ• = 4.88). Consequently, once the •OOH species are formed in the\ndark, they can readily react with neutral SQ•, leading to back reactions that regenerate O₂. To clarify the\npossibility of the dark H O generation under our acidic experimental conditions, we performed control\n2 2\nexperiments for H O production by PDA in the dark at pH = 4 and pH = 10 at 353.15 K (Supplementary\n2 2\nFig. 28a). The results show that PDA-alone does not produce detectable H O under acidic conditions\n2 2\n(pH = 4), whereas measurable non-photocatalytic H O generation occurs only under neutral to alkaline\n2 2\n14\nconditions. Moreover, in alkaline conditions, the H O production activity decreases dramatically in\n2 2\nthe 2nd run (Supplementary Fig. 28b), which is attributed to the irreversible oxidation of catechol to\nquinone in dark reaction. These results indicate that dark chemical H O production on PDA makes only\n2 2\na negligible contribution to the overall photocatalytic H O yield under our acidic experimental conditions.\n2 2\nThe following discussions have been added on Supplementary Page 36. “To exclude the possibility\nof thermally driven H O generation on PDA in the dark, we evaluate the H O production on PDA in the\n2 2 2 2\ndark at pH 4 and 353.15 K (Supplementary Fig. 28a). As a control, H O generation by PDA in the dark at\n2 2\npH 10 and 353.15 K is also examined. The results show that under alkaline conditions, dark H O\n2 2\nproduction on PDA is detectable and comparable to values reported in the literature57. In contrast, PDA\nproduces negligible H O under acidic conditions (pH = 4) in the dark, indicating that chemical H₂O₂\n2 2\ngeneration is insignificant under our experimental conditions. Furthermore, even at pH = 10, sustained\nH₂O₂ production is not observed in the dark (Supplementary Fig. 28b), as the oxidation of catechol to\nquinone is irreversible without photoinduced reduction, thereby terminating the redox cycle. These\nresults confirm that the stable and continuous H₂O₂ production observed for the PDA/SA-TCPP system\ncannot be attributed to dark chemical pathways.”\nSupplementary Figure 28. (a) Time-dependent H O generation on PDA at 353.15 K in dark with different\n2 2\nsolution pHs, (b) The cyclic experiment of PDA was conducted under dark conditions with a solution pH\nof 10.\n15\n8. The increase in temperature will affect the solubility of O , which will also have an impact on the\n2\nformation of H O . This aspect needs to be discussed.\n2 2\nAnswer: We agree with the reviewer that the temperature influences the dissolved oxygen (DO)\nconcentration and may thereby affect the ORR H O production. The discussions related to the dissolved\n2 2\noxygen have been added on Supplementary Page 3-4, “At elevated temperature (353.15 K), the O\n2\nsolubility in H O decreases from 8.26 mg/L at 298.15 K to 4.0 mg/L5. Despite the decrease in O solubility,\n2 2\nthe elevated temperature simultaneously enhances the diffusivity of the dissolved O and thereby\n2\naccelerates O transport to the catalyst surface. The volume-mass transfer rate of O is calculated to be\n2 2\nca. 33.8-91.3 mM/h, far exceeding the estimated O consumption (1.6 mM/h) based on the H O\n2 2 2\nproduction rate of PDA/SA-TCPP, indicating sufficient O supply. Consequently, dissolved O may not be\n2 2\nthe rate-limiting factor for H₂O₂ formation at elevated temperature conditions.”\nThe detailed calculations of the volume-mass transfer rate of O are shown in the Supplementary\n“The calculations of volume-mass transfer rate of O at 353.15 K\nD =\n7.4×10−8(ϕMB)1/2T\nEq. SX\nAB ηV0.6\nA\nwhere D is the diffusion coefficient (cm2/s), φ is the solvent association factor (2.26 for water), M is\nAB B\nthe molecular weight of the solvent (18.0 g/mol), T is the absolute temperature (K), η is the dynamic\nviscosity (298.15 K: 𝜂 = 0.890 cP, 353.15 K: 𝜂 = 0.355 cP), and V is the molar volume of O at its boiling\nA 2\npoint (25.6 cm³/mol) (R. N. Maddox, et al., Mass transfer: Fundamentals and applications, Prentice-Hall,\n1985).\nThe diffusion coefficients of O in water at 298.15 and 353.15 K are calculated as 2.27×10-5 cm2/s\n2\nand 6.72×10-5 cm2/s, respectively. Therefore, although the increase in temperature leads to a half\ndecrease in the solubility of O (at 298.15 K: approximately 8.26 mg/L, and at 353.15 K: approximately\n2\n4.0 mg/L), the diffusion coefficient of O has a triple increase, which may compensate for the loss of the\n2\nsolubility of oxygen at elevated temperature.\n2\ncondition, the instantaneous dissolved O concentration is not solely governed by temperature-\n2\ndependent solubility. Instead, the supply of O to our photocatalyst is determined by the volume-mass\n2\ntransfer rate of O , which in the liquid phase can be expressed by the classical gas-liquid mass transfer\n2\nmodel as (L. Johnny, Heliyon 2017, 3, e00248):\n𝑅 =\n𝑘𝐿𝑎(𝐶∗−𝐶)\n=\n𝑆ℎ𝐷𝑂2\n×\na(𝐶∗−𝐶)\nEq.SX\n𝑂2\n𝑀𝑂2 𝐿 𝑀𝑂2\nwhere R represents the molar supply rate of O per unit volume (mM/h), K a is the volume-mass\nO2 2 L\ntransfer coefficient, D is the liquid-phase diffusion coefficients of O (6.72×10-5 cm2/s at 353.15 K), Sh\nO2 2\nis the Sherwood number (10) (M. Hasan. et al., Plasma. Chem. Plasma. Process. 2021, 41, 1363) L is a\ncharacteristic length (distance from the outlet of the gas-bubbling pipe to the surface of suspended\nphotocatalysts), set in this work as the average of the liquid depth (2 cm), C∗ is the solubility of O in\n2\nwater (4.0 mg/L at 1 atm and 353.15 K), a is gas-liquid interface area ratio (300 - 800 cm-1) (K. Riet. Ind.\nEng. Chem. Process Des. Dev. 1979, 18, 3), C is the instantaneous dissolved O concentration in water (2.0\n2\nmg/L, which is the residual O concentration after per minute H O production), and M is the molar\n2 2 2 O2\nmass of oxygen (32 g/mol). Accordingly, the volume-mass transfer rate of oxygen is ca. 33.8-91.3 mM/h.”\n9. Performance tests conducted at 353.15 K claim negligible H O decomposition (Supplementary\n2 2\nFigure. 38). However, elevated temperature itself might promote non-photocatalytic pathways. (1)\nDark reaction controls or low-temperature activity comparisons should be provided to exclude thermal\neffects. (2) Furthermore, justification is required for why H O decomposition is negligible in this system\n2 2\ndespite its general susceptibility during photocatalysis.\nAnswer: Thanks for the comments.\n(1) Following the reviewer’s suggestions, the thermal effects are excluded by evaluating H O\n2 2\nproduction at elevated temperature (353.15 K) in the dark (Fig. I, review on), and by comparing the\nH O production at 298.15 K and 353.15 K. (Supplementary Fig. 12)\n2 2\nFig. I shows that, at 353.15 K in the dark, negligible H O is detected for the PDA/SA-TCPP system\n2 2\nat pH = 4, whereas 0.68 mM H O is observed at pH = 10. These results demonstrate that under our\n2 2\n17\nacidic experimental conditions, thermal effects alone do not induce H₂O₂ generation, even at elevated\ntemperature. This activity is similar to dark reaction on pure PDA (Supplementary Figure 28). To avoid\ndata duplication, the data is only used for the response.\nTo further exclude thermal contributions under irradiation, “Supplementary Fig. 12 compares H O\n2 2\nproduction on PDA alone at 298.15 K and 353.15 K using λ > 420 nm and λ > 800 nm cutoff filters. SA-\nTCPP is not evaluated together with PDA in this control experiment because the thermal contribution in\nthe SA-TCPP-alone system has been previously investigated13.In that system, although thermal effect\ndoes not directly initiate H O formation, photogenerated holes lead to the formation of TCPP-COOOH\n2 2\nintermediates, and thermal effect accelerates the hydrolysis of peroxy acid groups to yield H O while\n2 2\nregenerating TCPP. Here, to specifically probe direct H O production induced by thermal effects, we\n2 2\nfocus on PDA alone, thereby excluding the possibility that thermal effect enhances hole-induced H₂O₂\ngeneration from SA-TCPP under irradiation. The reaction pH is maintained at 4 to ensure consistency with\nthe PDA/SA-TCPP system.”\nAt 298.15 K, negligible H O is detected with PDA under both λ > 420 nm and λ > 800 nm irradiation.\n2 2\nAt 353.15 K, negligible H O is still observed with the λ > 800 nm cutoff filter, whereas 0.29 mM H O\n2 2 2 2\naccumulates with PDA after 4 h under λ > 420 nm irradiation. Considering that 11.24 mM H O is\n2 2\nproduced in the PDA/SA-TCPP system under identical conditions, the maximum contribution of thermal\neffects of PDA to the overall H O production is estimated to be less than 3%. (Supplementary Page 17)\n2 2\nAccording to the above results, in the PDA/SA-TCPP system, the thermal effect plays only a minor\nrole and cannot account for the high and sustained H O production observed in the PDA/SA-TCPP system.\n2 2\nIn particular, the thermal effect will barely contribute to the H O production under NIR light irradiation.\n2 2\n18\n0.8\nM pH = 10.0\nm pH = 4.0\n/\n0.6\nn\no\ni\nt\na\nr\nn t 0.4\ne\nc\nn\no\nc 0.2\n0.0\n0 1 2 3 4\nIrradiation time / h\nFigure I (review on). Time-dependent H O generation on PDA/SA-TCPP at 353.15 K in the dark with\n2 2\ndifferent solution pHs.\n0.4\nM l > 420 nm l > 800 nm\nm\n/\n0.3\nn\no\nti\na\nr\nn\nt0.2\ne\nc\nn\no\nc0.1\nN.D. N.D. N.D.\n0.0\n298.15 353.15 298.15 353.15\nSolution temperature / K\nSupplementary Figure 12. H O generation on PDA by under visible (λ>420 nm) and NIR (λ>800 nm)\n2 2\nirradiation.\n(2) We agree with the reviewer that although Figure S38 in the original manuscript shows negligible H O\n2 2\ndecomposition at 353.15 K, this observation alone does not imply that H O is intrinsically stable under\n2 2\nphotocatalytic conditions at elevated temperature. Indeed, H O is generally susceptible to\n2 2\ndecomposition during photocatalysis due to overreaction with photogenerated electrons and holes on\ncatalyst surfaces, yielding O and H O. In our system, however, we believe that the observed stability and\n2 2\nnear-linear increase of H O concentration arise from the following three factors.\n2 2\n2 2\ndecomposition is kinetically insignificant. The apparent H O production rate reflects the difference\n2 2\nbetween the formation rate and the decomposition rate, with the latter being strongly dependent on\nH O concentration. As shown in Supplementary Fig.66, the measured H₂O₂ decomposition rates under\n2 2\nAr atmosphere are 0.001, 0.008, and 0.012 mM/min at initial H O concentrations of 10.37 mM\n2 2\n(comparable to the maximum H O concentration achieved for PDA/SA-TCPP during our experiments),\n2 2\n21.65 mM, and 31.43 mM, respectively, whereas the H O formation rate is 0.06 mM/min. These\n2 2\nresults indicate that H O decomposition is negligible under our experimental conditions. Nevertheless,\n2 2\nin the long-term accumulation experiments shown in Figure 3d of the main text, a gradual decrease in\nthe apparent H₂O₂ production rate (from 3.32 mM/h to 2.01 mM/h) is observed with prolonged reaction\ntime, which we attribute to the increased contribution of H O decomposition as its concentration\n2 2\naccumulates.\nSupplementary Figure 66. (a) H O decomposition rates measured under an Ar atmosphere at different\n2 2\ninitial H O concentrations (10.37 mM, 21.65 mM, and 31.43 mM), (b) Photocatalytic H O formation\n2 2 2 2\nrate of the PDA/SA-TCPP system. Reaction conditions: Sln., 50 mL H O; Light source, 300 W Xe lamp with\n2\na 420 nm cut-off filter; Reaction temperature, 353.15 K; Photocatalyst concentration, 4.0 g/L.\nSecond, efficient H₂O₂ decomposition in photocatalytic systems is often associated with the\npresence of transition-metal species with readily accessible valence states, such as Ti, Mn, Fe, Co, Ni, or\nCu, which exhibit strong affinity toward H O , and easily catalyze redox-driven decomposition pathways.\n2 2\nthe H₂O₂ decomposition.\nThird, the weak interfacial affinity between the catalyst surface and H O promotes rapid desorption\n2 2\nof newly formed H O , minimizing its residence time on reactive sites. In the revised manuscript, we\n2 2\nprovide contact angle measurements for PDA/SA-TCPP (Supplementary Fig. 67), showing that the\ncontact angle of H O (21.5°) is significantly smaller than that of H O (52.8°). This contrast indicates\n2 2 2\nthat H O is readily displaced by surrounding H O molecules and desorbs from the catalyst surface,\n2 2 2\nthereby suppressing surface-induced decomposition by photogenerated electrons and holes.\na b\nH O H O\n2 2 2\n52.8°\n21.5°\nSupplementary Figure 67. Contact angle measurements of (a) H O and (b) H O droplets (85 wt%) on the\n2 2 2\nPDA/SA-TCPP surface. The 85 wt% H₂O₂ is concentrated from commercial 30 wt% H O by vacuum\n2 2\ndistillation at 373.15 K.\nThe following discussions are added on Supplementary Page 84. “At 353.15 K, H O decomposition in\n2 2\nthe PDA/SA-TCPP system is negligible under low-concentration conditions (10 mM; Supplementary Fig.\n66a). In addition, the system is free of transition-metal species that readily catalyze H O decomposition,\n2 2\nand PDA/SA-TCPP exhibits a weaker surface affinity toward H O than toward water (contact angles: H O,\n2 2 2\n21.5°; H O , 52.8°; Supplementary Fig. 67). These factors justify neglecting H₂O₂ decomposition under\n2 2\nthe experimental conditions employed.”\n21\n10. (1) While the manuscript mentions enhanced photothermal conversion efficiency by PDA\n(Supplementary Figure. 32-33), it fails to distinguish specific contributions of photothermal effects to\nreaction rates (e.g., local heating-enhanced O diffusion vs. thermal catalytic reactions). (2) Isothermal\n2\ncontrol experiments are recommended to quantify photothermal effects.\nAnswer: Thanks for your suggestions.\n(i) In the revised manuscript, we provide quantitative analysis of O₂ diffusion coefficients and the\nassociated mass transfer to the photocatalyst surface at elevated temperature. The detailed\ncalculations are presented in our responses to the reviewer’s Questions 8 and supplementary\ninformation S1 (on page 2). Briefly, the diffusion coefficients of O in water at 298.15 and 353.15 K are\n2\ncalculated as 2.27×10-5 cm2/s and 6.72×10-5 cm2/s, respectively, corresponding to a volume-mass transfer\nrate of O to be ca. 35.7-96.5 mM/h and ca. 33.8-91.3 mM/h at 298.15 and 353.15 K. The similar O\n2 2\nmass-transfer rate at room temperature and elevated temperature indicates that temperature will not\ninfluence the O supply in our system. Also, it is important to note that the supplied O flux far exceeds\n2 2\nthat required for H O generation via ORR (ca. 1.6 mM/h), indicating that O mass transfer is not the rate-\n2 2 2\nlimiting step under our experimental conditions.\nWe further evaluated the contribution of thermal catalytic effects to the observed photothermal\nH O production. Thermal effects may influence several processes, including (i) hole transfer in SA-TCPP,\n2 2\nas clarified in our response to Question 3 and in our previous study (C. Pan. et al., Nat. Energy 2023, 8,\n361); (ii) dark H O production at elevated temperature, which is shown to be negligible\n2 2\n(Supplementary Fig. x); and (iii) the ORR pathway, which is discussed below.\nSupplementary Fig. X compares H₂O₂ production on PDA/SA-TCPP at 298.15 K and 353.15 K using\nisopropanol (IPA) as a hole scavenger, thereby isolating the influence of thermal effects on ORR-driven\nH₂O₂ formation. Only a modest enhancement (1.2-fold) is observed at 353.15 K relative to 298.15 K,\nindicating that while elevated temperature can slightly facilitate ORR kinetics, it is not the primary\ncontributor to the overall enhancement in H O production.\n2 2\nBased on these analyses, we conclude that the dominant role of thermal effects in the PDA/SA-\nTCPP system is to promote hole-related processes, facilitating the hydrolysis of hole-oxidized peroxy acid\nintermediates into H O , consistent with our previous findings in the SA-TCPP-only system.\n2 2\nphotothermal contribution to H O production, control experiments are performed. Thermal effects may\n2 2\ninfluence H O production via dark H O formation, ORR acceleration, or hole transfer. However,\n2 2 2 2\nnegligible H O generation is observed for PDA, SA-TCPP, and PDA/SA-TCPP in the dark at 353.15 K and\n2 2\npH = 4, excluding thermal-driven H O production. (Supplementary Fig. 29) Using isopropyl alcohol (IPA)\n2 2\nas a hole scavenger, only a modest ca. 1.2-fold enhancement in H O production is observed at 353.15 K\n2 2\ncompared to 298.15 K, indicating that ORR acceleration is not the dominant factor. (Supplementary Fig.\n31) Therefore, by excluding the above two possibilities, thermal effects may primarily accelerate the\nhydrolysis of hole-oxidized peroxy acid intermediates, consistent with the results in Supplementary Fig.\n32 and our previous observations for the SA-TCPP-alone system, while H O production is dominated by\n2 2\nthe photocatalytic process and the associated photogenerated charge separation.”\n1.0\nM PDA/SA-TCPP\nm SA-TCPP\n0.8 PDA\n/\nn\no\ni\na\nt0.6\nr\nt\nn\ne\nc0.4\nn\no\nc\n20.2\nO\n0.0\n0 1 2 3 4\nIrradiation time / h\nSupplementary Figure 29. Photocatalytic H O production on PDA, SA-TCPP, and PDA/SA-TCPP under\n2 2\ndark conditions at elevated temperature (353.15 K). Reaction conditions: Sln., 50 mL H O; Light source,\n2\n23\nm\n/\nn\no 4\ni\nt\na\nr\nt\nn\ne\nc\nn\n2\no\nc\n0\n298.15 353.15\nSolution temperature / K\nSupplementary Figure 31. Photocatalytic H O production on PDA/SA-TCPP within 1 h reaction at 298.15\n2 2\nK and 353.15 K in the presence of IPA as a hole scavenger. Reaction conditions: Sln., 50 mL H O; Light\n2\nsource, 300 W Xe lamp with a 420 nm cut-off filter; Photocatalyst concentration, 4.0 g/L.\n(2) As suggested by the reviewers, “isothermal control experiments are conducted to clarify the\ncontribution of heat to the photocatalytic activity (Supplementary Fig. 30). The H O production rate of\n2 2\nPDA/SA-TCPP clearly increases with temperature: after 4 h reaction, the H O concentration reaches 1.55\n2 2\nmM at 293.15 K and increases to 3.22 mM, 7.18 mM, and 11.74 mM at 313.15, 333.15, and 353.15 K,\nrespectively. Notably, H O accumulation at 353.15 K is ca. 7 times higher than that at 293.15 K, far\n2 2\nexceeding the temperature-induced enhancement observed when IPA is used as a hole scavenger\n(Supplementary Fig. xa. This indicates that although heat may accelerate the ORR, it is not the dominant\nfactor. Given the negligible H O generation for PDA, SA-TCPP, and PDA/SA-TCPP in the dark at 353.15 K\n2 2\nand ph = 4 (Supplementary Fig. 30b), the thermal effect is mainly attributed to enhanced hole transfer\nand subsequent decomposition of hole-oxidized intermediates, consistent with our previous\nobservations for the SA-TCPP system.” (Supplementary Page 38)\nm 333.15 K\n313.15 K\n/\nn 293.15 K\no\nt i 8\na\nr\nt\nn\ne\nc\nn\no 4\nc\n0\n0 1 2 3 4\nIrradiation time / h\nSupplementary Figure 30. Time-dependent H O production on PDA/SA-TCPP at different solution\n2 2\ntemperatures. The solution temperature is controlled by a water bath or recirculating cooling water\nsystem.\n11. Data on pure PDA should be supplemented and compared with SA-TCPP and PDA/SA-TCPP.\nAnswer: Thanks for your comments. As suggested, we have added the UV-Vis-NIR DRS spectra of the\npure PDA in Figure 2d in the revised manuscript. We have also added the H O production of PDA itself\n2 2\nin Figure 3d in the revised manuscript. The following discussions have been added in the revised main\ntext (Page 10, Lines 19-20 and Page 14, Lines 11-12). “As shown in Figure 2d, pure PDA has a strong broad\nabsorption spectrum up to 1500 nm.” and “PDA/SA-TCPP accumulates 52.2 mM H O (0.16 wt%) after\n2 2\n24 h irradiation, which is 2.6 times higher than SA-TCPP alone and 130 times relative to pure PDA”\nSA-TCPP\n.\nu 385 PDA\n. 357\na\n/\ne\nc\nn\na\nb\nr\no\ns\nb\nA\n300 600 900 1200 1500\nWavelength / nm\nFigure 2d. The UV-Vis-NIR DRS spectra of PDA, SA-TCPP, and PDA/SA-TCPP.\nm SA-TCPP (0.16 wt%)\nPDA\n/\n45\nn\no\ni\nt\na\nr\nt\nn\ne 30\nc\nn\no\nc 15\n2 0.4 mM\nH\n0\n0 4 8 12 16 20 24\nIrradiation time / h\nFigure 3d. The H O production performance of PDA, SA-TCPP, and PDA/SA-TCPP.\n2 2\n12. Adding XPS testing further confirms the successful synthesis of PDA.\nAnswer: Thanks for your suggestions. The XPS testing has been added as Supplementary Fig. 4 in the\nSupplementary information (Page 8). The following discussions have been added following the Figure\n26\n“Supplementary Fig.4 shows the XPS of the prepared PDA. The wide-scan spectrum reveals the presence\nof C, N, and O elements. The narrow scan of the C 1s XPS peak is deconvoluted into five components\nlocated at 284.8, 285.8, 287.0, 288.6, 289.9, and 291.1 eV, corresponding to sp3 C, sp2 C, C-O, C-N, C=N,\nand C=O, respectively. The narrow scan of the N 1s XPS peak exhibits two peaks at 399.9 and 401.6 eV,\nwhich are assigned to C-N and C=N groups. The narrow scan of the O 1s XPS peak shows three peaks at\n531.5, 532.2, and 535.6 eV, corresponding to C=O, C-O, and surface -OH groups, respectively. These\nresults are consistent with the reported dihydroxyindole and indoledione units with varying degrees of\nunsaturation in PDA11.12, confirming the successful synthesis of PDA.”\nSupplementary Figure 4. XPS characterization of the prepared PDA. (a) Wide scan spectrum. Narrow-\nscan spectra of (b) C 1s, (c) N 1s, and (d) O 2p.\n13. The loading optimization of PDA/SA-TCPP composites was evaluated solely based on H O yield,\n2 2\nwithout considering factors such as light absorption and charge separation efficiency.\nwith the light absorption and charge separation efficiency in the Supplementary information. “The UV-\nVis DRS spectra of PDA/SA-TCPP composites with different PDA loading amounts are provided to\nillustrate the optimization of PDA loading with respect to light absorption. Supplementary Fig. X shows\nthat increasing the PDA content leads to a gradual enhancement of absorption in the NIR region (800-\n1500 nm), whereas the characteristic absorption peaks of SA-TCPP become less distinguishable. This\nresult indicates that higher PDA loading can enhance NIR-light absorption but simultaneously shield the\nintrinsic light absorption of SA-TCPP. At relatively low PDA loading amounts, the increased NIR\nabsorption may contribute positively to NIR-driven photocatalytic activity. However, since H O\n2 2\nproduction primarily originates from the photogenerated electrons and holes of SA-TCPP, excessive PDA\ncoverage may hinder light harvesting and charge generation on SA-TCPP. Such a shielding effect likely\nreduces the availability of photogenerated charge carriers, leading to a decrease in photocatalytic\nactivity at high PDA contents. The optimized mass ratio between PDA and SA-TCPP is 1.1 by considering\nthe activity.” (Supplementary Page 78).\nSupplementary Figure 63. The ultraviolet-visible near-infrared diffuse reflectance spectrum (UV-Vis NIR\nDRS) of X-PDA/SA-TCPP.\nwith varying PDA loading amounts to show the loading optimization with the charge separation\nefficiency. The method is often used to evaluate the charge separation efficiency in the literature (R.\nGomez, et al., J. Phys. Chem. C. 2008, 112, 139). “As shown in Supplementary Fig. 64, increasing the ratio\nof PDA: SA-TCPP from 0.5 to 1.1, the photocurrent increases from 2.1 μA/cm2 to 6.8 μA/cm2. In contrast,\nfurther increasing the ratio to 1.5 leads to a decrease in the photocurrent to 3.0 μA/cm2. The transient\nphotocurrent tests show that the highest charge separation efficiency is on the sample of 1.1-PDA/SA-\nTCPP, similar to the photocatalytic activity trend with different PDA contents. The OCP test also showed\nresults similar to those of the photocurrent.” (Supplementary Page 79).\nSupplementary Figure 64. (a) Transient photocurrent and (b) Open-circuit potential of X-PDA/SA-TCPP.\n14. The paper mentions that SA-TCPP crystallinity varies with temperature, yet its H O production\n2 2\nperformance remains similar. Further explanation of this phenomenon is required.\nAnswer: Thank you for your comment. In general, crystalline photocatalysts, particularly inorganic\nsemiconductors, exhibit higher photocatalytic activity than their amorphous counterparts due to more\nefficient charge separation and transport. In our previous work, crystalline SA-TCPP showed an H O\n2 2\nproduction rate of 1.62 mM/h, whereas the amorphous SA-TCPP used in the present study exhibits a\nslightly lower rate of 1.35 mM/h. Although this corresponds to a ca. 16.7% decrease in activity, the\n29\noverall difference is modest, indicating that crystallinity is not the decisive factor governing the\nphotocatalytic performance.\nThis behavior is consistent with the charge-transport mechanism in supramolecular\nphotocatalysts. Unlike inorganic semiconductors, where charge carriers move as delocalized waves\nthrough long-range ordered lattices, electron transfer in supramolecular systems such as SA-TCPP is\ngenerally described as hopping between localized molecular states mediated by hydrogen bonding or\nπ-π interactions. Consequently, the electron diffusion length in supramolecular systems (typically tens\nof nanometers, F. Zhao, et al., Adv. Func. Mater. 2025, 35, 2505200) is much shorter than that in inorganic\nsemiconductors (e.g., several micrometers in TiO₂, A. Walker. et al., J. Am. Chem. Soc. 2008, 130, 13364).\nIn addition, recent studies have also demonstrated that short-range ordering alone can be sufficient to\nenable efficient charge separation in organic photocatalysts, including porphyrin supramolecules (C. Pan.\net al., Angew. Chem. Int. Ed. 2025, 64, e202512844), covalent organic frameworks (C. Huang. et al., Adv.\nMater. 2025, e11092), and defective polymeric photocatalysts (X. Wang. et al., Angew. Chem. Int. Ed.\n2025, 64, e202507415; S. Mao. et al., Nat. Commun. 2025, 16, 6943). In some cases, organic\nphotocatalysts with only short-range order even outperform their highly crystalline counterparts. (R.\nMarschall.et al., Small Struct. 2023, 4, 2200184)\nIn our system, although SA-TCPP prepared at 298.15 K shows nearly amorphous crystallinity\ncompared with that prepared at 353.15 K, PL spectra analysis (Supplementary Fig. 61) confirms that\nthe characteristic J-stacking motif is preserved. This indicates the presence of short-range molecular\nordering, which we believe plays a dominant role in sustaining efficient photocatalytic activity.\nTherefore, consistent with other supramolecular photocatalytic systems, the observed H O production\n2 2\nis primarily governed by short-range ordering rather than long-range crystalline order. Corresponding\ndiscussion has been added to the revised manuscript.\n“Although SA-TCPP exhibits an amorphous structure, its photocatalytic activity is comparable to that\nof the reported crystalline counterpart, which may be due to the similar short-range ordering structure.\nThe reported crystalline SA-TCPP is a J-type aggregation13. To elucidate the supramolecular π-stacking\nstructure of amorphous SA-TCPP, PL spectra are comparatively investigated in the supramolecular state\n30\n(solid powder) and the molecular state (homogeneous solution measured in THF). Amorphous SA-TCPP\npowder exhibits two distinct PL emission peaks at 653 nm and 718 nm, which are assigned to the\nradiative transitions from the excited state to the ground state Q (0, 0) and to the vibrationally excited\nx\nground state Q (0, 1), respectively. In contrast, the corresponding PL peaks of molecular SA-TCPP are\nx\nblue-shifted to 649 nm and 713 nm. This characteristic spectral shift from the molecular to the\nsupramolecular state indicates that amorphous SA-TCPP is a J-type aggregation80. Such short-range\nordering in the amorphous SA-TCPP may be sufficient to enable efficient charge separation in organic\nsemiconductors 81, thereby leading to comparable photocatalytic activity relative to the crystalized one.”\n(Supplementary Page 76)\nAmorphous SA-TCPP\nTCPP in THF\nQ (0,0)\n.\nu x\n. 653 nm\na Q (0,1)\nx\n/\ny 718 nm\nt\ni\ns\nn\ne\nt\nn 649 nm\nI\n713 nm\n600 650 700 750 800\nWavelength / nm\nSupplementary Figure 61. PL spectra of amorphous SA-TCPP powder and TCPP in THF (excitation: 420\nnm).\n15. Although H O yield and SCC efficiency outperform comparable studies, the reaction temperature\n2 2\nused is difficult to sustain in practical solar applications. Evaluating performance at room temperature\nor clarifying the feasibility of elevated temperatures for real-world use is recommended. Additionally,\nthe outdoor SCC efficiency of only 0.12% differs significantly from laboratory conditions, necessitating\ndiscussion of practical limitations (e.g., light intensity, temperature, catalyst stability).\n(353.15 K) is difficult to sustain under practical solar conditions. In addition, we note that most reported\nhigh solar-to-chemical conversion (SCC) efficiencies for H O production are obtained in suspended\n2 2\npowder systems, whereas immobilized film systems are generally more relevant for practical applications.\nSince the SCC performance of the SA-TCPP powder system under both laboratory and outdoor\nconditions has been reported previously by our group (C. Pan et al., Nat. Energy 2023, 8, 361), and the\nPDA/SA-TCPP powder system in this work exhibits an SCC of the same order of magnitude as that of\nthe SA-TCPP powder, we provided the outdoor SCC efficiency of a PDA/SA-TCPP film to assess its\npractical potential in the original manuscript. As expected, the film system shows much lower activity\nthan the suspended powder due to the limited accessible surface area, resulting in an outdoor SCC of\n0.12% for the film compared with 2.12% for the powder in the laboratory. As expected, the film system\nexhibits a much lower SCC than the suspended powder, because the increase in irradiation area and\ncatalyst amount in the film is not proportional to that in the powder. This discrepancy arises from the\nintrinsically limited accessible surface area of the film compared with the powder, leading to an outdoor\nSCC of 0.12% for the film, in contrast to 2.12% for the powder under laboratory conditions. Despite this\nreduction, the obtained SCC remains relatively high among reported film-based systems\n(Supplementary Table 9) and may serve as a starting point for further practical optimization. In fact, in\na recent study, we immobilized SA-TCPP onto quartz wool and achieved an activity comparable to that of\nthe suspended powder system with the same catalyst amount (Figure I, reviewer only, C. Pan, et al., EES.\nSolar, 2025, 1, 1115). Inspired by this result, future work will focus on immobilizing PDA/SA-TCPP onto\nporous supports such as quartz wool to reduce the current SCC gap between powder and immobilized\nconfigurations.\nConsidering the reviewer’s concern that the large difference between the SCC values of the PDA/SA-\nTCPP powder and film systems may confuse readers, “For three consecutive days using the same\nphotocatalyst, the PDA/SA-TCPP powder achieves a SCC efficiency of 1.81% in average, slightly lower than\nthat obtained under laboratory conditions due to solar intensity and solution temperature\n(Supplementary Fig. 59 and Table 8)” (Page 21, line 18-21, main text)\n2 2\nSupported Reaction H O production\n2 2\nSupport Light source Refs.\nphotocatalyst time (h) rate (μM/h)\nλ > 420 nm,\nPDA/SA-TCPP Quartz plate 4 992.00 This work\nλ > 420 nm,\nHydrogel Ca (II)@ACG rGO 10 204.30 75\nMelamine foam Graphene, PTFE 6 587.00 76\n1.5 G\nCarbon fiber λ > 420 nm,\nTPB-DMTP-COF 5 580.00 77\npaper 300 W\nFuran-BILP hollow λ > 420 nm,\nCarbon cloth 5 73.33 78\nmicrofibers 300 W\nTTP Quartz cover, λ > 420 nm,\n6 626.40 79\n(organicpolymers) 25% nafion 300 W\nFigure. (Reviewer only) Comparison of the H O yields between SA-TCPP powder and NH -PDMS/SA-\n2 2 2\nTCPP/Quartz Wool (QW) composite at 353.15 K. (Insets) Photographs showing the SA-TCPP powder (left)\nand the immobilized NH -PDMS/SA-TCPP/QW composite (right)\n2\n33\n4 2.5\nM\nm\n2.0\n/ 3\nn\no\ni % 1.5\nt\na\nm u l 2 C /\nC\nu 1.0\nc S\nc\na 1\n2 0.5\nO\n0 0.0\n1 2 3 4\nIrradation time / h\nSupplementary Figure 59. H O production and SCC efficiency under real sunlight recorded from 10 : 00\n2 2\nto 14 : 00 at Sept. 17, 2023. Location: Wuxi, China (120.27° E, 31.48° N).\nSupplementary Table 8. The SCC efficiency and H O production on PDA/SA-TCPP irradiated by real\n2 2\nsunlight obtained at Wuxi, China (120.27° E, 31.48° N) from Sept. 17 to 19, 2023.\nTime (Sept. 17, 2023) 10:00 11:00 12:00 13:00 14:00\nT / K 299.25 299.55 300.45 300.75 300.95\nambient\nT / K 299.25 330.25 334.85 355.05 335.15\nsolution\nLight Intensity / mW·cm-2 62.4 50.7 52.4 46.8 53.1\nC(H O ) / mM 0 0.52 1.21 1.86 2.44\n2 2\nSCC / % 1.61 1.96 1.92 1.73\nTime (Sept. 18, 2023) 10:00 11:00 12:00 13:00 14:00\nT / K 303.35 303.95 304.65 305.05 305.35\nambient\nT / K 303.35 331.75 335.75 336.15 336.15\nsolution\nLight Intensity / mW·cm-2 60.2 60.9 58.8 53.9 52.2\n2 2\nSCC / % 1.42 1.67 1.88 1.96\nTime (Sept. 19, 2023) 10:00 11:00 12:00 13:00 14:00\nT / K 298.35 298.65 299.35 299.95 301.35\nambient\nT / K 298.35 330.55 334.45 335.55 335.45\nsolution\nLight Intensity / mW·cm-2 52.4 48.5 45.3 47.6 46.1\nC(H O ) / mM 0 0.45 1.01 1.59 2.21\n2 2\nSCC / % 1.39 1.86 1.86 1.97\n16. Further applications of H O should be discussed.\n2 2\nAnswer: Thanks for your suggestions. In the revised manuscript, we have added the application of in-situ\nphotocatalytically produced H O in our system for the use of continuous Fenton degradation of organic\n2 2\npollutants in wastewater. The device is shown in Figure 5d. The following discussions have been added\nin the revised main text (Page 22, Lines 13–19): “Given the excellent photocatalytic H O production\n2 2\nactivity of PDA/SA-TCPP, an integrated system for in-situ H O generation and pollutant degradation is\n2 2\ndesigned, as illustrated in Fig. 5d. Representative pollutants, including methylene blue (MB) and\nciprofloxacin (CIP), are employed to evaluate the removal efficiency of the system. In the device, the\nconcentration of in-situ produced H O reaches a stable level of 2.1 mM during the reaction at a flow\n2 2\nspeed of 2 mL/min. Within 12 min, nearly 95% of both pollutants are removed, corresponding to a\ndegradation rate of 0.23 min-1 and 0.21 min-1, respectively. (Supplementary Fig. 60) These results\ndemonstrate the effectiveness of the H O -producing system for pollutant removal and water purification.\n2 2\n2 2\nppm) is used as a representative pollutant. The outlet pipe transferring the generated H O to the MB\n2 2\nsolution is covered with a semi-permeable membrane to prevent PDA/SA-TCPP powder from entering\nthe MB solution. The inset shows the MB solution after degradation.\nSupplementary Figure 60.(a) The degradation curves of CIP and MB via Fenton reaction with the H O\n2 2\nin-situ produced in the PDA/SA-TCPP system. (b) The corresponding degradation rates of the CIP and MB.\n17. Comparative experiments are lacking where PDA is loaded onto other infrared catalyst supports to\ndemonstrate the universality or specificity of this strategy.\nAnswer: We thank the reviewer for the valuable comments. In the revised manuscript, we have\nprovided additional experimental data to demonstrate the applicability of the PDA-assisted catalytic\n36\nstrategy across a range of inorganic and organic NIR-responsive materials, including Bi CoO , black\n12 20\nTiO2, Zn-TCPP, and CoPc. Because PDA mainly promotes the ORR pathway, while the WOR side may limit\noverall H O generation, the universality of the NIR-enhancement strategy may not be evident in systems\n2 2\nwhere hole transfer is inefficient. To address this issue and enable a fair comparison across different\nphotocatalysts, IPA is introduced as a sacrificial reagent in selected systems, allowing the generality of\nthe PDA-assisted NIR enhancement to be more reliably evaluated. The detailed results are shown below.\n“Four NIR-adsorption materials, including Bi CoO (prepared according to the method reported\n12 20\npreviously by our group, C. Pan, et al., J. Catal. 2023, 428, 115172), black TiO (B-TiO , prepared according\n2 2\nto the reported method, L. Li. et al. Nat. Energy 2022, 7, 1042), commercial zinc porphyrin (Zn-TCPP, 95%,\npurchased from Beijing InnoChem Science & Technology Co, Ltd, China), and commercial\n(Tetracarboxyphthalocyaninato) cobalt (II) (CoPc, 95%, purchased from Xi'an Qiyue Biotechnology Co.,\nLtd, China), are selected and individually coupled with PDA to construct PDA/Bi CoO , PDA/B-TiO₂,\n12 20\nPDA/CoPc, and PDA/Zn-TCPP composites.\nAs shown in Supplementary Fig. 53a-d, the UV-Vis-NIR DRS spectra indicate that Bi CoO , B-TiO₂,\n12 20\nZn-TCPP, and CoPc all exhibit NIR absorption in the 800-1200 nm region. The H O generation rates of\n2 2\nthese systems under NIR irradiation (λ > 800 nm) with and without PDA loading are compared in\nSupplementary Fig. 53e. The results reveal that PDA loading significantly enhances H O production, with\n2 2\nthe H O yield of PDA/Bi CoO , PDA/B-TiO₂, PDA/CoPc, and PDA/Zn-TCPP increasing by 5.0, 2.5, 5.4,\n2 2 12 20\nand 7.8-fold, respectively, relative to the counterparts without PDA loading. These results demonstrate\nthat the PDA loading can efficiently promote the NIR-driven ORR to H O .” (Supplementary Page 64)\n2 2\n12 20 2\nComparison of H O generation rates under NIR irradiation (λ > 800 nm) for Bi CoO , B-TiO₂, CoPc, and\n2 2 12 20\nZn-TCPP, and their PDA-loaded composites. Reaction conditions: Cat., 4.0 g/L , Sln., 50 mL H O (or 10 vol%\n18. Does the hydrogen bonding interaction between PDA and SA-TCPP make a substantial contribution\nto electron transfer?\nAnswer: Thank you for your valuable comments. We propose that hydrogen bonding between PDA and\nSA-TCPP plays a critical role in facilitating interfacial electron transfer. To verify this hypothesis, in the\nrevised manuscript, we deliberately disrupted the hydrogen bonding by thermally treating the PDA/SA-\nTCPP composite at 423.15 K for 2 h under an N₂ atmosphere. As confirmed by FTIR analysis\n(Supplementary Fig. 42a), after heat-treatment, the characteristic FTIR peak shifts associated with\nhydrogen-bond formation between PDA and SA-TCPP disappear, indicating that the hydrogen bonding\ninteraction is effectively disrupted. TAS shows that, after removal of the hydrogen bonding interaction,\nelectron transfer from the trapped states of SA-TCPP to PDA is effectively suppressed (Supplementary Fig.\n42b). These results demonstrate that the hydrogen bonding is necessary to achieve the ultrafast\ninterfacial electron transfer. The following discussion has been added to the Supplementary Page 51, “To\nclarify the role of hydrogen bonding, the PDA/SA-TCPP composite is thermally treated at 423.15 K for 2\n38\nh under an N₂ atmosphere to disrupt interfacial hydrogen bonds, as evidenced by FTIR analysis\n(Supplementary Fig. 42a). Transient absorption spectroscopy further reveals that, upon disruption of\nhydrogen bonding, electron transfer from the trapped states of SA-TCPP to PDA is markedly suppressed\n(Supplementary Fig. 43b), demonstrating that the hydrogen bonding is necessary to achieve the\nultrafast interfacial electron transfer.”\nSupplementary Figure 43. (a) FTIR spectra of PDA/SA-TCPP before and after thermal treatment at 423.15\nK for 2 h under an N₂ atmosphere, (b) TAS of PDA/SA-TCPP after hydrogen-bond disruption (pump\nwavelength: 660 nm).\n19. The figure resolution is insufficient. Higher-quality images should be provided.\nAnswer: Thanks for your suggestion. In the revised manuscript, all figures have been replaced with high-\nresolution versions to ensure clarity.\n20. Issues exist in reference formatting consistency and outdated citations. The authors should\nthoroughly check and update relevant literature.\nAnswer: Thanks for your comments. We have carefully checked all references to ensure consistent\nformatting. The outdated citations have been replaced by up-to-date studies published within the past\ntwo years to better reflect the current progress in this field.\nThe manuscript reports a PDA/SA-TCPP photocatalyst that achieves efficient H O production under NIR\n2 2\nirradiation, with a rate of 0.99 mM h-1 and an AQY of 2.8% at 1020 nm. Photocatalytic H O production\n2 2\nis a hot topic and a promising sustainable method for solar-to-chemical energy conversion, yet current\nprogress is limited by low NIR utilization. This work is therefore timely and significant. The loading of PDA\nwith persistent semiquinone radicals is demonstrated to enable ultrafast (∼79 fs) sub-gap electron\ntransfer from porphyrin trap states to PDA, overcoming the high recombination rates of NIR-excited\nelectrons. Moreover, SQ• radicals are reported to promote the formation of •OOH radicals, a rate-\nlimitation intermediate for H O production, extending the NIR response to 1020 nm. These findings\n2 2\nprovide a new strategy for efficient solar-to-chemical energy conversion and will interest researchers in\nthe field. Overall, the manuscript is well written and of high impact. I recommend acceptance in Nature\nCommunications after minor revisions to address the following comments.\n1. PDA itself has been used in photocatalytic H O production. Please provide more discussion of these\n2 2\nresults in the introduction to better clarify the novelty of this work. Moreover, to clearly delineate the\nindividual roles of SA-TCPP and PDA within the PDA/SA-TCPP composite for H O generation,\n2 2\nsupplementary characterization of PDA’s semiconductor properties—including its light absorption\ncharacteristics, energy band structure, and corresponding intrinsic photocatalytic H O production\n2 2\nperformance—should be provided.\nAnswer: We sincerely thank the reviewer for the constructive suggestion. We fully acknowledge that PDA\nhas been reported to possess intrinsic photocatalytic activity for H O generation. In the revised\n2 2\nmanuscript, we have incorporated a discussion in the Introduction (Page3, lines 5-10) to contextualize\nthe novelty and mechanistic distinction of the current work.\n“Although PDA has been employed to promote the photocatalytic H O production19, its use to\n2 2\nenhance NIR-driven H O generation remains rare, despite its broad solar-spectrum absorption.\n2 2\nMoreover, while radical-mediated fast electron transfer has been reported12, the utilization of the\npersistent semiquinone radicals intrinsically present in PDA to mediate the transfer of low-energy, NIR-\nexcited sub-bandgap electrons remains poorly understood.”\nAlso, as suggested, we have provided additional characterizations on the semiconductor properties\nof PDA in Supplementary Fig. 7, and the activity of PDA has been shown in Supplementary Fig. 12. The\nfollowing discussions have been added.\n40\n“Supplementary Fig. 7 shows the band structure of PDA. The UV-Vis-NIR absorption shows PDA\nstrongly absorbs across the solar spectrum. Tauc-plot and Mott-Schottky analyses determine the\nbandgap and Fermi level to be 1.14 eV and -0.47 eV, respectively. The conduction band is considered as\nca. 0.1 eV above the Fermi level13. Accordingly, the conduction and valence band edge potentials of PDA\nare determined as -0.36 V and 0.78 V vs. NHE, respectively.” (Supplementary Page 11)\n“At 298.15 K, negligible H O is detected with PDA under both λ > 420 nm and λ > 800 nm irradiation.\n2 2\nAt 353.15 K, negligible H O is still observed with the λ > 800 nm cutoff filter, whereas 0.29 mM H O\n2 2 2 2\naccumulates with PDA after 4 h under λ > 420 nm irradiation.” (Supplementary Page 17)\nSupplementary Figure 7. Intrinsic photocatalytic properties of PDA. (a) UV-VIS-NIR DRS spectrum, (b) the\nTauc-plot curves for bandgap determination, and (c) Mott–Schottky analysis. (d) Schematic illustration of\nthe energy band structure of PDA derived from (b) and (c).\n41\n0.4\nM l > 420 nm l > 800 nm\nm\n/\n0.3\nn\no\nti\na\nr\nn\nt0.2\ne\nc\nn\no\nc0.1\nN.D. N.D. N.D.\n0.0\n298.15 353.15 298.15 353.15\nSolution temperature / K\nSupplementary Figure 12. H O generation on PDA by under visible (λ>420 nm) and NIR (λ>800 nm)\n2 2\nirradiation.\n2. (1) The authors attribute the superior NIR performance to persistent SQ• radicals. Will these radicals\nbe consumed during reaction? In fact, SQ• radicals appear to act as intermediates between QH and\n2 2 2\ndefinitively distinguish whether the mechanism involves cycling between QH and Q or between SQ•\n2\nand Q. (2) Additionally, since PDA can be oxidized by O to produce H O even in the absence of light,\n2 2 2\nit is crucial to elucidate the precise mechanism underlying the performance enhancement attributed\nto PDA.\nAnswer: (1) Thanks for your comments. “EPR measurements performed after photocatalytic H O\n2 2\nproduction show that the SQ• signal intensity remains essentially unchanged, indicating that SQ• is\npersistent under the reaction conditions. (Supplementary Fig. 51c) This apparent stability originates from\na dynamic regeneration process, in which transient SQ• consumption during •OOH formation is\ncontinuously compensated by electron transfer from photoexcited SA-TCPP (Supplementary Fig. 52).”\n(Supplementary Page 61)\n2 2\nSupplementary Figure 52. Schematic illustrating the SQ• radical cycle during the H O production.\n2 2\nWe also note the reviewer-mentioned PDA/CdS system reported by Prof. Wei and Zhao (ACS Catal\n2022, 12, 11436), in which cycling between QH /Q accelerates O reduction to H O . We believe that the\n2 2 2 2\ndominant cycling pathway (QH /Q versus SQ•/Q) is mainly determined by interfacial charge-transfer\n2\nkinetics and reaction pH. In the reported PDA/CdS system, interfacial charge separation is not explicitly\ndemonstrated, and the achieved H O yield and SCC are approximately one order of magnitude lower\n2 2\n43\nthan those of our PDA/SA-TCPP system, suggesting substantially slower interfacial electron transfer\nthan in our case (ca. 79 fs). Such slow charge transfer likely leads to electron accumulation at the\ninterface, favoring two-electron reduction of Q to QH rather than one-electron reduction to SQ•,\n2\nconsistent with reports of multi-electron transfer pathways under electron-rich conditions. (B. Li, et al.,\nGreen Chem., 2025, 27, 13993)\nIn addition, proton availability is essential for the ORR toward H O . The PDA/CdS system mentioned\n2 2\nby the reviewer operates under neutral pH conditions, where semiquinone radicals (SQ•) are prone to\ndeprotonation to form SQ⁻• (SQ• ⇌ SQ⁻• + H⁺). (A. G. Stack, J. Colloid Inter. Sci. 2004, 274, 433) Because\nSQ⁻• does not contain a bound proton, although it retains an unpaired electron, it may be less active for\nreducing O to form H O than QH , which can directly provide protons for proton-coupled electron\n2 2 2 2\ntransfer because of the high pKa (9.1-9.4, R. Romero. et al., Front. Chem. 2018, 6, 208). In contrast, our\nsystem is operated at pH = 4 to prevent SA-TCPP dissolution, under which SQ• radicals remain\nprotonated and can directly participate in proton-coupled electron transfer during ORR. Moreover, the\nreported reaction rate of SQ• with O (106~108 M−1s⁻¹) is much higher than that of QH with O (2 × 102\n2 2 2\nM−1 s−1) (G. Buettner et al., Free. Radical. Biol. Med. 2010, 49, 919). Therefore, we propose that the SQ•/Q\nredox cycling constitutes the dominant and kinetically favored pathway for NIR-driven H O production\n2 2\nin our system.\n(2) We have also noted that dark H O generation on PDA via chemical pathways involving the oxidation\n2 2\nof catechol moieties to quinone by •O - attack, as reported by Liu et al. (e.g. Y. Liu, et al., Appl. Catal. B:\nunder neutral or alkaline conditions, while reports under acidic conditions are rare. This behavior can\nbe rationalized by the pH-dependent speciation of semiquinone radicals. To clarify the possibility of the\ndark H O generation under our acidic experimental conditions, we performed control experiments for\n2 2\nH O production by PDA in the dark at pH = 4 and pH = 10 at 353.15 K (Supplementary Fig. 28a). The\n2 2\nresults show that PDA-alone does not produce detectable H O under acidic conditions (pH = 4), whereas\n2 2\nmeasurable non-photocatalytic H O generation occurs only under neutral to alkaline conditions.\n2 2\nMoreover, in alkaline conditions, the H O production activity decreases dramatically in the 2nd run\n2 2\n44\n(Supplementary Fig. 28b), which is attributed to the irreversible oxidation of catechol to quinone in dark\nreaction. These results indicate that dark chemical H O production on PDA makes only a negligible\n2 2\ncontribution to the overall photocatalytic H O yield under our acidic experimental conditions.\n2 2\nThe following discussions have been added in the Supplementary Page 36. “To exclude the\npossibility of thermally driven H O generation on PDA in the dark, we evaluate the H O production on\n2 2 2 2\nPDA in the dark at pH = 4 and 353.15 K (Supplementary Fig. 28a). As a control, H O generation by PDA\n2 2\nin the dark at pH =1 0 and 353.15 K is also examined. The results show that under alkaline conditions,\ndark H O production on PDA is detectable and comparable to values reported in the literature57. In\n2 2\ncontrast, PDA produces negligible H O under acidic conditions (pH = 4) in the dark, indicating that\n2 2\nchemical H₂O₂ generation is insignificant under our experimental conditions. Furthermore, even at\npH=10, sustained H O production is not observed in the dark (Supplementary Fig. 28b), as the oxidation\n2 2\nof catechol to quinone is irreversible without photoinduced reduction, thereby terminating the redox\ncycle. These results confirm that the stable and continuous H O production observed for the PDA/SA-\n2 2\nTCPP system is barely attributed to dark chemical pathways.”\nSupplementary Figure 28. (a) Time-dependent H O generation on PDA in dark with different pH. (b) The\n2 2\ncyclic experiment of PDA was conducted under dark conditions with a solution pH of 10.\n45\n3. To better differentiate between purely photocatalytic and thermal effects, the authors should\nevaluate the activity of PDA, SA-TCPP, and PDA/SA-TCPP under two additional conditions: either under\nlight irradiation at 298 K or in darkness at 353 K, given that the photocatalytic tests were originally\nperformed at 353 K.\nAnswer: Following the reviewer’s suggestions, we differentiate between purely photocatalytic and\nthermal effects by evaluating the contribution of thermal catalytic effects to the overall observed\nphotothermal H O production. We further evaluated the contribution of thermal catalytic effects to the\n2 2\nobserved photothermal H O production. Thermal effects may influence several processes, including (i)\n2 2\nhole transfer in SA-TCPP, as clarified in Supplementary Figure 32 and in our previous study (C. Pan. et\nal., Nat. Energy 2023, 8, 361); (ii) dark H O production at elevated temperature, which is shown in\n2 2\nSupplementary Fig. 29; and (iii) the ORR pathway, which is shown in Supplementary Fig. 31.\nSupplementary Fig. 29 shows the dark H₂O₂ production on PDA, SA-TCPP, and PDA/SA-TCPP at\nelevated temperature (353.15 K). For PDA, dark H O generation via chemical pathways has been\n2 2\nreported (Y. Liu, et al., App. Catal. B: Environ. 2025, 364, 124863). However, we also note that such\nreactions are predominantly observed under neutral or alkaline conditions, while reports under acidic\nconditions are rare. To clarify the possibility of the dark H\n2\ngeneration under our acidic experimental\nconditions, we have performed control experiments for H O production by PDA in the dark at pH = 4 at\n2 2\n353.15 K (Supplementary Fig. 28a). The results show that PDA-alone does not produce detectable H O\n2 2\nunder acidic conditions (pH = 4).\nFor SA-TCPP, Supplementary Fig. 29 confirms that no H O is produced in the dark, consistent with\n2 2\nour previous report. Similarly, the PDA/SA-TCPP composite exhibits negligible H O formation under\n2 2\ndark conditions, demonstrating that dark chemical reactions do not contribute substantially to the\nobserved H O production in this system.\n2 2\nFurthermore, Supplementary Fig. 31 compares H₂O₂ production on PDA/SA-TCPP at 298.15 K and\n353.15 K using isopropanol (IPA) as a hole scavenger, thereby isolating the influence of thermal effects\non ORR-driven H O formation. Only a modest enhancement (1.2-fold) is observed at 353.15 K relative\n2 2\nto 298.15 K, indicating that while elevated temperature can slightly facilitate ORR kinetics, it is not the\nprimary contributor to the overall enhancement in H O production.\n2 2\nBy excluding both the thermal contribution to dark H₂O₂ production and the possibility that\naccelerated electron transfer alone accounts for the observed activity enhancement, we conclude that\nthe dominant role of thermal effects in the PDA/SA-TCPP system is to promote hole-related processes,\nfacilitating the hydrolysis of hole-oxidized peroxy acid intermediates into H O , consistent with our\n2 2\nprevious findings in the SA-TCPP-only system.\nThe following discussions have been added in Supplementary Page 39, “As shown in Supplementary\nFigure S32 and S33, PDA markedly enhances the photothermal conversion efficiency. To decouple the\nphotothermal contribution to H O production, control experiments are performed. Thermal effects may\n2 2\ninfluence H₂O₂ production via dark H₂O₂ formation, ORR acceleration, or hole transfer. However,\nnegligible H₂O₂ generation is observed for PDA, SA-TCPP, and PDA/SA-TCPP in the dark at 353.15 K and\npH=4, excluding thermal-driven H O production. (Supplementary Fig.29) Using IPA as a hole scavenger,\n2 2\nonly a modest ca. 1.2-fold enhancement in H O production is observed at 353.15 K compared to 298.15\n2 2\nK, indicating that ORR acceleration is not the dominant factor. (Supplementary Fig. 31) Therefore, by\nexcluding the above two possibilities, thermal effects may primarily accelerate the hydrolysis of hole-\noxidized peroxy acid intermediates, consistent with the results in Supplementary Fig. 32 and our previous\nobservations for the SA-TCPP-alone system, while H O production is dominated by the photocatalytic\n2 2\nprocess and the associated photogenerated charge separation.”\n1.0\nM PDA/SA-TCPP\nm SA-TCPP\n0.8 PDA\n/\nn\no\ni\na\nt0.6\nr\nt\nn\ne\nc0.4\nn\no\nc\n20.2\nO\n0.0\n0 1 2 3 4\nIrradiation time / h\n2 2\ndark conditions at 353.15 K. Reaction conditions: Sln., 50 mL H O; Light source, 300 W Xe lamp with a\n2\n420 nm cut-off filter; Photocatalyst concentration, 4.0 g/L.\nm\n/\nn\no 4\ni\nt\na\nr\nt\nn\ne\nc\nn 2\no\nc\n0\n298.15 353.15\nSolution temperature / K\nSupplementary Figure 31. Photocatalytic H O production on PDA/SA-TCPP within 1 h reaction at 298.15\n2 2\nK and 353.15 K in the presence of IPA as a hole scavenger. Reaction conditions: Sln., 50 mL H O; Light\n2\nsource, 300 W Xe lamp with a 420 nm cut-off filter; Photocatalyst concentration, 4.0 g/L.\n4. The reported AQY values under NIR are impressive, but only calculated AQY data are provided in the\nSI. Please include the corresponding activity data and specify the light intensity used for each AQY\nmeasurements.\nAnswer: We sincerely thank the reviewer for the valuable comments. In response, we have\nsupplemented the manuscript with detailed experimental data related to the apparent quantum yield\n(AQY) measurements. The following discussions have been added on the Supplementary Page 33: “The\ncorresponding H O generation rates for AQY measurements at each NIR wavelength have been\n2 2\npresented in Supplementary Fig. 26. During all AQY measurements, an Xe lamp is set over the reaction\nsolution with a constant distance of 4.0 cm and the corresponding bandpass filters are used to obtain\nmonochromatic light. The incident light intensities are determined and calibrated using a power meter.\n(OHSP-350 UV, Perfect Light, Beijing, China) The measured light intensity is as follows: 46.3 W/m² at 850\nnm, 95.4 W/m² at 940 nm, 135.8 W/m² at 1020 nm.”\n2 2\n(a) 850 nm, (b) 940 nm, and (c) 1020 nm.\n5. Given the promise of PDA with persistent SQ• radicals on the utilization of trap electrons, have the\nauthors tested such materials in other photocatalytic systems to verify the general applicability of this\nstrategy?\nAnswer: We thank the reviewer for the valuable comments. In the revised manuscript, we have\nprovided additional experimental data to demonstrate the applicability of the PDA-assisted catalytic\n36\nstrategy across a range of inorganic and organic NIR-responsive materials, including Bi CoO , black\n12 20\nTiO2, Zn-TCPP, and CoPc. Because PDA mainly promotes the ORR pathway, while the WOR side may limit\noverall H O generation, the universality of the NIR-enhancement strategy may not be evident in systems\n2 2\n49\nwhere hole transfer is inefficient. To address this issue and enable a fair comparison across different\nphotocatalysts, IPA is introduced as a sacrificial reagent in selected systems, allowing the generality of\nthe PDA-assisted NIR enhancement to be more reliably evaluated. The detailed results are shown below.\n“Four NIR-adsorption materials, including Bi CoO (prepared according to the method reported\n12 20\npreviously by our group, C. Pan, et al., J. Catal. 2023, 428, 115172), black TiO (B-TiO , prepared according\n2 2\nto the reported method, L. Li. et al. Nat. Energy. 2022, 7, 1042), commercial zinc porphyrin (Zn-TCPP, 95%,\npurchased from Beijing InnoChem Science & Technology Co, Ltd, China), and commercial\n(Tetracarboxyphthalocyaninato) cobalt (II) (CoPc, 95%, purchased from Xi'an Qiyue Biotechnology Co.,\nLtd, China), are selected and individually coupled with PDA to construct PDA/Bi CoO , PDA/B-TiO₂,\n12 20\nPDA/CoPc, and PDA/Zn-TCPP composites.\nAs shown in Supplementary Fig. 53a-d, the UV-Vis-NIR DRS spectra indicate that Bi CoO , B-TiO₂,\n12 20\nZn-TCPP, and CoPc all exhibit NIR absorption in the 800-1200 nm region. The H O generation rates of\n2 2\nthese systems under NIR irradiation (λ > 800 nm) with and without PDA loading are compared in\nSupplementary Fig. 53e. The results reveal that PDA loading significantly enhances H O production, with\n2 2\nthe H O yield of PDA/Bi CoO , PDA/B-TiO₂, PDA/CoPc, and PDA/Zn-TCPP increasing by 5.0, 2.5, 5.4,\n2 2 12 20\nand 7.8-fold, respectively, relative to the counterparts without PDA loading. These results demonstrate\nthat the PDA loading can efficiently promote the NIR-driven ORR to H O .” (Supplementary Page 64)\n2 2\n12 20 2\nComparison of H O generation rates under NIR irradiation (λ > 800 nm) for Bi CoO , B-TiO₂, CoPc, and\n2 2 12 20\nZn-TCPP, and their PDA-loaded composites. Reaction conditions: Cat., 4.0 g/L , Sln., 50 mL H O (or 10 vol%\nReviewer #3\nThis study presents a composite photocatalyst comprising polydopamine (PDA) nanoparticles supported\non self-assembled TCPP supramolecular nanosheets (SA-TCPP) for near-infrared (NIR)-driven H O\n2 2\nphotosynthesis from H O and O . The authors attribute the enhanced activity to the role of persistent\n2 2\nsemiquinone radicals (SQ•) in PDA, which mediate ultrafast sub-gap electron transfer (~79 fs) from SA-\nTCPP to PDA, thereby promoting the formation of •OOH intermediates. While the experimental data are\ncomprehensive and generally support the conclusions, the work lacks mechanistic depth in several critical\nareas, and the catalyst design itself does not represent a significant conceptual advance. As such, the\nreviewer does not recommend publication in Nature Communications:\nAnswer: Thanks for the comments. Although NIR utilization is crucial for solar-driven H O\n2 2\nphotosynthesis, only limited strategies to enhance the NIR utilization have been explored: (i) up-\nconversion of NIR photons into higher energy levels (J. Kim, et al., Energy Environ. Sci., 2016, 9, 1063); (ii)\n51\ndirect utilization of NIR-excited band-edge electrons (B. Lotsch, et al., Nat. Synth. 2025, 4, 710); and (iii)\ncharge transitions via intermediate band states (Wang et al., Nat. Commun. 2024, 15, 9505). Despite\nprogress, these approaches are intrinsically limited by kinetic energy loss during up-conversion,\ninsufficient driven force of low-energy band-edge electrons, and strong localization of intermediate band\nstates, which together hinder further improvement in NIR-driven H O photosynthesis.\n2 2\nHere, we propose a distinct strategy based on persistent organic radicals. Unlike previously reported\nC-centered or H• radicals that require UV/visible excitation, the semiquinone (SQ•) radicals in PDA are\nintrinsically stable and well matched to low-energy NIR photons. Their unpaired electrons act as\nefficient electron acceptors, enabling ultrafast interfacial electron extraction from NIR-responsive SA-\nTCPP, promoting charge separation and facilitating O activation.\nnow provide systematic control experiments that directly demonstrate the ultrafast interfacial charge\ntransfer originating from persistent radicals, quantitative evaluation of thermal contributions, in-situ\nspectroscopic identification of •OOH-to-H O conversion, and interfacial DFT calculations linking the\n2 2\nelectron transfer to SQ•-related electronic states (Supplementary Figures 20-21,29,31,38-39,43,50-52).\nOverall, we believe these new results together with the existed data substantially deepen the\nmechanistic understanding and demonstrate a conceptual advance by revealing a previously\nunderexplored persistent radical-mediated pathway for NIR-driven photocatalysis beyond conventional\nband-engineering strategies. The detailed responses to the reviewer’s questions are listed below.\n1. Stability and Dynamics of SQ• Radicals: Although the cyclic experiments have shown good stability,\nthe chemical persistence and regeneration efficiency of the SQ• radicals under prolonged illumination\nremain unquantified. To firmly establish the role of SQ• as a durable electron mediator, quantitative\nEPR analysis of the radical concentration before and after extended reaction cycles is essential.\nAnswer: Thanks for your valuable comment. As suggested, we have performed quantitative EPR\nanalysis to determine the concentrations of persistent SQ• radicals before and after extended reaction\ncycles(Figure 5b). The details are shown below:\n“Commercial TEMPO is used as an external standard to determine the concentrations of persistent\nChemCatChem. 2024, 16, e202401042). In the first step, a series of reference TEMPO samples with\nknown spin concentrations is prepared. Then, EPR spectra of these standards are recorded under the\nsame measurement conditions as those used for the tested samples, including identical modulation\nfrequency (100.00 KH), power (3.17 mW), modulation amplitude (3.000 G), temperature (295.00 K), and\nsweep time (30.00 s) (Supplementary Fig. 51a,b). After that, each spectrum is baseline-corrected and\nsubjected to double integration, yielding the integrated intensity proportional to the spin number. Finally,\nbased on these results, a calibration curve correlating the integrated area with spin concentration is\nestablished, which exhibits excellent linearity (R2=0.999) within the working range. The fitted slope and\nintercept are used for subsequent calculations of the concentrations of persistent SQ• radicals, while the\ncorrelation coefficient is provided to assess linearity and measurement reliability.\nOn the other hand, for the PDA/SA-TCPP samples, identical measurement procedures are applied\nto record the EPR spectra before and after extended photocatalytic cycles. The spectra are processed and\ndouble-integrated following the same protocol. Using the established calibration curve, the integrated\nintensities are converted into radical concentrations (Supplementary Fig. 51 c,d). The calculated radical\nconcentrations before and after prolonged illumination are 6.33×1013 spin/μg and 6.18×1013 spin/μg ,\ncat cat\nrespectively, indicating a negligible change in the SQ• radical concentration before and after extended\nreaction cycles (Figure 5b). ” (Supplementary Page 61)\n“This apparent stability originates from a dynamic regeneration process, in which transient SQ•\nconsumption during •OOH formation is continuously compensated by electron transfer from\nphotoexcited SA-TCPP (Supplementary Fig. 52).” (Supplementary Page 63)\nsamples recorded under identical measurement conditions with SQ•. The inset is the molecular structure\nof TEMPO. (b) Linear relationship between the double-integrated EPR signal area and spin number for\nTEMPO. (c) EPR spectra of the PDA/SA-TCPP sample before and after 10 cycle reaction. (d) Comparison\nof SQ• radical concentrations before and after 10 reaction cycles, calculated using the calibration curve.\nSupplementary Figure S52. Schematic illustrating the SQ• radical cycle during the H O production.\n2 2\n2. Interface Characterization: The evidence for hydrogen bonding between PDA and SA-TCPP,\n54\nbased solely on FTIR peak shifts, is indirect. More direct characterization techniques, such as solid-state\nNMR or high-resolution XPS, are needed to conclusively identify and quantify the nature and strength of\nthese interfacial interactions.\nAnswer: Thank you for this valuable comment. In the original manuscript, hydrogen bonding is indirectly\nevidenced by the FTIR peak shifts of C=O and C-O groups, because the characteristic OH and COOH\nstretching region (3000-4000 cm⁻¹) overlaps with N-H vibrations, making direct identification difficult.\nIn the revised manuscript, we have prepared deuterium-substituted SA-TCPP, PDA, and PDA/SA-TCPP,\nin which the OD and COOD stretching vibrations are free from N-H interference, and their peak shifts\nprovide direct evidence for hydrogen-bond formation. In addition, as suggested by the reviewer, solid-\nstate 13C NMR and high-resolution XPS analyses have been performed to further support the existence\nof hydrogen bonding.\nThe following discussions have been added to Supplementary Page 25-26:\n“To obtain the direct evidence of hydrogen bonding between OH groups in PDA and COOH groups in\nSA-TCPP from FTIR and avoid the N-H interference, we have prepared deuterium-substituted SA-TCPP (D-\nSA-TCPP), PDA (D-PDA), and PDA/SA-TCPP (D-PDA/SA-TCPP) and measured the FTIR of the deuterium-\nsubstituted samples (Supplementary Fig. 20). The deuterium-substituted samples are prepared by first\ndissolving the original materials in a NaOH/D O solution and subsequently, precipitated by deuterated\n2\nhydrochloric acid solution (DCl + D O). After D-substitution, the FTIR spectra of D-SA-TCPP, D-PDA, and\nwith that in literature30, confirming the success of deuterium-substitution. In SA-TCPP, the characteristic\nstretching vibration of COO-D appears as two distinct bands at 2630 and 2524 cm⁻¹, due to the vibrational\nmode splitting31. In contrast, the O-D stretching vibration in PDA exhibits a single characteristic band at\n2639 cm⁻¹. In D-PDA/SA-TCPP, the stretching vibration peaks emerges at around 2667 cm-1 and 2544 cm-\n1, the shift of which directly confirms the existence of hydrogen bonding between OH groups in PDA and\nCOOH groups in SA-TCPP.”\n“Supplementary Fig. 21a presents the O 1s XPS spectra of SA-TCPP, PDA, and PDA/SA-TCPP. The O\n1s spectrum of SA-TCPP can be deconvoluted into three components located at 532.1 eV (C=O ),\n(COOH)\n533.9 eV (C–O ), and 535.6 eV (surface-OH). Similarly, the O 1s spectrum of PDA is resolved into\n(COOH)\n55\nthree peaks at 531.5 eV (C=O), 533.2 eV (C–O), and 535.6 eV (surface-OH), as reported11,32. Upon\nformation of the PDA/SA-TCPP composite, the binding energies of the C=O and C=O shift toward\n(COOH) (PDA)\nhigher values, while the binding energies of the C-O and C-O shift toward lower values,\n(COOH) (PDA)\ncompared with those of pristine SA-TCPP and PDA, indicating C=O is the H acceptor and C-OH is the H\ndonor in the hydrogen-bonding and confirming the hydrogen-bonding interactions between PDA and SA-\nTCPP33. Supplementary Fig. 21c shows the solid-state 13C NMR spectra of SA-TCPP, PDA, and PDA/SA-\nTCPP and their magnification. The detailed assignment of 13C NMR spectra of SA-TCPP is well consistent\nwith the reported one, as labelled in the inset, while that of PDA is shown in Supplementary Fig. 3. In\nPDA/SA-TCPP, the C peak associated with C=O (160-180 ppm) shifts to a lower chemical shift compared\nto SA-TCPP and PDA, confirming the presence of hydrogen bonding, as previously reported34. Moreover,\nthe peaks corresponding to the C=O groups in the PDA/SA-TCPP composite are significantly narrower\nthan those in SA-TCPP and PDA, which may also result from hydrogen bond formation between PDA and\nSA-TCPP, thereby restricting the free rotation of σ bonds, consistent with earlier observations35.”\nWe also attempted to obtain the solid-state 1H NMR spectrum of SA-TCPP, PDA, and PDA/SA-TCPP,\nas shown in the following Figure I (reviewer only). However, due to the strong 1H-1H dipolar couplings,\nthe peaks are broadened, barely giving the information of H-bonding, and only spin sidebands are\nobserved.\n2524\n2630\nu . 2667 2544\n.\na\n/\nn\no\nsi 2638\ns\nmi\ns\nn\na\nr\nT\nSA-TCPP\nPDA/SA-TCPP\nPDA\n40003500300025002000\nWavenumber / cm-1\nSupplementary Figure S20. isotope-labeled FTIR of PDA, SA-TCPP, and PDA/SA-TCPP.\nand PDA/SA-TCPP.\nSA-TCPP\nPDA/SA-TCPP\nPDA\n.\nu\n.\na\n/\ny\nt\ni\ns\nn\ne\nt\nn\nI\n80 60 40 20 0 −20 −40 −60 −80\n1H chemical shift / ppm\nFigure I (Reviewer only). Solid-state MAS 1H NMR spectra of PDA, SA-TCPP, and PDA/SA-TCPP.\n3. Reaction Mechanism Completeness: The study clearly demonstrates NIR-induced •OOH formation\non PDA. However, the subsequent critical step—how the •OOH intermediate is reduced to H₂O₂ via\nsynergy with SA-TCPP—is not elucidated. Identifying whether this step is limited by electron transfer,\nintermediate desorption, or another factor is crucial for rational optimization.\nAnswer: Thanks for the comments. In principle, the reduction potential for •OOH to H O is\n2 2\n57\napproximately 1.0 V (vs. NHE), which is well below the conduction band edges of most photocatalysts.\nIn contrast, the formation of •OOH from O requires a much more negative potential (ca. 0.3 V), which is\n2\ncloser to the conduction band edge of typical photocatalysts. From a thermodynamic perspective, the\ninitial formation of •OOH may be more difficult to accept electrons from the photocatalyst than the\nsubsequent reduction of •OOH to H O . For this reason, the original manuscript primarily focused on the\n2 2\ngeneration of •OOH rather than its further reduction.\nAs suggested by the reviewer, we have now provided additional experimental evidence to clarify\nthe subsequent conversion of •OOH in the revised manuscript. In situ FTIR, in situ Raman spectroscopy,\nand EPR measurements of PDA/SA-TCPP under NIR irradiation have been conducted (Supplementary\nFigs. 48,50). Based on these results, a complete reaction scheme for O reduction to H O via •OOH\n2 2 2\nintermediates on PDA is proposed (response to Reviewer’s Question 1 and Supplementary Fig. 52).\n“Distinct from the PDA-alone system, in which in situ FTIR spectra show only •OOH-related features\neven after 30 min of NIR irradiation, the PDA/SA-TCPP composite exhibits two additional IR bands at 1434\ncm⁻¹ and 1285 cm⁻¹ that emerge after 10 min of irradiation. These bands can be assigned to adsorbed\nH O and C-OOH species, respectively, indicating that •OOH is further reduced to H O through bound\n2 2 2 2\non the PDA surface, forming C-OOH intermediates. The formation of C-OOH intermediates is also\ncorroborated by in-situ Raman spectroscopy, where corresponding vibrational features are observed68-\n70. Notably, the peaks associated with •OOH reduction appear concurrently with those related to •OOH\nformation, suggesting that once •OOH is generated, its further conversion to H O proceeds readily via\n2 2\nthe C-OOH pathway (TS3-1, Figure 1c). These results indicate that the reduction of •OOH kinetically\nproceeds efficiently relative to •OOH formation.”(Supplementary Page 60)\n(λ > 800 nm).\nWe have also conducted EPR measurements on the PDA/SA-TCPP system under anoxic conditions\n(N₂ bubbling) and in air, together with quantitative H O analysis to study the further reduction of •OOH.\n2 2\n“Under N bubbling, EPR spectra reveal a pronounced accumulation of SQ• radicals, which contribute\n2\napproximately 55% to the overall EPR signal, accompanied by the production of 0.42 mM H O\n2 2\n(Supplementary Fig. 48a,b). In contrast, when the reaction is performed in air, the EPR signal associated\nwith SQ• decreases dramatically, with its contribution dropping to ca. 21%, while the amount of\ngenerated H O increases by approximately sevenfold (Supplementary Fig. 48c,d). Notably, at the same\n2 2\ntime, the contribution of •OOH to the overall EPR spectra increases substantially from 45% to 79%. The\ninverse correlation between SQ• intensity and H O yield provides strong evidence that SQ• radicals are\n2 2\nactively consumed during NIR-driven H O formation via generating •OOH. These results also indicate\n2 2\nthat even under anoxic conditions, where •OOH formation is strongly suppressed, the small amount\nof •OOH generated can still be efficiently reduced to H O . In air, substantial •OOH accumulation\n2 2\noccurs and its subsequent reduction to H O proceeds rapidly, while a fraction of SQ• remains\n2 2\nunconverted. Together, these observations demonstrate that, in this system, the reduction of •OOH to\nH O is kinetically more facile than the initial formation of •OOH.”( Supplementary Page 60)\n2 2\n2 2\non PDA/SA-TCPP under NIR irradiation with N bubbling, (c) and (d) EPR spectra and the corresponding\n2\nphotocatalytic H O production on PDA/SA-TCPP under NIR irradiation with air bubbling. The fitting\n2 2\nparameters are the same as that in Fig. 1d.\n4. Ultrafast Electron Transfer Pathway: While fs-TAS data indicate an interfacial electron transfer\nprocess, the specific pathway and electronic coupling mechanism for sub-gap electron injection from\nSA-TCPP trap states to PDA's SQ•/quinone moieties remain unclear. A more detailed theoretical\nanalysis (e.g., electronic structure calculations of the interface) would strengthen this central claim.\nAnswer: Thanks for your suggestion. In the revised manuscript, the interfacial electronic structure is\ninvestigated by density functional theory calculations, and the structural model is shown in\nSupplementary Fig. 43. Because the electronic properties of PDA are the primary focus, a PDA oligomer\nconsisting of nine units containing both saturated and unsaturated indole rings is employed. In contrast,\nas the structure of TCPP is well established in the literature, a single TCPP molecule is introduced to form\nhydrogen bonds with the SQ• moieties of PDA. The following discussion is added on Supplementary Page\n53.\n60\n“The entire PDA/SA-TCPP interfacial structure is fully optimized using DMol3 with the B3LYP\nexchange-correlation functional. Geometry optimization is performed with convergence criteria of 5 ×\n10-4 Ha/atom for total energy, 0.02 Ha/Å for maximum force, and 0.05 Å for maximum ionic displacement.”\nBader charge analysis is carried out on the optimized structure (Supplementary Table 6), and the\nnet charge transfer between PDA and SA-TCPP is summarized in the inset of Supplementary Fig. 43a. The\nresults reveal a charge transfer of approximately 0.14 e from PDA to SA-TCPP upon interfacial formation,\nrendering PDA positively charged and thereby facilitating the acceptance of photogenerated electrons\nfrom SA-TCPP. Electron density difference maps (Supplementary Fig. 43b) further show pronounced\nelectron accumulation at the hydrogen-bonding regions, confirming that the interfacial electron transfer\noccurs through hydrogen bonding.\nIn addition, the total and partial density of states (TDOS and PDOS) are calculated for the PDA/SA-TCPP\nsystem (Supplementary Fig. 43c-d). The results indicate that the PDA-derived electronic states are located\njust below the LUMO of TCPP, favoring interfacial electron transfer. PDOS analysis shows that these PDA\nstates mainly originate from the O 2p and C 2p orbitals of the SQ• moieties, with negligible contribution\nfrom N 2p orbitals. This observation confirms that the interfacial electronic states arise from the unpaired\nelectrons of the SQ• moieties, which are delocalized over O and C atoms due to resonance.”\nthe net charge transfer between the SQ• moiety and TCPP calculated from the Bader charge. (b) Electron\ndensity difference map, where yellow and cyan regions indicate electron accumulation and depletion,\nrespectively. (isosurface value: 0.04) (c) TDOS of the SQ• moiety of PDA and TCPP in the PDA/SA-TCPP\nmodel, (d) PDOS of PDA in PDA/TCPP, and PDOS of TCPP in PDA/TCPP.\nSupplementary Table 6. Atomic Bader charge analysis of the SQ• moiety and TCPP in PDA/SA-TCPP.\nNo. Atom Charge / e No. Atom Charge / e No. Atom Charge /e No. Atom Charge / e\n62\n5. Energy Level Diagram Clarification: For a more intuitive comparison, the energy level diagram in\nFigure 4d should include the calculated absolute energy values (in eV) of the relevant PDA orbitals (e.g.,\nLUMO, LUMO) alongside the trap state levels of SA-TCPP.\nAnswer: Thanks for your comments. As suggested, the absolute energy values (in eV) of the orbitals of\nPDA and SA-TCPP relevant to TAS spectra in Figure 4d are calculated by Gaussian 09. The corresponding\nenergy diagram to Figure 4d shown absolute energy values is in Supplementary Fig. 39.\nfrom TAS. aDFT calculations are carried out using the Gaussian 09 software package. Geometry\noptimization of the individual TCPP and PDA molecules is performed using the B3LYP functional and the\n6-31G(d,p) basis set. Single-point energy calculations are performed using the CAM-B3LYP functional and\nthe 6-311G(d,p) basis set. The energy level of excited states is calculated by TD-DFT with cam-b3lyp/6-\n311G(d,p). The energy level of ground states is calculated by DFT with b3lyp/6-311G(d,p). bThe\nexperimental transition data is converted from the observed TAS transition wavelength (λ) by the\nequation (ΔE = hc/λ = 1240 eV/ λ, h is the plank constant and c is the light speed). cThe theoretical trap-\nstate energy level is estimated by assuming the ratio match with the experimentally determined values.\nIn particular, the ratio between the observed transition differences (i.e. the difference between the\nenergy of the S (TCPP) → T transition and the S (TCPP) → trap transition relative to the difference\n0 1 0\nbetween the energy of the S (PDA) → trap transition and the S (PDA) → LUMO+2 transition) is set to\n0 0\nequal the corresponding theoretical transition differences.\n6. Benchmarking Context: In Supplementary Table S2, the photocatalytic performance of reference\nmaterials should be compared under standardized conditions. Annotations specifying the light source\ncharacteristics (wavelength range, intensity) for each benchmarked catalyst would ensure a fair and\naccurate comparison.\nAnswer: We thank the reviewer for the valuable suggestion. In the revised Supplementary Table S2, we\nhave added detailed information on the light sources used for each reference catalyst, including the\nwavelength range and light intensity, as suggested. We note that the reported studies employ\n64\nsubstantially different illumination conditions, particularly in the light intensity. As a result, a direct\ncomparison of H O production rates across different reports may be not accurate, which is consistent\n2 2\nwith the reviewer’s concern regarding standardized conditions. Accordingly, we delete the original\nsentence “Notably, PDA/SA-TCPP demonstrates the highest H O production rate and accumulation,\n2 2\nsurpassing typical H O -generation photocatalysts such as COFs, C N , and resins by more than\n2 2 3 4\ntwofold”.\nNotably, the AQY and SCC are generally evaluated under standardized illumination conditions, making\nthem more reliable for cross-study comparison. We have thus corrected the corresponding sentences in\nthe revised manuscript to: “Notably, PDA/SA-TCPP achieves a high H₂O₂ production rate, placing it among\nthe top-performing photocatalytic systems reported to date (Supplementary Table S2)” (Page 12, Lines\n1-3). “the average AQY of PDA/SA-TCPP is 22.3% at 420 nm (Supplementary Fig. 22), which is 1.9 times\nhigher than that of SA-TCPP and surpasses most reported values for H2O generation from H O and O\n2 2 2\n(Supplementary Table S2)” (Page 12, Lines 15-18). “This value is nearly twice that of pristine SA-TCPP and\nexceeds most reported photocatalysts (Supplementary Table S2)” (Page 21, Lines 1-2)\nSupplementary Table 2. H₂O₂-generation performance of representative photocatalysts.\nLight H2O2 H2O2\nCat. Light AQY at ηscc\nNo Photocatalyst intensity generation accum. Ref.\n(g/L) Source 420 nm (AM 1.5G)\n(mW/cm2) rate (µM/h) (mM)\n(λ ≥ 420nm) (24 h) 22.3% 2.10%\nwork\nAM 1.5G 100 1070 -\n(λ ≥ 420nm) (24 h)\n(AM 1.5G) (60 h)\nRF/P3HT Oriel Solar 10.7\n4 1.7 210 400 8.7% 1.00% 36\nresins Simulator 94123A (50 h)\n(300-1100 nm)\nSimulator 94123A (24 h)\n7 g-C3N4/ PDI/rGO 1.7 100 360 6.1% 0.20% 42\n(AM 1.5G) (48 h)\n(λ ≥ 420 nm) (24 h)\nPCX-50B 43.8\n(λ >420 nm) (96 h)\n(λ ≥ 420 nm) (48 h)\n(λ ≥ 420 nm) (24 h)\n(AM 1.5G) (3 h)\n(AM 1.5G) (8 h)\n(λ > 420 nm) (4 h)\n(λ > 420 nm) (1 h)\n(λ > 420 nm) (1 h)\n(λ > 420 nm) (72 h)\n(λ > 420 nm)\nwhite LED 4.09\n(400-700 nm) (6 h)\n7. Mechanistic Discrimination: To robustly distinguish an electron transfer mechanism from potential\nenergy transfer processes, time-resolved photoluminescence (TRPL) spectroscopy comparing the\nexcited-state lifetimes of SA-TCPP and PDA/SA-TCPP would provide complementary evidence.\nphotoluminescence (TRPL) measurements of SA-TCPP and PDA/SA-TCPP, and the excited-state\nlifetimes were extracted using three-exponential decay fitting. The following discussions have been\nadded in the revised manuscript (Page 18, Lines 1-2): “The TRPL results further confirm that the\nacceleration of charge separation after PDA loading.”\nThe specific details are as follows: “The time-resolved photoluminescence (TRPL) measurements of\nSA-TCPP and PDA/SA-TCPP are performed (Supplementary Fig. 38), and the excited-state lifetimes are\nextracted using three-exponential decay fitting (Supplementary Table 5). The shortest component (τ )\nCS\ncorresponds to the charge separation (exciton dissociation) process. The middle lifetime component (τ )\nCT\ncorresponds to the charge-transfer (CT) process, and the longest lifetime component (τ ) is associated\nCR\nwith charge recombination process50. τ is close to the lifetime of the polar separation obtained from\nCS\nthe TAS spectra. In our case, quantitative fitting reveals that τ decreases from 0.98 ns for pristine SA-\ncs\nTCPP to 0.09 ns for PDA/SA-TCPP, confirming that polarization separation and interfacial charge transfer\nare markedly accelerated at the interface between PDA and SA-TCPP.\nBesides that, the average fluorescence lifetime of pure SA-TCPP is τ = 5.81 ns, whereas in the\navg\nPDA/SA-TCPP composite, the lifetime significantly increases to τ = 16.24 ns. The longer average lifetime\navg\nof PDA/SA-TCPP indicates that once the polar is spatially separated into photo-excited electrons and\nholes at the interface between PDA and SA-TCPP, they may exist more longer time relative to those in SA-\nTCPP that easily recombine in the bulk.” (Supplementary Page 48)\nSupplementary Figure 38. PL decay spectra of PDA/SA-TCPP and SA-TCPP.\nSample τ /ns τ /ns τ /ns B /% B /% B /% τ /ns\nCS CT CR 1 2 3 avg\nSA-TCPP 0.98 2.80 10.41 59.01 1.09 39.87 5.81\nPDA/SA-TCPP 0.09 6.22 25.13 46.32 0.39 53.26 16.24\n8. Photothermal Contribution: The significant photothermal effect of PDA is noted, but its quantitative\ncontribution to the overall H₂O₂ production rate, distinct from the photochemical electron transfer\npathway, is not delineated. Controlled experiments under isothermal conditions are needed to\ndeconvolute these effects.\nAnswer: Thanks for your valuable suggestion. Following the reviewer’s suggestions, we differentiate\nbetween purely photocatalytic and thermal effects by evaluating the contribution of thermal catalytic\neffects to the overall observed photothermal H O production. Thermal effects may influence several\n2 2\nprocesses, including (i) hole transfer in SA-TCPP, as clarified in Supplementary Fig. 32 and in our previous\nstudy (Nat. Energy 2023, 8, 361); (ii) dark H O production at elevated temperature (353.15 K), as is\n2 2\nshown in Supplementary Fig. 29 and (iii) the ORR pathway, which is shown in Supplementary Fig. 31.\nSupplementary Fig. 39 shows the dark H₂O₂ production on PDA, SA-TCPP, and PDA/SA-TCPP at\nelevated temperature (353.15 K). For PDA, dark H O generation via chemical pathways has been\n2 2\nreported (Y. Liu, et al., App. Catal. B: Environ. 2025, 364, 124863). However, we also note that such\nreactions are predominantly observed under neutral or alkaline conditions, while reports under acidic\nconditions are rare. Under alkaline conditions, the generated •O\n2\n- is less likely to react with the\nnegatively charged semiquinone radical anion (SQ•-) because of electrostatic repulsion, favoring its\nfurther reduction. In contrast, under acidic conditions, the concentration of electron-rich SQ•- is low (pKₐ\nof SQ• = 4.88). Consequently, once the •OOH species formed, in the dark, they can readily react with\nneutral SQ•, leading to back reactions that regenerate O . To clarify the possibility of the dark H O\n2 2 2\ngeneration under our acidic experimental conditions, we have performed control experiments for H O\n2 2\nproduction by PDA in the dark at pH = 4 at 353.15 K (Supplementary Fig. 28a). The results show that PDA-\nalone does not produce detectable H\n2\nunder acidic conditions (pH = 4).\n2 2\nour previous report. Similarly, the PDA/SA-TCPP composite exhibits negligible H O formation under\n2 2\ndark conditions, demonstrating that dark chemical reactions do not contribute substantially to the\nobserved H O production in this system.\n2 2\nFurthermore, Supplementary Fig. 31 compares H₂O₂ production on PDA/SA-TCPP at 298.15 K and\n353.15 K using isopropanol (IPA) as a hole scavenger, thereby isolating the influence of thermal effects\non ORR-driven H O formation. Only a modest enhancement (1.2-fold) is observed at 353.15 K relative\n2 2\nto 298.15 K, indicating that while elevated temperature can slightly facilitate ORR kinetics, it is not the\nprimary contributor to the overall enhancement in H O production.\n2 2\nBy excluding both the thermal contribution to dark H₂O₂ production and the possibility that\naccelerated electron transfer alone accounts for the observed activity enhancement, we conclude that\nthe dominant role of thermal effects in the PDA/SA-TCPP system is to promote hole-related processes,\nfacilitating the hydrolysis of hole-oxidized peroxy acid intermediates into H O , consistent with our\n2 2\nprevious findings in the SA-TCPP-only system.\nThe following discussions have been added in Supplementary Page 39: “As shown in Supplementary\nFigure S32 and S33, PDA markedly enhances the photothermal conversion efficiency. To decouple the\nphotothermal contribution to H O production, control experiments are performed. Thermal effects may\n2 2\ninfluence H₂O₂ production via dark H₂O₂ formation, ORR acceleration, or hole transfer. However,\nnegligible H₂O₂ generation is observed for PDA, SA-TCPP, and PDA/SA-TCPP in the dark at 353.15 K and\npH=4, excluding thermal-driven H O production. (Supplementary Fig. 29) Using IPA as a hole scavenger,\n2 2\nonly a modest ca. 1.2-fold enhancement in H O production is observed at 353.15 K compared to 298.15\n2 2\nK, indicating that ORR acceleration is not the dominant factor. (Supplementary Fig. 31) Therefore, by\nexcluding the above two possibilities, thermal effects may primarily accelerate the hydrolysis of hole-\noxidized peroxy acid intermediates, consistent with the results in Supplementary Figure 32 and our\nprevious observations for the SA-TCPP-alone system, while H O production is dominated by the\n2 2\nphotocatalytic process and the associated photogenerated charge separation.”\n69\n1.0\nM PDA/SA-TCPP\nm SA-TCPP\n/ 0.8 PDA\nn\no\ni\na\nt0.6\nr\nt\nn\ne\nc0.4\nn\no\nc\n20.2\nO\n0.0\n0 1 2 3 4\nIrradiation time / h\nSupplementary Figure 29. Photocatalytic H O production on PDA, SA-TCPP, and PDA/SA-TCPP under\n2 2\ndark conditions at 353.15 K. Reaction conditions: Sln., 50 mL H O (pH = 4); Light source, 300 W Xe lamp\n2\nwith a 420 nm cut-off filter; Photocatalyst concentration, 4.0 g/L.\nm\n/\nn\no 4\ni\nt\na\nr\nt\nn\ne\nc\nn 2\no\nc\n0\n298.15 353.15\nSolution temperature / K\nSupplementary Figure 31. Photocatalytic H O production on PDA/SA-TCPP within 1 h reaction at 298.15\n2 2\nK and 353.15 K in the presence of IPA as a hole scavenger. Reaction conditions: Sln., 50 mL H O; Light\n2\nsource, 300 W Xe lamp with a 420 nm cut-off filter; Photocatalyst concentration, 4.0 g/L.\n9. Scalability and Practical Viability: The pathway toward practical application is not addressed.\nQuestions regarding the scalability of catalyst synthesis, the feasibility of fabricating stable catalytic\nfilms or membranes, and the design of flow reactors for continuous H₂O₂ production—along with a\n70\npreliminary techno-economic assessment—should be discussed to evaluate real-world potential.\nAnswer: We sincerely thank the reviewer for the valuable suggestion. In the revised manuscript,\nwe have supplemented relevant analyses, including the scalability of catalyst synthesis, the feasibility of\nfabricating stable catalytic films or membranes, and the design of flow reactors for continuous H₂O₂\nproduction, along with a preliminary techno-economic assessment.\nThe scalability of catalyst synthesis: First, the reactants used for preparing SA-TCPP are derived from\ncommercially available bulk TCPP, while PDA is synthesized from commercially available dopamine\nhydrochloride. The other chemicals involved in the preparation of PDA/SA-TCPP are common acids and\nbases. Therefore, all required chemicals are readily accessible and do not pose limitations for large-scale\nproduction. Second, the preparation process relies on simple mixing and pH adjustment, which are easy\nto control and manipulate. All reactions are conducted at room temperature without the need for a\nspecial gas atmosphere. Finally, the synthesis can be completed using only basic laboratory equipment,\nsuch as beakers and magnetic stirrers, which can be readily scaled up, highlighting the practical feasibility\nof large-scale catalyst preparation. In the revised manuscript, the following comments have been added\n“The PDA/SA-TCPP are prepared from commercially available chemicals, easily manipulated methods,\nand common laboratory equipment, indicating good potential for scale-up preparation.” (on page 25,\nline 26-28)\nThe feasibility of fabricating stable catalytic films or membranes: we have presented the\nperformance of the PDA/SA-TCPP film cast onto the Petri dish in Figure 5. The film can be easily obtained.\nThe following comments have been added in the revised manuscript: “The PDA/SA-TCPP powder is\nultrasonically dispersed in ethanol, and the resulting suspension is poured into the Petri dish and dried\nat room temperature to obtain a film. The film exhibits good adhesion to the Petri dish substrate and\ndoesn’t peel off during the outdoor tests.” (on Page 21, line 12-13)\nNote that at present, the film system shows much lower activity than the suspended powder due\nto the increase in irradiation area and catalyst amount in the film is not proportional to that in the\npowder., resulting in an outdoor SCC of 0.12% for the film compared with 2.12% for the powder in the\n71\nlaboratory. Despite this reduction, the obtained SCC remains relatively high among reported supported\nsystems (Supplementary Table 9) and may serve as a starting point for further practical optimization.\nIn fact, in a recent study, we immobilized SA-TCPP onto quartz wool and achieved an activity comparable\nto that of the suspended powder system (Figure II (reviewer only), C. Pan, et al., Quartz wool-supported\nporphyrin supramolecular photocatalysts for robust and scalable H O generation, EES Sol., 2025, 1,\n2 2\n1115). Inspired by this result, future work will focus on immobilizing PDA/SA-TCPP onto porous supports\nsuch as quartz wool to reduce the current SCC gap between powder and immobilized configurations.\nFigureII. (Reviewer only) Comparison of the H O yields between SA-TCPP powder and NH -PDMS/SA-\n2 2 2\nTCPP/Quartz Wool (QW) composite at 353.15 K. (Insets) Photographs showing the SA-TCPP powder (left)\nand the immobilized NH -PDMS/SA-TCPP/QW composite (right)\nlab-made flow and evaporation device for concentrated H O production, achieving a H O\n2 2 2 2\naccumulation concentration of 1.6 wt% within 10 hours. In Figure 5d, we have also presented a\ncontinuous flow reactor system and the use of in-situ produced H O for organic pollutants degradation,\n2 2\nwhere the concentration of in-situ produced H O reaches a stable level of 2.1 mM during the reaction\n2 2\nat the flow speed of 2 ml/min. Within 12 min, nearly 95% of representative pollutants, including\nmethylene blue (MB) dye and ciprofloxacin (CIP) antibiotic are removed, corresponding to a degradation\nrate of 0.23 min-1 and 0.21 min-1, respectively. (Supplementary Fig. 60) These results demonstrate the\neffectiveness of the continuous H O -producing system for pollutant removal and water purification.\n2 2\n2 2\nis used as a representative pollutant. The outlet pipe transferring the generated H O to the MB solution\n2 2\nis covered with a semi-permeable membrane to prevent PDA/SA-TCPP powder from entering the MB\nsolution. The inset shows the MB solution after degradation.\nSupplementary Figure 60. (a) The degradation curves of CIP and MB via Fenton reaction with the H O\n2 2\nin-situ produced in the PDA/SA-TCPP system. (b) The corresponding degradation rates of the CIP and MB.\n2 2\nproduction system is performed by separating the costs into capital expenditure (Capex) and operating\nexpenditure (Opex). The details are shown in Supplementary Note 1.\nAll costs are initially calculated in CNY and converted to USD using an exchange rate of 1 USD= 6.98\nCNY (Jan., 2026).\nCapital expenditure (Capex)\nThe capex mainly includes a 300 W Xe lamp ($1376.87), a quartz reactor ($0.55), a pump ($5.23),\nand others (i.e., connection pipe: $0.14 in total):\nC = C +C +C +C = $1382.79 Eq. S8\nCapex reactor lamp pump others\nOperating expenditure (Opex)\nThe operating expenditure consists of raw material costs (C ), running costs (C ), and labor\nOpex, 1 Opex, 2\ncosts (C ).\nOpex(labor)\nThe raw material costs include TCPP ($5.73 g-1) and PDA ($0.31×10-3 g-1):\nC = $5.73 g−1 ×0.050 g (m )×1.1/2.1(𝓌 %) = $0.15 Eq. S9\nOpex(TCPP) cat TCPP\nC = $0.31×10−3 g−1 ×0.05 g (m )× 1.0 (𝓌 %) = $0.74×10−5 Eq. S10\nOpex(PDA) cat PDA\n2.1\nC = C +C = $0.15 Eq. S11\nOpex,1 Opex(TCPP) Opex(PDA)\nThe running costs include electricity ($0.06 kWh-1, 300 W), O ($2.75/40 L, 99.90%, 150 atm), and\n2\nultrapure water ($0.14 L-1):\nC = $0.06 KWh−1 ×0.3 KW (Power of Xe lamp)×1 h = $0.018 Eq. S12\nOpex(electricity)\nL min\n0.05 (Gas flow rate)×60 ×1 h×1 atm (Reaction pressure)\nC = $2.75× min h = $0.138×10−2 Eq.\nOpex(O2)\nS13\nC = $0.14 L−1 ×2.0 mL min−1(Liquid flow rate)× 1 L ×60 min ×1 h = $0.017\nOpex(H2O)\n1000 mL h\nEq. S14\nC = C +C +C = $0.036 Eq. S15\nOpex,2 Opex(electricity) Opex(O2) Opex(H2O)\nC = 15%×(C +C ) = $0.028 Eq. S16\nOpex(labor) Opex,1 Opex,2\nThus, the total operating expenditure for 1 h operation is:\nC\nOpex\n= C\nOpex,1\n+C\nOpex,2\n+C\nOpex(labor)\n= $0.21 Eq. S17\nwhere the O flow rate is the 50 mL/min, the H O flow velocity is 2.0 mL/min, and the running time is\n2 2\n1 h.\nCost of H O production\n2 2\nConsidering only the operating expenditure, the mass of H O produced in 1 h is calculated from a\n2 2\nformation rate of 2.0 mM h-1:\nmM mL\nm = 2.0 (H O production rate)×2.0 (Liquid flow rate)×60 min×\nH2O\n2, 1 h h\n2 2\nmin\ng\n34.01 (m ) = 0.008 g/h Eq. S18\nmol\nH2O2\nAccordingly, the production cost of H O for 1 h operation is:\n2 2\nC = Copex = $0.21 = $26.25 g−1 Eq. S19\nH2O\n2, 1 h mH2O2 0.008 g\nUnder continuous operation for 10 h, the production cost of H O is:\n2 2\nC\nOpex\n= C\nOpex,1\n+10×C\nOpex,2\n+15%×(C\nOpex,1\n+10×C\nOpex,2\n) = $0.59 Eq. S20\nC = Copex = $0.59 = $7.38 g−1 Eq. S21\nH2O\n2, 10 h 10×mH2O2 0.08 g\nIf the system is operated continuously for 100 h, the production cost of H O is:\n2 2\nC = Copex = $4.31 = $5.39 g−1 Eq. S22\nH2O\n2, 100 h 100×mH2O2 0.8 g\nIf solar energy is used instead of the Xe lamp as the light source, the electricity cost can be excluded.\nC = Copex−C Opex(electricity) = $2.24 = $2.80 g−1 Eq. S23\nH2O2, 100 h, solar\n100×mH2O2 0.8 g\nAccording to the above calculations, the operating expenditure of H O production in the continuous-\n2 2\nflow system decreases markedly with prolonged operation. Specifically, the production cost of H O is\n2 2\nreduced from $26.25 g-1 after 1 h of operation to $7.38 g-1 and $5.39 g-1 upon continuous operation for\n10 and 100 h, respectively. When the Xe lamp is replaced by solar irradiation, the electricity-related costs,\ntogether with the associated labor cost, can be excluded, further decreasing the H O production cost to\n2 2\n$2.80 g-1 after 100 h of continuous operation. These results indicate that the continuous-flow reactor\nenables sustained H O production at low operating costs, highlighting its economic feasibility. Notably,\n2 2\nthis cost is lower than that of commercial-grade H O , which typically ranges from 0.2 to 7.0 US dollars\n2 2\ng⁻¹ depending on grade (H O , price, Sigma-Aldrich, https://www.sigmaaldrich.com/US/en/product/\n2 2\nsial/18304, (accessed Jan 06, 2026).\nReviewer #4\nThis manuscript precisely analyzes the near-infrared (NIR)-driven hydrogen peroxide production\nmechanism using a PDA/SA-TCPP composite, demonstrating enhanced electron transfer pathways and\ncatalytic performance. To overcome the sub-gap of SA-TCPP, PDA was synthesized, and the reason why\nthe composite photocatalyst is driven by photogenerated electron transfer in the NIR was analyzed\nthrough various experiments, including fs-TA. Several questions remain to be addressed to further\nelucidate the NIR-driven mechanism of PDA/SA-TCPP.\n1. It is necessary to compare and analyze the contribution of WOR and ORR to the photocatalytic H O\n2 2\nproduction in the NIR of PDA/SA-TCPP. Scavenger experiments or atmosphere-controlled experiments\nare required.\nAnswer: Thanks for your suggestion. In the revised manuscript, we have added scavenger experiments\nto clarify the NIR-driven H O production from WOR and ORR pathways. In general, the addition of a\n2 2\nsacrificial reagent often promotes the H O production rate relative to that in water because of the\n2 2\nacceleration of surface charge capture. (P. Pachfule. et al. Nat. Commun. 205, 16, 503) In our case, to\nminimize the surface charge capture, we choose the sacrificial reagents with close surface charge\ncapture capability to O and COOH groups (WOR active sites in SA-TCPP as we have determined before).\n3\nsacrificial reagent, where the reduction potential is 0.59 V (NO - to HNO ) and close to 0.68 V (O to\n3 2 2\nH O ). “Supplementary Fig. 33 shows the H O production with HCOOH and NO -, respectively, as hole\n2 2 2 2 3\nand electron scavengers under NIR irradiation. The H O production rate with HCOOH decreases to 0.61\n2 2\nmM/h, approximately 61% relative to that without HCOOH, suggesting that ORR contributes substantially\n76\nto the overall NIR-driven H₂O₂ production. In contrast, with La(NO ) and Ar bubbling, the H₂O₂\n3 3\nproduction rate drops to 0.51 mM/h, nearly half of the overall production rate, suggesting WOR\ncontributes similarly to ORR to H O production.” (Supplementary Page 41)\n2 2\nh 1.5\n/ O atmosphere Ar atmosphere\nM 2\nm\n/\ne\nt 1.0\na\nr\nn\no\ni\nt\nc\nu\nd 0.5\no\nr\np\nControl HCOOH La(NO )\n3 3\nSupplementary Figure 33. Sacrificial reagent experiment of PDA/SA-TCPP under NIR irradiation.\n(Reaction conditions: Sln., 50.0 mL H O; Cat., 4.0 g/L; Temp, 353.15 K controlled by an oil bath; Light\n2\nsource, 300 W Xe lamp with an 800 nm cut-off filter. The solution pH is adjusted with nitric acid when\nLa(NO ) is employed as the electron scavenger. (The IPA content was 10 vol%, and the concentration of\n3 3\nLa(NO ) was 0.01 mM)\n3 3\n2. To further isolate the contribution of the photothermal effect of PDA/SA-TCPP, it is necessary to\nanalyze the H O production under light irradiation while maintaining the same temperature.\n2 2\nAnswer: Thanks for your suggestion. As suggested, the data showing intrinsic activity of PDA/SA-TCPP\nin Supplementary Figures 22 and 62 are replaced with the activity data while maintaining the same\ntemperature (353.15 K). The activity data (Fig. 24, 35) showing the potential of practical use remains.\nThe details are shown below:\n77\n4\nh\n/\nM\nm\n3\n/\nn\no\nt i 2.1 times\na 2\nr\ne\nn\ne\ng\n1\n0\n1.5 2 3 4 5\nPhotocatalyst concentration / g/L\nSupplementary Figure 22. H O generation on PDA/SA-TCPP at different photocatalyst concentrations.\n2 2\nReaction conditions: Sln., 50.0 mL H O; Solution temperature, 353K; Light source, 300 W Xe lamp\n2\nequipped with a 420 nm cut-off filter.\nSupplementary Figure 62. (a) Time-dependent H O production curves for x-PDA/SA-TCPP\n2 2\nphotocatalysts. x is denoted as the mass ratio between PDA and SA-TCPP, (b) H O accumulation after 4\n2 2\nh irradiation. Reaction condition: Sln., 50.0 mL H O, Cat., 4.0 g/L, Solution temperature, 353K; 300 W Xe\n2\nlamp with a 420 nm cut-off filter.\nTo further clarify thermal contributions under irradiation, Supplementary Fig. 12 compares H O\n2 2\nproduction on PDA alone at 298.15 K and 353.15 K using λ > 420 nm and λ > 800 nm cutoff filters. SA-\nTCPP is not evaluated together with PDA in this control experiment because the thermal contribution in\nthe SA-TCPP-alone system has been previously investigated. (C. Pan et al., Nat. Energy 2023, 8, 361) In\nthat system, although thermal effect does not directly initiate H O formation, photogenerated holes\n2 2\nlead to the formation of TCPP-COOOH intermediates, and thermal effect accelerates the hydrolysis of\nperoxy acid groups to yield H O while regenerating TCPP. Here, to specifically probe direct H O\n2 2 2 2\nproduction induced by thermal effects, we focus on PDA alone, thereby excluding the possibility that\nthermal effect enhances hole-induced H O generation from SA-TCPP under irradiation. The reaction pH\n2 2\nis maintained at 4 to ensure consistency with the PDA/SA-TCPP system.\nAt 298.15 K, negligible H O is detected with PDA under both λ > 420 nm and λ > 800 nm irradiation.\n2 2\nAt 353.15 K, negligible H O is still observed with the λ > 800 nm cutoff filter, whereas 0.29 mM H O\n2 2 2 2\naccumulates with PDA after 4 h under λ > 420 nm irradiation. Considering that 11.24 mM H O is\n2 2\nproduced in the PDA/SA-TCPP system under identical conditions (Figure 3a of the original manuscript),\nthe maximum contribution of thermal effects of PDA to the overall H O production is estimated to be\n2 2\nless than 3%.\nAccording to the above results, in the PDA/SA-TCPP system, the thermal effect plays only a minor\nrole and cannot account for the high and sustained H O production observed in the PDA/SA-TCPP system.\n2 2\nIn particular, the thermal effect will barely contribute to the H O production under NIR light irradiation.\n2 2\nInstead, its role is manifested in promoting the thermal decomposition of peroxy acid intermediates\nformed via the oxidation of carboxyl groups by photogenerated holes as we have reported in the SA-\nTCPP-alone system.\n79\n0.4\nM l > 420 nm l > 800 nm\nm\n/\n0.3\nn\no\ni\nt\na\nr\nn\nt0.2\ne\nc\nn\no\nc0.1\nN.D. N.D. N.D.\n0.0\n298.15 353.15 298.15 353.15\nSolution temperature / K\nSupplementary Figure 12. Control experiments conducted under dark and illuminated conditions at\ndifferent temperatures (298.15 K and 353.15 K) for PDA.\n3. Although this manuscript presents an analysis of photoexcited electron transport, a systematic\nanalysis of hole transport between SA-TCPP and PDA is lacking. This needs to be supplemented to\ndemonstrate the contribution of the WOR pathway to H O production under NIR irradiation.\n2 2\nAnswer: Thanks for your suggestion. In the revised manuscript, we have performed in-situ Kelvin probe\nforce microscopy (KPFM) measurements in the dark and under light irradiation to monitor the hole\ntransfer in the PDA/SA-TCPP composite (Supplementary Fig. 34). In addition, we provide a systematic\ncomparison of 13C NMR, 1H NMR, FTIR, and TOF-MS data results for SA-TCPP and PDA/SA-TCPP\nobtained under NIR irradiation and after reaction at room temperature. The comparison is conducted\nto verify whether the WOR pathway in the PDA/SA-TCPP system is identical to that previously\nestablished for the SA-TCPP-only system in our earlier work.\n“The KPFM results show that, before illumination, the contact potential difference (CPD) of SA-TCPP\nis -350 mV. Upon NIR irradiation, the CPD of SA-TCPP increases by 50 mV, indicating the accumulation of\n80\nphotogenerated holes on the SA-TCPP nanosheets after the electron transfer to PDA.” (Supplementary\nPage 42)\nSupplementary Figure 34. KPFM characterization of the PDA/SA-TCPP composite before and after NIR\nirradiation. (a-b) KPFM images and (c-d) the corresponding surface potential.\nIn the SA-TCPP alone system (C. Pan, et al., Nat. Energy 2023, 8, 361), we have demonstrated hole\noxidation reactions in which the carboxyl group on SA-TCPP is initially oxidized into a peroxy acid\nintermediate (-COOH + 2h+ + H O → -CO H + 2H+). Subsequently, -CO H undergoes thermal hydrolysis\n2 3 3\nto regenerate the -COOH to form H O (-CO H + H O → -COOH + H O ).\n2 2 3 3 2 2\nIn our present work for PDA/SA-TCPP, TAS results (Figure 4) show electron transfer from SA-TCPP\nto PDA, implying that photogenerated holes remain on SA-TCPP. To probe their role, we have added\ncomparative 13C NMR, 1H NMR, TOF-MS, and FTIR analyses of PDA/SA-TCPP and SA-TCPP after reaction\nin the revised manuscript. SA-TCPP in the composite is selectively dissolved in DMSO to avoid PDA\ninterference, and measurements are conducted at 298.15 K to allow peroxy acid accumulation. The\nfollowing discussions have been added.\n“The NIR photocatalytic activity enhancement mechanism for PDA/SA-TCPP is studied next. In the\nPDA/SA-TCPP system, the peroxy acid intermediate, similar to that in SA-TCPP, is still observed under\n81\nirradiation (Supplementary Fig. 32), excluding hole transfer from SA-TCPP to PDA, which indicates that\nholes remain on SA-TCPP.” (Page 15, lines 2 to 6, main text)\n“Supplementary Fig. X compares the formation of the peroxy acid intermediate between PDA/SA-\nTCPP and SA-TCPP-alone after the reaction at 298.15 K. Supplementary Fig. Xa, b present the\ncorresponding 13C and 1H NMR spectra of the SA-TCPP and PDA/SA-TCPP photocatalyst after the reaction.\nAfter the reaction, distinct 13C NMR resonances attributed to SA-TCPP-COOOH appear at 167.1, 141.3,\n129.9, 129.5, and 119.4 ppm, together with characteristic 1H NMR signals at 12.8 ppm, 8.2-7.8 ppm, and\n7.0-6.8 ppm, confirming the formation of the COOOH groups.\nSupplementary Fig. Xc shows the FTIR spectra of PDA/SA-TCPP and SA-TCPP-alone recorded after\nthe reaction. Two absorption bands at 1633 cm⁻¹ and 1275 cm⁻¹ emerge for PDA/SA-TCPP, belonging to\nthe stretching vibrations of C=O and the bending of O-H in COOOH group, respectively, which is consistent\nwith those observed in the SA-TCPP-only system.\nSupplementary Fig. xd displays the TOF-MS of PDA/SA-TCPP and SA-TCPP-alone acquired after the\nreaction. After the reaction, peaks at 807, 808, 809, and 810 are observed for both samples. The mass\nincrement of 16 relative to SA-TCPP (m/z peaks at 791, 792, 793, and 794) indicates the incorporation of\n16O atom into the -COOH moiety, confirming the formation of the -COOOH intermediate, in agreement\nwith our previous reports. These results collectively indicate that in the PDA/SA-TCPP system, the holes\nremain on the SA-TCPP to oxidize the carboxyl groups and form the -CO H group, and subsequently, -\n3 2 2\neffect observed in the system using SA-TCPP alone.” (Supplementary Page 39)\n2 2\non PDA/SA-TCPP photocatalyst and SA-TCPP-alone after reaction at room temperature (298.15 K). To\nexclude 13C NMR, 1H NMR, and TOF-MS interference from PDA, SA-TCPP in the PDA/SA-TCPP composite\nis selectively dissolved using DMSO and subsequently used for further comparison.\n4. Current analyses of electron transfer are indirect. Direct data, such as in-situ XPS analysis, are\nneeded to confirm electron transfer between SA-TCPP and PDA.\nAnswer: Thanks for your comments. In-situ XPS has been provided in Supplementary Fig. 36. The detailed\ndescription is as follows: Supplementary Fig. 36 shows the in-situ XPS narrow-scan spectra of C 1s and O\n1s for the PDA/SA-TCPP composite recorded in the dark and under light irradiation. The C 1s spectrum\nexhibits a series of peaks including sp3 C (284.8 eV), sp2 C (285.4 eV), O-C (286.3 eV), C-N (287.1 eV), O=C\n83\n(289.0 eV), and O=C-O peaks (291.0 eV) (Z. Jin, et al., Langmuir 2015, 31, 11671; G. Huang, et al., Appl\nOrganometal Chem. 2018, 32, e4140). Upon the light irradiation, the O=C-O peak exhibits a positive shift\nof 0.3 eV, whereas the O-C peak exhibits a negative shift of 0.2 eV. Considering that the O=C-O signal\noriginates exclusively from the COOH group of SA-TCPP, while the O-C signal is solely associated with the\nC(sp2)-OH group of PDA, the opposite binding-energy shifts indicate distinct electronic responses of the\ntwo components. As reported (J. Yu, et al., Nat. Commun. 2024, 15, 9612), the positive XPS shift suggests\nelectron depletion, and the negative shift implies electron accumulation. Therefore, the observed shift\nindicates the electron transfer from SA-TCPP to PDA under light irradiation. For the O 1s spectrum, the\nO=C , O=C , C-O , C-O , and surface-OH peaks are located in 531.7, 532.3, 533.1, 533.7,\n(PDA) (COOH) (PDA) (COOH)\nand 535.6 eV in the dark. Upon light irradiation, the O 1s signal associated with the COOH group exhibits\na positive binding-energy shift, whereas that corresponding to the C(sp²)–OH group shifts negatively.\nThese opposite shifts are consistent with the trend observed in the C 1s spectra, suggesting the\nphotoinduced electron transfer from SA-TCPP to PDA.” (Supplementary Page 44)\nSupplementary Figure X. In-situ XPS spectra of PDA/SA-TCPP before and under light irradiation. (a) XPS\nC 1s and (b) XPS O 1s spectra.\n84\n[Review on Nature Communications – NCOMMS-25-71751]\nNear-IR H O Photosynthesis through Rapid Sub-Gap Electron Transfer Mediated by\n2 2\nPersistent Semiquinone Radicals\nThis manuscript precisely analyzes the near-infrared (NIR)-driven hydrogen peroxide\nproduction mechanism using a PDA/SA-TCPP composite, demonstrating enhanced electron\ntransfer pathways and catalytic performance. To overcome the sub-gap of SA-TCPP, PDA was\nsynthesized, and the reason why the composite photocatalyst is driven by photogenerated\nelectron transfer in the NIR was analyzed through various experiments, including fs-TA.\nSeveral questions remain to be addressed to further elucidate the NIR-driven mechanism of\nPDA/SA-TCPP.\nRecommendation: Minor\n1. It is necessary to compare and analyze the contribution of WOR and ORR to the\nphotocatalytic H O production in the NIR of PDA/SA-TCPP. Scavenger experiments\n2 2\nor atmosphere-controlled experiments are required.\n2. To further isolate the contribution of the photothermal effect of PDA/SA-TCPP, it is\nnecessary to analyze the H O production under light irradiation while maintaining the\n2 2\nsame temperature.\n3. Although this manuscript presents an analysis of photoexcited electron transport, a\nsystematic analysis of hole transport between SA-TCPP and PDA is lacking. This\nneeds to be supplemented to demonstrate the contribution of the WOR pathway to\nH O production under NIR irradiation.\n2 2\n4. Current analyses of electron transfer are indirect. Direct data, such as in-situ XPS\nanalysis, are needed to confirm electron transfer between SA-TCPP and PDA."}, {"round": 2, "reviewer_comments": {"reviewer_1": "In this revised manuscript, authors have completely addressed my concerns and doubts. The current version can be accepted in Nature Communications without further editions.", "reviewer_2": "this work has been revised well and it can be accepted as it is", "reviewer_3": "The reviewer is satisfied with the authors' revision and recommends accepting this revised manuscript for publication.", "reviewer_4": "The authors tried to address the comments. It's moderately persuasive and the reviewer approves of it."}, "author_response": ""}]

Decision letter