Spatiotemporal photon distribution control on active sites enables bio-inspired methane-to-methanol conversion

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

Abstract
Direct catalytic conversion of methane to methanol offers a pathway for transforming a potent greenhouse gas into a portable clean liquid fuel, thereby mitigating carbon emissions and supporting sustainable energy. However, this process faces challenges from thermodynamically favorable methanol overoxidation. Here, we show that spatiotemporal regulation of photogenerated charge carriers on engineered catalytic sites enables a bio-inspired ordered two-step photocatalytic process that imitates methane monooxygenase. In a platinum-loaded cadmium sulfide photocatalyst, unsaturated sulfur sites modulate hole migration while platinum sites modulate electron migration, ensuring their concurrent surface arrival within picoseconds and prolonged localization. This dynamics temporarily anchors methane at hole-enriched sulfur sites while hydroxyl radical generation occurs at electron-rich platinum sites, decoupling hydroxyl radical formation from methane dehydrogenation to suppress overoxidation. The approach achieves methane-to-methanol conversion with selectivity of 83.5%, offering a bio-inspired solar-driven strategy for C1 valorization.

Introduction
The depletion of crude oil reserve has driven catalytic methane conversion into value-added chemicals as a sustainable alternative to petroleum-based processes. Conventional approaches for producing syngas or hydrocarbons require high temperatures (600-1100°C), facing three key limitations: catalyst sintering, poor selectivity, and high energy demands1-3. These challenges have intensified researches into mild-condition methane (CH4) oxidation to methanol (CH3OH), which is regarded as a strategic C1 oxygenate-offering energy-efficient production of liquid platform chemicals2,4-7. Photocatalytic direct conversion of CH4 to CH3OH achieves efficient C-H bond activation under mild conditions, utilizing light-driven charge transfer to selectively oxidize methane at tailored catalytic sites. However, thermodynamic limitations inherently drive CH4 molecules toward overoxidation pathways, predominantly yielding fully oxidized carbon dioxide (CO2) as the terminal product8. This fundamental challenge necessitates the development of advanced catalytic architectures with precisely engineered active sites to kinetically steer CH4 activation trajectories toward partial oxidation while suppressing deep oxidation processes.

In recent works, simulating the active center of methane monooxygenase (MMO) for catalysts designs have made progress in modulating CH4 to CH3OH9-15. Not just the precisely constructing biomimetic active sites over photocatalysts, we are also inspired with the sequence of crucial steps, which requires the additional focus on temporal modulations. It is noted that enzymatic process occurs in two sequential steps, which is as illustrated in Fig. 1a. Firstly, electron and molecular oxygen (O2) are coordinated on active site to generate the reactive oxygen species (ROS). After that, CH4 is captured and one of the hydrogen atoms is abstracted by ROS (CH4 dehydrogenation), forming a methyl radical intermediate that subsequently yields CH3OH. Such a strictly ordered process is conceptualized in photocatalysis like: simulating the enzymatic oxygen activation process through light-induced electron transfer that combines with O2 to generate ROS; then replicating the enzymatic hydrogen extraction via ROS-mediated C-H bond dissociation in CH4 to form CH3OH.

However, translating these blueprints into functional photocatalytic platforms confronts substantial implementation barriers. This limitation stems from fundamental differences in reaction sequences between biological and artificial catalytic systems. In enzymatic catalysis mediated by MMO, CH4 adsorption strictly occurs after oxygen activation process, ensuring one hydrogen abstraction process that prevents overoxidation. Conversely, it is common that engineered photocatalysts employ photoinduced-electron-enriched active centers to facilitate efficient O2-to-ROS conversion (O2 + e- → ∙O2-, ∙O2- + H+ → ∙OOH, ∙OOH + H+ + e- → ∙OH)16-18. But it is possible that these active sites simultaneously adsorb both O2 and CH4 molecules during illumination. This concurrent adsorption creates two reaction pathways of ROS-mediated hydrogen abstraction from CH4 and direct electron transfer attacks on adsorbed CH4. The parallel activation mechanisms lead to non-selective extraction of multiple hydrogen atoms, promoting the generation of overoxidation products of CO2 rather than controlled single-step oxidation to CH3OH. This fundamental mismatch in reaction choreography highlights the critical need for spatially/temporally decoupled active sites in artificial photocatalytic systems to replicate the precision of enzymatic catalysis.

To address these challenges, we propose a kinetic modulation strategy through spatiotemporal charge separation engineering on catalyst surfaces. Our conceptual framework (Fig. 1b) involves constructing an active site rich in photogenerated electron adjacent to the original active site that rich in photogenerated hole. By utilizing this hole-rich site to preferentially capture CH4 molecules under light illumination, thereby delaying the adsorption process of CH4 toward active site rich in photogenerated electron. However, implementation faces fundamental kinetic barriers due to the disparate charge carrier dynamics - photogenerated electron typically migrates faster than hole in conventional semiconductors19-21. This temporal mismatch disrupts the desired reaction sequence, allowing premature CH4 adsorption at electron-rich sites rather than at hole-rich sites. Therefore, to realize this concept, it is necessary to develop effective strategies enabling photogenerated electron and hole to migrate to adjacent active sites within the same timescale.

Herein, we carried out investigations based on typical cadmium sulfide (CdS) to achieve the similar trapping of photogenerated electron and hole on ultrafast timescale. Specifically, the migration of hole to the surface is accelerated by utilizing unsaturated sulfur (~10.6 ps)22, addressing the issue of slow hole migration due to their large effective mass. Subsequently, platinum (Pt)23,24 enables the migration of electron to the surface within ~3.3 ps, achieving a temporal match between electron and hole migration. Then, the Pt-S bond forms independent localized sites for electron and hole, spatially separating them. As a result, electron-rich and hole-rich sites can stably exist over a longer timescale, allowing CH4 and O2 to interact with hole and electron, respectively, which significantly enhances the activity and selectivity of CH3OH production.

Results
Photocatalyst preparation
Based on a typical hydrothermal method (Supplementary Fig. 1a and Supplementary Fig. 2), unsaturated-sulfur-rich cadmium sulfide (CdS) is prepared as substrate, and platinum (Pt) is loaded using impregnation method (1%Pt/CdS and 2%Pt/CdS). X-ray diffraction (XRD) pattern and high-resolution transmission electron microscopy (HRTEM) are indicative of the successful preparation of CdS substrate. The primary diffraction peaks at around 24.9°, 26.5° and 28.2° in XRD (Supplementary Fig. 1b) can be indexed to (100), (002) and (101) of hexagonal CdS (PDF#65-3414), which are relatively sharp and narrow. The measurable lattice fringes in HRTEM (Supplementary Fig. 3b) includes typical (100) and (011) of CdS. Selected area electron diffraction (SAED) images (Supplementary Fig. 3c) demonstrate the polycrystalline property of substrate materials, where the obvious diffraction rings all correspond to hexagonal CdS crystal. Moreover, TEM reflects a typical particle shape of as-prepared CdS and the average size is less than 100 nm (Supplementary Fig. 3a). This result is consistent with the crystal average thickness deduced from Scherrer Formula (Supplementary Table 1). After Pt impregnation, a negligible impact on the crystal structure and micro-morphology of substrates can be noticed. XRD and TEM of 1%Pt/CdS and 2%Pt/CdS are basically same with CdS (Supplementary Fig. 3d-i). Furthermore, the electronic state and coordination environment is validated through X-ray photo electron spectroscopy (XPS) and X-ray absorption fine spectroscopy (XAFS). In XPS Cd 3d fine spectra of CdS (Supplementary Fig. 4a), the doublet peaks (3d5/2 at 404.7 eV, 3d3/2 at 411.5 eV) are ascribed to Cd2+ in crystal20. As to S 2p fine spectra (Supplementary Fig. 5a), the dominating signals (2p3/2 at ~161.1 eV, 2p1/2 at ~162.3 eV) originate from lattice S2-, while the minor ones at ~162.4 (2p3/2) and ~163.6 eV (2p1/2) are ascribed to bridging disulfide (S22-)9,25, demonstrating the formation of surface unsaturated sulfur. Worth noting that a positive shift of Cd 3d and S 2p binding energy emerges after the impregnation of Pt, which results from the surface reconfiguration over 1%Pt/CdS and 2%Pt/CdS. In terms of Pt 4f (Supplementary Fig. 4b), it is noticed that doublet subpeaks appear to be present in the spectra of 1%Pt/CdS and 2%Pt/CdS, and their spin-orbital splits are 3.3 eV according to the deconvolution analysis. Compared with standard Pt0 state (4f7/2 at ~70.6 eV, 4f5/2 at ~73.9 eV), the binding energy of dominating doublets are positively shifted, indicating that Pt is in an oxidation state (Ptδ+)26-28. Moreover, as Cl signals were not detected in XPS (the lower limit of detection is 0.10%), it is disclosed that chloroplatinic acid precursor residues on materials surface have been basically removed (Supplementary Fig. 6a). Importantly, electron paramagnetic spectroscopy (EPR) revealed that the signals for unpaired electron over CdS decreased with the loading of Pt, indicating Pt could be anchored on unsaturated sulfur (Supplementary Fig. 7). Additional demonstrations on Pt coordination are provided by analyzing X-ray absorption fine structure consisting of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Fig. 2a displays the normalized Pt L3-edge absorption spectra which are calibrated referenced on XANES first derivative spectra. 1%Pt/CdS and 2%Pt/CdS exhibit almost identical XANES of which the white-line peak intensity is between Pt foil and PtO2. This phenomenon also manifests that Pt species in 1%Pt/CdS and 2%Pt/CdS are both in an average electron efficient state and it rises from Pt0 to Ptδ+(0<δ<4)29. Pt L3-edge EXAFS is presented in k-space and R-space. EXAFS in k-space (Supplementary Fig. 8) still exhibits distinguished discrepancy between samples and references. But in R-space (Fig. 2b), exclusive Pt-S bonds are observed in the first shell of 1%Pt/CdS and 2%Pt/CdS while the contribution of Pt-O and Pt-Pt is absent. Taking these phenomena into consideration, it is reasonable to speculate that Pt is anchored on CdS through coordinating with unsaturated sulfur.

Accordingly, a possible configuration for Pt is constructed (model structures are provided in Supplementary data 1) and the corresponding EXAFS fitting is carried out (Fig. 2c and Supplementary Table 2). In the first shell of 1%Pt/CdS, Pt is coordinated with S atom (~2.33 Å) and average coordination number (N) is determined to be approximately 2.58. The contributions in the second shell originate from Pt-Cd (N=1.16) coordination of which the radial distance is approximately 2.78 Å. The appearance of Pt-Cd rather than Pt-Pt coordination indicates that Pt species exhibits high dispersity and Pt clusters or particles are not formed. As to 2%Pt/CdS, Pt-S bond in the first shell is still found and the coordination is close to 1%Pt/CdS, but the Pt-Cd contribution can hardly be observed (Supplementary Table 3). The wavelet transformation (WT) is adopted to combine k and R space together and unveil Pt coordination environment. As displayed in Fig. 2d-g, Pt-S bond makes dominated contributions to the ultimate results for 1%Pt/CdS and 2%Pt/CdS, while Pt-Cd contribution can only be found in the former. CO adsorption-desorption experiments for Pt configuration revelation are recorded (Fig. 2h and 2i). In contrast to CdS (Supplementary Fig. 9), the overlapped vibrations signals can be observed over 1%Pt/CdS and 2%Pt/CdS when CO have been adsorbed until saturation. After continuous purging with inert gas, weak CO adsorption signals retained at 2110~2104 cm-1, corresponding to the adsorbed CO on Ptδ+. Compared with typical signals (~2084 cm-1), the wavenumber was increased30-32. It is speculated that the anchored Pt over CdS could have strong affinity with CO. Importantly, no band at ~1950 cm-1 was found, demonstrating there was no any bridge-adsorbed CO between Pt clusters and the support. High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) revealed the sporadic Pt atoms on the lattice of 1%Pt/CdS due to the contrast difference (Supplementary Fig. 10a). Same phenomenon was also detected over 2%Pt/CdS while the density of Pt atoms was increased (Supplementary Fig. 10b). The abovementioned results support that the highly dispersed Pt-S configuration (Fig. 2j, Supplementary Fig. 11 and Supplementary Data 1) is formed over 1%Pt/CdS and 2%Pt/CdS, even if there is minor difference in the coordination environment. Regarding these differences, this work ascribes it to the variation of Pt amount. According to inductively coupled plasma optical emission spectroscopy (ICP-OES), the accurate Pt amount over 1%Pt/CdS and 2%Pt/CdS are determined to be 0.98 wt% and 1.99 wt%. It is speculated that with the increasing of Pt amount, the coordination environment becomes homogeneous and regular.

Taking the micro-configuration characterizations into account, it can be concluded that CdS surface which is rich in unsaturated sulfur site was successfully constructed. The loading of Pt led to the formation of additional Pt sites on CdS surfaces. The Pt sites were identified to exist in an oxidation state of δ+. As the accurate amount of Pt in sample is pretty close to the theoretical value, 1%Pt/CdS and 2%Pt/CdS are then marked as Pt1/CdS and Pt2/CdS for the following works.

Excited-state dynamics and charge migration
To investigate the effects of unsaturated sulfur and Pt sites on the migration processes of photogenerated electron and hole, the light absorption capacity and charge carrier dynamics were systematically analyzed. The steady-state absorption of prepared sample was revealed through ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). The dominating absorption peaks at around 500 nm corresponds to the band edge electron transition in CdS, which are prominent over three samples (In Supplementary Fig. 12). Importantly, through analyzing the band structure based on XPS valence band spectra and steady-state absorption edge revelation (Supplementary Fig. 13), it is found that the band edge position of CdS, Pt1/CdS and Pt2/CdS is similar with each other. This result indicates that there is limited discrepancy in the energy of excited carriers and more attention should be given to excited-state dynamics. To detail the charge excitation of samples, femtosecond transient absorption spectroscopy (TAS) was adopted for excited-state dynamics studying. TAS probing region is from 450 to 700 nm, and 400 nm pump light is used to excite the samples. The pump laser pulse fluency is modulated to a low level (~5 μJ∙pulse-1∙cm-2) so that there is exclusively single exciton dynamics reflected in TAS and the possible Auger recombination is not considered (Supplementary Fig. 14). Exhibited in Fig. 3a and Supplementary Fig. 15a, TAS of CdS are mainly featured with two typical signals: an increased absorption at ~420 nm induced by the excited-state absorption (ESA) in the presence of 1S excitons, and a ground-state bleach (GSB) at ~505 nm resulting from the state filling at the conduction band (CB) edge. The weak tail bleach at ~600 nm is ascribed to the interband states induced by surface unsaturated sulfur33-35. To determine the contribution of excited electron and hole to the tail bleach, electron trapping agent p-benzoquinone (BQ)36,37 was used to quench the signal. In Supplementary Fig. 16a, as BQ is introduced, kinetic decay curves at 600 nm keep almost identical, illustrating that the tail bleach is only contributed by hole. Noting that with the growing of Pt amount, additional steady-state absorption from 550 to 800 nm is increasing over Pt1/CdS and Pt2/CdS while they could possibly generate TAS signal. However, 600 nm bleach signals over three samples (Supplementary Fig. 16b and Fig. 16c) are almost identical and they are all not influenced by BQ. These phenomena illustrate that tail bleach at 600 nm in Pt1/CdS and Pt2/CdS are still contributed by CdS. Importantly, the tail bleach at 600 nm can serve as an indicator to illustrate the hole-related processes.

The excited state dynamics reflected in TAS is visualized through singular value decomposition (SVD) global fitting, and the results (Supplementary Table 4) are attached with the contour plots. SVD global fitting is a unified separable nonlinear model which can describe all measurements collected over multiple independent variables38. The carrier dynamics of CdS can be fitted with four bleach recovery time constants. The fastest one (τ0, 3.5 ps) is ascribed to the exciton cooling, where there is only a bleach at 480 nm. For the second constant (τ1, 13.4 ps), the tail bleach at 600 nm appears accompanying with GSB at 505 nm, illustrating that a hole-transfer process from valence band (VB) edge to interband state is revealed. τ2 at 397.0 ps is only featured with GSB and tail bleach has been completely removed. It demonstrates that the hole on interband state is further trapped and τ2 should be ascribed to the intrinsic recombination of CdS. Inf includes the photodynamic processes of which the lifespan exceeds the TAS time-window. As to Pt1/CdS and Pt2/CdS, the intrinsic excited dynamics of CdS was both maintained but the average lifespan has been reduced. This phenomenon indicates that the exotic noble metal can facilitate the carrier relaxation39. The distinguished variations are detected over time-components number, as there is an additional recovery time-component (τef) of which the timescale is only slower than τ0. τef consists of ESA and GSB, and there is no any tail bleach. It is thus reckoned that τef should be associated with electron transfer from CdS CB edge to Pt states. To demonstrate this speculation, GSB signal decay at ~505 nm is also analyzed using BQ as trapping agent. In Supplementary Fig. 17, GSB decay of CdS is remarkably accelerated when BQ is introduced, demonstrating excited electron of CdS can be trapped by BQ. As to Pt1/CdS, GSB decay is slightly enhanced because a part of electron is simultaneously transferred to Pt. While for Pt2/CdS, excessive Pt attracts most of electron, and the influence of BQ on GSB decay is negligible.

To well display the variations in photodynamics, GSB signal decay of three samples are presented in Fig. 4a. For Pt1/CdS and Pt2/CdS, kinetic decay can be initially observed at ~2 ps due to the electron transfer (τet) induced by Pt, while for CdS, the prominent decay is found at ~10 ps because of the hole transfer (τ1). The overall trend matches with the global fitting results above. The kinetic studying is also supported by time-resolved photoluminescence (TRPL) and steady-state photoluminescence (PL) spectroscopy which can explore the involved carrier recombination. Limited by instrument response function (Fig. 4b), recombination process observed in TAS are all included in the fastest time-component (Supplementary Table 5) of TRPL and it is almost identical over CdS, Pt1/CdS and Pt2/CdS (τ1, 2 ~2.0 ns). But as Pt has noticeably accelerated the carrier relaxation, the lifetime of τ1, 2 and τ3 shrink with the increasing of Pt amount. The average photoluminescence lifetime (τave) was 258.6 ns, 62.9 ns and 49.1 ns for CdS, Pt1/CdS and Pt2/CdS, respectively. Worth noting that the faster carrier recombination in Pt1/CdS and Pt2/CdS was also accompanied with a steady-state PL deterioration (Supplementary Fig. 18), indicating that a non-radiative channel is simultaneously formed, which is strongly related with the process of electron-transfer to Pt. Excited-dynamics reveals the contribution of Pt and unsaturated sulfur to electron and hole trapping in similar ultrafast timescale. It is also reasonable to speculate that excited electron relaxation is promoted by transferring to Pt states, while hole is simultaneously trapped on unsaturated sulfur sites (Fig. 4c).

But surface reaction occurs beyond the window of time-resolved spectroscopies, to demonstrate long lifespan of those trapped carriers, the carrier distribution on photocatalyst surface is further investigated through in-situ XPS. In-situ XPS in dark field is collected as reference while the data in light field is recorded after 5 minutes irradiation (Fig. 4d-i and Supplementary Fig. 19). Scrutinizing the fine spectra of CdS, it is clear to notice that the element binding energy is slightly shifted under light irradiation, illustrating the hole-aggregation on photocatalyst surface. This result unveils the long-lived hole over CdS, and it demonstrates that the trapped excited hole can be further localized on unsaturated sulfur. As to Pt1/CdS and Pt2/CdS, the binding energy shift is not consistent with each other, and it changes from positive to negative with the growing of Pt amount. The electron-aggregation dominating the surface manifests that Pt can also localize electron for a long timescale. Transient photocurrent response provides additional evidences to this speculation. Under visible light irradiation (Supplementary Fig. 20), an increased positive photocurrent can be detected over CdS as the unbound electron is released into the circuit with applied bias, and hole is localized on unsaturated sulfur. Noticeably, photocurrent intensity over Pt1/CdS is sharply decreased and for Pt2/CdS there is almost no detected photocurrent. Incident monochromatic photon-electron conversion efficiency (IPCE) profiles of CdS, Pt1/CdS and Pt2/CdS all aligns with their steady-state absorption curve (Supplementary Fig. 21 and Supplementary Fig. 22), but the highest IPCE are still observed over CdS (Supplementary Table 6). These phenomenon can be associated with the strong electron localization on Pt, which hinders the electron transfer from working electrode to the counter electrode40. Here, integrating the charge carrier dynamics in different timescale together, the function of Pt and unsaturated sulfur in photocatalysis is clearly disclosed, which can separately trap electron and hole within picoseconds, while simultaneously localize them for surface photocatalytic reactions.

Photocatalytic evaluation and mechanism revelation
Given the characteristics of as-prepared samples, an evaluation on photocatalytic CH4 selective oxidation was subsequently carried out based on a top-irradiation sealed glass reactor (Supplementary Fig. 23). To commence with, a contrast experiment was conducted to determine the optimized photocatalyst amounts for current system. In Fig. 5a, the gradient-increasing CH3OH production rate is observed when there is less than 10 mg photocatalysts. But when photocatalyst amount exceeds 10 mg, the average CH3OH production rate rapidly decreases, because the superfluous photocatalyst can hardly participate in target reactions41-44. Based on the determined photocatalyst amount, the evaluation experiments were subsequently carried out. Fig. 5b and 5c display the statistic amount of CH3OH and other C1 oxygenates during the irradiation period. A prominent CH3OH production rate is detected over Pt1/CdS (12.72 μmol g-1 min-1), which is remarkably better than CdS (5.07 μmol g-1 min-1) and Pt2/CdS (7.88 μmol g-1 min-1). Peroxides in current system consist of HCHO and CO2, and their distributions in products vary with CH3OH amount: the higher CH3OH production rate, the smaller peroxides proportion in products (Fig. 5d and Supplementary Table 7). The C2 hydrocarbons (including C2H6, C2H4 and C2H5OH) was also scrutinized using Pt1/CdS as photocatalyst, while no any products were found, indicating the products mainly consist of C1 hydrocarbons. On this basis, supplementary contrast group Pt0.5/CdS and Pt1.5/CdS were also prepared to demonstrate the performance of Pt1/CdS. As displayed in Supplementary Fig. 24, the overall performance of Pt0.5/CdS and Pt1.5/CdS are still inferior to the marked Pt1/CdS, indicating the scare or excessive Pt sites can hardly maximize the synergy of Pt and unsaturated sulfur in photocatalysis. To further complement the evaluation process, additional tests were carried out by modulating the necessary parameters, and the photocatalyst was Pt1/CdS. In Fig. 5e, the removal of O2 seriously deteriorated the overall performance, while when CH4 and light were separately removed, there was no CH3OH detected in the system. Moreover, it was noticed that the reaction temperature contributes to ultimate performance, because in contrast to optimized conditions, lower temperature (40°C) leads to lower CH3OH amount. As to the durability of photocatalysts, cycle experiments were carried out. Similar CH3OH production rate and products selectivity was observed in the first three rounds, indicating its photocatalytic stability in 360 min (Fig.5f and Supplementary Fig. 25). Moreover, to evaluate the structural stability of photocatalyst, XRD and XPS of used Pt1/CdS was scrutinized. The typical diffraction peaks of used samples in XRD can match with fresh ones while no additional peaks appeared, illustrating the crystal stability of CdS, Pt1/CdS and Pt2/CdS (Supplementary Fig. 26). Cd 3d and S 2p fine spectra of used Pt1/CdS are almost identical with the fresh one (Supplementary Fig. 27d and Supplementary Fig. 27e) while no lattice oxygen (Supplementary Fig. 27f) and SO42- (Supplementary Fig. 28c) signal appeared, excluding the photocorrosion of used Pt1/CdS. Besides, in Pt 4f fine spectra of used Pt1/CdS (Supplementary Fig. 28d), Ptσ+ was still detected after XPS fitting accompanied with no any reduced metallic Pt0. This phenomenon further demonstrates the stability of Pt-S configuration over Pt1/CdS. Ultimately, to present the performance of current system from a holistic perspective, turnover number (TON, ~15.19) and turnover frequency (TOF, ~0.25 min-1) over best Pt1/CdS are summarized in Supplementary Fig. 29, while apparent quantum efficiency (AQE) at 395 nm were calculated. AQE at 395 nm is ~1.00% for CH4 to CH3OH conversion (Supplementary Fig. 30, Supplementary Fig. 31 and Supplementary Table 8). Moreover, the activity of Pt1/CdS has been compared with analogous systems in Supplementary Table 11 and it is competitive in normal pressure system.

The experimental data above indicate that when utilizing unsaturated sulfur sites solely to accelerate hole transfer and create hole-localized centers, CH4 activation occurs but leads to overoxidation, resulting in reduced CH3OH selectivity. Similarly, excessive introduction of Pt sites creates electron-rich centers on surfaces, yet still triggers overoxidation. In contrast, the Pt1/CdS system combines electron-enriched Pt sites and hole-localized unsaturated sulfur sites. The formation of Pt-S bonds enables long-term stabilization of photogenerated electron and hole at their respective active centers. This synergistic configuration not only achieves efficient CH4 activation but also directs its selective conversion to CH3OH while suppressing overoxidation pathways.

To probe the underlying mechanisms, the CH4 conversion processes on various sample surfaces are systematically analyzed through in-situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) as Fig. 6a-c and Supplementary Fig. 32a-e display. For CdS, during the adsorption process, O-H bond bending vibration45 in H2O (~1640 cm-1) and C-H bond stretching vibration46 in CH4 (~1340 cm-1) are enhanced, demonstrating that reactants are adsorbed on photocatalyst surface. A new peak at 1013 cm-1 is assigned to H-C-S vibration of S-*CH4 configuration47,48, proving that the unsaturated sulfur is the adsorption site of CH4. Under light irradiation, there are new absorption bands assigned to *HCHO (1170~1132 cm-1)49,50, *CH3OH (~1036 cm-1)9 and CO32- (~1245 cm-1 *O-C-O)51 appearing. This indicates the following CH4 conversion pathway on CdS surface.
*CH4 → *CH3OH → *HCHO → CO32- over CdS

For Pt2/CdS, the adsorption processes are comparable to those of CdS. However, under light irradiation, additional intermediates attributed to *CH3O (~1088 cm-1)9 is observed alongside those typically detected on CdS surfaces. This observation reveals a distinct CH4 conversion pathway occurring on the Pt2/CdS surface, as schematically illustrated below.
*CH4 → *CH3O → *CH3OH → *HCHO over Pt2/CdS

In contrast to the aforementioned samples, signals attributed to *CH3 (1430 cm-1)52 are detected on the surface of Pt1/CdS after light irradiation (Fig. 6c), indicating that the emergence of new electron-rich sites effectively suppressed the overoxidation process.
*CH4 → *CH3 → *HCHO → CO32- over Pt1/CdS

To understand why the structurally different sites can effectively inhibit the overoxidation of CH4, the mechanism of action of the active sites on different surfaces has been analyzed. For CdS, due to the fact that the sites on the surface are mostly unsaturated sulfur sites that enrich photogenerated holes under light irradiation, these sites can not only effectively capture CH4 to promote the activation of its C-H bond, but also convert H2O into hydroxyl radicals (∙OH, OH- + h+ → ∙OH). To confirm the above conclusion, the contrast experiment of CH4 conversion in anerobic and moist atmosphere (H2O+CH4) under light irradiation was carried out. As shown in the Supplementary Fig. 33, after CH4 and H2O adsorption equilibrium was reached, the peaks of typical H-C-S vibration, adsorbed H2O and CH4 appeared. With constant light irradiation, the intensity of these characteristic peaks decayed while *CH3OH rose (*CH4 → *CH3OH), indicating that CH4 overoxidation can also be promoted. More importantly, when CH4 is bubbled into aerobic water to imitate photocatalytic CH4 conversion (Supplementary Fig. 34a), ∙OH intensity dramatically decreased, which demonstrates that the unsaturated sulfurs sites to generate ∙OH have been occupied by adsorbed CH4. The above data indicate that on the surface of CdS, the constructed unsaturated sulfur sites that enrich photogenerated holes are not only the adsorption and activation sites of CH4, but also the sites for H2O oxidation to generate ∙OH. Since the generation of reactive oxygen species (ROS) and the adsorption of CH4 both occur through the same site, it causes CH4 to be prematurely attracted and captured by the photogenerated holes at the site, resulting in that CH4 was consecutively attacked by ROS, leading to the occurrence of overoxidation reactions.

For Pt2/CdS of which surface is predominantly composed of electron-enriched Pt sites under illumination, CH4 activation and ROS could also be carried out on one site. Revealed by in-situ EPR (Supplementary Fig. 34b), ∙OH signals were still deteriorated when CH4 was bubbled into aerobic water. Moreover, in-situ DRIFTS unveiled the decreased peak assigned to H-C-S vibration on Pt2/CdS surface in Fig. 6b, ruling out unsaturated sulfur as primary CH4 adsorption sites (unlike CdS). Thus, the contrast experiments of ROS detection in aerobic CH3OH were additionally conducted (Supplementary Fig. 35). CH3OH is the trapping agents for ∙OH so that ∙OOH signals can be triggered. In contrast to CdS, ∙OOH signals have remarkably declined as the rapid electron-injection over Pt2/CdS promotes ∙OOH conversion to ∙OH (O2 + e- → ∙O2-, ∙O2- + H+ → ∙OOH, ∙OOH + H+ + e- → ∙OH). Pt sites, based on above results, are identified as the ∙OH generation sites over Pt2/CdS, which can simultaneously facilitate CH4 activation via the pure electrophilic activation process.

For Pt1/CdS, which possesses both electron-enriched Pt sites and hole-enriched unsaturated sulfur sites on its surface, the prerequisites for mimicking the stepwise reaction mechanism of enzyme are established. Specifically, the electron-rich Pt sites activate O2 to generate ROS, while the hole-localized sulfur sites temporarily capture CH4. Subsequently, ROS attack the CH4 adsorbed on the sulfur sites, enabling single hydrogen atom extraction from CH4 to form CH3OH. To validate this hypothesis, CH4 adsorption behavior was first investigated. As shown in the Fig. 6c, the H-C-S vibration characteristic peak still emerged on Pt1/CdS surface during adsorption, confirming that unsaturated sulfur sites serve as CH4 adsorption centers. Notably, under light irradiation, the attenuation rate of this signal was slower compared to that observed on CdS, indicating that while photogenerated holes effectively capture CH4 molecules, they do not accelerate C-H bond cleavage as aggressively as in CdS. Necessarily, in-situ EPR analysis (Supplementary Fig. 34c) implied that ∙OH generation over Pt1/CdS can hardly be influenced with CH4 adsorption, indicating that there are separated sites for CH4 activation and ∙OH generation. Furthermore, Pt1/CdS can also give impetus to ∙OOH conversion to ∙OH in aerobic CH3OH because Pt sites promote electron-injection for ∙OH generation (Supplementary Fig. 35). Computational simulations for static adsorption corroborated the findings above, demonstrating preferential adsorption of CH4 at unsaturated sulfur sites. The geometry optimized configuration Pt1/CdS (Fig. 6d and 6e) consists of typical unsaturated sulfur sites and Pt sites, but CH4 adsorption energy (Supplementary Table 9 and Supplementary Data 1) on the former site is more negative (-0.19 eV) than the latter site (-0.098 eV). This spatially segregated adsorption ensures that ROS generation (at Pt sites) is not overlapped with CH4 activation (at unsaturated sulfur sites), establishing a stepwise reaction pathway. The temporal and spatial decoupling of these processes allows ROS to dominate the selective extraction of a single hydrogen atom from CH4, steering the reaction toward CH3OH formation while suppressing overoxidation. Ultimately, surface area analysis (Supplementary Fig. 36 and Supplementary Table 10) was also carried out, and the similar surface area among three samples indicated that the total active sites of CdS are not influenced by Pt sites construction, but the charge carrier dynamics induces a more productive conversion process.

Methods
Chemicals
Chloroplatinic acid (H2PtCl6·6H2O, ≥99.9%), cadmium chloride (CdCl2·2.5H2O, ≥98%), p-benzoquinone (C6H4O2, ≥99.9%) and sodium sulfite (Na2SO3, ≥98%) were purchased from Aladdin (Shanghai, China). Sodium sulfide (Na2S·9H2O, ≥98%) and hydrochloric acid (≥37%) were provided by a local chemical agent company (Chron Chemicals, Chengdu, China). The reagents used for materials synthesis and related experiments were all in analytical grade without further purification.

Characterizations
Crystal structure of as-prepared photocatalyst was researched through X-ray diffraction (XRD, PANalytical X’Pert) which was operated with Cu Kα radiation. The morphology and microstructure characterizations were conducted through high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). HRTEM was recorded on a Tecnai G2 F30 transmission electron microscope. Pt element distribution in samples was investigated through Agilent 5110 inductively coupled plasma-optical emission spectrometer (ICP-OES). A Thermo-Scientific Kα spectrometer was used to record X-ray photoelectron spectra (XPS) of samples to investigate electronic state of element. The coordination environment of noble metal element was explored by recording X-ray absorption fine structure (XAFS). X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) at Pt L3-edge was collected at Shanghai Synchrotron Radiation Facility BL11B station. XAFS data of standard Pt foil and PtO2 was shared by the group of Nano-Catalysis Group at Sum Yat-sen University and Shanghai Synchrotron Radiation Facility. k3-weighted EXAFS was wavelet-transformed based on the Continuous Cauchy Wavelet Transform (CCWT) method53,54. XAS data analysis and fitting were all processed using Athena, Artemis and Hephaestus software55. Steady-state absorption spectroscopy and photoluminescence (PL) spectroscopy were collected to investigate the optical properties of samples. The former was recorded on a Shimadzu UV-2600 spectrophotometer equipped with an integrating sphere (BaSO4 was the reference standard), and the latter was obtained on a Hitachi F-7000 fluorescence spectrophotometer. In-situ electron paramagnetic resonance (EPR) spectra are recorded by a JES FA200 electron spin resonance spectrometer, and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) served as trapping agents. EPR for crystal defects characterizations were recorded on a CIQTEK EPR200 electron spin resonance spectrometer. To detect the element binding energy shift, XPS in dark and light field was then collected on an AXIS Supra (Shimadzu, Japan) spectrometer with Al Kα source (1486.6 eV), and 365 nm monochromatic light was used to provide excitation light. Before the XPS collection in dark field, sample film was fixed on a sample stage using conducting resin while the XPS chamber was vacuumized. Then the sample was irradiated under monochromatic light for 5 min, and XPS in light field began to be collected. When XPS in light field was collecting, monochromatic light was constantly irradiated. Given that in vacuum environment, the binding energy shifts of in-situ XPS can only be induced by surface charge carrier localization, the energy calibration is referenced on adsorbed carbon species (C 1s at 284.8 eV).

Photocatalyst preparation
CdS preparation: A conventional hydrothermal method is adopted to synthesize CdS. Specifically, CdCl2·2.5H2O (4 mmol) is dissolved in 20 mL hydrochloric acid aqueous solution (19.5 mL deionized water and 0.5 mL hydrochloric acid) to prepare solution A. Then, Na2S solution is prepared by dissolving 8 mmol Na2S∙9H2O in 20 mL deionized water, and it is marked as solution B. Solution B is dropped into solution A slowly with constant magnetic stirring. An orange-yellow suspension is obtained with the mixing of two solution, and the suspension was immediately transferred to a 50 mL polytetrafluoroethylene autoclave equipped with Teflon-lined stainless steel. Furthermore, the sealed autoclave was maintained at 140°C for 18 h to promote the secondary growth of crystal. When the autoclave was cooled to room temperature, the suspension in autoclave was centrifugated and washed using deionized water and alcohol. After being dry in an oven overnight, CdS powder is obtained.

Pt-loaded CdS preparation: This work prepares Pt-loaded CdS through an impregnation method. Firstly, 100 mg CdS powder was dispersed in 30 mL deionized through ultrasonic treatment. Following the adding of an amount of chloroplatinic acid aqueous solution, the suspension was maintained at 70°C for 6 h with constant magnetic stirring. Pt-loaded CdS is obtained after centrifugation, washing and vacuum drying. Supplementary Fig. 2 displays the image of as-prepared samples. Based on the theoretical amount of Pt, Pt-loaded CdS is marked as X%Pt/CdS, and X is calculated based on Equation 1. The accurate amount of Pt element in X%Pt/CdS is determined through inductively coupled plasma-optical emission spectrometer (ICP-OES). According to the results of ICP-OES, 1%Pt/CdS and 2%Pt/CdS is also written as Pt1/CdS and Pt2/CdS. Same procedures are also adopted to prepared 0.5%Pt/CdS and 1.5%Pt/CdS, and they are marked as Pt0.5/CdS and Pt1.5/CdS.

X = (The mass amount of Pt / The mass amount of CdS) × 100 (1)

Excited-state dynamics revelation
Excited-state dynamics of samples was deduced from transient absorption spectroscopy (TAS) and time-resolved photoluminescence (TRPL) spectroscopy. TAS was recorded on an Ultrafast System Helios-TA spectroscopy system of which 800 nm pulse laser was produced by a Spectra-Physics Solstice Ace laser device. The pulse width of the laser was ~140 fs and the corresponding repetition rate was 1000 Hz. 800 nm laser pulse was divided into two beams which are separately used as pump light and probe light. The wavelength of pump light was conversed to 400 nm as 400 nm pump light can well excite sample based on their steady-state absorption. The corresponding pump light power ranged from 70 to 500 μW. Probe light was also modulated and it consisted of continuous white light (450-700 nm). To prepare the samples suspension, 4 mg CdS or Ptx/CdS powder was dispersed in 10 mL ethyl alcohol with constant ultrasonic treatment. The suspension was transferred to a glass cuvette which can allow the transmission of both pump light and probe light. TAS signals were collected when pump light and probe light beams were overlapped. To reveal the contribution of trapping agents to photodynamics, p-benzoquinone (BQ) was added into sample suspension. BQ is a type of organic molecule where there are two symmetrical ketone functional groups in their structure, so that BQ exhibit oxidizing properties and it can actively attract photogenerated electron, simultaneously facilitating excited carrier relaxation in TAS. The related experiments were based on the following procedures. BQ was dissolved in ethyl alcohol to prepare 0.5 M electron-trapping agent solution (solution X). 100 μL solution X was mixed with 200 μL sample suspension with constant stirring so that BQ can be fully adsorbed. The TAS signals of prepared suspension were then recorded. Excited-state dynamics in this work are fitted with SVD global fitting. Particularly, SVD involves eliminating the less important parts in dataset and producing an accurate approximation data for which sufficient exponential decays and their amplitudes will be adopted to fit. Then the feature and timescale of specific dynamic processes can be assigned. TRPL measurements were carried out based on a time-correlated single photon counting setup (TCSPC). The associated pulsed diode laser is triggered at 5 MHz and 438 nm photon excited the sample dispersed in alcohol.

Photoelectrochemical evaluation
Photoelectrochemical characterizations were conducted using a Chenhua Instrument (Shanghai, China) electrochemical station equipped with a three-electrode system. Pt wire and Hg/HgO electrode worked as counter electrode and reference electrode, respectively. To prepare working electrode, a doctor-blade coating technique was adopted to make a photocatalyst film on 2.0×1.5 cm2 indium tin oxide (ITO) glass (the size of photocatalyst film is 1.0×1.0 cm2). To get the film stable, working electrode was annealed at 160°C for 2 h before photoelectrochemical evaluations. 0.6 M Na2SO3 solution worked as electrolyte and a Merry Change XS500 lamp provided light source. To record transient photocurrent response, Pt wire, Hg/HgO electrode and working electrode were firstly integrated and immersed in 50 mL 0.6 M Na2SO3 solution electrolyte. The electrolyte was prepared by dissolving 3.7812 g Na2SO3 into 50 mL deionized water, and it was stored in sealed reactor. The pH value of electrolyte was determined to be 10.8 ± 0.1 at room temperature. The open circuit potential (OCP) of working electrode was observed until the value got relatively stable (the sensitivity was set to 10-4 V). Then an applied potential which equal to OCP was set between working electrode and Pt electrode. With 50 s interval time, an artificial light was irradiated on working electrode and photocurrent was recorded. The photocurrent cycles were lasted for more than 20 rounds. Corresponding OCP over CdS, Pt1/CdS and Pt2/CdS are 1.14 V, 0.60 V and 0.62 V (reference to RHE). Incident monochromatic photon-electron conversion efficiency (IPCE) measurements was carried out in same conditions but the applied potential was set 1.13 V (corresponding to the onset potential of linear sweep voltammetry, RHE). To provide monochromatic light, a filter was installed on lamp to bypass photons (450 nm, 500 nm, 600 nm and 700 nm). See more experimental details in Supplementary Information for IPCE measures. The voltage is not iR corrected for all photoelectrochemical tests.

Photocatalytic evaluation
Methane (CH4) photooxidation evaluation was conducted in a 400 mL PQ-256 glass reactor (Beijing Perfect Light Technology Co., Ltd., Beijing, China) with a quartz window for light irradiation. The reactor was sealed after the photocatalyst suspension (10 mg sample was dispersed into 50 mL deionized water) was poured into the reactor. The simulation sunlight was produced by a 300 W CEAULIGHT Xe lamp (CEL-HXF300, central light intensity is set ~600 mW∙cm-2, >420 nm). The temperature of reaction system was maintained at 60°C using a water-cooling bath. Before photocatalytic tests, the sealed glass reactor was ventilated using diluted oxygen gas (10 vol% in N2 gas) to exhaust the air. The ventilation process lasted for approximately 30 min. Furthermore, 5 mL CH4 gas (99.99%) was injected into the reactor before the irradiation got started. Every 20 min, 1 mL gas in the reactor was extracted for gas components analysis through the gas chromatographs (Shimadzu GC-2010，and Agilent Technologies 7890B). To quantify the amount of HCHO, a reported colorimetric method is adopted to determine the target substances in aqueous solution56. HCHO owns electrophilic properties and it can react with pentane-2,4-dione to form colored substances. The specific experimental procedures of colorimetric method include: Firstly, colorimetric reagent solution was prepared through dissolving 15 g ammonium acetate, 0.3 mL of acetic acid and 0.2 mL pentane-2,4-dione in 95.5 mL deionized water. Secondly, 0.5 mL liquid in photocatalytic reactors and 0.5 mL of colorimetric reagent solution was dissolved in 2.0 mL deionized water, and then maintained at 80°C for 10 mins with water bath. Furthermore, the ultra-violet and visible absorption spectroscopy of the mixed liquid was measure. The absorbance at 412 nm is proportional to the concentration of HCHO in the liquid. Photocatalytic cycle experiments were based on the following procedures. After 60 min photocatalytic reaction, the photocatalyst dispersed in suspension was centrifugated and collected. The collected photocatalysts was washed with deionized water and then further tested for photocatalytic CH4 conversion. The CH4 conversion rate and product selectivity was determined by

CH4 Conversion(%)= n(product)all / n(CH4)input × 100%

Selectivity (%) = n(product)all / n(CH4)converted × 100%

Turnover number (TON), turnover frequency (TOF) and apparent quantum efficiency (AQE) determination
TON and TOF was obtained based on Equation 2 and 3, and N(Pt) and N(CH3OH) represented the mole of Pt supported on substate materials and the mole of CH3OH (see more details in Supplementary Information for specific TON and TOF calculation). t is the reaction time. AQE was determined referenced on Equation 4 and 5, where P is the power of light,  is the wavelength of photons, h is the Planck constant (6.63×10-34 J∙s) and c is the speed of light (3×108 m∙s-1). The number of electrons for one CH3OH molecule formation is 3. See more details for TON, TOF and AQE determination in Supplementary Information.

TON = N(CH3OH) / N(Pt) (4)

TOF = N(CH3OH) / (N(Pt) × t) (5)

AQE = Number of electron / Number of incident photon (6)

Number of incident photon = (P × t × ) / (h × c) (7)

In-situ DRIFTS measurements
In-situ diffuse reflectance infrared Fourier transform spectroscopy (In-situ DRIFTS) measurements were carried out to explore possible surface reaction steps, which were conducted based on a Bruker infrared spectrometer (Tensor II) equipped with a liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector. A Harrick Praying Mantis three-window diffuse-reflectance cell was installed to load samples. The silicon oxide window was used for light irradiation, while two measurement windows were made of ZnSe. In specific, sample was placed into the cell chamber and heated at 100°C to remove adsorbed substances. Then the constant gas flow consisting of reactants (CH4, O2 and H2O) was injected into the chamber for reactants adsorption. Immersed in the atmosphere for more than 20 min, the corresponding in-situ DRIFTS intensity became stable and there was no more obvious growing. The samples were subsequently illuminated by artificial light. Moreover, to collect CO desorption in-situ DRIFTS, samples was also placed in the cell chamber and continuous CO flow was injected into the chamber. The intensity of CO characteristic peaks in the region from 2300 to 1900 cm-1 were intentionally focused. Finally, CO flow was aborted and continuous Ar flow was injected to drive CO desorption.

Computational details
The computational calculations were implemented based on the Vienna ab initio simulation package (VASP). The interaction between ion cores and electrons were described using the projector augmented wave (PAW) method. The electron exchange-correlation was carried out through generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional. The k point was set to be 2×2×1 and cutoff energy was 400 eV. To guarantee the energy convergence, the configurations of the convergence threshold were set to be namely 1×10-5 eV per atom for the maximum energy change, 0.02 eV/Å for maximum force. The lattice constants of CdS crystal used in this work are a=b=4.135 Å and c=6.749 Å. The configurations concerning CH4 adsorbed on unsaturated sulfur site and Pt site are marked as Pt1/CdS (S) + CH4 and Pt1/CdS (Pt) + CH4, respectively.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The work by Y. Li et. al., focuses on the catalytic conversion of methane to methanol using impregnated nanoparticles of CdS with Pt. The Pt is proposed to exist in different oxidation states that favor conversion of methane to methanol through a temporary adsorption of methane to the surface. I was left with many questions regarding this manuscript that I would hope the reviewers could address.\n1. I was confused by the connection to biomimetics in the abstract of this paper. There doesn’t seem to be any connection to biology in this system (the authors argue that the coordination of dioxygen to a diiron center satisfies this connection), however there is little connection to diiron or any enzymatic science. The authors are not attempting to do careful synthetic work to create an artificial mimic of the active sites used in these systems. If anything, this could be motivated by a more controlled heterogeneous catalysis route similar to what is argued in their first paragraph. The ability to limit the overoxidation of the methane to carbon monoxide through light absorbing materials is as impactful as the biomimetic route and is likely more relevant to their overall paper. I would suggest the authors look at J.Am.Chem.Soc, 2024, 146, 25989-25999 and the references therein for inspiration.\n2. I wouldn’t agree with the author’s statement of a “model” substrate. There are many peaks within the XRD and the SAED images that show polycrystalline nanomaterials are present in the sample. Although polycrystalline substrates are interesting on their own, these are far from “model” substrates. It would be useful for the authors to highlight what areas are Pt and what are CdS in their TEM images. A comment or two on the number and distribution of SAED spots would also be helpful. Another question is what is the distribution of particle sizes? Are they all a single distribution? Multi-distribution?\n3. The arguments made regarding the oxidation state that the Pt is in are difficult to follow. The authors suggest it is some sort of oxidized Pt but say it is not Pt(IV). I do not agree with this assessment based on their available data. First, their Reference 25 clearly put the contribution at 72.1 eV as a Pt(II) species, while the contribution at 73.6 eV is most likely a Pt(IV) species (I’m leaving out the spin-orbit pair Pt 4f5/2 peak for simplicity). This isn’t surprising given the chloroplatinic acid species heated in aqueous solution is most likely to form Pt (IV) species upon deposition. With the two different available oxidation states, regardless of what formal charge they have, why isn’t there multiple contributions in the XAFS? I wouldn’t expect the different oxidation states to have the same coordination numbers around them. Can the authors explain the lack of structure in their XAFS based on the presence of multiple species in the XPS? If the assumption is that all of the Pt is at the surface, then the XPS and XANES/XAFS should show similar results.\n4. Did the authors observe any Cl in their XPS? It would be useful to increase the size of Supplementary Figure 6 and label all peaks in the survey spectra.\n5. Did the authors take CO DRIFTS spectra without the Pt on their CdS particles? They explain what peaks are not there but it would be useful to explain the peaks that are there. In the 1% Pt/CdS sample, there is clearly a red shift in the desorption peaks that is not present in the 2% Pt/CdS sample. Can the authors suggest why and how this is? Why does the peak envelope at 2050 cm-1 change between the different samples? The peak at ~2200 cm-1 is not the same between the two samples, why is this?\n6. The caption in Figure 2 made it difficult to understand which sub-figure was related to the different letterings.\n7. Can the authors explain the shift in the UV-vis DRS spectra for the Pt1/CdS at 480 nm?\n8. Would the authors expect multiple different relaxation pathways given the different oxidation states of Pt? Why are they only observing a single Pt pathway?\n9. The shifts measured in Figure 4 are very small. They are also shifting with the same magnitude and direction which leads me to wonder if the authors are just measuring a charging effect on their samples. If the Pt is accepting an electron and the S is sitting with a long-lived hole species, then I would expect to see a Pt shifted to lower binding energy with the S shifted to higher binding energy. How were the samples mounted in the XPS spectrometer? Was the spectrometer properly calibrated? There are very few details regarding the photoelectron spectroscopy. It would be good to include this in the main text given its significance.\n10. At higher temperatures, I would have expected the rate of the reaction to increase and therefore more methanol to be observed. Can the authors provide more commentary on why they observe the opposite effect?\n11. In Figure 5d, were all of the systems characterized in this study or are they putting this in comparison with other work that has been done in the literature? If the latter, they should reference where they got all of the data.\n12. What is the relationship between relative humidity and the adsorption of water at the different sites on these systems?\n13. The lack of recognition of multiple Pt oxidation states within the interpretation of the reaction mechanism makes this difficult to grasp what the true nature of the Pt in this scheme. Which of the Pt oxidation states are responsible for the oxygen reduction? Is the Pt being reduced during this process?\n14. Can the authors comment more on their subtraction during the DRIFTS experiment and be more explicit in how to interpret the data? For example, my interpretation of the peaks is that they have desorbed all species from the heating and then began flowing gas into their chamber from 0 to 20 min. At the 20 min mark, they zero’ed out their spectra and then began illuminating their samples. So, the adsorption spectra should all be positive peaks showing increases in the adsorption of the molecules as a function of time. The illumination would be positive peaks for new species, negative peaks for loss of species, and zero that show no change. Is that correct? If so, why do they see a negative peak around the 1036 cm-1 for CdS for the adsorption time of CH2OH? This only seems to happen for CdS and not for any of the other samples.\n15. Can the authors explain the changes in the peak envelopes just below 1000 cm-1? What about at 1250 cm-1?\n16. In the ESR spectra for Pt1/CdS under H2O/O2/CH4, why is the highest peak at ~3400G show so little intensity?\nOverall, the quality of the data appears to be quite high but many of their conclusions would have stronger support with further explanation based on the previous points. I’m not convinced that the impact of this paper is all that significant given that there are others who have shown similar results with related systems. It also impacted the perceived novelty of the work. The authors have done a quality job referencing their work and it was easy to access during review.", "reviewer_2": "In the manuscript, authors reported a combined experimental and theoretical work to study the effects of photogenerated charge carrier manipulation in methane-to-methanol conversion by constructing multifunctional active sites. Revealed by TA, in situ XPS, etc., electron and hole were trapped in similar timescale and then further localized on Pt and unsaturated sulfur sites for the spatiotemporal control, realizing the efficiency and highly selective methane conversion. Overall, the novelty of this work is prominent, and it matches with the requirement of Nature Communications. The results presented here provide substantial evidence supporting the proposed conclusions. It is believed that the findings in this work will be of the broad interests to readers in the field of energy materials. However, there are some issues that need to be identified and addressed in the present form.\nMain concerns:\n1.Supplementary Fig. 8 displays the ultra-violet and visible diffuse reflectance spectra of samples, and it is clear that there is additional tail absorption from 500 to 800 nm, which may be associated with Pt. However, in TAS (Fig. 3), authors claimed that the bleach signals in this region should only be ascribed to CdS without considering Pt species. Please explain this phenomenon and supply necessary proof in the manuscript.\n2.As to photodynamics in Fig. 3 d-f, the conclusion “2 at 397.0 ps is only featured with GSB and tail bleach has been completely removed. It demonstrates the hole on interband state is further trapped and 2 should be ascribed to the intrinsic recombination of CdS” needs to be further identified. The recombination of excited electron with trapped hole can also promote the decline of tail bleach, so why 2 was ascribed to band edge recombination and secondary trapping?\n3.In terms of time-resolved spectroscopies, authors claimed the influence of pump laser pulse fluency on photodynamics, which standardized the whole process; simultaneously, it was also noticed that the wavelength of pump laser was set to 400 nm. Why did authors choose this parameter and please explain it in the manuscript.\nOther concerns:\n1.Photodynamics revelations demonstrated the importance of active sites, but authors hardly mentioned the influence of Pt to band structure of photocatalysts. In this case, it is advised to depict the valence band and conduction band position of CdS, Pt1/CdS and Pt2/CdS, which is imperative to discuss carrier behavior from the perspective of thermodynamics.\n2.Apart from the mentioned C1 products, were C2H6 or C2H4 also detected in current system?\n3.HCHO was detected using colorimetric method, the fundamental mechanism of colorimetric method is suggested to be supplied in the manuscript.", "reviewer_3": "In this manuscript, the authors used CdS-supported Pt catalyst to realize the photocatalytic oxidation of methane to methanol, a significant topic. The CH3OH production rate over the optimal catalyst reaches 12.7 μmol-1∙g-1∙min-1 with a selectivity of 83.5%. My comments are given as follows:\n1. What is the oxidant for methane oxidaiton? In the experimental section, the authors only introduced CH4 into the reactor without any oxidant. Did they used some solvent (e.g., H2O) or other sacrificial agent?\n2. The authors used Pt to modify CdS with different contents. What are the structures of 1%Pt/CdS and 2%Pt/CdS? Only one sample was provided in EXAFS spectrum (Fig. 2c) and fitting (Supplementary Table 2). What is the local coordination structure of 2%Pt/CdS?\n3. In Supplementary Table 2, Pt was mistakenly written as \"Pd\". Pt atoms are coordinated with both Cd and S atoms. However, the scheme of the sturcture given in Fig. 2g shows that Pt only coordinates with S atom. I am wondering that how the Pt atoms are anchored with CdS, will Pt atoms replace some Cd, or dop as interstitial atoms?\n4. The catalytic peformance of 1%Pt/CdS and 2%Pt/CdS are strongly different. 2%Pt/CdS tends to catalyze methane to HCHO, CH3OH and CO2, while 1%Pt/CdS favors the selective formation of methanol. What is the reason?\n5. What is the role of Pt for methane oxidation? It seems that the introduction of Pt suppresses the migration of photogenerated carriers (Supplementary Fig. 15). The photocurrent of CdS is much higher than that of 1%Pt/CdS and 2%Pt/CdS. It is contradictory to the most reported cases.\n6. CdS tends to be oxidized under light irradition. The authors should give the data of the spent photocatalyst to verify its stability.\n7. The authors are suggested to test the long-term durality test for 1%Pt/CdS.\n8. In Fig. 6f, the author gave the detailed reaction pathways of 1%Pt/CdS and 2%Pt/CdS for methane converison. I think they should provide more evidences. For example, no signals of O2- radicals were observed in EPR, but which were invloved in the pathway. Same radicals were involved for methane oxidation over Why 1%Pt/CdS and 2%Pt/CdS (OH and O2-), why the reation pathways are greatly different?", "reviewer_4": "The critical mechanism of photocatalytic methane to methanol conversion using Pt-loaded CdS catalysts with special focus on the spatial and temporal distribution of photo-excited charge carriers was systematically investigated in this manuscript. And a clear picture on the correlation between catalyst structure and catalytic performance has been provided, which is important for the catalyst development in the field of green energy utilization. The paper is well written and has a concrete storyline but the following issues need to be stressed before it can be agreed for publication.\n1. There were only two contrast groups in current work, named 1%Pt/CdS and 2%Pt/CdS. It is suggested for authors to make more samples for photocatalytic methane to methanol evaluation.\n2. In the TA tests, why authors added BQ? The purpose needs to be clarified. Besides that, would the addition of such additives change the intrinsic structures of the catalysts? The factors and mechanism should be ruled out.\n3. The time-resolved spectroscopic studies were conducted with the fs-laser pulse and it reflected photodynamics in ultrafast timescale. But authors reckon electron and hole can be further localized on Pt and unsaturated sulfur, of which the corresponding timescale is beyond the time-window of TAS. How did authors deduce this conclusion and the validity of the spectroscopic characterizations related to the catalytic mechanism in general need to be discussed.\n4. As to electrochemical characterizations, was transient photocurrent response tested under open circuit potential? The applied potential should be illustrated in the manuscript.\n5. Since the SVD analysis is still quite new compared with conventional single wavelength kinetic fitting for TA results (Angew. Chem. Int. Ed. 2024, 63, e202401255; Adv. Mater. 2024, 36, 2303287), I suggest the author provide detailed description on how the SVD fitting is implemented and the basic interpretation or theory about the fitting process to facilitate the non-expert readers. Moreover, some expressions need to be checked, e.g. 1Σ excitons in line 200 was also written as 1S excitons, etc. (Adv. Mater. 2014, 26, 2954-2961; Nano Energy 2016, 28, 319-329; ACS Catal. 2022, 12, 10115-10126)."}, "author_response": "Manuscript: NCOMMS-25-21495\nSpatiotemporal control of photon distribution on active sites: Bridging bio-\ninspired methane-to-methanol conversion\nResponse to the Reviewers’ Comments\nReviewer #1\nThe work by Y. Li et. al., focuses on the catalytic conversion of methane to methanol using\nimpregnated nanoparticles of CdS with Pt. The Pt is proposed to exist in different oxidation states\nthat favor conversion of methane to methanol through a temporary adsorption of methane to the\nsurface. I was left with many questions regarding this manuscript that I would hope the reviewers\ncould address.\nReply to reviewer: Thanks for reviewer’s comments. In the revised manuscript, we have re-\nanalyzed the electronic state and coordination environment of Pt species based on the combination\nof the data from XPS, XAFS, XRD, TEM, SAED and in situ DRIFTS CO adsorption probe tests. It\nis found that Pt species in 1%Pt/CdS and 2%Pt/CdS both stay in valence of +2 and are coordinated\nwith S to form Pt-S configurations (see Response 1.2, 1.3, 1.4 and 1.5). The role of Pt in the carrier\ndynamics and reaction paths as well as its stability in photocatalysis have been discussed (see\nResponse 1.8, 1.9, 1.13, 1.14, 1.15 and 1.16). Furthermore, experimental conditions of\ntemperature and humidity have been investigated and discussed for their contributions to ultimate\nperformance (see Response 1.10 and Response 1.12). The constructive comments and\nsuggestions are addressed in detail as follow, and we hope that these alterations could meet your\nexpectation.\nComment 1.1 I was confused by the connection to biomimetics in the abstract of this paper. There\ndoesn’t seem to be any connection to biology in this system (the authors argue that the coordination\nof dioxygen to a diiron center satisfies this connection), however there is little connection to diiron\nor any enzymatic science. The authors are not attempting to do careful synthetic work to create an\nartificial mimic of the active sites used in these systems. If anything, this could be motivated by a\nmore controlled heterogeneous catalysis route similar with what is argued in their first paragraph.\nThe ability to limit the overoxidation of the methane to carbon monoxide through light absorbing\nmaterials is as impactful as the biomimetic route and is likely more relevant to their overall paper.\nI would suggest the authors look at J. Am. Chem. Soc, 2024, 146, 25989-25999 and the references\ntherein for inspiration.\nReply to reviewer: Thanks for reviewer’s comment. We are sorry that our previous descriptions\non photocatalyst design cannot well display our motivation and raise reviewer’s confusion. To\nP\nA\nG\nE\npresent our ideas in a better approach, the inspire of this work is necessarily reclaimed. Methane\nmonooxygenase (MMO) exhibits excellent performance in the bio-catalytic conversion of CH to\n3\nspecifically inspired by the ordered sequence of this MMO catalytic process, rather than its Fe\nactive site structure. This core concept of process-inspired design has been explicitly emphasized\nin the abstract and introduction of the revised manuscript, which is highlighted on Page 2-3.\nComment 1.2 I wouldn’t agree with the author’s statement of a “model” substrate. There are many\npeaks within the XRD and the SAED images that show polycrystalline nanomaterials are present\nin the sample. Although polycrystalline substrates are interesting on their own, these are far from\n“model” substrates. It would be useful for the authors to highlight what areas are Pt and what are\nCdS in their TEM images. A comment or two on the number and distribution of SAED spots would\nalso be helpful. Another question is what is the distribution of particle sizes? Are they all a single\ndistribution? Multi-distribution?\nReply to reviewer: Thanks for reviewer’s comment. Our response to reviewer’s comment are\npresented in detail as follow:\n(1) Naming CdS as a model catalyst\nCdS has been extensively employed as a typical photocatalyst in prior studies owing to its\nsuperior light-harvesting properties and facile surface tunability. Consequently, in the previous\nversion of our manuscript, CdS was named as a model catalyst. In accordance with the reviewer's\nsuggestion, this terminology has been revised to ‘typical photocatalyst’ to more accurately reflect\nits role in demonstrating fundamental reaction principles.\n(2) Size and distribution of Pt nanostructures:\nAs shown in Supplementary Fig. R1, the primary diffraction peaks at around 24.9°, 26.5° and\n28.2° in XRD can be indexed to (100), (002) and (101) of hexagonal CdS (PDF#65-3414), which\nare relatively sharp and narrow. The measurable lattice fringes in HRTEM (Supplementary Fig. R2b)\nincludes typical (100) and (011) of CdS. Selected area electron diffraction (SAED) images\n(Supplementary Fig. R2c) demonstrate the polycrystalline property of substrate materials, where\nthe obvious diffraction rings all correspond to hexagonal CdS crystal. In contrast, no characteristic\npeaks corresponding to Pt metallic nanoparticles or Pt-related composites were detected in the\nXRD, TEM, and SAED patterns of 1%Pt/CdS and 2%Pt/CdS, confirming the high-dispersity of Pt\non the surface of CdS. Combined analysis of XPS and XAFS data demonstrates that Pt exists in\nthe +2 oxidation state and forms Pt-S bonds with CdS. (Detailed discussions on Pt valence and\ncoordination are provided in Response 1.3) Corresponding revisions have been implemented on\nPage 5 line 112 of the revised manuscript with highlighted modifications.\nP\nA\nG\nE\nSupplementary Fig. R1 XRD of CdS, 1%Pt/CdS and 2%Pt/CdS.\nSupplementary Fig. R2 TEM, high-resolution TEM and selected area electron diffraction (SAED)\nimages of CdS a-c, 1%Pt/CdS d-f and 2%Pt/CdS g-i.\nP\nA\nG\nE\nComment 1.3 The arguments made regarding the oxidation state that the Pt is in are difficult to\nfollow. The authors suggest it is some sort of oxidized Pt but say it is not Pt(IV). I do not agree with\nthis assessment based on their available data. First, their Reference 25 clearly put the contribution\nat 72.1 eV as a Pt(II) species, while the contribution at 73.6 eV is most likely a Pt(IV) species (I’m\nleaving out the spin-orbit pair Pt 4f peak for simplicity). This isn’t surprising given the chloroplatinic\n5/2\nacid species heated in aqueous solution is most likely to form Pt (IV) species upon deposition. With\nthe two different available oxidation states, regardless of what formal charge they have, why isn’t\nthere multiple contributions in the XAFS? I wouldn’t expect the different oxidation states to have\nthe same coordination numbers around them. Can the authors explain the lack of structure in their\nXAFS based on the presence of multiple species in the XPS? If the assumption is that all of the Pt\nis at the surface, then the XPS and XANES/XAFS should show similar results.\nReply to reviewer: Thanks for reviewer’s comment and suggestions. In the XPS fitting of last\nversion of manuscript, we referred to several works to identify the possible peaks. Among them,\nthe doublets at 73.6 eV (Pt ) mainly referred to the Pt loaded on the oxide surface (J. Am. Chem.\n7/2\nSoc. 2024, 146, 16363-16368), and this peak might correspond to Pt4+. Pt with +2 valence can be\nfitted at a binding energy of 72.1 eV (Pt ). Due to this mixed valence state, in our last version, we\n7/2\nmainly stated that Pt was in an oxidation state and did not specify its specific valence state.\nHowever, on the suggestion of the reviewers, we examined the fitting of XPS and ultimately\ndetermined that there is only Pt2+ in Pt /CdS and Pt /CdS based on the following considerations.\n1 2\nFirstly, Cl 2p signal was not detected in XPS, indicating that there is no chloroplatinic acid residual\nover material surface (see details in Responses 1.4). Secondly, we analyzed the coordination of\nthe material in combination with XAFS and found that the average environment of Pt in the material\nis unique and not the result of the superposition of multiple coordination structures. Finally, by\nreferring to multiple literatures related to Pt/CdS (Angew. Chem. Int. Ed. 2023, 62, e202306452;\nAngew. Chem. Int. Ed. 2023, 62, e202301239), we found that it was not common to detected Pt4+\non the surface of CdS. Therefore, we refitted the Pt 4f signal of XPS and found that when there is\nonly one couple of doublets, the signal can still be well fitted. The corresponding substance was\nPt2+(Supplementary Fig. R3b). Meanwhile, EXAFS fitting also proves that Pt grows on the surface\nof CdS through Pt-S bonds, and forms a Pt-S coordination structure. Here, we sincerely express\nour gratitude to the reviewers for constructive suggestions. Necessary revisions have been made\nin the corresponding parts of the article (in revised manuscript Page 6 line 132).\nP\nA\nG\nE\nSupplementary Fig. R3 X-ray photoelectron Cd 3d a, Pt 4f b, O 1s c fine spectra of CdS,\n1%Pt/CdS and 2%Pt/CdS.\nComment 1.4 Did the authors observe any Cl in their XPS? It would be useful to increase the size\nof Supplementary Figure 6 and label all peaks in the survey spectra.\nReply to reviewer: Thanks for this comment. To verify the potential presence of residual Cl on the\nsurface of 1%Pt/CdS and 2%Pt/CdS, XPS high-resolution Cl 2p spectra were analyzed. As shown\nin Supplementary Fig. R4, no characteristic peaks assigned to Cl species were observed,\nconfirming the effective elimination of chloroplatinic acid precursor which is the only source of Cl\nspecies. Moreover, to respond reviewer’s comment, XPS full spectra have been enlarged while the\ndetected signals are all labelled, including Cd 4d, Cd 4s, Pt 4f, S 2s and so on. Corresponding\nrevisions have been implemented on Page 6 line 133 of the revised manuscript with highlighted\nmodifications.\nSupplementary Fig. R4 The Cl 2p spectra of CdS, 1%CdS and 2%CdS.\nP\nA\nG\nE\nSupplementary Fig. R5 X-ray photoelectron full spectra of CdS, 1%CdS and 2%CdS.\nComment 1.5 Did the authors take CO DRIFTS spectra without the Pt on their CdS particles? They\nexplain what peaks are not there but it would be useful to explain the peaks that are there. In the\n1% Pt/CdS sample, there is clearly a red shift in the desorption peaks that is not present in the 2%\nPt/CdS sample. Can the authors suggest why and how this is? Why does the peak envelope at\n2050 cm-1 change between the different samples? The peak at ~2200 cm-1 is not the same between\nthe two samples, why is this?\nReply to reviewer: Thanks for this comment. Before responding to reviewer’s questions, we need\nto make more descriptions on CO adsorption/desorption experiment details. Before carrying out\nCO adsorption, inert gas (Ar) was firstly used to purge the impurities on the surface of photocatalyst.\nAfter the purging is completed, CO was introduced into the infrared reactor for adsorption until the\nadsorption saturation is reached. However, in CO adsorption process, the collected IR signal is\nrather complex and non-specific, because the vibration signal of the gaseous CO molecules will\noverlap with the signal of the adsorbed CO molecules. Therefore, it is necessary to further use inert\ngas to purge the material surface to remove the excess gaseous CO molecules and then observe\nthe vibration of the adsorbed CO molecules. During the process of removing gaseous CO\nmolecules, the originally overlapping infrared signals are separated and the deviation of the infrared\nsignal peak can be observed. The phenomenon observed in experiments are illustrated as follow.\nAfter adsorption saturation (Supplementary Fig. R6a), the adsorption signal of gaseous CO\nwas mainly observed on the surface of CdS. In contrast, the infrared signals on the surfaces of\n1%Pt/CdS and 2%Pt/CdS showed complex due to the superposition of multiple vibrations. After\ncontinuous purging with inert gas (Supplementary Fig. R6b), the vibration signals related to CO on\nthe CdS surface disappeared rapidly, while on the surface of 1%Pt/CdS and 2%Pt/CdS, weak CO\nadsorption signals retained at 2110~2104 cm-1, corresponding to the adsorbed CO on Ptδ+.\nHowever, due to the high dispersity of Pt, compared with typical signals (~2084 cm-1), this vibration\nP\nA\nG\nE\nhas changed (Nat. Commun. 2017, 8, 16100; ACS Catal. 2022, 12, 3634-3643). It is speculated\nthat the anchored Pt over CdS could have strong affinity with CO. Ultimately, combining CO\nadsorption/desorption experiments with XPS and XAFS, it can be disclosed that Pt is in the form\nof Pt-S bonds with +2 valence. The revisions have been made in the corresponding parts of the\narticle (in revised manuscript Page 7 line 164).\nSupplementary Fig. R6 CO adsorption a and CO desorption b in-situ DRIFTS of CdS, Pt /CdS\n1\nand Pt /CdS. (These data were smoothed during processing)\nto the different letterings.\nReply to reviewer: Thanks for reviewer’s suggestion. We have revised the caption to well deliver\nthe information in the figure, which is shown in Supplementary Fig. R7. Corresponding revisions\nhave been implemented on Page 8 line 181 of the revised manuscript with highlighted modifications.\nP\nA\nG\nE\nSupplementary Fig. R7 XANES spectra of 1%Pt/CdS and 2%Pt/CdS versus that of Pt foil and\nPtO a; Fourier-transformed k3-weighted EXAFS of 1%Pt/CdS and 2%Pt/CdS versus that of Pt foil\n2\nand PtO b; R-space fitting results for 1%Pt/CdS and 2%Pt/CdS (The R-space data are presented\n2\nwithout phase correction) c; EXAFS wavelet transformation (WT) for Pt foil, PtO , 1%Pt/CdS and\n2\n2%Pt/CdS d; CO adsorption e and desorption f in-situ DRIFTS of 1%Pt/CdS and 2%Pt/CdS (Ar\ngas flow was used to remove extra gaseous CO and the desorption curve was collected after 20\nmin Ar flow); The proposed structure for Pt-S configuration for 1%Pt/CdS and 2%Pt/CdS g.\nComment 1.7 Can the authors explain the shift in the UV-vis DRS spectra for the Pt /CdS at 480\n1\nnm?\nReply to reviewer: Thanks for reviewer’s comments. It is noted that the absorption peak near 480\nnm was shifted to a certain extent in the UV-vis DRS spectra, but this shift is not related to the\nintrinsic absorption change of CdS due to the following analysis. Firstly, as shown in Supplementary\nFig. R8, it can be found that the valence band positions of CdS, Pt /CdS and Pt /CdS are basically\n1 2\nsame. Meanwhile, in TAS, the wavelengths corresponding to the ground state bleaching signals of\nCdS, Pt /CdS and Pt /CdS are consistent (Supplementary Fig. R9), indicating that the absorption\n1 2\nedge of CdS has not moved either. Above results prove that Pt has not changed the band structure\nand intrinsic absorption of CdS. As for the wavelength shift observed the UV-vis DRS spectra, we\nspeculate that the Pt on the surface of Pt /CdS scatters a part of incident light during the diffuse\nA\nG\nE\nreflection process, thereby causing a weak wavelength shift in the absorption signal after\nnormalization.\nSupplementary Fig. R8 XPS valence band spectra of CdS, Pt /CdS and Pt /CdS.\n1 2\nSupplementary Fig. R9 Transient absorption spectroscopy (TAS) where 400 nm beam light was\nused as pump light and a continuous white light ranging from 450 to 700 nm was used as probe\nlight: two-dimensional contour plots of TAS with the associated global fitting results of CdS a,\nPt /CdS b and Pt /CdS c. The diagram exhibiting the excited-state carrier relaxation of CdS d,\n1 2\nPt /CdS e and Pt /CdS f.\n1 2\nP\nA\nG\nE\nComment 1.8 Would the authors expect multiple different relaxation pathways given the different\noxidation states of Pt? Why are they only observing a single Pt pathway?\nReply to reviewer: Thanks to reviewer’s comment. Due to the confirmation of the oxidation state\nand coordination environment of Pt, the role of Pt in relaxation paths was further revealed based\non excited-state dynamics studying. From the perspective of ultrafast photodynamics, when Pt\nspecies was loaded on CdS, the TAS global fitting results showed that extra time-component (~ 3.3\nps) appeared in contrast to CdS, which is associated with electron trapping. Moreover, transient\nphotocurrent response and in-situ XPS demonstrated that electron trapped by Pt are further\nlocalized on photocatalyst surface. For surface reaction, Pt can work as electron-rich center to\npreferably adsorb O for ∙OH formation (O + e- → ∙O -, ∙O - + H+ → ∙OOH, ∙OOH + H+ + e- → ∙OH)\n2 2 2 2\nwhile CH is adsorbed on unsaturated sulfur sites (such as Pt /CdS). In this case, CH OH\n4 1 3\noveroxidation was inhibited.\nComment 1.9 The shifts measured in Figure 4 are very small. They are also shifting with the same\nmagnitude and direction which leads me to wonder if the authors are just measuring a charging\neffect on their samples. If the Pt is accepting an electron and the S is sitting with a long-lived hole\nspecies, then I would expect to see a Pt shifted to lower binding energy with the S shifted to higher\nbinding energy. How were the samples mounted in the XPS spectrometer? Was the spectrometer\nproperly calibrated? There are very few details regarding the photoelectron spectroscopy. It would\nbe good to include this in the main text given its significance.\nReply to reviewer: Thanks for reviewer’s comments and these comments are responded in detail\nas follows:\n(1) The details on the sample preparation and energy calibration for in-situ XPS.\nTo prepare sample for in-situ XPS testing, an amount of photocatalyst was mixed with\nelectroconductive resin to form homogeneous mixture. The mixture was processed by compression\nto prepare a film which was immediately placed on the specimen stage of in-situ XPS spectrometer.\nThe chamber where the sample stage was located was evacuated and then XPS data collection\nwas carried out. XPS in the light field was collected after 5 min monochromatic light irradiation.\nDuring the data collection period, monochromatic light will continue to be shone. Finally, the binding\nenergy of in-situ was calibrated referenced on C 1s at 284.8 eV. The revisions have been made in\nPage 20 line 519 of revised manuscript.\n(2) The overall energy shifts in in-situ XPS\nWe agree with author’s view and it was ever expected to see that the binding energy of S 2p\nP\nA\nG\nE\nwas positively shifted while Pt 4f was negatively shifted. As to current results that XPS spectra are\noverall shifted, we speculated that it is caused by carrier diffusion over photocatalyst surface. Based\non the experimental procedures of in-situ XPS (in revised manuscript Page 20 line 519), XPS in\nthe light field was collected after 5 min irradiation and in that case the dominated carriers could\nrapidly diffuse and influence the overall surface charge distributions. Moreover, Pt is bonded on\nCdS through Pt-S bond, and the carrier diffusions between them could be exaggerated, which\npromote the whole process.\n(3) The minor energy shifts in in-situ XPS\nThe transfer and localization of carriers is a dynamic process that needs to compete with the\nrecombination behavior of carriers. At the time scale that in-situ XPS can characterize, the\nexcitation and recombination of carriers have reached a dynamic equilibrium, and thus the charge\naccumulation that can be observed on the material surface will not be obvious. The binding energy\noffset within the range of 0-0.2 eV is a relatively common value in in-situ XPS tests (Angew. Chem.\nInt. Ed. 2023, 62, E 2022, 18688; Nat. Commun. 2024, 15, 4807). Secondly, for the localization of\nsurface electrons and holes, we also referred to other test results in our research. For example, in\nthe photocurrent test, we found that the electron outflow from the surface of the Pt /CdS working\n1\nelectrode was significantly lower than that of CdS, indicating that the strong electron capture and\nlocalization effect of Pt inhibited the transfer of electrons to the external circuit. Taking the\nphenomenon mentioned above in considerations, we reckoned that the minor energy shift in in-situ\nXPS is acceptable and they can reflect the carrier distribution on photocatalyst surface.\nComment 1.10 At higher temperatures, I would have expected the rate of the reaction to increase\nand therefore more methanol to be observed. Can the authors provide more commentary on why\nthey observe the opposite effect?\nReply to reviewer: Thanks for reviewer’s comment. We are sorry to the unclear descriptions which\nhave raised misunderstanding in last version of manuscript. The contrast experimental\n(Supplementary Fig. R10) were carried out to determine the contributions of experimental factors\n(including light, temperature, O , and CH ) to ultimate performance (photocatalyst was Pt /CdS).\n2 4 1\nAmong them, group “current condition” referred to the best experimental conditions (CH +O +light\n4 2\nat 60°C) which have been used to compare performance between CdS, Pt /CdS and Pt /CdS.\n1 2\nHence, consistent with the reviewer's comment, the activity increased when the temperature was\nraised from 40°C to 60°C under light irradiation. The “current condition” has been revised as “the\nbest conditions (CH +O +light at 60°C)” in Page 20 line 519 of revised manuscript.\n4 2\nP\nA\nG\nE\nSupplementary Fig. R10 The contrast photocatalytic experiment to determine the optimized\nexperimental conditions (photocatalyst was Pt /CdS). Error bars represent standard deviations\n1\nobtained from at least two independent measurements\nComment 1.11 In Figure 5d, were all of the systems characterized in this study or are they putting\nthis in comparison with other work that has been done in the literature? If the latter, they should\nreference where they got all of the data.\nReply to reviewer: Thanks for reviewer’s comment. The contrast experiments (Supplementary Fig.\nR10, Figure 5d in manuscript) were all carried out in our photocatalytic system through selectively\nremoving O , light or CH as well as lowing temperature.\n2 4\nComment 1.12 What is the relationship between relative humidity and the adsorption of water at\nthe different sites on these systems?\nReply to reviewer: Thanks for reviewer’s comments. In response to the reviewers' comments,\nwe explored the influence of humidity on the adsorption sites of H O using in-situ DRIFTS. In our\n2\nphotocatalytic evaluation experiments, the photocatalyst was pre-dispersed in ultrapure water with\na high environmental humidity. Therefore, we firstly characterized the adsorption of H O under high\n2\nhumidity conditions (~83%). As shown in the Supplementary Fig. R11, in contrast to CdS, the H O\n2\nvibration signals over Pt /CdS and Pt /CdS have shifted under high humidity conditions, indicating\n1 2\nthat the adsorption sites of H O have changed. For CdS, it is speculated that since a large amount\n2\nof unsaturated sulfur are enriched on its surface, H O could be adsorbed on the unsaturated sulfur\n2\nsites. While for Pt /CdS and Pt /CdS, the changes in the adsorption sites should be caused by Pt,\n1 2\nas H O has been adsorbed onto Pt sites. Furthermore, as humidity was decreased to a low level\n2\n(~10%), the vibration signals over CdS, Pt /CdS and Pt /CdS are not altered but the signals\n1 2\nP\nA\nG\nE\nintensity drops. This phenomenon illustrates that in low humidity, H O adsorption sites over\n2\nphotocatalyst are still same with that in high humidity, while the amount of adsorbed H O could\n2\ndecrease.\nSupplementary Fig. R11 The adsorption of H O on photocatalyst surface in high humidity a; the\n2\ncontribution of humidity to H O adsorption on photocatalyst surface b. (These data were smoothed\n2\nduring processing)\nComment 1.13 The lack of recognition of multiple Pt oxidation states within the interpretation of\nthe reaction mechanism makes this difficult to grasp what the true nature of the Pt in this scheme.\nWhich of the Pt oxidation states are responsible for the oxygen reduction? Is the Pt being reduced\nduring this process?\nReply to reviewer: Thanks for reviewer’s comment. Based on Response 1.13, we have\ndetermined that only Pt2+ (Pt 4f at ~72.3 eV) over Pt /CdS which is responsible for the oxygen\n7/2 1\nreduction. Moreover, to demonstrate the stability of Pt-S configurations in photocatalysis, XPS of\nused Pt /CdS was tested. Displayed in Supplementary Fig. R12, XPS Pt 4f fine spectra were not\n1\nnegatively shifted while no Pt0 species appeared after photocatalytic reaction, which indicated that\nPt species were not further reduced. The involved contents have been supplemented in Page 13\nline 322 of revised manuscript.\nP\nA\nG\nE\nSupplementary Fig. R12 XPS Pt 4f fine spectra of fresh Pt /CdS a and used Pt /CdS b.\n1 1\nComment 1.14 Can the authors comment more on their subtraction during the DRIFTS experiment\nand be more explicit in how to interpret the data? For example, my interpretation of the peaks is\nthat they have desorbed all species from the heating and then began flowing gas into their chamber\nfrom 0 to 20 min. At the 20 min dark, they zeroed out their spectra and then began illuminating their\nsamples. So, the adsorption spectra should all be positive peaks showing increases in the\nadsorption of the molecules as a function of time. The illumination would be positive peaks for new\nspecies, negative peaks for loss of species, and zero that show no change. Is that correct? If so,\nwhy do they see a negative peak around the 1036 cm-1 for CdS for the adsorption time of CH OH?\nReply to reviewer: Thanks for reviewer’s comments and these comments are responded in detail\nas follows:\n(1) The specific experimental procedures of in-situ DRIFTS\nIn-situ DRIFTS experiments were carried out in a sealed reactor which can place sample and\nallow probe light to transmit. At first, background signals were collected as basic lines to zero out\nthe spectra. Then, the reactant gas (H O+CH + O ) was introduced into the reactor for adsorption.\n2 4 2\nDuring the adsorption process, DRIFTS spectra was constantly collected until the characteristic\nsignals was not growing. Furthermore, the spectra were zeroed out for the second time and the\nsimulated light was turned on. Then DRIFTS spectra were further recorded.\n(2) The information of peaks at ~1036 cm-1\nWe reckon that no signal appeared at around 1036 cm-1 over CdS during adsorption process.\nSpectra at 1036 cm-1 look negative because the signals around it are strongly positive, such as S-\n*CH signal at around 1013 cm-1 and continuous bands from 1035 to 1200 cm-1. The overlapping\nA\nG\nE\nof different signals made 1036 cm-1 seem negative, but it can hardly be regarded as a signal. As to\nwhy this phenomenon was only detected on CdS, we supposed it could be related with surface\nstructure. The unsaturated sulfur over CdS might be beneficial to reactant adsorption so that the\ncontinuous band and S-*CH are both stronger. But unsaturated sulfur sorely can hardly manipulate\n4\nelectron, so that CH selective conversion under light irradiation was inhibited.\nWhat about at 1250 cm-1?\nReply to reviewer: Thanks for reviewer’s comment. The responses are presented in detail as\nfollow:\n(1) The information of peaks at ~1245 cm-1\nThe characteristic peaks at ~1245 cm-1 in DRIFTS are ascribed to (*O-C-O) (Nat.\nCommunications, 2021, 12, 1675) which is associated with CO adsorbed on photocatalysts\n2\nsurface. Additional descriptions on this phenomenon have been made on Page 15 line 355 of\nrevised manuscript to respond reviewer’s comment.\n(2) In-situ DRIFTS below 1000 cm-1\nRestricted attention has been given to the signal below 1000 cm-1 in this work due to these\ntwo main concerns. Importantly, the signals in Infrared fingerprint area (below 1000 cm-1) are\ngenerally complex and overlapping while exhibits poor characteristics. Extracting information in this\nregion is not widely adopted (J. Am. Chem. Soc. 2025, 147, 9134-9146; Angew. Chem. Int. Ed.\n2024, 63, e202408379; Nat. Commun. 2024, 15, 564). On the other hand, sufficient information\nabout CH conversion has been obtained in the region beyond 1000 cm-1, so that a complete CH\n4 4\noxidation path can be built (CH →CH OH→HCHO→CO ) in this case. Accordingly, we presented\n4 3 2\nthe in-situ DRIFTS as Supplementary Fig. R13 show.\nSupplementary Fig. R13 In-situ diffuse reflectance infrared Fourier transform spectroscopy\n(DRIFTS) of CdS a, Pt /CdS b and Pt /CdS c in the atmosphere of CH + O + H O mixture under\n2 1 4 2 2\nlight irradiation: the sample surface has been fully absorbed with reactants before the light\nirradiation (These data were smoothed during processing).\nP\nA\nG\nE\nComment 1.16 In the ESR spectra for Pt /CdS under H O/O /CH , why is the highest peak at\n1 2 2 4\n~3400G show so little intensity?\nReply to reviewer: Thanks for reviewer’s comment. Regarding this issue, we suppose it might be\ncaused by the magnetic field or baseline fluctuations during the testing process (Supplementary\nFig. R14). Although the signal is not obvious at ~3400 G, it can still be determined that ∙OH has\nbeen generated. Firstly, the intensity ratio of four ∙OH EPR signals is about 1:2:2:1, and highest\npeaks should be located at central area, corresponding to signals at around ~3415 G, and ~3430\nG. Secondly, the typical EPR signal are symmetrically distributed in the spectra. As the signal at\naround ~3445 G is found, it can be speculated that another signal should appear at ~3400 G. Finally,\nthe signal interval of ∙OH should strictly follow that A =A = 15 G, and the phenomena detected in\nN H\nour EPR results match with this rule. Based on these results, we determine the formation of ∙OH in\nreaction system.\nSupplementary Fig. R14 The EPR of Pt /CdS in the atmosphere of H O+O +CH (These data\n1 2 2 4.\nwere smoothed during processing)\nP\nA\nG\nE\nReviewer #2\nIn the manuscript, authors reported a combined experimental and theoretical work to study the\neffects of photogenerated charge carrier manipulation in methane-to-methanol conversion by\nconstructing multifunctional active sites. Revealed by TA, in situ XPS, etc., electron and hole were\ntrapped in similar timescale and then further localized on Pt and unsaturated sulfur sites for the\nspatiotemporal control, realizing the efficiency and highly selective methane conversion. Overall,\nthe novelty of this work is prominent, and it matches with the requirement of Nature\nCommunications. The results presented here provide substantial evidence supporting the\nproposed conclusions. It is believed that the findings in this work will be of the broad interests to\nreaders in the field of energy materials. However, there are some issues that need to be identified\nand addressed in the present form.\nReply to reviewer: We are grateful to reviewer for the positive and constructive suggestions. Due\nto space limitations in the previous version of our manuscript, we have not provided a detailed\nexplanation of the testing objectives and procedures for the TA as well as the related analysis. In\nthe revised manuscript, we have expanded this section (see Response 2.1, 2.2 and 2.3).\nFurthermore, band structure of samples is investigated through analyzing XPS valence band\nspectra, demonstrating the consistence of band edge position of CdS, Pt /CdS and Pt /CdS (\n1 2\nsee Response 2.4). Additional analysis of C products is added in the revised manuscript (see\nnecessary descriptions have been added in the manuscript. As follow, the point-to-point responses\nare presented in detail and we hope could meet reviewer’s expectation.\nComment 2.1 Supplementary Fig. 8 displays the ultra-violet and visible diffuse reflectance spectra\nof samples, and it is clear that there is additional tail absorption from 500 to 800 nm, which may be\nassociated with Pt. However, in TAS (Fig. 3), authors claimed that the bleach signals in this region\nshould only be ascribed to CdS without considering Pt species. Please explain this phenomenon\nand supply necessary proof in the manuscript.\nReply to reviewer: Thanks for reviewer’s comment. The TAS signals related to Pt were excluded\ndue to the following reasons. Firstly, in our TAS tests, 400 nm pump light with pulse fluency of ~5\nμJ∙pulse-1∙cm-2 was adopted to excite samples and there was only single exciton dynamics. In this\ncase, Pt of which the unoccupied states are far more than CdS can make scarce contributions to\nTAS. Besides, the BQ-trapping experiments provided additional supports to it (Supplementary Fig.\nR15). The bleach signals at 600 nm were not altered by BQ, and this phenomenon was same over\nCdS, Pt /CdS and Pt /CdS, illustrating this signal is still contributed by CdS rather than Pt. To\n1 2\nP\nA\nG\nE\nrespond reviewer’s comment, the descriptions on these phenomena have been supplemented in\nour revised manuscripts and Supplementary information so that it can enhance reader’s\ncomprehensions (In revised manuscript Page 9 line 215 and revised Supplementary Information\nPage 14 line 129).\nSupplementary Fig. R15 The kinetic decay curves at 600 nm to determine the contribution of p-\nbenzoquinone (BQ) to excited-state carrier relaxation: CdS a, Pt /CdS b, Pt /CdS c.\n1 2\nComment 2.2 As to photodynamics in Fig. 3 d-f, the conclusion “ at 397.0 ps is only featured with\nfurther trapped and  should be ascribed to the intrinsic recombination of CdS” needs to be further\n2\nidentified. The recombination of excited electron with trapped hole can also promote the decline of\ntail bleach, so why  was ascribed to band edge recombination and secondary trapping?\nunder light irradiation, in-situ XPS binding energy is positively shifted, indicating the hole\nlocalization on the surface. Thus, it is reasonable to speculate that the trapped hole are not\nrecombined and they own prolonged lifetime so that can be further transferred and localized on\nunsaturated sulfur site. Moreover, the trapped carrier generally own longer lifetime (ACS Nano\n2021, 15, 2, 2281-2291; Angew. Chem. Int. Ed. 2021, 60, 20811-20816), and the timescale for its\nrecombination could be beyond the time-window of TAS. Taking these factors into consideration,\nwe ascribe  to band-edge recombination process.\nlaser pulse fluency on photodynamics, which standardized the whole process; simultaneously, it\nwas also noticed that the wavelength of pump laser was set to 400 nm. Why did authors choose\nthis parameter and please explain it in the manuscript.\nReply to reviewer: Thanks for reviewer’s comment. According to the steady-state absorption of\nCdS, Pt /CdS and Pt /CdS, the intrinsic absorption for 400 nm proton were prominent over three\n1 2\nP\nA\nG\nE\nsample (Supplementary Fig. R16). Thus 400 nm pump light can well excite the sample to produce\nphotogenerated carriers. Moreover, carriers excited by 400 nm pump light can cool down to band\nedge so that visible probe light can also detect them. Besides, from the perspective of instrument,\n400 nm pump laser source is stable and sufficient over most of laser source, which is the\npreconditions for high-quality TAS signals. Referenced on the reported works, 400 nm pump light\nwere commonly used for CdS-based materials TAS signal collection (J. Am. Chem. Soc. 2023, 145,\n40, 21886–21896; Angew. Chem. Int. Ed. 2023, 62, e202218688; J. Am. Chem. Soc. 2015, 137,\n10224-10230). To illustrate the necessity of 400 nm pump light, additional revisions have been\nsupplemented in revised manuscript (in revised manuscript Page 19 line 485).\nSupplementary Fig. R16 Ultraviolet-visible diffuse and reflectance (UV-vis DRS) spectra of CdS,\nPt /CdS and Pt /CdS.\n1 2\nComment 2.4 Photodynamics revelations demonstrated the importance of active sites, but authors\nhardly mentioned the influence of Pt to band structure of photocatalysts. In this case, it is advised\nto depict the valence band and conduction band position of CdS, Pt /CdS and Pt /CdS, which is\n1 2\nimperative to discuss carrier behavior from the perspective of thermodynamics.\nReply to reviewer: Thanks for reviewer’s comment. The band structure of CdS, 1%Pt/CdS and\n2%Pt/CdS was necessarily investigated through determining the valance band position from XPS.\nAs displayed in Supplementary Fig. R17, the intersection points of the tangent line with the\ncoordinate axis are almost identical among CdS, 1%Pt/CdS and 2%Pt/CdS, illustrating that the\nvalence band position of CdS were not altered with the introduction of Pt. Moreover, in TAS\n(Supplementary Fig. R18), the ground-state bleach signal of CdS, Pt /CdS and Pt /CdS were both\n1 2\nprobed by ~505 nm light, demonstrating their same band gap. Accordingly, we conclude that the\nband structure of substrate materials are not influenced by Pt which mainly plays a role in\nphotogenerated carrier manipulation. To respond reviewer’s suggestion, additional descriptions on\nP\nA\nG\nE\nphotocatalyst band structure have been supplemented in revised manuscript (in revised manuscript\nPage 8 line 195).\nSupplementary Fig. R17 XPS valence band spectra of CdS, Pt /CdS and Pt /CdS a; the\n1 2\nabsorption edge of CdS b; the band structure of CdS, Pt /CdS and Pt /CdS c.\n1 2\nSupplementary Fig. R18 Transient absorption spectroscopy (TAS) where 400 nm beam light was\nused as pump light and a continuous white light ranging from 450 to 700 nm was used as probe\nlight: two-dimensional contour plots of TAS with the associated global fitting results of CdS a,\nPt /CdS b and Pt /CdS c. The diagram exhibiting the excited-state carrier relaxation of CdS d,\n1 2\nPt /CdS e and Pt /CdS f.\n1 2\nP\nA\nG\nE\nComment 2.5 Apart from the mentioned C products, were C H or C H also detected in current\n1 2 6 2 4\nsystem?\nReply to reviewer: Thanks for reviewer’s comment. Supplementary Table R1 summarizes the\nphotocatalytic CH oxidation reactions over CdS and Pt /CdS (X=0.5~2.0) where Pt /CdS exhibited\n4 x 1\nprominent performance in CH OH selective production. To respond reviewer’s suggestions, we\n3\nfurther scrutinized the C products, including C H , C H and CH OH in our system and Pt /CdS\n2 2 6 2 4 3 1\nwas used as photocatalyst. Based on the data recorded in gas chromatograph, no any C products\n2\nhave been found. There results and related discussions have been added to the revised manuscript\n(On page 13 line 305 of revised manuscript).\nSupplementary Table R1 CH conversion rate and product generation rate.\nCH OH production CO production rate\n3 2\nSamples production rate selectivity of\nrate (μmol∙g-1∙min-1) (μmol∙g-1∙min-1)\n(μmol∙g-1∙min-1) CH OH (%)\nPt /CdS 7.65 2.09 0.49 74.8\n0.5\nPt /CdS 12.72 2.13 0.39 83.5\n1.5\nPt /CdS 7.88 2.71 0.41 71.7\ncolorimetric method is suggested to be supplied in the manuscript.\nReply to reviewer: Thanks for reviewer’s comment. HCHO owns electrophilic properties and it can\nreact with pentane-2,4-dione to form colored substances. In the presence of ammonium salts (such\nas ammonium acetate), HCHO undergoes a condensation reaction with pentane-2,4-dione to form\nyellow 3,5-diacetyl-1,4-dihydro-2,6-lutidine (DDL) which has a characteristic absorption peak at 412\nnm (HCHO + pentane-2,4-dione + NH + → DDL + H O). By measuring DDL, HCOH amount can\n4 2\nbe determined. The specific experimental procedures of colorimetric method include: Firstly,\ncolorimetric reagent solution was prepared through dissolving 15 g ammonium acetate, 0.3 mL of\nacetic acid and 0.2 mL pentane-2,4-dione in 95.5 mL deionized water. Secondly, 0.5 mL liquid in\nphotocatalytic reactors and 0.5 mL of colorimetric reagent solution was dissolved in 2.0 mL\ndeionized water, and then maintained at 80°C for 10 mins with water bath. Furthermore, the ultra-\nviolet and visible absorption spectroscopy of the mixed liquid was measure. The absorbance at 412\nP\nA\nG\nE\nnm is proportional to the concentration of HCHO in the liquid. Finally, to well exhibit the procedure\nand mechanism of colorimetric method, we supplemented the contents above in experimental\nsections (In revised manuscript Page 21 line 560).\nP\nA\nG\nE\nReviewer #3\nIn this manuscript, the authors used CdS-supported Pt catalyst to realize the photocatalytic\noxidation of methane to methanol, a significant topic. The CH OH production rate over the optimal\n3\ncatalyst reaches 12.7 μmol∙g-1∙min-1 with a selectivity of 83.5%. My comments are given as follows:\nReply to reviewer: Thanks for pointing out the issues that need to be addressed in the manuscript.\nIn response to reviewer’s concerns with the photostability and the coordination environment of\nphotocatalyst, additional tests have been carried out. In specific, the photocatalytic durability of our\nbest sample was explored by conducting cycle experiments and analyzing the XPS of used sample\n(see Response 3.6 and 3.7). The stable CH OH production and selectivity can be observed in three\n3\nrounds while no photocorrosion was found over used sample. Moreover, the local coordination of\nPt in 2%Pt/CdS was disclosed by fitting data in R-space with a proposed configuration (see\nResponse 3.2 and 3.3). Pt in 2%Pt/CdS is still coordinated with S atom, which is close to that of\n1%Pt/CdS. In addition, the role of Pt in carrier dynamics modulation and reaction path\ndeterminations have been further illustrated (see Response 3.4 and 3.5). As follow, the point-to-\npoint responses have been presented in detail.\nComment 3.1 What is the oxidant for methane oxidation? In the experimental section, the authors\nonly introduced CH into the reactor without any oxidant. Did they used some solvent (e.g., H O)\n4 2\nor other sacrificial agent?\nReply to reviewer: Thanks for reviewer’s comments. For our photocatalytic evaluation\nexperiments, the sealed glass photoreactor was poured photocatalyst-dispersed solution and then\nexhausted with diluted oxygen gas (10 vol% in N gas) and 5 mL CH . The reactants for our\n2 4\nexperiments included O , H O and CH . Among them, O worked as oxidant to promote CH\n2 2 4 2 4\nconversion to CH OH, while H O was used to disperse photocatalyst and provide protons for ∙OH\n3 2\nformation (O + e- → ∙O -, ∙O - + H+ → ∙OOH, ∙OOH + H+ + e- → ∙OH).\n2 2 2\nComment 3.2 The authors used Pt to modify CdS with different contents. What are the structures\nof 1%Pt/CdS and 2%Pt/CdS? Only one sample was provided in EXAFS spectrum (Fig. 2c) and\nfitting (Supplementary Table 2). What is the local coordination structure of 2%Pt/CdS?\nReply to reviewer: Reviewer’s comments are really appreciated. In response to reviewer’s\nsuggestions, the coordination environment of 2%Pt/CdS was investigated through fitting the\nEXAFS in R space as displayed in Supplementary Fig. R19. Pt in 2%Pt/CdS was also coordinated\nwith S (~2.3 Å) in the first shell while only Pt-S contribution could be observed in R space. It is\nspeculated that with the increasing of Pt amount, the coordination environment becomes\nhomogeneous and regular. Necessary revisions have been made on Page 8 line 180 of revised\nP\nA\nG\nE\nmanuscript and Page 37 of revised supplementary information.\nSupplementary Fig. R19 R-space fitting results for 2%Pt/CdS (The R-space data are presented\nwithout phase correction)\nSupplementary Table R2 Curve-fit parameters of Pt L -edge EXAFS of 2%Pt/CdS based on\n3\noptimized crystal model.\nS 2 δ2 E (eV) R (Å) N R-factor\n0 0\nPt-S1 2.22 1.35\n0.98 6.313 0.016\nPt-S2 2.38 2.53\nComment 3.3 In Supplementary Table 2, Pt was mistakenly written as \"Pd\". Pt atoms are\ncoordinated with both Cd and S atoms. However, the scheme of the structure given in Fig. 2g shows\nthat Pt only coordinates with S atom. I am wondering that how the Pt atoms are anchored with CdS,\nwill Pt atoms replace some Cd, or dope as interstitial atoms?\nReply to reviewer: Thanks for reviewer’s comments and these comments are responded in detail\nas follows:\n(1) Optimizing the expression for chemical element\nWe apologize for labelling element Pt as Pd in the last version of manuscript and it is sincerely\nappreciated for reviewer to point it out. In the revised manuscript and Supplementary Information,\nall the contents have been comprehensively checked so that the key points can be accurately\ndelivered to readers.\n(2) The coordination of Pt in 1%Pt/CdS in Fig. 2g\nThe contribution of Pt-Cd was observed in the second shell for 1%Pt/CdS while there is no\nany Pt-Pt of Pt-O contribution. Fig. 2g in the last version of manuscript displayed the coordination\nof Pt in Pt /CdS but the top view can hardly display all details. In this regard, the coordination of Pt\n1\nwas also shown from other views as Supplementary Fig. R20 show. Revisions have been made on\nP\nA\nG\nE\nPage 13 of revised supplementary information.\nSupplementary Fig. R20 The top view and side view of proposed 1%Pt/CdS a and 2%Pt/CdS b\nconfigurations.\n(3) The way that Pt atoms are anchored with CdS\nTo investigate the way that Pt was anchored on CdS, the atomic ratio over CdS, Pt /CdS and\n2\ngradually decreased over Pt /CdS and Pt /CdS, while sulfur ratio was increased. Thus, it can be\n1 2\nconcluded that Pt has replaced a part of Cd to formed Pt-S configuration. The phenomenon also\nmatches with the detected Pt-Cd coordination in the second shell, arising from crystal structure\ndeformation.\nSupplementary Table R3 The Cd, S and Pt atomic ratio on the surface of CdS, 1%Pt/CdS and\n2%Pt/CdS.\nSamples\nCdS 1%Pt/CdS 2%Pt/CdS\nCd 48.1 45.6 43.0\nS 51.9 53.1 54.3\nPt 0 1.3 2.7\nP\nA\nG\nE\nComment 3.4 The catalytic performance of 1%Pt/CdS and 2%Pt/CdS are strongly different.\n2%Pt/CdS tends to catalyze methane to HCHO, CH OH and CO , while 1%Pt/CdS favors the\n3 2\nselective formation of methanol. What is the reason?\nReply to reviewer: Thanks for reviewer’s comment. According to transient absorption\nspectroscopy (in Supplementary Fig. R21) and in-situ XPS (in Supplementary Fig. R22),\nunsaturated sulfur and Pt sites can separately trap hole and electron, then further localizing them\non photocatalyst surface. For Pt /CdS, in-situ EPR indicated that ∙OH formation sites and CH\n1 4\nactivation site are separated, as when CH was introduced into system, the detected ∙OH amount\n4\nwere not decreased (in Supplementary Fig. R23). Then, based on DFT calculation (in\nSupplementary Fig. R24), it can be noted that CH should be preferably anchored on unsaturated\n4\nsulfur sites, which also indicated that O should be reduced over Pt sites to form ∙OH. Such as a\n2\nreaction process is closely like bio-enzyme to catalyze CH to CH OH, and it boosts overall\n4 3\nefficiency. However, over Pt /CdS, the excessive Pt has changed the reaction path. In in-situ EPR,\n2\nthe introduction of CH in system decreased the detected ∙OH amount, illustrating the overlapping\n4\nof CH activation sites and ∙OH formation sites. Considering that Pt has dominated Pt /CdS surface,\n4 2\nCH activation and ∙OH formation could both be carried on Pt sites. Such a process promotes\n3 2\nP\nA\nG\nE\nSupplementary Fig. R21 Transient absorption spectroscopy (TAS) where 400 nm beam light was\nused as pump light and a continuous white light ranging from 450 to 700 nm was used as probe\nlight: two-dimensional contour plots of TAS with the associated global fitting results of CdS a,\nPt /CdS b and Pt /CdS c. The diagram exhibiting the excited-state carrier relaxation of CdS d,\n1 2\nPt /CdS e and Pt /CdS f.\n1 2\nP\nA\nG\nE\nSupplementary Fig. R22 TAS kinetic decay curves at 505 nm of CdS, Pt /CdS and Pt /CdS: the\n1 2\nscatter plots are experimental data and linear plots are the corresponding fitting curves a. Time-\nresolved photoluminescence (TRPL) spectra of CdS, Pt /CdS and Pt /CdS b. A diagram showing\n1 2\nthe carrier distribution on photocatalyst surface c. High-resolution X-ray photoelectron Pt 4f and S\n2p fine spectra in dark and light field: CdS d&g, Pt /CdS e&h and Pt /CdS f&i.\n1 2\nP\nA\nG\nE\nSupplementary Fig. 23 In-situ electron paramagnetic resonance (EPR) spectroscopy of CdS a,\nPt /CdS b and Pt /CdS c under different testing conditions (These data were smoothed during\n1 2\nprocessing).\nSupplementary Fig. 24 In-situ diffuse reflectance infrared Fourier transform spectroscopy\n(DRIFTS) of CdS a, Pt /CdS b and Pt /CdS c in the atmosphere of CH + O + H O mixture: the\n2 1 4 2 2\nsample surface has been fully adsorbed with reactants before the light irradiation (These data were\nsmoothed during processing). Geometry optimized configuration of CH adsorbed on Pt sites d and\n4\nunsaturated sulfur sites e. Schematic diagram illustrating the CH OH production through stepwise\n3\nreaction path f.\nComment 3.5 What is the role of Pt for methane oxidation? It seems that the introduction of Pt\nsuppresses the migration of photogenerated carriers (Supplementary Fig. 15). The photocurrent of\nCdS is much higher than that of Pt /CdS and Pt /CdS.\n1 2\nP\nA\nG\nE\nReply to reviewer: Thanks for reviewer’s comment. Our responses are presented in detail as\nfollows:\n(1) The role of Pt in methane oxidation\nPt mainly works as active site to modulate electron behavior while preferably adsorb O to\n2\nprevent the overlapping of OH formation sites and CH activation sites so that overoxidation can\n4\nbe inhibited. In specific, based on excited-state dynamics studying (Supplementary Fig. R25-R27),\nit is demonstrated that Pt can trap electron in picosecond timescale (~3.3 ps) and further localize\nelectron in the timescale equal to surface reactions. During the surface reaction, O is preferably\n2\nadsorbed on Pt and conversed to OH through electron-injection (see more details in Response\n3.4) while CH is adsorbed and activated on unsaturated sulfur sites. Finally, OH combine with\n4\nactivated CH to form CH OH.\n4 3\n(2) The lower photocurrent intensity over 1%Pt/CdS and 2%Pt/CdS\nThis phenomenon might be induced by strong electron trapping of Pt. In transient photocurrent\nresponse (Supplementary Fig. R27), the positive photocurrent observed over CdS, Pt /CdS and\n2\nlight irradiation. Due to the strong electron trapping of Pt, rapid electron transfer into external circuit\nover Pt /CdS and Pt /CdS was obviously inhibited. Same phenomena were also reported and\n1 2\ndiscussed in recent work (Nat. Sustain. 2024, 7, 1171-1181) which also considered the electron\ntrapping to decreased photocurrent.\nP\nA\nG\nE\nSupplementary Fig. R25 Transient absorption spectroscopy (TAS) where 400 nm beam light was\nused as pump light and a continuous white light ranging from 450 to 700 nm was used as probe\nlight: two-dimensional contour plots of TAS with the associated global fitting results of CdS a,\nPt /CdS b and Pt /CdS c. The diagram exhibiting the excited-state carrier relaxation of CdS d,\n1 2\nPt /CdS e and Pt /CdS f.\n1 2\nP\nA\nG\nE\nSupplementary Fig. R26 TAS kinetic decay curves at 505 nm of CdS, Pt /CdS and Pt /CdS: the\n1 2\nscatter plots are experimental data and linear plots are the corresponding fitting curves a. Time-\nresolved photoluminescence (TRPL) spectra of CdS, Pt /CdS and Pt /CdS b. A diagram showing\n1 2\nthe carrier distribution on photocatalyst surface c. High-resolution X-ray photoelectron Pt 4f and S\n2p fine spectra in dark and light field: CdS d&g, Pt /CdS e&h and Pt /CdS f&i.\n1 2\nP\nA\nG\nE\nSupplementary Fig. R27 Transient photocurrent response of CdS, Pt /CdS and Pt /CdS\n1 2\n(embedding picture shows the enlarged Pt\n2\n/CdS photocurrent image).\nComment 3.6 CdS tends to be oxidized under light irradiation. The authors should give the data of\nthe spent photocatalyst to verify its stability.\nReply to reviewer: Thanks for reviewer’s comments. In response to reviewer’s suggestions, XPS\nof used Pt /CdS was recorded to verify the structural stability of photocatalyst. Typically, the\n1\noxidized CdS should be feathered with the appearance of SO 2- and lattice oxygen signals in XPS.\n4\nand lattice oxygen (ACS Catal. 2024, 14, 10, 7788-7794) at ~ 530.0 eV were both absent over used\nPt /CdS. The prominent signals in S 2p are still indexed to S2- in crystal (2p at ~161.3 eV, 2p\n1 3/2 1/2\nat ~162.5 eV) and unsaturated sulfur (2p at ~162.4, 2p at ~163.6 eV). Above results exclude\n3/2 1/2\nthe photocorrosion and sample’s stability is verified. In revised manuscript, additional descriptions\non XPS of used photocatalyst have been supplemented (in Page 13 line 318 of revised manuscript).\nSupplementary Fig. R28 XPS S 2p for SO 2- a, O 1s b and XPS S 2p for S2- c of fresh Pt /CdS;\n4 1\nXPS S 2p for SO 2- d, O 1s e and XPS S 2p for S2- f of used Pt /CdS.\n4 1\nComment 3.7 The authors are suggested to test the long-term durability test for 1%Pt/CdS.\nReply to reviewer: Thanks for reviewer’s comments. The cycle experiments have been carried\nout in this work to characterize the long-term stability of Pt /CdS. Displayed in Supplementary Fig.\nA\nG\nE\nproduct selectivity are also close, indicating its photocatalytic stability in 360 min. In revised\nmanuscript, additional descriptions on cycle experiments have been supplemented (on Page 13\nline 316 of revised manuscript).\nSupplementary Fig. R29 Photocatalytic CH to CH OH cycle experiments over Pt /CdS: the\n4 3 1\ninfluence of cycle number to CH OH production rate a; the statistic average production rate of\n3\ndifferent products b and photocatalytic products distributions c.\nComment 3.8 In Fig. 6f, the author gave the detailed reaction pathways of 1%Pt/CdS and\n2%Pt/CdS for methane conversion. I think they should provide more evidences. For example, no\nsignals of O - radicals were observed in EPR, but which were involved in the pathway. Same\n2\nradicals were involved for methane oxidation over Pt /CdS and Pt /CdS (∙OH and ∙O -), why the\n1 2 2\nreaction pathways are greatly different?\nReply to reviewer: Thanks for reviewer’s comment. Our responses to reviewer’s comment are\npresented in detail as follows:\n(1) The demonstrations on ∙O - radicals in reaction path.\n2\ncrucial to efficient CH OH formation. As oxidant, O was firstly reduced to O - radicals and then to\n3 2 2\n∙OOH and ∙OH (O + e- → ∙O -, ∙O - + H+ → ∙OOH, ∙OOH + H+ + e- → ∙OH) which is the active\n2 2 2\noxygen species in CH conversion. The above reaction paths were widely considered in previous\n4\nworks (ACS Catal. 2024, 14, 955-964; Angew. Chem. Int. Ed. 2024, 63, e202408379; Nat. Commun.\n2023, 14, 2690). Importantly, although no signal of ∙O - and ∙OOH radicals were observed in EPR,\n2\nwe reckoned it results from the rapid radical hydrogenation and relatively excessive ∙OH signals,\nwhich weakened the signals of ∙O - and ∙OOH. To demonstrate the existence of ∙O - and ∙OOH in\n2 2\nour system, we dispersed samples in aerobic methanol (CH OH + O ) where CH OH can remove\n3 2 3\n∙OH and exaggerate ∙OOH signal. In Supplementary Fig. R30, ∙OOH are all detected over CdS,\nPt /CdS and Pt /CdS. In this case, ∙OOH was only produced through O reduction where ∙O - is the\n1 2 2 2\ninvolved intermediate (O + e- → ∙O -, ∙O - + H+ → ∙OOH). This result demonstrates the participation\n2 2 2\nof ∙O - in photocatalytic CH conversion.\n2 4\nP\nA\nG\nE\nSupplementary Fig. R30 The contrast photocatalytic experiment to determine the optimized\nexperimental conditions (photocatalyst was Pt /CdS). Error bars represent standard deviations\n1\nobtained from at least two independent measurements.\nSupplementary Fig. R31 In-situ electron paramagnetic resonance (EPR) spectroscopy of CdS,\nPt /CdS and Pt /CdS in the conditions of O + CH OH (These data were smoothed during\n1 2 2 3\nprocessing).\n(2) The reaction path discrepancy of Pt /CdS and Pt /CdS\n1 2\nThe discrepancy of reaction paths over Pt /CdS and Pt /CdS might be caused by the\n1 2\ndistribution of unsaturated sulfur and Pt on the surface. Over Pt /CdS, Pt and unsaturated sulfur\n1\nwork in synergy that electron-rich Pt preferably adsorb O to produce ∙OH (O + e- → ∙O -, ∙O - +\n2 2 2 2\nH+ → ∙OOH, ∙OOH + H+ + e- → ∙OH) while hole-rich unsaturated sulfur sites adsorb CH for\n4\nactivation. However, the excessive Pt sites over Pt /CdS have dominated photocatalyst surface so\n2\nthat ∙OH formation and CH activation could both be carried out on electron-rich Pt sites (see more\n4\ndetails in Response 3.4). In that case, ∙OH is still produced through O reduction and the its\n2\nconversion process is identical with Pt /CdS. But ∙OH could further attack CH , leading to the\n1 4\nundesired overoxidation.\nP\nA\nG\nE\nReviewer #4\nThe critical mechanism of photocatalytic methane to methanol conversion using Pt-loaded CdS\ncatalysts with special focus on the spatial and temporal distribution of photo-excited charge carriers\nwas systematically investigated in this manuscript. And a clear picture on the correlation between\ncatalyst structure and catalytic performance has been provided, which is important for the catalyst\ndevelopment in the field of green energy utilization. The paper is well written and has a concrete\nstoryline but the following issues need to be stressed before it can be agreed for publication.\nReply to reviewer: We thank reviewer for the constructive suggestions. In our revised manuscript,\nadditional contrast experiments have been conducted to demonstrate the priority of Pt /CdS in\n1\nphotocatalytic CH to CH OH, and the principle of trapping agents in TAS as well as the mechanism\n4 3\nof kinetic global fitting are also supplemented. In specific, samples of Pt /CdS and Pt /CdS have\n0.5 1.5\nbeen prepared as contrast groups and their photocatalytic CH to CH OH performance are\n4 3\nevaluated (see Response 4.1). According to the photocatalytic performance evaluation, Pt /CdS\n0.5\nand Pt /CdS are both inferior to Pt /CdS, demonstrating the best performance of Pt /CdS in\n1.5 1 1\ncurrent system. Moreover, the mechanism that BQ works as TAS trapping agent and how Pt and\nunsaturated sulfur contribute to photodynamics have been illustrated in detail (see Response 4.2\nand 4.3). Finally, the advantages of SVD global fitting in excited-state dynamics studying are further\npresented so that it can well inspire non-expert readers (see Response 4.5). As follow, the point-\nto-point response are presented in detail.\nComment 4.1 There were only two contrast groups in current work, named 1%Pt/CdS and\n2%Pt/CdS. It is suggested for authors to make more samples for photocatalytic methane to\nmethanol evaluation.\nReply to reviewer: Thanks for reviewer’s comments. Samples of Pt /CdS and Pt /CdS have\n0.5 1.5\nbeen prepared as contrast group and their corresponding photocatalytic CH to CH OH\n4 3\nperformance have been evaluated. As displayed in Supplementary Fig. R32, the overall\nperformance Pt /CdS and Pt /CdS, including CH OH production rate and CH OH selectivity, is\n0.5 1.5 3 3\nstill inferior to marked Pt /CdS, indicating the scare or excessive Pt sites can hardly maximize the\n1\nsynergy of Pt and unsaturated sulfur in photocatalysis. To respond reviewer’s comment, the\nsupplementary experimental results have been added in our revised manuscript (In revised\nmanuscript Page 13 line 309).\nP\nA\nG\nE\nSupplementary Fig. R32 Photocatalytic CH oxidation performance evaluation: the contribution of\nbars represent standard deviations obtained from at least two independent measurements.\nComment 4.2 In the TA tests, why authors added BQ? The purpose needs to be clarified. Besides\nthat, would the addition of such additives change the intrinsic structures of the catalysts?\nReply to reviewer: Thanks for reviewer’s comment. These comments are responded in detail as\nfollows:\n(1) The role of BQ in photodynamics investigation\nBQ is a type of organic molecule where there are two symmetrical ketone functional groups in\ntheir structure (Supplementary Fig. R33), so that BQ exhibit oxidizing properties and it can actively\nattract photogenerated electron, simultaneously facilitating excited carrier relaxation in TAS.\nReflected in TAS results, kinetic decay of electron signals could be accelerated in the circumstance\nthat BQ is adsorbed on photocatalyst. Thus, BQ trapping experiments are widely conducted to\nidentify the contributions of electron to time-resolved spectroscopy and investigate photodynamics\n(J. Phys. Chem. Lett. 2019, 10, 566−573; J. Am. Chem. Soc. 2012, 134, 10337−10340; J. Am.\nChem. Soc. 2018, 140, 7791−7794). In our work, due to the limited influence of BQ on 600 nm TAS\nsignal, we ascribed the tail bleach in TAS to hole-related trapping process, which is importance in\nour photodynamics revelation.\nP\nA\nG\nE\nSupplementary Fig. R34 The structural formula of p-benzoquinone (BQ)\n(2) The influence of BQ on intrinsic structures of the catalysts\nAs to this point, we believed there was restricted influence of BQ on photocatalysts. To\ncommence with, in TAS testing, photocatalysts samples were immersed in BQ solution for trapping\nagent adsorption, and BQ amount is strictly controlled in a low level. Importantly, BQ has been used\nto research CdS-based materials photodynamics and no work found its contributions to catalyst\nintrinsic structure (J. Am. Chem. Soc. 2012, 134, 10337−10340; J. Am. Chem. Soc. 2018, 140,\n7791−7794), which lay a foundation for our experiments. To respond reviewer’s comment, the\nmechanism of BQ trapping have been supplemented in our revised manuscript to enrich the\ncontents (In revised manuscript on Page 19 line 493).\nComment 4.3 The time-resolved spectroscopic studies were conducted with the fs-laser pulse and\nit reflected photodynamics in ultrafast timescale. But authors reckon electron and hole can be\nfurther localized on Pt and unsaturated sulfur, of which the corresponding timescale is beyond the\ntime-window of TAS. How did authors deduce this conclusion and the validity of the spectroscopic\ncharacterizations related to the catalytic mechanism in general need to be discussed.\nReply to reviewer: Thanks for reviewer’s comments. Kinetic decay fitting disclosed that Pt site and\nunsaturated sulfur can separately trap electron (~3.3 ps) and hole (~10.6 ps) in picosecond\ntimescale. However, photocatalytic reduction and oxidation reaction were generally carried out in\nmore than millisecond timescale, and it is difficult to demonstrate that the trapped carrier can have\nsuch a long lifetime and participate in photocatalysis. To fill the blank in this process, a series of\ncharacterizations which are able to unveils the photodynamics in slow timescale have been\nadditionally adopted. For example, TRPL and steady state PL were firstly combined together\n(Supplementary Fig. R35). It was found that TRPL average photoluminescence lifetime of CdS was\nreduced to 49.1 ns with Pt sites formation, while simultaneously steady-state PL intensity drops.\nThus, we concluded that the electron trapped by Pt sites own long lifetime and it returns to ground-\nP\nA\nG\nE\nstate through a non-radiative channel. Furthermore, additional characterizations including in-situ\nXPS and transient photocurrent response (Supplementary Fig. R36) were also carried out. As to\nin-situ XPS, the element binding energy shifts under light irradiation was slightly positive over CdS,\ndemonstrating the hole localization is favorable in this case. While for Pt /CdS and Pt /CdS,\nthe 1 2\nbinding energy shift gradually became negative with the increasing of Pt amount, which illustrates\nthe strong correlation between Pt and surface electron localization. Transient photocurrent\nresponse provided more evidences. The positive photocurrent was detected over CdS, and it\nindicated the electron transfer from working electrode to counter electrode. Noting that due to the\nstrong trapping of Pt, the photocurrent intensity over Pt /CdS and Pt /CdS were remarkably lower\n1 2\nthan CdS, further disclosing the long-lifetime localization of carrier on Pt active sites. Accordingly,\nwe assumed that Pt sites and unsaturated sulfur can separately trap electron and hole in\npicosecond timescale, and further localize carriers on photocatalyst surface so that they could\nparticipate in reactions.\nSupplementary Fig. R35 TAS kinetic decay curves at 505 nm of CdS, Pt /CdS and Pt /CdS: the\n1 2\nP\nA\nG\nE\nscatter plots are experimental data and linear plots are the corresponding fitting curves a. Time-\nresolved photoluminescence (TRPL) spectra of CdS, Pt /CdS and Pt /CdS b. A diagram showing\n1 2\nthe carrier distribution on photocatalyst surface c. High-resolution X-ray photoelectron Pt 4f and S\n2p fine spectra in dark and light field: CdS d&g, Pt /CdS e&h and Pt /CdS f&i.\n1 2\nSupplementary Fig. R36 Transient photocurrent response of CdS, Pt /CdS and Pt /CdS\n1 2\n(embedding picture shows the enlarged Pt\n2\n/CdS photocurrent image).\nComment 4.4 As to electrochemical characterizations, was transient photocurrent response tested\nunder open circuit potential? The applied potential should be illustrated in the manuscript.\nReply to reviewer: Thanks for reviewer’s comments. The transient photocurrent response in this\nwork was tested under open circuit potential (OCP). The open circuit potential (OCP) of working\nelectrode would be observed until the value get relatively stable (the sensitivity was set to 10-4 V).\nCorresponding OCP over CdS, Pt /CdS and Pt /CdS are -0.4103 V, -0.1301 Vand -0.1105 V,\n1 2\nrespectively. The revisions made in experimental sections have been supplemented on Page 20\nline 545 of revised manuscript.\nComment 4.5 Since the SVD analysis is still quite new compared with conventional single\nwavelength kinetic fitting for TA results (Angew. Chem. Int. Ed. 2024, 63, e202401255; Adv. Mater.\n2024, 36, 2303287), I suggest the author provide detailed description on how the SVD fitting is\nimplemented and the basic interpretation or theory about the fitting process to facilitate the non-\nexpert readers. Moreover, some expressions need to be checked, e.g. 1Σ excitons in line 200 was\nalso written as 1S excitons, etc. (Adv. Mater. 2014, 26, 2954-2961; Nano Energy 2016, 28, 319-329; ACS Catal. 2022, 12, 10115-10126).\nReply to reviewer: Thanks for reviewer’s comment. Single wavelength kinetic fitting is a common\nand widely adopted method to analyze kinetic decay, of which the mechanism is relatively simple.\nHowever, for complex system dynamics, single wavelength kinetic fitting is not that efficient\ncompared with SVD global fitting. SVD global analysis is a unified separable nonlinear model which\nP\nA\nG\nE\ncan describe all measurements collected over multiple independent variables. SVD involves\neliminating the less important parts in dataset and producing an accurate approximation data, for\nwhich sufficient exponential decays and their amplitudes will be adopted to fit. Then the feature and\ntimescale of specific dynamic processes can be assigned. In this regard, the photodynamics can\nbe visualized in a more intuitive way. In our revised manuscript, additional description for SVD\nglobal fitting has been supplemented so that it can be well presented to non-expert readers (in\nrevised manuscript Page 9 line 210 and Page 19 line 500). Finally, the expressions that reviewers\nmentioned have been checked and we revise “1Σ excitons” with “1S excitons” (in revised\nmanuscript Page 9 line 206).\nP\nA\nG\nE"}, {"round": 2, "reviewer_comments": {"reviewer_1": "I want to applaud the authors on addressing the concerns outlined. Based on many of their responses I am more supportive of their conclusions but am still not convinced of the impact of their work. There are more concerns with their central conclusion that justifies the impact – that the Pt center is responsible for adsorption of oxygen, and free S groups are responsible for CH4 adsorption. If the authors could provide responses to the following, it may add clarity more clarity to their conclusions:\n1. In the authors response to comment 1.3, they re-fit their XPS spectra and show their new fits in supplementary figure R3. If one looks closely at the Pt 4f spectra for each sample, they will see a change in slope around 74.5 eV and a second contribution to the Pt spectra. This is clearly a multivalent Pt species on the surface and exists for all samples with Pt. The contribution is much smaller, granted, in the 1% species but it there. My concern rests on the author’s central point that the Pt species is acting as this sink of O2 for the mechanism. Which Pt species? Why do they just observe a single pathway in the transient spectroscopy if there are multiple Pt species? Why do they only observe a single Pt species in the XAFS when there are clearly multiple valences in the XPS? In the authors supplementary figure R35, the Pt envelope clearly shows multivalence too. Why isn’t there consistency between the different photoelectron spectra?\n2. Further to the previous point, there is some indication that there could be Cl 2p in the 1% Pt. What were the parameters that the Cl 2p was taken? Did the authors use a larger pass energy to ensure that they could observe small amounts on the surface? The reason for my concern with this is that Cl is often a recombination center when adsorbed on the surface. If the samples are not perfectly clean of Cl, there could be changes to many of the different techniques used in the author’s study – DRIFTS and TAS – to make their central argument.\n3. I do not agree with the comment 1.8 the author’s response. The oxidation and coordination environment are still not confirmed and this convolutes the conclusions from the ultrafast photodynamics experiment. I could accept that a generic Pt species is what creates this behavior but it still isn’t clear to me what the role of the oxidation state is. Perhaps this is irrelevant? If so, will any electron trapping metal provide the same behavior? Do unsaturated S-sites normally adsorb CH4?\n4. What indications are there that there is an explicit Pt-S bond? Is this from the EXAFS?\n5. From comment 1.9, the authors cite Nat. Commun. 2024, 15, 4807 (I tried to find the other references but they were difficult to find due to the authors formatting) as a reference for their small shifts. In that article, those authors do show the expected shifts for electron trapping and hole trapping that was referred to in the initial review. In this work, the authors do not show this phenomenon. Can the authors comment on how they are coming to their conclusion given that they are not observing similar effects from the literature in their photoelectron spectra?\n6. In response to Reviewer 3, the authors claim that the Pt has replaced part of Cd to form the Pt-S configuration. Have the authors considered that the Pt will deposit on top of Cd and attenuate its signal, thus producing a lower Cd:S ratio? Did the authors use appropriate sensitivity values to get their ratios? Is any of the Pt oxidation states of similar size to Cd2+ to replace it in the crystal structure?\n7. The lower photocurrent seems to scale with the amount of Pt. The Pt seems to be acting as a recombination center rather than a reaction site. Can the authors comment on this?", "reviewer_2": "I have carefully read the author's revisions. I think the manuscript is now in an acceptable state and can be published.", "reviewer_3": "All the comments have been addressed, and this manuscript can be accepted with the current version.", "reviewer_4": "The revised manuscipt has been improved and acceptance is suggested."}, "author_response": "Manuscript: NCOMMS-25-21495A\nSpatiotemporal control of photon distribution on active sites: Bridging bio-\ninspired methane-to-methanol conversion\nResponse to the Reviewers’ Comments\nReviewer #1\nI want to applaud the authors on addressing the concerns outlined. Based on many of their\nresponses I am more supportive of their conclusions but am still not convinced of the impact of\ntheir work. There are more concerns with their central conclusion that justifies the impact – that the\nPt center is responsible for adsorption of oxygen, and free S groups are responsible for CH\n4\nadsorption. If the authors could provide responses to the following, it may add clarity more clarity\nto their conclusions:\nReply to reviewer:\nWe are grateful to the reviewer for the positive and appreciative of our work\nand pointing out the issues that need to be solved in the manuscript. In the revised manuscript,\nwe comprehensively analyzed all relevant data to further confirm the electronic state and coordination\nof Pt, conclusively establishing that Pt in both 1%Pt/CdS and 2%Pt/CdS is anchored via Pt-S bonds\nin the valence state of +2 (see Response 1.1, 1.4, and 1.6). Furthermore, we have definitively\ndemonstrated that all Pt-S configurations significantly enhance electron trapping during\nphotodynamics (see Response 1.3). Critically, these findings align with our previous conclusions.\nImportantly, we re-emphasize and provide clear evidence that residual Cl has been completely\nremoved, confirming the thorough elimination of precursors (see Response 1.2). To address the\nreviewer's specific concerns, we have provided detailed supplementary explanations for the\nphenomena observed in in-situ XPS and photocurrent responses (see Response 1.5 and 1.7). The\nconstructive comments and suggestions are addressed in detail as follow, and we hope that these\nalterations could meet your expectation.\nComment 1.1 In the author’s response to comment 1.3, they re-fit their XPS spectra and show\ntheir new fits in supplementary figure R3. If one looks closely at the Pt 4f spectra for each sample,\nthey will see a change in slope around 74.5 eV and a second contribution to the Pt spectra. This\nis clearly a multivalent Pt species on the surface and exists for all samples with Pt. The contribution\nis much smaller, granted, in the 1% species but it there. My concern rests on the author’s central\npoint that the Pt species is acting as this sink of O for the mechanism. Which Pt species? Why do\n2\nthey just observe a single pathway in the transient spectroscopy if there are multiple Pt species?\nWhy do they only observe a single Pt species in the XAFS when there are clearly multiple valences\nin the XPS? In the author’s supplementary figure R35, the Pt envelope clearly shows multivalence\ntoo. Why isn’t there consistency between the different photoelectron spectra?\nReply to reviewer: Thanks for this comment, and these comments are responded in detail\nas follows:\n(1) The doublet peak fitting in XPS\nAddressing the reviewer's observation regarding the slope change near 74.5 eV and potential\nsecondary contribution in Pt XPS spectra, we attribute these features primarily to overlap of Pt 4f\nspin-orbit split signals (3.3 eV splitting) rather than higher-valence Pt species, particularly given the\nsignificant spectral overlap within 74.0-75.0 eV. Simultaneously, Pt is still the minor component (<\n5%) compared with Cd and S. While Pt 4f fine spectra was extended acquisition cycles, the possible\ninterference from background contributions can hardly be ignored, further promoting the possible\nfluctuations of fine spectra at ~74.5 eV. On this basis, we also considered the phenomenon\ndetected in other characterizations. Based on XAFS structural evidence (Supplementary Fig. R1),\nR-space fitting reveals an exclusive Pt-S coordination environment without detectable Pt-O or Pt-\nCl bonds, precluding the existence of Pt4+ species (e. PtO and H PtCl ). Moreover, XPS elemental\n2 2 6\nquantification confirms effective removal of Cl impurities (see more details in Response 1.2), further\nsubstantiating complete elimination of platinum precursors (Supplementary Fig. R2). To avoid data\noverinterpretation, we deliberately constrained the fitting complexity and maintain a couple of\ndoublets. In addition, the complementary analysis of XAFS and XPS data addressing this matter is\ndetailed in Response 1.4.\n(2) The phenomenon observed in transient photodynamics\nRegarding ultrafast dynamics analysis, global fitting of carrier kinetics reveals that both\nPt /CdS and Pt /CdS exhibit exclusively one additional time component (strongly correlated with\n1 2\nelectron trapping as there is no any bleach at 600 nm) compared to pristine CdS (Supplementary\nFig. R3b and Fig. R3c). This confirms Pt-induced rapid electron trapping. Given that the ubiquitous\nPt-S coordination over Pt /CdS and Pt /CdS, we deduce consistent carrier transfer pathways\n1 2\nacross highly dispersed Pt atoms. Therefore, our theoretical calculations and surface reaction\npathway analyses are based on the Pt-S single atom coordination model, wherein Pt localizes\nelectrons to adsorb O (forming ∙OH) while unsaturated sulfur sites localize holes for CH\n2 4\nadsorption.\n(3) The spectra discrepancy between XPS and in-situ XPS\nOwing to the specialized optical configuration required for in-situ XPS measurements, our\nconventional XPS (Supplementary Fig. R4) and in-situ XPS (Supplementary Fig. R5) analyses\nwere conducted on distinct spectrometers (Specific descriptions were provided on page 20 of\nrevised manuscript and page 4 of revised Supplementary Information). To ensure maximal data\nfidelity, conventional XPS spectra underwent deliberately optimized acquisition parameters with\nextended dwell times. Conversely, in-situ XPS focused exclusively on tracking light-induced binding\nenergy shifts, hence employing shorter acquisition cycles that inherently yield noisier spectral\nprofiles.\nSupplementary Fig. R1 XANES spectra of 1%Pt/CdS and 2%Pt/CdS versus that of Pt foil and\nPtO a; Fourier-transformed k3-weighted EXAFS of 1%Pt/CdS and 2%Pt/CdS versus that of Pt foil\n2\nand PtO b; R-space fitting results for 1%Pt/CdS and 2%Pt/CdS (The R-space data are presented\n2\nwithout phase correction) c; EXAFS wavelet transformation (WT) for Pt foil, PtO , 1%Pt/CdS and\n2\n2%Pt/CdS d; CO adsorption e and desorption f in-situ DRIFTS of 1%Pt/CdS and 2%Pt/CdS (Ar\ngas flow was used to remove extra gaseous CO and the desorption curve was collected after 20\nmin Ar flow); The proposed structure for Pt-S configuration over 1%Pt/CdS and 2%Pt/CdS g.\nSupplementary Fig. R2 X-ray photoelectron Cl 2p spectra a and full spectra b of CdS, 1%Pt/CdS\nand 2%Pt/CdS.\nSupplementary Fig. R3 Transient absorption spectroscopy (TAS) where 400 nm beam light was\nused as pump light and a continuous white light ranging from 450 to 700 nm was used as probe\nlight: two-dimensional contour plots of TAS with the associated global fitting results of CdS a,\nPt /CdS b and Pt /CdS c. The diagram exhibiting the excited-state carrier relaxation of CdS d,\n1 2\nPt /CdS e and Pt /CdS f.\n1 2\nSupplementary Fig. R4 X-ray photoelectron Cd 3d a, Pt 4f b, O 1s c fine spectra of CdS,\n1%Pt/CdS and 2%Pt/CdS.\nSupplementary Fig. R5 TAS kinetic decay curves at 505 nm of CdS, Pt /CdS and Pt /CdS: the\n1 2\nscatter plots are experimental data and linear plots are the corresponding fitting curves a. Time-\nresolved photoluminescence (TRPL) spectra of CdS, Pt /CdS and Pt /CdS b. A diagram showing\n1 2\nthe carrier distribution on photocatalyst surface c. X-ray photoelectron S 2p and Pt 4f fine spectra\nin dark and light field: CdS d&g, Pt /CdS e&h and Pt /CdS f&i.\n1 2\nComment 1.2 Further to the previous point, there is some indication that there could be Cl 2p in\nthe 1% Pt. What were the parameters that the Cl 2p was taken? Did the authors use a larger pass\nenergy to ensure that they could observe small amounts on the surface? The reason for my concern\nwith this is that Cl is often a recombination center when adsorbed on the surface. If the samples\nare not perfectly clean of Cl, there could be changes to many of the different techniques used in\nthe author’s study – DRIFTS and TAS – to make their central argument.\nReply to reviewer: Thanks for reviewer’s comments and these comments are responded in detail\nas follows:\nTo definitively confirm the absence of Cl residues and attribute apparent spectral features to\nbaseline artifacts, we provide Cl 2p spectra of pure CdS as a reference alongside Pt/CdS samples\n(Supplementary Fig. R6). Crucially, both Pt /CdS and Pt /CdS exhibit near-identical spectral\n1 2\nprofiles to the Cl-free CdS control, with all observed variations attributable solely to baseline\nfluctuations. This experimental evidence conclusively establishes no detectable Cl residues exist\non Pt/CdS surfaces. For absolute scientific rigor, we explicitly emphasize that any potential residual\nCl falls below the detection threshold of XPS, as verified by direct comparison of unsmoothed\nspectral data.\nSupplementary Fig. R6 Cl 2p spectra extracted from XPS full spectra.\nComment 1.3 I do not agree with the comment 1.8 the author’s response. The oxidation and\ncoordination environment are still not confirmed and this convolutes the conclusions from the\nultrafast photodynamics experiment. I could accept that a generic Pt species is what creates this\nbehavior but it still isn’t clear to me what the role of the oxidation state is. Perhaps this is irrelevant?\nIf so, will any electron trapping metal provide the same behavior? Do unsaturated S-sites normally\nadsorb CH ?\nexclusively monovalent Pt2+ species in Pt-S configurations are uniformly present on both Pt /CdS\n1\nand Pt /CdS. Our ultrafast kinetic analysis reveals that the modified carrier dynamics in CdS\n2\noriginate from a singular electron transfer process – specifically, electron trapping at these Pt2+\nsites. Regarding the reviewer's query on oxidation state effects, the absence of mixed-valence Pt\nin our system directly underpins the observed unified electron transfer pathway.\nRegarding selective CH adsorption at unsaturated sulfur sites, while unsaturated sulfur atoms\n4\nserve as potential active sites, their CH adsorption/desorption behaviors were jointly determined\n4\nby DRIFTS and theoretical calculations (Supplementary Figure R7). In in-situ DRIFTS, during\nreactant adsorption, characteristic vibrational peaks at ~1013 cm-1 emerged uniformly across CdS,\nPt /CdS and Pt /CdS, corresponding to the S-*CH configuration, confirming CH adsorption at\n1 2 4 4\nunsaturated sulfur sites. Moreover, DFT calculations revealed stronger absolute adsorption\nenergies for CH at unsaturated sulfur sites when co-existing with monodisperse Pt atoms,\n4\nindicating thermodynamically favored adsorption. In-situ EPR (Supplementary Figure R8)\ndemonstrated non-overlapping adsorption sites for O and CH on Pt /CdS, that CH adsorbs\n2 4 1 4\npreferentially at sulfur sites, while O migrates to adjacent Pt sites. This spatial separation\n2\nunderpins the proposed dual-active-site mechanism.\nSupplementary Fig. R7 In-situ diffuse reflectance infrared Fourier transform spectroscopy\n(DRIFTS) of CdS a, Pt /CdS b and Pt /CdS c in the atmosphere of CH + O + H O mixture: the\n2 1 4 2 2\nsample surface has been fully adsorbed with reactants before the light irradiation (These data were\nsmoothed during processing). Geometry optimized configuration of CH adsorbed on Pt sites d and\n4\nunsaturated sulfur sites e. Schematic diagram illustrating the CH OH production through stepwise\n3\nreaction path f.\nSupplementary Fig. R8 In-situ electron paramagnetic resonance (EPR) spectroscopy of CdS a,\nPt /CdS b and Pt /CdS c under different testing conditions. (These data were smoothed during\n1 2\nprocessing)\nComment 1.4 What indications are there that there is an explicit Pt-S bond? Is this from the EXAFS?\nReply to reviewer: Thanks for reviewer’s comment. We concluded Pt-S configurations over\nPt /CdS and Pt /CdS referenced on XPS and EXAFS fitting results. Reflected in XPS O 1s, S 2p\n1 2\nand Pt 4f, there is no any lattice oxygen (~530.1 eV) and metallic Pt (~70.6 eV) while only sulfide\ncan be detected, excluding the possible Pt-O and Pt-Pt bonds. Simultaneously, in FT-k3 EXAFS,\nthe dominating peaks over Pt /CdS and Pt /CdS can hardly match well standard Pt foil and PtO ,\n1 2 2\nbut can be well fitted by our proposed configurations where Pt was anchored on CdS through Pt-S\nbond. Taking all these results into consideration, we determined the existence of Pt-S bonds.\nSupplementary Fig. R9 X-ray photoelectron Cd 3d a, Pt 4f b, O 1s c fine spectra of CdS,\n1%Pt/CdS and 2%Pt/CdS.\nSupplementary Fig. R10 X-ray photoelectron S 2p fine spectra of CdS a, 1%Pt/CdS b and\n2%Pt/CdS c.\nSupplementary Fig. R11 XANES spectra of 1%Pt/CdS and 2%Pt/CdS versus that of Pt foil and\nPtO a; Fourier-transformed k3-weighted EXAFS of 1%Pt/CdS and 2%Pt/CdS versus that of Pt foil\n2\nand PtO b; R-space fitting results for 1%Pt/CdS and 2%Pt/CdS (The R-space data are presented\n2\nwithout phase correction) c; EXAFS wavelet transformation (WT) for Pt foil, PtO , 1%Pt/CdS and\n2\n2%Pt/CdS d; CO adsorption e and desorption f in-situ DRIFTS of 1%Pt/CdS and 2%Pt/CdS (Ar\ngas flow was used to remove extra gaseous CO and the desorption curve was collected after 20\nmin Ar flow); The proposed structure for Pt-S configuration over 1%Pt/CdS and 2%Pt/CdS g.\nComment 1.5 From comment 1.9, the authors cite Nat. Commun. 2024, 15, 4807 (I tried to find\nthe other references but they were difficult to find due to the authors formatting) as a reference for\ntheir small shifts. In that article, those authors do show the expected shifts for electron trapping and\nhole trapping that was referred to in the initial review. In this work, the authors do not show this\nphenomenon. Can the authors comment on how they are coming to their conclusion given that they\nare not observing similar effects from the literature in their photoelectron spectra?\nReply to reviewer: Thanks for reviewer’s comment. We are sorry that the inappropriate format of\ncited references, which lead to the difficult searching. Currently, the complete reference information\nand DOI number have been supplied so that they can be correctly found (Angew. Chem. Int. Ed.\n2023, 62, e202218688. 10.1002/anie.202218688; Nat. Commun. 2024, 15, 4807. 10.1038/s41467-\n024-49004-7).\nIn our prior response, the cited references primarily serve to demonstrate that binding energy\nshifts of 0.0 to 0.2 eV are commonly observed during in-situ XPS characterization. However, the\nreferenced systems are all heterojunction materials with well-defined dual phases. In such\nconfigurations, charge carriers tend to accumulate and delocalize preferentially within one phase\nafter crossing the heterojunction interface, resulting in a binding energy increase in one phase and\ndecrease in the other – consistent with the authors' expectations. Conversely, our material does\nnot constitute a conventional heterojunction system, lacking distinct phase separation. The\ncovalent Pt-S bonding facilitates efficient carrier diffusion between Pt and S atoms. Consequently,\nthe observed binding energy shifts are governed by the primary carrier localization sites. For CdS\nand Pt /CdS, unsaturated sulfur sites dominate hole localization, manifesting as positive binding\n1\nenergy shifts under photoexcitation. While for Pt /CdS, excessive Pt sites become the predominant\n2\nlocalization centers, leading to negative binding energy shifts under identical conditions.\nSupplementary Fig. R12 TAS kinetic decay curves at 505 nm of CdS, Pt /CdS and Pt /CdS: the\n1 2\nscatter plots are experimental data and linear plots are the corresponding fitting curves a. Time-\nresolved photoluminescence (TRPL) spectra of CdS, Pt /CdS and Pt /CdS b. A diagram showing\n1 2\nthe carrier distribution on photocatalyst surface c. X-ray photoelectron S 2p and Pt 4f fine spectra\nin dark and light field: CdS d&g, Pt /CdS e&h and Pt /CdS f&i.\n1 2\nComment 1.6 In response to Reviewer 3, the authors claim that the Pt has replaced part of Cd to\nform the Pt-S configuration. Have the authors considered that the Pt will deposit on top of Cd and\nattenuate its signal, thus producing a lower Cd:S ratio? Did the authors use appropriate sensitivity\nvalues to get their ratios? Is any of the Pt oxidation states of similar size to Cd2+ to replace it in the\ncrystal structure?\nReply to reviewer: Thanks for reviewer’s comments and these comments are responded in detail\nas follows:\n(1) Whether Pt deposit on the top of Cd and cause a lower Cd:S ratio\nWe assume that Pt could replace a part of Cd to form Pt-S configuration rather than simply\ndeposition, because it is notice that as Pt amount was increased, Cd amount was decreased while\nS amount was also increased (Supplementary Table R1). This phenomenon indicated that overall\nmetal-to-sulfur radio was changed and original Cd have been extracted. More importantly, if Pt\nwere deposited on CdS surface, it should be expected to see that both S and Cd amount both\ndeclined with Pt amount growing, but this trend was not detected.\n(2) The size of Pt and Cd atom\nReferenced on standard database, the radius of Pt2+ and Pt4+ are ~0.85 Å and ~0.70 Å,\nrespectively, while that of Cd2+ is ~0.92 Å. This phenomenon indicated Pt2+ is more prone to take\nthe place of Cd2+ of CdS to form Pt-S configuration.\nSupplementary Table R1 The Cd, S and Pt atomic ratio on the surface of CdS, 1%Pt/CdS and\n2%Pt/CdS.\nSamples\nCdS 1%Pt/CdS 2%Pt/CdS\nCd 48.1 45.6 43.0\nS 51.9 53.1 54.3\nPt 0 1.3 2.7\nComment 1.7 The lower photocurrent seems to scale with the amount of Pt. The Pt seems to be\nacting as a recombination center rather than a reaction site. Can the authors comment on this?\nReply to reviewer: Thanks for reviewer’s comment. The positive photocurrent indicates the\nelectron transferring from working electrode (made of photocatalyst) to counter electrode (Pt foil)\nunder applied voltage, and it was revealed that the photocurrent intensity of CdS decreased with\nthe growing of Pt amount (Supplementary Fig. R13). Here, we understand the reviewer’s concerns\nwith this phenomenon, that Pt could become the recombination center over photocatalysts. But in\nour work, Pt sites over Pt /CdS and Pt /CdS have been demonstrated the strong trapping for\n1 2\nphotogenerated electron in ultrafast timescale, which is faster than photocurrent formation. In this\nregard, less photogenerated electron could enter the circuit and the observed photocurrent intensity\nwas decreased. Same phenomenon was also reported by Tang et al. (Nat. Sustain. 2024, 7, 1171-\n1181. 10.1038/s41893-024-01401-y) who explored the contributions of metal sites to photocurrent\nintensity.\nSupplementary Fig. R13 Transient photocurrent response of CdS, Pt /CdS and Pt /CdS\n1 2\n(embedding picture shows the enlarged Pt\n2\n/CdS photocurrent image).\nReviewer #2\nI have carefully read the author's revisions. I think the manuscript is now in an acceptable state\nand can be published.\nReply to reviewer:\nWe thank for the Reviewer for the appreciative evaluation of our work.\nReviewer #3\nAll the comments have been addressed, and this manuscript can be accepted with the current\nversion.\nReply to reviewer:\nWe deeply thank the reviewer for this comment.\nReviewer #4\nThe revised manuscript has been improved and acceptance is suggested.\nReply to reviewer:\nWe sincerely appreciate the reviewer’s evaluations and recommended\nacceptance of our work."}, {"round": 3, "reviewer_comments": {"reviewer_1": "I want to thank the authors for their useful discussion on their paper. While I am still not convinced of their interpretation of the photoelectron spectra, I believe this merits publication and scrutiny by the wider community to further investigate their claims.\n• In the HAADF-STEM image, the authors point to several changes in contrast on the 1% Pt/CdS in a single area but it is not distributed across the particle. The same can be said for the 2% Pt/CdS image. Is this a proper representation of the photocatalyst surfaces in each case? I would expect for the 2% Pt/CdS to have double the amount of Pt on the surface, but this doesn’t seem to be the case. Can the authors provide some explanation for this?\n• In the EPR spectra, this change is very small and could be attributed to changes in the background. Did the authors also run the 2% Pt/CdS to observe a starker change in the EPR?\n• Adsorbed CO2 isn’t likely to shift the photoelectron spectra in the way the authors indicate. It is not clear whether the shifts mean anything other than some sort of charging effect. More information on how the samples for photoelectron characterization are mounted in the methods section would be appreciated.\n• Can R14 be split into multiple panels and the data enlarged so that we can see more subtle changes in the XRD spectra? The current presentation is difficult to discern any changes other than major changes in the largest peaks.\nOverall, I think the authors have done a lot of work to address our reviewer comments. The interpretation of the photoelectron spectra still concerns me. There seems to be enough supporting evidence of bulk techniques for the authors claims, but their core argument/interpretation does center on the interaction of Pt with the surface of the CdS particles, thus a surface sensitive characterization technique should be the most supportive of their claims. I would continue with my last comment that it merits publication and that the authors and the field should take the opportunity to investigate this further.", "reviewer_5": "Despite numerous efforts to support the authors’ proposal for unique catalytic sites and charge dynamics, the claim of exclusively monovalent Pt2+ on the surface is not properly demonstrated. The XPS Pt 4f spectra clearly show a shoulder peak possibly for Pt4+. The response to this concern is not convincing. Reviewer #1’s concern about mixed valence is well-founded. In addition, given that H2PtCl6 (Pt4+) is used as the precursor, no explicit reduction step is described and the chemical pathway from Pt4+ to Pt2+ remains unclear. It is also doubtful that Pt species are atomically dispersed in this study since the TEM image of separated Pt atoms are not provided. Therefore, further data analyses and computational simulations should be considered with more solid investigation and proper structural hypothesis.\n1. HAADF-STEM should be carried out to confirm the separated Pt atoms on CdS surface.\n2. The claim that Pt is coordinated with sulfur sites is not convincing. EPR spectra of CdS samples before and after Pt deposition should be provided.\n3. The XPS discussion regarding Figure 4 is not convincing, as all elements appear shifted by the same value. This shift may result from the C 1s (284.8 eV) calibration, which is broad and prone to be shifted.\n4. No standard sample containing Pt-S bond, or other Pt2+ states, is measured and compared in XAS. Analysis on the EXAFS and XANES lacks details, what is the Pt-S model and how does this model fit into the EXAFS spectra?\n5. In Figure 5c, in addition to selectivity, it is essential to report the Faradaic efficiency to evaluate the actual process efficiency. Faradaic efficiency quantifies the percentage of charge carriers effectively used for methane-to-methanol conversion. Selectivity alone does not account for holes consumed in reactions.\n6. To me the reply to reviewer #1’s concerns about photocurrents is not really convincing.\n7. Bandgap evaluation based on IPCE spectra should be carried out.\n8. XRD for all samples after reaction need to be provided.\n9. Literature citations need to be improved proficiently, and the foundation of the concept needs to be cited properly rather than just some recent related papers.", "reviewer_6": "I have carefully reviewed the entire manuscript as well as the exchange between Reviewer 1 and the authors. Overall, I find the conclusions and findings in the paper to be convincing and carefully presented.\nWith regard to the main point of debate—the oxidation state of the Pt species—I did notice a very slight shoulder on the high-binding-energy side of the main Pt²⁺ peak, around 73.6 eV. However, given the generally weak core-level signal of the sample, I would be very cautious about directly assigning this feature to a new Pt species. Several alternative explanations are possible, including surface charging, the presence of surface adsorbates during measurement, or baseline artifacts, as the authors have already pointed out. I therefore agree with the authors that the oxidation state of Pt should be established through complementary characterization methods. Indeed, both XAS and TA studies provide consistent evidence supporting the monovalent nature of the Pt species.\nIn addition, the authors confirmed that there is no residual chloroplatinic acid in the sample, which rules out the major possibility suggested by Reviewer 1.\nIn general, XPS is a highly surface-sensitive technique that can be subject to significant uncertainties, especially when the overall signal intensity is low. To rigorously validate the electronic structure of the target sample, complementary techniques are essential, rather than overinterpreting noisy XPS spectra through curve fitting alone. This is precisely the approach taken by the authors, and I find their response to Reviewer 1 to be convincing and well-reasoned.\nSummary, this manuscript presents a novel innovative concept supported by extensive characterization data. however， before publication, several following issues still need to be addressed.\n1. There appears to be an error in the unit labels within the Fig. 2b and 2c. The unit for vertical coordinate should be the angstrom, symbolized as ‘Å’, not the ampere, which is symbolized as ‘A’. Additionally, adding a detailed legend description to the EXAFS fitting parameters table (Supplementary Table 2-3) is crucial for reflecting the rigor of the data. For example, J.Am.Chem.Soc, 145, 2698-2707.\n2. In Fig. 6, it is recommended to clearly indicate the correspondence between the electron/hole enrichment sites and the reaction pathways, for example, holes are enriched at the S sites while electrons are enriched at the Pt sites.\n3. It is recommended to supplement the test data for apparent quantum efficiency to allow for a more comprehensive evaluation of the photocatalytic efficiency.\n4. It appears that the font or size of “µ” in Fig. 5 is inconsistent with others. It is recommended to optimize its font style and size to ensure visual uniformity.\n5. The paper indicates that the introduction of Pt accelerates the charge carrier recombination rate, yet it enhances the catalytic performance. Does this imply that a longer charge carrier lifetime is not necessarily better?"}, "author_response": "Manuscript: NCOMMS-25-21495\nSpatiotemporal control of photon distribution on active sites: Bridging bio-\ninspired methane-to-methanol conversion\nResponse to the Reviewers’ Comments\nReviewer #1\nI want to thank the authors for their diligence and patience in this review. I do have a few other\nquestions based on their discussions with my colleagues in their response.\n• In the HAADF-STEM image, the authors point to several changes in contrast on the 1% Pt/CdS in a single area but it is not\ndistributed across the particle. The same can be said for the 2% Pt/CdS image. Is this a proper representation of the\nphotocatalyst surfaces in each case? I would expect for the 2% Pt/CdS to have double the amount of Pt on the surface, but this\ndoesn’t seem to be the case. Can the authors provide some explanation for this?\n• In the EPR spectra, this change is very small and could be attributed to changes in the background. Did the authors also\nrun the 2% Pt/CdS to observe a starker change in the EPR?\n• Adsorbed CO2 isn’t likely to shift the photoelectron spectra in the way the authors indicate. It is not clear whether the shifts\nmean anything other than some sort of charging effect. More information on how the samples for photoelectron\ncharacterization are mounted in the methods section would be appreciated.\n• Can R14 be split into multiple panels and the data enlarged so that we can see more subtle changes in the XRD spectra?\nThe current presentation is difficult to discern any changes other than major changes in the largest peaks.\nOverall, I think the authors have done a lot of work to address our reviewer comments. The interpretation of the photoelectron\nspectra still concerns me. There seems to be enough supporting evidence of bulk techniques for the authors claims, but their\ncore argument/interpretation does center on the interaction of Pt with the surface of the CdS particles, thus a surface sensitive\ncharacterization technique should be the most supportive of their claims. I would continue with my last comment that it merits\npublication and that the authors and the field should take the opportunity to investigate this further.\nReply to reviewer:\nWe would like to express our sincere gratitude to the reviewer for the comprehensive evaluation, which has significantly improved the quality of our manuscript.\nRegarding the interpretation of Pt valence states, we fully appreciate the reviewer's thoughtful concerns and the opportunity to refine our analysis for greater rigor. Accordingly, we have revised the descriptions of Pt valence states in the latest version to make them more measured and nuanced (see more details in the revised manuscript). We believe this wording strengthens our core arguments while leaving sufficient space for future researchers to further explore the valence states and functions of Pt based on our work.\nMoreover, point-to-point responses have been made to positively respond the reviewer’s comments. Firstly, we have enriched our descriptions on in-situ XPS and presented more details of experiments and analysis (see response 1.3). Recommended EPR spectra for CdS, 1%Pt/CdS and 2%Pt/CdS have been supplemented (see response 1.2) and XRD of fresh and used samples have been partially enlarged to display the crucial information in a better way (see response 1.4). Moreover, we also give more explanations to HAADF-STEM analysis, which is expected to solve the confusion of reviewer (see response 1.1). Our responses are presented in detail as follow:\nComment 1.1 In the HAADF-STEM image, the authors point to several changes in contrast on the 1% Pt/CdS in a single area but it is not distributed across the particle. The same can be said for the 2% Pt/CdS image. Is this a proper representation of the photocatalyst surfaces in each case? I would expect for the 2% Pt/CdS to have double the amount of Pt on the surface, but this doesn’t seem to be the case. Can the authors provide some explanation for this?\nReply to reviewer: Thanks for reviewer’s comments. This comment will be responded in details\n1\nas follow:\n(1) Explanation for the non-uniform distribution of Pt across the particles.\nIn HAADF-STEM image, the identification of uniformly dispersed Pt atoms primarily relies on\nthe contrast difference. Due to the higher relative atomic mass of Pt compared to Cd and S, Pt\natoms appear brighter in the images. Regarding the reviewer’s question concerning the dispersion\nof Pt, we attribute the absence of observed uniform distribution across the entire particle to two\nmain reasons. Firstly, the highly dispersed Pt atoms exist predominantly as single atoms with\nminimal mutual interference, resulting in a random distribution. This phenomenon is also reported\nin other studies (J. Am. Chem. Soc.145, 13169-13180 (2023)). Secondly, we speculate that this is\nrelated to the thickness of the CdS particles. In the central region of the particles, the increased\ncrystal thickness, combined with the fact that the contrast difference between Pt and Cd is not\n‘absolutely large’, may have prevented HAADF from effectively capturing the relevant signals.\n(2) The explanation on the signals intensity over 2%Pt/CdS.\nWe share the reviewer’s expectation that the 2%Pt/CdS sample should exhibit approximately\ntwice the signal intensity of 1%Pt/CdS sample in the images. However, as the loading amount\nincreases, we cannot assume that interatomic interference grows in a strictly linear manner.\nAlthough XAFS fitting results indicate that Pt in 2%Pt/CdS still exhibits a Pt-S coordination,\nits overall configuration is not identical to that of the 1% Pt sample. This suggests the presence of\ninteractions among Pt atoms, leading to the clustering of some Pt single atoms within certain\nregions in HAADF images. Therefore, the overall dispersion does not directly correlate with the\nnominal loading amount.\nIn summary, HAADF-STEM reveals the high dispersity of Pt over 1%Pt/CdS and 2%Pt/CdS,\nand this result can support the results of XAFS, TEM and etc.\nSupplementary Fig. R1 HAADF-STEM of 1%Pt/CdS a and 2%Pt/CdS b.\nComment 1.2 In the EPR spectra, this change is very small and could be attributed to changes in\n2\nthe background. Did the authors also run the 2% Pt/CdS to observe a starker change in the EPR?\nReply to reviewer: We thank reviewer for this comment. To display the change in EPR, CdS\n1%Pt/CdS and 2%Pt/CdS have been all supplemented in revised Supplementary Information\n(Page 11). As Supplementary Fig. R2 displays, the EPR signals of CdS decline as the loading\namount of Pt is increasing, illustrating that Pt are bonded with unsaturated sulfur which induce\ncrystal defects. The related descriptions for EPR are also supplemented on Page 6 of revised\nmanuscripts.\nSupplementary Fig. R2 EPR of CdS, 1%Pt/CdS and 2%Pt/CdS.\nComment 1.3 Adsorbed CO isn’t likely to shift the photoelectron spectra in the way the authors\n2\nindicate. It is not clear whether the shifts mean anything other than some sort of charging effect.\nMore information on how the samples for photoelectron characterization are mounted in the\nmethods section would be appreciated.\nReply to reviewer: Thanks for reviewer’s comment. We are sorry our previous descriptions on\nXPS calibrations are not clearly presented. It should be emphasized that our in-situ XPS\nmeasurements were conducted under vacuum conditions; therefore, the charge accumulation\nobserved on the material surface should originate from the material itself rather than from other\nexternal processes. Furthermore, during the energy calibration of XPS, we consider that adsorbed\ncarbon species (C 1s 284.8 eV) does not substantially affect the binding energy shift. Accordingly,\nall spectra were calibrated based on this premise, which allowed us to identify the systematic\ndeviation in binding energy. Specifically, as the Pt loading increases, the degree of electron\nlocalization at the material surface is enhanced, leading to an overall negative shift in binding\nenergy across the surface. To better clarify our testing and interpretation procedures, we have\nsupplemented the experimental details related to the in-situ XPS characterization in the revised\nsupplementary information (Page 4), aiming to present the relevant information more\ncomprehensively to readers.\nsubtle changes in the XRD spectra? The current presentation is difficult to discern any changes\nother than major changes in the largest peaks.\nReply to reviewer: Thanks for reviewer’s comment and suggestions. To well present the details of\nXRD, the continuous spectra (from 10 to 70°) have been divided into three panels (23 to 30°, 30 to\n40°, 42 to 55°) where the typical diffraction peaks of as-prepared samples are enlarged. As\nSupplementary Figure R3 displays, the detected diffraction peaks of CdS, Pt /CdS and Pt /CdS\n1 2\ncan be all indexed to hexagonal CdS, while they are stable and not altered after photocatalysis,\nillustrating the crystal stability of photocatalysts. The related descriptions for XRD are also\nsupplemented on Page 13 of revised manuscripts.\nSupplementary Fig. R3 XRD of fresh and used photocatalysts: full spectra a) and partially\nenlarged spectra b).\nThe authors have addressed fully my concerns. Now the manuscript can be accepted for\npublication in Nature Communications.\nReply to reviewer:\nWe extend our sincere gratitude to the reviewer for the thorough scrutiny and acceptance of our work.\n5"}, {"round": 4, "reviewer_comments": {"reviewer_1": "I have no further comments on this manuscript and would like to thank the authors for their discussions"}, "author_response": ""}]

Decision letter