Concentrating and directing energy flow in plasmonic heterostructures for stable and efficient light-driven methane dry reforming

Domain: neuroscience
Published: 2026-02-12
Editorial outcome: minor_revision

Abstract
Methane dry reforming offers a promising approach for converting CH4 and CO2 into valuable syngas, while its application is restricted by catalyst deactivation and carbon deposition. Here, we report a well-designed heterostructured plasmonic photocatalyst consisting of a plasmonically active Ag core and a catalytically active Ir cage selectively grown on the vertices and edges of the Ag core, which preserves strong plasmonic absorption and enables the significant concentration of electromagnetic energy on the Ir cage, as well as the selective dissipation of that energy to generate hot carriers. This heterostructured plasmonic photocatalyst demonstrates long-term stability (300 h), high selectivity (>97%), and much enhanced H2 and CO production in light-driven methane dry reforming. We demonstrate that light-excited hot carriers, coupled with electron-enriched Ir sites, enhance the activation of CO2 and CH4, and facilitate the conversion of *CHx intermediates to *CHO, thereby preventing coke formation and contributing to the high catalytic performance.

Introduction
Dry reforming of methane (DRM; CH4 + CO2 = 2H2 + 2CO) offers a promising pathway to achieve a carbon-cycle economy by converting two potent greenhouse gases, methane (CH4) and carbon dioxide (CO2), into syngas, a highly versatile feedstock for Fischer-Tropsch synthesis to produce value-added lower olefins, gasoline, diesel, and other chemicals, and therefore has attracted increasing attention in recent years1–4. However, the high energy barrier for activating CH4 and CO2 typically requires DRM to operate under high-temperature conditions (700–1000 °C)5,6. This not only results in significant energy consumption and substantial CO2 emissions but also leads to the rapid deactivation of the catalysts due to coking or sintering, consequently hindering the industrialization of DRM7. Therefore, the development of DRM reaction systems that can operate at low temperatures while maintaining high activity and stability remains highly urgent yet continues to face significant challenges8,9.

Plasmonic photocatalysis, typically demonstrated on noble metals such as Au10,11, Ag12,13, and Cu14,15, provides an efficient pathway for light-driven reactions due to the unique localized surface plasmon resonance (LSPR) effect16–18. Noble metal based plasmonic nanostructures, such as Ag nanostars and Au nanotriangles, can localize incident light energy at sharp vertices or edges, forming high-intensity electromagnetic hot-spots19,20. These hot-spots can significantly enhance light absorption, stimulate energetic hot-carrier generation, and induce localized high-temperatures in their vicinity21. As a result, they enable light-driven reactions under considerably milder conditions compared to traditional thermocatalytic processes, using light as the sole energy input22. However, the limited catalytic reactivity of plasmonic noble metals in activating CH4 and CO2 has restricted their applications in light-driven DRM reactions. To address this issue, hybrid plasmonic metal nanostructures that integrate plasmonically active noble metal antenna nanoparticles with catalytically active reactor materials have been developed and demonstrate high photocatalytic efficiency and selectivity for DRM23. For example, Zhou et al. reported a plasmonic photocatalyst consisting of Cu nanoparticle antenna with single-Ru atomic reactor sites on surface which achieved a long-term stability (50 h) and high selectivity (>99%) for DRM under illumination at room temperature24. In light of this inspiring antenna-reactor configuration, to further enhance the photocatalytic efficiency and stability in DRM, controlling and concentrating the LSPR energy flow is critical. Hence, we hypothesized that a hybrid plasmonic antenna-reactor nanostructure that would meet this critical requirement should contain a core plasmonic metal nanoparticle as antenna with a low imaginary dielectric function at the LSPR frequency and the catalytically active metal sites as reactor featured by a high imaginary dielectric function at the LSPR frequency, in which the reactor sites should be selectively located at the hot-spots (typically like vertices or edges) of the core plasmonic antenna nanoparticle25. Such an antenna-reactor nanostructure would have following desired features. (1) The selective growth of catalytically active metal on the vertices or edges of the plasmonic metal core—resulting in a core-cage heterostructure—can effectively avoid the shielding effect commonly observed in conventional fully coated core-shell structures and thus preserve the strong LSPR absorption of the plasmonic metal core; (2) Since the energy dissipation of LSPR through the formation of energetic charge carriers is larger in the material with a larger imaginary dielectric function compared to that with a lower imaginary dielectric function, the above as-proposed antenna-reactor structure—comprising a core with a low imaginary dielectric function and a surrounding cage with a high imaginary dielectric function—would allow for the selective dissipation of the light energy stored in LSPR modes of plasmonic core to generate energetic charge carriers in the cage; (3) Due to the lightning rod effect as well as the near field coupling between cage metal and core metal, the distribution of catalytically active metal at the vertices or edges of the plasmonic metal core would promote the concentration of the electromagnetic energy and enhance the intensity of electromagnetic field at the hot-spots, thereby facilitating molecule activation and chemical transformations.

In this work, we present such an antenna-reactor plasmonic photocatalyst in form of core-cage heterostructure that contains an Ag nanocrystal core serving as the antenna and a Ir cage functioning as the reactor that is grown selectively on the vertices and edges of the Ag core (denoted as Ag@Ir-cage). This plasmonic Ag@Ir-cage heterostructure exhibits strong light absorption and enables efficient directional electron transfer from Ag to Ir. More importantly, it allows for a significant concentration of electromagnetic energy on the surface of the Ir cage and meanwhile facilitates the selective dissipation of the energy for generating hot carriers. As a result, the Ag@Ir-cage achieves a long-term stability exceeding 300 h, and demonstrates high selectivity (>97%) along with favorable H2 and CO production rates (2080 and 2145 mmol g−1 h−1) in photocatalytic methane reforming under the light irradiation with no external heating. With the aid of in-situ characterizations and theoretical calculations, we propose that the enhanced energy efficiency and high coking resistance of the Ag@Ir-cage can be attributed to the combination of the Ag-Ir heterostructure and the efficient generation of hot carriers. This study may offer valuable insights for the rational design of plasmonic photocatalysts, enabling more energy-efficient DRM and other relevant catalysis reactions through the effective utilization of LSPR energy.

Results
Plasmonic Ag@Ir-cages were synthesized by a one-pot thermal decomposition approach using silver nitrate (AgNO3) and iridium acetylacetonate (Ir(acac)3) as Ag and Ir sources, respectively, during which Ag nanocrystals (AgNCs) were firstly formed and subsequently, Ir atoms were selectively grown on the vertices and edges of AgNCs to form the Ir cage structure (Fig. 1a, preparation details please see Methods). The observation by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) shows the uniform dispersion of Ag@Ir-cages with an average size of 8.9 ± 1.2 nm in diameter (Fig. 1b, and Supplementary Figs. 1, 2). As displayed in Supplementary Fig. 3a, the high-resolution transmission electron microscopy (HRTEM) image confirms the Ag cores within Ag@Ir-cages have a high crystallinity, which is also demonstrated by the selected-area electron diffraction (SAED) pattern (Supplementary Fig. 3b). It should be noted that the absence of signal attributable to Ir-based species in the SAED pattern may be related to the ultrathin structure of Ir cages. Figure 1c and Supplementary Fig. 3c, d show the atomic resolution high-angle annular dark-field scanning transmission electron microscopy (AR-HAADF-STEM) images acquired from different individual Ag@Ir-cages. Due to a lager atomic number of Ir (Z = 77) than Ag (Z = 47), Ir atoms would present brighter contrasts than Ag atoms in AR-HAADF-STEM images. It is evident that Ir atoms with brighter contrasts are observed to be selectively distributed on the vertices and edges of AgNC cores, confirming the formation of the Ir cage structure. This conclusion can also be verified by the intensity profile curves (Fig. 1d) and the atomic overlap Gaussian function fitting mapping (Fig. 1e), in which Ir atoms with higher surface intensity are enriched on edges and vertices of the AgNC. To further confirm the formation of Ir cage structure, acid etching was used to remove Ag cores from Ag@Ir-cages. As shown in Supplementary Fig. 4, hollow Ir cages with an edge thickness of ~1 nm are presented. Figure 1f shows a HAADF-STEM image and the corresponding elemental dispersive X-ray spectroscopy (EDS) mappings of an individual Ag@Ir-cage. The spatial distribution of the Ir signal surrounding the Ag core further confirms the formation of Ir cage encapsulating the Ag core. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was employed to determine the weight ratio of Ir:Ag as 1:3.6 for Ag@Ir-cages (Supplementary Table 1). It is worthy of mentioning that such unique Ag@Ir-cage heterostructures with Ir atoms selectively located on vertices and edges of Ag cores would be advantageous for synergistically enhancing plasmon-driven catalysis because the vertices and edges of plasmonic nanostructures typically act as localized hotspots capable of concentrating and coupling hot-carriers and thermal energy to drive chemical transformations26.

Figure 2a shows the X-ray diffraction (XRD) patterns of Ag@Ir-cages and Ag NCs, in which characteristic diffraction peaks corresponding to metallic silver (JCPDS, 04-0783) can be clearly observed. Furthermore, a small peak at around 40.5 degree is observed in the XRD pattern of Ag@Ir-cages, which could be attributed to the diffraction of (111) plane of metallic Ir (JCPDS, 01-88-2342). X-ray absorption spectroscopy (XAS) measurements were employed to investigate the electronic structure and local atomic environment of Ir in Ag@Ir-cages. The Ir L3-edge X-ray absorption near edge structure (XANES) spectra of Ag@Ir-cages, Ir foil, and IrO2 are displayed in Fig. 2b, which shows that the intensity of the white line is ordered as IrO2 > Ag@Ir-cages > Ir foil. This indicates the average valence states of Ir in Ag@Ir-cages are between 0 and +4, suggesting the surface oxidation of Ir cages27. Extended X-ray absorption fine structure (EXAFS) was employed to study the local coordination environment of Ir atoms in Ag@Ir-cages. As shown in Fig. 2c, the Fourier-transformed (FT) Ir L3-edge EXAFS spectrum of Ag@Ir-cages exhibits a dominant peak at ~1.5 Å, which could be attributed to the first-shell Ir−O coordination, further confirming the surface oxidation of Ir cages28. Particularly, a distinct shoulder peak appears between 2.0–3.2 Å, which can be attributed to the combined scattering contributions from higher coordination shells, specifically Ir−Ag and Ir−Ir bonds29. To further resolve the atomic contributions in different coordination shells, wavelet transform (WT) analysis was performed. This approach can provide enhanced resolution by simultaneously visualizing the scattering contributions in both R-space and k-space, allowing for a better distinguishment between the Ir−O, Ir−Ag, and Ir−Ir coordination. As shown in Fig. 2d-f, the WT analysis of Ag@Ir-cages reveals a distinct intensity maximum around 7 Å−1, which could be ascribed to the Ir−O scattering, aligning with the FT-EXAFS results. Furthermore, the WT analysis identifies a scattering signature at R ≈ 2.56 Å for Ag@Ir-cages, which can be attributed to the combined action of Ir−Ir and Ir−Ag coordination. This attribution is grounded in the observation that the peak demonstrates substantial broadening relative to the Ir−Ir scattering peak of Ir metal, which suggests the existence of multiple scattering paths. The presence of Ir−Ag bonds demonstrates the strong electronic interaction between Ag core and Ir cage in Ag@Ir-cages. To further elucidate the quantitative coordination environment of Ir atoms in Ag@Ir-cages, the Ir L3-edge EXAFS spectrum of Ag@Ir-cages was analyzed through multi-shell fitting (Fig. 2g, Supplementary Fig. 5 and Supplementary Table 3). The central Ir atoms exhibit primary coordination with 2.36 oxygen atoms in the first shell with an average bond distance of 2.05 Å. Notably, the second coordination shell demonstrates heterometallic interactions, where each Ir atom coordinates with 1.85 Ir and 1.18 Ag atoms, corresponding to the average bond lengths of 2.73 and 3.09 Å for Ir−Ir and Ir−Ag, respectively. These atomic-level coordination metrics confirm the presence of Ir−Ag coordination motifs, indicative of the interfacial interaction between Ag and Ir.

To further confirm the electronic interaction between Ag and Ir in Ag@Ir-cages, X-ray photoelectron spectroscopy (XPS) was performed. As shown in Fig. 2h and Supplementary Fig. 6, the Ag 3d spectrum of Ag NCs present two peaks at around 367.7 and 373.7 eV, corresponding to the binding energies for Ag3d5/2 and Ag3d3/2 of metallic Ag30. Compared with Ag NCs, the Ag 3d signal of Ag@Ir-cages exhibits a shift toward higher binding energies. This result implies the electron transfer from Ag core to Ir cage at the interface, highlighting the interfacial electronic interaction between them. The electron transfer from Ag to Ir may be related to the higher electronegativity of Ir compared to Ag. This interfacial electronic interaction would be beneficial for the separation and transfer of charge carriers generated via the LSPR excitation of Ag. Theoretical calculations on charge density difference also demonstrate that, there is a significant electron redistribution at the interface of Ag and Ir (Fig. 2i), in which the electron density on Ag atoms exhibits a localized dissipation, while Ir atoms show an obvious electron enrichment feature, suggesting a directional charge migration from Ag to Ir. This is in good line with the XPS results.

As shown in Fig. 3a, Ag NCs exhibit a strong absorption peak ranging from 300 to 600 nm, which can be attributed to the LSPR excitation of Ag. Meanwhile, Ir-cages display a broad absorption in the visible and UV ranges, which is dominated by the interband transitions31–33. Notably, Ag@Ir-cages combine the LSPR absorption from the Ag core and the interband absorption from the Ir cage, thereby demonstrating significantly enhanced light absorption spanning both the UV and visible ranges. Meanwhile, compared with that of Ag NCs, the LSPR peak of Ag@Ir-cages is slightly shifted and broadened, which is probably due to the change in the dielectric environment of Ag cores caused by the coating of Ir cages25,34. Since the surface plasmons on Ag NCs could decay radiatively by emission of luminescence, the photoluminescence (PL) measurements were conducted to investigate the hot-electron transfer behavior within Ag@Ir-cages. As shown in Fig. 3b, Ag NCs exhibit a strong PL spectrum under 400-nm light excitation. By comparison, the PL signal of Ag@Ir-cages is much quenched. This observation implies that hot electrons generated by plasmonic excitation of Ag can be transferred from Ag core to Ir cage, thereby suppressing the recombination of hot carriers and resulting in diminished light emission.

To evaluate the hot-electron-transfer behavior more accurately, femtosecond time-resolved transient (TA) absorption measurements were further performed, in which a 400-nm laser pump was used to ensure the LSPR excitation of Ag. As illustrated in Fig. 3c, d and Supplementary Figs. 7 and 8, the TA spectra of Ag@Ir-cages and Ag NCs display exhibit similar characteristics, including a strong and broad plasmon-bleaching (PB) signal ranging from 460 to 640 nm, as well as two exciton absorption signals located at λ = 450 nm and λ = 650 nm, respectively35. These observations suggest that hot carriers are generated within Ag@Ir-cages and Ag NCs through plasmonic excitation of Ag under 400-nm light irradiation36. Fig. 3e presents the kinetics probed at 650 nm (corresponding to the exciton absorption) for Ag@Ir-cages, which can be fitted by a bi-exponential function. The τ1 time constant is attributed to electron-phonon scattering that relates to the generation rate of local heat, whereas the τ2 time constant originates from the process of charge recombination that is indicative of the lifetime of hot electrons37. Compared with Ag NCs (τ1 = 5.56 ps, and τ2 = 371.19 ps), Ag@Ir-cages exhibits significantly longer τ1 (9.01 ps) and τ2 (882.99 ps). The prolonged τ1 indicates a reduced photothermal conversion efficiency, reflecting that Ag@Ir-cages enable the preferential conversion of light energy harvested through LSPR excitation to hot carriers. Meanwhile, the extended τ2 suggest that the generated hot electrons can be effectively transferred from Ag to Ir within Ag@Ir-cages and therefore affords an increased lifetime.

To shed light on the concentration behavior of electromagnetic energy over Ag NCs, Ir-cages and Ag@Ir-cages, we performed the three-dimensional finite-difference time-domain (FDTD) simulations. The models used for the simulations were built according to the TEM observations. Figure 3g depict the comparative electromagnetic field profiles under 400 nm illumination, where both Ag NC and Ag@Ir-cage exhibits significant near-field enhancement, while the electromagnetic field intensity of Ir-cage is quite weak. As for the Ag NC, photoexcitation induces collective oscillation of conduction electrons, generating localized surface plasmon resonances that amplify the electromagnetic field intensity. Notably, the maximum field enhancement occurs at the vertices of the Ag NC, a characteristic manifestation of the lightning rod effect arising from geometric field focusing. In stark contrast, Ag@Ir-cage demonstrates significantly augmented electromagnetic field intensity, particularly at edge and vertex regions, leading to more plasmonic hotspot generation. Specifically, the electromagnetic field intensity at the vertices of the Ag@Ir-cage is more than 3 and 6 times those of the Ag NC and the Ir-cage, respectively. This significant amplification in electromagnetic field originates from the enhanced lightning rod effect and the near field coupling between Ag and Ir38, where the selective growth of Ir on the edges and vertices of Ag NCs lead to the formation of sharper tips on the nanoparticle and modifies the localized dielectric environment of Ag.

The LSPR excitation-induced hot carrier transfer behavior within Ag@Ir-cage heterostructures was further dynamically investigated by in-situ XPS characterization under light irradiation (380 nm < λ < 800 nm). As shown in Supplementary Fig. 9, the Ag 3d peaks of Ag NCs exhibit a shift toward lower binding energy under light irradiation. This phenomenon can be attributed to the dynamic enrichment of hot electrons on the surface induced by LSPR excitation. The in-situ Ag 3d XPS spectra of Ag@Ir-cages are presented in Fig. 2h, which demonstrate a shift of the signal to lower binding energy upon light irradiation. This finding further corroborates the surface electron enrichment resulting from LSPR excitation of Ag cores. More importantly, the light irradiation also leads to the negative shift of Ir 4f XPS peaks of Ag@Ir-cages (Fig. 3f). This potentially indicates the occurrence of hot-electron transfer from Ag core to Ir cage. Based on the above experimental results and theoretical simulations, we propose that the growth of the Ir cage surrounding the Ag core introduces a plasmon decay pathway through the Ir cage. Furthermore, a significant portion of the electromagnetic energy concentrated within Ag@Ir-cages is dissipated through the thin Ir cage via the generation of energetic hot-carriers, in which hot-electrons are transferred from Ag core to Ir cage.

The performance of Ag@Ir-cages for plasmonic photocatalytic DRM was evaluated under the focused irradiation (18.5 W cm−2) from a 300 W Xe lamp without external heating. For comparison, the performance of Ir-cages and Ag NCs was also tested. Before the measurements, MgAl layered double hydroxide (MgAl-LDH), which is inert for DRM under the present reaction conditions, was employed as a support to disperse the catalysts. As depicted in Fig. 4a, Ir-cages exhibit substantial deactivation of catalytic activity during the 30 h measurement period. This is evidenced by a pronounced decline in H2 production rate from 1741 to 1253 mmol g−1 h−1 and a corresponding decrease in CO production rate from 1785 to 1474 mmol g−1 h−1. Additionally, there is a notable reduction in the H2/CO ratio (selectivity), which decreases from 0.97 to 0.85. The observed reduction in activity agrees with the evidence of coke deposition, as Raman analysis confirms the significant formation of graphitic carbon on the surface of the post-reaction Ir-cages (Fig. 4b). Ag NCs are found to be inert under light irradiation toward DRM, with no detectable products formed (Supplementary Fig. 10), likely attributed to their limited ability to activate CH4. In stark contrast, Ag@Ir-cages demonstrate much higher photocatalytic activity and stability for DRM. Specifically, they achieve initial production rates of 2080 mmol g−1 h−1 for H2 and 2145 mmol g−1 h−1 for CO, respectively, with a H2/CO ratio of 0.97. After 300 h of reaction, only a 12% reduction in the H2 production rate is observed, which could be potentially attributed to the gradually reduced light intensity caused by the Xe lamp aging during the long-term operation (Supplementary Fig. 11). The markedly improved photocatalytic stability of Ag@Ir-cages in comparison to Ir-cages might be related to the Ag-Ir heterostructure and the LSPR induced hot carrier generation, which effectively inhibits the coke deposition: Raman spectroscopy analysis verifies the absence of coke formation on Ag@Ir-cages following 300 h of reaction (Fig. 4b), and meanwhile a carbon balance close to unity is demonstrated (Supplementary Fig. 12). Characterization on the post-reaction Ag@Ir-cages confirms the reduction of Ir species to metallic Ir during the DRM reaction (Supplementary Figs. 13-15). In addition, it should be noted that the H2/CO ratio being slightly less than 1 suggests that the DRM process may involve reverse water-gas shift reactions and other side reactions. Supplementary Table 4 compares the catalytic performance of Ag@Ir-cages with that of some recently reported state-of-the-art catalysts. The data indicate that Ag@Ir-cages exhibit competitive catalytic performance among them.

In the plasmonic photocatalytic process, both photoinduced heating and photoinduced hot-carriers might contribute to surface chemical reactions. To clarify the role of light energy toward DRM, a series of experiments were performed. Firstly, we measured the catalytic activity of Ag@Ir-cages at varying light intensities. As shown in Fig. 4c, d, both the production rate of H2 and the conversion rate of CH4 display an nearly linear relationship with the light intensity. This characteristic is a typical indicator of a photocatalytic process governed by photogenerated charge carriers39,40. However, if the reaction were to proceed solely through photocatalysis without any thermal contribution, this linear relationship would extrapolate to the origin, while such feature is absence in the present reaction system. This implies that, besides the photocatalysis process governing the reaction rate, there is an activation step associated with thermal process in the reaction41. Fig. 4e illustrates the selectivity of DRM over Ag@Ir-cages as a function of light intensity. The selectivity exhibits a monotonic increase with light intensity and approaches approximately 100% at light intensities reaching approximately 18.5 W cm−2. This behavior supports the hot-carrier-mediated mechanism24. Then, we evaluate and compare the thermocatalytic and photocatalytic activities under identical surface temperature conditions, where the temperatures are respectively achieved through external heating and light illumination. Under light illumination of 18.5 W cm−2 without external heating (the surface temperature of the catalyst was measured to be around 425 °C (Fig. 4f)), the photocatalytic production rates of H2 and CO achieve 2080 and 2145 mmol g−1 h−1, respectively. In contrast, as depicted in Fig. 4g, the thermocatalytic DRM process is scarcely initiated at 425 °C and further increasing the reaction temperature even to 580 °C leads to only a negligible improvement in reaction rate. Based on the above results, we conclude that the LSPR-induced hot-carrier generation is the predominant mechanism in light-driven DRM over Ag@Ir-cages, while the photothermal conversion induced local high temperature is also necessary for initiating the reaction. Figure 4h shows the variation of the normalized photocatalytic rate over Ag@Ir-cages as a function of light wavelength. The one-to-one correspondence between the normalized photocatalytic rate and the LSPR absorption of Ag@Ir-cages provides additional evidence supporting that LSPR excitation induced hot-carriers are responsible for the observed catalytic activity of Ag@Ir-cages toward DRM.

To illustrate the CO2 adsorption and activation capacity of MgAl-LDH supported Ag@Ir-cages, CO2 temperature-programmed desorption (CO2-TPD) measurements were performed. As depicted in the CO2-TPD spectra presented in Fig. 5a, both MgAl-LDH supported Ag@Ir-cages and MgAl-LDH supported Ir-cages demonstrate three distinct desorption peaks with the temperature ranges of 50–150 °C, 200–350 °C and 400–650 °C, corresponding to the weak, medium, and strong basic sites on their surface, respectively. It is noteworthy that the strong basic site peak of MgAl-LDH supported Ag@Ir-cages is shifted to a higher temperature by ~13 °C as compared with that of MgAl-LDH supported Ir-cages. This result indicates that MgAl-LDH supported Ag@Ir-cages exhibit a stronger affinity for CO2 adsorption than MgAl-LDH supported Ir-cages. This is likely due to that the electron-enriched Ir atoms on the surface of Ag@Ir-cages provide stronger Lewis-base sites for CO2 adsorption42,43. The strong adsorption of CO2 would facilitate its activation, thereby contributing to the improvement in DRM performance.

To get an in-depth understanding of the DRM process, in-situ Fourier transform infrared (FTIR) measurements were carried out. As shown in Fig. 5b, c, and Supplementary Fig. 16, the bands centered at ca. 3011 and 2347 cm−1 can be ascribed to the C−H deformation vibration of CH4 and C−O stretching vibrations of CO2, respectively43,44. Upon exposure to irradiation, a new absorption band corresponding to *CHxO species emerges at 1072 cm−145,46 and its intensity increases progressively with prolonged irradiation time (Fig. 5d). This finding indicates the dissociation of CH4 into *CHxO species. It is noteworthy that the reaction pathway involving *CHxO species can effectively mitigate coking, thereby enhancing the stability. This is evidenced by the stable catalytic performance of Ag@Ir-cages (Fig. 4a) and the absence of detectable coke formation after a 300 h activity measurement (Fig. 4b). Furthermore, a band at 2160 cm−1 is also observed upon irradiation (Fig. 5b, c), which can be attributed to the stretching vibration of linearly bound CO, suggesting the formation of CO in the reaction47,48. No characteristic peaks belong to *COOH species are detected during the measurement. In addition, in the in-situ FTIR spectra of Ir-cages (Supplementary Fig. 17), a band centered at 1624 cm−1 appears and grows gradually under light irradiation, which could be attributed to the stretching vibrations of C=C bonds49–51, suggesting the formation of carbon species and the fast coke deposition on the catalyst surface. Concurrently, no signals at 1072 cm−1, characteristic of *CHxO species, are detected. These observations are consistent with the significant coke formation observed on Ir-cages during the DRM reaction (Fig. 4b) and their rapid deactivation in catalytic performance (Fig. 4a). Based on the above results, it can be reasonably inferred that the DRM pathway over Ag@Ir-cages proceeds through the following steps: 1) CH4 and CO2 are dissociated into (*CHx + *H) and (*CO + *O), respectively; 2) *CHx subsequently reacts with *O to form *CHxO, which further dissociates into (*CO + *H); 3) *CO desorbs to produce CO, while *H species couple to form H2.

Density functional theory (DFT) calculations were further conducted to offer qualitative insights into the high photocatalytic DRM performance of Ag@Ir-cages, although a complete description of the real catalytic conditions is beyond the present models. Two models, including Ir(111) and Ag-supported Ir(111) (denoted as Ag@Ir(111)), were built based on experimental characterization results (Supplementary Fig. 18) and then the energetics of the elementary steps of the DRM reaction were calculated on the surface of both models (Fig. 5e-h). As shown in Fig. 5e, on the surface of Ag@Ir(111), the change of Gibbs free energy (ΔG) required for the oxidation of *CHx to *CHO (1.24 eV) is much less than that for *CHx cleavage to *C (1.86 eV). This suggests the *CHx→*CHO pathway dominates on Ag@Ir(111), which is consistent with the in-situ FTIR results that show evident signals corresponding to *CHxO species during the DRM reaction (Fig. 5b, d). In contrast, *CHx would prefer to be converted into *C rather than *CHO on the surface of Ir(111), as evidenced by the greater energetic favorability of the *CHx→*C pathway relative to the *CHx→*CHO pathway (Fig. 5g). Furthermore, the subsequent oxidation of *C to *CO on Ir(111) is severely impeded due to a high thermodynamic barrier of 3.24 eV, suggesting the occurrence of carbon deposition. These findings are highly consistent with the in-situ FTIR results, which show evident signals corresponding to carbon species but no detectable signals for *CHxO species, thereby providing a rational explanation for the significant coke deposition and the rapid deactivation observed over Ir-cages during the DRM reaction (Fig. 4a, b). In addition, regarding the dissociation of CO2 on both Ag@Ir(111) and Ir(111), the reaction pathway *CO2 → (*CO + *O) → *CO is energetically more favorable compared to the pathway *CO2 → *COOH → (*CO + *OH) (Fig. 5f, h). This indicates that the former pathway is predominant on both surfaces, which is also supported by the in-situ FTIR results. Considering the more significant reduction in free energy, Ag@Ir(111) demonstrates a greater propensity for driving the conversion of *CO2 to *CO compared to Ir(111). This provides an additional contribution to the significantly enhanced catalytic performance observed for Ag@Ir-cages over Ir-cages (Fig. 4a).

Methods
Chemicals
Sliver nitrate (AgNO3) and butylamine were purchased from Sinopharm Chemical Reagent. Iridium(III) acetylacetonate (Ir(acac)3, 97%) and triphenylphosphine (TPP, 99%) were purchased from Sigma-Aldrich Technology Co., Ltd. Oleylamine (OAm, 80–90%), magnesium (II) nitrate hexahydrate (Mg(NO3)2·6H2O), aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and formamide (CH3NO, 99%) were purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd. Sodium hydroxide (NaOH, 97%), hexane and ethanol were purchased from Shanghai Macklin Biochemical Technology Co. Ltd. All chemicals were used as received without further purifications. Deionized (DI) water (18.2 MΩ·cm at 25 °C) was used in all experiments.

Synthesis of Ag@Ir-cages
In a typical process, 34 mg of AgNO3, 20 mg of Ir(acac)3 and 52 mg of TPP were sequentially added to a three-neck flask containing 6 mL of OAm and heated to 120 °C for 10 min under vacuum. Subsequently, the flask was purged with N2 and the mixture solution was heated to 170 °C for 60 min, after which the solution was further heated to 210 °C for 240 min. After being cooled to room temperature, the product was collected by centrifugation and washed several times with hexane and ethanol for further characterizations.

Synthesis of AgNCs
Typically, 34 mg of AgNO3 and 52 mg of TPP were sequentially added to a three-neck flask containing 6 mL of OAm and heated to 120 °C for 10 min under vacuum. Subsequently, the flask was purged with N2 and the mixture solution was heated to 170 °C for 60 min, after which the solution was further heated to 210 °C for 240 min. After being cooled to room temperature, the product was collected by centrifugation and washed several times with hexane and ethanol for further characterizations.

Synthesis of Ir-cages
Typically, the as-prepared Ag@Ir-cages were dispersed in 20 mL of 0.1 mol/L HNO3 solution via sonication, followed by stirring at room temperature for three days. Subsequently, the Ir-cages were collected by centrifugation and thoroughly washed with DI water for further use.

Synthesis of MgAl-LDH
MgAl-LDH was prepared using a modified method reported previously52. In a typical process, 19 mg of Mg(NO3)2·6H2O and 9 mg of Al(NO3)3·9H2O were added to a beaker containing 20 mL of formamide solution (23 vol.%) and heated to 80 °C for 10 min. During this period, 1.0 M NaOH solution was gradually added to the flask to maintain the pH of about 10 (totally, 12.5 mL of NaOH solution was added). The product was collected by centrifugation, washed repeatedly with DI water and ethanol, and kept in 10 mL of ethanol for subsequent use.

Preparation of MgAl-LDH supported Ag@Ir-cages
The as-prepared Ag@Ir-cage and MgAl-LDH were dispersed in 25 mL of n-butylamine to form a homogeneous suspension. After being stirred at room temperature for 24 h, the catalyst was collected by centrifugation and washed several times with hexane and ethanol to remove excess n-butylamine. Finally, the catalyst was dried overnight at 80 °C under vacuum conditions. The loading amount of Ag and Ir were determined to be 15.4 and 4.1 wt%, respectively, by inductively coupled plasma optical emission spectroscopy (ICP-OES).

Preparation of MgAl-LDH supported Ir-cages
The as-prepared Ir-cages and MgAl-LDH were dispersed in 25 mL of n-butylamine to form a homogeneous suspension. After being stirred at room temperature for 24 h, the catalyst was collected by centrifugation and washed several times with hexane and ethanol to remove excess n-butylamine. Finally, the catalyst was dried overnight at 80 °C under vacuum conditions. The loading amount of Ir was determined to be 5.0 wt% by ICP-OES.

Preparation of MgAl-LDH supported AgNCs
The as-prepared AgNCs and MgAl-LDH were dispersed in 25 mL of n-butylamine to form a homogeneous suspension. After being stirred at room temperature for 24 h, the catalyst was collected by centrifugation and washed several times with hexane and ethanol to remove excess n-butylamine. Finally, the catalyst was dried overnight at 80 °C under vacuum conditions.

Characterizations
Powder X-ray diffraction (XRD) was performed on a Bruker D8 Discover X-ray diffractometer. A JEOL-2100F transmission electron microscope (TEM) and a JEOL JEM-ARM200F scanning transmission electron microscope (STEM) were employed to conduct TEM imaging and energy-dispersive X-ray spectroscopy (EDS) elemental mapping on the samples. The surface intensity image was generated by ImageJ (version 1.53k). In-situ X-ray photoelectron spectroscopy (XPS) analysis was performed under light irradiation (380 < λ < 800 nm) and in the dark using a Thermo Fisher Scientific ESCALAB 250Xi photoelectron spectrometer equipped with a 300 W Xe lamp as simulated solar light source. During the XPS measurements conducted under light irradiation, the XPS spectra of the sample were recorded while the sample was simultaneously exposed to the visible light irradiation (Supplementary Fig. 19a). During the XPS measurements performed in the dark, the XPS spectra were collected without the visible light irradiation on the sample (Supplementary Fig. 19b). The UV-visible absorption spectra were measured on an UV-Vis spectrophotometer (UV-1800; Shimadzu, Japan). The steady-state photoluminescence (PL) spectra were obtained at room temperature using a FLSP920 fluorescence spectrometer (Edinburgh Instruments Ltd, UK). ICP-OES measurements were conducted on an Agilent 5110 system ICP-OES analyzer. Raman spectra were recorded on a LabRAM HR Evolution (HORIBA) spectrometer. Thermogravimetric Analysis (TGA) was performed on a METTLER TOLEDO thermal analysis system (TGA/DSC3+). X-ray absorption fine structure (XAFS) measurements were conducted at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility (SSRF). The XAFS data were analyzed with the ATHENA and ARTEMIS code according to the standard procedures, including normalization, background removal and Fourier transformation.

Catalytic performance measurements
The methane dry reforming (DRM) performance was measured at ambient pressure in a flow reactor with a quartz window at the top of the reactor for light exposure (Supplementary Figs. 20 and 21). Prior to each measurement, 5.0 mg of the MgAl-LDH supported catalyst was uniformly placed in the sample holder of the reactor with a diameter of 6 mm. Then, reaction gas (50% CH4/50% CO2) was continuously fed into the reactor at a flow rate of 20 mL min−1. A 300 W Xe lamp (MC-PF300C, Merry Change light) equipped with a focusing lens was used as a light source to drive the DRM reaction. The quantities of CO and H2 were determined by an on-line gas chromatography (GC, Scion 456i, Techcomp Co., LTD) equipped with thermal conductivity (TCD) and flame ionization detectors. The surface temperatures of the catalyst under illumination were recorded using a K-type thermocouple. For wavelength-dependent experiments, the reaction temperature was maintained at 550 °C using a temperature controller and the monochromatic light of 380, 405, 420, 480, 532, 600, and 660 nm wavelengths, with a bandwidth of ±10 nm, were obtained using a set of band pass filters.

The production rates of H2 (rH2) and CO (rCO) and the reaction rates of CH4 (rCH4) and CO2 (rCO2) were defined as follows:
rH2 = CoH2 × Fout × 60 / (Vm × m) (1)
rCO = CoCO × Fout × 60 / (Vm × m) (2)
rCH4 = (CiCH4 × Fin − CoCH4 × Fout) × 60 / (Vm × m) (3)
rCO2 = (CiCO2 × Fin − CoCO2 × Fout) × 60 / (Vm × m) (4)
where, CiCH4 and CiCO2 are the concentrations (vol%) of CH4 and CO2 in the stream of inlet, respectively; CoCH4 and CoCO2 are the concentrations (vol%) of CH4 and CO2 in the stream of outlet, respectively; Fout and Fin indicate the gas flow rates (ml min−1) of inlet and outlet, respectively; Vm means the gas molar volume under standard conditions; and m represents the mass of catalyst.

The reaction selectivity was defined as follows:
Selectivity = rH2 / rCO (5)

The carbon balance rate was calculated by the Eq. (6):
Carbon balance rate = (CoCO × Fout + CoCH4 × Fout + CoCO2 × Fout) / (CiCH4 × Fin + CiCO2 × Fin) (6)

CO2-temperature-programmed desorption measurements (CO2-TPD)
CO2-TPD experiments were conducted on a temperature-programmed desorption instrument (JW-HX100, Beijing JWGB Instrument Co., Ltd.) with a TCD detector. Firstly, 50 mg sample was treated under a He atmosphere at a flow rate of 30 mL min−1 at 400 °C for 1 h. After the sample was cooled to 50 °C, the gas was switched to 10% CO2/He for 1 h and then the sample was purged with pure He for 1 h at the same temperature. Finally, the sample was heated from 50 to 700 °C at 10 °C min−1 under a He atmosphere at a flow rate of 30 mL min−1 and the gas signal was detected by a TCD detector.

In-situ Fourier transform infrared measurements (In-situ FTIR)
In-situ FTIR were conducted on a Bruker Invenio-S FTIR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector. Xe lamp was employed as the light source. Before the measurement, the fresh catalyst was first purged with N2 at 600 °C for 60 min to remove impurities. Then, the fresh catalyst was placed in a 50% CH4/50% CO2 gas stream to collect FTIR spectra for CO2 and CH4 adsorption. After saturation of adsorption, the catalyst was exposed to illumination and the FTIR spectra were recorded at 0, 1, 3, 5, 10, 20, 30, 40, 50, and 60 min. The spectrum detected before illumination was used as the background.

Transient absorption (TA) measurements
Femtosecond transient absorption measurements were performed following a similar procedure reported previously53. A femtosecond laser (1030 nm wavelength, 50 kHz, pulse width < 190 fs, Pharos, Light Conversion) was used as the source beam, 90% of which was converted by an optical parametric amplifier (OPA, Orpheus-HP, Light Conversion) to a 400 nm pump excitation (pulse duration of ~120 fs), while the rest was served as the probe beam for transient absorption measurements. In the TA spectrometer TA100 (Time-Tech Spectra), both the pump beam and the probe beam were fed into the optical bench. At 380 to 720 nm, the probe beam was focused on the sapphire crystal, producing continuous white light. As for the pump beam, the frequency of the chopper was set to 2.5 kHz and the energy attenuation of the pump pulse at 400 nm excitation was about 64 μJ/cm2. The time delay between pump-probe pulses was regulated by a computer-controlled optical delay stage. Both pump and probe pulses were focused and overlapped on the sample layer, which was spin-coated on a 1 mm thick quartz glass. Transient absorption spectra were obtained by the software by collecting and analyzing the white light spectrum of the probe passing through the sample with and without the pump beam.

Finite-difference time-domain (FDTD) simulations
Computational simulations were performed by using the FDTD method with perfectly matched layer boundary conditions. In the simulations, a plane wave with a wavelength of 400 nm was incident perpendicular to the surface of the nanostructures. In addition, the external region was set as an absorbing boundary condition to avoid boundary reflection. Mesh with sufficient accuracy was applied to ensure that reliable computational results were obtained. Finally, the electric field distribution of the nanoparticles under light irradiation was calculated by using the frequency domain solver.

Density functional theory (DFT) calculations
Density functional theory with D3 dispersion correction (DFT+D3) calculations were carried out using the Vienna Ab-initio Software Package (VASP) with Perdew-Burke-Emzerhof (PBE) exchange-correlation functional, following a protocol similar to that reported previously54. According to our experimental observations, Ag(111) and Ir(111) surfaces were constructed using 4 × 4 × 1 supercells and they were combined to model the Ag-Ir heterostructure, where Ir atoms served as the surface active sites. For comparison, a pristine Ir(111) surface was considered as the reference catalytic surface. The Brillouin zone was sampled using a 4 × 4 × 1 Monkhorst-Pack k-point mesh. Adsorption configurations of reaction intermediates were optimized on the constructed surfaces to evaluate adsorption energies. A vacuum layer of 20 Å was introduced along the c-direction to eliminate interactions between periodic images. The plane-wave cutoff energy was set to 400 eV and the convergence criteria for energy and force were 10−5 eV and 10−2 eV Å−1, respectively.

The adsorption energy (Eads) was calculated using the following equation:
Eads = Esubstrate+adsorbate − (Esubstrate + Eadsorbate) (7)
where Esubstrate+adsorbate is the total energy of the (adsorbate + substrate) system, and Esubstrate and Eadsorbate represent the energies of the clean surface and isolated adsorbate, respectively.

The Gibbs free energy change (ΔG) for each elementary reaction step was determined by:
ΔG = ΔE + ΔEZPE − TΔS (8)
Where ΔE is the adsorption energy, ΔEZPE and ΔS denote the zero-point energy and entropy corrections, respectively, and T is the temperature (300 K).

The atomic coordinate information is available in Supplementary Data 1.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The manuscript presents a comprehensive study on plasmon-enhanced photocatalytic dry reforming of methane (DRM) utilizing core-cage Ag@Ir nanostructures. This innovative catalyst design effectively activates both CH4 and CO2 molecules under light illumination, resulting in a significant enhancement of DRM reaction activity at ambient temperature. The efficient generation and directional transfer of hot carriers from the plasmonic Ag-core to the catalytic Ir-cage surface can be attributed to a distinctive “antenna-reactor” mechanism that facilitates selective energy dissipation. This article serves as an important demonstration of rationally designed plasmonic catalysts for achieving efficient and stable DRM processes. However, for publication in this esteemed journal, the authors are encouraged to address the following comments:\n1.The schematic (Fig. 1) labels the Ir formation as “deposition”, while the text describes it as “grown” (e.g., line 87: “...Ir cage functioning as the “reactor” that is grown selectively...”). Please align terminology or clarify the process in Methods.\n2.In the charge density difference analysis (Fig. 2i), distinguishing Ag and Ir atoms is challenging due to similar color saturation. To improve the readability of the charge density difference analysis, please add atomic colour identification explanations to the figure, for example: “Gold spheres: Ag; Blue spheres: Ir”).\n3.The sub-panel label “d” in Fig. 3d is truncated/cropped (e.g., due to image compression or layout alignment issues). Please modify to ensure clarity and professionalism.\n4.To enhance the clarity of the dual-y-axis presentation in Fig. 4h, the data should be explicitly labeled in accordance with their respective y-axes.\n5.The language should be improved.\n6.Page S2, lines 36 and 42, more experimental details should be provided. For example, the amount of NaOH used, as well as the temperature and duration of vacuum drying.", "reviewer_2": "In this work, the authors synthetized Ag nanoparticles within an Ir cage and evaluated their performances in the photocalytic dry reforming reaction of methane (DRM). The presence of the Ir cage is fundamental to concentrate the hot electrons generated on the plasmonically active Ag core on catalytically active Ir therefore boosting its activity in DRM. The catalyst is reported to be highly selective and highly stable (>300 h on stream).\nAmong the various reforming processes, DRM converts two potent greenhouse gases into useful syngas, making it a critical reaction in the decarbonization scenario. Activity, but more important, stability at low temperature are still two major challenges that are hindering the real scaleup and widespread use of this reaction.\nThe use of concentrated light as energy input can mitigated the high thermal energy input needed to preform DRM with acceptable activity and stability.\nThe present manuscript is sound and represent a marked advancement of the state-of-the-art of photocatalysts for DRM, especially in terms of coke resistance and stability.\nIt is worth for publication in Nature Communications after addressing some points.\n- All the single components of the final photocatalyst, that is, the Ag@Ir-cages, MgAl-LDH, and the Ag@Ir-cages/MgAl-LDH, were synthetized with the help of surfactants. While this is understandable for the Ag@Ir-cages, it is not clear why formamide was employed for the preparation of MgAl-LDH considering that the precipitation was initiate by NaOH, and why n-butylamine was added during the deposition of the Ag@Ir-cages on the MgAl-LDH. Can the authors explain? And were the authors sure that all these molecules were removed before the characterizations and the catalytic tests?\n- The catalytic tests were performed using “in a flow reactor with a quartz window” with the catalyst dispersed “on a 6 mm diameter stainless steel substrate”. The authors should provide more details on the reactor and on the preparation procedure of the catalytic bed. This a critical point for two reasons. Firstly, it is well known that flow photocatalytic tests with external heating systems, with their peculiar geometry to accommodate the window while ensuring a uniform temperature of the catalytic bed, may be affected by sever mass transport issues due to a non-optimal diffusion of the gases. Proving the absence of transport limitations is essential to make a meaningful comparison with the literature. Secondly, it is not clear how the comparison with the Ir cages was made. For instance, was the amount of Ir the same in the reactor?\n- To better appreciated the impact of the Ir cage on the activity, the authors should add a test using only Ag nanoparticles ideally prepared by reproducing the synthetic procedure of the Ag@Ir-cages but without any Ir precursor.\n- There is a typo in row 363. Instead of CO it should be CO2.\n- It is not clear how the carbon balance was calculated. Please explain.\n- Despite the exception stability, a 12% activity loss was reported anyway after 300 h on stream. Since no coke deposition could be evidenced, can the authors provide some plausible explanation for such activity loss?", "reviewer_3": "This manuscript reported an Ag@Ir-cages photocatalyst for methane dry reforming reaction. The structure of Ag@Ir-cages photocatalyst is novel, and catalytic performance is superior. However, some questions should be clarified before publication.\n1、 There is a small peak around 40.5 degree of Ag@Ir-cages in Fig.2a，whether it is the feature of Ir species？\n2、 The UV-Vis DRS of Ir-cages was lacked in Fig. 3a and Fig. 3. The enhanced absorption of Ag@Ir-cages might be due to the LSPR effect of Ir species. As reported in literatures, among the Pt group metals, iridium(Ir) is a compelling metal for UV plasmonic because its bulk plasma frequency is 7.8 eV。【Applied Surface Science 487 (2019) 674–677】\n3、 What is the reaction conditions for Ir-cages catalyst in Fig. 4a? If the reaction was conducted in the dark, how can the reaction occurred over Ir-cages without thermal-driven? If the reaction was conducted under light irradiation, how can Ir-cages driven the reaction without the LSPR effect of Ag core? The reaction condition also lacked in Supplementary Fig. 9.\n4、 How to exclude the LSPR effect of Ir-cages in the ultraviolet region? In Fig. 4h, we can see that the catalytic performance of Ag@Ir-cages was higher at 375 nm than that at 400nm. However, the absorption peak of Ag core in the UV-Vis DRS was at 400 nm, which means the LSPR effect of Ag core was not the main driven force. Besides, the LSPR absorption peak was in the ultraviolet region for Ir, was the highest catalytic performance at 375 nm originated from the LSPR effect of Ir in th ultraviolet region?\n5、 What is the difference between Fig. 4b and Supplementary Fig. 10. Supplementary Fig. 11? Is it repetitive?\n6、 The authors claimed “Light irradiation also leads to the negative shift of Ir 4f XPS peaks of Ag@Ir-cages (Fig. 3h).” The detailed test procedure should be given. The XPS test process is a light exciting process, what is the meaning of in the dark or under light irradiation? (The caption of Fig. 3h, XPS spectra of Ir 4f measured under dark and light conditions for Ag@Ir-203 cages). In other words, how to conduct the XPS test in the dark?\n7、 The authors should make sure the CO2-TPD spectra of Ag@Ir-cages, Ag NCs, Ir-cages, and MgAl-LDH or MgAl-LDH supported Ag@Ir-cages, Ag NCs, Ir-cages in Fig.5. Besides, there is some doubts about the data in Fig. 5, the MgAl-LDH is easily decomposed into MgO-Al2O3 mixed metal oxide and CO2 and H2O at high temperature. So, the CO2 TPD of MgAl-LDH is confused.\n8、 It is noteworthy that the reaction pathway involving *CHxO species can 356 effectively mitigate coking, thereby enhancing the stability\nWhy the Ir-cages suffered from the coking? Is there any difference in the reaction mechanism? The in situ FT-IR of Ir-cages should be added."}, "author_response": "Response Letter\n(All revisions in the revised manuscript were highlighted in red)\nManuscript ID: NCOMMS-25-56446\nTitle: Concentrating and Directing Energy Flow in Plasmonic Heterostructures\nto Completely Prevent Coking for Stable and Efficient Light-driven Methane\nDry Reforming\nReviewer #1:\nThe manuscript presents a comprehensive study on plasmon-enhanced photocatalytic\ndry reforming of methane (DRM) utilizing core-cage Ag@Ir nanostructures. This\ninnovative catalyst design effectively activates both CH and CO molecules under\n4 2\nlight illumination, resulting in a significant enhancement of DRM reaction activity at\nambient temperature. The efficient generation and directional transfer of hot carriers\nfrom the plasmonic Ag-core to the catalytic Ir-cage surface can be attributed to a\ndistinctive “antenna-reactor” mechanism that facilitates selective energy dissipation.\nThis article serves as an important demonstration of rationally designed plasmonic\ncatalysts for achieving efficient and stable DRM processes. However, for publication\nin this esteemed journal, the authors are encouraged to address the following\ncomments:\nAnswer:\nWe sincerely thank you for your very positive evaluation on our work and highly\nappreciate your great effort to review the manuscript. Your comments are insightful\nand very constructive for improving our manuscript. The following is a detailed\nresponse to your comments.\nComment 1. The schematic (Fig. 1) labels the Ir formation as “deposition”, while the\ntext describes it as “grown” (e.g., line 87: “...Ir cage functioning as the “reactor”\nthat is grown selectively...”). Please align terminology or clarify the process in\nMethods.\nThank you very much for your comments. We have changed “Ir deposition” to “Ir\ngrowth” in Fig. 1a.\nRevision in Manuscript\nLine 135\nFig. 1. | Synthesis of Ag@Ir-cages. a Schematic illustration of the synthesis of\nAg@Ir-cages. b TEM and c HAADF-STEM images of Ag@Ir-cages. d The line\nintensity profiles of the regions labeled in (c). e The intensity image of the region\nmarked by the red solid square in (c). f HAADF-STEM image and the corresponding\nEDS elemental mappings of an individual Ag@Ir-cage.\nComment 2. In the charge density difference analysis (Fig. 2i), distinguishing Ag and\nIr atoms is challenging due to similar color saturation. To improve the readability of\n2\nthe charge density difference analysis, please add atomic colour identification\nexplanations to the figure, for example: “Gold spheres: Ag; Blue spheres: Ir”).\nAnswer:\nThank you very much for your comments. We have added colour identifications to the\natoms in the caption of Fig. 2i.\nRevision in Manuscript\nLine 183\nFig. 2. | Structural characterization. a XRD patterns of Ag@Ir-cages and Ag NCs.\nb Ir L -edge XANES spectra of Ag@Ir-cages and the references. c FT k3-weighted Ir\n3\n(d) Ag@Ir-cages, (e) IrO , and (f) Ir foil; g EXAFS fitting curve of Ag@Ir-cages at Ir\nand Ir in Ag@Ir-cages. Gray and light-yellow balls correspond to Ag and Ir atoms,\nrespectively.\nComment 3. The sub-panel label “d” in Fig. 3d is truncated/cropped (e.g., due to\nimage compression or layout alignment issues). Please modify to ensure clarity and\nprofessionalism.\nAnswer:\nThank you very much for your comments. Fig. 3d has been updated in the revised\nmanuscript.\nRevision in Manuscript\nLine 199\nvisible absorption spectra of Ag@Ir-cages, Ag NCs and Ir-cages. b PL spectra of\nAg@Ir-cages and Ag NCs. c, d 2D pseudo-color maps of TA spectra of (c) Ag NCs\nand (d) Ag@Ir-cages recorded after the excitation of a 400-nm laser. e Normalized\ndecay kinetic curves probed at 650 nm for Ag NCs and Ag@Ir-cages. f XPS spectra\nof Ir 4f measured under dark and light conditions for Ag@Ir-cages. g Simulated\nelectromagnetic field distribution and enhancement effect over Ag NCs (top), Ir-cages\n(middle) and Ag@Ir-cages (bottom) under 400-nm light excitation. The color scale\nshows the electromagnetic field enhancement.\nComment 4. To enhance the clarity of the dual-y-axis presentation in Fig. 4h, the data\nshould be explicitly labeled in accordance with their respective y-axes.\nAnswer:\nThank you very much for your comments. Fig. 4h has been updated in the revised\nmanuscript.\nRevision in Manuscript\nFig. 4. | Photocatalytic DRM performance. a Long-term stability and selectivity of\nAg@Ir-cages for DRM under 18.5 W cm-2 light illumination. The performance of Ir-\ncages is also provided for comparison, which was measured under the identical\nreaction conditions to Ag@Ir-cages. b Raman spectra of Ir-cages and Ag@Ir-cages\ncollected following the 30-hour and 300-hour DRM reactions, respectively. c H\n2\nproduction rate and d CH conversion rate for DRM over Ag@Ir-cages as a function\n4\nof light intensity. e Light intensity dependence on the reaction selectivity over Ag@Ir-\ncages. f Dependence of catalyst surface temperature on light intensity over Ag@Ir-\ncages. g Production rates of H and CO in DRM over Ag@Ir-cages under both light\n2\nirradiation and external heating alone. h Normalized absorption spectrum of Ag@Ir-\ncages plotted as a function of the wavelength-dependent DRM reaction rate. In the\nmeasurements, due to the intensity of monochromatic light is too low to initiate the\nreaction, an external heating (550 °C) was employed.\nComment 5. The language should be improved.\nAnswer:\nentire manuscript and improved the language.\nComment 6. Page S2, lines 36 and 42, more experimental details should be provided.\nFor example, the amount of NaOH used, as well as the temperature and duration of\nvacuum drying.\nAnswer:\nThank you very much for your comments. More experimental details have been added\nin the revised Supplementary Information.\nRevision in Supplementary Information\nPage S2\nSynthesis of MgAl-LDH. MgAl-LDH was prepared using a modified method\nreported previously.1 In a typical process, 19 mg of Mg(NO ) ·6H O and 9 mg of\n3 2 2\nAl(NO ) ·9H O were added to a beaker containing 20 mL of formamide solution (23\n3 3 2\nvol.% ) and heated to 80 °C for 10 min. During this period, 1.0 M NaOH solution was\ngradually added to the flask to maintain the pH of about 10 (totally, 12.5 mL of NaOH\nsolution was added). The product was collected by centrifugation, washed repeatedly\nwith deionized water and ethanol, and kept in 10 mL of ethanol for subsequent use.\nPreparation of MgAl-LDH supported Ag@Ir-cages. The as-prepared Ag@Ir-cages\nand MgAl-LDH were dispersed in 25 mL of n-butylamine to form a homogeneous\nsuspension. After being stirred at room temperature for 24 h, the catalyst was\ncollected by centrifugation, and washed several times with hexane and ethanol to\nremove excess n-butylamine. Finally, the catalyst was dried overnight at 80 °C under\nvacuum conditions. The loading amount of Ag and Ir were determined to be 15.4 and\n4.1 wt%, respectively, by inductively coupled plasma optical emission spectroscopy\n(ICP-OES).\nPreparation of MgAl-LDH supported Ir-cages. The as-prepared Ir-cages and\nMgAl-LDH were dispersed in 25 mL of n-butylamine to form a homogeneous\nsuspension. After being stirred at room temperature for 24 h, the catalyst was\ncollected by centrifugation, and washed several times with hexane and ethanol to\n6\nremove excess n-butylamine. Finally, the catalyst was dried overnight at 80 °C under\nvacuum conditions. The loading amount of Ir was determined to be 5.0 wt% by ICP-\nOES.\nPreparation of MgAl-LDH supported Ag NCs. The as-prepared Ag NCs and MgAl-\nLDH were dispersed in 25 mL of n-butylamine to form a homogeneous suspension.\nAfter being stirred at room temperature for 24 h, the catalyst was collected by\ncentrifugation, and washed several times with hexane and ethanol to remove excess n-\nbutylamine. Finally, the catalyst was dried overnight at 80 °C under vacuum\nconditions.\nIn this work, the authors synthetized Ag nanoparticles within an Ir cage and evaluated\ntheir performances in the photocalytic dry reforming reaction of methane (DRM). The\npresence of the Ir cage is fundamental to concentrate the hot electrons generated on\nthe plasmonically active Ag core on catalytically active Ir therefore boosting its\nactivity in DRM. The catalyst is reported to be highly selective and highly stable\n(>300 h on stream).\nAmong the various reforming processes, DRM converts two potent greenhouse gases\ninto useful syngas, making it a critical reaction in the decarbonization scenario.\nActivity, but more important, stability at low temperature are still two major\nchallenges that are hindering the real scaleup and widespread use of this reaction.\nThe use of concentrated light as energy input can mitigated the high thermal energy\ninput needed to preform DRM with acceptable activity and stability.\nThe present manuscript is sound and represent a marked advancement of the state-of-\nthe-art of photocatalysts for DRM, especially in terms of coke resistance and stability.\nIt is worth for publication in Nature Communications after addressing some points.\nAnswer:\nWe sincerely thank you for your very positive evaluation on our work and highly\nappreciate your great effort to review the manuscript. Your comments are insightful\nand very constructive for improving our manuscript. The following is a detailed\nresponse to your comments.\nComment 1. All the single components of the final photocatalyst, that is, the Ag@Ir-\ncages, MgAl-LDH, and the Ag@Ir-cages/MgAl-LDH, were synthetized with the help\nof surfactants. While this is understandable for the Ag@Ir-cages, it is not clear why\nformamide was employed for the preparation of MgAl-LDH considering that the\nprecipitation was initiate by NaOH, and why n-butylamine was added during the\ndeposition of the Ag@Ir-cages on the MgAl-LDH. Can the authors explain? And were\nthe authors sure that all these molecules were removed before the characterizations\nand the catalytic tests?\nThank you very much for your insightful comments.\n(1) In this work, MgAl-LDH was prepared in the presence of formamide according\nto a widely reported method (Nanoscale 7, 9448-9451 (2015); Angew. Chem. Int. Ed.\n62, e202217296 (2023).). Regarding the role of formamide in the preparation of\nMgAl-LDH, Yu et al. have conducted a comprehensive investigation (Nanoscale 7,\n9448-9451 (2015).). It is demonstrated that formamide primarily functions as a layer\ngrowth inhibitor by adsorbing onto the surface of MgAl-LDH sheets, thereby\npromoting lateral sheet growth while suppressing interlayer expansion, ultimately\nresulting in the formation of thin MgAl-LDH nanosheets. It should be mentioned that,\nbefore being used as the support for the deposition of Ag@Ir-cages, the as-prepared\nMgAl-LDH was thoroughly washing with water and ethanol to remove the surface\nadsorbed formamide. To confirm the removal of formamide, Fourier transform\ninfrared (FTIR) spectroscopy measurements were performed (the related results are\ndiscussed below (Point 4 of this response)).\n(2) The deposition of Ag@Ir-cages onto MgAl-LDH with the addition of n-\nbutylamine also follows a well-established procedure (J. Am. Chem. Soc. 132, 4984-\n4985 (2010); Science 344, 495-499 (2014); ACS Catal. 13, 12288-12298 (2023); ECS\nTrans. 61, 25 (2014).). According to these reports, n-butylamine, as a short-chain\nalkylamine ligand, can function to replace the surface long-alkane-chain capping\nagents—specifically oleylamine—on Ag@Ir-cages through kinetic ligand exchange\n(oleylamine was used in the preparation of Ag@Ir-cages and presumably adsorbed on\ntheir surface). Subsequently, with the thorough washing with ethanol and n-hexane,\nthe excess surfactants of oleylamine and n-butylamine would be washed off. The\nFTIR spectra were collected to confirm the removal of oleylamine and n-butylamine\nand the corresponding results are discussed below (Point 4 of this response).\n(3) In the present study, the catalytic tests were conducted under the light\nirradiation (18.5 W cm-2), under which the catalyst surface temperature reached\naround 425 °C (Fig. 4f). Given that the boiling points of formamide (210 °C),\noleylamine (364 °C) and n-butylamine (78 °C) are much lower than this catalyst\n9\nsurface temperature, even though there are trace amounts of formamide, oleylamine\nor n-butylamine remaining on the catalyst surface, they would be completely removed\nunder the catalytic reaction conditions.\n(4) To confirm the complete removal of formamide, oleylamine and n-butylamine\nin the catalysts, MgAl-LDH, MgAl-LDH supported Ag@Ir-cages, and the irradiated\nMgAl-LDH supported Ag@Ir-cages (collected after being irradiated for 5 min) were\ninvestigated by FTIR. For comparison, the FITR spectra of oleylamine, n-butylamine,\nand formamide were also recorded. As shown in Fig. R1, the representative band\nlocated at 1662 cm-1, which can be attributed to the vibration of C=O in formamide,\nis not observed in the spectra of MgAl-LDH, MgAl-LDH supported Ag@Ir-cages, and\nthe irradiated MgAl-LDH supported Ag@Ir-cages, indicating the removal of\nformamide. Oleylamine and n-butylamine present strong characteristic absorption\nbands at 2950 to 2860 cm-1, which could be assigned to the vibration of C−H.\nHowever, these bands are not detected in the spectra of MgAl-LDH supported Ag@Ir-\ncages and the irradiated MgAl-LDH supported Ag@Ir-cages. This result suggests that\noleylamine and n-butylamine are removed in MgAl-LDH supported Ag@Ir-cages.\nFig. R1. FTIR spectra of formamide, n-butylamine, oleylamine, MgAl-LDH, MgAl-\nLDH supported Ag@Ir-cages, and the irradiated MgAl-LDH supported Ag@Ir-cages.\nwindow” with the catalyst dispersed “on a 6 mm diameter stainless steel substrate”.\nThe authors should provide more details on the reactor and on the preparation\nprocedure of the catalytic bed. This a critical point for two reasons. Firstly, it is well\nknown that flow photocatalytic tests with external heating systems, with their peculiar\ngeometry to accommodate the window while ensuring a uniform temperature of the\ncatalytic bed, may be affected by sever mass transport issues due to a non-optimal\ndiffusion of the gases. Proving the absence of transport limitations is essential to\nmake a meaningful comparison with the literature. Secondly, it is not clear how the\ncomparison with the Ir cages was made. For instance, was the amount of Ir the same\nin the reactor?\nAnswer:\nThank you very much for your insightful comments. The photograph of the reactor\nand the gas flow pathway in the reactor are provided in Supplementary Fig. 20\n(shown below) to give more details of the reactor. Prior to each measurement, 5.0 mg\nof the MgAl-LDH supported catalysts (MgAl-LDH supported Ag@Ir-cages, MgAl-\nLDH supported Ir-cages, or MgAl-LDH supported Ag nanocrystals) were uniformly\nplaced in the sample holder (6 mm in diameter) of the reactor to form the catalytic bed.\nTo evaluate the transport limitations of the present reaction system, the catalytic\nactivity of Ag@Ir-cages for DRM was measured as a function of the catalyst loading\nat a constant W/F of 1.5 × 10-2 kg s L-1 (here, W indicates the catalyst weight, and F\nmeans the flow rate). According to previous reports (Ind. Eng. Chem. Res. 60, 18243-\n18255 (2021); AlChE J. 63, 2019-2029 (2017); Appl. Catal., A 308, 119-127 (2006).),\nwhen the reforming rate is not affected by changing the amount of catalyst and the\nflow rate, i.e., at constant contact time., the transport limitation is negligible under the\nconditions applied. As shown in Supplementary Fig. 21 (provided below), the H\n2\nproduction rate remains nearly constant as the feed flow rate increases from 8 to 32\nmL/min, indicating that transport limitations are negligible in the present reaction\nsystem within this flow rate range. In the work, a flow rate of 20 mL/min was used for\nthe catalytic activity measurements. Thus, the transport limitations are negligible\n11\nunder the experimental conditions employed.\nThe Ir-cages were prepared by etching Ag from the as-prepared Ag@Ir-cages using\na HNO solution (0.1 M). Then, the Ir-cages were loaded onto the MgAl-LDH support\n3\nfor the subsequent catalytic activity measurement. The loading amounts of Ir in\nMgAl-LDH supported Ag@Ir-cages and MgAl-LDH supported Ir-cages were\ndetermined to be 4.1 and 5.0 wt%, respectively, by ICP-OES, indicating comparable\nIr loadings. Given that identical quantities (5 mg) of both catalysts were employed in\nthe catalytic activity measurements, the actual amounts of Ir introduced into the\nreactor were nearly equivalent in both cases.\nSupplementary Fig. 20. (a-d) Photographs of the reactor. (e) The gas flow pathway\nin the reactor.\nSupplementary Fig. 21. Effect of the flow rate on the reforming rate over MgAl-\nLDH supported Ag@Ir-cages investigated at a constant W/F of 1.5 × 10-2 kg s L-1 (W:\ncatalyst weight; F: flow rate).\nPage S2\nSynthesis of Ir-cages. Typically, the as-prepared Ag@Ir-cages were dispersed in 20\nmL of 0.1 mol/L HNO solution via sonication, followed by stirring at room\n3\ntemperature for three days. Subsequently, the Ir cages were collected by\ncentrifugation and thoroughly washed with water for further use.\nPage S3\nPreparation of MgAl-LDH supported Ir-cages. The as-prepared Ir-cages and\nMgAl-LDH were dispersed in 25 mL of n-butylamine to form a homogeneous\nsuspension. After being stirred at room temperature for 24 h, the catalyst was\ncollected by centrifugation, and washed several times with hexane and ethanol to\nremove excess n-butylamine. Finally, the catalyst was dried overnight at 80 °C under\nvacuum conditions. The loading amount of Ir was determined to be 5.0 wt% by ICP-\nOES.\nPage S19\nSupplementary Table 2. The Ag and Ir mass loadings in the as-synthesized samples\ndetermined by ICP-OES.\nMass loading (%)\nSamples\nAg Ir\nMgAl-LDH supported\n15.4 4.1\nAg@Ir-cages\nMgAl-LDH supported\n- 5.0\nIr-cages\nSupplementary Fig. 20. (a-d) Photographs of the reactor. (e) The gas flow pathway\nin the reactor.\nSupplementary Fig. 21. Effect of the reactant flow rate on the reforming rate over\nMgAl-LDH supported Ag@Ir-cages investigated at a constant W/F of 1.5 × 10-2 kg s\nL-1 (W: catalyst weight; F: flow rate). As shown in the figure, the H production rate\n2\nremains nearly constant as the feed flow rate increases from 8 to 32 mL/min,\nindicating that transport limitations are negligible in the current reaction system\nwithin this flow rate range.\nComment 3. To better appreciated the impact of the Ir cage on the activity, the authors\nshould add a test using only Ag nanoparticles ideally prepared by reproducing the\nsynthetic procedure of the Ag@Ir-cages but without any Ir precursor.\nThank you very much for your insightful comments. We prepared Ag nanocrystals\n(Ag NCs) using the synthetic procedure of Ag@Ir-cages but without the addition of\nany Ir precursor. Then, the catalytic activity of Ag NCs was tested. The XRD pattern\nand TEM image of Ag NCs are shown in Supplementary Fig. 10a, b (provided below),\nrespectively. The catalytic activity data of Ag NCs is displayed in Supplementary Fig.\n10c. It can be seen that Ag NCs are inert under light irradiation toward DRM, with no\ndetectable products formed, which is likely due to their limited ability to activate CH\n4\n(J. Phys. Chem. C 127, 16357-16366 (2023)).\nRevision in Supplementary Information\nPage S2\nSynthesis of Ag NCs. Typically, 34 mg of AgNO and 52 mg of TPP were\n3\nsequentially added to a three-neck flask containing 6 mL of OAm and heated to\n120 °C for 10 min under vacuum. Subsequently, the flask was purged with N and the\n2\nmixture solution was heated to 170 °C for 60 min, after which the solution was further\nheated to 210 °C for 240 min. After being cooled to room temperature, the product\nwas collected by centrifugation and washed several times with hexane and ethanol for\nfurther characterizations.\nPage S3\nPreparation of MgAl-LDH supported Ag NCs. The as-prepared Ag NCs and MgAl-\nLDH were dispersed in 25 mL of n-butylamine to form a homogeneous suspension.\nAfter being stirred at room temperature for 24 h, the catalyst was collected by\ncentrifugation, and washed several times with hexane and ethanol to remove excess n-\nbutylamine. Finally, the catalyst was dried overnight at 80 °C under vacuum\nconditions.\nSupplementary Fig. 10. (a) XRD and (b) TEM image of Ag NCs. (c) Comparison of\nthe photocatalytic DRM performance between MgAl-LDH, MgAl-LDH supported Ag\nNCs, and MgAl-LDH supported Ag@Ir-cages. The performance was measured under\n18.5 W cm-2 light illumination without external heating (5 mg catalyst, 10 mL min-1\nof CH + 10 mL min-1 of CO ). (d) The reaction rates of CO and CH over MgAl-\n4 2 2 4\nLDH supported Ir-cages, which were measured under 18.5 W cm-2 light illumination\nwithout external heating (5 mg catalyst, 10 mL min-1 of CH + 10 mL min-1 of CO ).\n4 2\nComment 4. There is a typo in row 363. Instead of CO it should be CO .\nThank you very much for your comments. The correction has been made in the\nrevised manuscript.\nRevision in Manuscript\nLine 383\nBased on the above results, it can be reasonably inferred that the DRM pathway over\nAg@Ir-cages proceeds through the following steps: 1) CH and CO are dissociated\n4 2\ninto (*CH + *H) and (*CO + *O), respectively; 2) *CH subsequently reacts with *O\nx x\nto form *CH O, which further dissociates into (*CO + *H); 3) *CO desorbs to\nx\n16\nproduce CO, while *H species couple to form H .\nAnswer:\nThank you very much for your comments. We have added the calculation details of\ncarbon balance rate in the revised Supplementary Information.\nRevision in Supplementary Information\nPage S4\nCatalytic performance measurements. The methane dry reforming (DRM)\nperformance was measured at ambient pressure in a flow reactor with a quartz\nwindow at the top of the reactor for light exposure (Supplementary Figs. 20 and 21).\nPrior to each measurement, 5.0 mg of the MgAl-LDH supported catalyst was\nuniformly placed in the sample holder of the reactor with a diameter of 6 mm. Then,\nreaction gas (50% CH /50% CO ) was continuously fed into the reactor at a flow rate\n4 2\nof 20 mL min-1. A 300 W Xe lamp (MC-PF300C, Merry Change light) equipped with\na focusing lens was used as a light source to drive the DRM reaction. The quantities\nof CO and H were determined by an on-line gas chromatography (GC, Scion 456i,\ndetectors. The surface temperatures of the catalyst under illumination were recorded\nusing a K-type thermocouple. For wavelength-dependent experiments, the reaction\ntemperature was maintained at 550 °C using a temperature controller and the\nmonochromatic light of 380, 405, 420, 480, 532, 600, and 660 nm wavelengths, with\na bandwidth of ±10 nm, were obtained using a set of band pass filters.\nThe production rates of H (𝑟 ) and CO (𝑟 ) and the reaction rates of CH (𝑟 )\n2 𝐻2 𝐶𝑂 4 𝐶𝐻4\nand CO (𝑟 ) were defined as follows:\n2 𝐶𝑂2\n𝑟 = 𝐶𝑜𝑢𝑡 ×𝐹 ×60/(𝑉 ×𝑚) (1)\n𝐻2 𝐻2 𝑜𝑢𝑡 𝑚\n17\n𝑟 = 𝐶𝑜𝑢𝑡 ×𝐹 ×60/(𝑉 ×𝑚) (2)\n𝐶𝑂 𝐶𝑂 𝑜𝑢𝑡 𝑚\n𝑟 = (𝐶𝑖𝑛 ×𝐹 −𝐶𝑜𝑢𝑡 ×𝐹 )×60/(𝑉 ×𝑚) (3)\n𝐶𝐻4 𝐶𝐻4 𝑖𝑛 𝐶𝐻4 𝑜𝑢𝑡 𝑚\n𝑟 = (𝐶𝑖𝑛 ×𝐹 −𝐶𝑜𝑢𝑡 ×𝐹 )×60/(𝑉 ×𝑚) (4)\n𝐶𝑂2 𝐶𝑂2 𝑖𝑛 𝐶𝑂2 𝑜𝑢𝑡 𝑚\nwhere, 𝐶𝑖𝑛 and 𝐶𝑖𝑛 are the concentrations (vol%) of CH and CO in the stream of\n𝐶𝐻4 𝐶𝑂2 4 2\ninlet, respectively; 𝐶𝑜𝑢𝑡 and 𝐶𝑜𝑢𝑡 are the concentrations (vol%) of CH and CO in\n𝐶𝐻4 𝐶𝑂2 4 2\nthe stream of outlet, respectively; 𝐹 and 𝐹 indicate the gas flow rates (ml min-1)\n𝑜𝑢𝑡 𝑖𝑛\nof inlet and outlet, respectively; 𝑉 means the gas molar volume under standard\n𝑚\nconditions; and m represents the mass of catalyst.\nThe reaction selectivity was defined as follows:\nSelectivity=\n𝑟𝐻2\n(5)\n𝑟𝐶𝑂\nThe carbon balance rate was calculated by the equation (6):\n𝐶𝑎𝑟𝑏𝑜𝑛 𝑏𝑎𝑙𝑎𝑛𝑐𝑒 𝑟𝑎𝑡𝑒 =\n(𝐶\n𝐶\n𝑜\n𝑂\n𝑢𝑡×𝐹𝑜𝑢𝑡)+(𝐶\n𝐶\n𝑜\n𝐻\n𝑢𝑡\n4\n×𝐹𝑜𝑢𝑡)+(𝐶\n𝐶\n𝑜\n𝑂\n𝑢\n2\n𝑡×𝐹𝑜𝑢𝑡)\n(6)\n(𝐶\n𝐶\n𝑖𝑛\n𝐻4\n×𝐹𝑖𝑛)+(𝐶\n𝐶\n𝑖𝑛\n𝑂2\n×𝐹𝑖𝑛)\nComment 6. Despite the exception stability, a 12% activity loss was reported anyway\nafter 300 h on stream. Since no coke deposition could be evidenced, can the authors\nprovide some plausible explanation for such activity loss?\nAnswer:\nThank you very much for your insightful comments. Indeed, as you pointed out,\ndespite exceptional stability, a 12% loss in activity was observed after 300 hours on\nstream. Such activity loss could be attributed to the gradual decrease in light intensity\ndue to the aging of the Xe lamp during the long-term continuous operation. Hence, we\nmonitored the light intensity of the Xe lamp during long-term continuous operation.\nAs shown in Supplementary Fig. 11 (provided below), the light intensity decreases\ngradually with increasing operation time. Specifically, after 120 hours of operation,\napproximately 9.4% reduction in light intensity is observed. This measured data of\nlight intensity as a function of operation time are in good agreement with the data (Fig.\nthe activity loss to the decrease in light intensity during the long-term continuous\noperation.\nSupplementary Fig. 11. The change in light intensity of the Xe lamp during\ncontinuous operation.\nFig. R2. The change in lumens of the Xe lamp over operation time. This data is\nprovided by the Xenon lamp manufacturer (PerkinElmer Corporation).\nRevision in Manuscript\nLine 302\nSpecifically, they achieve initial production rates of 2080 mmol g-1 h-1 for H and\n2\n2145 mmol g-1 h-1 for CO, respectively, with a H /CO ratio of 0.97. After 300 hours of\n2\nreaction, only a 12% reduction in the H production rate is observed, which could be\n2\npotentially attributed to the gradually reduced light intensity caused by the Xe lamp\naging during the long-term operation (Supplementary Fig. 11).\nPage S12\nSupplementary Fig. 11. The change in light intensity of the Xe lamp during\ncontinuous operation.\nThis manuscript reported an Ag@Ir-cages photocatalyst for methane dry reforming\nreaction. The structure of Ag@Ir-cages photocatalyst is novel, and catalytic\nperformance is superior. However, some questions should be clarified before\npublication.\nAnswer:\nWe extend our sincerest gratitude for your very positive evaluation on our work and\ndeeply appreciate the considerable effort you dedicated to reviewing our manuscript.\nYour insights are invaluable and the comments you provided are immensely\nconstructive for enhancing our paper. Attached below is a point-by-point response to\nyour feedback.\nComment 1. There is a small peak around 40.5 degree of Ag@Ir-cages in Fig.2a，\nwhether it is the feature of Ir species?\nAnswer:\nThank you very much for your helpful comments. We sincerely thank you for your\nvaluable reminding. We have carefully re-checked the XRD pattern of Ag@Ir-cages\nand compared it with the standard PDF data of metallic Ir. Indeed, as you pointed out,\nthe small peak at around 40.5 degree matches well with the diffraction of (111) plane\nof metallic Ir. Moreover, to rule out the potential interference from the signal noise,\nwe have also re-measured the XRD pattern of Ag@Ir-cages. As shown in Fig. R3, the\nsmall peak at around 40.5 degree is still detected in the re-measured XRD pattern,\nclearly confirming the above assignment.\nRevision in Manuscript\nLine 142\nFig. 2a shows the X-ray diffraction (XRD) patterns of Ag@Ir-cages and Ag NCs,\nin which characteristic diffraction peaks corresponding to metallic silver (JCPDS, 04-\n0783) can be clearly observed. Furthermore, a small peak at around 40.5 degree is\nobserved in the XRD pattern of Ag@Ir-cages, which could be attributed to the\ndiffraction of (111) plane of metallic Ir (JCPDS, 01-88-2342). X-ray absorption\nspectroscopy (XAS) measurements were employed to investigate the electronic\nstructure and local atomic environment of Ir in Ag@Ir-cages.\nComment 2. The UV-Vis DRS of Ir-cages was lacked in Fig. 3a and Fig. 3. The\nenhanced absorption of Ag@Ir-cages might be due to the LSPR effect of Ir species. As\nreported in literatures, among the Pt group metals, iridium (Ir) is a compelling metal\nfor UV plasmonic because its bulk plasma frequency is 7.8 eV. [Applied Surface\nScience 487 (2019) 674–677]\nAnswer:\nThank you very much for your insightful comments. Following your suggestions, the\nUV-visible absorption spectrum of Ir-cages has been added in Fig. 3a (provided\nbelow). As shown in the updated Fig. 3a, Ir-cages display a broad absorption from\n300 to 900 nm. According to previous reports (Angew. Chem. Int. Ed. 53, 2935-2940\n(2014); Phys. Rev. B 15, 4115-4118 (1977); J. Phys. Chem. C 111, 11246-11251\n(2007)), this broad absorption in the visible and UV ranges is dominated by the\ninterband transitions of Ir (the plasmon resonances of Ir were reported to range from\n6.7 to 7.8 eV, corresponding to wavelengths from approximately 159 to 185 nm\n(Coatings 13, 787 (2023); Phys. Rev. B 15, 4115-4118 (1977).)). Hence, the enhanced\nabsorption of Ag@Ir-cages could be attributed to the contribution from the interband\nabsorption of Ir-cages.\nFig. 3a. UV-visible absorption spectra of Ag@Ir-cages, Ag NCs and Ir-cages.\nRevision in Manuscript\nLine 208\nAs shown in Fig. 3a, Ag NCs exhibit a strong absorption peak ranging from 300 to\n600 nm, which can be attributed to the LSPR excitation of Ag. Meanwhile, Ir-cages\ndisplay a broad absorption in the visible and UV ranges, which is dominated by the\ninterband transitions.31-33 Notably, Ag@Ir-cages combine the LSPR absorption from\nthe Ag core and the interband absorption from the Ir cage, thereby demonstrating\nsignificantly enhanced light absorption spanning both the UV and visible ranges.\nMeanwhile, compared with that of Ag NCs, the LSPR peak of Ag@Ir-cages is\nslightly shifted and broadened, which is probably due to the change in the dielectric\nenvironment of Ag cores caused by the coating of Ir cages.25, 34\nLine 199\nvisible absorption spectra of Ag@Ir-cages, Ag NCs and Ir-cages. b PL spectra of\nAg@Ir-cages and Ag NCs. c, d 2D pseudo-color maps of TA spectra of (c) Ag NCs\nand (d) Ag@Ir-cages recorded after the excitation of a 400-nm laser. e Normalized\ndecay kinetic curves probed at 650 nm for Ag NCs and Ag@Ir-cages. f XPS spectra\nof Ir 4f measured under dark and light conditions for Ag@Ir-cages. g Simulated\nelectromagnetic field distribution and enhancement effect over Ag NCs (top), Ir-cages\n(middle) and Ag@Ir-cages (bottom) under 400-nm light excitation. The color scale\nshows the electromagnetic field enhancement.\nComment 3. What is the reaction conditions for Ir-cages catalyst in Fig. 4a? If the\nreaction was conducted in the dark, how can the reaction occurred over Ir-cages\nwithout thermal-driven? If the reaction was conducted under light irradiation, how\ncan Ir-cages driven the reaction without the LSPR effect of Ag core? The reaction\ncondition also lacked in Supplementary Fig. 9.\nAnswer:\nshown in Fig. 4a and Supplementary Fig. 10 were measured under 18.5 W cm-2 light\nillumination without external heating. The details of the reaction conditions have been\nadded in the revised manuscript and Supplementary Information.\nThe performance of Ir-cages observed under light irradiation can be attributed to\nthe contribution of the interband transitions of Ir, which is discussed in detail as\nfollows. As shown in Fig. 3a, Ir-cages display a broad absorption in the visible and\nUV ranges, which is dominated by the interband transitions of Ir corresponding to the\nphotoinduced excitation of bound electrons to high energy levels (J. Phys. D: Appl.\nPhys. 37, 3133 (2004); J. Phys. Chem. C 111, 11246-11251 (2007).). Similar to LSPR\neffect commonly observed in conventional plasmonic metals like Au, Ag and Cu,\nthe interband transitions can also induce the formation of hot carriers and the heating,\nwhich both can contribute to chemical reactions (Angew. Chem. Int. Ed. 53, 2935-\n2940 (2014); J. Mater. Chem. A 2, 9875-9882 (2014); APL Materials 3, 104401\n(2015).).\nTo confirm the effect of interband transitions of Ir-cages on their catalytic\nperformance for DRM, a series of experiments were conducted. Firstly, the\nphotothermal effect of Ir cages was investigated. As shown in Fig. R4, under the light\nirradiation without external heating, the surface temperature of Ir cages is remarkably\nincreased. Specifically, at the light intensity of 18.5 W cm-2 (the catalytic performance\nof Ir-cages was investigated at this light intensity), the surface temperature of Ir cages\nreaches around 389 °C. This result indicates the interband transitions of Ir-cages can\ninduce significant photothermal effect via dissipating the photon energy into heat.\nThen, we conducted the thermocatalytic DRM reaction over Ir-cages at 389 °C\nthrough external heating (without light irradiation). As shown in Fig. R5, under such\nthermocatalytic conditions, no products are detected. Furthermore, even when the\nreaction temperature is further increased to 580 °C, the production of CO and H\n2\nremains negligible. In contrast, as shown in Fig. 4a, Ir-cages demonstrate significantly\nhigher production rates for CO and H under light irradiation conditions (light\n2\nintensity of 18.5 W cm-2; without external heating; surface temperature of Ir cages\n25\nwas measured to be 389 °C). Based on the above results, it can be reasonably\nconcluded that the hot carriers induced by the interband transitions contribute to the\nDRM reaction over Ir-cages, while the high surface temperature induced by\nphotothermal conversion is also necessary for initiating the reaction.\nFurthermore, the impact of the irradiation wavelength on the catalytic reaction rate\nof Ir-cages was also investigated. As shown in Fig. R6, the dependence of the\nnormalized reaction rate of Ir-cages on the wavelength of light exhibits a profile\nsimilar to the light absorption spectrum. This result provides additional evidence that\nthe excitation of interband transitions of Ir-cages is responsible for the observed\ncatalytic performance for DRM.\nBased on the above discussion, it can be concluded that the performance of Ir-cages\nobserved under light irradiation can be attributed to the interband transitions of Ir.\nFig. 3a. UV-visible absorption spectra of Ag@Ir-cages, Ag NCs and Ir-cages.\nFig. R5. Production rates of H and CO in DRM over Ir-cages measured at different\n2\ntemperatures through external heating (without light irradiation).\nFig. R6. Absorption spectrum of Ir-cages plotted as a function of the wavelength-\n27\ndependent DRM reaction rate. In the measurements, due to the intensity of\nmonochromatic light is too low to initiate the reaction, an external heating (550 °C)\nwas employed.\nRevision in Manuscript\nLine 273\nFig. 4. | Photocatalytic DRM performance. a Long-term stability and selectivity of\nAg@Ir-cages for DRM under 18.5 W cm-2 light illumination. The performance of Ir-\ncages is also provided for comparison, which was measured under the identical\nreaction conditions to Ag@Ir-cages. b Raman spectra of Ir-cages and Ag@Ir-cages\ncollected following the 30-hour and 300-hour DRM reactions, respectively. c H\n2\nproduction rate and d CH conversion rate for DRM over Ag@Ir-cages as a function\n4\nof light intensity. e Light intensity dependence on the reaction selectivity over Ag@Ir-\ncages. f Dependence of catalyst surface temperature on light intensity over Ag@Ir-\ncages. g Production rates of H and CO in DRM over Ag@Ir-cages under both light\n2\nirradiation and external heating alone. h Normalized absorption spectrum of Ag@Ir-\ncages plotted as a function of the wavelength-dependent DRM reaction rate. In the\nmeasurements, due to the intensity of monochromatic light is too low to initiate the\n28\nreaction, an external heating (550 °C) was employed.\nRevision in Supplementary Information\nPage S12\nSupplementary Fig. 10. (a) XRD and (b) TEM image of Ag NCs. (c) Comparison of\nthe photocatalytic DRM performance between MgAl-LDH, MgAl-LDH supported Ag\nNCs, and MgAl-LDH supported Ag@Ir-cages. The performance was measured under\n18.5 W cm-2 light illumination without external heating (5 mg catalyst, 10 mL min-1\nof CH + 10 mL min-1 of CO ). (d) The reaction rates of CO and CH over MgAl-\n4 2 2 4\nLDH supported Ir-cages, which were measured under 18.5 W cm-2 light illumination\nwithout external heating (5 mg catalyst, 10 mL min-1 of CH + 10 mL min-1 of CO ).\n4 2\nComment 4. How to exclude the LSPR effect of Ir-cages in the ultraviolet region? In\nFig. 4h, we can see that the catalytic performance of Ag@Ir-cages was higher at 375\nnm than that at 400 nm. However, the absorption peak of Ag core in the UV-Vis DRS\nwas at 400 nm, which means the LSPR effect of Ag core was not the main driven force.\nBesides, the LSPR absorption peak was in the ultraviolet region for Ir, was the highest\ncatalytic performance at 375 nm originated from the LSPR effect of Ir in the\nultraviolet region?\nAnswer:\n(MgAl-LDH supported) Ag@Ir-cages shown in Fig. 4h, the absorption peak located at\napproximately 375 nm can actually be attributed to the LSPR absorption of the Ag\ncore rather than the LSPR absorption of Ir. To confirm this point, the light absorption\nspectra of (MgAl-LDH supported) Ag@Ir-cages and (MgAl-LDH supported) Ir-cages\nare compared in Fig. R7. In contrast to (MgAl-LDH supported) Ag@Ir-cages showing\nan absorption peak centered at around 375 nm, (MgAl-LDH supported) Ir cages show\nno obvious absorption peak but a broad absorption in the visible and UV ranges,\nwhich can be attributed to the excitation of interband transitions of Ir (Angew. Chem.\nInt. Ed. 53, 2935-2940 (2014); Phys. Rev. B 15, 4115-4118 (1977); J. Phys. Chem. C\n111, 11246-11251 (2007)). This result confirms the absorption peak at 375 nm in the\nspectrum of (MgAl-LDH supported) Ag@Ir-cages is attributed to the LSPR\nabsorption of Ag core rather than that of Ir cage. Here, it should be noted that, Ag@Ir-\ncages show a narrow LSPR absorption peak at approximately 400 nm in Fig. 3a (as\nyou pointed out), while they show a broad LSPR absorption peak at around 375 nm in\nFig. 4h and Fig. R7. The spectral broadening and change in the position of the LSPR\npeak can be ascribed to the dense packing of Ag@Ir-cages on the support and to the\ndifferent dielectric constants of hexane and air (Nat. Chem. 3, 467-472 (2011).), as the\nspectrum presented in Fig. 3a was measured for a dilute solution of unsupported\nAg@Ir-cages in hexane, whereas the spectra shown in Fig. 4h and Fig. R7 were\nmeasured for the Ag@Ir-cages deposited on the MgAl-LDH support in air. Similar\nphenomena that the changes in the dielectric environment and the dispersion status of\nmetal nanoparticles lead to the shift and broadening of their light absorption were\nwidely reported (J. Phys. Chem. B 107, 668-677 (2003); J. Phys. Chem. B 109,\n21556-21565 (2005); Nat. Photon. 10, 473-482 (2016).).\nsupported Ir-cages, and MgAl-LDH.\nTo decouple the effects of LSPR of the Ag core and the effects of LSPR and\ninterband transitions of the Ir cage on the catalytic performance of (MgAl-LDH\nsupported) Ag@Ir-cages, additional experiments and theoretical simulations were\nperformed. Firstly, we further measured the action spectrum of (MgAl-LDH\nsupported) Ir-cages, where the normalized reaction rate of (MgAl-LDH supported) Ir-\ncages is plotted against the wavelength of light irradiation (Fig. R8a). Then, the rate\nenhancement was calculated by dividing the normalized reaction rate of (MgAl-LDH\nsupported) Ag@Ir-cages at different wavelengths by that of (MgAl-LDH supported)\nIr-cages (Fig. R8b). Meanwhile, the differential absorption spectrum of (MgAl-LDH\nsupported) Ag@Ir-cages relative to (MgAl-LDH supported) Ir-cages was also\ncalculated by subtracting the absorbance of (MgAl-LDH supported) Ir-cages from that\nof (MgAl-LDH supported) Ag@Ir-cages (Fig. R8b). This differential spectrum can\napproximately represent the LSPR absorption caused by the Ag core in (MgAl-LDH\nsupported) Ag@Ir-cages (J. Am. Chem. Soc. 135, 10064-10072 (2013).). Evidently,\nthe variation of the reaction rate enhancement is well consistent with the trend of the\ndifferential absorption spectrum. This result clearly indicates that the LSPR excitation\nof the Ag core is responsible for the observed enhancement in the catalytic\nperformance of (MgAl-LDH supported) Ag@Ir-cages for DRM.\nfunction of the wavelength-dependent DRM reaction rate. (b) Wavelength-dependent\nrate enhancement, which was calculated by dividing the normalized reaction rate of\n(MgAl-LDH supported) Ag@Ir-cages at different wavelengths by that of (MgAl-LDH\nsupported) Ir-cages. The differential absorption spectrum of (MgAl-LDH supported)\nAg@Ir-cages relative to (MgAl-LDH supported) Ir-cages is also shown, which was\ncalculated by subtracting the absorbance of (MgAl-LDH supported) Ir-cages from that\nof (MgAl-LDH supported) Ag@Ir-cages.\nIn addition, three-dimensional finite-difference time-domain (FDTD) simulations\nwere also conducted on Ir-cages. Fig. R9 presents the comparative electromagnetic\nfield profiles of Ag NC, Ir-cage, and Ag@Ir-cage simulated under 400 nm light\nirradiation. Obviously, both Ag NC and Ag@Ir-cage exhibit significant near-field\nenhancements due to the strong LSPR effect of Ag. In contrast, the electromagnetic\nfield intensity is quite weak on Ir-cage, since the plasmon resonance of Ir occurred in\nthe deep-UV region (located at around 159 to 185 nm, Coatings 13, 787 (2023); Phys.\nRev. B 15, 4115-4118 (1977).). Specifically, electromagnetic field intensities of\nAg@Ir-cage and Ag NC are more than six and two times that of Ir-cage, respectively.\nThese findings provide additional evidence suggesting that the LSPR excitation of the\nAg core plays a significant role in generating hot carrier to drive the DRM reaction\nover Ag@Ir-cages.\nIn summary, the discussions presented above clearly demonstrate the significant\nrole of the LSPR effect of the Ag core in promoting the DRM reaction over Ag@Ir-\n32\ncages. However, we must acknowledge that, as the LSPR absorption of the Ag core is\noverlapped with the absorption of the Ir-cage (Fig. R7), it is hardly possible to\ncompletely exclude the effects of LSPR and interband transitions of the Ir-cage on the\ncatalytic performance of Ag@Ir-cages. We would greatly appreciate it if the reviewer\ncould offer suggestions on alternative methods to completely exclude the effects of\nLSPR and interband transitions of the Ir-cage, and we are fully committed to update\naccordingly.\nFig. R9. Simulated electromagnetic field distribution and enhancement effect over (a)\nAg NC, (b) Ir-cage, and (c) Ag@Ir-cage under 400-nm light irradiation. The color\nscale shows the electromagnetic field enhancement.\nRevision in Manuscript\nLine 199\nvisible absorption spectra of Ag@Ir-cages, Ag NCs and Ir-cages. b PL spectra of\nAg@Ir-cages and Ag NCs. c, d 2D pseudo-color maps of TA spectra of (c) Ag NCs\nand (d) Ag@Ir-cages recorded after the excitation of a 400-nm laser. e Normalized\ndecay kinetic curves probed at 650 nm for Ag NCs and Ag@Ir-cages. f XPS spectra\nof Ir 4f measured under dark and light conditions for Ag@Ir-cages. g Simulated\nelectromagnetic field distribution and enhancement effect over Ag NCs (top), Ir-cages\n(middle) and Ag@Ir-cages (bottom) under 400-nm light excitation. The color scale\nshows the electromagnetic field enhancement.\nLine 241\nTo shed light on the concentration behavior of electromagnetic energy over Ag NCs,\nIr-cages and Ag@Ir-cages, we performed the three-dimensional finite-difference time-\ndomain (FDTD) simulations. The models used for the simulations were built\naccording to the TEM observations. Fig. 3g depict the comparative electromagnetic\nfield profiles under 400 nm illumination, where both Ag NC and Ag@Ir-cage exhibit\nsignificant near-field enhancement, while the electromagnetic field intensity of Ir-\n34\ncage is quite weak. As for the Ag NC, photoexcitation induces collective oscillation of\nconduction electrons, generating localized surface plasmon resonances that amplify\nthe electromagnetic field intensity. Notably, the maximum field enhancement occurs\nat the vertices of the Ag NC, a characteristic manifestation of the lightning rod effect\narising from geometric field focusing. In stark contrast, Ag@Ir-cage demonstrates\nremarkably augmented electromagnetic field intensity, particularly at edge and vertex\nregions, leading to more plasmonic hotspot generation. Specifically, the\nelectromagnetic field intensity at the vertices of the Ag@Ir-cage is more than 3 and 6\ntimes those of the Ag NC and the Ir-cage, respectively.\nComment 5. What is the difference between Fig. 4b and Supplementary Fig. 10.\nSupplementary Fig. 11? Is it repetitive?\nAnswer:\nThank you very much for your helpful comments. Yes, the data presented in Fig. 4b\nare identical to those displayed in the original Supplementary Figs. 10 and 11. In the\nrevised revision, we have deleted these two figures in the Supplementary Information.\nComment 6. The authors claimed “Light irradiation also leads to the negative shift of\nIr 4f XPS peaks of Ag@Ir-cages (Fig. 3h).” The detailed test procedure should be\ngiven. The XPS test process is a light exciting process, what is the meaning of in the\ndark or under light irradiation? (The caption of Fig. 3h, XPS spectra of Ir 4f\nmeasured under dark and light conditions for Ag@Ir-cages). In other words, how to\nconduct the XPS test in the dark?\nAnswer:\nThank you very much for your insightful comments. Schematic illustrations of the\nXPS measurements conducted under light irradiation (380 < λ < 800 nm) and in the\ndark are shown in Supplementary Fig. 19a, b, respectively. Specifically, during the\nXPS measurements conducted under light irradiation (380 < λ < 800 nm), the XPS\nspectra of the sample are recorded while the sample is simultaneously exposed to an\nadditional visible light irradiation (380 < λ < 800 nm). During the XPS measurements\n35\nperformed in the dark, the XPS spectra are collected without that visible light\nirradiation (380 < λ < 800 nm) on the sample. The detailed test procedure was added\nin the revised Supplementary Information.\nSupplementary Fig. 19. Schematic illustrations of the XPS measurements conducted\n(a) under light irradiation and (b) in the dark.\nRevision in Supplementary Information\nPage S3\nIn-situ X-ray photoelectron spectroscopy (XPS) analysis was performed under light\nirradiation (380 < λ < 800 nm) and in the dark using a Thermo Fisher Scientific\nESCALAB 250Xi photoelectron spectrometer equipped with a 300 W Xe lamp as\nsimulated solar light source. During the XPS measurements conducted under light\nirradiation, the XPS spectra of the sample were recorded while the sample was\nsimultaneously exposed to the visible light irradiation (Supplementary Fig. 19a).\nDuring the XPS measurements performed in the dark, the XPS spectra were collected\nwithout the visible light irradiation on the sample (Supplementary Fig. 19b).\nPage S16\nSupplementary Fig. 19. Schematic illustrations of the XPS measurements conducted\n(a) under light irradiation and (b) in the dark.\ncages in Fig.5. Besides, there is some doubts about the data in Fig. 5, the MgAl-LDH\nis easily decomposed into MgO-Al O mixed metal oxide and CO and H O at high\n2 3 2 2\ntemperature. So, the CO -TPD of MgAl-LDH is confused.\nThank you very much for your insightful comments. We apologize for that the sample\ninformation was not clearly clarified in the caption of Fig. 5. In the study, the CO -\nActually, prior to the CO -TPD measurements, all samples were pretreated at\n2\n300 °C for 1 h under a He atmosphere with a flow rate of 30 mL min-1. After this\npretreatment, MgAl-LDH was indeed decomposed into the MgO-Al O mixed metal\n2 3\noxide, as evidenced by the XRD result (Fig. R10a). However, the thermogravimetry-\nmass spectroscopy (TG-MS) analysis on the pretreated MgAl-LDH showed that the\nMgAl-LDH was not actually completely decomposed during the pretreatment, as\nthere was still a trace amount of CO and H O released from the pretreated MgAl-\n2 2\nLDH when it was re-heated to around 350 °C (Fig. R10b). This trace amount of CO\n2\nrelease would potentially interfere with the result of CO -TPD, as you pointed out.\n2\nmeasurements with the samples pretreated at 400 °C under a He atmosphere.\nConsidering that the catalytic performance of the catalysts was measured under the\n18.5 W cm-2 light irradiation, under which the catalyst surface temperature reached\nabove 400 °C (Fig. 4f), the pretreatment of the samples at 400 °C is acceptable. Fig.\nR11 shows the XRD pattern and TG-MS spectra of the MgAl-LDH sample pretreated\nat 400 °C. It is clear that the MgAl-LDH sample was completely decomposed into the\nMgO-Al O mixed metal oxide through this pretreatment at 400 °C, and no CO and\n2 3 2\nH O release was detected during the TG-MS analysis. Hence, with the sample\n2\npretreatment at 400 °C under a He atmosphere, the CO -TPD spectra of the MgAl-\nin Fig. 5a (provided below), both MgAl-LDH supported Ag@Ir-cages and MgAl-\ntemperature ranges of 50-150 °C, 200-350 °C, and 400-650 °C, corresponding to the\nweak, medium, and strong basic sites on their surface, respectively. It is noteworthy\nthat, the strong basic site peak of MgAl-LDH supported Ag@Ir-cages is shifted to a\nhigher temperature by approximately 13 °C as compared with that of MgAl-LDH-\nsupported Ir-cages. This result indicates that MgAl-LDH supported Ag@Ir-cages\nexhibit a stronger affinity for CO adsorption than MgAl-LDH supported Ir-cages.\n2\nthe improvement in DRM performance.\nFig. R10. (a) XRD pattern and (b) TG-MS analysis of the pretreated MgAl-LDH\nsample which is subjected to the annealing treatment at 300 °C for 1 h under a He\natmosphere with a flow rate of 30 mL min-1.\nFig. R11. (a) XRD pattern and (b) TG-MS analysis of the pretreated MgAl-LDH\nsample which is subjected to the annealing treatment at 400 °C for 1 h under a He\natmosphere with a flow rate of 30 mL min-1.\nLine 350\nTo illustrate the CO adsorption and activation capacity of MgAl-LDH supported\n2 2\nwere performed. As depicted in the CO -TPD spectra presented in Fig. 5a, both\nthree distinct desorption peaks with the temperature ranges of 50-150 °C, 200-350 °C\nand 400-650 °C, corresponding to the weak, medium, and strong basic sites on their\nsurface, respectively. It is noteworthy that, the strong basic site peak of MgAl-LDH\nsupported Ag@Ir-cages is shifted to a higher temperature by approximately 13 °C as\ncompared with that of MgAl-LDH-supported Ir-cages. This result indicates that\nMgAl-LDH supported Ag@Ir-cages exhibit a stronger affinity for CO adsorption\n2\nthan MgAl-LDH supported Ir-cages. This is likely due to that the electron-enriched Ir\natoms on the surface of Ag@Ir-cages provide stronger Lewis-base sites for CO\n2\nadsorption.42, 43 The strong adsorption of CO would facilitate its activation, thereby\n2\ncontributing to the improvement in DRM performance.\nLine 344\ncages collected at different irradiation time. c In-situ FTIR peak intensity for *CH O\nx\nintermediates over MgAl-LDH supported Ag@Ir-cages as a function of irradiation\ntime. d-g Reaction pathways of DRM on the surface of (d, e) Ag@Ir(111) and (f, g)\nIr(111).\nRevision in Supplementary Information\nPage S5\nCO -temperature-programmed desorption measurements (CO -TPD). CO -TPD\n2 2 2\nexperiments were conducted on a temperature-programmed desorption instrument\n(JW-HX100, Beijing JWGB Instrument Co., Ltd.) with a TCD detector. Firstly, 50\nmg sample was treated under a He atmosphere at a flow rate of 30 mL min-1 at 400 °C\nfor 1 h. After the sample was cooled to 50 °C, the gas was switched to 10% CO /He\n2\nfor 1 h and then the sample was purged with pure He for 1 h at the same temperature.\nFinally, the sample was heated from 50 to 700 °C at 10 °C min-1 under a He\natmosphere at a flow rate of 30 mL min-1 and the gas signal was detected by a TCD\ndetector.\neffectively mitigate coking, thereby enhancing the stability.\nWhy the Ir-cages suffered from the coking? Is there any difference in the reaction\nmechanism? The in situ FTIR of Ir-cages should be added.\nAnswer:\nThank you very much for your insightful comments. In accordance with your\nsuggestion, we have conducted the in-situ FT-IR investigation on Ir-cages to elucidate\nthe reaction mechanism occurring over them. As shown in the in-situ FTIR spectra of\nIr-cages (Supplementary Fig. 17, displayed below), a band centered at 1624 cm-1\nappears and grows gradually under light irradiation, which could be attributed\nstretching vibrations of C=C bonds (Proc. Natl. Acad. Sci. USA 79, 4972-4976\n(1982); ACS Nano 3, 2653-2659 (2009); Nat. Chem. 16, 893-900 (2024).), suggesting\nthe formation of carbon species and the fast coke deposition on the catalyst surface.\nConcurrently, no signals at 1072 cm-1, characteristic of *CH O species, are detected.\nx\nThese observations are consistent with the significant coke formation observed on Ir-\ncages during the DRM reaction (Fig. 4b) and their rapid deactivation in catalytic\nperformance (Fig. 4a).\nTo reveal the reason for the significant coke formation observed on Ir-cages,\ndensity functional theory (DFT) calculations were conducted. As shown in Fig. 5f\n(provided below), on the surface of Ir(111), *CH prefers to undergo conversion to *C\nrather than coupling with O to form *CHO, as demonstrated by the greater energetic\nfavorability of the *CH→*C pathway relative to the *CH→*CHO pathway.\nFurthermore, the subsequent oxidation of *C to *CO on Ir(111) is severely impeded\ndue to a high thermodynamic barrier of 3.24 eV, suggesting the occurrence of carbon\ndeposition. These findings are highly consistent with the results of in-situ FTIR which\nshow remarkable signals corresponding to carbon species but no detectable signals for\n*CH O species. All the above results provide a rational explanation for the significant\nx\ncoke deposition observed on Ir-cages during the DRM reaction and thus the fast\ncatalyst deactivation.\nBased on the above results, the corresponding revisions have been made in the\n41\nrevised manuscript and Supplementary Information.\nSupplementary Fig. 17. In-situ FTIR spectra of MgAl-LDH supported Ir-cages\ncollected at different irradiation time.\nFig. 5f. Reaction pathways of DRM on the surface of Ir(111).\nRevision in Manuscript\nLine 375\nNo characteristic peaks belong to *COOH species are detected during the\nmeasurement. In addition, in the in-situ FTIR spectra of Ir-cages (Supplementary Fig.\n17), a band centered at 1624 cm-1 appears and grows gradually under light irradiation,\nwhich could be attributed to the stretching vibrations of C=C bonds,49-51 suggesting\nthe formation of carbon species and the fast coke deposition on the catalyst surface.\nConcurrently, no signals at 1072 cm-1, characteristic of *CH O species, are detected.\nx\ncages during the DRM reaction (Fig. 4b) and their rapid deactivation in catalytic\nperformance (Fig. 4a). Based on the above results, it can be reasonably inferred that\nthe DRM pathway over Ag@Ir-cages proceeds through the following steps: 1) CH\n4\nand CO are dissociated into (*CH + *H) and (*CO + *O), respectively; 2) *CH\n2 x x\nsubsequently reacts with *O to form *CH O, which further dissociates into (*CO +\nx\n*H); 3) *CO desorbs to produce CO, while *H species couple to form H .\nThis suggests the *CH→*CHO pathway dominates on Ag@Ir(111), which is\nconsistent with the in-situ FTIR results that shows remarkable signals corresponding\nto *CH O species during the DRM reaction (Fig. 5b, c). In contrast, *CH would\nx\nprefer to be converted into *C rather than *CHO on the surface of Ir(111), as\nevidenced by the greater energetic favorability of the *CH→*C pathway relative to\nthe *CH→*CHO pathway (Fig. 5f). Furthermore, the subsequent oxidation of *C to\n*CO on Ir(111) is severely impeded due to a high thermodynamic barrier of 3.24 eV,\nsuggesting the occurrence of carbon deposition. These findings are highly consistent\nwith the in-situ FTIR results, which show remarkable signals corresponding to carbon\nspecies but no detectable signals for *CH O species, thereby providing a rational\nx\nexplanation for the significant coke deposition and the rapid deactivation observed\nover Ir-cages during the DRM reaction (Fig. 4a, b).\nRevision in Supplementary Information\nPage S15\ncollected at different irradiation time.\n44"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The revision can be accepted.", "reviewer_2": "The authors have responded satisfactorily to all the points raised. The manuscript is now fit for publication in Nature Communications journal.", "reviewer_3": "The author has answered my question very well. I agree to accept this article."}, "author_response": "Response Letter\nManuscript ID: NCOMMS-25-56446A\nTitle: Concentrating and Directing Energy Flow in Plasmonic Heterostructures\nfor Stable and Efficient Light-driven Methane Dry Reforming\nReviewer #1:\nThe revision can be accepted.\nAnswer:\nWe would like to express our sincere thanks to you for the recognition of our research.\nYour valuable suggestions are immensely constructive for enhancing our paper.\nReviewer #2:\nThe authors have responded satisfactorily to all the points raised. The manuscript is\nnow fit for publication in Nature Communications journal.\nAnswer:\nWe sincerely appreciate your positive feedback on our work. The insightful comments\nand valuable suggestions you provided significantly enhanced the quality of our\nmanuscript.\nReviewer #3:\nThe author has answered my question very well. I agree to accept this article.\nAnswer:\nWe are truly grateful for your positive feedback and diligent work. Your insightful\ncomments and suggestions have greatly improved the rigor and clarity of our\nmanuscript."}]

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