An atomically dispersed Pt/γ-Mo₂N(O_0.3) catalyst for hydrogen production via aqueous-phase reforming of methanol†

Yeteng Gong‡ ^a, Hengyue Xu‡^b, Yongsheng Li^d, Yaxuan Jing*^ce, Xiaohui Liu^a, Yanqin Wang*^a and Yong Guo*^ad
aState Key Laboratory of Green Chemical Engineering and Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China. E-mail: wangyanqin@ecust.edu.cn; guoyong@ecust.edu.cn
^bDepartment of Chemistry, Tsinghua University, Beijing 100084, China
^cState Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China. E-mail: yaxuan.jing@nju.edu.cn
^dSchool of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003, P. R. China
^eInstitute for the Environment and Health, Nanjing University Suzhou Campus, Suzhou 215163, China

First published on 8th July 2025

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Green foundation 1. We developed a low-energy, high-efficiency catalytic system for hydrogen production via aqueous-phase reforming of methanol. 2. The developed Pt/γ-Mo2N(O0.3) catalyst with low Pt loading gave an ATOF of 14813 h−1, surpassing traditional oxide-supported catalysts (e.g., Pt/γ-Al2O3: 294 h−1) by two orders of magnitude. 3. Replacing Pt with non-precious metals and developing methods to regenerate degraded catalysts, extending lifespan and reducing waste, could achieve net-zero carbon emissions and broader industrial applicability in sustainable hydrogen economies.

1 Introduction

Hydrogen-driven polymer electrolyte membrane fuel cells (PEMFCs) are widely recognized as a promising alternative energy technology due to their high energy utilization efficiency and zero carbon emission,^1–4 particularly in mobile applications such as fuel cell vehicles.⁵ The in situ release of hydrogen from stable liquid hydrogen carriers is highly desirable, considering the challenges associated with hydrogen storage and delivery, as well as the convenience of fuel adding.^4,6–8 Methanol, an inexpensive bulk chemical, has been identified as a suitable hydrogen carrier, as it can release 18.8 wt% of its weight as hydrogen through reforming with water (CH₃OH + H₂O = CO₂ + 3H₂).^6,9–11 Compared to conventional methanol steam reforming, aqueous phase reforming (APR) presents distinct advantages for mobile applications, because APR operates at lower temperatures, eliminates the need for a vaporization unit, and produces only trace amounts of CO,^12–15 making it particularly suitable for direct integration into PEMFC stacks.^9,10,16 Achieving a high hydrogen production rate is critical to ensure an efficient hydrogen supply. Furthermore, since APR is conducted under hot aqueous conditions, catalysts must exhibit robust hydrothermal stability to withstand potential structural and chemical degradation. This highlights the necessity for advanced catalyst design to overcome these challenges, enabling the practical implementation of APR in hydrogen-driven energy systems.

In the APR of methanol, the generally recognized reaction pathway involves sequential steps, beginning with methanol activation through C–H/O–H dehydrogenation to generate CO, followed by the conversion of CO into CO₂ and H₂ via the water gas shift (WGS) reaction.^11,17,18 Several critical insights have been established: (1) methanol dehydrogenation primarily occurs at metal sites, with platinum-, palladium-, ruthenium- and nickel-based catalysts being demonstrated to effectively facilitate this process.^{11,12,17,19–21} Notably, single-atom or atomically dispersed catalysts exhibit superior efficiency in methanol dehydrogenation.^9,10 (2) The activation of H₂O is crucial for achieving higher catalytic efficiency and predominantly takes place at the metal–support interface.^22–24 (3) Metal species in the electron-deficient state can mitigate CO toxicity and facilitate the low-temperature WGS reaction.^22,23,25 Based on these insights, atomically dispersed catalysts emerge as ideal candidates to meet these requirements, owing to their high density of interfacial sites and electron-deficient properties.

Previous reports have demonstrated that supports with the face-centred-cubic (fcc) structure typically exhibit stronger interactions with active metal species,^9,26,27 favoring the formation of atomically dispersed catalysts upon metal loading.^28–30 Among various catalytic systems, Pt/α-MoC is recognized as one of the most active catalytic systems.^9,25 However, the synthesis of α-MoC involves a complex process, requiring the preparation of γ-MoN, followed by carbonization to produce α-MoC. To simplify the preparation process, we propose γ-MoN, which shares the same fcc structure as α-MoC, as an alternative support. This study aims to systematically investigate the structure, catalytic activity, and reaction mechanism of the Pt/γ-MoN system, providing valuable insights into its potential as an efficient and readily synthesized catalyst.

In this work, we present a novel atomically dispersed Pt/γ-Mo₂N(O_0.3) catalyst that demonstrates both high activity and selectivity, as well as excellent tolerance to hot aqueous conditions. The Pt/γ-Mo₂N(O_0.3) catalyst achieved an ATOF of 14813 mol_H2 mol_Pt⁻¹ h⁻¹ and the hydrogen production rate decreased only 11% after ten cycles, demonstrating exceptional stability. Catalyst characterization studies revealed that when γ-Mo₂N is used as a support, its bulk phase retains the γ-Mo₂N structure, while the surface incorporates partial oxygen species, forming a unique γ-Mo₂N(O_0.3) structure. The surface heterostructured oxide layers of γ-Mo₂N(O_0.3) promote the dispersion of Pt. The atomically dispersed Pt species and the interface between Pt and γ-Mo₂N(O_0.3) provide highly active sites for methanol dehydrogenation and water dissociation, respectively, contributing to the superior catalytic performance in APRM. Moreover, DFT calculations confirm that Pt/γ-Mo₂N(O_0.3) with surface partial MoO_x species is kinetically favorable for the overall reaction.

2 Experimental section

2.1 Materials

Methanol (99.99%) was purchased from Shanghai Titan Scientific Co. Ltd. (NH₄)₆Mo₇O₂₄·4H₂O was purchased from Sinopharm Chemical Reagent Co., Ltd. H₂PtCl₆·6H₂O was bought from the Northwest Institute for Non-Ferrous Metal Research. All the above chemicals were analytical reagents and used directly as received. Nickel(II) nitrate hexahydrate and aluminum nitrate nonahydrate were purchased from Sinopharm Chemical Reagent Co., Ltd. Ammonium hydroxide was obtained from Shanghai Titan Scientific Co., Ltd. NH₃ was bought from Shanghai HaoQi Gas Co., Ltd. Pure water was obtained by laboratory purification. Ultrapure water was produced using a laboratory water system.

2.2 Catalyst preparation

2.3 Catalyst characterization

Powder X-ray diffraction (XRD) patterns were recorded using a D8 Focus diffractometer by using Cu Kα1 (λ = 0.15406 nm) radiation. The operation condition was 2.2 kW.

A Micromeritics ASAP 2020 M sorption analyzer was used for the nitrogen adsorption–desorption measurements. Before measuring at −196 °C, the samples were degassed at 200 °C for 6 h. The specific surface area was calculated according to the Brunauer–Emmett–Teller (BET) equation.

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to determine the Pt actual loading content, which was conducted on Agilent 725ES equipment.

In situ X-ray photoelectron spectra (XPS) experiments were carried out on a Thermo Scientific ESCALAB 250Xi equipped with an Al Kα (1486.6 eV) X-ray source. Prior to the test, the sample was reduced in situ at 300 °C for 2 h under 10% H₂/Ar. All binding energies were externally calibrated using the carbonaceous C 1s line (284.6 eV).

High-angle annular dark-field (HAADF)-STEM images were collected on an FEI Talos F200X G2 electron microscope at 200 kV and recorded with a convergence semi-angle of 11 mrad and inner and outer collection angles of 59 and 200 mrad, respectively.

Morphology and elemental distribution of the catalysts were analyzed by aberration-corrected STEM operated on a Thermo Fisher Themis Z transmission electron microscope equipped with two aberration correctors.

The Pt L₃-edge X-ray absorption spectroscopy (XAS) was carried out in the fluorescence mode at the Beamline 44A of the Peking Photon Source.

In situ Raman spectra were collected using a Horiba LabRam-HR spectrometer equipped with visible laser excitation at 514 nm generated using a He–Cd laser. The program of the in situ test was as follows: the sample was purged by Ar at 300 °C for 30 min. Then it was reduced at 300 °C for 30 min under a 10% H₂/Ar flow. After switching to Ar, the Raman signals were recorded at 300 °C and room temperature, respectively. The gas flow rates for the above tests were all 10 mL min⁻¹, and the Raman spectra were collected after each gas or the temperature was changed. The scanning range was 100–2000 cm⁻¹.

Temperature-programmed surface reactions (TPSRs) were employed to examine the surface reaction of methanol and water. Before analysis, we pretreated about 100 mg of the passivated catalyst at 300 °C for 2 h in 10% H₂/Ar in a quartz tube and then cooled to room temperature. Then the system was purged with Ar for 1 h to remove the desorbed molecules. A saturated mixture of methanol and water vapor was introduced into the system using a 30 ml min⁻¹ argon flow from a bubbler at 25 °C. We controlled the P_methanol/P_water at 1 in the gas phase according to the phase diagram for the methanol–water system. Then, the test sample was heated to 500 °C at a rate of 5 °C min⁻¹ under 30 ml min⁻¹ argon flow. Signals of H₂ (m/z = 2), He (m/z = 4), CH₄ (m/z = 15), H₂O (m/z = 18), CO (m/z = 28), CH₃OH (m/z = 31), CO₂ (m/z = 44), HCOOH (m/z = 45), HCHO (m/z = 30) and HCOOCH₃ (m/z = 60) were recorded with a mass spectrometer.

2.4 Catalytic activity tests

Before each evaluation, the catalyst was activated at 300 °C for 3 h in a H₂/Ar mixture. After the activated catalyst has cooled to room temperature, it is transferred to the autoclave and then added methanol aqueous solution. The sealed autoclave was purged with 0.5 MPa N₂ three times and then charged to 3 MPa. The catalytic reactions were carried out at 210 °C, and after the reaction, the gas phase was analyzed by using a gas chromatograph with a methanator, a flame ionization detector (FID) and a thermal conductivity detector (TCD). The amounts of generated H₂, CO, and CH₄ were quantified directly according to the GC analysis data. The concentration of CO₂ could not be accurately determined owing to its high solubility in the liquid phase, especially at high pressure. We measured the activity in the methanol-reforming reaction through the H₂ production rate. The selectivity to gaseous carbon products (i = CO_x and CH₄) was calculated as follows:

2.5 Computational details

3 Results and discussion

3.1 Identification of the geometry and electronic structures of Pt/γ-Mo₂N(O_0.3)

To elucidate the geometry and electronic structures of the prepared Pt/γ-Mo₂N catalysts with different Pt loadings (1 wt% and 0.2 wt%), various characterization studies were performed. First, scanning transmission electron microscopy (STEM) was employed to observe the distribution of Pt in Pt/γ-Mo₂N catalysts. The simultaneously obtained bright-field (BF) images show that γ-Mo₂N consisted of nanoparticle aggregates with diameters ranging from 10 to 20 nm (Fig. S2†). To further identify the spatial distribution of Pt species on γ-Mo₂N, Z-contrast STEM-HAADF imaging combined with energy-dispersive X-ray spectroscopy (EDS) mapping was performed. As shown in Fig. 1(a) and (e), Pt was highly dispersed in both 1% Pt/γ-Mo₂N and 0.2% Pt/γ-Mo₂N catalysts. In the case of the 1% Pt/γ-Mo₂N catalyst, atomically dispersed Pt species were predominantly observed alongside Pt nanoclusters measuring approximately 0.5–1.5 nm. For the 0.2% Pt/γ-Mo₂N catalyst, the Pt species were primarily atomically dispersed, although a Pt nanocluster with a size of ∼0.7 nm was detected upon detailed examination of several regions. Elemental mapping images (Fig. 1(c–h)) further confirmed that both atomically dispersed Pt species and Pt nanoclusters were uniformly distributed in 1% Pt/γ-Mo₂N. In contrast, the Pt species in 0.2% Pt/γ-Mo₂N were highly atomically dispersed. Overall, the STEM analysis demonstrates a clear distinction between the two catalysts: 0.2% Pt/γ-Mo₂N predominantly features atomically dispersed Pt species, whereas 1% Pt/γ-Mo₂N contains both atomically dispersed Pt and Pt nanoclusters.

The XRD pattern (Fig. 1(i)) of the synthesized support only shows the diffraction peaks corresponding to γ-Mo₂N, indicating its successful formation from MoO₃. After loading Pt, no diffraction peaks of Pt were observed, likely due to the low Pt loading and high dispersion. In situ X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and extended X-ray-absorption fine-structure (EXAFS) analysis were performed to determine the nature of the Pt species in the two catalysts. The Pt species in 1% Pt/γ-Mo₂N exhibit three different valence states, predominantly in the form of low-valence states (Pt⁰) (Fig. 1(j)). In contrast, in the 0.2% Pt/γ-Mo₂N catalyst, the binding energy of Pt 4f_7/2 is 71.68 eV, approximately 0.7 eV higher than that of metallic Pt⁰ (Fig. 1k).^9,41,42 This observation suggests that Pt species exist in an electron-deficient state on the 0.2% Pt/γ-Mo₂N catalyst. To further investigate the chemical state of the Pt species, X-ray absorption near edge structure (XANES) analysis was conducted. Generally, the intensity of the “white line” correlates with the oxidation state of Pt, where a higher intensity indicates a more oxidized state and a lower intensity reflects a more reduced state.⁴³ As shown in Fig. 1(l), the white lines of the 0.2% Pt/γ-Mo₂N catalyst were higher than those of the 1% Pt/γ-Mo₂N catalyst. This finding suggests that the Pt species in the 0.2% Pt/γ-Mo₂N catalyst are more electron-deficient than those in the 1% Pt/γ-Mo₂N catalyst, consistent with the XPS results. Subsequently, EXAFS analysis was performed to determine the chemical environment of the Pt species. However, due to the extremely low Pt loading in the 0.2% Pt/γ-Mo₂N catalyst, the EXAFS signal at the R space was too weak to extract meaningful structural information. In contrast, the EXAFS results for the 1% Pt/γ-Mo₂N catalyst revealed the presence of Pt–N and Pt–O coordination shells, along with an extremely low Pt–Pt coordination.

To gain further insights into the oxygen species, we analyzed the XPS results of oxygen atoms on the surfaces of 0.2% Pt/γ-Mo₂N and Pt/MoO₃. As shown in Fig. 1(m), the peaks correspond to lattice oxygen in the range of 530.7–531 eV, oxygen-deficient regions around ∼531.7 eV, and adsorbed oxygen in the range of 523.3–532.7 eV (e.g., adsorbed H₂O, O₂, etc.).^39–44 The two primary lattice oxygen species are attributed to MoN_xO_γ and MoO₃,^27,45,46 resulting from the reactive nature of the γ-Mo₂N surface, which undergoes oxidation upon exposure to atmospheric oxygen, thereby generating oxygen-containing species. As expected, abundant O species were observed on the surface of 0.2% Pt/γ-Mo₂N. Notably, the lattice oxygen on the surface of 0.2% Pt/γ-Mo₂N exhibited a lower binding energy of 529.8 eV, approximately 0.8 eV lower than that of Pt/MoO₃. These unique oxygen species may correspond to oxygen species coordinated with Pt, which would play an important role in regulating the properties of Pt sites.

Although no diffraction peaks of MoO_x were detected by XRD, the existence of MoO_x species is suspected due to the high oxygen affinity of Mo^27,47,48 and unavoidable exposure to air during sample preparation. To further investigate the possible existence of MoO_x species, Raman spectroscopy was employed to analyze γ-Mo₂N and 0.2 wt% Pt/γ-Mo₂N. The bands at ∼224 cm⁻¹ (δ(Mo–O–Mo)) and ∼940 cm⁻¹ (ν_as(O)₂MoO₂) (Fig. 1(n)) were clearly observed, corresponding to the isolated surface dioxo sites,^49–51 which confirm the formation of MoO_x species on the support surface. Despite the presence of MoO_x species on the surface, their quantity appears to be very low, and the catalyst support predominantly maintains the γ-Mo₂N phase.

Based on the above characterization studies, we confirm the successful synthesis of the 0.2 wt% Pt/γ-Mo₂N catalyst with atomically dispersed Pt species. Moreover, the γ-Mo₂N support contains surface partial MoO_x species, which are coordinated with Pt. According to the surface element distribution results (Pt, Mo, N and O) obtained from XPS in Table S2,† the 0.2 wt% Pt/γ-Mo₂N catalyst is named Pt/γ-Mo₂N(O_0.3).

3.2 Catalytic performance of Pt/γ-Mo₂N(O_0.3) in APRM

Next, we evaluated the catalytic performance of Pt/γ-Mo₂N(O_0.3) compared to Pt-based catalysts supported on conventional metal oxides. As shown in Fig. 2(a) and listed in Table S3,† Pt/γ-Al₂O₃, a commonly used catalyst for APR, exhibited a hydrogen production rate of 252 μmol_H2 g_cat⁻¹ min⁻¹ with an ATOF of 294 mol_H2 mol_Pt⁻¹ h⁻¹. At the same time, Pt/γ-Mo₂N(O_0.3) catalysts also showed extremely low CO selectivity, accounting for only 0.9% in carbon-containing gases and merely 0.1% in all gaseous products. Therefore, the hydrogen produced through the APRM reaction using the Pt/γ-Mo₂N(O_0.3) catalyst meets the application requirements for PEMFC vehicles. In a previous study, Pt/NiAl₂O₄, which demonstrated high efficacy in a continuous-flow fixed-bed reactor,¹¹ achieved a hydrogen production rate of 438 μmol_H2 g_cat⁻¹ min⁻¹ with an ATOF of 512 mol_H2 mol_Pt⁻¹ h⁻¹. Pt/MoO₃ displayed poor performance with an ATOF of only 114 mol_H2 mol_Pt⁻¹ h⁻¹. In contrast, the Pt/γ-Mo₂N(O_0.3) catalysts showed significantly enhanced catalytic activity. Specifically, the hydrogen production rate reached 4242 μmol_H2 g_cat⁻¹ min⁻¹ on 1% Pt/γ-Mo₂N(O_0.3) and 2532 mol_H2 mol_Pt⁻¹ h⁻¹ on 0.2% Pt/γ-Mo₂N(O_0.3), respectively, representing an order-of-magnitude improvement over traditional oxide-supported catalysts. Notably, varying the Pt precursor had minimal impact on catalytic activity, with the hydrogen production rate of 4243 μmol_H2 g_cat⁻¹ min⁻¹ (Pt(NO₃)₂) and 4968 mol_H2 mol_Pt⁻¹ h⁻¹ (H₂PtCl₆). Additionally, the Pt/γ-Mo₂N(O_0.3) catalysts demonstrated lower CH₄ selectivity compared to the oxide-supported catalysts. Furthermore, reducing the Pt loading from 1% to 0.2% in the Pt/γ-Mo₂N(O_0.3) catalyst further enhanced its intrinsic activity, achieving an exceptional ATOF of 14813 mol_H2 mol_Pt⁻¹ h⁻¹. As shown in Table S4,† the Pt/γ-Mo₂N(O_0.3) catalyst maintained excellent APRM activity across a wide temperature range, underscoring its superior performance and robustness. At varying reaction temperatures, the CO selectivity remained sufficiently high to meet the requirements for state-of-the-art PEMFC vehicle applications.

Then stability of Pt/γ-Mo₂N(O_0.3) was investigated and the results are presented in Fig. 2(b). In a 10-cycle test without the addition of extra methanol to the reaction system, Pt/γ-Mo₂N(O_0.3) achieved a total turnover number (TTN) of 111849 per Pt atom and a productivity of 2532 mol_H2 g_cat⁻¹ min⁻¹. After 10 cycles, the hydrogen production rate remained sufficiently high to meet the requirements for state-of-the-art PEMFC vehicle applications. Moreover, XRD analysis confirmed that the γ-Mo₂N phase was retained even after 10 cycles, with only crystallinity changes observed in the structure (Fig. 1(i)). Based on calculations using the Scherrer formula, the grain size of pristine 0.2 wt% Pt/γ-Mo₂N was determined to be 25 nm, while that of the post-reaction 0.2 wt% Pt/γ-Mo₂N decreased to 21 nm. Therefore, prolonged hydrothermal treatment of the Pt/γ-Mo₂N catalyst led to changes in crystallinity; the crystal plane orientation shifted toward MoN, which had no obvious effect on the catalytic activity. The above results show that Pt/γ-Mo₂N(O_0.3) is both stable and highly efficient for APRM, highlighting its potential for long-term applications.

3.3 Catalytic mechanism on Pt/γ-Mo₂N(O_0.3)

Next the focus is placed on exploring the catalytic mechanism of APRM on Pt/γ-Mo₂N(O_0.3). As presented in Table S5,† the methanol dehydrogenation experiments demonstrate that the Pt/γ-Mo₂N(O_0.3) catalyst exhibits superior methanol dehydrogenation rates across various temperature ranges. To compare the intermediates and reaction pathways over atomically dispersed Pt/γ-Mo₂N(O_0.3) and conventional Pt/γ-Al₂O₃ catalysts, temperature-programmed surface reactions (TPSRs) were conducted. As shown in Fig. 3(a) and S3,† the reaction mechanisms of the two catalysts differ significantly. Notably, the temperature at which CO₂ and H₂ are generated on Pt/γ-Mo₂N(O_0.3) is lower than that on Pt/γ-Al₂O₃, which is consistent with the activity evaluation results. At the beginning of the reaction, CH₃OH consumption is minimal due to the slow reaction rate at low temperatures, leading to a discrepancy between CH₃OH input and consumption. Interestingly, as the temperature increased, no formic acid intermediate species were detected on Pt/γ-Mo₂N(O_0.3), while a strong formic acid signal appeared on Pt/γ-Al₂O₃. For the latter, the complete decomposition or desorption of formic acid occurred only at temperatures exceeding 300 °C. These findings indicate the different reaction pathways on the two catalysts: On Pt/γ-Mo₂N(O_0.3), the APRM proceeds primarily through the direct decomposition of CH₃OH into CO and H₂, followed by the WGS reaction between CO and H₂O to produce CO₂ and H₂. In contrast, the APRM on Pt/γ-Al₂O₃ predominantly follows the more challenging formate pathway. Furthermore, TPSR analysis of the WGS reaction on Pt/γ-Mo₂N(O_0.3) also confirmed the absence of formate species during the reaction (Fig. 3(b)). It is worth noting that the decomposition of formic acid is kinetically challenging. Consequently, the reforming activity tends to be lower when the reaction follows the formic acid pathway. In short, Pt/γ-Mo₂N(O_0.3) demonstrates superior activity due to its ability to facilitate a redox mechanism after methanol dehydrogenation to CO. This is attributed to the maximized exposed active interface of Pt/γ-Mo₂N(O_0.3), which exhibits high activity for water dissociation.

In order to verify the role of surface partial MoO_x species in Pt/γ-Mo₂N(O_0.3), DFT calculations were conducted to compare the energy barriers on Pt₁/γ-Mo₂N(O_0.3) and Pt₁/γ-Mo₂N. Based on the STEM analysis and the coordination results derived from XAENS, two catalyst models (Pt₁/γ-Mo₂N(O_0.3) and Pt₁/γ-Mo₂N) were constructed, which were constructed to accurately represent the actual catalytic system. The constructed surface slab models are shown in Fig. S5.† Detailed reaction pathway calculations reveal that the rate-determining steps differ between the two catalysts during methanol dehydrogenation. On the Pt₁/γ-Mo₂N(111) surface, the transition state TS4, with an energy barrier of 2.60 eV, represents the formation of CO and H from CHO and H, thereby establishing it as the rate-limiting step in the methanol dehydrogenation pathway. On the Pt₁/γ-Mo₂N(O_0.3)(111) surface, the first transition state (TS1) for dissociation into CH₃O and H exhibits the highest energy barrier of 1.04 eV, obviously lower than that of the rate-limiting step TS4 on the Pt₁/γ-Mo₂N(111) surface. While both Pt₁/γ-Mo₂N(111) and Pt₁/γ-Mo₂N(O_0.3)(111) surfaces demonstrate potential for methanol dehydrogenation, the Pt₁/γ-Mo₂N(O_0.3)(111) surface offers a more efficient pathway due to its lower rate-determining barrier for CO formation.

Additionally, during the WGS reaction, the Pt₁/γ-Mo₂N(O_0.3)(111) surface demonstrates stronger reaction capability. On the Pt₁/γ-Mo₂N(111) surface, the energy barrier for the rate-determining step, namely the reaction between *OH with CO after dissociation, is 2.16 eV (TS6), whereas the same step on the Pt₁/γ-Mo₂N(O_0.3) (111) surface is even exothermic by 0.27 eV. On the Pt₁/γ-Mo₂N(O_0.3)(111) surface, the highest energy barrier corresponds to TS5 (1.01 eV), associated with the formation of H₂O from OH and H, which is significantly lower than the energy required for TS6 on the Pt₁/γ-Mo₂N(111) surface. In the water dissociation experiments, it was observed that unmodified γ-Mo₂N(O_0.3) required heating to 183 °C to achieve H₂O dissociation with minimal hydrogen production, whereas the Pt-loaded catalyst enabled efficient dissociation at a significantly lower temperature of 106 °C (as shown in Fig. S6†). This experimental outcome provides direct validation of our DFT findings, conclusively demonstrating that the Pt–O/N interfacial sites exhibit a synergistic effect that enables highly efficient H₂O dissociation. In summary, the synergistic effect between Pt and the surface partial MoO_x species in γ-Mo₂N(O_0.3) significantly reduces the reaction energy barriers for the WGS process. Overall, the Pt/γ-Mo₂N(O_0.3) catalyst exhibits significant kinetic advantages for both methanol dehydrogenation and WGS reaction steps, contributing to its superior overall performance.

4 Conclusion

In summary, we have developed an atomically dispersed Pt/γ-Mo₂N(O_0.3) catalyst, which enables the low-temperature APRM process with outstanding hydrogen production activity and stability. The atomically dispersed Pt species favors methanol dehydrogenation and maximizes the exposed active interface of Pt/γ-Mo₂N(O_0.3), which promotes efficient water dissociation. Moreover, Pt/γ-Mo₂N(O_0.3) with surface partial MoO_x species exhibits significant kinetic advantages for the overall reaction. This innovative catalyst represents a significant step forward in realizing a commercially viable hydrogen storage strategy.

Conflicts of interest

The authors declare no conflict of interest.

Data availability

Data collected for this research are available in the ESI.†

Acknowledgements

This work is financially supported by the National Natural Science Foundation of China (No. U23A20641, 22072041), the National Key Research and Development Program of China (2022YFA1504900), the Science and Technology Commission of Shanghai Municipality (10dz2220500), and the Fundamental Research Funds for the Central Universities (14380001).

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Footnotes

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5gc02092a

‡ These two authors contributed equally to this work.

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