Environmentally sustainable and selective conversion of methane to valuable chemicals under ambient conditions is pivotal for the development of next‐generation photocatalytic technology. However, due to the lack of microscopic knowledge about non‐thermal methane conversion, controlling and modulating photocatalytic oxidation processes driven by photogenerated holes remain a challenge. Here, we report novel function of metal cocatalysts to accept photogenerated holes and dominate selectivity of methane oxidation, which is clearly beyond the conventional concept in photocatalysis that the metal cocatalysts loaded on the surfaces of semiconductor photocatalysts mostly capture photogenerated electrons and dominate reduction reactions exclusively. The novel photocatalytic role of metal cocatalysts was verified by operando molecular spectroscopy combined with real‐time mass spectrometry for metal‐loaded Ga2O3 model photocatalysts under methane and water vapor at ambient temperature and pressure. Our concept of metal cocatalysts that work as active sites for both photocatalytic oxidation and reduction provides a new understanding of photocatalysis and a solid basis for controlling non‐thermal redox reactions by metal‐cocatalyst engineering.

On-site and on-demand photocatalytic methane conversion under mild conditions is one of the urgent global challenges for the sustainable use of ubiquitous methane resources. However, the lack of accurate knowledge of the reaction mechanism prevents the development of engineering strategies for methane photocatalysis. Combining real-time mass spectrometry and operando infrared absorption spectroscopy with ab initio molecular dynamics simulations, here we report key molecular-level insights into photocatalytic green utilization of methane. The photoactivated water dramatically promotes the activation of robust C–H bond of methane, and stabilizes the •CH3 intermediates in the interfacial hydrogen-bond network of water. Owing to the moderate stabilization of •CH3, the overall photocatalytic conversion rates are dramatically improved by typically more than 30 times at ambient temperatures (~300 K) and pressures (~1 atm). The increase in reaction activity is noticeable also in C1 to C2 evolution of methane, although water is not explicitly involved in the reaction equation (2CH4 → C2H6 + H2). These marked water-assisted effects in the interfacial chemistry should affect the basic understanding and the designing strategies on the non-thermal heterogeneous catalysis of methane under ambient conditions.

Environmentally sustainable and selective conversion of methane to valuable chemicals under ambient conditions is pivotal for the development of next-generation photocatalytic technology. However, due to the lack of microscopic knowledge about nonthermal methane conversion, controlling and modulating photocatalytic oxidation processes driven by photogenerated holes remain a challenge. Here, we report novel function of metal cocatalysts to accept photogenerated holes and dominate selectivity of methane oxidation, which is clearly beyond the conventional concept in photocatalysis that the metal cocatalysts loaded on the surfaces of semiconductor photocatalysts mostly capture photogenerated electrons and dominate reduction reactions exclusively. The novel photocatalytic role of metal cocatalysts was verified by operando molecular spectroscopy combined with real-time mass spectrometry for metal-loaded Ga 2 O 3 model photocatalysts under methane and water vapor at ambient temperature and pressure. Our concept of metal cocatalysts that work as active sites for both photocatalytic oxidation and reduction provides a new understanding of photocatalysis and a solid basis for controlling non-thermal redox reactions by metal-cocatalyst engineering.

Environmentally sustainable and selective conversion of methane to valuable chemicals under ambient conditions is pivotal for the development of next-generation photocatalytic technology. However, due to the lack of microscopic knowledge about non-thermal methane conversion, controlling and modulating photocatalytic oxidation processes driven by photogenerated holes remain a challenge. Here, we report novel function of metal cocatalysts to accept photogenerated holes and dominate the oxidation selectivity of methane, which is clearly beyond the conventional concept in photocatalysis that the metal cocatalysts loaded on the surfaces of semiconductor photocatalysts mostly capture photogenerated electrons and dominate reduction reactions exclusively. The novel photocatalytic role of metal cocatalysts was verified by operando molecular spectroscopy combined with real-time mass spectrometry for metal-loaded Ga2O3 model photocatalysts under methane gas and water vapor at ambient temperature and pressure. Our concept of metal cocatalysts that work as active sites for both photocatalytic oxidation and reduction provides a new understanding of photocatalysis and a solid basis for controlling the non-thermal redox reactions by metal-cocatalyst engineering.