Regulation of O2 activation pathway boosts efficient photocatalytic methane oxidation to methanol

Photocatalytic oxidation of methane to methanol is a promising process under mild conditions, nevertheless confronting great challenges in achieving high yield and selectivity of methanol simultaneously. Herein, we propose a strategy for the proper amount of hydroxyl radicals (•OH) generation from O2 by rational design of Au nanoparticles and oxygen vacancies (OVs) co-decorated ZnO photocatalysts. For photocatalytic methane oxidation at ambient temperature, a high CH3OH yield of 6.3 mmol·g−1·h−1 with a nearly 100 % selectivity has been achieved over the optimized Au2.5-def-ZnO (2.5 wt% Au and OVs co-decorated ZnO) photocatalyst, exceeding most reported literatures. Mechanism investigations revealed that Au nanoparticles and OVs synergistically promoted charge separation, improved the adsorption and activation of CH4 and O2, facilitating the selective generation of •OH from O2. Combined with the aqueous phase system, the over-oxidation of CH3OH was effectively inhibited, thereby achieving high yield and high selectivity of CH3OH simultaneously. This work provides some guidance for the design of high-performance photocatalysts for photocatalytic selective oxidation of methane to methanol.