Regulating Reactive Oxygen Species with H2 over PdCu/ZnO for Selective Photocatalytic Aerobic Oxidation of Methane to Methanol

Photocatalytic aerobic oxidation of methane (CH4) to methanol (CH3OH) offers an alternative to the current energy-intensive route for CH4 utilization, while suffering from the activity-selectivity trade-off due to the uncontrolled generation of reactive oxygen species (ROS). Herein, we perform the photocatalytic CH4 aerobic oxidation in the presence of H2 over a PdCu NPs-modified ZnO catalyst, which exhibits a CH3OH yield of 13.5 mmol gcat–1 h–1 and a selectivity of 71.1%, surpassing many previously reported results. The introduction of H2 enables more ROS production simultaneously from photoelectron-induced O2 reduction and in situ-produced H2O2, facilitating the conversion of CH4. Compared to Pd, the PdCu cocatalyst favors the generation of more •OOH radicals in the ROS. More importantly, it is proposed that intermediate CH3OOH can be converted to CH3OH by H2-derived Pd–H species, which could also scavenge the excessive •OH radicals and holes, thus promoting the productivity of CH3OH and suppressing overoxidation. This work provides a strategy to regulate ROS formation for efficient CH4 oxidation into CH3OH under mild conditions.