Regulating Reactive Oxygen Species with H ₂ over PdCu/ZnO for Selective Photocatalytic Aerobic Oxidation of Methane to Methanol

Photocatalytic aerobic oxidation of methane (CH 4 ) to methanol (CH 3 OH) offers an alternative to the current energy-intensive route for CH 4 utilization, while suffering from the activity-selectivity trade-off due to the uncontrolled generation of reactive oxygen species (ROS). Herein, we perform the photocatalytic CH 4 aerobic oxidation in the presence of H 2 over a PdCu NPs-modified ZnO catalyst, which exhibits a CH 3 OH yield of 13.5 mmol g cat –1 h –1 and a selectivity of 71.1%, surpassing many previously reported results. The introduction of H 2 enables more ROS production simultaneously from photoelectron-induced O 2 reduction and in situ-produced H 2 O 2, facilitating the conversion of CH 4 . Compared to Pd, the PdCu cocatalyst favors the generation of more •OOH radicals in the ROS. More importantly, it is proposed that intermediate CH 3 OOH can be converted to CH 3 OH by H 2 -derived Pd–H species, which could also scavenge the excessive •OH radicals and holes, thus promoting the productivity of CH 3 OH and suppressing overoxidation. This work provides a strategy to regulate ROS formation for efficient CH 4 oxidation into CH 3 OH under mild conditions.