Molecular oxygen enhances H 2 O 2 utilization for the photocatalytic conversion of methane to liquid-phase oxygenates.

H 2 O 2 is widely used as an oxidant for photocatalytic methane conversion to value-added chemicals over oxide-based photocatalysts under mild conditions, but suffers from low utilization efficiencies. Herein, we report that O 2 is an efficient molecular additive to enhance the utilization efficiency of H 2 O 2 by suppressing H 2 O 2 adsorption on oxides and consequent photogenerated holes-mediated H 2 O 2 dissociation into O 2 . In photocatalytic methane conversion over an anatase TiO 2 nanocrystals predominantly enclosed by the {001} facets (denoted as TiO 2 {001})-C 3 N 4 composite photocatalyst at room temperature and ambient pressure, O 2 additive significantly enhances the utilization efficiency of H 2 O 2 up to 93.3%, giving formic acid and liquid-phase oxygenates selectivities respectively of 69.8% and 97% and a formic acid yield of 486 μmol HCOOH ·g catalyst -1 ·h -1 . Efficient charge separation within TiO 2 {001}-C 3 N 4 heterojunctions, photogenerated holes-mediated activation of CH 4 into ·CH 3 radicals on TiO 2 {001} and photogenerated electrons-mediated activation of H 2 O 2 into ·OOH radicals on C 3 N 4 , and preferential dissociative adsorption of methanol on TiO 2 {001} are responsible for the active and selective photocatalytic conversion of methane to formic acid over TiO 2 {001}-C 3 N 4 composite photocatalyst.