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.