Interstitial Zinc Defects Enriched ZnO Tuning O₂ Adsorption and Conversion Pathway for Superior Photocatalytic CH₄ Oxygenation

Abstract

Photocatalytic methane conversion into liquid oxygenates using O2 oxidants provides a promising approach for high-value chemicals. The generation of reactive oxygen species and their reaction pathway are key to determine the oxygenate selectivity. Here, an interstitial Zni defect ZnO (ZnO(Zni)) is developed through thermal decomposition of the ZnO2 precursor. Zni favors the O2 adsorption at a terminal adsorption configuration and induces effectively the conversion O2 into the desired •OOH instead of •OH for improving the yield and selectivity of oxygenates. For comparison, O2 adsorbed in a lateral configuration tends to be converted into excessive •OH on the typical Au/ZnO. As a result, ZnO(Zni) shows the liquid oxygenates yield of 6080 μmol g–1 with 98.6% selectivity, which leads to 10 times lower than Au/ZnO for CO2 release of overoxidation. This work provides a pathway for O2 adsorption and activation to regulate the photocatalytic CH4 oxidation conversion into liquid oxygenates.