Directional Activation of Oxygen by the Au‐Loaded ZnAl‐LDH with Defect Structure for Highly Efficient Photocatalytic Oxidative Coupling of Methane

Photocatalytic oxidative coupling of CH₄ (OCM) is a promising CH₄ conversion process that can achieve efficient methane conversion with the assistance of O₂. It remains to be highly challenging to improve the photocatalytic OCM activity from catalyst design and to deepen the understanding of the reactant activation in the OCM process. In this work, the Au-loaded ZnAl-layered double hydroxides (LDHs) with and without oxygen vacancy are constructed (denoted as Au/ZnAl and Au/ZnAl-v), respectively. When applied for photocatalytic OCM, the Au/ZnAl-v shows a CH₄ conversion rate of 8.5 mmol g^-1 h^-1 with 92% selectivity of C₂H₆ at 40 °C, outperforming most reported photocatalytic OCM systems at low temperature reported in the literature. Furthermore, the catalytic performance of Au/ZnAl-v can be stable for 100 h. In contrast, the An/ZnAl exhibits a CH₄ conversion rate of 0.8 mmol g^-1 h^-1 with 46% selectivity of C₂H₆. Detailed characterizations and DFT calculation studies reveal that the introduced Ov sites on Au/ZnAl-v are able to activate O₂, and the resulting superoxide radical O₂·^- greatly promotes the activation of CH₄. The coupling of CH₃· groups with the assistance of Au cocatalyst leads to the formation of C₂H₆ with high photocatalytic activity.