Understanding Au facet effects in photocatalytic nonoxidative coupling of methane

Abstract

The photocatalytic nonoxidative coupling of methane (NOCM) represents an appealing approach for addressing global warming and producing sustainable chemical commodities. However, the effectiveness of this process is hindered by the challenge of adsorbing and activating methane due to its high inertness. In this study, we synthesized Au/ZnO nanocomposites featuring different exposed facets of Au as co-catalysts and investigated their influence on the photocatalytic activity of NOCM. Our results indicate that Au octahedra with exposed (111) facets achieved the highest ethane yield of 21.0 μmol cm⁻² h⁻¹ under ambient temperature and pressure conditions, exceeding the yields of Au cubes with exposed (100) facets and Au rhombic dodecahedra with exposed (110) facets by 2.3 and 3.0 times, respectively. Through experimental and theoretical analyses, we found that the facet of Au co-catalysts had a negligible effect on the separation efficiency of photoinduced carriers and the activation ability of methane. However, the Au(111) facets exhibited the strongest adsorption capacity of methane compared to Au(100) and Au(110) facets, which was related to the greater electron richness of Au(111) facets, leading to stronger interaction with methane and enhanced photocatalytic performance. This study highlights the importance of facet engineering of co-catalysts to enhance the photocatalytic performance in methane conversion.