Low-Loading Gold Nanoclusters on Zinc Oxide Enable Efficient Photocatalytic Oxidative Coupling of Methane

Abstract

Photocatalytic oxidative coupling of methane (POCM) is a promising strategy for the production of sustainable C₂₊ hydrocarbons; however, it typically relies on large quantities of noble metals, such as gold, to serve as active sites for methyl coupling. In this study, we demonstrate that ZnO-supported gold nanoclusters with an average diameter of 1.1 nm provide a robust alternative to conventional gold nanoparticles, enabling efficient POCM even at ultralow gold loadings of 0.1 wt%. The optimized photocatalyst affords a C₂–C₄ hydrocarbon production rate of 3.89 mmol/(g h) with 94.8% selectivity under 365 nm irradiation in a batch reactor. Results reveal that the abundant interfaces between highly dispersed gold nanoclusters and ZnO substrates facilitate charge carrier separation and promote a light-induced Mars–van Krevelen reaction pathway. Methyl adsorption causes gold nanoclusters to exhibit a more intense d-σ hybridization state compared to gold nanoparticles, enhancing electron transfer interactions and substantially reducing the transition-state energy barrier for methyl coupling.

Keywords

Photocatalysis / Oxidative coupling of methane / Nanoclusters / Zinc oxide / Natural gas

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