Integrating photochemical and photothermal effects for selective oxidative coupling of methane into C₂₊ hydrocarbons with multiple active sites.

Abstract

The direct photocatalytic oxidation of methane to value-added chemicals has garnered considerable interest in recent years. However, achieving high productivity while maintaining high selectivity at an appreciable methane conversion rate remains a formidable challenge. Here, we present photochemically-triggered and photothermally-enhanced oxidative coupling of methane to multi-carbon C₂₊ alkanes over an Au and CeO₂ nanoparticle-decorated ZnO photocatalyst, which exhibits a record-breaking C₂₊ production rate of 17,260 μmol g^-1 h^-1 with ~90% C₂₊ selectivity under wide-spectrum light irradiation without a secondary source of heating. Comprehensive characterizations and computational studies reveal that CH₄ activation is a photochemical reaction initiated by ultraviolet light-excited ZnO, and the introduction of CeO₂ substantially enhances the activation of CH₄ and O₂ due to the cooperative interaction between Au and CeO₂. Concurrently, Au nanoparticles capture visible and near-infrared light to generate localized heating, which greatly promotes the subsequent desorption of produced methyl radical for C-C coupling prior to undergoing further undesired overoxidation.