Highly Selective Photocatalytic Methane Coupling by Au-Modified Bi₂WO₆

Photocatalytic oxidative coupling of methane (OCM) to ethane promises a route to value-added C-2 products from an abundant and low-cost feedstock. However, selective activation of the C-H bond of CH4 without overoxidation to CO2 has been a major challenge. In this work, we present the use of Au-modified Bi2WO6 as a prototypical photocatalyst, demonstrating a high performance of OCM through photocatalysis. A C2H6 production rate at 1.69 x 10(3) mu molg(-1)h(-1) with approximately 85% selectivity was achieved, which ranks among the top-performing photocatalytic OCM systems. Efforts were also made in establishing a correlation between improved OCM performance and the photocatalyst system by examining the nature of the oxide photocatalyst. Our findings indicated that oxygen within the oxide surface, likely from adsorbed and subsequently dissociated oxygen at the vacancy sites, afforded a desired reactivity to selectively activate the C-H bond without significant overoxidation. Surprisingly, it was revealed that the Au cocatalyst plays dual roles of activating the oxide photocatalyst for enhanced CH4 activation and promoting C-C coupling to yield C2H6 as the main product.