Efficient Photocatalytic CH4-to-Ethanol Conversion by Limiting Interfacial Hydroxyl Radicals Using Gold Nanoparticles

Abstract

Photocatalytic CH4 oxidation to ethanol with high selectivity is attractive but substantially challenging. The activation of inert C–H bonds at ambient conditions requires highly reactive oxygen species like hydroxyl radicals (·OH), while the presence of those oxidative species also facilitates fast formation of C1 products, instead of the kinetically sluggish C–C coupling to produce ethanol. Herein, we developed a BiVO4 photocatalyst with surface functionalization of Au nanoparticles (BiVO4@Au), which not only enables photogeneration of ·OH to activate CH4 into ·CH3, but also in-situ consumes those ·OH species to retard their further attack on ·CH3, resulting in an enhanced ·CH3/·OH ratio and facilitating C–C coupling toward ethanol. The ·CH3/·OH ratio is further improved by transporting CH4 via a gas-diffusion layer to the photocatalytic interface, leading to even higher ethanol selectivity and production rates. At ambient conditions and without photosensitizers or sacrificial agents, the BiVO4@Au photocatalyst exhibited an outstanding CH4-to-ethanol conversion performance, including a peak ethanol yield of 680 μmol·g-1·h-1, a high selectivity of 86%, and a stable photoconversion of > 100 h, substantially exceeding most of the previous reports. Our work suggests an attractive approach of in-situ generation and modulation of the ·OH levels for photocatalytic CH4 conversion toward multi-carbon products.