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.