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

Photocatalytic CH 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 C products, instead of the kinetically sluggish C-C coupling to produce ethanol. Herein, we developed a BiVO photocatalyst with surface functionalization of Au nanoparticles (BiVO@Au), which not only enables photogeneration of ⋅OH to activate CH into ⋅CH, but also in situ consumes those ⋅OH species to retard their further attack on ⋅CH, resulting in an enhanced ⋅CH/⋅OH ratio and facilitating C-C coupling toward ethanol. The ⋅CH/⋅OH ratio is further improved by transporting CH 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 BiVO@Au photocatalyst exhibited an outstanding CH-to-ethanol conversion performance, including a peak ethanol yield of 680 μmol ⋅ g ⋅ h, 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 CH conversion toward multi-carbon products.