Plasmon-Enhanced Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde Using BiVO₄/BiOBr/Au Nanosheets

Plasmonic Au nanoparticles were deposited over photocatalytic BiVO4/BiOBr nanosheets with different loadings in the range of 0.5–5% (w/w) to boost the photocatalytic reactivity via surface plasmonic resonance. The results showed that the highest benzyl alcohol conversion (100%) and the maximum benzaldehyde yield (99%) were obtained using BiVO4/BiOBr/Au 3% after 4 h of irradiation. Electron paramagnetic resonance analysis and trapping experiments revealed that singlet oxygen is the dominant species produced within the system and suggest that it is the main species driving photocatalytic oxidation of benzyl alcohol to benzaldehyde. The proposed mechanism involves irradiation of BiVO4/BiOBr/Au with light to excite its electrons to the singlet state and produce singlet excitons, which eventually produces triplet excitons via intersystem crossing. Dissolved O2 subsequently reacts with these triplet excitons to produce singlet oxygen. Moreover, the energy barrier and the intrinsic reaction indicated that the reaction is thermodynamically favorable. These results demonstrate the unique effects of plasmonic resonance on photocatalytic activity, which can be adapted to different selective oxidation reactions.