Substrate-dependent photoreactivities of BiOBr nanoplates prepared at different pH values

In this study, we showed that BiOBr nanoplates prepared at different pH values have substrate-dependent photocatalytic activities under visible-light irradiation. The BiOBr nanoplates synthesized at pH 1 (BOB-1) degraded salicylic acid more effectively than did those obtained at pH 3 (BOB-3), but the order of their photocatalytic activities in rhodamine B (RhB) degradation were reversed. Electrochemical Mott–Schottky and zeta-potential measurements showed that BOB-1 had a more positive valence band and lower surface charge, leading to superior photocatalytic activity in salicylic acid degradation under visible light. However, BOB-3 was more powerful in RhB degradation because larger numbers of superoxide radicals were generated via electron injection from the excited RhB to its more negative conduction band under visible-light irradiation; this was confirmed using active oxygen species measurements and electron spin resonance analysis. This study deepens our understanding of the origins of organic-pollutant-dependent photoreactivities of semiconductors, and will help in designing highly active photocatalysts for environmental remediation.

Graphical AbstractBiOBr prepared at pH 1 more efficiently oxidized salicylic acid via photogenerated holes, because of its more positive valence band and poor adsorption ability. BiOBr prepared at pH 3 had superior rhodamine B degradation activity because of its more negative conduction band and better adsorption ability, which enhanced •O2− generation.Figure optionsDownload full-size imageDownload as PowerPoint slide