Surface Modulation of BiVO ₄ Photoanodes via Oxygen Vacancy-Rich β-Bi ₂ O ₃ Coating for Enhanced Charge Transfer and Water Oxidation Kinetics

Heterojunction engineering has been widely employed to enhance the charge transfer performance of bismuth vanadate (BiVO4) photoanodes; however, the simultaneous acceleration of water oxidation has remained unexplored. In this study, an O2 plasma treatment is applied to construct BiVO4/β-Bi2O3 (BVO/BO-P), aiming to concurrently improve charge transfer efficiency and promote water oxidation. The photocurrent density of BVO/BO-P at 1.23 V versus the reversible hydrogen electrode (RHE) exhibits a remarkable 150% increase compared to that of bare BiVO4. Moreover, the photocurrent onset potential of BVO/BO-P catholically shifts by 300 mV relative to bare BiVO4. In a BVO/BO-P photoanode, charge transfer performance is improved by the construction of BiVO4/β-Bi2O3 heterojunctions, while water oxidation is accelerated by overlayer β-Bi2O3 with numerous oxygen vacancies (OVs). This work provides a facile approach to constructing a BiVO4/β-Bi2O3 heterojunction for enhancing charge transfer and accelerating water oxidation.