Boosted Charge Transport Efficiency for Bismuth and Oxygen Dual Vacancy-Engineered BiVO4 Photoanodes

Abstract

Bismuth vanadate (BiVO₄) is a promising photoanode material that has been widely employed to address environmental pollution and the energy crisis. However, defect states substantially affect the efficiency of BiVO₄ photoanodes, and practical applications are severely limited because the fabrication of large-area photoanodes possessing excellent and uniform photoelectrochemical (PEC) activities remains challenging. Herein, bismuth and oxygen dual vacancy-engineered BiVO₄ photoanodes were fabricated by cosputtering BiVO₄ and V targets. The Bi/V atomic ratio of the BiVO₄ photoanode was tailored by tuning the sputtering power of the V target (P_V), thereby regulating both vacancy types in the BiVO₄ photoanode. The optimized BiVO₄ photoanode was fabricated at a P_V of 300 W and featured the highest bismuth vacancy (Bi_vac) concentration (12%) and oxygen vacancy (O_vac) concentration. Under solar spectrum air mass 1.5 irradiation, the current density of the optimized BiVO₄ photoanode was 1.9 mA/cm² (at 1.6 V_RHE (versus a reversible hydrogen electrode)), which was 11.9 times higher than that of the vacancy-free BiVO₄ photoanode (0.16 mA/cm²). Meanwhile, the optimized dual vacancy-engineered BiVO₄ photoanode exhibited the highest tetracycline hydrochloride degradation efficiency (79%) within 12 min, which was 2.9 times higher than that of the vacancy-free BiVO₄ photoanode (27%). The promoted PEC activity is ascribed to the high carrier concentration and efficient Bi_vac- and O_vac-derived charge transport. This work offers a strategy for fabricating highly efficient, large-area BiVO₄ photoanodes containing adjustable Bi_vac and O_vac concentrations.