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

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 (PV), thereby regulating both vacancy types in the BiVO4 photoanode. The optimized BiVO4 photoanode was fabricated at a PV of 300 W and featured the highest bismuth vacancy (Bivac) concentration (12%) and oxygen vacancy (Ovac) 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 VRHE (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 Bivac- and Ovac-derived charge transport. This work offers a strategy for fabricating highly efficient, large-area BiVO4 photoanodes containing adjustable Bivac and Ovac concentrations.