Reversing Internal Electric Field Direction at BiVO 4 /TiO 2 Heterostructure Interface by a Thin W‐VO 2 Layer: Turning Waste Charge Carriers into Wealth

Abstract In heterojunction photocatalysts, the band edge alignment and internal electric field (IEF) direction significantly affect the charge carrier separation, thus the photoconversion efficiency. For example, because of an unfavorable band alignment and compared to BiVO 4 alone, BiVO 4 /TiO 2 results in ≈24% reduction in photocurrent density in this study. Herein, a tungsten‐doped VO 2 (W‐VO 2 ) thin film is inserted between BiVO 4 and TiO 2 to modify unfavorable spike‐like conduction band offset and IEF direction in ternary heterojunction. After reversing the IEF direction and engineering the band edges through W‐VO 2 insertion, the photocurrent density is enhanced by ≈145% and ≈91% compared to BiVO 4 /TiO 2 and BiVO 4 , respectively at 1.23 V versus RHE. Besides, under visible light irradiation, the kinetics rate constant for tetracycline removal by BiVO 4 /W‐VO 2 /TiO 2 photocatalyst is 225% higher than that of BiVO 4 /TiO 2 , due to utilizing charge carriers before being recombined, without doping the BiVO 4 and TiO 2 structures. Lastly, LC‐HR‐MS/MS analysis followed by the Toxicity Estimation Software Tool (T.E.S.T.) reveals the high importance of the band alignment on the detoxification of the solution. The tunability of the VO 2 work function with a low bandgap, yet distinctive valence and conduction bands (which distinguished it from metals) opens new avenues for designing high‐performance heterojunction‐based devices.