Reversing Internal Electric Field Direction at BiVO4/TiO2 Heterostructure Interface by a Thin W‐VO2 Layer: Turning Waste Charge Carriers into Wealth

• Published in: Advanced sustainable systems (Online) Vol. 8; no. 7
• Main Authors: Seck, Astou, Mirzaei, Amir, Shayegan, Zahra, Ngom, Balla D, Ma, Dongling, Chaker, Mohamed
• Format: Journal Article
• Language: English
• Published: 01-07-2024
• Subjects: band edge engineering; internal electric field direction; photocatalysis; water splitting; water treatment
• ISSN: 2366-7486; 2366-7486
• DOI: 10.1002/adsu.202300496

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 BiVO4 alone, BiVO4/TiO2 results in ≈24% reduction in photocurrent density in this study. Herein, a tungsten‐doped VO2 (W‐VO2) thin film is inserted between BiVO4 and TiO2 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‐VO2 insertion, the photocurrent density is enhanced by ≈145% and ≈91% compared to BiVO4/TiO2 and BiVO4, respectively at 1.23 V versus RHE. Besides, under visible light irradiation, the kinetics rate constant for tetracycline removal by BiVO4/W‐VO2/TiO2 photocatalyst is 225% higher than that of BiVO4/TiO2, due to utilizing charge carriers before being recombined, without doping the BiVO4 and TiO2 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 VO2 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.
This study highlights the reversing of the internal electric field (IEF) at the BiVO4/TiO2 interface and modifying band edge alignment without bandgap narrowing and by inserting a thin‐film W‐VO2. A dramatic improvement in photocatalytic activity is obtained after reversing IEF, directing photo‐induced holes to the surface and electrons toward back contact, and reducing charge carriers' recombination rate at the interface.