In Situ Formation of Oxygen Vacancies Achieving Near‐Complete Charge Separation in Planar BiVO4 Photoanodes

• DOI: 10.1002/adma.202001385
• Publication Date: 2020-05-14T08:14:05Z
• Authors: Songcan Wang; Tianwei He; Peng Chen; Aijun Du; Kostya (Ken) Ostr...; Wei Huang; Lianzhou Wang
• Keywords: bismuth vanadate; 2210 Mechanical Engineering; charge separation; Photoanodes; water splitting; 01 natural sciences; 7. Clean energy; oxygen vacancies; 2211 Mechanics of Materials; Engineering; photoanodes; Physical; Water splitting; Science & Technology; Multidisciplinary; 2500 Materials Science; Charge separation; 540; 0104 chemical sciences; Physical sciences; Chemistry; Oxygen vacancies; Chemical sciences; Bismuth vanadate

AbstractDespite a suitable bandgap of bismuth vanadate (BiVO4) for visible light absorption, most of the photogenerated holes in BiVO4 photoanodes are vanished before reaching the surfaces for oxygen evolution reaction due to the poor charge separation efficiency in the bulk. Herein, a new sulfur oxidation strategy is developed to prepare planar BiVO4 photoanodes with in situ formed oxygen vacancies, which increases the majority charge carrier density and photovoltage, leading to a record charge separation efficiency of 98.2% among the reported BiVO4 photoanodes. Upon loading NiFeOx as an oxygen evolution cocatalyst, a stable photocurrent density of 5.54 mA cm−2 is achieved at 1.23 V versus the reversible hydrogen electrode (RHE) under AM 1.5 G illumination. Remarkably, a dual‐photoanode configuration further enhances the photocurrent density up to 6.24 mA cm−2, achieving an excellent applied bias photon‐to‐current efficiency of 2.76%. This work demonstrates a simple thermal treatment approach to generate oxygen vacancies for the design of efficient planar photoanodes for solar hydrogen production.