Modulating built-in electric field via Bi-VO4-Fe interfacial bridges to enhance charge separation for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting on semiconductor electrodes is considered to be one of the important ways to produce clean and sustainable hydrogen fuel, which is a great help in solving energy and environmental problems. Bismuth vanadate (BiVO4) as a promising photoanode for photoelectrochemical water splitting still suffers from poor charge separation efficiency and photo-induced self-corrosion. Herein, we develop heterojunction-rich photoanodes composed of BiVO4 and iron vanadate (FeVO4), coated with nickel iron oxide (NiFeOx/FeVO4/BiVO4). The formation of the interface between BiVO4 and FeVO4 (Bi-VO4-Fe bridges) enhances the interfacial interaction, resulting in improved performance. Meanwhile, high-conductivity FeVO4 and NiFeOx oxygen evolution co-catalysts effectively enhance bulk electron/hole separation, interface water's kinetics and photostability. Concurrently, the optimized NiFeOx/FeVO4/BiVO4 possesses a remarkable photocurrent density of 5.59 mA/cm2 at 1.23 V versus reversible hydrogen electrode (vs RHE) under AM 1.5G (Air Mass 1.5 Global) simulated sunlight, accompanied by superior stability without any decreased of its photocurrent density after 14 h. This work not only reveals the crucial role of built-in electric field in BiVO4-based photoanode during PEC water splitting, but also provides a new guide to the design of efficient photoanode for PEC.