In-situ and synchronous generation of oxygen vacancies and FeOx OECs on BiVO4 for ultrafast electron transfer and excellent photoelectrochemical performance

Abstract Efficient separation and transport of charge is a critical issue in solar-driven water oxidation. Herein, we developed a novel, facile, controllable method based on zero-valent iron (ZVI) reduction to in-situ and synchronous generate oxygen vacancies (Ov) and FeOx oxygen evolution co-catalysts (OECs) on BiVO4 for ultrafast electron transfer and excellent photoelectrochemical (PEC) water oxidation. In this method, a moderate and controllable ZVI reduction was the critical step to ensure whole penetration of Ov from BiVO4 to FeOx layer. This is because a special galvanic cell is formed between ZVI and BiVO4, making it easy to capture oxygen atom from BiVO4 and obtain a FeOx layer (5 nm) outside simultaneously in oxygen-free annealing. The Ov can extend light absorption by narrowing bandgap and significantly improve electron mobility (8.6 × 10−7 cm2 s−1) by reducing the trap-assisted recombination, which is 6.1-fold of BiVO4. Meanwhile, electron lifetime increases from 11.6 to 115.3 ms. Ultrathin FeOx layer provides more sites and dramatically reduces OER over-potential of 210 mV, resulting in fast hole-to-oxygen kinetics. A photocurrent of 3.13 mA·cm−2 at 1.23 VRHE is achieved for PEC water oxidation, which is 4.6-fold of pristine BiVO4. This work provides a new path to overcome charge transport limitations and achieve enhanced solar water oxidation.