Sustained Water Oxidation with Surface- and Interface-Engineered WO₃/BiVO₄ Heterojunction Photoanodes

Photoelectrochemical water splitting is a promising way of producing green hydrogen from water by utilizing solar energy and a suitable semiconductor material. However, most of the semiconductor materials suffer from severe photocorrosion. To overcome this issue, we demonstrate that a stable and efficient photoanode can be achieved in a surface- and interface-engineered WO₃/BiVO₄ heterojunction photoanode with a conformal TiO₂ protective layer and FeOOHNiOOH cocatalyst layer. Herein, a WO₃/BiVO₄ heterojunction photoanode was first fabricated by a combination of hydrothermal and solution drop-casting methods. A surface and interface of the photoanode was strategically engineered using an ultrathin TiO₂ protective layer by atomic layer deposition and a subsequent FeOOHNiOOH cocatalyst layer by photoelectrochemical deposition to achieve a record photocurrent density up to 4.6 mA/cm² at 1.23 V vs RHE with long-term photostability under simulated AM 1.5G light exposure. Therefore, this work provides an avenue for the fabrication of efficient photoanodes for photoelectrochemical water splitting.