Synergy of compression and WO₃ treatment promotes charge transfer and enhances performance of BiVO₄ photoanodes

Particle powder assembly is a simple and scalable strategies for preparing photoelectrodes, but the photoelectrodes prepared by this method usually encounter the problem of poor charge transfer between particles. The photoelectrochemical performance of BiVO₄ photoanodes was significantly improved through mechanical pressing treatment and WO₃ surface modification. Firstly, monoclinic-phase BiVO₄ powder was prepared by the hydrothermal method, and deposited onto fluorine-doped tin oxide (FTO) substrates by drop-casting to form the photoanode. The electrical contact and connectivity between particles were enhanced by the tablet pressing process. Subsequently, WO₃ was deposited on the electrode surface to form a WO₃/BiVO₄ composite electrode, which effectively promoted the separation of photogenerated charges and provided an efficient electron transport channel. The results show that under AM 1.5G illumination (100 mW/cm²), the photoanode of BiVO₄ after mechanical pressing and WO₃ modification achieved a photocurrent density of 2.13 mA/cm² at a bias of 2.0 V versus reversible hydrogen electrode (RHE), which was approximately 7.8 times higher than that of the original sample of 2.08 mA/cm². The photocurrent densities obtained with either mechanical pressing alone or WO₃ modification alone were about 0.92 and 1.40 mA/cm², respectively, indicating a significant synergistic effect between the two treatments. The composite photoanode also exhibited higher charge separation efficiency, carrier density, and catalytic activity, and had good stability. This study provides a new optimization strategy for the design and preparation of high-performance BiVO₄-based photoanodes. This work provides a novel optimization strategy for designing and preparing high-performance BiVO₄-based photoanodes. By integrating mechanical pressing with chemical surface modification—where the former resolves the inherent interparticle discontinuities in powder-assembled electrodes and the latter optimizes charge separation and transport pathways from a band structure perspective—the combined approach achieves performance gains far exceeding those of individual treatments. The method avoids high-temperature sintering or vacuum coating, preventing grain growth and phase transformation, while being low-cost and easy to operate, making it suitable for large-scale fabrication. This strategy not only offers an effective enhancement route for BiVO₄-based photoanodes but also serves as a general reference for optimizing other particulate photoelectrodes such as WO₃ and TiO₂, holding significant promise for advancing the practical application of powder-assembled technologies in photoelectrochemical water splitting.