MXene-modified BiVO4/FePO4 photoanodes for solar oxygen evolution.

Photoelectrochemical reactions in aqueous systems represent a promising route for solar fuel production; however, their efficiency is often constrained by the sluggish kinetics of the anodic oxygen evolution reaction (OER). BiVO4 is one of the most promising photoanode materials and has demonstrated the ability to efficiently convert light into electrical and then chemical energy. However, the conversion efficiency of pure BiVO4 remains insufficient. In this work, BiVO4 photoanodes are first modified with FePO4 using a simple Autodrop process and subsequently integrated with Ti3C2T x MXene overlayers deposited via automated spray coating. The thus modified photoanodes exhibit a superior performance thanks to the synergistic interaction between the FePO4 and MXene layers, which promotes the movement of electrons and efficient charge separation, thus suppressing surface recombination in BiVO4. Meanwhile, both the FePO4 and MXene layers can act as hole-transport channels and co-catalytic interfaces, facilitating interfacial charge transfer and accelerating OER kinetics. Importantly, achieving an optimal balance between MXene coverage and FePO4 exposure is critical to maximizing catalytic activity within the BiVO4/FePO4/MXene heterostructure. By optimizing the MXene loading, the modified BiVO4/FePO4 photoelectrode exhibits an approximately 50% improvement in photocurrent performance. Overall, this work presents a simple and effective strategy for fabricating high-performance photoanodes with potential for scalable production. The proposed heterojunction design provides a promising pathway toward the development of efficient and stable photoanodes for solar fuel applications.