Citric acid-driven interface engineering of BiVO4 photoanodes for enhanced photoelectrochemical performance

Abstract

BiVO₄, with its moderate band gap (∼2.4 eV) and visible light absorption properties, is considered a promising photoanode material. However, its photoelectrochemical performance is hindered by intrinsic defects such as poor charge carrier transport and rapid electron-hole recombination, resulting in a significant gap between its practical and theoretical photocurrent densities. In this work, we present a simple surface reconstruction method by adding citric acid to Na₂SO₄ electrolyte. Citric acid’s multidentate structure strongly chelates the metal-sites on the BiVO₄ surface, triggering lattice reconstruction through intense interactions. This surface modification not only prolongs hole lifetime but also acts as an interface modifier, leaving a carboxyl-rich, superhydrophilic interface on the BiVO₄ surface after the reaction (contact angle ≈ 0°). The multi-dimensional optimization synergistically improves BiVO₄’s photoelectrochemical performance, achieving an excellent photocurrent density of 6.8 mA·cm⁻² under AM 1.5G irradiation. Importantly, our findings reveal a three-pronged synergy achieved with inexpensive citric acid: structural reconfiguration, electronic tuning, and extreme wettability, which offered a streamlined route for solar fuel production without solid co-catalysts.