Dual Functions of Optimized FeCo Oxyhydroxide Composition in BiVO4 Photoanodes with Bi Vacancy for Photocorrosion Inhibition and Improved Photoelectrochemical Performance

Excessive hole-accumulation-induced photocorrosion is considered a key factor that limits the activity of the photoelectrochemical water splitting reaction. In this study, a heterogeneous catalyst was prepared by a simple impregnation method, i.e., modification of different ratios of heterometallic oxyhydroxides (Fe x Co 1– x OOH) on in situ photoreduction-treated BiVO 4 (Bi-BVO). This work demonstrates for the first time that adjusting the FeCo ratio can greatly enhance the separation, transport, and directional control of electron–hole pairs, thus inhibiting photocorrosion. The Bi-BVO/Fe 0.7 Co 0.3 OOH composite exhibited a photocurrent density of 0.243 mA cm –2 at 1.23 V RHE (4.5 times that of pure BiVO 4 under 1.5 G AM illumination) in a sacrificial agent-free Na 2 SO 4 electrolyte. After 20 h of continuous illumination, the photocurrent density of the optimized samples showed negligible attenuation (7.2%). The strong stability under light conditions can be attributed to Fe and Co acting as hole shuttling mediators, which efficiently match the hole generation rate of Bi-BVO and enhance hole transport to the surface active sites. Furthermore, formation of Co–O–V bonds and passivation of surface states, which immobilize V 5+ in the lattice, further inhibit photocorrosion. This bimetallic oxyhydroxide modification strategy provides valuable insights into mitigating photocorrosion and offers an optimization approach for photoelectrochemical water splitting.