Super-hydrophilic BiVO4/MgO/FeCo2O4 charge migration achieves efficient photoelectrochemical performance

To address the issue of inefficient charge transfer efficiency at the semiconductor/cocatalyst interface, we engineered a BiVO4/MgO/FeCo2O4 array, incorporating an MgO interlayer. This design aimed to enhance the performance of photoelectrochemical (PEC) water splitting on BiVO4 and FeCo2O4. The introduced interlayer efficiently hinders hole backflow, promoting unimpeded charge migration within the multi-hybrid structure. This, in turn, significantly reduces recombination of electron-hole pairs. In addition, the BiVO4/MgO/FeCo2O4 undergoes a low-temperature plasma treatment, resulting in super-hydrophilicity. This treatment enhances charge migration efficiency and foster extensive contact between the electrolyte and electrode interfaces. Photoelectrochemical analysis demonstrates that H-BiVO4/MgO/FeCo2O4 exhibits exceptional performance for the oxygen evolution reaction (OER), showcasing a photocurrent density of 4.3 mA·cm−2 at 1.23 V vs. RHE in 0.5 M Na2SO4 under AM 1.5 G (100 mW·cm−2) illumination. Remarkably, this value is 5.2 times higher than that observed for BiVO4. Furthermore, the maximum incident photon to current conversion efficiency (IPCE) reaches an impressive 61.7 %, surpassing that of BiVO4 and BiVO4/FeCo2O4 by approximately 5.1 and 1.7 times, respectively. Additionally, the charge separation efficiency of H-BiVO4/MgO/FeCo2O4 achieves a notable 83.4 %, and the charge injection efficiency is substantially improved. This study advocates for a straightforward yet highly effective approach to mitigate interfacial electron-hole recombination.