Design and Construction of the Fe₂O₃/BiVO₄ Heterostructure-Based Photoanode for Photo-Electrochemical Desalination

Solar-assisted electrochemical desalination is a novel technique for sustainable development. In this study, a high energy efficiency photodriven electrochemical desalination method was proposed. The entire desalination process is driven by the Fe2O3/BiVO4 photoanode. The Fe2O3/BiVO4 material has a uniform distribution with the original coral-like morphology, which enhances its light energy utilization and reduces the photocorrosion of BiVO4. In the current photoelectrochemical desalination device, at a saltwater concentration of 1350 ppm, an initial photocurrent of 1.92 mA/cm2 and a salt removal rate of 44.62 μg/(cm2·min) were achieved with a zero-bias voltage applied in Fe2O3/BiVO4 compared with 20.40 μg/(cm2·min) in pure BiVO4. Also, at the saltwater concentration of 3500 ppm, the salt removal rate of Fe2O3/BiVO4 reached 65.29 μg/(cm2·min). The solar desalination capacities of the obtained photoanodes were 0.127 μmol/J at 1350 ppm and 0.133 μmol/J at 3500 ppm. Further research was conducted on the photoanode–electrolyte interface and charge separation and transportation using electron paramagnetic resonance and Mott–Schottky analysis. The exceptional desalination performance can be credited to the type II heterostructure effect of the Fe2O3/BiVO4 photoanode, which is applied in solar-driven desalination. This study has a significant importance in the design of high energy efficiency heterojunction photocatalysts for saltwater desalination.