Doping of Nonmetal Se in Fe₂O₃ Nanowire Array-Based Photoanodes for Water Oxidation

Achieving ideal photoelectrochemical (PEC) water splitting efficiency for renewable chemical fuel generation is a highly preferable but a challenging target. To do so, much effort needs to be taken to investigate photoelectrodes. In this study, we report the amelioration of hematite (α-Fe2O3), which is a well-known semiconducting oxide suitable for PEC water oxidation. The Se-doped α-Fe2O3 nanowire array thin film on the fluorine-doped tin oxide substrate was synthesized by a facile one-step hydrothermal process followed by in situ two-step annealing at 823 and 1073 K. A photocurrent of 0.85 mA cm–2 at 1.23 V versus RHE was achieved for the Se-doped α-Fe2O3 photoanode, which was more augmented than the undoped α-Fe2O3 photoanode (0.33 mA cm–2). The Mott–Schottky plot revealed that the carrier concentration of α-Fe2O3 was strongly increased through Se doping. Photovoltage and electrochemical impedance spectroscopy indicated that Se-doped α-Fe2O3 exhibited a stronger driving force and reduced charge transport resistance, which were crucial aspects for higher photocurrent. Our work highlights the importance of the nonmetal element dopant to improve the PEC performance of α-Fe2O3 via convenient preparation.