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.