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Abstract In this study, Nb‐doped α‐Fe 2 O 3 nanorod photoanodes were prepared via a facile solution‐based process by directly adding NbCl 5 in the aqueous solution. The morphology and electronic structure of Nb‐doped α‐Fe 2 O 3 films depended strongly on the dopant concentrations. Compared with the undoped sample, the optimal Nb‐doped α‐Fe 2 O 3 film showed an approximately 4‐fold photocurrent increase under solar light at 1.0 V versus Ag/AgCl, and the incident photon‐to‐current conversion efficiency was increased by 2.5 times, reaching 13.7 % at 350 nm and 1.23 V versus RHE. The enhancement in PEC activity, as induced by moderate Nb doping, was attributed to the increased charge carrier density for promoted charge transfer ability as well as the smaller nanorod diameter for shortened charge transfer distance. However, superfluous Nb dopants would destroy the nanorod structure and greatly reduce the thickness of α‐Fe 2 O 3 films, leading to poor optical absorption and thus decreased photoelectrochemical performance.
Fu et al. (Sun,) studied this question.