Ultrafine Ti⁴⁺ doped α-Fe₂O₃ nanorod array photoanodes with high charge separation efficiency for solar water splitting

Hematite (α-Fe₂O₃) is a promising photoanode material for solar water splitting due to its suitable band gap, earth-abundance, excellent stability and non-toxicity. However, a short hole diffusion length limits its performance. A nanorod array structure can shorten hole transfer distance to photoelectrode/electrolyte interface and decrease recombination of photo-generated carriers. However, average diameters of all previously reported nanorods are over 50 nm, thus being too thick for holes to transfer to the interface. It is still a big challenge to prepare a Fe₂O₃ nanorod array photoelectrode with finer diameter. In this study, we prepare an ultrafine α-Fe₂O₃ nanorod array film with average diameter about 25 nm by calcining γ-FeOOH for the first time. The ultrafine nanorod array photoanode indicates much higher carrier separation efficiency and performance than a conventional nanorod array film.