A facile spray pyrolysis method to prepare Ti-doped ZnFe2O4 for boosting photoelectrochemical water splitting

Abstract

Although spinel zinc ferrite (ZnFe₂O₄), with a band gap of 1.9 eV, is a promising photoanode material for solar water splitting, its photoelectrochemical performance is usually hindered by poor charge carrier transport. Ti⁴⁺ doping was introduced to increase the charge carrier concentration and promote charge carrier transport in the ZnFe₂O₄ photoanode. Here, pure and Ti⁴⁺-doped ZnFe₂O₄ photoanodes were prepared by a fast and effective spray pyrolysis method. In the Ti-doped ZnFe₂O₄ photoanode, some of the Fe³⁺ sites in the crystal lattice are substituted by Ti⁴⁺, as shown by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometry (FTIR) analyses. The results of Mott–Schottky analysis and electrochemical impedance spectroscopy (EIS) indicated that the substitution of Fe³⁺ by Ti⁴⁺ enhances the charge carrier concentration and electron transfer efficiency. The Ti-doped ZnFe₂O₄ photoanodes exhibit a solar water-splitting photocurrent of 0.35 mA cm⁻² at 1.23 V vs. RHE (reversible hydrogen electrode), which is 8.75 times higher than that of the pure ZnFe₂O₄ photoanodes. Hence, this study may provide a simple route to fabricate multi-metal oxide photoelectrodes through ion doping to enhance their photoelectrochemical performances.