Photoelectrochemical water oxidation in α-Fe₂O₃ thin films enhanced by a controllable wet-chemical Ti-doping strategy and Co–Pi co-catalyst modification

The poor electrical conductivity, short hole diffusion length, and slow water oxidation reaction kinetics have severely limited the photoelectrochemical performance of the hematite (α-Fe₂O₃) photoanodes. In this paper, we report a facile wet-chemical approach to prepare the Ti-doping controllable hematite photoanode with subsequent Co–Pi electrocatalysts modification for solar water splitting. By optimizing the Ti-doping in Fe₂O₃, the Ti–Fe₂O₃ photoanodes can retain the primary morphology with the pristine Fe₂O₃ nanostructures, while simultaneously reducing the photogenerated charge carrier recombination rate in the films. Besides, by further decorating with Co–Pi co-catalysts on Ti–Fe₂O₃ surface, the formed Ti–Fe₂O₃/Co–Pi photoanode demonstrated an accelerated electrode/electrolyte kinetics during photoelectrochemical water oxidation reaction. As expected, the Ti–Fe₂O₃/Co–Pi photoanode produced an improved photocurrent density of 0.76 mA/cm² at 1.23 V vs RHE, which is much higher than the photocurrent density of individual Fe₂O₃ (0.25 mA/cm²) and Ti–Fe₂O₃ photoanode (0.51 mA/cm²). This work provides a good insight for designing the composite photoanode to simultaneously enhance the charge transport and surface water oxidation kinetics for efficient solar fuel production.