Solvothermal-Etching Process Induced Ti-Doped Fe2O3 Thin Film with Low Turn-On Voltage for Water Splitting

In this work, a thinning process of hematite film accompanied by simultaneous titanium (Ti) doping has been demonstrated. Ti(4+) ion was incorporated into ultrathin Fe2O3 film by solvothermally etching a hematite film fabricated on titanium nanorod array substrate. As a consequence, the onset potential (Von) of oxygen evolution reaction for final ultrathin Ti-doped Fe2O3 film shifted toward cathodic substantially, a very low Von of 0.48 VRHE was realized, approximately 0.53 V cathodic shift of the hematite film. Working mechanisms were investigated from both kinetic and thermodynamic ways. The ultrathin Ti-doped Fe2O3 film exhibited reduced Tafel slope and higher generated photovoltage than the pristine Fe2O3 electrode. Moreover, the highly doped Fe2O3 resulted in significant reduction of charge-transfer resistance at the Fe2O3∥electrolyte interface. The drastic cathodic-shift Von is believed to be a result of combined factors including thermodynamic contribution, improved surface reaction kinetics, as well as facilitated charge transfer across bulk and interface.