Arc-Synthesized FeTiO ₃ : when Interfacial Charge Transfer Kinetics Controls PEC Water Oxidation

High Resolution Image Download MS PowerPoint Slide Ilmenite FeTiO 3 (97% phase purity, indirect bandgap of 2.1 eV) was fast synthesized from arc melting α-Fe 2 O 3 and anatase-TiO 2 . Electrodes of FeTiO 3 (3.9 μm thick) deposited on FTO were evaluated for photoelectrochemical alkaline O 2 evolution reaction (OER); the current–potential profiles under irradiation confirmed the n-type behavior with a charge separation of 3.5% and transfer efficiencies of 90%, at +1.6 V vs RHE. At + 1.4 V vs RHE, the FTO|FeTiO 3 photoanode delivered a stable photocurrent that varied from 100 to 70 μA cm –2 over 5 h. Electrochemical impedance spectroscopy suggests that the charge transfer resistance at the semiconductor|electrolyte interface is a primary limiting factor. Intensity-modulated (photo)current/voltage spectroscopies revealed the apparent electron diffusion coefficient of 2.5·10 –4 cm 2 s –1; also, the charge transfer time increased from 17 to 147 ms, with increasing the working potential. Comparison of transfer and recombination times demonstrates that the FeTiO 3 is governed predominantly by interfacial charge recombination rather than by slow bulk electron transport.