Herrmann-Geppert, I.; Bogdanoff, P.; Fengler, S.; Dittrich, T.; Fiechter, S.: Photoelectrooxidation of Water on Hematite Thin Films. ECS Transactions 45 (2013), p. 137-147

α-Fe2O3 (hematite) photoanodes for the oxygen evolution reaction (OER) were prepared by a cost-efficient sol-gel procedure. We show that annealing and plasma post-treatments improve significantly the photoelectrochemical properties for the OER. Annealing steps lead to a reorganization of the crystal structure and thereby to a pronounced shift of the photocurrent to negative potentials. Surface photovoltage measurements (SPV) indicate an enhanced separation of charge carriers originated from the band gap photoabsorption. Nevertheless a more pronounced effect on the catalytic efficiency was gained by a surface-treatment in oxygen plasma. X-ray photoelectron spectroscopy (XPS) analysis reveals an oxygen enriched surface layer with new oxygen species which might be responsible for the improved electrochemical activity. SPV measurements identify an increased fraction of transferred charge carriers from this newly produced surface defects. The combination of these post-treatments leads finally to an efficient hematite photoanode for the OER.