Hematite Thin Film Photoanodes for Visible Light Water Photooxidation: Effects of Zn Doping and Hydrogen Treatment

The present work is devoted to the improvement of key hematite properties, in order to achieve an enhanced activity in photoelectrochemical (PEC) H2O splitting activated by visible light. To this regard, Fe2O3 thin films prepared by electrodeposition on fluorine-doped tin oxide (FTO) substrates were modified by Zn introduction and/or treatment in hydrogen-containing atmospheres under controlled conditions. In particular, the combined Zn doping and hydrogen treatment enabled the development of Zn/H:alpha-Fe2O3 photoanodes with significantly improved performances than the pristine alpha-Fe2O3 (photocurrent density: 1.13 vs. 0.36 mA/cm2 at 1.23 V/RHE under visible light illumination). Optical absorption, Mott-Schottky and electrochemical characterization revealed that the combined Zn introduction and hydrogen treatment produced various effects, including an increase in donor density and an enhanced optical absorption. As a result, a favorable performance improvement took place, paving the way to the eventual utilization of the target systems in PEC water splitting under real-world conditions.