α-Fe2O3/TiO2 stratified photoanodes

Bilayer alpha-Fe2O3/TiO2 thin films were prepared with the aim of minimising photocorrosion of hematite. Conductive fluorine doped tin oxide (FTO)/glass was used as substrate for successive deposition of (i) alpha-Fe2O3 layers by high-power impulse magnetron sputtering (HIPIMS) and (ii) TiO2 (sol-gel method using dip-coating): The influence of annealing temperature (250-750 degrees C) and hematite layer thickness on the photoelectrochemical performance was evaluated. Hematite films on FTO substrates, calcined at 650 degrees C or 750 degrees C show increased photoelectrochemical response due to doping by Sn diffusion from the substrate. The photoresponse decreases with increasing thickness from 20 to 100 nm due to incomplete doping of the bulk. For bilayer hematite/TiO2 films, the visible light photoresponse is higher than that for the single hematite film which is ascribed to suppression of surface recombination at the Fe2O3/electrolyte junction by capping with TiO2. The Faradaic efficiency of the photocorrosion reaction was found to be 0.8% for an unprotected hematite electrode and decreased to 0.1% for a hematite electrode covered with a 65 nm thick layer of TiO2, thus proving the beneficial role of TiO2 in protecting hematite against photocorrosion. (C) 2018 Elsevier B.V. All rights reserved.