Behaviour of Titanium-based Fe2O3 Photo-Anodes in Photo-Electrochemical Reactors for Water Splitting

Abstract The behaviour of titanium substrates was investigated as replacements for transparent fluorine-doped tin oxide-coated glass substrates, the low conductivity of which causes inhomogeneous spatial distributions of potential and current densities on scaling up photo-electrodes in photo-electrochemical reactors. Hence, Fe 2 O 3 (ca. 23 nm thick) was deposited by spray pyrolysis onto the titanium surface at 450 °C in air, causing growth of (less photo-active) rutile by thermal oxidation, the thickness being measured as ca. 20 nm by secondary ion mass spectrometry. Anodising titanium in aqueous phosphoric acid enabled ca. 12 nm anatase TiO 2 to be grown prior to spray pyrolysis, limiting the subsequent thermal growth of rutile, so the overall TiO 2 thickness was ca. 16 nm. 23 nm thick Fe 2 O 3 deposited on a 22 nm TiO 2 | Ti substrate after heat treatment at 500 °C for 1 hour was found to produced greater current densities than Fe 2 O 3 deposited onto TEC-8 fluorine-doped tin oxide coated on glass; uv absorption by TiO 2 and reflection by the titanium substrate contributed to measured photo-current densities.