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

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, Fe2O3 (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 TiO2 to be grown prior to spray pyrolysis, limiting the subsequent thermal growth of rutile, so the overall TiO2 thickness was ca. 16 nm. 23 nm thick Fe2O3 deposited on a 22 nm TiO2 | Ti substrate after heat treatment at 500 °C for 1 hour was found to produced greater current densities than Fe2O3 deposited onto TEC-8 fluorine-doped tin oxide coated on glass; uv absorption by TiO2 and reflection by the titanium substrate contributed to measured photo-current densities.