Fe2O3 photoanodes: Photocorrosion protection by thin SnO2 and TiO2 films

[Display omitted] •Porous hematite layers covered by conformal ALD SnO2 and TiO2 overlayers.•The presence of the TiO2/SnO2 coatings was evidenced by XPS.•The Faradaic efficiency, f, of photocorrosion in acidic media determined.•f decreased by capping with either TiO2 or SnO2 2 nm thick overlayer.•2 nm thick SnO2 overlayer had positive influence on the long term photocurrent stability. The possibility of protection of Fe2O3 (hematite) against photocorrosion in aqueous electrolytes by thin layers of TiO2 and SnO2 deposited by ALD (atomic layer deposition), was investigated. Sn-doped hematite layers, as obtained in this study by aerosol pyrolysis had significant roughness and porosity. ALD is very successful in applying conformal films to such structures. The nominal coverage by ALD films was varied between 0.5 and 7.5 nm. The presence of the TiO2 and SnO2 films was evidenced by XPS. Photocurrents were strongly diminished as the capping layer thickness was increased. The Faradaic efficiency, f, of photocorrosion in acidic media (0.01 M H2SO4) was decreased from 0.026 to 0.014 and to 0.010 by capping with either a 2 nm thick overlayer of TiO2 or of SnO2, respectively. The latter had also a positive influence on the long term photocurrent stability.