Effect of TiO2 supporting layer on Fe2O3 photoanode for efficient water splitting

For an electrochemical water splitting system, titanate nanotubular particles with a thickness of ∼700 nm produced by a hydrothermal process were repetitively coated on fluorine-doped tin oxide (FTO) glass via layer-by-layer self-assembly method. The obtained titanate/FTO films were dipped in aqueous Fe solution, followed by heat treatment for crystallization at 500 °C for 10 min in air. The UV–vis absorbance of the Fe-oxide/titanate/FTO film showed a red-shifted spectrum compared with the TiO2/FTO coated film; this red shift was achieved by the formation of thin hematite-Fe2O3 and anatase-TiO2 phases verified using X-ray diffraction and Raman results. The cyclic voltammetry results of the Fe2O3/TiO2/FTO films showed distinct reversible cycle characteristics with large oxidation–reduction peaks with low onset voltage of I–V characteristics under UV–vis light illumination. The prepared Fe2O3/TiO2/FTO film showed much higher photocurrent densities for more efficient water splitting under UV–vis light illumination than did the Fe2O3/FTO film. Its maximum photocurrent was almost 3.5 times higher than that obtained with Fe2O3/FTO film because of the easy electron collection in the current collector. The large current collection was due to the existence of a TiO2 base layer beneath the Fe2O3 layer.