Fabrication of TiO ₂/tin-doped indium oxide-based photoelectrode coated with overlayer materials and its photoelectrochemical behavior

The photoelectrochemical properties of TiO ₂-based photoelectrodes with metal oxide overlayers (e.g., ZnO, ZrO ₂, MgO, and Al ₂O ₃ were investigated. The metal oxides were deposited on TiO ₂/tindoped indium oxide (ITO) films by spin-coating metal-alkoxide precursors. The formation of the overlayers was confirmed by energy dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM). Each overlayers were well-coated on the TiO ₂-based films and have approximately 2 nm thickness. The prepared films were used as photoanodes in a photoelectrochemical system with a Pt counter electrode to evaluate hydrogen production performance. Comparing with other overlayers, the ZnO-coated photoelectrode exhibits the highest rate of hydrogen evolution and which is better than the uncoated one. From the photoelectrochemical and spectroscopic study, the superior hydrogen production property of the ZnO-coated TiO ₂ photoelectrode was attributed to both the higher light absorbance of ZnO compared to TiO ₂ and the formation of hydroxyl groups at the ZnO surface.