Characterization and photoelectrochemical performance of Zn-doped TiO2 films by sol-gel method

Zn-doped TiO2 (Zn-TiO2) thin films were prepared by the sol-gel method on titanium substrates with heat treatment at different temperatures. The effects of heat treatment temperatures and Zn doping on the structure, photocathodic protection and photoelectrochemical properties of TiO2 thin films were investigated. It is indicated that the photoelectrical performance of the Zn-TiO2 films is enhanced with the addition of Zn element compared with the pure-TiO2 film and the largest decline by 897 mV in the electrode potential is achieved under 300 °C heat treatment. SEM-EDS analyses show that Zn element is unevenly distributed in Zn-TiO2 films; XRD patterns reveal that the grain size of Zn-TiO2 is smaller than that of pure-TiO2; FTIR results indicate that Zn-O bond forms on Zn-TiO2 surface. Ultraviolet visible absorption spectra prove that Zn-TiO2 shifts to visible light region. Mott-Shottky curves show that the flat-band potential of Zn-TiO2 is more negative and charge carrier density is bigger than that of pure-TiO2, implying that under the synergy of the width of the space-charge layer, carrier density and flat-band potential, Zn-TiO2 with 300 °C heat treatment displays the best photocathodic protection performance.