Study of the photoelectrochemical cathodic protection mechanism for steel based on the SrTiO3-TiO2 composite

Up to now the mechanism of the photoelectrochemical (PEC) cathodic protection of the semiconductor materials is still unclear. In this work, the conduction band (CB) potential of the SrTiO3-TiO2 composite was regulated by controlling the deposition amount of SrTiO3 on the surface of TiO2 nanotube arrays. When the hydrothermal treating time was 1 h, the prepared SrTiO3-TiO2 photoanode (denoted as SrTiO3-TiO2-1) exhibited the most excellent PEC cathodic protection performance for 304 stainless steel and Q235 carbon steel in NaCl electrolyte. Further analysis indicates that the PEC cathodic protection performance of the photoanode is determined by the CB potential of the n-type semiconductor material, the separation efficiency of the photogenerated electron-hole pairs and the redox potential of the electrolyte. Among them, sufficient negative CB potential is the prerequisite for providing the PEC cathodic protection for the coupled metals. Under this premise, the higher the separation efficiency of the photogenerated electron-hole pairs and the more negative redox potential of the electrolyte are, a more negative potential of the coupled metal can be cathodically polarized to under the illumination of incident light with suitable wavelength. (C) 2017 Elsevier B.V. All rights reserved.