3D ZnIn2S4 nanosheets/TiO2 nanotubes as photoanodes for photocathodic protection of Q235 CS with high efficiency under visible light

A 3-dimensional ZnIn2S4/TiO2 nanotubes composite was prepared by a combined hydrothermal reaction and electrochemical anodization method. Photogenerated open circuit potential, photogenerated current density, electrochemical impedance spectra, Tafel curves, and i-V curves were measured to investigate the photoelectrochemical activities and photocathodic protection properties for Q235 carbon steel. The results showed that the photocurrent density of the ZnIn2S4/TiO2 composite was greatly increased compared with pure TiO2. Under visible light irradiation, the photocurrent density of the ZnIn2S4-0.25/TiO2 composite can reach 400 mu A cm(-2), which was two times that of TiO2. The photogenerated potential drop of the composite photoanode was about 0.36 V, which was greater than that of TiO2 (about 0.16 V). The introduction of the ZnIn2S4 improved the visible light absorption ability and photogenerated charge separation efficiency of TiO2. The loading of ZnIn2S4 onto the TiO2 surface led to a negative shift of the Fermi level of TiO2. The generation of adsorbed oxygen can facilitate the separation of photogenerated charges. (C) 2018 Elsevier B.V. All rights reserved.