Preparation and photocathodic protection property of ZnIn2S4/RGO/TiO2 composites for Q235 carbon steel under visible light.

For improving the photocathodic protection performance of TiO2 photoanode, ZnIn2S4/reduced graphene oxide (RGO)/TiO2 nanotubes (NTs) composite was synthesized by electrochemical anodizing combined with hydrothermal method. The photoelectrochemical and photocathodic protection properties of the ZnIn2S4/RGO/TiO2 composite were investigated in detail. Compared with pure TiO2 NTs, the ZnIn2S4/RGO/TiO2 composite showed a significant improvement in photocathodic protection performances. The photogenerated open circuit potential drop of ZnIn2S4/RGO/TiO2 coupled with Q235 carbon steel in 3.5 wt% NaCl solution under visible light could reach 420 mV versus saturated calomel electrode, which was more than twice as much as that of pure TiO2. The photogenerated current density of ZnIn2S4/RGO/TiO2 could reach 5.6 mA cm-2, which was twice as much as that of pure TiO2. The appearance of the adsorbed oxygen (OA) enabled the ZnIn2S4/RGO/TiO2 to have better photo-carrier separation efficiency and better photogenerated cathodic protection than pure TiO2. The present work demonstrated ZnIn2S4/RGO/TiO2 could be a potential material for photoanodes because of its better visible-light response, higher electrical conductivity and smaller charge transfer resistance.