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

For improving the photocathodic protection performance of TiO photoanode, ZnInS/reduced graphene oxide (RGO)/TiO nanotubes (NTs) composite was synthesized by electrochemical anodizing combined with hydrothermal method. The photoelectrochemical and photocathodic protection properties of the ZnInS/RGO/TiO composite were investigated in detail. Compared with pure TiO NTs, the ZnInS/RGO/TiO composite showed a significant improvement in photocathodic protection performances. The photogenerated open circuit potential drop of ZnInS/RGO/TiO 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 TiO. The photogenerated current density of ZnInS/RGO/TiO could reach 5.6 mA cm, which was twice as much as that of pure TiO. The appearance of the adsorbed oxygen (O) enabled the ZnInS/RGO/TiO to have better photo-carrier separation efficiency and better photogenerated cathodic protection than pure TiO. The present work demonstrated ZnInS/RGO/TiO could be a potential material for photoanodes because of its better visible-light response, higher electrical conductivity and smaller charge transfer resistance.