Preparation of SnIn4S8/TiO2 Nanotube Photoanode and Its Photocathodic Protection for Q235 Carbon Steel Under Visible Light.

TiO2 is an attractive semiconductor suitable for photocathodic protection, but its weak absorption of visible light and low quantum yield limit its usage. Here, a new heterostructured SnIn4S8 nanosheet/TiO2 nanotube photoanode was prepared and its photocathodic protection performance was analyzed. SnIn4S8 nanosheets were uniformly deposited on the surface of the TiO2 nanotube via a solvothermal treatment. The SnIn4S8/TiO2 composite exhibited better photocathodic protection performance compared with pure TiO2 nanotubes, owing to its good visible-light response and photogenerated carrier separation efficiency. Moreover, the composite exhibited a maximum photocurrent density of 100 μA cm-2 for a 6 h solvothermal reaction under visible light irradiation. The negative shift of the photoinduced potential of Q235 carbon steel connected to the composite could reach 0.45 V versus SCE. Therefore, the SnIn4S8/TiO2 composite can offer efficient photocathodic protection for Q235 carbon steel against corrosion in 3.5 wt% NaCl solution. This work provides a new approach for the development of high-efficient photoanode materials for the photocathodic protection of metals.