CuInS2/TiO2 heterojunction with elevated photo-electrochemical performance for cathodic protection

Semiconductor quantum dots with high quantum yield and photovoltaic conversion efficiency have ushered in a brilliant moment for constructing internal electric field heterojunctions for photogenerated cathodic protection applications. In this paper, TiO2 nanotubes grown vertically on the surface of titanium substrates were modified via a combination of conventional electrochemical oxidation and a one-step solvothermal pathway to sensitize with CuInS2 quantum dots. Compared with pure TiO2 photoelectrodes, the modification improves sunlight absorption efficiency and provides photoelectron cathodic protection to the 304 stainless steel (304 SS). Through 9 h solvothermal reaction, the CuInS2/TiO2 coupled with protected 304 SS exhibited an excellent property when the simulated sunlight irradiation. Its mixed open circuit potential is negatively shifted to -0.99 V, at the mean time with a stable photocurrent density (118 μA cm−2). The results indicate that CuInS2 and TiO2 established a p-n heterojunction with well-matched energy level, which can effectively facilitate the carrier separation and retain the strong redox capbility of photo-induced electrons and holes.