The enhanced charge transport at the Ba_xSr_1−xTiO₃/TiO₂ heterojunction interface improves the photoelectrochemical corrosion protection performance of stainless steel

Photoelectrochemical cathodic protection technology is an efficient and environmentally friendly strategy for metal corrosion protection. TiO₂ has been widely utilized due to its high chemical stability and appropriate band structure, yet its limited visible-light responsiveness and rapid recombination of photogenerated charge carriers hinder practical applications. The construction of heterojunctions enables the modulation of band structures to broaden the spectral response range and utilizes interfacial electric fields to facilitate charge separation, thereby significantly enhancing photoelectrochemical cathodic protection performance. In this study, Ba_xSr_1−xTiO₃/TiO₂ films were successfully prepared on FTO glass by two-step ultrasonic spray pyrolysis method, and the photoelectrochemical cathodic protection performance of Ba_xSr_1−xTiO₃/TiO₂ composite films was tested using 304 stainless steel (304 SS) as the protected metal. Subsequently, the BaTiO₃/TiO₂ composite film with the best performance was studied in depth. The results show that compared with TiO₂ films, the BaTiO₃/TiO₂ composite film has enhanced light absorption performance and improved photogenerated carrier separation efficiency. In 3.5wt% NaCl solution, the photocurrent density of BaTiO₃/TiO₂ composite films can reach 8.7 μA/cm², which is 4.14 times that of TiO₂, and the open-circuit potential is negatively shifted to −0.5 V, which is 390 mV and 250 mV lower than that of 304 SS self-corrosion potential and pure TiO₂ film, respectively. The improvement of its performance is mainly attributed to the combination of BaTiO₃ and TiO₂ to form a heterojunction, which promotes the separation of photogenerated carriers.