Preparation of BaTiO₃/SrTiO₃ composite film and its photoelectrochemical cathodic protection performance

Improving the separation efficiency of photogenerated carriers is an effective way to improve the protection performance of photoelectrochemical cathode. In order to make up for the shortcomings of SrTiO₃, such as large band gap and low separation efficiency of photogenerated carriers, BaTiO₃/SrTiO₃ composite films were prepared on fluorine-doped tin oxide conductive glass (FTO) by two-step ultrasonic spray pyrolysis process. The phase composition, surface morphology and optical properties of the samples were observed by XRD, SEM, UV-vis DRS and PL. Then, 304 stainless steel (304 SS) was used as the protected metal, and the photoelectrochemical cathodic protection performance of BaTiO₃/SrTiO₃ composite film was observed under the condition of shading light. The relative position of BaTiO₃/SrTiO₃ is determined by Mott-Schottky curve. The results show that the light absorption range of BaTiO₃/SrTiO₃ composite films prepared by two-step ultrasonic spray pyrolysis process is broadened to 400 nm. Compared with SrTiO₃ film, BaTiO₃/SrTiO₃ composite film has better light absorption performance. The separation efficiency of photo-generated carriers is improved. In 3.5wt%NaCl solution, BaTiO₃/SrTiO₃ composite film negatively shifts the open circuit potential of 304 SS to −0.38 V, with a negative shift degree of about 230 mV, while pure SrTiO₃ film can only negatively shift by 100 mV. The performance improvement is mainly attributed to the heterojunction formed by BaTiO₃ and SrTiO₃, which promotes the separation of photogenerated carriers.