Preparation of SrTiO₃/TiO₂ composite film for photoelectrochemical cathodic protection

Due to the presence of large band gap TiO₂, photogenerated carriers disadvantage low rate of separation, which limits the photoelectrochemical cathodic protection. To solve this problem, TiO₂ nanoarrays were prepared by hydrothermal method, and then SrTiO₃/TiO₂ composite films were prepared by ultrasonic spray pyrolysis. XRD, SEM, UV-visible diffuse reflectance spectrum (UV-Vis DRS), fluorescence spectra (PL) were used to characterize the phase structure, microscopic morphology, and light absorption properties of the samples. Finally, using 304 stainless steel (304 SS) as the protected substrate, the photoelectrochemical cathodic protection performance of the SrTiO₃/TiO₂ composite film was investigated. The results show that the SrTiO₃/TiO₂ composite film prepared by the ultrasonic spray pyrolysis method has a light absorption range of light below 415 nm, which enters the visible light region. The SrTiO₃/TiO₂ composite film has better light absorption than the TiO₂ nanoarray. The separation rate of photogenerated electron-hole pairs is increased, and the mobility of photogenerated electrons is improved. In 3.5wt%NaCl solution, the SrTiO₃/TiO₂ composite film makes the corrosion potential of 304 stainless steel negatively shift to −0.45 V, and the negative shift is nearly 270 mV. While the TiO₂ nanoarray can only move 210 mV negatively, and the performance is improved by 28.5%. The performance of the SrTiO₃/TiO₂ composite film is stable after four open and closed light cycle tests.