Photoelectrochemical Cathodic Protection Effect of Bi₂S₃/TiO₂ nanorod Array Composite Film for Stainless Steel

Abstract

TiO 2 nanomaterials have long been a topic of interest for applications in various fields due to their special photoelectrochemical properties. However, there are some problems for practical applications of a pure TiO 2 film. TiO 2 can only be excited by ultraviolet light and its photoelectric conversion efficiency is low due to the high electron-hole recombination rate. In order to overcome these problems, many methods have been developed to modify TiO 2 films for improving their photoelectrochemical properties. In this work, we fabricated a Bi 2 S 3 modified rutile TiO 2 nanorod array film on FTO conductive glass for achieving a good photoelectrochemical cathodic protection effect on 403 stainless steel (403SS) in a NaCl solution. A single crystalline rutile TiO 2 nanorod array film was prepared by a typical hydrothermal reaction method. A FTO substrate (10 mm × 15 mm × 2.2 mm) was immersed in a TiCl 4 solution and thermally treated in an electric oven at 70 ℃ for 30 min. After that, the FTO specimen was annealed at 550 ℃ in air for 1 h. Then the specimen with the TiO 2 seed layer was immersed a mixed aqueous solution of TiCl 4 and HCl, and heated in an electric oven at 150 ℃ for 10 h. Bi 2 S 3 nanoparticles was prepared on the TiO 2 film by a typical chemical bath deposition method. The TiO 2 film sample was alternately immersed in the Bi(NO 3 ) 3 ethylene glycol solution and the Na 2 S aqueous solution for 1 min. After each immersion, the film sample was dried at 80 ℃ for 5 min. This operation cycle was repeated for 15 times. Finally, the film sample was annealed at 240 ℃ for 4 h in a N 2 atmosphere. The prepared films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their photoelectrochemical properties and photocathodic protection effects were investigated. The results indicated that the prepared TiO 2 film was composed of the nanorod array. The TiO 2 in the film was highly crystallized and agreed well with the rutile phase, and Bi 2 S 3 nanoparticles were successfully deposited on the TiO 2 film. The photoresponse of the Bi 2 S 3 /TiO 2 composite film was extended into the visible light region, and its photoelectrochemical properties were enhanced. Under white light illumination, the Bi 2 S 3 /TiO 2 composite film as a photoanode could make the potential of 403SS in a 0.5 M NaCl solution decrease by 695 mV (relative to its corrosion potential), showing a more effective photoelectrochemical cathodic protection effect than the pure rutile TiO 2 nanorod film, which is of significance for environmentally friendly corrosion control of metals. This work was supported by the National Natural Science Foundation of China (Nos. 21573182, and 21173177).