Photocathodic Protection of 304 Stainless Steel by BiS/TiO Nanotube Films Under Visible Light.

We report the preparation of TiO nanotubes coupled with a narrow bandgap semiconductor, i.e., BiS, to improve the photocathodic protection property of TiO for metals under visible light. BiS/TiO nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of BiS deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO and orthorhombic BiS and exhibited a high visible light response. The photocurrent density of BiS/TiO was significantly higher than that of pure TiO under visible light. The sensitization of BiS enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO. The BiS/TiO nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.