Ag/SnO2/TiO2 nanotube composite film used in photocathodic protection for stainless steel

Abstract A TiO2 nanotube film was fabricated on a Ti foil via anodization, SnO2 quantum dots were deposited on the film by hydrothermal treatment, and then Ag nanoparticles were formed on the SnO2/TiO2 film by pulse electrodeposition to obtain a Ag/SnO2 co-modified TiO2 composite photoanode with good photocathodic protection performance and charge storage ability. The properties of the composite film were investigated by surface analyses, UV–vis and fluorescence spectroscopies, and photoelectrochemical measurements. The results showed that the light absorption of the Ag/SnO2/TiO2 film was extended into the visible region compared with the TiO2 film. The photocurrent intensity of the composite film was two times as high as that of the TiO2 film. The composite photoanode under illumination by white light made the potential of the coupled 403 stainless steel (403SS) in a 0.5 M NaCl solution drop by 475 mV in contrast with its corrosion potential, showing an enhanced photocathodic protection effect. It is noteworthy that the 403SS potential was still 270 mV lower than the corrosion potential within 22.5 h after cutting off the illumination, demonstrating that the cathodic protection could be maintained through the charge storage ability of the composite photoanode.