Effect of SiO2-doping on photogenerated cathodic protection of nano-TiO2 films on 304 stainless steel

In this study, SiO2-TiO2 composite films were prepared on 304 stainless steel (SS) by a sol-gel method and dipcoating technology. The impact of doping SiO2 on the microstructure and photoelectrochemical performance of the films was investigated. The results demonstrated that pure TiO2 film was composed of anatase and rutile. Doping the film with SiO2 suppressed the phase transformation of anatase to rutile and decreased particle sizes of the films. SiO2 also reduced fluorescence intensity of the composite films, inhibiting the recombination of electrons and holes. Optical absorption intensity of the films first increased and then decreased with increasing SiO2. The corrosion potential of the coated 304SS in 3.5% NaCl in the dark increased along with SiO2 content. Under illumination, however, the 304SS with 10% SiO2-TiO2 film behaved the lowest corrosion potential and smallest charge transfer resistance. Further SiO2 addition caused an amorphous film and suppressed light absorption, resulting in decreased photoelectrochemical performance.