Preparation of PPy/TiO₂ core-shell nanorods film and its photocathodic protection for 304 stainless steel under visible light

In this study, polypyrrole (PPy)/TiO₂ core-shell nanorods (PTNRs) films were successfully synthesized through hydrothermal treatment and electrochemical polymerization method. The structure and optical properties of the as-prepared films were characterized. The results showed that the core-shell PTNRs film exhibits superior visible-light absorption ability. The composite films with different deposition conditions were systematically studied on the performance of the photocathodic protection (PCP). The photoelectrochemical performance of the samples are related to their structures which are strongly influenced by the deposition time of PPy layer. Meanwhile, compared with other reported as-prepared films, PTNRs film under visible light illumination could negatively shift the potential of the coupled 304 stainless steel (304SS) to -640 mV vs. Ag/AgCl, exhibiting more efficient PCP effect. More importantly, it can continuously provide protection for the steel in the darkness based on the electron pool effect of PPy. The possible PCP mechanism of PTNRs film was also discussed.