Highly efficient polypyrrole sensitized TiO2 nanotube films for photocathodic protection of Q235 carbon steel

•PPy/TNAs hybrid film is prepared by electrochemical method.•The effect of electropolymerisation time on the performance of film is compared.•PPy/TNAs show excellent photocathodic protection ability for Q235 carbon steel.•PPy plays a role in photosensitization, electron pool and hetero-junction formation.

Polypyrrole (PPy) sensitized TiO2 nanotube arrays (PPy/TNAs) are fabricated via anodic oxidation and electropolymerisation method. The crystallinity, morphology, optical property and photocathodic protection performance of PPy/TNAs composites can be readily controlled by varying the electropolymerisation time. PPy acts as a photosensitizer and a “pool” to gather photoexcited electrons, and an appropriate quantity of PPy contributes to the photosensitization, heterojunction formation and electron pool effect. The PPy/TNAs film acquired at 15 min exhibits excellent visible-light response and favourable photocathodic protection for the coupled Q235 carbon steel under white-light irradiation.