Polythiophene-sensitized TiO2 nanotube arrays for photo-generated cathodic protection of 304 stainless steel

TiO2 nanotube arrays (TNAs) with highly ordered three-dimensional structure are a promising alternative in photo-generated cathodic protection. Organic semiconductor polythiophene (Pth)-sensitized TNAs nanocomposite was synthesized by a two-step anodic oxidation and electrochemical anodic polymerization methods in this work. The crystalline phase, morphology, optical property and photoelectrochemical performance of Pth/TNAs samples with different polymerization times were investigated. Light absorption of Pth/TNAs samples improves with appropriate Pth deposition that increases the density of photo-generated charge carriers. Meanwhile, Pth deposition induces improvement in the inner electric field that drives electron transfer from semiconductor to the connected metal. Increased carrier separation and heterojunction barrier effects in Pth/TNAs/Ti/304 SS multiple interfaces enhances the photoelectrochemical performance of the photoanode that leads to excellent protection effect of 304 stainless steel with irradiation. Moreover, electrons reflux from metal corrosion will be retarded for the unidirectional continuity of electrons in heterojunction barriers without irradiation, which shows application potentials in photo-generated cathodic protection in dark.