Visible-induced photocatalytic reactivity of polymer–sensitized titania nanotube films

In this study, polythiophene–TiO2 nanotube films (PTh/TNT) were successfully prepared by a two-step electrochemical process of anodization and electropolymerization, in which a highly ordered TiO2 nanotube (TNT) film was anodized at a low-voltage with post calcination first and then the prepared TNT film was deposited with a polythiophene layer by electropolymerization in the BFEE electrolyte. The morphology and structures of PTh/TNT composites were examined by FESEM, EDX, XRD and XPS methods. XPS spectra of PTh/TNT composites indicate the strong interaction between S sites of polymer backbone and TiO2 nanotubes, in which electron transfer from polythiophene to titania takes place. UV–vis DRS analysis shows that these composites have a strong photoresponse in the visible region at 500 nm. The prepared PTh/TNT films revealed significant activity for 2,3-dichlorophenols (2,3-DCP) degradation under visible light irradiation and also sunlight irradiation, in which the PTh3/TNT film achieved the best performance. On the other hand, this study also confirmed that the side-chains of polythiophene could influence its photocatalytic activity significantly in an order from high to low as poly3-methylthiophene ≈ polythiophene > polythiophenecarboxylic acid > poly3-hexylthiophene. The results may provide useful information to further develop some effective polymer-semiconductor catalysts for pollutant degradation under sunlight irradiation for water and wastewater treatment.