Visible light active C-doped titanate nanotubes prepared via alkaline hydrothermal treatment of C-doped nanoparticulate TiO2: Photo-electrochemical and photocatalytic properties

Carbon-doped titanate nanotubes (C-TNT) were formed via alkaline hydrothermal treatment of a TiO2 nanoparticulate material pre-doped with carbon. Attempts to form C and W co-doped titanate nanotubes using analogous C and W co-doped nanoparticulate materials were unsuccessful. Physical characterisations, such as X-ray diffraction, N2 physisorption and Transmission Electron Microscopy, confirmed the formation of titanate nanotubes ~7 nm in diameter and hundreds of nm in length with increased surface areas relative to the nanoparticulate precursors. X-ray Photoelectron Spectroscopy confirmed the retention of substitutional carbon dopant and the exclusion of tungsten dopant from the doped TNT materials. Converting doped (or undoped TiO2) into C-TNT (or TNT) slightly increases the material’s bandgap but the C-TNT material (in contrast to TNT and undoped TiO2) absorbs into the visible region of the spectrum. C-doped and un-doped titanate nanotube materials were more active in promoting the photo degradation of 4-chlorophenol under visible light than their analogous nanoparticulate precursors. C-TNT was the most photocatalytically active material tested. However, photocurrent response measurements showed C-TNT to be less effective at generating current following irradiation than both its nanoparticulate analogue and nanoparticulate P25 when screen printed onto electrode surfaces. We ascribe this to non-optimal alignment of the TNTs on the electrode surface.