Influence of crystallinity and carbon content on visible light photocatalysis of carbon doped titania thin films

Visible light responsive carbon doped TiO2 films were developed by ion-assisted electron-beam evaporation using rutile powder as source material and two different gases, CO2 and CO in the ion source as dopant source. The influence of beam current on the carbon content and crystallinity of the films was systematically studied to understand their effect on photocatalytic activity. More carbon content was incorporated when ion beam current was raised and when CO2 gas was utilized as the ion source and it also resulted in shifting the absorbance edge of TiO2 towards higher wavelength region. The TiOxCy film of well-crystallized anatase phase with 1.25 at.% carbon dopant from CO2 source exhibited the lowest contact-angle close to zero and the best photocatalytic activity in terms of the reduction of silver ions to metallic silver and the degradation of methylene-blue under visible-light illumination. Post annealing the films at a higher temperature (500 degrees C) also improved the overall photocatalytic activities. This work demonstrates clearly that the photocatalytic performance of the TiOxCy films under visible light correlates well with the anatase crystallinity and carbon dopant concentration. (c) 2007 Elsevier B.V. All rights reserved.