Improving carbon coated TiO2 films with a TiCl4 treatment for photocatalytic water purification

By using a simple thermal decomposition route, carbon-TiO2 hybrid films have been synthesized from a catechol-TiO2 surface complex. The coated films display enhanced visible region absorption, owing to the thin (approximate to 2nm) layer of carbon encapsulating the TiO2. Although photocatalytically active under visible light alone, it is demonstrated that the activity of the carbon-coated films can be improved further by a hydrolytic treatment with TiCl4, leading to the introduction of small TiO2 particles (5-10nm) and doping of chlorine into the structure. The combination of the carbon layer and TiCl4 treatment gives increased photocatalytic performance for the photodegradation of dyes, phenolic pollutants and the reduction of toxic Cr-VI to relatively benign Cr-III. In addition, the carbon-coated films show improved bactericidal activity under UV irradiation, and hence have been successfully tested against the most common types of pollutant present in potential drinking waters.