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

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 (~2 nm) layer of carbon encapsulating the TiO₂. While 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.