Carbon modified TiO 2 photocatalysts for water purification

Abstract

Carbon can form different structures with TiO 2 : carbon-doped TiO 2, carbon coated TiO 2 and composites of TiO 2 and carbon. The presence of carbon layer on the surface of TiO 2 as well as the presence of porous carbon in the composites with TiO 2 can increase the concentration of organic pollutants on the surface of TiO 2, facilitating the contact of the reactive species with the organic molecules. Carbon-doped TiO 2 can extend the absorption of the light to the visible region by the narrowing of the band gap and makes the photocatalysts active under visible light irradiation. TiO 2 loaded carbon can also work as a photocatalyst, on which the molecules are adsorbed in the pores of carbon and then they undergo the photocatalytic decomposition with UV irradiation. Enhanced photocatalytic activity for the destruction of some organic compounds in water was noticed on the carbon coated TiO 2 and TiO 2 loaded activated carbon, mostly because of the adsorptive role of carbon. However, in carbon-doped TiO 2, the role of carbon is somewhat different, the replacement of carbon atom with Ti or oxygen and formation of oxygen vacancies are responsible for extending its photocatalytic activity towards the visible range.