Preparation of carbon-coated Magneli phases TinO2n−1 and their photocatalytic activity under visible light

Carbon-coated Magneli phases TinO2n−1 were prepared by a simple heat treatment of the powder mixture of rutile-type TiO2 with poly(vinyl alcohol) PVA at 1100 °C in inert atmosphere. The lower TiO2/PVA ratio in the mixture resulted in TinO2n−1 with the lower n-value. Carbon-coated TinO2n−1 phases thus prepared showed photocatalytic activity under visible light. The TinO2n−1 phases with n-vales of 2 and 3 had higher activity under visible light than those with n-values of more than 4. Carbon coated on the particles was found to reduce the matrix rutile-type TiO2 to Magneli phases TinO2n−1 during the heat treatment, in addition to suppress the sintering and grain growth of TinO2n−1 particles and to enhance the photocatalytic activity by increasing local concentration of the pollutant due to its adsorptivity.