Mechanism of hydroxyl radicals formation on the reduced rutile

Abstract

Preparation of TiO2 with Ti3+ defects was performed by heating of titania raw material under flow of an ammonia gas at the temperatures of 300–700 °C. Different types of surface defects have been formed in titania upon heat treatment process and they were analysed by EPR technique. Enhanced formation of hydroxyl radicals was observed under both UV and visible light irradiations, on TiO2 sample prepared at 700 °C, which contained inner Ti3+ centers and oxygen vacancies in rutile lattice sites. The most probably the presence of rutile defects increased formation of O2−• radicals, which then gave yield in H2O2 and further in hydroxyl radicals. The intra band gap was created in rutile due to the formation of inner Ti3+ centers, which enhanced its visible light activity.