Correlations among defect type, photoconductivity and photoreactivity of doped TiO2

The electrical conductivity (sigma), photoconductivity and photocatalytic r eactivity in doped crystalline TiO2 were measured as a function of the oxyg en partial pressure (Po-2), temperature, doping type and UV irradiation. Th e Po, dependence of sigma suggests that the predominant atomic defects in p ure TiO2 are oxygen vacancies (V-(o)double over dot) and interstitial titan ium ions (Ti-(i) triple over dot), but the dominant defect is changed with Po-2 and temperature. The photoexcited electrons in reduced and/or n-type d oped TiO2 enhance both the photoconductivity and the photocatalytic reactiv ity by the reduction process. Therefore, these behaviors are strongly depen dent on the electron concentration.