Investigation on the electron transfer between anatase and rutile in nano-sized TiO2 by means of surface photovoltage technique and its effects on the photocatalytic activity

Photoinduced electron transfer between anatase and rutile in nanosized TiO2, prepared by a sol-gel method, was revealed by means of the surface photovoltage technique, and its effects on the photocatalytic performance in the degradation of a phenol solution were investigated. Also, the role of the surface states during the processes of photo-physics and photochemical reactions was discussed. In the as-prepared TiO2 sample consisting of anatase and rutile, the photoinduced electrons can easily transfer from anatase surface states to rutile, as well as from anatase conduction band to rutile. These factors are responsible for the strong surface photovoltage response and high photocatalytic activity. Moreover, the surface states related to oxygen vacancies can induce photocatalytic reactions under visible irradiation, especially in the resulting biphase TiO2, due to the electron transfer from anatase surface states to rutile.