SUB-ESTIOQUIOMETRIC TITANIA LAYERS PREPARED BY MOCVD FOR PHOTOCATALYSIS APPLICATIONS

摘要

Many researchers have proved that semiconducting TiO_2 is an excellent photocatalist which permits the degradation and finally the mineralization of stable organic pollutants such as detergents,dyes and pesticides in water (1,2).However,it requires ultraviolet (UV) radiation whose energy exceeds the band gap of 3.2 eV (X-380 nm) of the anatase crystalline phase,hence practically ruling out the use of sunlight as an energy source for the photodegradation.Recently,theoretical calculations (3) have demonstrated that introducing oxygen vacancies in the anatase structure can induce the defect band to reach a width of 0.2 eV,and therefore to overlap with the conduction band.In this situation,the electrons in these defect states are able to hop and contribute to conduction thus enhancing photodegradation properties of the self-doped titania.These vacancy-induced band of electronic states facilitates the transport of the photocarriers to the active sites in the surface where the transfer to the target must take place for the degradation process.