KIM Jung-Sik University of Seoul

Photocatalytic Degradation of Benzene Gas by the Hybrid Photocatalyst of Nanocrystalline TiO2/CaAl2O4:(Eu,Nd) Phosphor under Visible-light Irradiation

Co-authors SUNG Hyun-Je, KIM Byung-Min

The coupling of TiO2 with other inorganic oxides such as SiO2, SnO2, WO3, (Sr,La)TiO3+, and ZnFe2O4 can change the photocatalytic efficiency and the energy range of photo-excitation. This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on long-lasting phosphor of CaAl2O4:Eu2+,Nd3+. The CaAl2O4:Eu2+,Nd3+ phosphor powders were prepared via conventional sintering using CaCO3, Al2O3, Eu2O3, and Nd2O3 as raw materials according to the appropriate molar ratios. Nanocrystalline TiO2 was deposited on CaAl2O4:Eu2+,Nd3+ powders via low-pressure chemical vapor deposition (LPCVD). The TiO2 deposited on the long-lasting phosphor presented different decomposition behaviors with respect to the photo-degradation of benzene gas when compared to that of pure TiO2. The TiO2 coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO2, which is almost non-reactive. The coupling of TiO2 with phosphor may result in an energy band bending in the junction region, which then induces the TiO2 crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO3 that formed at the interface between TiO2 and the CaAl2O4:(Eu2+,Nd3+) phosphor may affect the photocatalytic reaction. In addition, the effect of Ag nanoparticle loading was investigated on the photocatalytic reactivity of the TiO2/CaAl2O4:Eu2+,Nd3+ phosphor. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. TiO2 on the Ag-doped phosphor presented a higher benzene gas decomposition rate than the TiO2 did on the phosphor without Ag-doping. The photocatalytic characteristics of TiO2/Ag-CaAl2O4:(Eu,Nd) hybrid photocatalyst will be discussed with crystalline structure, heterojunction of energy band structure and phosphorescence.