Au/TiO2 Flowerlike Core-shell Nano Particles: Synthesis and Application as Photocatalyst

Speaker:

Haiyan Song Post-doctor, Center for Materials Science and Nanotechnology and Department of Chemistry, University of Oslo

Co-Author(s):

Yeon-Tea Yu Chonbuk National University, Chonju 561-756, Korea Poul Norby University of Oslo, P. O. Box 1033, Blindern, N-0315 Oslo, Norway

Semiconductor-metal nano composites have been widely employed in photocatalysis, where as the metal, in contact with the semiconductor can store and shuttle photo-generated electrons from the semiconductor to an acceptor in a photocatalytic process, thus greatly enhances the overall photocatalytic efficiency. In most of the catalytic studies, noble metal nano particles were dispersed on an oxide surface, such a catalyst structure, though effective, result in exposing both to reactants and the surrounding medium. Corrosion or dissolution of the noble metal particles during the operation of a photocatalytic reaction is likely to limit the use of noble metal such as Ag and Au. And the UV irradiation and photochemical reaction may cause obvious metal aggregation, the density and size of noble metal particles will be changed, which is unfavorable to the photocatalytic reaction. Thus, a better synthesis design is highly necessary for improving the catalytic performance of oxide-metal composite. In the present work, flowerlike Au/TiO2 core-shell nano particles were prepared by hydrothermal synthesis process and characterized by XRD, XPS, TEM, FE-SEM and BET measurement. The Au-core size and the TiO2-shell thickness can be controlled by using different concentration of HAuCl4 and TiF4, respectively. The photocatalytic activities of as-prepared Au/TiO2 were investigated through the degradation of acetaldehyde at room temperature under visible right irradiation, and the effluent gas was analyzed using a gas chromatograph with two flame ionization detectors. The acetaldehyde can be oxidized completely to produce CO2 and H2O on the Au/TiO2 surface under visible irradiation. The Au/TiO2 core-shell nano particles showed much better activity compared with nano TiO2 particles not only due to the changed Fermi level energy by the Au nano particles but also the large amount of •OH radical adsorbed on the surface of Au/TiO2. The higher photocatalytic activity was obtained in the composite catalyst with smaller Au-core particles.