Reactivity of Au nanoparticles supported over SiO2 and TiO2 studied by ambient pressure photoelectron spectroscopy

The influence of the metal cluster size and the support on the reactivity of gold-based catalysts has been Studied in the CO oxidation reaction. To overcome the structural complexity of the supported catalysts, gold nanoparticles synthesized from colloidal chemistry with precisely controlled size have been used. Those particles were supported over SiO2 and TiO2 and their catalytic activity measured in a flow reactor. The reaction rate was dependent on the particle size and on the support, suggesting two reaction pathways in the CO oxidation reaction. In parallel, ambient pressure photoelectron spectroscopy (APPS) has been performed under reaction conditions using bidimensional model catalysts prepared by supporting Au nanoparticles over planar polycrystalline SiO2 and TiO2 thin films. The nanoparticles were transferred from a water surface where they have been dispersed by means of the Langmuir-Blodgett (LB) technique. In this way, the catalytically active surface was characterized under real reaction conditions, revealing that during CO oxidation gold remains in the metallic state. (C) 2008 Elsevier B.V. All rights reserved.