In Situ XAS Studies on the Structure of the Active Site of Supported Gold Catalysts

Gold clusters supported on Al2O3 and TiO2 have been exposed to different mixtures of CO and O2. Their structure has been probed in situ using X-ray absorption spectroscopy (XAS) at the Au L3-edge. In all materials, the dominant phase during catalysis is Au0. Both samples show variations of the electronic structure of the gold clusters with changing reaction conditions as evidenced by changes in the X-ray absorption near-edge (XANES) region. These variations are caused by interaction between the gold clusters and the carbon monoxide present in the gas phase. The gold atoms remain zerovalent throughout all experiments confirming the importance of Au0 for catalytic activity.