In situ time-resolved characterization of Au-CeO2 and AuOx-CeO2 catalysts during the water-gas shift reaction:: Presence of Au and O vacancies in the active phase -: art. no. 221101

Synchrotron-based in situ time-resolved x-ray diffraction and x-ray absorption spectroscopies were used to study the behavior of nanostructured {Au+AuOx}-CeO2 catalysts under the water-gas shift (WGS) reaction. At temperatures above 250 degrees C, a complete AuOx -> Au transformation was observed with high catalytic activity. Photoemission results for the oxidation and reduction of Au nanoparticles supported on rough ceria films or a CeO2(111) single crystal corroborate that cationic Au delta+ species cannot be the key sites responsible for the WGS activity at high temperatures. The rate determining steps for the WGS seem to occur at the gold-ceria interface, with the active sites involving small gold clusters (< 2 nm) and O vacancies. (c) 2005 American Institute of Physics.