Water-gas shift reaction on Cu and Au nanoparticles supported on CeO₂ and ZnO: Intrinsic activity and importance of support interactions

Synchrotron-based techniques (high-resolution photoemission, in-situ X-ray absorption spectroscopy, and time-resolved X-ray diffraction) have been used to study the water-gas shift (WGS, CO + H2O → H2 + CO2) reaction on a series catalysts. Au and Cu nanoparticles supported on CeO2(111) display an extraordinary catalytic activity for the WGS reaction that is not seen on a ZnO(000i) support or for the bulk metal. The behaviour of Au/ceria in the WGS illustrates the essential role that an oxide can have for the activity of supported Au nanocatalysts. In-situ time-resolved x-ray diffraction and x-ray absorption spectroscopy were used to monitor the behavior of nanostructured {Au+AuOx}-CeO2 catalysts under the WGS reaction. At temperatures above 250 C, a complete AuOx→Au transformation was observed with high catalytic activity. The active sites in {Au + AuOx}/ceria catalysts involve pure gold nanoparticles in contact with O vacancies of the oxide support.