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

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Jose A. Rodriguez, rodrigez@bnl.gov, Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973, Xianqin Wang, xianqin@gmail.com, Depatment of Chemistry, Brookhaven National Laboratory, Upton, NY 11973, Ping Liu, pingliu3@bnl.gov, Chemistry Department, Brookhaven National Laboratory, Upton, NY NY 11973, Jonathan C. Hanson, Chemistry Department, Brookhaven National Laboratory, Bldg.555, Upton, NY 11973, and Jan Hrbek, hrbek@bnl.gov, Brookhaven National Laboratory, Chemistry 555, Upton, NY 11973.
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(000) 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.