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Restructuring of AuPd Nanoparticles Studied by a Combined XAFS/DRIFTS Approach

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posted on 17.12.2015 by Emma K. Gibson, Andrew M. Beale, C. Richard A. Catlow, Arunabhiram Chutia, Diego Gianolio, Anna Gould, Anna Kroner, Khaled M. H. Mohammed, Michal Perdjon, Scott M. Rogers, Peter P. Wells
The use of AuPd nanoparticles in catalysis is widespread, with the activity being attributed to their precise structural properties. We demonstrate the restructuring of AuPd nanoparticles under CO oxidation conditions using a combined XAFS/DRIFTS approach. The fresh catalyst exhibits PdO islands at the surface of the nanoparticles, which are reduced under reaction conditions, a process observed via both DRIFTS and Pd K-edge XAFS measurements. From the EXAFS analysis alone the nanoparticles were observed to have a Au rich core with an outer region of intimately mixed Au and Pd atoms. This structure was found to remain mostly unaltered throughout reaction. However, the DRIFTS spectra showed that although Au was present on the surface during the initial stages of reaction the surface rearranged just before light-off, and contained only Pd atoms thereafter. This study highlights the advantage of this combined approach, where both the surface structure and local environment of the constituent metals can be probed simultaneously, allowing a complete picture of the restructuring of these bimetallic particles to be obtained under reaction conditions.

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