Abstract
Alumina supported gold catalyst prepared by spray reaction method (spr) provides gold particles with about 20 nm diameter. The gold particle size is larger than for conventional gold catalysts. However, the spr catalyst shows catalytic activity for NO–CO reaction. In the present paper, we discuss the local structures of spr-Au/Al2O3 catalyst by using Au L3-edge XANES spectra. In order to investigate the local structures of Au-sites, multiple scattering approach to XANES analysis was applied. Calculated Au L3-edge XANES spectrum for fcc-Au and Au2O3 were in good agreement with the observed spectra. XANES spectra for spr-Au/Al2O3 were characterized by 4 types of Au sites (bulk, interface, surface and peripheral). In this case, almost all gold sites (> 90%) are bulk sites. Less than 10% of the gold particles are in interface sites. However, the experimental result for spr-Au/Al2O3 requires about 30% of gold oxide or hydroxide. Bulk of Al2O3 contains a certain number of gold nano-particles, which was incorporated in the Al2O3 support. In the interface area, gold oxide forms a few layers. This result was also supported by DV-Xα electronic structure calculations.
Published Version
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