Structure and oxidation state of gold on different supports under various CO oxidation conditions

• Published in: Journal of catalysis Vol. 240; no. 2; pp. 100 - 107
• Main Authors: Weiher, N., Bus, E., Delannoy, L., Louis, C., Ramaker, D.E., Miller, J.T., van Bokhoven, J.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 10-06-2006; Elsevier
• Subjects: Alumina; Catalysis; Chemistry; CO oxidation; Exact sciences and technology; General and physical chemistry; Gold; Silica; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Titania; X-ray absorption spectroscopy; Gold; CO oxidation; X-ray absorption spectroscopy; Catalysis; Titania; Silica; Alumina; Catalytic reaction; Support; Transition element compounds; Transition metal; Supported catalyst; Heterogeneous catalysis; Oxidation; Carbon monoxide; Structure; Titanium oxide; X ray absorption
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2006.03.010

The structure of gold clusters of different sizes supported on various metal oxides (Al
2O
3, TiO
2, SiO
2) exposed to different CO oxidation conditions was investigated in situ using X-ray absorption spectroscopy at the Au L
3 edge. In all catalysts, the only phase detected during catalysis was Au
0. In the most active sample with small gold particles (Au/Al
2O
3), variation in the electronic structure of the gold clusters with changing reaction conditions was observed by XANES spectroscopy and ascribed to the adsorption of CO on the metallic gold clusters. FEFF8 calculations proved that the changes in the XANES signature of Au/Al
2O
3 can be explained by backdonation of d-electrons into the
π
∗
orbitals of CO. For Au/Al
2O
3, the presence of Au
O backscattering in the EXAFS suggested weak cluster–support interactions. For Au/SiO
2 and Au/TiO
2, the structure of the gold clusters remained unchanged throughout all experiments.