Gold Nanoparticles on Ceria: Importance of O Vacancies in the Activation of Gold
Synchrotron-based techniques (high-resolution photoemission, in-situ X-ray absorption spectroscopy, and time-resolved X-ray diffraction) have been used to study the destruction of SO{sub 2} and the water-gas shift (WGS, CO + H{sub 2}O {yields} H{sub 2} + CO{sub 2}) reaction on a series of gold/ceria systems. The adsorption and chemistry of SO{sub 2} was investigated on Au/CeO{sub 2}(111) and AuO{sub x} /CeO{sub 2} surfaces. The heat of adsorption of the molecule on Au nanoparticles supported on stoichiometric CeO{sub 2}(111) was 4-7 kcal/mol larger than on Au(111). However, there was negligible dissociation of SO{sub 2} on the Au/CeO{sub 2}(111) surfaces. The full decomposition of SO{sub 2} was observed only after introducing O vacancies in the ceria support. AuO{sub x} /CeO{sub 2} surfaces were found to be much less chemically active than Au/CeO{sub 2}(111) or Au/CeO{sub 2-x} (111) surfaces. In a separate set of experiments, in-situ time-resolved X-ray diffraction and X-ray absorption spectroscopy were used to monitor the behavior of nanostructured (Au + AuO{sub x})-CeO{sub 2} catalysts under the WGS reaction. At temperatures above 250 C, a complete AuO{sub x} {yields} Au transformation was observed with high catalytic activity. Photoemission results for the oxidation and reduction of Au nanoparticles supported on rough ceria films or a CeO{sub 2}(111) single crystal corroborate that cationic Au{sup {delta}+} species cannot be the key sites responsible for the WGS activity at high temperatures. The active sites in (Au + AuO{sub x})/ceria catalysts should involve pure gold nanoparticles in contact with O vacancies of the oxide.
- Research Organization:
- Brookhaven National Laboratory (BNL) National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 929928
- Report Number(s):
- BNL--80522-2008-JA
- Journal Information:
- Topics in Catalysis, Journal Name: Topics in Catalysis Journal Issue: 39449 Vol. 44
- Country of Publication:
- United States
- Language:
- English
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