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Activity and Relevant Spectroscopic Features of Gold-Ceria Catalysts for the Catalytic Oxidation of Carbon Monoxide

Weiling Deng1, Maria Flytzani-Stephanopoulos1, Maela Manzoli2, Flora Boccuzzi2, Anna Chiorino2, and Floriana Vindigni2. (1) Chemical and Biological Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, (2) Dipartimento di Chimica IFM and NIS Centre of Excellence, UniversitÓ di Torino, Torino 10125, Italy

Gold/cerium oxide is one of the most active catalysts reported to date for the catalytic oxidation of carbon monoxide by various oxidants, such as oxygen in low- temperature dry CO oxidation [1], and the PROX reaction in the presence of large amount of hydrogen and water [2]; and water in low- temperature WGS reaction [2-5]. In this work, fundamental studies of the interactions of gold/ cerium oxide with CO are reported to shed light on the activity/stability of various structures in oxygen and water.

An FTIR study of CO adsorption from 120 K up to r.t. on high- and low- content Au/CeO2 samples identified some special features, unique to the gold-ceria system. In particular, a broad absorption in the 2130-2140 cm-1 range, more resistant to oxidation than the usual band of CO on the Au0 sites, assigned to CO interacting with cationic gold clusters, has been observed. These species show lower reactivity to oxygen than CO adsorbed on the Au0 particles, beginning to produce CO2 at ~310 K, while CO adsorbed on metallic gold forms CO2 below room temperature. On both the high- and low-content gold-ceria samples, a broad CO absorption band in the range 2000-2100 cm-1 was observed following a reduction treatment at 473 K. This is assigned to negatively charged gold species. Upon oxidation, these species are again transformed to positively charged clusters. XPS and cyclic CO- and H2-TPR data corroborate the catalysis and the FTIR results.

References

1. W. Liu, M. Flytzani-Stephanopoulos, J. Catal. 153 (1995) 304-316 & 317-332. 2. W. Deng, J. De Jesus, H. Saltsburg, M. Flytzani-Stephanopoulos, Appl. Catal. A 291 (2005) 126-135. 3. Q. Fu, H. Saltsburg, M. Flytzani-Stephanopoulos, Science 301 (2003) 935. 4. Q. Fu, W. Deng, H. Saltsburg, M. Flytzani-Stephanopoulos, Appl. Catal. B 56 (2005) 57-68. 5. W. Deng, M. Flytzani-Stephanopoulos, Angew. Chem. Int. Ed. 45 (2006) 2285-2289. 6. Manzoli et al. J. Catal., in review (2006).