Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions |
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Authors: | Weiling Deng Colin Carpenter Nan Yi Maria Flytzani-Stephanopoulos |
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Affiliation: | (1) Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, USA;(2) Present address: Dartmouth College, Hanover, NH 3755, USA |
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Abstract: | We compare the activity and relevant gold species of nanostructured gold–cerium oxide and gold–iron oxide catalysts for the
CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO
oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze
the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium
cyanide at pH ≥12. Both parent and leached catalysts were investigated. The activity of the leached gold–iron oxide catalyst
in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to
H2 up to 400 °C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of
the CO oxidation activity. Similar results were found with the gold–ceria catalysts. On the other hand, pre-reduction of the
calcined leached catalyst samples did not promote their water-gas shift activity. UV–Vis, XANES and XPS were used to probe
the oxidation state of the catalysts after various treatments. |
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Keywords: | gold iron oxide cerium oxide CO oxidation water-gas shift reaction |
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