Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

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 H 2 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.

Low Temperature Oxidation of Carbon Monoxide over Mesoporous Au-Fe2O3Catalysts

“…It was widely reported that properties of catalysts, such as particle size, active metal dispersion, surface area, and strength of interaction, have a great influence on the redox properties and reactivity [50]. The behavior of Au supported catalysts was mainly attributed to the electronic interaction between the Au and support [51] as well as the contribution from H 2 pretreatment prior to the reaction.…”

Geometric and electronic structure of Au on Au/CeO2catalysts during the CO oxidation: Deactivation by reaction induced particle growth

“…While some groups claimed that gold in ionic form (Au + , Au 3+ ) is predominantly responsible for the activity of the Au catalysts [5], other groups suggested that metallic Au 0 NPs represent the active species during reaction [6]. Likewise, deactivation of Au/CeO 2 catalysts during CO oxidation had been proposed to mainly originate from (i) effects associated with changes of the formal oxidation state of Au [5,7], (ii) the build-up of surface poisoning carbon containing species at the perimeter of the Au-support interface [8], and/or (iii) sintering of Au NPs during reaction [7,9].…”

The nature of oxygen states on the surfaces of CeO2 and La-doped CeO2

“…CeO 2 is a valuable material for a range of catalytic applications, such as threeway-catalysts (TWC) for automotive emissions, [1] water-gas-shift reactions, [2][3][4] and soot oxidation. [5,6] The effectiveness of CeO 2 as a catalyst is associated with its high oxygen storage capacity (OSC), i.e.…”