Abstract
AbstractThe effect of ceria doping by oxide surface modification and controlled metal surface modification (CSM) on the structure-function properties of Rh/γ-Al2O3 catalysts in the process of CO oxidation were studied by a combined array of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)/Energy Dispersive X-ray Absorption Fine Structure/Mass Spectrometry techniques applied simultaneously under time-resolved, in situ conditions in the temperature range of 298–573 K. The addition of each promoter element by CSM exhibits multiple effects on the catalysts structure. The DRIFTS/XAS studies indicate that CeOx facilitate the protection of Rh particles against extensive oxidation in atmospheres of air, O2 and CO, without reducing the coverage of oxidisable adsorbed CO.
Highlights
The process of CO oxidation over Rh catalysts has been a subject of many experimental investigations [1,2,3,4,5,6] due to its industrial and environmental importance of removing CO from chemical processes and automotive exhausts [7,8,9], and traces of CO from H2 feed gas for fuel cells [10,11]
Either by oxide surface modification (OSM) of the alumina, or by controlled surface modification (CSM) of the pre-formed rhodium particles, a close proximity of these elements on the alumina surface was confirmed by EDX measurement [15]; in contrast, segregation was observed more with conventional methods using inorganic sources
Based on the extended X-ray absorption fine structure (EDE)/Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)/mass spectrometry (MS) data on CSM ceriated Rh catalyst we can confirm a presence of larger Rh particles and a close proximity between Rh and CeOx molecules which influences a structural behaviour of this catalyst upon CO oxidation
Summary
The process of CO oxidation over Rh catalysts has been a subject of many experimental investigations [1,2,3,4,5,6] due to its industrial and environmental importance of removing CO from chemical processes and automotive exhausts [7,8,9], and traces of CO from H2 feed gas for fuel cells [10,11]. In the CO/O2 switches the proportion of RhI(CO)2 increases, indicating that more Rh(+) species are present in studied catalysts and the subsequent O2 exposures cause further structural disruption of Rh particles.
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