The present study focuses on the modification of surface compositional profiles induced in nanoporous (NP) Au catalysts by the catalytic oxidation of carbon monoxide to carbon dioxide in the presence of oxygen. The phenomenon has deep implications concerning the catalytic behavior of NP Au foams in particular, and more in general for the design of more efficient catalysts. Aimed at gaining deeper insight into the mechanisms governing surface segregation, we exposed NP Au foams containing residual Ag to a mixture of gaseous carbon monoxide and oxygen at different temperature. Structural and surface composition analyses pointed out the concomitant occurrence of both NP Au coarsening and Ag surface segregation processes. Experimental findings suggest for Ag surface segregation a two-stage kinetics. During the initial, rapid coarsening of the NP Au structure, Ag surface segregation is mediated by surface rearrangements, which allow the Ag atoms to reach the surface at anomalously fast rate. As coarsening decelerates, the slower diffusion of buried Ag atoms towards the surface predominates, due to favorable chemical interactions with adsorbed oxygen. This novel mechanism’s understanding can benefit strategic areas of science and technology.
Ag surface segregation in nanoporous Au catalysts during CO oxidation / G. Pia, E. Sogne, A. Falqui, F. Delogu. - In: SCIENTIFIC REPORTS. - ISSN 2045-2322. - 8:1(2018), pp. 15208.1-15208.9.
|Titolo:||Ag surface segregation in nanoporous Au catalysts during CO oxidation|
FALQUI, ANDREA (Penultimo)
|Parole Chiave:||gold catalyst; chemistry|
|Settore Scientifico Disciplinare:||Settore FIS/03 - Fisica della Materia|
|Data di pubblicazione:||2018|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1038/s41598-018-33631-4|
|Appare nelle tipologie:||01 - Articolo su periodico|
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