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Influence of the support on surface rearrangements of bimetallic nanoparticles in real catalysts

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Science  31 Oct 2014:
Vol. 346, Issue 6209, pp. 620-623
DOI: 10.1126/science.1258106

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Supported nanoparticles make the reaction faster

Several techniques now allow surface structures used as catalysts to be probed during exposure to reactive gases, as opposed to under vacuum conditions. Divins et al. used near-ambient-pressure x-ray photoelectron spectroscopy to compare the effect of reaction gases on unsupported palladium-rhodium nanoparticles versus ones on a reducible cerium oxide support. For the reaction of ethanol with steam to produce hydrogen, the supported nanoparticles were more reactive and less prone to reduction and surface rearrangement.

Science, this issue p. 620

Abstract

Catalysts used for heterogeneous processes are usually composed of metal nanoparticles dispersed over a high–surface-area support. In recent years, near-ambient pressure techniques have allowed catalyst characterization under operating conditions, overcoming the pressure gap effect. However, the use of model systems may not truly represent the changes that occur in real catalysts (the so-called material gap effect). Supports can play an important role in the catalytic process by providing new active sites and may strongly affect both the physical and chemical properties of metal nanoparticles. We used near-ambient pressure x-ray photoelectron spectroscopy to show that the surface rearrangement of bimetallic (rhodium-palladium) nanoparticles under working conditions for ethanol steam reforming with real catalysts is strongly influenced by the presence of a reducible ceria support.

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