The key role of highly dispersed rhodium in the chemistry of hydrogen–ceria systems

Bernal, S.; Calvino, José J.; Cifredo, G.A.; Rodrı́guez-Izquierdo, J.M.; Perrichon, V.; Laachir, A.

doi:10.1039/c39920000460

Cited by 58 publications

(62 citation statements)

References 9 publications

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“…[20][21][22] One may therefore speculate that scavenging of hydrogen from the gold by the support acts to promote the above two reactions, but not the homocoupling of iodobenzene to produce biphenyl, in accord with observation.…”

mentioning

confidence: 69%

Identity of the Active Site in Gold Nanoparticle-Catalyzed Sonogashira Coupling of Phenylacetylene and Iodobenzene

2010

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XPS, TEM, and reaction studies were used to examine the catalytic behavior of gold species deposited on lanthana toward the cross-coupling of phenylacetylene and iodobenzene. Atomically dispersed Au I and Au III were catalytically inert, whereas metallic Au 0 nanoparticles were both active and very selective. Thus it is metallic gold and not ionic gold that provides the catalytically active sites. Au 0 nanoparticles supported on silica, γ-alumina, and BaO were active but relatively unselective; however, as with lanthana, ceria-supported Au 0 nanoparticles showed high selectivity. This strong promoting effect of the lanthanide oxide supports on Sonogashira selectivity cannot be accounted for in terms of acid/base, redox, or SMSI effects; it may be tentatively ascribed to metal f support hydrogen spillover.

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mentioning

confidence: 69%

Identity of the Active Site in Gold Nanoparticle-Catalyzed Sonogashira Coupling of Phenylacetylene and Iodobenzene

2010

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“…Metal dispersion can be achieved by selective chemisorption of probe molecules such as H 2 and CO. Because the support is able to chemisorb large quantities of H 2 (spillover) and CO for the CeO 2 -containing materials even at room temperature [20][21][22][23][24][25], physical techniques such as XRD, TEM, and HTEM are also used to estimate metal dispersion [5,23,26]. It has been found that H 2 chemisorption at 191 K [27] and CO chemisorption at 195 K [28,29] can be used as al-ternative methods to measure the metal dispersion on ceria.…”

Section: Pd Dispersionmentioning

confidence: 99%

Low-temperature oxidation of CO over Pd/CeO2–TiO2 catalysts with different pretreatments

Zhu

Qin

Shan

et al. 2005

Journal of Catalysis

145

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“…A number of publications has been devoted to ceria containing catalysts investigating chemisorptive [27,28], structural [29,30] and catalytic properties [18,31]. Adsorption of CO on ceria supported catalysts leads to accumulation of different carboxylate, carbonate and formate species on the ceria surface as revealed from infrared spectroscopic studies [32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part I: Oxidation state and surface species on Pt/CeO2 under reaction conditions

Pozdnyakova

Teschner

Wootsch

et al. 2006

Journal of Catalysis

374

244

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The CO content of hydrogen feed to proton exchange membrane fuel cells (PEMFC) must be kept under 1-100 ppm for their proper operation. This can be achieved by using catalysts able to selectively oxidize CO in the presence of excess hydrogen (PROX). The present study reports on the mechanism of PROX reaction on Pt/CeO 2 catalyst, by using catalytic tests, in-situ DRIFTS, high-pressure XPS, HRTEM and TDS techniques. Bulk metallic, pronounced adsorbate-induced surface Pt and a small amount of oxidized Pt sites were detected by in-situ, high pressure XPS under PROX conditions. The pre-oxidized ceria surface was strongly reduced in pure H 2 but significantly re-oxidized under PROX conditions (i.e. O 2 +CO in excess hydrogen) at T=358 K. The remaining small amount of Ce 3+ decreased with increasing temperature. HRTEM found well-crystallized CeO 2 particles (8-10 nm) in the case of activated (pre-oxidized) sample that transformed in a large extent to an oxygen deficient ceria super-cell structure after PROX reaction. Metallic Pt particles (2-3 nm) and small (0.5-0.6 nm) Pt clusters were found by HRTEM. These findings were in accordance with the variations in relative intensity of the corresponding Pt-CO bands (DRIFTS). Different types of carbonate and formate species were detected (XPS and DRIFTS). Their possible role in the reaction mechanism is discussed. Resolved OH bands could not be found by DRIFT in the PROX reaction mixture indicating significant amount of adsorbed water in a hydrogen-bonded structure. Its presence seems to suppress hydrogen oxidation while CO oxidation still takes place, as the metallic particles are covered by CO (DRIFTS). The direct contribution of surface water in a low-temperature water-gas-shift (LTWGS) type reaction in the PROX mixture is proposed.

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The key role of highly dispersed rhodium in the chemistry of hydrogen–ceria systems

Cited by 58 publications

References 9 publications

Identity of the Active Site in Gold Nanoparticle-Catalyzed Sonogashira Coupling of Phenylacetylene and Iodobenzene

Identity of the Active Site in Gold Nanoparticle-Catalyzed Sonogashira Coupling of Phenylacetylene and Iodobenzene

Low-temperature oxidation of CO over Pd/CeO2–TiO2 catalysts with different pretreatments

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part I: Oxidation state and surface species on Pt/CeO2 under reaction conditions

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