Removal of Carbonaceous Residues by Deuterium from Pt Catalysts

Wootsch, Attila; Descorme, C.; Paál, Z.; Duprez, Daniel

doi:10.1006/jcat.2002.3557

Cited by 52 publications

(98 citation statements)

References 72 publications

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“…Two catalysts with nominally 1% and 5% metal loadings were prepared on the same ceria support used in Part [12,27]. The impregnated samples were dried at 393 K overnight and calcined for 4 hours at 773 K in flowing air (30 mL/min) and reduced at 672 K for 4 hours in flowing H 2 (30 mL/min).…”

Section: Catalystsmentioning

confidence: 99%

“…Catalyst formulations found to be active in the PROX reaction can be classified as: gold based catalysts [5][6][7][8], supported Pt [5,[8][9][10][11][12], Rh [9], Ru [9,13], and bimetallic Pt-Sn [11,14] and other systems not containing metallic phase, such as CuO/CeO 2 [5,15]. These systems, as a rule, are also active in the low temperature CO oxidation.…”

Section: Introductionmentioning

confidence: 99%

“…A group of authors [9,12] explains this fact by the change in the oxidation state of Pd. The highly active reduced Pd form 2 (active in low temperature CO oxidation) can be oxidized to PdO x , which is less active in CO oxidation (without hydrogen).…”

Section: Introductionmentioning

confidence: 99%

“…The aim of this paper is to clarify the reaction mechanism of both CO oxidation and the PROX reaction on a Pd catalyst, study the role of the reducible ceria support, and to compare its behaviour with Pt/CeO 2 , which was found to be remarkably active in the PROX reaction [1,12].…”

Section: Introductionmentioning

confidence: 99%

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Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part II: Oxidation states and surface species on Pd/CeO2 under reaction conditions, suggested reaction mechanism

Pozdnyakova

Teschner

Wootsch

et al. 2006

Journal of Catalysis

198

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The aim of the PROX reaction is to reduce the CO content of hydrogen feed to proton exchange membrane fuel cells (PEMFC) by selective oxidation of CO in the presence of excess hydrogen. Both Pt and Pd on ceria are active in CO oxidation (without hydrogen) while Pd is poorly active in the presence of hydrogen. In this paper we aimed at finding the reasons of such behavior, using the same techniques for Pd/CeO 2 as for Pt/CeO 2 in Part I: catalytic tests, in-situ DRIFTS, high-pressure XPS, HRTEM and TDS. The reaction mechanism of CO oxidation (without hydrogen) was also examined. It does not occur via the exactly same mechanism on Pt and Pd/CeO 2 catalyst. In the presence of hydrogen (PROX) at low temperature (T=350-380 K), the formation of Pd β-hydride was confirmed by high-pressure in-situ XPS. Its formation greatly suppressed the possibility of CO oxidation, because oxygen both from gas phase and support sites reacted fast with hydride H to form water, and this water desorbed from Pd easily. Nevertheless, CO adsorption was not hampered here. These entities transformed mainly to surface formate and formyl (-CHO) species instead of oxidation as observed by DRIFTS. The participation of a low-temperature water-gas-shift type reaction proposed for the platinum system [Part I] was hindered. Increasing temperature led to decomposition of the hydride phase and a parallel increase in the selectivity towards CO oxidation was observed. However, it remained still lower on Pd/CeO 2 than on Pt/CeO 2 .

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Section: Catalystsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part II: Oxidation states and surface species on Pd/CeO2 under reaction conditions, suggested reaction mechanism

Pozdnyakova

Teschner

Wootsch

et al. 2006

Journal of Catalysis

198

View full text Add to dashboard Cite

show abstract

“…Apparently, those oxygen vacancies at the metalsupport interface favor the activation of the CO molecule and provide active sites for the oxidation to CO 2 [49]. On the contrary, in the chlorinated catalyst, chlorine inhibited the formation of those oxygen vacancies due to the formation of CeOCl surface species [22,50,51]. This process was favored at high reduction temperatures.…”

Section: Co Prox: Effect Of Reaction and Reduction Temperaturementioning

confidence: 99%

Influence of the metal precursor on the catalytic behavior of Pt/Ceria catalysts in the preferential oxidation of CO in the presence of H2 (PROX)

Jardim

Rico-Francés

Coloma

et al. 2015

Journal of Colloid and Interface Science

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The effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H2 over Pt/CeO2 catalysts has been studied. The catalysts were prepared using (Pt(NH3)4)(NO3)2 and H2PtCl6, as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst. This is a previous version of the article published in Journal of Colloid and Interface Science. 2015, 443: 45-55. doi:10.1016/j.jcis.2014 3: Graphical Abstract (for review)• The presence or absence of Cl in the Pt precursor strongly affects the catalytic behavior.• The Pt precursor affects the PROX mechanism at low reaction temperatures.• At 333 K, the mechanism in the Cl-free catalyst seems to involve the -OH groups on the support.• At higher temperatures, the reaction occurs via the same mechanism on both catalysts.. Highlights (for review) AbstractThe effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H 2 over Pt/CeO 2 catalysts has been studied. The catalysts are prepared using (Pt(NH 3 ) 4 )(NO 3 ) 2 and H 2 PtCl 6 , as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO 2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst.

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25th Anniversary Article: Scalable Multiscale Patterned Structures Inspired by Nature: the Role of Hierarchy

et al. 2013

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Multiscale, hierarchically patterned surfaces, such as lotus leaves, butterfly wings, adhesion pads of gecko lizards are abundantly found in nature, where microstructures are usually used to strengthen the mechanical stability while nanostructures offer the main functionality, i.e., wettability, structural color, or dry adhesion. To emulate such hierarchical structures in nature, multiscale, multilevel patterning has been extensively utilized for the last few decades towards various applications ranging from wetting control, structural colors, to tissue scaffolds. In this review, we highlight recent advances in scalable multiscale patterning to bring about improved functions that can even surpass those found in nature, with particular focus on the analogy between natural and synthetic architectures in terms of the role of different length scales. This review is organized into four sections. First, the role and importance of multiscale, hierarchical structures is described with four representative examples. Second, recent achievements in multiscale patterning are introduced with their strengths and weaknesses. Third, four application areas of wetting control, dry adhesives, selectively filtrating membranes, and multiscale tissue scaffolds are overviewed by stressing out how and why multiscale structures need to be incorporated to carry out their performances. Finally, we present future directions and challenges for scalable, multiscale patterned surfaces.

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Removal of Carbonaceous Residues by Deuterium from Pt Catalysts

Cited by 52 publications

References 72 publications

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part II: Oxidation states and surface species on Pd/CeO2 under reaction conditions, suggested reaction mechanism

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part II: Oxidation states and surface species on Pd/CeO2 under reaction conditions, suggested reaction mechanism

Influence of the metal precursor on the catalytic behavior of Pt/Ceria catalysts in the preferential oxidation of CO in the presence of H2 (PROX)

25th Anniversary Article: Scalable Multiscale Patterned Structures Inspired by Nature: the Role of Hierarchy

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