Investigation on Active Sites in Pt−Mo on Silica Catalysts for Reactions of Hydrocarbons with Hydrogen

Leclercq, G.; Pietrzyk, S.; Romero, Trino; Gharbi, A. El; Gengembre, L.; Grimblot, J.; Aïssi, Faustin; Guelton, M.; Latef, A.; Leclercq, Loı̈c

doi:10.1021/ie9606303

Cited by 18 publications

(5 citation statements)

References 51 publications

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“…For the Pt-Ru catalysts made according to the same procedure, 24 the Pt/Ru surface atomic ratios were 2.1 and 2.4, respectively. This slight surface enrichment in Mo relative to the bulk has already been observed by other authors 14 and are probably due to the presence of oxidized species at the surface.…”

Section: Resultssupporting

confidence: 83%

“…Similar results were obtained for Pt-Mo chemical catalysts obtained on silica. 14 Figure 4 also presents the XPS narrow-scan spectra of Mo 3d for Pt 0.5 Mo 0.5 (Al) 4 34,35 This is the major species found in the upper layer of the Mo powder probed by XPS. On the other hand, the binding energy at 231.0-231.1 eV corresponds to Mo(V) 35 which is found at about equal concentration with Mo(VI) in the upper layer of the ballmilled catalyst.…”

Section: Resultsmentioning

confidence: 99%

“…Similar results were obtained for Pt-Mo chemical catalysts obtained on silica. 14 Figure 4 Table III. Each spectrum is composed of three doublets characteristic of Mo 3d.…”

Section: Xrd Results Surface Area Measurements and Sem Micrographs-fi...mentioning

confidence: 99%

“…In that case, a catalytic site for the reaction of hydrocarbons with hydrogen was also assigned to an interaction between a Mo(V) species with Pt. 14 Fuel cell tests and CO tolerance.-Figure 6A presents the polarization curves in H 2 /O 2 of a single membrane-electrode assembly (MEA), using Pt 0.5 Mo 0.5 (Al) 4 and Pt 0.5 Mo 0.5 (MgH 2 ) 4 as anode catalysts. For the sake of comparison, the polarization curves obtained with Pt black and Pt 0.5 Ru 0.5 black are also given in the same figure.…”

Section: Xrd Results Surface Area Measurements and Sem Micrographs-fi...mentioning

confidence: 99%

“…13 Pt-Mo alloys are also known in chemical catalysis, for instance to promote reactions of hydrocarbons with hydrogen. 14 High-energy ballmilling or mechanical alloying is an interesting low-temperature alloying technique. 15 The principle of mechanical alloying is simple.…”

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High Energy Ballmilled Pt-Mo Catalysts for Polymer Electrolyte Fuel Cells and Their Tolerance to CO

Gouérec

Denis

Guay

et al. 2000

J. Electrochem. Soc.

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Polymer electrolyte fuel cells are clean, efficient electrical generators based on the electrochemical oxidation of hydrogen by oxygen. Both electrochemical reactions require catalysts such as Pt to operate at a useful rate. However, Pt is easily poisoned by CO, and significant power losses may arise when H 2 is obtained from the reforming of alcohols or hydrocarbons. Even 10 ppm CO in the H 2 feedstream has a detrimental effect on the fuel cell performance. 1 Binary electrocatalysts have been used with success to alleviate CO poisoning problems at the anode of polymer electrolyte fuel cells. They contain a more oxidizable element with the ability to activate oxygenated species at lower potentials in order to initiate CO oxidation. The most studied CO-tolerant anode catalysts are certainly Pt-Ru and Pt-Sn alloys (see Ref. 2 and references cited therein). Recently, several authors reported CO tolerance for new anode catalysts containing Mo which are of technical interest for low-temperature fuel cells fed with a reformed fuel and for direct methanol fuel cells (DMFCs). These catalysts are either binary Pt-Mo alloys [3][4][5][6][7][8] or ternary alloys such as Pt-Ru-Mo or Pt-Co-Mo, 7,9,10 or even composite Pt-based catalysts containing Mo oxides. 10-12 The best-performing CO-tolerant catalyst based on a Pt-Mo binary alloy has a Pt/Mo ϭ 4 surface atomic ratio. 3-6 It is of interest to develop Pt-Mo catalysts because Mo is a transition metal which is not expensive and is readily available. Furthermore, Mo is soluble in Pt, at least up to 28 wt %. 13 Pt-Mo alloys are also known in chemical catalysis, for instance to promote reactions of hydrocarbons with hydrogen. 14 High-energy ballmilling or mechanical alloying is an interesting low-temperature alloying technique. 15 The principle of mechanical alloying is simple. A vial containing the powder to be milled and the grinding balls is swung energetically several thousand times a minute. The balls impact at high velocity against the sample and the walls of the vial, thereby both milling and mixing the sample. Crystallites of nanometric dimensions are obtained during mechanical alloying. This paper is part of a series of articles intending to demonstrate that it is possible to adapt the technique of high-energy ballmilling to the preparation of interesting catalysts for fuel cells using a protonic membrane, e.g., polymer electrolyte membrane (PEM) fuel cells and direct methanol fuel cell (DMFCs). As it is easy to prepare unsupported catalysts by high-energy ballmilling, this technique is particularly well-adapted for the production of catalysts for DMFCs, for which large amounts (from 1 to 5 mg of metal/cm 2 ) of Pt and CO-tolerant Pt alloys (usually Pt-Ru alloys) are used at the cathode and the anode, respectively. [16][17][18][19][20][21][22] However, before using mechanical alloying to prepare novel catalysts for the anode of DMFCs, it is necessary to demonstrate that this technique is able to produce well-known CO tolerant catalysts based on Pt and Ru or Pt and Mo. Pr...

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

“…Similar results were obtained for Pt-Mo chemical catalysts obtained on silica. 14 Figure 4 Table III. Each spectrum is composed of three doublets characteristic of Mo 3d.…”

Section: Xrd Results Surface Area Measurements and Sem Micrographs-fi...mentioning

confidence: 99%

Section: Xrd Results Surface Area Measurements and Sem Micrographs-fi...mentioning

confidence: 99%

mentioning

confidence: 99%

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High Energy Ballmilled Pt-Mo Catalysts for Polymer Electrolyte Fuel Cells and Their Tolerance to CO

Gouérec

Denis

Guay

et al. 2000

J. Electrochem. Soc.

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ChemInform Abstract: Active Sites in Pt‐Mo on Silica Catalysts for Reactions of Hydrocarbons with Hydrogen

et al. 1997

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Hydrogenation of the Aromatic Ring

Metal-Catalysed Reactions of Hydrocarbons

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Investigation on Active Sites in Pt−Mo on Silica Catalysts for Reactions of Hydrocarbons with Hydrogen

Cited by 18 publications

References 51 publications

High Energy Ballmilled Pt-Mo Catalysts for Polymer Electrolyte Fuel Cells and Their Tolerance to CO

High Energy Ballmilled Pt-Mo Catalysts for Polymer Electrolyte Fuel Cells and Their Tolerance to CO

ChemInform Abstract: Active Sites in Pt‐Mo on Silica Catalysts for Reactions of Hydrocarbons with Hydrogen

Hydrogenation of the Aromatic Ring

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