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Élaboration et caractérisation de nouveaux matériaux d'électrodes pour pile à combustible à membrane échangeuse de protons : catalyseurs à base de tungstène supportés sur un dérivé du graphite expansé

Abstract : This work is implicated in the development of carbon materials and of materials for energy applications. In the first part, we aim to totally or partially replace the platinum catalyst of the Proton Exchange Membrane Fuel Cell by less expensive and more abundant materials. In the second part, we optimize the catalytic sites accessibility for the reactants. WCl6 was impregnated on the Expanded Graphite derivated substrate by gaseous transport under chlorine pressure before being reduced and/or carburized in order to obtain tungsten derivatives (tungsten, tungsten carbides). The nature and size of the nanoparticles depend on the reducing or carburizing gas composition (H2 or H2/CH4 mixture) and the reaction temperature. Reduction is not complete until 500°C when using H2. W2C and WC mixtures are formed when using H2/CH4 mixtures (90/10, 85/15 or 80/20). The temperature increasing favours the sintering effect but not the complete carburization. All these obtained catalysts show low electrocatalytic performances when tested on a half-cell system. Platinum-tungsten hemicarbides catalysts were obtained by a successive deposition of PtCl4 and WCl6 while the reduction-carburization step was realized at 900°C under H2/CH4 mixture (85/15). These materials show higher electrocatalytic performances than a commercial platinum catalyst for an equivalent platinum ratio. The final part of this work concerns the carbon support functionnalization with sulfonate groups. Polystyrene sufonate grafting seems efficient for it helps to reduce the Nafion quantities used in the electrodes and to increase the electrocatalytic performances
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Nathalie Hugot. Élaboration et caractérisation de nouveaux matériaux d'électrodes pour pile à combustible à membrane échangeuse de protons : catalyseurs à base de tungstène supportés sur un dérivé du graphite expansé. Autre. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0061⟩. ⟨tel-01749586⟩

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