4 research outputs found
DĂ©veloppement par PECVD de membranes conductrices protoniques de type phosphonique pour la production dâhydrogĂšne par (photo-)Ă©lectrolyse de lâeau
The purpose of this work was to develop phosphonic-type proton conductive membranes by radio-frequency PECVD in a continuous or pulsed discharge from the single precursor dimethyl allylphosphonate. Such membranes could advantageously replace the NafionÂź membrane or conventional sulfonic-type or phosphonic acid-type membranes, more classically used in PEM fuel cells and electrolysis devices. A parametric study was carried out in order to establish correlations between the properties of the films and the deposition parameters. It appears that the use of a pulsed discharge promotes better films properties, namely higher growth rate and lower density, than the continuous discharge, thus promoting proton conduction. It was also noticed that the deposits prepared in a pulsed discharge have the highest sorption and water retention capacities, which is particularly beneficial for the intended application i.e. the (photo-) electrolysis of water. Furthermore, all the plasma phosphonic membranes prepared are stable in terms of water retention and covalent network up to at least 250 °C, which ensures their use in systems able to operate up to 120 °C. Subsequently the plasma phosphonic membranes, deposited on the NafionÂź as mechanical support, were integrated as electrolyte membrane into a water electrolysis cell. It turns out that plasma phosphonic membranes are competitive enough to be envisaged in the future as integral solid electrolytes in solid membrane-electrodes assemblies.Le but de ces travaux Ă©tait de dĂ©velopper des membranes conductrices protoniques de type phosphonique par PECVD radio-frĂ©quence en dĂ©charges continue et pulsĂ©e Ă partir du mono-prĂ©curseur dimĂ©thyl allylphosphonate. De telles membranes sont pressenties comme pouvant avantageusement remplacer la membrane NafionÂź ou les membranes conventionnelles de type sulfonique ou phosphonique classiquement utilisĂ©es dans les dispositifs piles Ă combustible ou Ă©lectrolyseur de type PEM. Ainsi, une Ă©tude paramĂ©trique visant Ă Ă©tablir des corrĂ©lations entre les propriĂ©tĂ©s des films et les paramĂštres de dĂ©pĂŽt a Ă©tĂ© menĂ©e. Il ressort de cette Ă©tude paramĂ©trique que lâutilisation dâune dĂ©charge pulsĂ©e est favorable Ă une vitesse de croissance plus Ă©levĂ©e et une densitĂ© des films plus faible que le mode de dĂ©charge continue, favorisant ainsi la conduction protonique. Nous avons Ă©galement dĂ©montrĂ© que les dĂ©pĂŽts rĂ©alisĂ©s en mode de dĂ©charge pulsĂ©e prĂ©sentent de meilleures capacitĂ©s de sorption et de rĂ©tention dâeau, ce qui est bĂ©nĂ©fique pour lâapplication visĂ©e qui est la (photo-)Ă©lectrolyse de lâeau. Par ailleurs toutes les membranes phosphoniques plasma prĂ©parĂ©es sont stables dâun point de vue rĂ©tention dâeau et rĂ©seau covalent jusquâĂ au moins 250 °C, ce qui garantit leur utilisation dans des systĂšmes pouvant fonctionner jusquâĂ 120 °C. Par la suite, les membranes phosphoniques plasma ont Ă©tĂ© intĂ©grĂ©es en cellule dâĂ©lectrolyse de lâeau, associĂ©es au NafionÂź en tant quâĂ©lectrolyte. Les caractĂ©risations Ă©lectrochimiques en cellule ont montrĂ© que les membranes phosphoniques plasma sont suffisamment compĂ©titives pour ĂȘtre envisagĂ©es dans le futur comme Ă©lectrolytes solides Ă part entiĂšre dans des AME « tout solide »
Sorption and permeation of water through Plasma Enhanced Chemical Vapour Deposited phosphonic acid-based membranes
International audiencePhosphonic acid-based membranes were prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD) with an input power of 100 W in a continuous or pulsed glow discharge. Comparing both kinds of plasma discharges makes appear that the pulsed configuration gives rise to PECVD materials with longer hydrocarbon chains and thus higher flexible polymer network which consequently present better sorption properties than those prepared from a continuous plasma discharge. Being more hydrophilic and richer in acidic functions than NafionÂź 212, PECVD membranes (whatever the kind of plasma discharge, pulsed or continuous, during the deposition of films) present a better water sorption ability. Nevertheless, having a more highly cross-linked structure, they have a lower water diffusion/permeation capacity. Consequently PECVD membranes show singular water management properties which could be a great advantage for the final Proton-Exchange Membrane Electrolyte Cells and Proton-Exchange Membrane Fuel Cells applications