The project tackles the design of disruptive ion exchange membranes intended to electrochemical cells for the energy domain, namely alkaline polymer electrolyte fuel cells / electrolyzers (SAMFC / SAMEC).
Alkaline cells have the advantage of being cheaper to manufacture than their acidic counterparts (PEMFC / PEMEC) because they do not require a noble metal catalyst (typically platinum) to induce electrochemical oxygen reduction with suitable kinetics. Indeed, the kinetics of electrochemical reactions are easier in basic medium than in acidic medium. However, contrary to the acidic process for which the polymer electrolyte Nafion has largely demonstrated its competitiveness, there is no commercially recognized membrane for SAMFC / SAMEC technologies. Therefore, for the medium or long term commercial aims of the alkaline process, new alkaline polymer electrolytes must be developed. These electrolytes must have: a sufficiently high hydroxyl conduction (> 10 mS.cm-1), sufficient mechanical strength to limit the swelling of the membrane during water sorption, and good chemical stability to withstand a high pH and an operating temperature close to 100°C. It is known that conventional polymer membranes developed for these systems often suffer from insufficient chemical, thermal and mechanical stability; in addition, adhesion to electrodes and water management are not always optimal. Plasma processes can provide interesting solutions to these problems.
This research project concerns the manufacture of anionic conductive membranes by plasma polymerization. Plasma polymerization allows the deposition at room temperature of uniform, dense, amorphous, highly cross-linked and perfectly adherent thin films on any substrate, whose structural and transport properties can be largely modulated by the variation of process parameters (pressure, electrical power, flow of the deposition precursors). Independently of the intrinsic characteristics of plasma polymer membranes (in particular their high cross-linking rate favorable to a good retention of liquids and gases and a good chemical/mechanical/thermal stability), one of the major advantages of plasma polymerization is to make these membranes growing directly on the electrodes of the cells/electrolyzers with good adhesion, thus allowing the obtaining of very good quality interfaces. Moreover, plasma polymerization is a cheap and clean synthesis method, using no solvents and releasing no toxic effluents.
The objective of this PhD project is to prepare anionic conductive membranes by plasma polymerization and to characterize them in terms of morphology, structure, functionality and stability. Their performance as a key part of SAMFC / SAMEC will also be investigated.
The proposal is strongly in line with the policy of hydrogen materials and mobility development of the industrial partner and its ambitions. For more information: https://www.michelin.com/hydrogene/