New Aryl Monomers, Polymers and Membranes for PEMFC and DMFC

摘要

This contribution comprises an overview about the work done by our research group in the development of ionomers/ionomer (blend) membranes for membrane fuel cells. The topics include the development of novel sulfonated arylene nonfluorinated and partially fluorinated monomers and their polycondensation to homopolymers, block and statistical copolymers; the preparation of ionically cross-linked membranes prepared by mixing these polymers with different polybenzimidazoles (PBI); the application of these membranes to PEFC and DMFC; development of novel base-excess PBI/sulfonated polymer/H3PO4 blend membranes, and test of these membranes in fuel cells at intermediate fuel cell operation temperatures (170-200°C). From the sulfonated homo- and block-co-ionomers, acid-excess ionically cross-linked membranes have been prepared by mixing the sulfonated ionomers with different PBIs. These membranes have been tested in a DMFC in order to investigate their suitability for the DMFC up to a temperature of 60°C under atmospheric pressure which is interesting for the use of DMFC as power supply for mobile electronic applications, under comparison with Nafion~R. The i/U polarization curves of the membranes along with their meOH permeability showed a better performance than Nafion~R which is due to the lower meOH permeability of the arylene ionomer membranes, compared to Nafion~R. Acid-base blend membranes were also applied to the HyS electrolysis process, showing good stability and electrolysis performance. Phosphonated polymers and ternary PBI/sulfonated polymer/H3PO4 blend membranes for the application in intermediate T fuel cells have been developed as well. These membranes showed good performance in fuel cells in the temperature range 125-200°C, their chemical stability being even better than that of pure PBI membranes, which was ascertained by H2O2 and Fentons degradation test during H2O2 treatment, the base-excess base-acid PBI blend membranes showed markedly less molecular weight degradation than pure PBI or sulfonated polymers, as determined by gel permeation chromatography (GPC).