Block Copolymers for Alkaline Fuel Cell Membrane Materials
COLORADO SCHOOL OF MINES GOLDEN
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Alkaline fuel cells AFCs using anion exchange membranes AEMs as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal e.g. nickel, silver catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte e.g. aqueous potassium hydroxide, which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems blend, block, grafted, and crosslinked polymers in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of polyvinylbenzyl chloride-bpolystyrene PVBC-b-PS diblock copolymer, prepared by nitroxide mediated polymerization NMP, with poly2,6- dimethyl-1,4-phenylene oxide PPO or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity up to 94 mScm at 80 C while excellent mechanical properties strain up to 205 of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol mPEG as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC-b-PS.
- Polymer Chemistry
- Electrochemical Energy Storage