Abstract
Alkaline polyelectrolyte fuel cell now receives growing attention as a promising candidate to serve as the next generation energy-generating device by enabling the use of non-precious metal catalysts (silver, cobalt, nickel et al.). However, the development and application of alkaline polyelectrolyte fuel cell is still blocked by the poor hydroxide conductivity of anion exchange membranes. In order to solve this problem, we demonstrate a methodology for the preparation of highly OH− conductive anion exchange polyelectrolytes with good alkaline tolerance and excellent dimensional stability. Polymer backbones were grafted with flexible aliphatic chains containing two or three quaternized ammonium groups. The highly flexible and hydrophilic multi-functionalized side chains prefer to aggregate together to facilitate the formation of well-defined hydrophilic-hydrophobic microphase separation, which is crucial for the superior OH− conductivity of 69 mS/cm at room temperature. Besides, the as-prepared AEMs also exhibit excellent alkaline tolerance as well as improved dimensional stability due to their carefully designed polymer architecture, which provide new directions to pursue high performance AEMs and are promising to serve as a candidate for fuel cell technology.
Highlights
Fuel cell technology is recognized as one of the most promising candidate to cope with the impending energy crisis
On the other hand, compared with Nafion, the state of art proton exchange membrane which demonstrates excellent proton conductivity attributing to its particular comb-shaped polymer architecture and the strong acidity of sulfonic acid groups, poor micro phase separation ability and weak basicity of quaternary ammonium hydroxide are considered as the key problems for improving the OH− conductivity of anion exchange membranes (AEMs)
Numerous strategies have been applied to improve the hydroxide conductivity of AEMs which can be mainly classified into two categories: synthesis of new anion conductive groups and design of polymer architecture[2,3] for tuning of ordered micro-phase segregations
Summary
Fuel cell technology is recognized as one of the most promising candidate to cope with the impending energy crisis. On the other hand, compared with Nafion , the state of art proton exchange membrane which demonstrates excellent proton conductivity attributing to its particular comb-shaped polymer architecture and the strong acidity of sulfonic acid groups, poor micro phase separation ability and weak basicity of quaternary ammonium hydroxide are considered as the key problems for improving the OH− conductivity of anion exchange membranes (AEMs). QA groups based anion exchange membranes are prepared either by chloromethylation or bromomethylation followed by quaternization, which leads to AEMs with quaternary ammonium groups closely attached to the polymer backbones This kind of anion exchange membranes usually show low hydroxide conductivity ascribing to their less ordered self-assembly morphologies as previously reported[8]. As an experiential verification of this proposal, side chain type anion exchange membranes were successfully developed in our lab via poly-condensation of pre-quaternized monomers for morphology tuning purpose, and as-expected good microphase separation and high OH− conductivity were observed[12]
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