(Invited) Molecular Engineering of Ion-Conducting Polymer Membranes for Electrochemical Energy Storage and Conversion Technologies

Abstract

Anion exchange membranes (AEMs) based on hydroxide-conducting polymers are a key component for anion-based electrochemical energy technology such as fuel cells, electrolyzers, and advanced batteries. Although these alkaline electrochemical technologies offer a promising alternative to acidic proton exchange membrane electrochemical devices, the access to chemically stable, mechanically durable, high-performing polymer electrolyte materials has been bottleneck to advance electrochemical technologies for hydrogen and other green chemicals until now. Despite vigorous research of AEM polymer design, examples of high-performance polymers with good alkaline stability at an elevated temperature are uncommon. Traditional aromatic polymers used in AEM applications contain a heteroatomic backbone linkage which is prone to degradation via nucleophilic attack by hydroxide ion. In this presentation, I will highlight recent progress at the Bae group of Rensselaer Polytechnic Institute in the development of advanced hydroxide-conducting polymers and membranes for AEM technology applications. We have developed a number of synthetic methodologies that produce polymer design made of all C−C bond backbones and a flexible chain-tethered quaternary ammonium group and that provide an effective solution to the problem of alkaline stability. The advantage of good solvent processability, synthetic versatility, and convenient scalability of the reaction process has generated considerable interest of these polymers, and they are considered leading candidates for commercial standard AEM. AEM fuel cells, electrolyzer, and redox flow battery tests of some of the developed polymer membranes showed excellent performance, suggesting that this new class of AEMs open a new avenue to electrochemical devices with real-world applications.