Molecular Design Aspect of Anion Exchange Polymer Electrolytes

Abstract

Anion exchange polymer electrolytes play an important role both in separator (membrane) and in electrode binder (ionomer). Depending on their role, polymer electrolytes must possess certain properties which are essential to improve the alkaline membrane fuel cell performance & durability. In this study, we will present molecular design aspects of anion exchange polymer electrolytes for the use of membranes and ionomeric binders. In-depth studies on chemical degradation of polyaromatic anion exchange membranes and importance of perfluoirnated structure in the catalyst layer will be discussed in addition to the effects of cation type on chemical degradation and interaction with electro-catalysis.

Best Practices for Investigating Anion Exchange Membrane Suitability for Alkaline Electrochemical Devices: Case Study Using Quaternary Ammonium Poly(2,6-dimethyl 1,4-phenylene)oxide Anion Exchange Membranes

“…Since that early review, reported SAFC performance (maximum power density) with hydrogen and oxygen using platinum electrocatalysts has now exceeded 300 mW cm −2 8-11 in the peer-review literature (up to 550 mW cm −2 ) 11 and range from between 500 mW cm −2 (using non-platinum electrocatalysts) to 730 mW cm −2 (using platinum electrocatalysts) in the non-peerreviewed literature. 12,13 Nakashima and co-workers have also shown fuel cell performance of 256 mW cm −2 (with platinum electrocatalysts) with hydrogen and air using an alkaline membrane and electrode. 14 Additionally, reports by Zhang and co-workers and Yan and co-workers have shown fuel cell performance with hydrogen and oxygen of up to 70 mW cm −2 with no platinum group metal catalysts used.…”

“…There have only been a handful of reports investigating the stability of the AEM during fuel cell operation. Kim and co-workers, 12 Gottesfeld and co-workers, 13 and Luo et al 32 have all performed constant current or voltage hold tests and monitored changes in the drop of voltage or current, respectively, with time. Kim and co-workers showed that the drop in cell current correlated with an increase in the high frequency resistance of the cell.…”

“…Kim and co-workers showed that the drop in cell current correlated with an increase in the high frequency resistance of the cell. 12 However, to date there are no reports attempting to connect ex-situ AEM alkaline stability experiments (which evaluate changes in ionic conductivity, IEC, mechanical properties, and NMR spectra upon exposure to alkali) to the changes in polarization and high frequency resistance observed in-situ during fuel cell operation. In this paper, we have adopted an all-encompassing strategy to assess the alkaline stability of poly (2,6dimethyl 1,4-phenylene) oxide (PPO) AEMs (containing quaternary benzyl ammonium groups) for alkaline fuel cells.…”