Anion-exchange membranes (AEM) containing saturated-heterocyclic benzyl-quaternary ammonium (QA) groups synthesised by radiation-grafting onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films are reported. The relative properties of these AEMs are compared with the benchmark radiation-grafted ETFE-g-poly(vinylbenzyltrimethylammonium) AEM. Two AEMs containing heterocyclic-QA head groups were down-selected with higher relative stabilities in aqueous KOH (1 mol dm-3) at 80°C (compared to the benchmark): these 100 μm thick (fully hydrated) ETFE-g-poly(vinylbenzyl-Nmethylpiperidinium)- and ETFE-g-poly(vinylbenzyl-N-methylpyrrolidinium)-based AEMs had as-synthesised ion-exchange capacities (IEC) of 1.64 and 1.66 mmol g-1, respectively, which reduced to 1.36 mmol dm-3 (ca. 17 – 18% loss of IEC) after alkali ageing (the benchmark AEM showed 30% loss of IEC under the same conditions). These down-selected AEMs exhibited as-synthesised Cl- ion conductivities of 49 and 52 mS cm-1, respectively, at 90°C in a 95% relative humidity atmosphere, while the OH- forms exhibited conductivities of 138 and 159 mS cm-1, respectively, at 80°C in a 95% relative humidity atmosphere. The ETFE-g-poly(vinylbenzyl-N-methylpyrrolidinium)-based AEM produced the highest performances when tested as catalyst coated membranes in H2/O2 alkaline polymer electrolyte fuel cells at 60°C with PtRu/C anodes, Pt/C cathodes, and a polysulfone ionomer: the 100 μm thick variant (synthesised from 50 μm thick ETFE) yielded peak power densities of 800 and 630 mW cm-2 (with and without 0.1 MPa back pressurisation, respectively), while a 52 μm thick variant (synthesised from 25 μm thick ETFE) yielded 980 and 800 mW cm-2 under the same conditions. From these results, we make the recommendation that developers of AEMs, especially pendent benzyl-QA types, should consider the benzyl-Nmethylpyrrolidinium head-group as an improvement to the current de facto benchmark benzyltrimethylammonium headgroup

For AEMFC, OHform of membrane reacts with CO2 when exposed to air leading to loss in conductivity. Very few attempts have been made to understand the reaction kinetics, morphological properties and equilibrium concentrations at different environmental conditions. We have attempted to study the CO2 kinetics and its effect on water-uptake (or lambda) and morphology(SAXS) when the OHform of membrane is exposed to air which has approx. 400 ppm of CO2. The kinetics was studied by exposing the membrane to controlled environment and titrating it using Warder and Winkler titration methods. From transient SAXS analysis we observe the intensity of ionomer feature of membrane spectrum dropping over time. Also the d-spacing at equilibrium is lower than the initial value. Ultimately we want to understand the effect of CO2 on membrane from every aspect and possibly help us think about strategies to mitigate the problem.

Ex situ physico-chemical, electrochemical, and morphological analysis sheds light on the CO2 limitation of ambient air anion exchange membrane fuel cells.