Issue 12, 2016

High performance aliphatic-heterocyclic benzyl-quaternary ammonium radiation-grafted anion-exchange membranes


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-N-methylpiperidinium)- 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-N-methylpyrrolidinium head-group as an improvement to the current de facto benchmark benzyltrimethylammonium head-group.

Graphical abstract: High performance aliphatic-heterocyclic benzyl-quaternary ammonium radiation-grafted anion-exchange membranes

Supplementary files

Article information

Article type
07 Jul 2016
03 Oct 2016
First published
03 Oct 2016
This article is Open Access
Creative Commons BY license

Energy Environ. Sci., 2016,9, 3724-3735

High performance aliphatic-heterocyclic benzyl-quaternary ammonium radiation-grafted anion-exchange membranes

J. Ponce-González, D. K. Whelligan, L. Wang, R. Bance-Soualhi, Y. Wang, Y. Peng, H. Peng, D. C. Apperley, H. N. Sarode, T. P. Pandey, A. G. Divekar, S. Seifert, A. M. Herring, L. Zhuang and J. R. Varcoe, Energy Environ. Sci., 2016, 9, 3724 DOI: 10.1039/C6EE01958G

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity