Anion exchange membranes (AEMs) are of high interest for a number of electrochemical device applications including fuel cells, electrolyzers, and flow batteries. Perfluorinated sulfonic acid polymers have been the standard polymer used in the much more established area of proton exchange membrane based devices due to specific advantageous attributes including chemical stability, high conductivity, high water mobility, and the ability to create high performance electrodes. These attributes would make for desirable AEMs, but synthesizing perfluorinated AEMs has been limited and has significant challenges. Here, we report our efforts to develop novel synthesis routes to sulfonamide-linked alkyl ammonium perfluorinated AEMs. We have demonstrated the ability to achieve both high levels of ion exchange and membrane conductivity. We have achieved improved durability by extending the length of the alkyl tether from 3 to 6 carbons, and we have demonstrated the ability to process these polymers into membranes, ionomer solutions/dispersions, and fuel cells with reasonable performance.

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.

Anion Exchange Membrane Fuel Cells (AEMFCs) have experienced a significant rise in attention in recent years, largely motivated by the potential to overcome the costs that have plateaued for proton exchange membrane fuel cells. However, despite significant advances in power generation, membrane conductivity, membrane stability, and catalyst activity, the vast majority of high performing AEMFCs are fabricated with a high PGM loading (0.4-0.8 mg cm −2 ). This work demonstrates an electrode fabrication method that reduces the anode catalyst loading by 85% while still achieving performance ca. 1 W cm −2 -accomplished by designing a multilayered electrode comprised of an optimized ionomer:carbon:PGM ratio catalyst layer coupled with a hydrophobic microporous layer. If paired with a high-performing PGM-free cathode, this new anode shows the potential to meet existing DOE PGM loading and performance targets. Anion exchange membrane fuel cells (AEMFCs) have received significant attention in recent years as a potentially lower cost electrochemical energy conversion device than proton exchange membrane fuel cells (PEMFCs).1-3 There have been several major advancements in the materials and operational understanding of the AEMFC in the past few years, which have allowed AEMFCs to close the performance gap with PEMFCs. Improvements in membrane stability and conductivity have been at the forefront of the material improvements, with conductivities rivaling Nafion, 4-10 and an increasing number of membranes showing stability in highly alkaline environments (up to 2 M KOH at 80• C) for 100s or even 1000s of hours. [8][9][10][11][12][13] Additionally, catalyst layer engineering that allows for improved water management, both on the macro-scale 14 and on the micro-scale, 15 has led to AEMFCs that are able to achieve peak power densities nearing 2 W cm −2 and demonstrate operational stability exceeding 500 hours. These are crucial steps toward the realization of commercially viable AEMFCs; however, there remain additional hurdles to overcome, specifically AEMFCs with low platinum group metal (PGM) loadings that are able to not only achieve high power densities but sustain them over long term operation. 12In order to reduce the PGM loading in operating AEMFCs, there will need to be at least some development of non-PGM catalysts. Due to differences in the water dissociation behavior in alkaline media, 16 the kinetics for the hydrogen oxidation reaction are hindered in alkaline media compared to acid media. 17 The opposite is true of the oxygen reduction reaction at the cathode; therefore, it is more likely that the AEMFC will see a high performance PGM-free cathode electrode. Indeed, some very promising catalysts have already been identified. 3,[18][19][20][21][22][23] However, at the AEMFC anode, it is very likely (akin to the PEMFC cathode) that it will be difficult to move completely away from PGM-based catalysts, though this is presently an active area for research.24,25 Therefore, it is important for researchers in the field to ...

Recent advances in highly conductive and base stable anion exchange membrane chemistries have enabled the widespread fabrication of alkaline membrane fuel cells (AMFC).(1) A significant limitation to AMFC commercialization, however, is the sluggish hydrogen oxidation reaction (HOR) kinetics of current anode catalysts. Much work has been performed to understand the fundamental limitations of HOR in an alkaline environment(2, 3) and to study the HOR in an alkaline membrane electrode assembly (MEA)(4). It is of significant interest to the AMFC community to continue studying the HOR reaction to understand the in-situsources of voltage losses, and to develop a diagnostic tool to test the kinetics of new/alternative catalysts in an alkaline MEA. In this study, a series of MEAs were fabricated where the membrane (Tokuyama A201) and binder polymer (Tokuyama AS-4) are held constant, but where the catalyst content and composition are varied. A hydrogen pump technique was utilized where an external current source drives HOR on one electrode of the MEA and hydrogen evolution (HER) on the other. It should be noted that there is no traditional reference electrode in this system, as each electrode reaction contributes a significant overpotential. The polarization curves acquired from the hydrogen pump are analyzed for sources of voltage losses including mass transport, ohmic, and kinetic overpotentials. The causes of such losses will be discussed and presented with insight gained from modeling and experimental work. Exchange current densities of HOR and HER for both platinum on carbon and platinum ruthenium on carbon will also be presented, where all data was taken in an in-situalkaline MEA. The potential for hydrogen pump as a diagnostic method for future anode catalyst testing will also be included. Figure 1. HOR and HER overpotentials for Pt/C electrodes between 0.119 and 0.8 mg/cm2 loading as a function of current density per Pt site, with the corresponding Butler-Volmer model fit 1. J. R. Varcoe, P. Atanassov, D. R. Dekel, A. M. Herring, M. A. Hickner, P. A. Kohl, A. R. Kucernak, W. E. Mustain, K. Nijmeijer, K. Scott, T. Xu and L. Zhuang, Energy & Environmental Science(2014). 2. J. Durst, A. Siebel, C. Simon, F. Hasche, J. Herranz and H. A. Gasteiger, Energy & Environmental Science, 7, 2255 (2014). 3. Y. Wang, G. Wang, G. Li, B. Huang, J. Pan, Q. Liu, J. Han, L. Xiao, J. Lu and L. Zhuang, Energy & Environmental Science, 8, 177 (2015). 4. M. D. Woodroof, J. A. Wittkopf, S. Gu and Y. S. Yan, Electrochemistry Communications, 61, 57 (2015). Figure 1

Anionic exchange membrane fuel cell is a promising new technology which potentially meets the challenges faced by other low-temperature fuel cells like Proton-exchange membranes. Anionic exchange membrane can be operated with non-noble catalyst. To design a robust material which is hydroxide conductive, chemically stable and mechanically strong is the biggest challenge to make this technology commercial. This research focuses on the characterization of a novel anionic exchange membrane with PTFE backbone. The experimental ion-exchange capacity of this polymer is 0.9 mmol/gm. The conductivity of this membrane was measured in its chloride form. We observed the highest value of 0.039 S/cm conductivity at 80 0C and 95%RH. The polymer also shows water uptake of 11 % and λ value of 6.8 at 60 0C and 95% RH. The small-angle x-ray scattering analysis of this membrane shows the polymer’s ionomer peak and we understand that the swelling of the polymer is higher at higher temperature. From this analysis, this material can be expected to exhibit higher hydroxide conductivities and good mechanical stability and hence this polymer is a promising candidate for anionic exchange membranes. Keywords: Anionic exchange membrane, PTFE backbone Figure 1