Hydroxide based decomposition pathways of alkyltrimethylammonium cations

Edson, Joseph B.; Macomber, Clay S.; Pivovar, Bryan S.; Boncella, James M.

doi:10.1016/j.memsci.2012.01.025

Cited by 127 publications

(97 citation statements)

References 29 publications

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“…Figure shows the change of IEC of quaternized PSf membranes after immersing in an aquous KOH solution at 60°C. As expected IEC of TMA or DABCO quaternized PSf are not much affected by the alkaline environment as their ammonium groups do not contain β ‐ H atoms . On the other hand, IEC of MI quaternized PSf decreases fast, probably as a result of an imidazolium ring‐opening mechanism .…”

Section: Resultssupporting

confidence: 65%

Polysulfone‐based anion exchange polymers for catalyst binders in alkaline electrolyzers

Schauer

Žitka

Pientka

et al. 2015

J of Applied Polymer Sci

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The preparation of quaternized bisphenol A polysulfone (PSf) by chloromethylation and quaternization with trimethylamine (TMA), 1,4-diazabicyclo[2.2.2]octane (DABCO), 1-methylimidazole (MI), or 1,2-dimethylimidazole (DMI) is described. While the ion-exchange capacities (IECs) of MI or DMI quaternized PSf significantly decrease in concentrated KOH solutions at 608C, the IECs of TMA or DABCO quaternized PSf are not much affected, but the membranes of these polymers become brittle. TMA quaternized PSf (IEC 5 1.21 meq/g; IC 5 2.45 S/m) and DABCO quaternized PSf (IEC 5 1.09 meq/g; IC 5 2.49 S/m) were used to bind a NiCo 2 O 4 spinel electrocatalyst on the anode of Ni foam. Both the quaternized PSfs were quite effective in water electrolysis when used as binders, but not more effective than PTFE when rear sides of electrodes were fed with 10 wt % aqueous KOH solution. For long-term electrolysis, binders based on more stable anion-conductive polymers should be developed. V C 2015 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2015, 132, 42581.

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Section: Resultssupporting

confidence: 65%

Polysulfone‐based anion exchange polymers for catalyst binders in alkaline electrolyzers

Schauer

Žitka

Pientka

et al. 2015

J of Applied Polymer Sci

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“…The alkali environment of an AEM exposes the membrane to hydroxide ions that can attack the ionic group tethered to the polymer or the polymer backbone itself [3]. A significant amount of ongoing research is directed towards identifying alkali stable polymer chemistries and novel cation functionalities for chemically robust AEMs [7][8][9][10]. Transport of hydroxide, or other anions, in an AEM is inherently slower than protons in PEMs, and to compensate for this factor, ionic concentration is often increased in AEMs [1].…”

Section: Introductionmentioning

confidence: 99%

Effect of hydration on the mechanical properties and ion conduction in a polyethylene-b-poly(vinylbenzyl trimethylammonium) anion exchange membrane

Vandiver

Caire

Pandey

et al. 2016

Journal of Membrane Science

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a b s t r a c tAnion exchange membranes (AEM) are promising solid polymer electrolytes utilized in alkali fuel cells and electrochemical energy conversion devices. AEMs must efficiently conduct ions while maintaining chemical and mechanical stability under a range of operating conditions. The ionic nature of AEMs leads to stiff and brittle membranes under dry conditions while at higher hydrations, water sorption causes significant softening and weakening of the membrane. In this work, a new polyethylene-b-poly(vinylbenzyl trimethylammonium) polymer (70 kg/mol) was cast into large (300 cm 2 ), thin (12 7 3 μm) membranes. These membranes exhibited improved elasticity over previously tested AEMs, minimal dimensional swelling, and moderate ionic conductivity (5 7 2 mS/cm at 50°C, 95% RH in the bromide form). Extensional testing indicated a 95% reduction in Young's modulus between dry and hydrated states. Further investigation of the complex modulus as a function of hydration, by dynamic mechanical analysis, revealed a sharp decrease in modulus between dry and hydrated states. Mechanical softening was reversible, but the location of the transition displayed hysteresis between humidification and dehumidification. Conductivity increased after membrane softening; suggesting bulk mechanical properties can identify the hydration level required for improved ion transport. Understanding the relationship between ion conduction and mechanical properties will help guide AEM development and identify operating conditions for sustained performance.

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“…6,11,12 Hydroxide transport is inherently slower than proton transport, to compensate the concentration of ion groups is often increased in AEMs. Increasing cation concentration in the polymer can significantly increase water uptake, causing dimensional swelling of the membrane and loss of mechanical integrity.…”

mentioning

confidence: 99%

Mechanical Performance of Polyiosoprene Copolymer Anion Exchange Membranes by Varying Crosslinking Methods

Vandiver

Caire

Ertem

et al. 2015

J. Electrochem. Soc.

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Anion exchange membranes (AEM) are polymer electrolytes that facilitate ion transport in alkaline fuel cells and electrochemical devices. Fabrication of mechanically durable AEMs with high ionic conductivity is a challenge. Here, a copolymer of isoprene and vinylbenzyl trimethylammonium and a terpolymer of isoprene, vinylbenzyl trimethylammonium and styrene were crosslinked by various methods, and properties, including conductivity and mechanical strength, were investigated at dry and saturated conditions. Polymer chemistry and degree of crosslinking significantly influenced conductivity, swelling, and mechanical properties. The terpolymer had a higher proportion of vinylbenzyl trimethylammonium units increasing the ion exchange capacity (IEC), but membranes could still be rendered insoluble by crosslinking. The higher IEC of the terpolymer resulted in higher chloride conductivity, 20-75 mS/cm at 50 • C and 95%RH, compared to 4-17 mS/cm for the copolymer at the same conditions. At dry conditions films were stiff, having Young's moduli between 100-740 MPa, but hydration caused severe softening, reducing moduli by 1-2 orders of magnitude. The severe softening effect of hydration was confirmed by dynamic mechanical analysis. The AEMs studied did not have adequate mechanical durability at hydrated conditions, additional work is needed to determine polymer chemistries and crosslinking methods that will produce robust AEMs for long-term use in fuel cells and electrochemical devices. Fuel cells are attractive energy conversion devices that utilize hydrogen to produce electrical energy for stationary and transportation applications, with the by-product being water.1,2 Electrolyzers utilize a similar principle to produce hydrogen from water using electrical energy. Fuel cells and electrolyzers both utilize a polymer electrolyte membrane to separate the catalyst layers and efficiently transport ions, while limiting crossover of other species.1,3 Proton exchange membranes (PEM), specifically perfluorosulfonic acid polymers such as Nafion, have been utilized almost exclusively for current fuel cells, owing to their high proton conductivity and suitable chemical and mechanical stability. 4,5 While PEM fuel cells have been widely researched and developed over the last few decades, anion exchange membrane (AEM) fuel cells offer potential advantages over PEMs. [6][7][8][9][10] The alkali nature of an AEM fuel cell allows redox reactions with nonplatinum catalysts and improves oxygen reduction kinetics. 6,9,10 On going research seeks to develop robust, well performing AEMs for use in fuel cells, electrolyzers, and other electrochemical devices.Anion exchange membranes must have a high ionic conductivity and be chemically and mechanically stable over the life-time of the fuel cell.6,9,10 Chemical stability is a concern in AEMs as hydroxide ions present in the membrane have the potential to degrade the polymer backbone and cation functionalities. 6,11,12 Hydroxide transport is inherently slower than proton transport, to compensate...

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Hydroxide based decomposition pathways of alkyltrimethylammonium cations

Cited by 127 publications

References 29 publications

Polysulfone‐based anion exchange polymers for catalyst binders in alkaline electrolyzers

Polysulfone‐based anion exchange polymers for catalyst binders in alkaline electrolyzers

Effect of hydration on the mechanical properties and ion conduction in a polyethylene-b-poly(vinylbenzyl trimethylammonium) anion exchange membrane

Mechanical Performance of Polyiosoprene Copolymer Anion Exchange Membranes by Varying Crosslinking Methods

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