Mechanism of Tetraalkylammonium Headgroup Degradation in Alkaline Fuel Cell Membranes

Chempath, Shaji; Einsla, Brian R.; Pratt, Lawrence R.; Macomber, Clay S.; Boncella, James M.; Rau, J.; Pivovar, Bryan S.

doi:10.1021/jp7115577

Cited by 355 publications

(283 citation statements)

References 11 publications

Supporting

Mentioning

270

Contrasting

Unclassified

Order By: Relevance

“…This poor stability in alkaline conditions derives from the strong nucleophilicity of the OHanions, which induces displacement (S N2 , or via ylide intermediates) and Hofmann elimination reactions (predominantly the latter when ß-hydrogens present). [18][19][20][21] With the aim of obtaining AAEMs with enhanced stability, alternative cationic head-groups including guanidinium, 22,23 stabilized phosphonium, 24,25 and imidazolium, [26][27][28][29][30] have been recently investigated. Zhang and co-workers reported a new class of AAEMs containing guanidinium head-groups, which maintained ionic conductivity even after immersion in aqueous NaOH (1 mol dm -3 ) for a week at room temperature; this suggested good alkaline stability.…”

Section: Introductionmentioning

confidence: 99%

Development of imidazolium-type alkaline anion exchange membranes for fuel cell application

Jin

Varcoe

et al. 2012

Journal of Membrane Science

213

146

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Development of imidazolium-type alkaline anion exchange membranes for fuel cell application

Jin

Varcoe

et al. 2012

Journal of Membrane Science

213

146

View full text Add to dashboard Cite

“…In general, the degradation pathways for the tetra-alkyl quaternary ammonium cations include Hofmann degradation, E 2 -hydrogen elimination, SN 2 direct nucleophilic substitution, and nitrogen ylide formation. 39,40 These mechanisms have been verified in ex-situ testing of model compounds and materials, but in-situ degradation assessment in operating cells is still ongoing. Clearly, one of the goals for furthering AEMFC technology is to develop new AEMs that not only have high ionic conductivity but also exhibit improved chemical and mechanical stability in alkaline fuel cell conditions.…”

mentioning

confidence: 96%

Characterization and Chemical Stability of Anion Exchange Membranes Cross-Linked with Polar Electron-Donating Linkers

Amel

Smedley

Dekel

et al. 2015

J. Electrochem. Soc.

View full text Add to dashboard Cite

The effect of the cross-linker chemical structure on the properties and chemical stability of anion exchange membrane is the focus of this study. Two different cross-linkers were investigated, one with linear hexyl chain between crosslinking sites, and the other, ether in the center of the alkyl linker. These two cross-linkers have a fundamental difference in their polarity and hydrophilicity. The ether-containing cross-linker is more polar and therefore will improve membrane's water uptake and conductivity. Swelling and conductivity measurements were performed at various temperatures for both types of samples. While water uptake and conductivity were found to be higher for the ether-based cross-linker, degradation measurements indicated that the membrane that is cross-linked with electron-rich linker degraded in hydroxide faster than the alkyl linker at temperature of 60 • Fuel cell technology has been recognized as a promising clean energy conversion technology in next-generation energy systems. Fuel cells have been undergoing revolutionary developments in the last few decades. [1][2][3] Among the different types of fuel cell systems, proton exchange membrane fuel cells (PEMFC) are the most investigated and developed for low-temperature operation in portable and automotive environments. 4,5 Although there has been great progress in improving the performance and lifetime of PEMFCs and large-scale commercial applications are on the horizon, the largest barriers to wide-spread fuel cell technology are materials availability and cost. Among the limitations of PEMFCs, the dependence on noble metal catalysts is a critical concern. For example, the use of Nafion, the state of the art acidic membrane, generally allows only platinum group metals to be used as stable catalysts for long-term use, thus considerably increasing the cost of PEMFC technology. To overcome the requirement of precious metal catalysts, anion exchange membrane fuel cell (AEMFC) technology has begun to attract recent attention. This new effort focused on AEMFCs is due to several potential advantages that anion exchange membranes hold over their acidic membrane counterparts. In AEMFCs, oxygen reduction kinetics is improved in the high pH environment of the membrane and the use of non-precious metals as electrocatalysts greatly reduces the cost of fuel cell devices.6-8 A highlyconductive, chemically robust anion exchange membrane (AEM) is a crucial component of the fuel cell as it acts as a barrier between the fuel and oxidant streams while simultaneously transporting anions from the cathode to the anode. and imidazoilum 36-38 groups. It is known that the quaternary ammonium moiety is susceptible to hydroxide attack, resulting in degradation of alkaline membrane at elevated temperature under alkaline conditions, but clear pathways for degradation of polymer backbones and other functional groups of AEMs including non-ammonium cations has not been extensively pursued. In general, the degradation pathways for the tetra-alkyl quaternary ammonium cations...

show abstract

“…131 High pressure surpasses the water loss inside the membrane thus stops membrane degradation occurring. 125,132 The methods to improve the water retention of AEM are important for future development. Self-humidification developed for the Nafion membrane 133 can apply to AEMs.…”

Section: Further Development Of Anion Exchange Membranes (Aems)mentioning

confidence: 99%

Direct oxidation alkaline fuelcells: from materials to systems

Wang

Krewer

et al. 2012

Energy Environ. Sci.

237

153

View full text Add to dashboard Cite

Direct oxidation alkaline fuel cells (DOAFCs) possess particular advantages on the possibility of employing low cost non-noble metal catalysts. A wide range of fuels can be used due to superior reaction kinetics in alkaline media. The development of DOAFCs was hindered by the carbonation of electrolyte due to the presence of CO 2 . The application of the anion exchange membrane (AEM) provides the possibility of reducing the effect of carbonation and fuel crossover which is an issue in the proton exchange membrane fuel cells (PEMFCs). The latest developments in alkaline fuel cells are examined in this paper, considering different types of fuels, novel catalysts and anion exchange membranes. Moreover, alkaline fuel cell systems and configurations are studied, particularly the new designs for portable or microelectronic devices. Further development of DOAFCs will rely on novel AEMs with good ionic conductivity and stability, low cost non-Pt catalysts with high activity and good stability for various fuels and oxidant. We envisage that DOAFCs will play a major role in energy research and applications in the near future.

show abstract

Mechanism of Tetraalkylammonium Headgroup Degradation in Alkaline Fuel Cell Membranes

Cited by 355 publications

References 11 publications

Development of imidazolium-type alkaline anion exchange membranes for fuel cell application

Development of imidazolium-type alkaline anion exchange membranes for fuel cell application

Characterization and Chemical Stability of Anion Exchange Membranes Cross-Linked with Polar Electron-Donating Linkers

Direct oxidation alkaline fuelcells: from materials to systems

Contact Info

Product

Resources

About