Alkali resistant and conductive guanidinium-based anion-exchange membranes for alkaline polymer electrolyte fuel cells

Lin, Xiaocheng; Wu, Liang; Liu, Yanbo; Ong, Ai Lien; Poynton, Simon D.; Varcoe, John R.; Xu, Tongwen

doi:10.1016/j.jpowsour.2012.05.062

Cited by 161 publications

(107 citation statements)

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“…The properties of the membranes synthesized such as OH -conductivity, water uptake, the ion-exchange capacity (IEC), structural composition, mechanical and stability were thoroughly characterized using AC impedance technique, FT-IR spectra, SEM and TG analysis. We will demonstrate that, compared to the state of the art in AEMs as proposed above [6][7][8][9][10][11][12][13][14][15][16], the CS/EMImC-Co-EP membranes developed in this work are cost-effective, easier preparation and also perform high OH -conductivity along with the perfect alkaline stability and promising power density. EMImC-Co-EP (40% as active ingredients in H 2 O, average molecular weight M w = 400,000) were purchased from Aldrich.…”

Section: Introductionmentioning

confidence: 89%

“…However, these polymers are usually high price and complex quaternization process, and even toxic and carcinogenic when these polymers were generally artificially synthesized [13]. Moreover, despite the great progress in the development of new AEMs, few AEMs have actually been tested in real alkaline fuel cell (AFC), since they suffered unstable property at temperatures above 60 o C and at high KOH concentrations (above 1 M) [14][15][16]. Therefore, to prove the real application of AFC, an easy, low cost and green fabrication methodology with long-lifetime AFC performance needs to be developed [17,18].…”

Section: Introductionmentioning

confidence: 99%

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Novel Alkaline Anion-exchange Membranes Based on Chitosan/Ethenylmethylimidazoliumchloride Polymer with Ethenylpyrrolidone Composites for Low Temperature Polymer Electrolyte Fuel Cells

Song

Gao

et al. 2015

Electrochimica Acta

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Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Novel Alkaline Anion-exchange Membranes Based on Chitosan/Ethenylmethylimidazoliumchloride Polymer with Ethenylpyrrolidone Composites for Low Temperature Polymer Electrolyte Fuel Cells

Song

Gao

et al. 2015

Electrochimica Acta

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“…A few other promising cations evaluated include pentamethylguanidium, quaternarized diazabicylco[2.2.2]octane, N,N,N,N-tetramethyl-hexanediammonium, 1-methylimidazoliium, and tris(2,4,6-trimethoxyphenyl) phosphonium (16,(24)(25)(26)(27)(28)(29)(30)(31)(32). Most of these cations exhibit some level of alkaline stability, but comparison of the reported alkaline stability data are difficult because most of the experiments performed were carried out under different conditions (e.g., alkali concentrations and temperature) and used different characterization methods to assess stability (e.g., 1D 1 H NMR, infrared spectroscopy, change in ion-exchange capacity, and change in ion conductivity).…”

mentioning

confidence: 99%

Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes

Arges

Ramani

2013

Proc. Natl. Acad. Sci. U.S.A.

434

295

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Anion exchange membranes (AEMs) find widespread applications as an electrolyte and/or electrode binder in fuel cells, electrodialysis stacks, flow and metal-air batteries, and electrolyzers. AEMs exhibit poor stability in alkaline media; their degradation is induced by the hydroxide ion, a potent nucleophile. We have used 2D NMR techniques to investigate polymer backbone stability (as opposed to cation stability) of the AEM in alkaline media. We report the mechanism behind a peculiar, often-observed phenomenon, wherein a demonstrably stable polysulfone backbone degrades rapidly in alkaline solutions upon derivatization with alkaline stable fixed cation groups. Using COSY and heteronuclear multiple quantum correlation spectroscopy (2D NMR), we unequivocally demonstrate that the added cation group triggers degradation of the polymer backbone in alkaline via quaternary carbon hydrolysis and ether hydrolysis, leading to rapid failure. This finding challenges the existing perception that having a stable cation moiety is sufficient to yield a stable AEM and emphasizes the importance of the often ignored issue of backbone stability.alkaline fuel cells | anion exchange membrane degradation | water electrolysis | quaternary benzyl ammonium cations T here have been intensive research efforts directed toward the development of anion exchange membranes (AEMs) for solidstate alkaline fuel cells (AFCs) and water electrolyzers in recent years (1-6). These devices permit the use of non-platinum-groupmetal electrocatalysts for the oxygen reduction/evolution and hydrogen oxidation/evolution reactions (7-11). Besides their use in AFCs, AEMs are highly relevant for other electrochemical energy conversion/storage devices such as redox flow batteries, electrodialysis stacks, and metal-air batteries (6,(12)(13)(14). The renewed interest in AFCs has led to many studies directed toward improving the hydroxide ion conductivity of AEMs, a property that is inherently limited by the lower intrinsic mobility of the hydroxide ion. Approaches have included investigating new fixed cation chemistries and/or modification of the polymer electrolyte membrane network (e.g., cross-linking, spacer chain pendants, and block copolymers) (15-17). These efforts have facilitated an order of magnitude gain in hydroxide ion conductivity (roughly 10) (15,18,19). AEMs have traditionally exhibited poor chemical stability in alkaline environments. The poor alkaline stability of AEMs is an important issue that has received much less attention than AEM ionic conductivity. This issue has limited the use of AEMs in applications that involve exposure to hydroxide ions, a potent nucleophile (12). The primary AEM degradation modes involve hydroxide ion attack on the fixed cation groups of AEMs, leading to Hoffman elimination (1, 10, 11), direct nucleophilic substitution (1-3), and chemical rearrangements induced through ylide intermediate formation (2,3,(20)(21)(22). Each of these degradation mechanisms results in rapid loss of ion exchange capacity, and hence ionic co...

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“…9,11,15,16 PPO was found to be favorable in the fabrication of AEMs due to its higher alkaline stability stemming from the absence of strong electron-withdrawing groups. The polymer has been studied using solvent processing techniques earlier 17 but no study reports melt processing for fabricating membranes.…”

mentioning

confidence: 99%

“…13 PPO is a versatile aromatic polymer, which can advantageously be used as a precursor in the preparation of graft, 14 random and copolymers as studied by previous researchers for AEM applications. 9,11,15,16 PPO was found to be favorable in the fabrication of AEMs due to its higher alkaline stability stemming from the absence of strong electron-withdrawing groups. The polymer has been studied using solvent processing techniques earlier 17 but no study reports melt processing for fabricating membranes.…”

mentioning

confidence: 99%

A Highly Hydroxide Conductive, Chemically Stable Anion Exchange Membrane, Poly(2,6 dimethyl 1,4 phenylene oxide)-b-Poly(vinyl benzyl trimethyl ammonium), for Electrochemical Applications

Pandey

Sarode

Yang

et al. 2016

J. Electrochem. Soc.

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A chemically stable copolymer [poly(2,6 dimethyl 1,4 phenylene oxide)-b-poly(vinyl benzyl trimethyl ammonium)] with two ion exchange capacities, 3.2 and 2.9 meq g −1 , was prepared as anion exchange membranes (AEM-3.2 and AEM-2.9). These materials showed high OH − conductivities of 138 mS.cm −1 and 106 mS.cm −1 , for AEM-3.2 and AEM-2.9 respectively, at 60 • C, and 95% RH. The OH − conductivity = 45 mS.cm −1 for AEM-3.2 at 60% RH and 60 • C in the absence of CO 2 . Amongst the ions studied, only OH − is fully dissociated at high RH. The lower E a = 10-13 kJ.mol −1 for OH − compared to F − ∼ 20 kJ.mol −1 in conductivity measurements, and of H 2 O from self-diffusion coefficients suggests the presence of a Grotthuss hopping transport mechanism in OH − transport. PGSE-NMR of H 2 O and F − show that the membranes have low tortuosity, 1.8 and 1.2, and high water self-diffusion coefficients, 0.66 and 0.26 × 10 −5 cm 2 .s −1 , for AEM-3.2 and AEM-2.9 respectively. SAXS and TEM show that the membrane has several different sized water environments, ca. 62 nm, 20 nm, and 3.5 nm. The low water uptake, λ = 9-12, reduced swelling, and high OH − conductivity, with no chemical degradation over two weeks, suggests that the membrane is a strong candidate for electrochemical applications. Anion Exchange membranes (AEMs) have been proposed as the separator in electrochemical energy conversion devices such as fuel cells, electrolyzers, or redox flow cells.1 As catalysis is more facile in base, the use of an AEM should allow the use of non-precious metal catalysts and also the oxidation or production of complex fuels beyond hydrogen.2 Significant work has been done in the past decade in this area and many new membranes have been developed with improved mechanical, chemical, and transport properties. An ideal AEM should have high ionic conductivity to achieve practical power densities, 3 good chemical stability to operate under an alkaline environment, 4 and excellent thermal and mechanical properties to survive transient operating conditions. 1,5 Intensive efforts have been made to study AEMs with aromatic backbones such as polysulfone, 6-8 poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), 9-11 and poly(ether ether ketone) 12 due to their high thermal and chemical stability, good mechanical properties, and outstanding film forming ability.13 PPO is a versatile aromatic polymer, which can advantageously be used as a precursor in the preparation of graft, 14 random and copolymers as studied by previous researchers for AEM applications. 9,11,15,16 PPO was found to be favorable in the fabrication of AEMs due to its higher alkaline stability stemming from the absence of strong electron-withdrawing groups. The polymer has been studied using solvent processing techniques earlier 17 but no study reports melt processing for fabricating membranes.Polymer -water/ion interactions are important when it comes to understanding performance of anion exchange membranes.18 Inherently hydroxide (OH − ) transport (5.273 × 10 −5 cm 2 /sec) is ∼50% slower tha...

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Alkali resistant and conductive guanidinium-based anion-exchange membranes for alkaline polymer electrolyte fuel cells

Cited by 161 publications

References 37 publications

Novel Alkaline Anion-exchange Membranes Based on Chitosan/Ethenylmethylimidazoliumchloride Polymer with Ethenylpyrrolidone Composites for Low Temperature Polymer Electrolyte Fuel Cells

Novel Alkaline Anion-exchange Membranes Based on Chitosan/Ethenylmethylimidazoliumchloride Polymer with Ethenylpyrrolidone Composites for Low Temperature Polymer Electrolyte Fuel Cells

Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes

A Highly Hydroxide Conductive, Chemically Stable Anion Exchange Membrane, Poly(2,6 dimethyl 1,4 phenylene oxide)-b-Poly(vinyl benzyl trimethyl ammonium), for Electrochemical Applications

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