Synthesis and Alkaline Stability of Solubilized Anion Exchange Membrane Binders Based on Poly(phenylene oxide) Functionalized with Quaternary Ammonium Groups via a Hexyl Spacer

Parrondo, Javier; Jung, Min-suk; Wang, Zhongyang; Arges, Christopher G.; Ramani, Vijay

doi:10.1149/2.0891510jes

Cited by 47 publications

(74 citation statements)

References 44 publications

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“…54,56 The ultimate strength and the elongation at break are very important in applications where the membranes are to be assembled in electrochemical cell, wherein they are subjected to stresses that could result in deformation and mechanical failure. It is interesting to note that the mechanical properties of tri-block copolymers (e.g.…”

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confidence: 99%

Anion Exchange Membranes Based on Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene Triblock Copolymers: Cation Stability and Fuel Cell Performance

Wang

Parrondo

Ramani

2017

J. Electrochem. Soc.

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A series of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS)-based anion exchange membranes (AEMs) were synthesized via chloromethylation of SEBS followed by quaternization with trimethylamine (TMA). SEBS-based AEMs functionalized with TMA + cations exhibited a hydroxide ion conductivity of 136 mS/cm at 70 • C. This membrane exhibited a phaseseparated morphology with wide and interconnected ionic channels as observed by atomic force microscopy. Poly (phenylene oxide) (PPO)-based AEMs with quaternary benzyl-trimethylammonium (TMA + ) and quaternary benzyl-tris(2,4,6-trimethoxyphenyl) phosphonium (TTMPP + ) and PPO-based AEMs with hexyl pendant chains were also synthesized and evaluated as binders in AMFC electrodes. PPO-based AEMs functionalized with TTMPP + demonstrated the best ex situ alkaline stability, losing only 9% of their ion-exchange-capacity after 30 days in 1M KOH (at 60 • C). The best in situ stability was achieved by SEBS-based MEAs (as membrane and as binder in the electrodes); The peak power density dropped approx. 35% after holding the cell at a constant voltage of 0.55V for 12 hours. Fuel cell performance with SEBS-based AEMs resulted in peak power densities of 300 mW/cm 2 at 70 • C. Anion exchange membranes (AEMs) are a promising technology for alkaline membrane fuel cells (AMFCs), 1-6 redox flow batteries (RFBs), 7-13 alkaline water electrolyzers (AWEs) [14][15][16] and reverse electrodialysis (RED) cells. 17,18 The AEMs commonly reported in peer reviewed papers mostly contain quaternary ammonium fixed cation groups, mainly in the form of benzyl trimethylammonium cations.14,19-40 However, it has been shown that quaternary ammonium-based AEMs are sensitive toward Hofmann elimination 20,41 and direct nucleophilic elimination reactions 42,43 that result in loss of ion exchange capacity (IEC) and ionic conductivity. To resolve the stability problem inherent to quaternary-ammonium-group-containing AEMs, several alternative cations, including imidazolium, 41,44,45 benzimidazolium, 3,45,46 guanidinium, 15,47,48 phosphonium 8,9,49 and metal cations 50,51 have been proposed and investigated. Phosphonium-based AEMs were investigated by Gu et al. 52 Gu et al. attached benzyl-tris(2,4,6-trimethoxyphenyl) phosphonium (TTMPP + ) onto polysulfone backbone to make AEMs, and found them to be alkaline stable; There was no ionic conductivity fade after immersion in 1M KOH for 30 days at room temperature. The bulky phosphonium-based AEMs remained stable in alkali because of the steric hindrance effect that protects the core phosphorus atom and the α-carbons against hydroxide ion attack. There is no possibility of β-elimination reaction because of the lack of hydrogen atoms in β-carbons. However, very few researchers have investigated in situ stability of bulky phosphorus-based AEMs. It is essential to correlate the ex situ stability results obtained in immersion alkaline stability tests with in situ stability in a functional H 2 /O 2 fuel cell.Hibbs 53 has shown that poly(phenylene)-bas...

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confidence: 99%

Anion Exchange Membranes Based on Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene Triblock Copolymers: Cation Stability and Fuel Cell Performance

Wang

Parrondo

Ramani

2017

J. Electrochem. Soc.

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“…Additional details regarding the NMR experiments are presented in the electronic supplementary information (ESI) and in our previous papers. 22,47,48 Anion exchange capacity was determined using Volhard titration. The AEMs (dry weight of approximately 0.1 g) were immersed in 20 mL of 1 M sodium nitrate for 48 h. The amount of chloride ions exchanged was determined by back titration using 0.1 M potassium thiocyanate, after addition of 5 mL of 0.1 M silver nitrate.…”

Section: Reduction Of the Ketone Group In Ppo-kc6br (Ppo-c6brmentioning

confidence: 99%

“…Additional details of the application of the method can be found in our previous papers. 3,6,10,14,47 Results and Discussion Figure 1 shows the scheme for the synthesis of modified imidazolium cation groups: 1-heptyl-2-methyl-imidazole (2MI-C7) and 1-dodecyl-2-methyl-imidazole (2MI-C12). The formation of 2MI-C7 was confirmed by the 1 H-NMR and 2D NMR (Correlation Spectroscopy; COSY) spectra as shown in Figures S1 and S2 49 The protons initially at 3.4 ppm (in the spectrum of 1-bromoheptane) shifted, after reaction with 2-methylimidazole, to ca.…”

Section: Reduction Of the Ketone Group In Ppo-kc6br (Ppo-c6brmentioning

confidence: 99%

“…Details of the calculations employed to arrive at this value can be found in our previous papers. 10,47 The shift of the protons present initially in the bromomethyl group (peak "3", initially at 4.33 ppm) to higher frequencies (5.30 ppm) was attributed to the proximate presence of the positively charged cation and demonstrated the formation of the product (P1, see Figure S6). A small shift in the protons of type "6", from ca.…”

Section: Reduction Of the Ketone Group In Ppo-kc6br (Ppo-c6brmentioning

confidence: 99%

“…Additional assessment of the presence of the ketone group in the benzyl position was performed using 13 C NMR spectroscopy in our previous paper. 47 The peak at 207 ppm corresponds to the carbon in the ketone group. 43 The 1 H NMR peak at 3.4 ppm (peak "9") corresponds to the protons in the bromomethyl group at the end of the pendant chain.…”

Section: Reduction Of the Ketone Group In Ppo-kc6br (Ppo-c6brmentioning

confidence: 99%

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Alkaline Stability of Poly(Phenylene Oxide) Based Anion Exchange Membranes Containing Imidazolium Cations

Wang

Parrondo

Ramani

2016

J. Electrochem. Soc.

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Two modified imidazole bases (1-heptyl-2-methyl-imidazole and 1-dodecyl-2-methyl-imidazole) were synthesized, each with a long alkyl chain (7 or 12 carbon) attached to the N-3 position. Anion exchange membranes (AEMs) were prepared with imidazolium cations derived from these bases that were either grafted directly onto the benzyl position of poly(phenylene oxide) (PPO) or affixed to the PPO using a hexyl spacer chain. First, we reacted 1-methylimidazole with brominated PPO and with PPO with a hexyl spacer chain. By comparing the alkaline stability of the resultant AEMs, we demonstrated that a hexyl spacer chain could improve AEM alkaline stability substantially. Second, by comparing the alkaline stability of PPO-based AEMs obtained by the reaction of brominated PPO with 1-methylimidazole and 1,2-dimethylimidazole, we showed that C-2-substituted (with a methyl group) imidazolium-based AEMs were much more stable in alkali than C-2-unsubstituted imidazolium-based AEMs. Finally, by investigating the alkaline stability of AEMs synthesized by reaction of brominated PPO with 1,2-dimethylimidazole and modified imidazole bases (with 7 or 12 alkyl carbon chain at the N-3 position), we demonstrated that the increase in length of a long alkyl chain affixed to the N-3 position decreases the alkaline stability of the resultant imidazolium-based AEMs. There is a growing interest in using anion exchange membranes (AEMs) as separators in alkaline membrane fuel cells (AMFCs) 1,2 and in other energy conversion and storage systems such as redox flow batteries (RFBs), 3-5 alkaline water electrolyzers (AWEs) 6,7 and reverse electrodialysis (RED) cells. 8 The most commonly used AEMs reported in the literature contain quaternary ammonium groups, primarily in the form of benzyl trimethylammonium cations.6,9-30 However, it had been shown that quaternary ammonium-based AEMs are sensitive toward Hofmann elimination 10,31 and direct nucleophilic elimination reactions 32,33 that result in loss of ion exchange capacity (IEC) and ionic conductivity. To resolve the stability problem inherent to quaternary-ammonium-group-containing AEMs, several alternative cations, including imidazolium, 31,34,35 benzimidazolium, 36 guanidinium, 37 phosphonium 38-40 and metal cations 41 have been proposed and investigated. Imidazolium-based AEMs have drawn researchers' interests mainly because of their high hydroxide-ion conductivities. 42 However, it has been reported that imidazoliumbased AEMs degrade under alkaline conditions at temperatures below 80• C. Ye and co-workers investigated the degradation mechanism of imidazolium-based AEMs at several relative humidities, temperatures and pH. They found that imidazolium-based AEMs were chemically stable at low temperatures, but relatively unstable at higher temperatures in alkaline conditions (degradation commences at 80• C when [KOH] >1 M). They postulated the following degradation mechanism: Ring-opening of the imidazolium ring was triggered by the nucleophilic attack of OH -on the imidazolium ring at the ...

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Properties and Alkaline Stability of Composite Anion Conducting Ionomers Based on Poly(phenylene oxide) Grafted with DABCO and Mg/Al Lamellar Double Hydroxide

Pasquini¹,

Becerra‐Arciniegas

Narducci

et al. 2020

ChemElectroChem

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We studied composite anion exchange membranes made from poly(2,6-dimethyl-1,4phenylene oxide) (PPO) with grafted 1,4-diazabicyclo[2.2.2]octane (DABCO) and Mg/Al lamellar double hydroxide particles as inorganic filler. The mechanical and conductivity properties were measured in fully humidified conditions. The activation energy for conductivity amounts to (0.20 ± 0.01) eV. The degradation of the anion exchange membrane in 2 M NaOH at 60 °C was investigated during 168 h following the ionic conductivity, water uptake and ion exchange capacity as function of the alkaline treatment time. The degradation is rapid within the first hours and then slows down. The degradation was also studied by thermogravimetric analysis and FTIR spectroscopy, showing the various decomposition phenomena of the composite.

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Synthesis and Alkaline Stability of Solubilized Anion Exchange Membrane Binders Based on Poly(phenylene oxide) Functionalized with Quaternary Ammonium Groups via a Hexyl Spacer

Cited by 47 publications

References 44 publications

Anion Exchange Membranes Based on Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene Triblock Copolymers: Cation Stability and Fuel Cell Performance

Anion Exchange Membranes Based on Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene Triblock Copolymers: Cation Stability and Fuel Cell Performance

Alkaline Stability of Poly(Phenylene Oxide) Based Anion Exchange Membranes Containing Imidazolium Cations

Properties and Alkaline Stability of Composite Anion Conducting Ionomers Based on Poly(phenylene oxide) Grafted with DABCO and Mg/Al Lamellar Double Hydroxide

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