Novel anion exchange membranes based on polymerizable imidazolium salt for alkaline fuel cell applications

Abstract

A new polymerizable imidazolium salt monomer, 1-(4-vinylbenzyl)-3-methyl-imidazolium chloride ([VBMI]Cl), has been readily synthesized by reaction of 4-vinylbenzyl chloride with 1-methylimidazole. Novel anion exchange membranes (AEMs) based on the copolymers of [VBMI]Cl and styrene have been prepared and characterized. Excellent thermostability of the membranes is observed through the thermo-gravimetric analysis (TGA) curves. Water uptake and ion exchange capacity (IEC) of the OH(-) form AEMs range from 26.1% to 61.9% and from 0.95 to 1.45 mmol g(-1), respectively. This type of AEM displays significant ionic conductivities over the order of 10(-2) S cm(-1) in deionized water at room temperature, and the membranes are stable in 10 mol L(-1) NaOH solution at 60 degrees C for 120 h. For the H(2)/air single fuel cell at 30 degrees C with this novel AEM, the peak power density of 33 mW cm(-2) is obtained at a current density of 59 mA cm(-2).High-Tech Research and Development Program of China[2008AA05Z107]; National Nature Science Foundation of China[20876129

Stabilizing the Imidazolium Cation in Hydroxide‐Exchange Membranes for Fuel Cells

“…The strong electron-donating properties of 2,4,6-trimethoxyphenyl were confirmed by examining the 13 C NMR shifts of 4,5-dimethylimidazoles with and without the substituent: adding the 2,4,6-trimethoxyphenyl group shifted the peaks of the C4 and C5 atoms upfield (from 126.6 to 102.2 ppm) and that of the C2 atom downfield (from 132.3 to 137.8 ppm) (Table S2 and Figure S2). …”

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

“…However, the alkaline durability of the BPPO-based Im-AAEMS, while acceptable, is not as high as for styrene-based imidaolium systems (reportedly stable in NaOH (2 mol dm -3 ) for 120 h at 60°C). 28 A plausible explanation is that the ether bond in the polymer main chains is not stable in concentrated alkaline solutions, an instability that is exasperated by the low compactness of the methyl groups of the polymers main chains (allows more hydroxide ions to penetrating into membrane network). Hence, further research into intrinsically more stable bromomethylated aromatic polymers is under the way with the aim of targeting Im-type AAEMs with enhanced alkali stability.…”

“…28,34 However, the mechanical integrity of such aliphatic-chain polymers is likely to be compromised at the working temperatures of fuel cells due to the typically low glass-transition temperature of such polymers. 35 To address the above, this study targets the preparation of Im-AAEMs via the reaction of 1-methylimidazole with bromomethylated poly(phenylene oxide) (BPPO); these resulting BPPO-Im AAEMs contain stiff aromatic polymer main chains.…”

“…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.…”

Reduction of the monomer quantities required for the preparation of radiation-grafted alkaline anion-exchange membranes

“…The TPS results ( at 60°C respectively; the increased water contents and faster ion mobilities led to the increase in conductivities at higher temperatures [37]. The high bicarbonate (and calculated hydroxide) ion conductivities in the through-plane direction of the AEMs provides evidence of an even distribution of the VBC monomer through the thickness of the AEMs, which is contrary to the observations by Mamlouk et al where an emulsion technique was used to prepare similar AEMs from ETFE preformed films but using water as the solvent [30].…”