Proton Conducting Membranes Obtained by Doping Radiation‐Grafted Basic Membrane Matrices with Phosphoric Acid

Abstract

By grafting 4‐vinylpyridine (4VP), N‐vinylformamide (NVF), and 1‐vinylimidazole (1VIm) onto electron beam irradiated ETFE and FEP films, the basic membrane matrices ETFE‐graft‐poly(4VP), FEP‐graft‐poly(4VP), ETFE‐graft‐poly(1VIm), and ETFE‐graft‐poly(vinylamine), after subsequent hydrolysis of ETFE‐graft‐poly(NVF), can be obtained. These matrices are doped with phosphoric acid to produce acid–base composite materials that exhibit high proton conductivities up to 100 mS · cm−1 at high temperatures (120 °C) and no humidification. The produced membranes are robust, flexible, and mechanically stable even at high doping levels and endure temperatures of up to 160 °C. Preliminary tests in H2/O2 fuel cells provide power densities between 75 and 150 mA · cm−2 at 120 °C without humidification.magnified image

Novel concept of polymer electrolyte membranes for high-temperature fuel cells based on ETFE grafted with neutral acrylic monomers

“…In addition, glycidyl methacrylate and butyl acrylate were grafted to ETFE and subsequently the epoxy group was aminated. Some of the systems were tested in fuel cells and proved the concept that PA is an effective proton conductor [52,53].…”

“…As an example, poly(ethylene-alt-tetrafluoroethylene) (ETFE) was used [8,[52][53][54][55][56][57][58][59]. Generally, the polymer backbone material was irradiated and subsequently grafted with basic monomer(s), since it was anticipated that the affinity to PA scales with basicity.…”

Polymer‐Säure‐Komposite auf Basis strahlungsinduzierter Pfropfpolymerisation für Hochtemperatur‐PEM‐Brennstoffzellen

“…Pfropfmembranen vom Typ ETFE-g-P(NVF) werden durch Hydrolyse in Natronlauge (NaOH, 1 mol/L) bei 80°C 12 h mit nachfolgender gründlicher Reinigung der Membranen mit Wasser [9] zum stark basischen P(VA) (pK b (Methylamin) = 3,4) [16] umgesetzt (Schema 2).…”

Copolymers of Poly(2,5‐benzimidazole) and Poly[2,2′‐(p‐phenylene)‐5,5′‐bibenzimidazole] for High‐Temperature Fuel Cell Applications

“…[5] High-temperature operation of PEMs can overcome many of the shortcomings of low-temperature operations (below 100 8C), such as low tolerance to fuel impurities such as carbon monoxide (CO), slow cathode kinetics, water management problems, the requirement for intensive cooling, cathode flooding, and conductivity and cell performance drops due to the relatively low-humidity environment. [5][6][7][8][9] Among the PBI membranes, poly[2,2 0 -(m-phenylene)-5,5 0 -bibenzimidazole] (mPBI) has been the most systematically studied with regard to its performance in acid doping, [9][10][11][12] water uptake, [12] proton conductivity, [9,11,[13][14][15][16] mechanical stability, [9,16,17] thermal stability, [9,18] water drag coefficient, [19,20] methanol crossover, [10,20] gas permeability [17] and fuel cell tests. [6,9,10,19,21] Recently, poly(2,5-benzimidazole) (ABPBI) has also been studied by several research groups [22][23][24] because of its advantages over mPBI, such as low cost, simple polymerization condition and high proton conductivity.…”

“…[5][6][7][8][9] Among the PBI membranes, poly[2,2 0 -(m-phenylene)-5,5 0 -bibenzimidazole] (mPBI) has been the most systematically studied with regard to its performance in acid doping, [9][10][11][12] water uptake, [12] proton conductivity, [9,11,[13][14][15][16] mechanical stability, [9,16,17] thermal stability, [9,18] water drag coefficient, [19,20] methanol crossover, [10,20] gas permeability [17] and fuel cell tests. [6,9,10,19,21] Recently, poly(2,5-benzimidazole) (ABPBI) has also been studied by several research groups [22][23][24] because of its advantages over mPBI, such as low cost, simple polymerization condition and high proton conductivity. [23][24][25][26][27][28][29][30] However, the practical application of ABPBI membranes in high-temperature fuel cells might not be possible because of its poor chemical and mechanical stability; when ABPBI membranes are doped using a high concentration of H 3 PO 4 to increase its acid doping level, they dissolve completely.…”