Nafion

About: Nafion is a research topic. Over the lifetime, 9110 publications have been published within this topic receiving 320865 citations.

Fluorene-Based Poly(arylene ether sulfone)s Containing Clustered Flexible Pendant Sulfonic Acids as Proton Exchange Membranes

Abstract: A new bisphenol monomer, 9,9-bis(3,5-dimethoxy-4-hydroxyphenyl) fluorene, was synthesized and polymerized to form fluorene-based poly(arylene ether sulfone) copolymers containing tetra-methoxy groups (MPAES). After converting the methoxy group to the reactive hydroxyl group, the respective side-chain type sulfonated copolymers (SPAES) were obtained by sulfobutylation. The polymers were characterized by 1H NMR, thermogravimetric analysis (TGA), water uptake, and proton and methanol transport for fuel cell applications. These SPAES copolymers had good overall properties as polymer electrolyte membrane (PEM) materials, having high proton conductivity in the range of 0.061–0.209 and 0.146–0.365 S/cm at 30 and 80 °C (under hydrated conditions), respectively. SPAES-39 (IEC = 1.93 mequiv/g) showed higher or comparable proton conductivity than that of Nafion 117 at 50–95% RH (relative humidity). The methanol permeabilities of these membranes were in the range of 3.22 to 13.1 × 10–7 cm2/s, which is lower than Nafi...

Multifunctional graphene/platinum/Nafion hybrids via ice templating.

Abstract: We report the synthesis of multifunctional hybrids in both films and bulk form, combining electrical and ionic conductivity with porosity and catalytic activity. The hybrids are synthesized by a two-step process: (a) ice templation of an aqueous suspension comprised of Nafion, graphite oxide, and chloroplatinic acid to form a microcellular porous network and (b) mild reduction in hydrazine or monosodium citrate which leads to graphene-supported Pt nanoparticles on a Nafion scaffold.

Synthesis and proton conductivity of partially sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene) block copolymers

Abstract: A series of novel, amphiphilic block copolymers comprising of sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene) [P(VDF-co-HFP)-b-SPS] were synthesized. The number-average molecular weights of the fluorous and polystyrene segments were 17 900 and 8100 g/mol, respectively. Sulfonation of the polystyrene segment to different extents provided a series of polymers which were cast into films to yield proton exchange membranes with varying ion exchange capacity (IEC). Proton conductivity of the membranes increased significantly when the IEC was increased from 0.5 to 1.2 mmol/g. For 0.9−1.2 mmol/g IEC membranes, the conductivity was similar to Nafion 117, significantly higher than random copolymers of polystyrene and sulfonated polystyrene, and twice that of nonfluorous block copolymer membranes based on sulfonated poly(styrene-b-[ethylene-co-butylene]-b-styrene) (S-SEBS) and sulfonated hydrogenated poly(butadiene-b-styrene) (S-HPBS) copolymers. TEM revealed a disruption in ordered morphol...

Hexamethyl-p-terphenyl poly(benzimidazolium): a universal hydroxide-conducting polymer for energy conversion devices

Abstract: A hydroxide-conducting polymer, HMT-PMBI, which is prepared by methylation of poly[2,2′-(2,2′′,4,4′′,6,6′′-hexamethyl-p-terphenyl-3,3′′-diyl)-5,5′-bibenzimidazole] (HMT-PBI), is utilized as both the polymer electrolyte membrane and ionomer in an alkaline anion-exchange membrane fuel cell and alkaline polymer electrolyzer. A fuel cell operating between 60 and 90 °C and subjected to operational shutdown, restarts, and CO2-containing air demonstrates remarkable in situ stability for >4 days, over which its performance improved. An HMT-PMBI-based fuel cell was operated at current densities >1000 mA cm−2 and power densities of 370 mW cm−2 at 60 °C. When similarly operated in a water electrolyzer with circulating 1 M KOH electrolyte at 60 °C, its performance was unchanged after 8 days of operation. Methodology for up-scaled synthesis of HMT-PMBI is presented, wherein >½ kg is synthesized in six steps with a yield of 42%. Each step is optimized to achieve high batch-to-batch reproducibility. Water uptake, dimensional swelling, and ionic conductivity of HMT-PMBI membranes exchanged with various anions are reported. In the fully-hydrated chloride form, HMT-PMBI membranes are mechanically strong, and possess a tensile strength and Young's modulus of 33 MPa and 225 MPa, respectively, which are significantly higher than Nafion 212, for example. The hydroxide anion form shows remarkable ex situ chemical and mechanical stability and is seemingly unchanged after a 7 days exposure to 1 M NaOH at 80 °C or 6 M NaOH at 25 °C. Only 6% chemical degradation is observed when exposed to 2 M NaOH at 80 °C for 7 days. The ease of synthesis, synthetic reproducibility, scale-up, and exceptional in situ and ex situ properties of HMT-PMBI renders this a potential benchmark polymer for energy conversion devices requiring an anion-exchange material.