Preface

Eisenberg, A.; Yeager, H. L.

doi:10.1021/bk-1982-0180.pr001

Cited by 41 publications

(50 citation statements)

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“…The expensive Pt-based catalysts, combined with perfluorinated membranes and corrosion-resistant cell hardware increase the cost of PEMFC devices beyond what is currently commercially viable. 7,8 Alkaline fuel cells (AFCs) have received significant interest in recent years relative to acidic fuel cells, 9−14 because of advantages when operating under alkaline conditions, which include enhancement of the electrode reaction kinetics, especially at the cathode, and the catalysts are not subjected to corrosion at high pH. 9,12,13 Consequently, non-noble metals or inexpensive metal oxides can be used as catalysts to greatly reduce the cost of the device.…”

Section: ■ Introductionmentioning

confidence: 99%

Highly Stable, Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells

et al. 2013

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To produce an anion-conductive and durable polymer electrolyte for alkaline fuel cell applications, a series of quaternized poly(2,6-dimethyl phenylene oxide)s containing long alkyl side chains pendant to the nitrogen-centered cation were synthesized using a Menshutkin reaction to form combshaped structures. The pendant alkyl chains were responsible for the development of highly conductive ionic domains, as confirmed by small-angle X-ray scattering (SAXS). The combshaped polymers having one alkyl side chain showed higher hydroxide conductivities than those with benzyltrimethyl ammonium moieties or structures with more than one alkyl side chain per cationic site. The highest conductivity was observed for comb-shaped polymers with benzyldimethylhexadecyl ammonium cations. The chemical stabilities of the comb-shaped membranes were evaluated under severe, accelerated-aging conditions, and degradation was observed by measuring IEC and ion conductivity changes during aging. The comb-shaped membranes retained their high ion conductivity in 1 M NaOH at 80°C for 2000 h. These cationic polymers were employed as ionomers in catalyst layers for alkaline fuel cells. The results indicated that the C-16 alkyl side chain ionomer had a slightly better initial performance, despite its low IEC value, but very poor durability in the fuel cell. In contrast, 90% of the initial performance was retained for the alkaline fuel cell with electrodes containing the C-6 side chain after 60 h of fuel cell operation. ■ INTRODUCTIONFuel cells are efficient energy conversion devices that generate electric power from energy-dense chemical fuels and have been attracting attention as a clean energy technology. 1−3 The most widespread low-temperature fuel cell technologies are based on sulfonated polymer membranes to separate the oxidant and fuel chambers and conduct protons between the anode and cathode of the cell. 4−6 These proton exchange membrane fuel cells (PEMFC) principally employ Nafion, a product from DuPont, as the sulfonated polymeric proton conductor. PEMFCs require platinum or other precious metal-based catalysts because these are the only types of metal catalysts stable under the low pH and electrochemical conditions of an operating cell. The expensive Pt-based catalysts, combined with perfluorinated membranes and corrosion-resistant cell hardware increase the cost of PEMFC devices beyond what is currently commercially viable. 7,8 Alkaline fuel cells (AFCs) have received significant interest in recent years relative to acidic fuel cells, 9−14 because of advantages when operating under alkaline conditions, which include enhancement of the electrode reaction kinetics, especially at the cathode, and the catalysts are not subjected to corrosion at high pH. 9,12,13 Consequently, non-noble metals or inexpensive metal oxides can be used as catalysts to greatly reduce the cost of the device. 13−16 In addition, high energy density liquids and gases such as ethanol, hydrazine, and ammonia can be adopted as fuels. 17,18 Alkaline fuel ...

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Section: ■ Introductionmentioning

confidence: 99%

Highly Stable, Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells

et al. 2013

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“…The phase transition temperatures determined from the development of the o-Ps lifetime are summarized in Table I. The α-transition [11] observed at ≈ 60…”

Section: Resultsmentioning

confidence: 99%

“…Sodaye et al [10] studied the effect of temperature on free volumes in Nafion by the Doppler broadening (DB) spectroscopy and found a strong variation of the line-shape S-parameter with temperature of the sample. Phase transitions in H + form of Nafion were deduced from changes in the slope of the S-parameter temperature dependence, namely a low temperature γ-transition [11] taking place at ≈ −100…”

Section: Introductionmentioning

confidence: 99%

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Thermal Development of Free Volumes in Nafion Membrane

et al. 2017

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In this work we employed positron lifetime spectroscopy for investigation of the thermal development of free volumes in H + Nafion membrane over a broad range of temperatures from -150 to 150• C. Positron lifetime studies were combined with differential scanning calorimetry. Size distribution of free volumes was determined from ortho-positronium contribution to positron lifetime spectra. Our investigations revealed that the mean size of free volume holes strongly increases with temperature. On the other hand, the width of the size distribution and the positronium yield decreases with temperature. Transition temperatures corresponding to a change in the slope of the temperature dependence of ortho-positronium lifetime were identified. Results of positron lifetime spectroscopy agree well with the curve obtained by differential scanning calorimetry.

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“…During the last 40 years, perfluorosulfonic acid polymers such as Nafion have been used predominantly as PEMs in PEMFCs [7,8]. The perfluorinated structure provides good thermal and chemical stability and high proton conductivity.…”

Section: Introductionmentioning

confidence: 99%

Partially Fluorinated Sulfonated Poly(ether amide) Fuel Cell Membranes: Influence of Chemical Structure on Membrane Properties

2011

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A series of fluorinated sulfonated poly (ether amide)s (SPAs) were synthesized for proton exchange membrane fuel cell applications. A polycondensation reaction of 4,4'-oxydianiline, 2-sulfoterephthalic acid monosodium salt, and tetrafluorophenylene dicarboxylic acids (terephthalic and isophthalic) or fluoroaliphatic dicarboxylic acids produced SPAs with sulfonation degrees of 80-90%. Controlling the feed ratio of the sulfonated and unsulfonated dicarboxylic acid monomers afforded random SPAs with ion exchange capacities between 1.7 and 2.2 meq/g and good solubility in polar aprotic solvents. Their structures were characterized using NMR and FT IR spectroscopies. Tough, flexible, and transparent films were obtained with dimethylsulfoxide using a solution casting method. Most SPA membranes with 90% sulfonation degree showed high proton conductivity (>100 mS/cm) at 80 °C and 100% relative humidity. Among them, two outstanding ionomers (ODA-STA-TPA-90 and ODA-STA-IPA-90) showed proton conductivity comparable to that of Nafion 117 between 40 and 80 °C. The influence of chemical structure on the membrane properties was systematically investigated by comparing the fluorinated polymers to their hydrogenated counterparts. The results suggest that the incorporation of fluorinated moieties in the polymer backbone of the membrane reduces water absorption. High molecular weight and the resulting physical entanglement of the polymers chains played a more important role in improving stability in water, however. OPEN ACCESSPolymers 2011, 3 223

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Preface

Cited by 41 publications

References 0 publications

Highly Stable, Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells

Highly Stable, Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells

Thermal Development of Free Volumes in Nafion Membrane

Partially Fluorinated Sulfonated Poly(ether amide) Fuel Cell Membranes: Influence of Chemical Structure on Membrane Properties

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