Perspective—Prospects for Durable Hydrocarbon-Based Fuel Cell Membranes

Gubler, Lorenz; Nauser, Thomas; Coms, Frank D.; Lai, Yeh-Hung; Gittleman, Craig S.

doi:10.1149/2.0131806jes

Cited by 51 publications

(61 citation statements)

References 44 publications

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“…These ionomers are of interest to replace the widely used perfluoroalkylsulfonic acid (PFSA) membranes, owing to their much lower gas permeability, higher glass transition temperature, and potentially lower cost. 1 Oxidative stress is created by the presence of radical species, such as HO , H and HOO , which are formed during the operation of the fuel cell in the presence of H 2 , O 2 , and the noble metal catalyst. 2 The hydroxyl radical (HO ) can be particularly detrimental to the polymer as it initiates degradation.…”

Section: Introductionmentioning

confidence: 99%

Attack of hydroxyl radicals to α-methyl-styrene sulfonate polymers and cerium-mediated repair via radical cations

Nolte

Nauser

Gubler

2020

Phys. Chem. Chem. Phys.

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Both synthetic polymers (membranes, coatings, packaging) and natural polymers (DNA, proteins) are subject to radical-initiated degradation. In order to mitigate the deterioration of the polymer properties, antioxidant strategies need to be devised. We studied the reactions of poly(a-methylstyrene sulfonate), a model compound for fuel cell membrane materials, with different degrees of polymerization with OH radicals as well as subsequent reactions. We observed the resulting OH -adducts to react with oxygen and eliminate H 2 O, the relative likelihood of which is determined by pH and molecular weight. The resulting radical cations can be reduced back to the parent molecule by cerium(III). This 'repair' reaction is also dependent on molecular weight likely because of intramolecular stabilization. The results from this study provide a starting point for the development of new hydrocarbon-based ionomer materials for fuel cells that are more resistant to radical induced degradation through the detoxification of intermediates via damage transfer and repair pathways. Furthermore, a more fundamental understanding of the mechanisms behind conventional antioxidants in medicine, such as ceria nanoparticles, is achieved.

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Section: Introductionmentioning

confidence: 99%

Attack of hydroxyl radicals to α-methyl-styrene sulfonate polymers and cerium-mediated repair via radical cations

Nolte

Nauser

Gubler

2020

Phys. Chem. Chem. Phys.

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“…[23][24][25] Within this subset of aromatic-hydrocarbon-based PEMs exists a multitude of synthetic strategies to obtain various chemical architectures from comparatively lowcost starting materials. Common examples include sulfonated derivatives of poly(arylene ether sulfone)s, [26][27][28][29] poly(ether ether ketone)s, 13,30 poly(phenylene oxide)s, 31 poly(benzimidazole) s, [32][33][34][35] poly(imide)s 36 and poly(phenylene)s. [37][38][39][40][41][42] Of the numerous hydrocarbon-based structures examined in the literature to date, recent developments on sulfonated poly(phenylene)s have been particularly promising. These polymers, which are composed wholly of aryl-aryl linkages devoid of labile heteroatomic linkages, are potentially more resilient to oxidative degradation than other hydrocarbon PEMs, both ex situ 25,37,38,40,41 and in situ.…”

Section: Introductionmentioning

confidence: 99%

“…Within this subset of aromatic‐hydrocarbon‐based PEMs exists a multitude of synthetic strategies to obtain various chemical architectures from comparatively low‐cost starting materials. Common examples include sulfonated derivatives of poly(arylene ether sulfone)s, 26–29 poly(ether ether ketone)s, 13,30 poly(phenylene oxide)s, 31 poly(benzimidazole)s, 32–35 poly(imide)s 36 and poly(phenylene)s 37–42 …”

Section: Introductionmentioning

confidence: 99%

Effect of steric constraints on the physico‐electrochemical properties of sulfonated polyaromatic copolymers

Peressin

Adamski

Holdcroft

2020

Polymer International

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The impact of incorporating additional steric restrictions into highly sterically encumbered sulfonated polyaromatic polymers was investigated. Copolymers possessing between 0 and 10% nonlinear ortho or meta biphenyl units in an otherwise linear para biphenyl-containing sulfo-phenylated poly(phenylene) were synthesized in yields >80% and evaluated on the basis of their physical and electrochemical properties. When incorporated into sulfonated copolymers in ≤5 mol%, ortho and meta linked biphenyl moieties reduced membrane swelling in water by up to 23 and 19 vol%, respectively, compared to strictly para biphenyl-linked copolymers. Despite this, copolymers possessing nonlinear, biphenyl-linked monomers displayed a decrease in proton conductivity and mechanical strength. This study reinforces the importance of considering restricted rotation, backbone flexibility, and chain entanglement in the design of polymers aimed at improving their physical and electrochemical properties.

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“…It could be done only by filling high-conductivity ionomers into porous substrates or by forming a three-layered structure (ionomer/ionomer filled substrate/ionomer) [12][13][14][15][16][17][18][19][20]. Perfluorosuflonic acid (PFSA) ionomers are still the most frequently used material even though less expensive hydrocarbon membranes have been intensively developed [7,[21][22][23] Among many reasons for the use of PFSA ionomers, the main one would be the good stability against mechanical and chemical stress occurring during fuel cell or water electrolysis operation. Since the less volume of PFSA is used compared to non-reinforced PFSA membranes, benefits can be obtained in terms of material cost [12,24,25].…”

Section: Introductionmentioning

confidence: 99%

Composite Membranes Using Hydrophilized Porous Substrates for Hydrogen Based Energy Conversion

Lim¹,

Park²

2020

Energies

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Poly(tetrafluoroethylene) (PTFE) porous substrate-reinforced composite membranes for energy conversion technologies are prepared and characterized. In particular, we develop a new hydrophilic treatment method by in-situ biomimetic silicification for PTFE substrates having high porosity (60–80%) since it is difficult to impregnate ionomer into strongly hydrophobic PTFE porous substrates for the preparation of composite membranes. The thinner substrate having ~5 μm treated by the gallic acid/(3-trimethoxysilylpropyl)diethylenetriamine solution with the incubation time of 30 min shows the best hydrophilic treatment result in terms of contact angle. In addition, the composite membranes using the porous substrates show the highest proton conductivity and the lowest water uptake and swelling ratio. Membrane-electrode assemblies (MEAs) using the composite membranes (thinner and lower proton conductivity) and Nafion 212 (thicker and higher proton conductivity), which have similar areal resistance, are compared in I–V polarization curves. The I–V polarization curves of two MEAs in activation and Ohmic region are very identical. However, higher mass transport limitation is observed for Nafion 212 since the composite membrane with less thickness than Nafion 212 would result in higher back diffusion of water and mitigate cathode flooding.

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Perspective—Prospects for Durable Hydrocarbon-Based Fuel Cell Membranes

Cited by 51 publications

References 44 publications

Attack of hydroxyl radicals to α-methyl-styrene sulfonate polymers and cerium-mediated repair via radical cations

Attack of hydroxyl radicals to α-methyl-styrene sulfonate polymers and cerium-mediated repair via radical cations

Effect of steric constraints on the physico‐electrochemical properties of sulfonated polyaromatic copolymers

Composite Membranes Using Hydrophilized Porous Substrates for Hydrogen Based Energy Conversion

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