Proton and water transport in nano-separated polymer membranes

Kreuer, Klaus‐Dieter; Ise, Martin; Fuchs, Annette; Maier, Joachim

doi:10.1051/jp4:2000756

Cited by 75 publications

(96 citation statements)

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“…The percent liquid uptake in 2 M methanol solution for SPEEK membranes at 65°C is lower or similar to that of Nafion ͑Table II͒, and under these conditions, the SPEEK membranes are known to have lower electro-osmotic drag coefficients than Nafion. 13,20 Therefore, the difference between the measured and actual limiting crossover current density values should be smaller (Ͻ30%) in SPEEK membranes compared to that with the Nafion membranes. This implies that the difference between the actual methanol crossover current densities of SPEEK and Nafion may be even larger than that seen in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, membranes based on SPEEK may help to alleviate the problems associated with high methanol crossover in DMFCs. However, the previous studies [12][13][14][15][16][17][18][19][20] have focused mainly on the physical properties such as swelling, thermal stability, and proton conductivity, and little information is available on the performance in DMFCs. We present here the performance of the SPEEK membranes in DMFCs and compare the data with that of Nafion.…”

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confidence: 99%

“…Kreuer and co-workers 13,19,20 compared the transport properties and the swelling behavior of sulfonated poly͑ether ether ketone͒ ͑SPEEK͒ with that of Nafion in terms of the differences in their microstructures. They found that the separation between the hydrophobic and hydrophilic groups is smaller, but the separation between the sulfonic acid functional groups is larger in SPEEK compared to that in Nafion.…”

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confidence: 99%

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Sulfonated Poly(ether ether ketone) Membranes for Direct Methanol Fuel Cells

Yang

Manthiram

2003

Electrochem. Solid-State Lett.

141

104

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Sulfonated poly͑ether ether ketone͒ ͑SPEEK͒ with different degrees of sulfonation has been prepared and evaluated as proton exchange membrane electrolytes in direct methanol fuel cells ͑DMFCs͒. The membranes have been characterized by ion-exchange capacity, proton conductivity, and liquid uptake measurements. The proton conductivity of the SPEEK membranes increases with increasing sulfonation level, and are lower than that of Nafion. The percent liquid uptake increases with increasing temperature, methanol concentration, and degree of sulfonation. Within a narrow range of sulfonation of ϳ50%, the SPEEK membranes exhibit electrochemical performances comparable to or exceeding that of Nafion at 65°C, making it an attractive low-cost alternative to Nafion. The better performance of the SPEEK membranes is due to the suppression of methanol permeability as indicated by a lower methanol crossover current density at the cathode. Currently, a hydrated perfluorosulfonic acid membrane called Nafion is used as the polymer electrolyte in both proton exchange membrane fuel cells ͑PEMFCs͒ and direct methanol fuel cells ͑DMFCs͒ due to its excellent chemical, mechanical, and thermal stabilities and relatively high proton conductivity ͑0.08 S/cm͒ in the hydrated state.1,2 However, the Nafion membrane is confronted with (i) high cost, (ii) limited operating temperature of Ͻ100°C as the membrane must be wet to allow proton conduction, [3][4][5] and (iii) high methanol permeability from the anode to the cathode in DMFCs. The methanol permeation results in a mixed reaction at the cathode that reduces the overall cell potential and fuel efficiency. These difficulties have created enormous interest in the development of alternate membranes. In this regard, several fluorine-free ionomer membranes such as polybenzimidazole, 6,7 polyimide, 8,9 polysulfones, 10,11 and polyketones 12-17 are being investigated actively. Proton conduction could be achieved with these ionomers by sulfonation 18 which increases the density of mobile protons as well as water uptake. However, high levels of sulfonation can lead to an undesirable swelling of the membranes and also dissolution in hot water. Therefore, the level of sulfonation must be optimized by controlling the reaction time and temperature to achieve a combination of adequate proton conductivity and mechanical property.Membranes based on the aromatic poly͑ether ether ketone͒ ͑PEEK͒ are promising for fuel cell applications as they possess good thermal stability and mechanical properties, and the proton conductivity can be controlled by the degree of sulfonation. Kreuer and co-workers 13,19,20 compared the transport properties and the swelling behavior of sulfonated poly͑ether ether ketone͒ ͑SPEEK͒ with that of Nafion in terms of the differences in their microstructures. They found that the separation between the hydrophobic and hydrophilic groups is smaller, but the separation between the sulfonic acid functional groups is larger in SPEEK compared to that in Nafion. These characteristics of SPEEK...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Sulfonated Poly(ether ether ketone) Membranes for Direct Methanol Fuel Cells

Yang

Manthiram

2003

Electrochem. Solid-State Lett.

141

104

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“…Under humidification one can, in principle, consider proton uptake in a manner analogous to that which occurs in proton-conducting perovskites such as doped barium zirconates and cerates. 18,19 In those materials, water incorporation is described by the reaction…”

Section: Introductionmentioning

confidence: 99%

Unusual decrease in conductivity upon hydration in acceptor doped, microcrystalline ceria

Chueh

Yang

Garland

et al. 2011

Phys. Chem. Chem. Phys.

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The impact of hydration on the transport properties of microcrystalline Sm 0.15 Ce 0.85 O 1.925 has been examined. Dense, polycrystalline samples were obtained by conventional ceramic processing and the grain boundary regions were found, by high resolution transmission electron microscopy, to be free of impurity phases. Impedance spectroscopy measurements were performed over the temperature range 250 to 650 1C under dry, H 2 O-saturated, and D 2 O-saturated synthetic air; and over the temperature range 575 to 650 1C under H 2 -H 2 O atmospheres. Under oxidizing conditions humidification by either H 2 O or D 2 O caused a substantial increase in the grain boundary resistivity, while leaving the bulk (or grain interior) properties unchanged. This unusual behavior, which was found to be both reversible and reproducible, is interpreted in terms of the space-charge model, which adequately explains all the features of the measured data. It is found that the space-charge potential increases by 5-7 mV under humidification, in turn, exacerbating oxygen vacancy depletion in the space-charge regions and leading to the observed reduction in grain boundary conductivity. It is proposed that the heightened space-charge potential reflects a change in the relative energetics of vacancy creation in the bulk and at the grain boundary interfaces as a result of water uptake into the grain boundary core. Negligible bulk water uptake is detected under both oxidizing and reducing conditions.

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“…On the other hand, thecombination of fluorinated backbone and sulfonic acid groups makes Nafion a very strong acid [21,22]. So the stability of the hydride electrode at different humidity needs to be further discussed.…”

Section: The Cell Charged With Electrochemical Methodsmentioning

confidence: 99%

A Solid-State Metal Hydride/Oxygen Cell using La0.78Ce0.22Ni3.73Mn0.30Al0.17Fe0.50Co0.30 in the Anodeand Nafion as Electrolyte

Zhang¹,

Wu²,

Chen³

et al. 2016

Proceedings of the 2nd Annual International Conference on Advanced Material Engineering (AME 2016)

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Abstract.A solid polymer electrolyte metal hydride (MH)/oxygen cell using La 0.78 Ce 0.22 Ni 3.73 Mn 0.30 Al 0.17 Fe 0.50 Co 0.30 in the anode and Nafion as electrolyte is described and investigated experimentally. In this work, the discharge performances of the cell are compared in two charging ways, namely, electrochemical and gas-solid hydrogenation. The specific discharge capacityby gas-solid hydrogenation method is about 59.3mAh·g -1 , while almost few specific discharge capacityis obtained by electrochemical method in this work. The cell is characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. And the ex-situ XRD results of the cell charged by gas-solid hydrogenation method show that an electrochemical reaction between hydrogen and oxygen does happen, and little observable side reaction occurs. Moreover, the stability of the MH electrode depending on various relative humidity is investigated. The results indicate that solid-state MH/O 2 cell using Nafion as electrolyte is technically feasible, while the control of the water content during charge/discharge processes and the catalyst loading must be the key points. More than that, further researches are still required to enhance both charge/discharge capacity and reversibility.

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Proton and water transport in nano-separated polymer membranes

Cited by 75 publications

References 0 publications

Sulfonated Poly(ether ether ketone) Membranes for Direct Methanol Fuel Cells

Sulfonated Poly(ether ether ketone) Membranes for Direct Methanol Fuel Cells

Unusual decrease in conductivity upon hydration in acceptor doped, microcrystalline ceria

A Solid-State Metal Hydride/Oxygen Cell using La0.78Ce0.22Ni3.73Mn0.30Al0.17Fe0.50Co0.30 in the Anodeand Nafion as Electrolyte

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