Thermodynamics of water sorption by perfluorosulphonate (Nafion-117) and polystyrene–divinylbenzene sulphonate (Dowex 50W) ion-exchange resins at 298 ± 1 K

Pushpa, K. K.; Nandan, Deoki; Iyer, R.M.

doi:10.1039/f19888402047

Cited by 94 publications

(94 citation statements)

References 2 publications

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“…These solvention interactions decrease the number of water molecules available for cation hydration and limit the overall water uptake. 17 Though sPEEK's higher water uptake may be expected to lead to higher permeabilities of redox-active species, this was not observed for sPEEK, see Table I. This is attributed to differences in the water cluster structure between PFSA and sPEEK.…”

Section: Resultsmentioning

confidence: 72%

Communication—Sulfonated Poly (ether ether ketone) as Cation Exchange Membrane for Alkaline Redox Flow Batteries

Porcellinis

Mecheri

D’Epifanio

et al. 2018

J. Electrochem. Soc.

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A sulfonated poly (ether ether ketone) (sPEEK) was tested as the separator in a full alkaline flow battery with 2,6-dihydroxyanthraquinone-ferro/ferricyanide, DHAQ-FeCy, redox couples. Cell performance was compared to that of an identical cell utilizing a perfluorosulfonic acid (PFSA) membrane. Replacement of the PFSA membrane with sPEEK resulted in a 10% power density increase, a 40% decrease in capacity loss per day and an 85-fold decrease in ferricyanide permeation. Though long-term stability of sPEEK in alkaline media requires improvement, these results highlight the potential to produce non-fluorinated membranes with better performance in organic redox flow batteries than the commercially available PFSAs. Aqueous organic redox flow batteries (AORFBs) constitute one of the most attractive alternatives to solve the storage problem associated with environmentally friendly, yet intermittent, power sources. 1,2-9Promising electrolyte compositions have been reported for AORFBs using commercially available cation exchange membranes (CEMs) as the electrode separator. The typical materials of choice for these membranes are perfluorinated sulfonic acids (PFSAs), such as Nafion. One barrier that hinders their widespread adoption is their relatively high cost.10 Replacement of PFSAs with a non-fluorinated membrane could reduce the cost of the films by a factor of 2.5 and facilitate the commercial implementation of AORFBs.11 Though inspiring new AORFBs operating at neutral pH have recently been reported, 8,[12][13][14] the majority of the systems developed to date require relatively harsh operation conditions (pH>13 or pH<0). These operating parameters limit the polymer chemistry choices that warrant further exploration. One promising starting point is the sulfonated version of poly ether ether ketone (sPEEK). This material has been previously tested as the CEM in fuel cells and vanadium redox flow batteries.15,16 Herein we compare the performance of a sPEEK membrane with a 50% degree of sulfonation with that of a commercially available perfluorinated alternative, Nafion NR212. The sPEEK membranes exhibited higher ionic conductivity, higher peak power density, lower capacity loss per cycle, and lower crossover of electroactive species than the PFSA membranes. Though the long-term stability of these nonfluorinated polymers needs to be improved, these results illustrate the potential for producing non-fluorinated membranes with comparable or better performance than the commercially available PFSAs, if the hydrolysis-prone heteroatoms are eliminated from the polymer backbone. ExperimentalThe procedures used for membrane preparation and characterization, as well as cell assembly and testing, are included in the supplemental information (SI). Results and DiscussionMembrane properties relevant for flow cell performance are presented in Table I. The higher conductivity observed for sPEEK is ascribable to its higher ion exchange capacity and higher water uptake. The water uptake differences between sPEEK and Nafion in their cor...

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Section: Resultsmentioning

confidence: 72%

Communication—Sulfonated Poly (ether ether ketone) as Cation Exchange Membrane for Alkaline Redox Flow Batteries

Porcellinis

Mecheri

D’Epifanio

et al. 2018

J. Electrochem. Soc.

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“…[8] suggests that for a highly swollen membrane ( w   0.25), the swelling pressure is between 20 and 25 MPa, which is higher than the cell assembly pressures (1 to 3 MPa), but within the same order of magnitude with the measured values in this work and in the literature. [21][22][23] The consistency between the measured and calculated pressure values also lend credence to the modeling approach taken.…”

Section: Resultsmentioning

confidence: 99%

“…[17] by replacing the external pressure term with the in-plane pressure term in Eq. [23] (i.e., e in-plane…”

Section: Swelling Of a Constrained Membranementioning

confidence: 99%

“…[18][19][20] There are a limited number of studies focused on measuring the swelling pressure in the membrane using custom-made fixtures and reported pressures between 30-100 MPa. [21][22][23] Moreover, except for a few studies investigating the constraints in PEFCs, 1,3,24 mathematical models generally assume that membranes are unconstrained (although with a given thickness, i.e., swelling is ignored). In fact, there has been only minimal research into swelling of constrained polymers in general with notable exceptions of gels and elastomers, for which Flory-Rehner theory 25,26 is commonly employed to develop models.…”

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confidence: 99%

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Understanding the Effects of Compression and Constraints on Water Uptake of Fuel-Cell Membranes

Kusoglu

Kienitz

Weber

2011

J. Electrochem. Soc.

118

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Accurate characterization of polymer-electrolyte fuel cells (PEFCs) requires understanding the impact of mechanical and electrochemical loads on cell components. An essential aspect of this relationship is the effect of compression on the polymer membrane's water-uptake behavior and transport properties. However, there is limited information on the impact of physical constraints on membrane properties. In this paper, we investigate both theoretically and experimentally how the water uptake of Nafion membrane changes under external compression loads. The swelling of a compressed membrane is modeled by modifying the swelling pressure in the polymer backbone which relies on the changes in the microscopic volume of the polymer. The model successfully predicts the water content of the compressed membrane measured through in-situ swelling-compression tests and neutron imaging. The results show that external mechanical loads could reduce the water content and conductivity of the membrane, especially at lower temperatures, higher humidities, and in liquid water. The modeling framework and experimental data provide valuable insight for the swelling and conductivity of constrained and compressed membranes, which are of interest in electrochemical devices such as batteries and fuel cells. † Current Address: W.L. Gore and Associates, 201 Airport Road, Elkton, MD USA ‡ Corresponding author. E-mail address: azweber@lbl.gov Tel: (510) 486-6308. * ECS Member. IntroductionIonomer membranes used in polymer-electrolyte-fuel-cell (PEFC) applications are always subjected to mechanical constraints to some extent due to cell design and clamping loads to reduce contact resistances and seal cells using compression seals. Furthermore, swelling of the membranes due to water uptake results in compressive stresses during cell operation. [1][2][3] Compression in the cell is known to influence membrane stresses, [2][3][4][5][6] transport in gas-diffusion layers (GDL), [7][8][9] and cell resistance. 10 However, the effect of the constraints and mechanical loads on the membrane's water-uptake behavior is yet to be determined due to the difficulty of such measurement. Moreover, due to the lack of the experimental data on the swelling behavior of constrained membranes, mathematical models on water uptake cannot be fully validated. In this work, we aim to investigate how the constraints on the membrane affect its water-uptake behavior and other water-dependent transport properties such as conductivity.In a PEFC, the extent to which the membrane is deformed depends on a number of factors including, but not limited to, geometry of the cell (e.g. land/channel ratio), thickness and stiffness of the cell components (e.g. bipolar plates, gas-diffusion layers (GDLs)), and operating conditions (e.g., humidity). Thus, stresses and pressures in the membrane are not uniform; they depend on location, time, and component material properties. In addition, the membrane itself is subjected to a combination of constraints and mechanical loads: (i) interfacial con...

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“…Despite the fact that many models are used to investigate transient transport processes in PEFCs, they usually rely on material properties that are not well characterised, due to the intrinsic difficulties in measuring such properties, i.e. as those related to the charge and mass transfer in the ionomer membrane [11,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. This inaccuracy increases the difficulty of validating the models.…”

Section: Introductionmentioning

confidence: 99%

1D‐Modelling and Experimental Study of the PEFC Dynamic Behaviour at Load Increase

et al. 2011

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The complex dynamic response of a 1‐dimensional polymer electrolyte fuel cell to load changes is numerically and experimentally investigated, in order to understand the transient transport processes in the different domains of the cell through the membrane‐electrode assembly. The analysis focuses on the comparison of cell response to step load changes, at different levels of reactants humidification. To render the model capable of capturing the cell behaviour at different operating conditions, a multiparameter optimisation procedure is performed to determine the most sensitive transport parameters. The optimisation procedure converges towards a well‐defined solution and the resulting parameters are compared to those available in the literature. Model results indicate that the time required to reach the new steady‐state after a load increase is controlled by the water transport in the membrane. The influence of the water diffusion coefficient at the different operating conditions is further investigated numerically.

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Thermodynamics of water sorption by perfluorosulphonate (Nafion-117) and polystyrene–divinylbenzene sulphonate (Dowex 50W) ion-exchange resins at 298 ± 1 K

Cited by 94 publications

References 2 publications

Communication—Sulfonated Poly (ether ether ketone) as Cation Exchange Membrane for Alkaline Redox Flow Batteries

Communication—Sulfonated Poly (ether ether ketone) as Cation Exchange Membrane for Alkaline Redox Flow Batteries

Understanding the Effects of Compression and Constraints on Water Uptake of Fuel-Cell Membranes

1D‐Modelling and Experimental Study of the PEFC Dynamic Behaviour at Load Increase

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