Proton dissociation and transfer in proton exchange membrane ionomers with multiple and distinct pendant acid groups: An ab initio study

Clark, J. R.; Paddison, Stephen J.

doi:10.1016/j.electacta.2012.11.138

Cited by 32 publications

(53 citation statements)

References 88 publications

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“…Based on theoretical calculations, several configurations of hydrogen bonded structures were reported in ionomers having multiple acidic sites per side chains. 27 For 3M PFIA the first proton dissociation was reported with only three water molecules in the lowest energy structure where the ionic sulfonate group is hydrogen bonded (via hydronium ion and two water molecules) to the SQO group of the un-dissociated bis(sulfonyl imide group). Since hydrogen bonding causes a downshift of the corresponding SQO stretching mode, 64 the strong 1439 cm À1 peak in this phase is most likely due to the SQO mode hydrogen-bonded in a structure as reported by Clark et al, 27 whereas the 1450 cm À1 shoulder is caused by a similar, but weakly or non-hydrogen bonded SQO mode.…”

Section: Acidic Formsmentioning

confidence: 97%

“…27 For 3M PFIA the first proton dissociation was reported with only three water molecules in the lowest energy structure where the ionic sulfonate group is hydrogen bonded (via hydronium ion and two water molecules) to the SQO group of the un-dissociated bis(sulfonyl imide group). Since hydrogen bonding causes a downshift of the corresponding SQO stretching mode, 64 the strong 1439 cm À1 peak in this phase is most likely due to the SQO mode hydrogen-bonded in a structure as reported by Clark et al, 27 whereas the 1450 cm À1 shoulder is caused by a similar, but weakly or non-hydrogen bonded SQO mode. By the end of this phase (B12-15 min after start of heating), no further increase of the 1439 cm À1 band was observed while the bands at 1086 and 1346 cm À1 had (almost) completely disappeared, demonstrating that the majority of the SNS À groups have already been neutralized.…”

Section: Acidic Formsmentioning

confidence: 97%

“…18,[21][22][23] The hydrated hydronium ions are found in Zundel 24 26 Recent developments towards improved PEM performance reported use of multi acid side chains to retain high proton conductivity, stabilizing additives for improved chemical or polymer nanofibers for mechanical stability. 8,10,27 Having multiple acidic sites per side chain lowers the ionomer equivalent weight (EW = grams of ionomer per mole of acid) without compromising the mechanical stability and allows for the formation of larger ionic channels which increases proton conductivity. 28 Perfluoroimide acid or PFIA is one of these multi-acid PEMs recently developed by the 3M Company's (3M) Fuel Cell Components Group that incorporates a bis-sulfonyl imide group into pendant chains providing an additional source of the protonic group (Scheme 1A, compare Scheme 1B for NAFIONt).…”

Section: Introductionmentioning

confidence: 99%

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Infrared dynamics study of thermally treated perfluoroimide acid proton exchange membranes

Puškar

Ritter

Schade

et al. 2017

Phys. Chem. Chem. Phys.

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The temperature induced dehydration process of the 3M Brand perfluoroimide acid (PFIA), an advanced proton exchange membrane for fuel cells, was studied by in situ infrared spectroscopy to understand proton transport processes under conditions of low hydration levels. A comprehensive assignment of the vibrational bands of PFIA in the mid infrared region is provided. Investigation of the kinetics in conjunction with 2D correlation spectroscopy methods revealed the sequential process of the hydration and dehydration in a conclusive model. The results indicate that at a lower water content the sulfonate group of the PFIA side chain is preferentially ionised and involved in a hydrogen bonding structure with the sulfonyl imide acid group, until a sufficient amount of water is present to ionise the second ionic site. Comparison to the well-understood NAFION™ membrane revealed that under low humidity conditions a higher amount of water is retained in PFIA in a state most similar to liquid water. The results contribute to a better understanding of water retention capability and thus proton conductivity under high-temperature and low-humidity conditions.

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Section: Acidic Formsmentioning

confidence: 97%

Section: Acidic Formsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Infrared dynamics study of thermally treated perfluoroimide acid proton exchange membranes

Puškar

Ritter

Schade

et al. 2017

Phys. Chem. Chem. Phys.

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“…An ab initio study of proton dissociation and the energetics of proton transfer is presented in Ref. 68 for three 3M ionomers with multi-acid side-chains including PFIA.…”

mentioning

confidence: 99%

Molecular Dynamic Study of Water-Cluster Structure in PFSA and PFIA Ionomers

Atrazhev

Astakhova

Sultanov³

et al. 2017

J. Electrochem. Soc.

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Molecular-dynamics simulations were used to study the structure of water clusters in different perfluorinated ionomers. The ionomers included in this work were Perfluorosulfonic Acid (PFSA) and Perfluoroimide Acid (PFIA). Different shapes and sizes of water domains in PFSA and PFIA were observed. In PFSA, ionomer water domains have spherical-like shape while water domains have complicated branch structure in PFIA ionomer. The mean water-cluster size for PFSA and PFIA ionomers as a function of water content lie on one universal curve, which indicates that the size of water clusters depends primarily on water content and weakly on ionomer chemistry. In PFSA, almost all hydronium ions are located predominantly close to the water cluster/backbone interface for both large and small values of water content; while in PFIA a relatively large fraction of hydronium ions are distributed within the bulk of the water clusters. A similar distribution of acidic groups was observed in both ionomers. In PFSA ionomer, all sulfonic groups are located in the surface water layer at the distance from 3 Å to 6 Å from the backbone. In PFIA ionomer, approximately 60% of sulfonic groups are located in the surface water layer and 40% of sulfonic groups are immersed into the bulk of water cluster. Perfluorinated ion-exchange membranes are widely used in both fuel cells and flow-battery cells. Flow batteries, such as vanadium redox batteries (VRBs), are promising devices for the large-scale Electrical Energy Storage (EES) applications 1 and are receiving increasing interest due to the demand for grid-scale EES solutions and recent improvements in VRB cell performance.2 The ion-exchange membrane is a critical component in these different types of electrochemical flow cells, which conducts the charge-carrier ions (e.g., protons) while preventing the flow of electrons through it. Additionally, in a flow-battery cell, the membrane separates the positive and negative liquid electrolytes containing the active redox-species ions. For example, in a VRB cell, it is desirable to prevent the crossover of vanadium ions through the membrane since the result is a decrease in both the energy efficiency and energy capacity of the VRB system. 2,3 In VRBs, this energy-capacity loss is recoverable, since the vanadium can be simply rebalanced by pumping some of the electrolyte with the excess V to the other electrolyte tank (albeit with an additional energy loss due to self-discharging that results from mixing the two reactants). In flow-battery chemistries with dissimilar active-species ions (e.g., Fe-Cr systems), crossover can also cause contamination of the electrolytes and/or electrodes, which can result in additional adverse effects on the flow-battery system. 1 In any case, the activespecies ions are transported through the membrane in the hydrophilic phase (i.e., the water clusters) of the membrane. Therefore, the study of the water-cluster structure is required to understand and model the transport of different ions in the membrane. One of the ultimate...

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“…However, they reported the dissociation of second proton on ortho-acid required more water, due to localization of charge and hydrogen bonding. Moreover, authors claimed that the electron withdrawing groups played dual role, as promoters of the proton dissociation by delocalizing electrons around proton donating acid groups, and by allowing the development of a hydrogen bond network, that readily adjusts for the transfer of charge at low hydration levels [118]. Kurniawan and co-workers [119] investigated the durability of Nafion-hydrophilic-silica hybrid membrane using B3LYP and 6- …”

Section: Dft Modelsmentioning

confidence: 99%