Electrical conductivities of quaternary ammonium salts in acetone.: Part II. The mechanisms of transport

Adams, William A.; Laidler, Keith J.

doi:10.1139/v68-329

Cited by 10 publications

(7 citation statements)

References 18 publications

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“…Finally, making a similar comparison of the conductivity ratio of PSU-QA (OH -) and PPO-QA (Cl -), which is 1.8 at λ = 100, and the ratio of the ion mobility of hydroxide and chloride ions at infinite dilution (2.6 [57,58]), the difference might again be attributed to the would be about 30% lower for hydroxide than for chloride ions. This result is consistent with the effective ionic radii of chloride (181 pm [79]) and hydroxide ions (132 pm [79]) given that a lower ion radius increases the strength of ion pairs [80][81][82].…”

Section: Hydration Dependence Of the Ionic Conductivitysupporting

confidence: 85%

Effective ion mobility in anion exchange ionomers: Relations with hydration, porosity, tortuosity, and percolation

Knauth

Pasquini

Narducci

et al. 2021

Journal of Membrane Science

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The effective mobility of hydroxide, chloride and fluoride ions is reported in various anion exchange membranes (AEM) with a backbone of polysulfone (PSU) or poly(2,6-dimethyl-1,4-phenylene)oxide (PPO). The concentration dependence of the effective mobility is used to derive the porosity (π), tortuosity (τ), and percolation thresholds and to plot the ionic conductivity vs the hydration number. Semi-logarithmic plots of the effective ion mobility u(i) vs the square root of concentration √c(i) for hydroxide, fluoride and chloride ions in various PSU-and PPO-based ionomers at 25 and 60 °C show linear relations, from which the ratio π/τ can be determined. This existence of linear u(i)=f(√c(i)) plots is related to the very particular boundary conditions experienced by mobile ions, migrating in close vicinity to the immobile grafted counter-ions placed at the interfaces between polymer domains and electrolyte solution. The π/τ values for PSU-QA (0.29) and PPO-QA (0.38) are consistent with a relatively low hydrophilic-hydrophobic nanophase separation, which leads to channels with low diameter and high tortuosity. The tortuosity determined from a Bruggeman-type relation is 1.9 for PSU-QA and 1.6 for PPO-QA. The percolation thresholds , determined from the universal percolation equation near and above , are at a water volume fraction of 0.07 for PSU-TMA and 0.03 for PPO-QA indicating that these AEM have a two-dimensional structure of the hydrated domains. The prefactor, which should represent a good indication as to the maximum achievable ionic conductivity, is slightly below 100 mS/cm for both PSU-TMA and PPO-based ionomers. Plots of experimental and computed hydroxide and chloride ion conductivities as function of the hydration number () show a maximum ionic conductivity for a value of the hydration number around 60, corresponding to optimal hydration conditions. At λ = 100, the ratio of conductivity between PSU-QA (OH form) and PPO-QA (Cl form) indicates that the degree of dissociation of ion pairs is about 30% lower for hydroxide than for chloride ions, which is consistent with the effective ionic radii of Cl and OH -.

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Section: Hydration Dependence Of the Ionic Conductivitysupporting

confidence: 85%

Effective ion mobility in anion exchange ionomers: Relations with hydration, porosity, tortuosity, and percolation

Knauth

Pasquini

Narducci

et al. 2021

Journal of Membrane Science

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“…Figure 2a shows the evolution of n for the a The activation energy for the viscous flow, E a , was derived from an Arrhenius fit of the viscosity data in the temperature range 15−45 °C (Figure 1c and d). E a for liquid AC is close to previous data: 1.67(3) 74 and 1.70 75 The observed trend might be largely influenced by electrostriction effects regulating the changes of free volume in the solution: smaller volume for the solvent in the ion solvation shell than in the bulk. 36 Figure 2b illustrates the mole fraction dependence of the relative viscosity, η r (=η/η 0 , with η indicating the viscosity of the solution at a given x and η 0 the viscosity of the pure solvent), at 25 °C.…”

Section: Resultssupporting

confidence: 89%

Complex Dynamical Aspects of Organic Electrolyte Solutions

et al. 2013

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Molecular dynamics of acetone-alkali metal halide (LiBr, LiI) solutions were investigated using depolarized Rayleigh scattering (DRS) and low-frequency Raman spectroscopy in the frequency range from ~0.5 to 200 cm(-1) (~20 GHz to 6 THz). These experiments probe fast dynamical fluctuations of the polarizability anisotropy at picosecond and sub-picosecond time scales that are mainly driven by acetone orientational dynamics. Two distinct contributions were revealed: a fast process (units of picosecond, ps) related to the essentially unperturbed bulk solvent and a slow one (tens of ps) assigned to acetone molecules forming Li(+) solvation shells, decelerated by the motional constraint imposed by the cation. The increase of LiBr and LiI concentration significantly slows down the overall solvent relaxation as a consequence of the increased fraction of acetone molecules involved in the ion solvation shells. The global retardation is larger in LiI than LiBr solutions consistently with viscosity trends. This is explained in terms of ion association (at least ion pairing) more favorably promoted by Br(-) than I(-), with reduced Li(+)-acetone interactions in LiBr than LiI solutions. Anion-induced modulation of the Li(+)···O═C contacts, largely responsible for electrostriction phenomena, also affects the reduced THz-Raman spectral density, ascribed to ultrafast librational motions of acetone molecules. Overall, these findings enlighten the interplay between ion-dipole and ion-ion interactions on the fast solvation dynamics in electrolyte solutions of a typical polar aprotic solvent.

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“…The equation has yielded predicted values of conductances for PbCl2-PbBra and KNO3-NaNO3 melts which are ELECTRICAL CONDUCTANCE OF CARBONATE 1051 within +_ 2% of experimental data (26). The Markov equation follows directly from a consideration of the probability of interaction between pure salts in the mixture and the electrical conductance of such an arrangement within the melt.…”

Section: Discussionmentioning

confidence: 97%

“…Furthermore, the frictional formalism has not yielded sufficient insight into the mechanisms of transport" to warrant its inclusion in this discussion (24). Lack of necessary fundamental data for these salts did not allow the formal application to these data of the hole model as developed by Bockris et al (25) or the free volume approach of Laidler et al (26). However, estimates of the ionic radius (12), ion vibration (4), and jump distance for the pure alkali metal carbonates have allowed approximate calculations to be performed for the hole model, the results of which gave conductances of similar accuracy as those for univalent salts; that is the calculated Arrhenius coefficients were in reasonable agreement with experimental values but the absolute values were not.…”

Section: Discussionmentioning

confidence: 99%

Electrical Conductance of Molten Alkali Carbonate Binary Mixtures

Spedding

1973

J. Electrochem. Soc.

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The electrical conductances are reported for molten lithium, sodium, and potassium carbonate binary mixtures over the complete composition range. Molar concentration-equivalent conductance isotherms exhibit a negative deviation from ideal behavior. Attempts to handle the results by using conduction theories proved unsuccessful except in the case of the Markov equation. Calculations with the Markov equation gave values for the conduction of dissimilar interacting cations that indicated that the temperature dependence of the conduction is governed by the anion environment present, while the absolute value of conductance gives an indication of the ease of movement of the dissimilar interacting cations.The alkali metal carbonates have been subjected to extensive study over recent years primarily because of their possible practical application in electrochemistry. This present study was undertaken as part of an integrated fuel cell research program aimed at obtaining a better understanding of the actual processes taking place in the molten carbonate-type cell. ExperimentalMethc>ds which are used for measurement of electrical conduction of molten salts have been reviewed by a number of workers (1-5) who have concluded that the most accurate technique which is available for corrosive media is the capillary cell with the actual capillaries formed in noncorrosive insulating material (6-8). The technique therefore was used in this study. The actual apparatus employed is detailed in Fig. 1 and is similar to that of Janz and co-workers (9-10). Care was taken with the design and construction of the apparatus to ensure that the conduction path was entirely confined to the capillaries and the melt between their two immersed extremities. The capillaries were ultrasonically drilled in two single crystals of magnesium oxide. The salt bath was held in a Palau crucible (80% Au-20% Pd) in a controlled carbon dioxide atmosphere, in order to ensure the melt composition was unchanged during experimentation. The over-all details of the control and operation of the system have been presented elsewhere (11,12). Temperature was better than ___ 0.1 ~ at 800~The capillary cell was calibrated with aqueous KC1 solution at 25~ using standard techniques (13). Coefficient of expansion data (14) then were applied to the particular cell geometry employed to give the operating cell constant. The calibration was checked against molten KC1 data (15) at intervals during the entire work and was found to agree within • 0.002%. The cell constants for the various cells used during the determination were approximately 370 -1 cm in the operating temperature range used. Measurements were taken at approximately 20~ intervals at increasing and then at decreasing temperatures. During an actual measurement the furnace was switched off to avoid errors which arise because of interference from the furnace windings. The Jones bridge-oscillator-oscilloscope combination used to measure the conductance virtually eliminated any capacitance effects. Readings were taken ove...

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Electrical conductivities of quaternary ammonium salts in acetone.: Part II. The mechanisms of transport

Cited by 10 publications

References 18 publications

Effective ion mobility in anion exchange ionomers: Relations with hydration, porosity, tortuosity, and percolation

Effective ion mobility in anion exchange ionomers: Relations with hydration, porosity, tortuosity, and percolation

Complex Dynamical Aspects of Organic Electrolyte Solutions

Electrical Conductance of Molten Alkali Carbonate Binary Mixtures

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