Voltammetry at High Pressure

Ewald, A. H.; Lim, Seong-Bin

doi:10.1021/j150556a047

Cited by 10 publications

(10 citation statements)

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“…However, this was found to be in contradiction with the results of Lim [11] who investigated the same system at a stationary Pt microelectrode and found a significant decrease in the limiting current when the pressures increased up to 3 kbar. This discrepancy was attributed to the fact that DC polarization is always liable to give anomalous results when using long polarization times [24].…”

contrasting

confidence: 84%

“…It is therefore somewhat surprising that only a few studies describe the use of microdisk electrodes in high pressure electrochemical experiments [2,11,30,31,38,39,55,77].…”

Section: Microelectrodesmentioning

confidence: 99%

“…The use of microelectrodes at high pressures was first reported in 1957 by Ewald [11] who investigated the reduction of Cu 2 to Cu relative to a saturated calomel electrode in 0.5 M KCl up to 303 MPa. From the half-wave potential (which was found to be independent of concentration but was moved to a more negative value by an increase in pressure of 3 000 atm), the volume of reaction DV SCE for the cell was evaluated to be 23 AE 0.7 cm 3 mol À1 .…”

Section: Microelectrodesmentioning

confidence: 99%

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Electrochemistry at High Pressures: A Review

2004

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High pressure electrochemical studies are potentially dangerous and less immediately implemented than conventional investigations. Technical obstacles related to properties of the working electrode material, preparation of its surface, availability of suitable reference electrodes, and the need for specially designed high pressure equipment and cells may account for the relative lack of experimental data on electrochemistry at high pressures. However, despite the stringent requirements for system and equipment stability, significant developments have been made in recent years and the combination of electrochemical methods with high hydrostatic pressure has provided useful insights into the thermodynamics, kinetics, and other physico-chemical characteristics of a wide range of redox reactions. In addition to fundamental information, high pressure electrochemistry has also lead to a better understanding of a variety of processes under non-classical conditions with potential applications in today×s industrial environment from extraction and electrosynthesis in supercritical fluids to measurement of the pH at the bottom of the ocean. The purpose of this article is to detail the experimental pressurizing apparatus for electroanalytical measurements at high pressures and to review the relevant literature on the effect of pressure on electrode processes and on the properties of aqueous electrolyte solutions.

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contrasting

confidence: 84%

“…It is therefore somewhat surprising that only a few studies describe the use of microdisk electrodes in high pressure electrochemical experiments [2,11,30,31,38,39,55,77].…”

Section: Microelectrodesmentioning

confidence: 99%

Section: Microelectrodesmentioning

confidence: 99%

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Electrochemistry at High Pressures: A Review

2004

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“…For our present purposes, however, the most important consideration is that the pressure dependences of the kinetics of the self-exchange reactions of all four couples have been reported (1)(2)(3)(4)(5)(6) and the use of those data together with the present results in testing the applicability of the Marcus "cross 'To whom all correspondence should be addressed coming article. A variety of approaches to measurements of electrode phenomena at high pressures have been reported (5,6,(8)(9)(10)(11)(12)(13)(14)(15). We have found cyclic voltammetry to be well suited for the measurement of electrode potentials Ep as functions of the pressure P (12,13); however, our attempts to obtain kinetic information from a combination of cyclic and AC voltammetry (16) gave inconsistent results under pressure, and are reported only in outline here.…”

Section: Introductionmentioning

confidence: 91%

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Doine¹,

Whitcombe²,

Swaddle³

1992

Can. J. Chem.

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The dependences of the electrode potentials E of aqueous Fe(H20);+/'+, ~e(~hen),)+/'+, F~(cN)~)-/"-, and ~o ( s e~) ' + / ' + upon pressure P (up to ca. 200 MPa) have been measured at 25.0°C relative to an AgCl/Ag(satd. KCI) electrode by cyclic voltammetry. For ~o ( s e~)~+ / ' + at ionic strength I = 0.28 and 1.00 rnol kg-', (dE/dP), is independent of P as well as I, giving a volume of reaction AV = + 13.7 ? 0.4 cm3 mol-' relative to AgCl/Ag; similarly, for F~( H~o ) ; + /~+ at I = 0.28 rnol kg-' (CF3S03H), AV = +5.0 * 0.3 cm3 mol-'. For F~(cN);-/~-in KC1 media, (dE/dP), is independent of P and I at I = 0.28 and 0.51 rnol kg-', giving AV = -36.1 ? 1.0 cm3 mol-', but shows some slight dependence on P at I = 1.00 rnol kg-' (low-pressure limit AVO = -38 * 1 cm3 mol-'; (dAV/dP), = +0.030 cm3 mol-' MP~-I).For ~e (~h e n )~~+ / ' + , (dE/dP), is markedly pressure and medium dependent, with AVO = +14.2 ? 0.5 and +6.2 ? 0.5 cm3 mol-' in KNO, media at I = 0.25 and 1 . OO rnol kg-', respectively. The peak-to-peak separation of the cyclic voltammograms increases with increasing P for Fe(cN)$-I4-, but decreases slightly for the cationic couples; these trends can be accounted for in terms of the volumes of activation for the corresponding self-exchange reactions.

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“…We now report in full the results of high pressure electrochemical kinetic studies of ten aqueous self-exchange reactions, for which values of Δ V ex ⧧ are available, that confirm that eq 4 holds with remarkable precision, despite a very poor correlation between ln k el and ln k ex . High pressure studies of redox phenomena at electrodes are not common, − and reports of high-pressure kinetic measurements are particularly sparse, ,− probably because of problems with reproducibility due to contamination of electrodes in high-pressure equipment. We describe here procedures that yield reliable values of k el and Δ V el ⧧ from AC voltammetry.…”

Section: Introductionmentioning

confidence: 99%

Relationship between Heterogeneous and Homogeneous Kinetics of Electron Transfer between Transition Metal Complexes in Aqueous Solution: Volumes of Activation

and

Swaddle

1997

J. Am. Chem. Soc.

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Electrochemical rate constants k el and volumes of activation ΔV el ⧧ for self-exchange at an electrode of the aqueous couples Co(phen)3 3+/2+, Co(en)3 3+/2+, Fe(H2O)6 3+/2+, Co(diamsar)3+/2+, Co(diamsarH2)3+/2+, Co(sep)3+/2+, Co(ttcn)2 3+/2+, Fe(phen)3 3+/2+, Mo(CN)8 3-/4-, and Fe(CN)6 3-/4- have been measured by high-pressure AC voltammetry over the range 0.1−200 MPa at 25 °C; the respective values of ΔV el ⧧ are −9.1, −8.3, −5.5, −3.5, −3.8, −3.0, −2.8, −1.6, +7.3, and +11 cm3 mol-1. Although the theory of Marcus (Electrochim. Acta 1968, 13, 1005) suggests that ln k el should be linearly related to 1/2 ln k ex, where k ex is the rate constant of the corresponding homogeneous (bimolecular) self-exchange reaction, ln k el is often sensitive to the nature of the working electrode and the supporting electrolyte and is only weakly correlated with ln k ex, with slope ≈0.1. In contrast, ΔV el ⧧ = (0.50 ± 0.02)ΔV ex ⧧, in precise agreement with an extension of Marcus' theory, regardless of the nature of the electrode and the supporting electrolyte. This result implies that electron transfer in these couples occurs adiabatically on direct ion−ion and ion−electrode contact (i.e., within the outer Helmholtz plane), and also that ΔV el ⧧ values are predictable in the manner described elsewhere (Can. J. Chem. 1996, 74, 631) for ΔV ex ⧧. Conversely, where ΔV ex ⧧ cannot be measured for technical reasons (e.g., where paramagnetism of both reactants precludes NMR measurements of k ex), it can be reliably estimated as 2ΔV el ⧧.

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Voltammetry at High Pressure

Cited by 10 publications

References 0 publications

Electrochemistry at High Pressures: A Review

Electrochemistry at High Pressures: A Review

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Relationship between Heterogeneous and Homogeneous Kinetics of Electron Transfer between Transition Metal Complexes in Aqueous Solution: Volumes of Activation

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