Determination of the heterogeneous electron-transfer rate constants for the redox couples Mo(CN)8, W(CN)8, Fe(CN)6, Os(CN)6 and IrCl6 using fast sweep cyclic voltammetry at carbon fibre electrodes

Oyama, Noboru; Ohsaka, Takeo; Yamamoto, Nobushige; Matsui, Junichiro; Hatozaki, Osamu

doi:10.1016/0022-0728(89)80198-6

Cited by 34 publications

(9 citation statements)

References 37 publications

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“…With a glassy carbon disk as the working electrode, the oxidative wave of the first CV scan was typically distorted, but after further cycling of the potential, the electrode response became highly reversible and reproducible over several hours. As noted previously, k el 0 values for Mo(CN) 8 3-/4- in the literature vary widely with the medium and the nature of the electrode; ,− nevertheless, it should be noted that k el 0 was found to be markedly faster in Et 4 NCl at glassy carbon than in NaClO 4 at gold (Table ). The pressure dependences of E 1/2 and ln k el were linear within the experimental uncertainty, 0−200 MPa (Supporting Information, Figures S1 and S2), and the corresponding values of Δ V Ag/AgCl and Δ V el ⧧ from replicate runs are given in Tables and .…”

Section: Resultsmentioning

confidence: 73%

“…Comparison of E 1/2 from CVs with the peak potential from the ACVs 1,2 showed that the transfer coefficient α was 0.50. For 1.51 mmol L -1 K 4 Os(CN) 6 in 0.61 mol L -1 KCl, k el 0 (the value of k el at ambient pressure) was 0.0194 cm s -1 at glassy carbon and 0.035 cm s -1 at Pt; Oyama et al used CV peak separation to obtain k el 0 = 0.15 ± 0.11 cm s -1 at a carbon fiber microelectrode for a different, highly acidic medium (0.1 mol L -1 CF 3 COONa + 0.1 mol L -1 CF 3 COOH) in which the electroactive hexacyanoosmate species would have been protonated . The pressure dependences of E 1/2 and ln k el were linear within the experimental uncertainty over the range 0−200 MPa, as shown in Figures and , and the corresponding values of Δ V Ag/AgCl and Δ V el ⧧ are given in Tables and , respectively.…”

Section: Resultsmentioning

confidence: 99%

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Electrochemical Kinetics of Cyanometalate Complexes in Aqueous Solution at High Pressures

Swaddle

1999

Inorg. Chem.

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For the aqueous couples Os(CN)(6)(3-/4-), Mo(CN)(8)(3-/4-), and W(CN)(8)(3-/4-), volumes of reaction DeltaV(Ag/AgCl) relative to Ag/AgCl/4.0 mol L(-)(1) KCl and volumes of activation DeltaV(el)() for the electrode reactions are reported. Values of DeltaV(Ag/AgCl) are consistent with a very small increase in the metal-carbon bond length on reduction in each case, the main component of DeltaV(Ag/AgCl) (other than that of the reference electrode) being electrostrictive solvation change. For media in which the cation is 0.5 mol L(-)(1) K(+) or (for Mo) Na(+), DeltaV(el)() is strongly positive (+9.4 +/- 0.7, +7.3 +/- 0.7, and +10.8 +/- 0.4 cm(3) mol(-)(1) for Os(CN)(6)(3-/4-), Mo(CN)(8)(3-/4-), and W(CN)(8)(3-/4-), respectively, at 25 degrees C), whereas the theoretical expectation for a mechanism involving only the cyanometalate anions is -3 +/- 1 cm(3) mol(-1). For Mo(CN)(8)(3-/4-) in Et(4)NCl, however, DeltaV(el)() is -4.2 +/- 0.2 cm(3) mol(-)(1). In all cases, DeltaV(el)() is just one-half of the corresponding parameter DeltaV(ex)() for the homogeneous (bimolecular) self-exchange reaction of the same couple, giving strong confirmation of the "fifty-percent rule" (Fu, Y.; Swaddle, T. W. J. Am. Chem. Soc. 1997, 119, 7137). These and related results are interpreted in terms of a mechanism for both electrode and homogeneous electron-transfer reactions of cyanometalates in which the counterion mediates the electron-transfer process. For alkali metal cations, partial deaquation to permit this mediation results in positive DeltaV(el)() values, whereas for tetraalkylammonium counterions, there are no aqua ligands to be removed and DeltaV(el)() is "normal".

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Section: Resultsmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Electrochemical Kinetics of Cyanometalate Complexes in Aqueous Solution at High Pressures

Swaddle

1999

Inorg. Chem.

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“…0.787 AE 0.002 0.79 AE 0.04 [24] 1,1'-ferrocenedicarboxylic acid (FDCA) 0.433 AE 0.019 - with increasing r in and r with slopes of % 9.2 10 À4 and % 1.8…”

Section: à3mentioning

confidence: 99%

“…It can be said again that I L is controlled by r rather than by r in . On the other hand, the limiting current I L,0 at V f = 0 also increased almost linearly [Fe(CN) 6 ] 4À 0.658 AE 0.005 0.639, [23] 0.61 AE 0.01 [24] I À 1.70 AE 0.02 1.99 [23]…”

Section: Cell Geometries and Volumetric Flow Rate Dependencementioning

confidence: 99%

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Limiting Current in a Flowing‐Electrolyte‐Type Droplet Cell

et al. 2009

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To the limit: Electrolyte flow accelerates the mass-transfer process in a droplet cell (see picture). The limiting current in the cell is expressed as a sum of hydrodynamic and stagnant terms. The current derived from the latter term indicates that convective mass transfer in the cell would be changed dramatically at a significantly small volumetric flow rate. Convective mass transfer in a flowing-electrolyte-type droplet cell (f-DC) is investigated for quantitative analysis of an electrode process and precise electrofabrication of microstructures using this device. The limiting current in the f-DC was expressed theoretically and its practical equation is investigated experimentally by cyclic voltammetry in solutions containing a redox mediator. The limiting-current equation in the f-DC derived experimentally could be expressed as a sum of hydrodynamic and stagnant terms. The current derived from the latter term of the f-DC is ten times larger than that in a conventional stagnant cell, thus indicating that the convective mass transfer in the cell would be changed dramatically at a small volumetric flow rate.

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Ultrafast Electrochemical Techniques

Forster

2000

Encyclopedia of Analytical Chemistry

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Ultrafast electrochemical techniques provide information about the kinetics and thermodynamics of redox processes that occur at submillisecond or even nanosecond timescales. This short timescale is achieved either by making very rapid transient measurements or by using ultrasmall probes to achieve very high rates of diffusion under steady‐state conditions. Microelectrodes (i.e. electrodes with critical dimensions in the micrometer range) play pivotal roles in both approaches. Electrochemistry has several advantages over spectroscopy in that it provides direct information about electron transfer (E) and coupled chemical (C) reactions. Ultrafast electrochemical techniques now allow it to do so at times as short as 10 ns. In transient measurements, decreasing the lower accessible timescale depends critically on fabricating ultramicroelectrodes that continue to respond ideally as their critical dimension (e.g. the radius of a microdisc) decreases. It is now possible to assemble microelectrodes that respond to changes in applied potential within less than a few nanoseconds. In steady‐state approaches, ultrasmall probes are required to make short timescale measurements and various approaches that yield nanodes (i.e. electrodes of nanometer dimension) have been proposed. However, beyond the need for smaller probes and faster instrumentation, the continued development of new theory describing electron transfer is essential, where the dimensions of the zone that is depleted of reactant because of a Faradaic reaction and the electrochemical double layer become comparable.

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Determination of the heterogeneous electron-transfer rate constants for the redox couples Mo(CN)8, W(CN)8, Fe(CN)6, Os(CN)6 and IrCl6 using fast sweep cyclic voltammetry at carbon fibre electrodes

Cited by 34 publications

References 37 publications

Electrochemical Kinetics of Cyanometalate Complexes in Aqueous Solution at High Pressures

Electrochemical Kinetics of Cyanometalate Complexes in Aqueous Solution at High Pressures

Limiting Current in a Flowing‐Electrolyte‐Type Droplet Cell

Ultrafast Electrochemical Techniques

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