How Much Supporting Electrolyte Is Required to Make a Cyclic Voltammetry Experiment Quantitatively “Diffusional”? A Theoretical and Experimental Investigation

Dickinson, Edmund J. F.; Limon-Petersen, Juan G.; Rees, Neil V.; Compton, Richard G.

doi:10.1021/jp901628h

Cited by 163 publications

(184 citation statements)

References 30 publications

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“…As with the data in Figure 2 and Figure S1, these would all, again, be regarded as reasonable concentrations of redox-active species and ratios of electrolyte to redox-active species concentration in conventional cells. 67 However, as with the data in Figure 1 and Table 1, these results highlight the need to use rather extreme electrolyte to redox-active species concentrations in dropletcell kinetic measurements, and the importance of RE and CE placement. In order to diminish the dependence of the voltammetric response on the cell configuration, a larger concentration of supporting electrolyte, 1 M KCl (instead of 0.1 M), was used for the kinetic measurements herein, since this increases the conductivity of the solution by approx.…”

Section: Assessment Of Ohmic Loss Of Potentialsupporting

confidence: 63%

Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models

Zhang

Cuharuc

Güell

et al. 2015

Phys. Chem. Chem. Phys.

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Original citation:Zhang, Guohui, Cuharuc, Anatolii S., Güell, Aleix G. and Unwin, Patrick R.. (2015) Electrochemistry at highly oriented pyrolytic graphite (HOPG) : lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models. Physical Chemistry Chemical Physics (Number 17). pp. 11827-11838. Permanent WRAP url: http://wrap.warwick.ac.uk/67805 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-forprofit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher statement:First published by Royal Society of Chemistry 2015 http://dx.doi.org/10.1039/C5CP00383K A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. This simple configuration allows measurements to be made on a very short time scale after cleavage of HOPG, so as to minimise possible effects from (atmospheric) contamination, and with minimal, if any, change to the HOPG surface. However, the droplet-cell geometry differs from more conventional electrochemical setups and is more prone to ohmic drop effects. The magnitude of ohmic drop is elucidated by modelling the electric field in a typical droplet configuration. These simulations enable ohmic effects to be minimised practically by optimising the positions of the counter and reference electrodes in the droplet, and by using a concentration ratio of electrolyte to redox species that is higher than used conventionally . It is shown that the ET kinetics for all of the redox species studied herein is fast on all grades of HOPG and lower limits for ET rate constants are deduced. For IrCl 6 2-/3-and Fe(CN) 6 3-/4-, ET on HOPG is at least as fast as on Pt electrodes, and for Ru(NH 3 ) 6 3+/2+ ET kinetics on HOPG is comparable to Pt electrodes. Given the considerable difference in the density of electronic states (DOS) between graphite and metal electrodes, the results tend to suggest that the DOS of the electrode does not play an important role in the ET kinetics of these outer-sphere redox couples over the range of values encompassing HOPG and metals. This can be rationalised because the DOS of all of these different electrode ma...

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Section: Assessment Of Ohmic Loss Of Potentialsupporting

confidence: 63%

Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models

Zhang

Cuharuc

Güell

et al. 2015

Phys. Chem. Chem. Phys.

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“…The interfacial tension between the kerosene and water phases slightly increases in the presence of salts 39 (typically by a few of mN m −1 ), i.e., the formation of the tip on the droplet surface at a charging electrode is more difficult and the electric charge is transferred from the electrode to the droplet through different surface area. Increased concentration of a supporting electrolyte also reduces the electromigration transport of the electrochemical reactants, 40 which changes the transport rates of these species during the charge/discharge process. It can be concluded that salt addition into the water droplet results in a complex change of system behavior.…”

Section: B Frequency Characteristicsmentioning

confidence: 99%

Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

et al. 2014

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We experimentally observed oscillatory motion of water droplets in microfluidic systems with coplanar microelectrodes under imposed DC electric fields. Two-electrode arrangement with no bipolar electrode and eight-electrode arrangement with six bipolar microelectrodes were investigated. Kerosene was used as the continuous phase. We studied the dependences of the oscillation frequency on the electric field intensity and ionic strength of the water phase. We found that the electric field dependence is strongly nonlinear and discussed possible reasons of this phenomenon, e.g., the droplet deformation at electrode edges that affects the charge transfer between the electrode and droplet or the interplay between the Coulomb force on free charge and the dielectrophoretic force. Our experiments further revealed that the oscillation frequency decreases with growing salt concentration in the two-electrode arrangement, but increases in the eight-electrode arrangement, which was attributed to surface tension related processes and electrochemical processes on the bipolar electrodes. Finally, we analyzed the effects of the electric field on the oscillatory motion by means of a simplified mathematical model. It was shown that the electric force imposed on the droplet charge is the key factor to induce the oscillations and the dielectrophoretic force significantly contributes to the momentum transfer at the electrode edges. For the same electric field strength, the model is able to predict the same oscillation frequency as that observed in the experiments.

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“…They also solved Poisson's equation, rather than assuming electroneutrality or implementing a displacement-current equation. Dickinson et al 60 subsequently modified the methodology of Streeter and Compton 59 to simulate CV of idealized single-electron transfer reactions at a hemispherical working electrode. Their model also assumed that the electrolyte was weakly to strongly supported and that no mass was transferred from the electrolyte to the electrode.…”

Section: Theorymentioning

confidence: 99%

“…This work builds upon the methodology of Dickinson et al 60 by extending the interfacial reaction model to account for the nucleation, growth, and dissolution of metal deposits, as well as the experimental Coulombic efficiency. The utility of the model is demonstrated by identifying parameter sets that are consistent with experimentally obtained CV data.…”

Section: Theorymentioning

confidence: 99%

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Computational Model of Magnesium Deposition and Dissolution for Property Determination via Cyclic Voltammetry

Chadwick

Vardar

DeWitt

et al. 2016

J. Electrochem. Soc.

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The development of a practical magnesium-anode battery requires electrolytes that allow for highly efficient magnesium exchange while also being compatible with cathode materials. Here, a one-dimensional continuum-scale model is developed to simulate cyclic plating/stripping voltammetry of a model magnesium-based electrolyte system employing magnesium borohydride/dimethoxyethane [Mg(BH 4 ) 2 /DME] solutions on a gold substrate. The model is developed from non-electroneutral dilute-solution theory, using Nernst-Planck equations for the mass flux and Poisson's equation for the electrostatic potential. The electrochemical reaction is modeled with multistep Butler-Volmer kinetics, with a modified current/overpotential relationship that separately accounts for the portions of the current responsible for nucleating new deposits and propagating or dissolving existing ones. The diffusivities of the electrolyte species, standard heterogeneous rate constant, charge-transfer coefficient, formal potential, and nucleation overpotential are determined computationally by reproducing experimental voltammograms. The model is computationally inexpensive and therefore allows for broad parametric studies of electrolyte behavior that would otherwise be impractical. A rechargeable magnesium battery was first demonstrated 25 years ago when Gregory et al. 1 showed that magnesium could be reversibly deposited onto and dissolved from a magnesium-metal surface, as well as intercalated into and deintercalated from various host cathodes. Further interest in secondary magnesium batteries arose following the work of Aurbach et al., 2 which demonstrated a highly efficient organohaloaluminate electrolyte using a magnesium anode and a Mo 6 S 8 Chevrel-phase cathode. As a battery anode, magnesium metal offers important advantages over both intercalation compounds and lithium metal, including a higher theoretical volumetric energy capacity (3833 mAh/cm 3 vs. 2046 mAh/cm 3 for lithium metal and 760 mAh/cm 3 for graphite-based lithium-ion anodes), as well as a higher abundance in the earth's crust.3 Additionally, magnesium is less prone to dendrite formation than lithium when electrodeposited and therefore offers potential for improved battery cycle life and safety. 4 In addition to high-capacity electrode materials, a practical magnesium battery will also require an efficient electrolyte that is compatible with (i.e., chemically stable in contact with) these electrodes. Compared to lithium electrolytes, magnesium electrolytes remain in a relatively early developmental stage.1-29 Electrolytes formulated from Grignard reagents have been widely studied both in the battery and general electrochemistry communities. 1,6,28,[30][31][32][33][34][35] The speciation of these electrolytes is complex because, in addition to ionic dissociation, the reagents also undergo the Schlenk equilibrium process (a type of ligand exchange) and form multimeric species in many solvents. Both organohaloaluminates and the so-called magnesium aluminum chloride complex (MACC) a...

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How Much Supporting Electrolyte Is Required to Make a Cyclic Voltammetry Experiment Quantitatively “Diffusional”? A Theoretical and Experimental Investigation

Cited by 163 publications

References 30 publications

Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models

Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models

Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

Computational Model of Magnesium Deposition and Dissolution for Property Determination via Cyclic Voltammetry

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