Diagnostic Criteria for the Characterization of Quasireversible Electron Transfer Reactions by Cyclic Square Wave Voltammetry

Mann, Megan A.; Helfrick, John C.; Bottomley, Lawrence A.

doi:10.1021/ac501550j

Cited by 25 publications

(38 citation statements)

References 22 publications

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“…[9][10][11][12][13][14] In the following sections, we present the results of our simulations in a similar fashion, first considering the impact of the chemical reaction rate on the shape of the voltammogram and then individually examining the impact of the each empirical parameter. We conclude with a set of instructions on how to identify an electrode reaction as an ECE mechanism and determining k f from empirical data.…”

Section: Resultsmentioning

confidence: 99%

“…[9][10][11][12][13][14] In this work, we critically evaluate CSWV for the analysis of consecutive electron transfers coupled by a homogeneous irreversible chemical reaction, i.e. an ECE mechanism.…”

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confidence: 99%

“…36 To compute theoretical voltammograms for CSWV, we employed the cyclic waveform and empirical parameters available with current commercial electrochemical instrumentation capable of CSWV as delineated in our previous reports. [9][10][11] The final equations used to compute theoretical voltammograms are:…”

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confidence: 99%

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Diagnostic Criteria for Identifying an ECE Mechanism with Cyclic Square Wave Voltammetry

Mann

Helfrick

Bottomley

2015

J. Electrochem. Soc.

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Theory for cyclic square wave voltammetry of an irreversible first-order chemical reaction coupling two electron transfers, i.e. an ECE mechanism, is presented. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. Note that the results presented herein are applicable only to ECE processes where E 0 for the second electron transfer step is negative of that for the first. Under this condition, disproportionation reactions do not occur. From the trends obtained, diagnostic criteria for this mechanism were deduced. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure reaction kinetics over the range −2 ≤ log k f ≤ 6. Square wave voltammetry (SWV) has been shown to be particularly useful in identifying electrode reaction mechanisms especially those involving chemical reactions coupled to the electron transfer step.1-7 Although a strong theoretical basis exists, 8 the use of SWV for identifying electrode reaction mechanisms has been limited to a small number of electrochemists. Our goal is to broaden the use of SWV for determining electrode reaction mechanisms especially by nonexperts in electrochemistry who make occasional use of voltammetry in characterizing new compounds. Cyclic square wave voltammetry (CSWV) is a modified form of SWV that steps through the region of the formal potential of the electroactive species under study and back to the initial potential as shown in Fig. 1a. The empirical parameters that comprise the CSWV waveform are period (τ), amplitude (E sw ), increment (δE), and the potential at which the direction of the sweep is reversed (E λ ).Our current effort is focused on identifying the specific mechanisms CSWV provides a straightforward means for determining the mechanism and associated kinetic parameters. [9][10][11][12][13][14] In this work, we critically evaluate CSWV for the analysis of consecutive electron transfers coupled by a homogeneous irreversible chemical reaction, i.e. an ECE mechanism. The process used to evaluate CSWV is as follows. Theoretical voltammograms were computed by systematic variation of each empirical parameter. Figures of merit that describe the shape of the voltammogram as shown in Fig. 1b (peak potentials, peak currents, and peak widths) were compiled and correlated with the empirical parameter being varied. Trends characteristic of this mechanism were identified from these correlations and provide diagnostic criteria for assigning an electrode reaction as an ECE process. Application of these criteria will enable non-specialists to accurately assign the mechanism and, in many instances, quantify the rate constant of the chemical reaction.The ECE mechanism has been the subject of considerable interest by electrochemists over the past five decades. [2][3][4][15][16][17][18][19][20][21][22][23][24] The continuing interest reflects: (1) the challenge in mathematically modeling the...

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Section: Resultsmentioning

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Diagnostic Criteria for Identifying an ECE Mechanism with Cyclic Square Wave Voltammetry

Mann

Helfrick

Bottomley

2015

J. Electrochem. Soc.

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“…Also, by fitting of experimental values of the forward and reverse peak currents and the peak position, the simultaneous determination of g and E 0 0 app is possible. Note that different magnitudes of the forward and reverse peaks are also predicted when the electrode process is not fully reversible [46]. These two situations (non-reversible electron transfer vs unequal diffusion coefficients) can be discriminated attending to the value of the half-peak width of the SWV peak that, as discussed above, is described with small error by Eq.…”

Section: Resultsmentioning

confidence: 88%

Effects of Unequal Diffusion Coefficients and Coupled Chemical Equilibria on Square Wave Voltammetry at Disc and Hemispherical Microelectrodes

Olmos

Molina

Laborda

et al. 2015

Electrochimica Acta

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“…In the recent years we have made an attempt to develop such methods under conditions of square-wave voltammetry (SWV) [5], which was achieved by the virtue of the SW amplitude, inspecting the influence of the amplitude variation to the current [2] or position [3] of the voltammetric response. In a broader context let us note that the latter methods are only a small fraction of a plethora of novel studies of merit dedicated to the methodological and theoretical development of SWV [6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Characterizing electrode reactions by multisampling the current in square-wave voltammetry

Mirčeski

Guziejewski

Bozem

et al. 2016

Electrochimica Acta

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A B S T R A C TA novel and simple methodology for characterization of electrode processes by square-wave voltammetry (SWV), considered as a complex repetitive double-step chronoamperometric experiment, is proposed. Specifically, the sampling of the current at the very end of each potential pulse, as common in conventional SWV, is replaced with a multisampling protocol during each potential pulse, resulting in generation of a series of corresponding multisampled SW voltammograms constructed out of a single measurement. The evolution of such voltammograms reflects the chronoamperometric properties of the current in the course of each potential pulse, thus being specific to electrode mechanism and electrode kinetics. The proposed methodology could serve as a basis for modification of common SWV mode in commercially available instrumentation for the purpose of an advanced characterization of electrode processes. The methodology is theoretically illustrated by the analysis of three kinetically controlled common electrode mechanisms, such as the electrode reaction of a solution resident and surface confined redox couples, as well as the regenerative catalytic electrode mechanism (EC'), while the experimental verification is done with the electrode reaction of Eu 3+ /Eu 2+ and azobenzene/ hydrazobenzene redox couples.

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Diagnostic Criteria for the Characterization of Quasireversible Electron Transfer Reactions by Cyclic Square Wave Voltammetry

Cited by 25 publications

References 22 publications

Diagnostic Criteria for Identifying an ECE Mechanism with Cyclic Square Wave Voltammetry

Diagnostic Criteria for Identifying an ECE Mechanism with Cyclic Square Wave Voltammetry

Effects of Unequal Diffusion Coefficients and Coupled Chemical Equilibria on Square Wave Voltammetry at Disc and Hemispherical Microelectrodes

Characterizing electrode reactions by multisampling the current in square-wave voltammetry

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