First‐ and Second‐Order Derivative Polarography/Voltammetry for Reversible, Quasi‐Reversible, and Irreversible Electrode Processes

Abstract

New methods for analysis of current‐potential curves in terms of their derivatives are suggested for studies of heterogeneous electron‐transfer reactions. Consequences of the Butler‐Volmer theory on the shape of the derivatives are illustrated. Comparisons are made between fast and slow electron‐transfer reactions for various values of the standard heterogeneous rate constants false(k0false) and the transfer coefficient (α) utilizing asymmetries found in the peak shapes of the derivatives from a dc polarogram. Various parameters which characterize the peak asymmetry (such as ratios of peak‐currents and ratios of peak‐widths) are evaluated and analyzed. They are symmetrical for a reversible process, while they become asymmetrical for slower heterogeneous kinetic systems. It is shown that α for irreversible processes can be directly determined from measurements of peak‐widths or peak‐separations of derivatives. Simultaneous determination of the heterogeneous kinetic parameters ( k0 and α) for several systems is accomplished by fitting the theoretical derivative equation to the experimental data which are obtained with a moving‐window‐smoothing/differentiation method. The results agree well with those obtained with other methods such as dc, ac, semi‐integral, differential pulse polarography, and square‐wave voltammetry.

The Restructuring-Induced CoOx Catalyst for Electrochemical Water Splitting

“… 16 The first cycle CV curve also exhibits a pronounced irreversible feature as the integrated area of the anodic peaks (positive current values) at voltages less than 1.4 V was much larger than that of the cathodic peaks (negative current values), suggesting the oxidation of the Co 9 S 8 catalyst ( Figure 1 a). In addition, by investigating the second derivation of the curve, 17 , 18 the anodic band at 1.15–1.4 V has two peaks at 1.27 and 1.31 V ( Figure S1a,b ), which could be due to the change of the coordination environments for cobalt atoms. Compared to the first cycle, the integrated area of anodic peaks for the following second to fifth cycles is much smaller ( Figure 1 b), and the 1.05 V anodic peak in the first cycle disappeared, which also indicates an irreversible change in the Co 9 S 8 films.…”

Intramolecular Electron Transfer in Pentaammineruthenium(III)-Modified Cobaltocytochrome c

“…The effect of the slow heterogeneous electron transfer rate is to displace the apparent peak potential in a cathodic scan to a more negative value with respect to the fast, reversible case. A theoretical treatment of the effects of quasi-reversible and irreversible behavior on polarograms was recently published by Kim et al 26 Work on quantification of the quasi-reversibility of the CoCyt c couple is continuing. Our measurements are consistent with Chien's result; we will use the potentiometric titration value of -0.14 ( 0.02 V vs NHE in subsequent calculations.…”

Interrupted amperometry: An ultrasensitive technique for diffusion current measuring

“…Currents produced by discharge of electroactive impurities are significantly lower than those produced by discharge of the analyte in the fixed potential region. 6. Potentiostat transition time is significantly shorter than the circuit locking time.…”

“…The great variety of approaches to enhancing the signal-to-noise ratio can be roughly divided into two groups -mathematical and instrumental methods. Various mathematical techniques, such as derivative voltammetry [5][6][7][8], Fourier [9][10][11][12] and wavelet [13][14][15] transformations, effectively eliminate noise-like signals thus improving sensitivity and resolution. However, these methods operate with experimentally collected data and don't improve the analytical signal physically.…”