Abstract
Electrochemical simulations are presented to introduce students to the capabilities of cyclic voltammetry (CV). The systems chosen involve one and two-electron transfers, and can be delineated with CV as being reversible, quasi-reversible, or irreversible. The rate constants for the electron transfer can be estimated by the theory of Nicholson and Shain. DigiElch, professional® provides the opportunity of fitting experimental CVs after assuming a reaction scheme. We will demonstrate data fitting for two different mechanisms, electron transfer E and electron transfer followed by a chemical reaction with a subsequent electron transfer of the product ECE.
Highlights
Several factors are of interest when developing new electrochemical devices: cell thermodynamics as the electromotive force (EMF), the standard free enthalpy (∆G0) of the cell reaction, and the equilibrium constant (Kcell)
The current depends on the electrode potential when the electrode process is rate limiting: I=
Typical values are D ≈10-5 cm2 / s and t = 1s and d ≈ 50 μm. This means that diffusion in solution is a slow process. (The solution has to be stirred to prevent a diffusion-controlled electrochemical process.) Figure 2 shows a concentration profile at different potentials of the oxidised and reduced species in a one-electron transfer calculated by the electrochemical simulation and fitting program DigiElch Professional®
Summary
Several factors are of interest when developing new electrochemical devices: cell thermodynamics as the electromotive force (EMF), the standard free enthalpy (∆G0) of the cell reaction, and the equilibrium constant (Kcell). This means that a lot of energy is necessary to rearrange the sphere There is another process involved in the electrochemical reaction: the mass transport to or from the electrode. (The solution has to be stirred to prevent a diffusion-controlled electrochemical process.) Figure 2 shows a concentration profile at different potentials of the oxidised and reduced species in a one-electron transfer calculated by the electrochemical simulation and fitting program DigiElch Professional®. According to Eq (1), the concentration of the electroactive species c at the electrode surface is given by the potential E, the standard electrochemical rate constant k0, and the diffusion to and away from the electrode (Eq (4)).
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