Randles–Sevcik Equation Calculator

Welcome to our Randles-Sevcik equation calculator, where you'll be able to calculate any of the variables of that formula.

Of course, the Randles-Sevcik equation units are interchangeable, and you can, for example, use meters instead of centimeters as long as you keep dimensional homogeneity.

The calculation of this equation has different applications:

• As we'll see in the next section, the calculation of the Randles-Sevcik equation can help us distinguish whether an analyte is freely diffusing or absorbed in an electrode.
• We can also use the Randles-Sevcik equation to find the diffusion coefficient of the oxidized analyte.
• If we want to know if our electrochemical process is irreversible, the Randles-Sevcik equation can give insights into that: you will learn how the Randles-Sevcik plot describes such processes.

If you're interested in other handy tools from chemistry, our fret efficiency calculator offers a quick estimation of the resonance energy transfer efficiency and critical distance from the spectral overlap and other known parameters.

Electrochemistry is the branch of physical chemistry that, using electrodes, studies the relationship between chemical reactions and electricity. Within this branch, we can find different methods to perform that study: voltammetry is the most common one, in which we study current as a function of applied potential in the electrodes. This current-voltage relationship is represented using a graph called voltammogram.

We can find different types of voltammetry, but we will focus on the cyclic voltammetry. In cyclic voltammetry, we apply an increasing and decreasing cyclic potential over time, as in the following image:

The voltammogram generated in this process is called cyclic voltammogram and typically has this form:

As long as the process is reversible and involves freely diffusing redox species, the previous plot will correspond to the Randles-Sevcik equation.

The calculation of the Randles-Sevcik equation applies only to reversible processes. To be more precise, this equation is valid for electrochemically reversible electron transfer processes that involve freely diffusing redox species.

As you can note from the equation, the Randles-Sevcik plot of $i_{\text{p}}$ vs. $v^{1/2}$ should be linear, and a deviation from this linearity can indicate two things:

1. Electrochemical quasi-reversibility.
2. Electron transfer occurs not via free diffusion but through surface-absorbed species.

The following one is the Randles-Sevcik equation and its units

where:

• $A$ — Electrode surface area (cm²);
• $C^0$ — Bulk concentration of the analyte (mol/cm³);
• $n$ — Number of electrons transferred in the redox event;
• $F$ — Faraday's constant (C/mol);
• $v$ — Scan rate (V/s);
• $D_0$ — Diffusion coefficient of the oxidized analyte (cm²/s);
• $R$ — Ideal gas constant (J/(mol K)); and
• $T$ — Absolute temperature (K).