Simulations of Cyclic Voltammetry Data
- To become familiar with DigiElch electrochemical simulation software
- To learn about different reaction mechanisms that can be studied using cyclic
- To extract kinetic parameters from cyclic-voltammetry data using DigiElch
- DigiElch electrochemical simulation software installed and running on a Windows®PC
- DigiElch license
- Sample cyclic voltammetry data found in the My Gamry Data folder in Echem Analyst™
Mechanisms that Control Current
Electrochemical systems can be complicated. They often include more than one redox pair in solution; there can be reactions that alter the electrode surface (e.g., platinum forming a platinum oxide layer); and solution species can alter reaction products as they form. Kinetics of electrochemical reactions can further complicate matters.
Theoretically all electrochemical reactions have a kinetics limit that controls how fast the reaction can occur. In many systems, the electrochemical kinetics are fast enough that every atom or molecule that reaches the electrode surface reacts instantaneously. In these systems, the concentration of the reactant at the electrode surface falls to zero: cell current only depends on the rate at which reactants can reach the electrode. Generally, diffusion is the mechanism that transports a reactant through the solution, so these systems are often called diffusion-controlled or mass-transport controlled. Almost all of the experiments in this laboratory manual involve this type of electrochemical system.
In other systems, the electrochemical reaction is slow enough that the concentration of reactant at the electrode surface is not zero. When this occurs, the concentration gradient that drives diffusion is less steep. The observed current is always smaller than that predicted under diffusion control. These systems are often called kinetically controlled. The corrosion experiments are run on a kinetically controlled system.
Regardless of the mechanism that limits the cell current, the cell current is always proportional to the flux of material at the electrode surface (Fick’s Law).