# Concept of Limiting Current

I am investigating the current output from an electrochemical cell. The electrochemical cell can be broken down into several stages, for example:

1. Diffusion of reactants across a capillary
2. Diffusion in aqueous electrolyte
3. Adsorption and desorption at the electrode
4. Current generated due to anodic and cathodic though the Butler-Volmer Equation

From the readings I have done so far, current will be generated at each of these stages due to transfer of electrons. However, most authors will introduce the concept of limiting current at the rate determining step and neglect the remainder current generated from other stages.

If so, is it possible to obtain the total current output by summing the limiting current in each individual stages of the entire chemical reaction? Or focusing on solely the limiting current of the rate determining step will give a good approximation?

• I think you have the wrong idea. The notion that "current will be generated at each of these stages due to transfer of electrons" is wrong. Rather current will be limited at each step. Also current and voltage are dependent. As the current flowing through a cell goes up, the voltage goes down. – MaxW Sep 28 '17 at 18:28
• @MaxW So, does it mean that the current measured when connecting the 2 ends of the electrode across a resistor is not the limiting current? What are the procedures needed to calculate this current then? Taking the net battery voltage (Energy given by Nernst equation - cathodic and anodic overpotential) divided by the value of the resistor and internal resistance of the cell? – Christopher Sep 29 '17 at 8:39