Electrode Potential

Energy of a spontaneous redox reaction can be converted into electrical work.

Daniell cell is one such cell which converts the energy of redox reactions into electrical energy.

The Daniell cell is made up of two half cells, oxidation and reduction,

where each half cell consists of a metallic electrode dipped in an electrolyte.

In the oxidation half, this is the reaction that takes place:

And this is the reaction that takes place at the reduction half cell:

Let us look at in detail what happens at the oxidation half cell.

At the electrode- electrolyte interface of the oxidation half cell,

we find that zinc metal atoms from the electrode go into the solution as zinc ions

and leave behind electrons at the electrode making it negatively charged

Since, positive zinc ions go into the solution and electrons are left at the zinc electrode,

the electrode becomes negatively charged with respect to the electrolyte

At equilibrium, this results in a separation of charges between the electrode and electrolyte interface.

And this generates a potential difference between the electrode and electrolyte.

This potential difference is called the electrode potential.

Since the potential difference is developed at the oxidation half cell, this electrode potential is called oxidation potential.

Moving on, let us look at what happens at the reduction half cell in detail.

In this, there is a tendency of copper ions from the solution to deposit on the copper electrode.

This makes the copper electrode positive with respect to the electrolyte.

So, we have a separation of charges between the electrode and electrolyte surface,

Again resulting in a potential difference also called electrode potential.

This potential developed at the reduction half cell is called the reduction potential.

We can thus define electrode potential as the potential difference that exists between the electrode and electrolyte.

Now, if the concentration of all the species involved in a half cell is unity,

the electrode potential is called standard electrode potential.

Revision

Electrode potential is the potential difference that exists between the electrode and electrolyte.

Potential developed at the oxidation half cell is called oxidation potential.

The potential developed at the reduction half cell is called reduction potential.

If the concentration of all the species in a half cell is unity, the electrode potential is called standard electrode potential.