# Definition of Absolute Electrode Potential

• Dario56

#### Dario56

Hey guys,

I have two questions:

1) I thought absolute electrode potential is galvani potential difference at the interface. However, it is given by this equation in John Bockris - Modern Electrochemistry: $$E(abs) = ^M\Delta^S\phi - \mu_e^M/F$$
First term is galvani potential difference on the metal/solution interface and the other is chemical potential of electrons in the metal divided by Farady's constant

Why is chemical potential of electrons in metal included in the definition?

2) On wikipedia, absolute electrode potential is defined as: $$E(abs) = ^M\Delta^S\phi + \Theta$$

Where second term is work function of the metal. This definiton is a little bit different than in Bockris since work function includes surface potential difference on the interface in addition to chemical potential of electrons in the metal.

Why are these two definitions different?

They are not essentially different. The work function is, roughly, the chemical potential per electron.
There are complicating factors because of choice of zero for the potential and the work function and a few more technical points involving geometry and the Fermi surface, but often these are not relevant. As usual, detailed semantic distinctions must be supplanted by appropriate maths.

They are not essentially different. The work function is, roughly, the chemical potential per electron.
There are complicating factors because of choice of zero for the potential and the work function and a few more technical points involving geometry and the Fermi surface, but often these are not relevant. As usual, detailed semantic distinctions must be supplanted by appropriate maths.
Yes as I mentioned in the post, work function is defined as: $$\Theta = -\mu_e^M + zF\Xi^M$$

Other term is surface potential of the metal, so this term is the difference between the two definitions.

Maybe as you said, surface potential term is usually small compared to chemical potential term.