# Definition of Absolute Electrode Potential

• Dario56
In summary, Absolute electrode potential is defined as the galvani potential difference at the interface, which is given by the equation: $$E(abs) = ^M\Delta^S\phi - \mu_e^M/F$$This definition includes the chemical potential of electrons in the metal, which is important in determining the potential difference. However, on Wikipedia, the absolute electrode potential is defined as:$$E(abs) = ^M\Delta^S\phi + \Theta$$where the second term is the work function of the metal. This definition also takes into account the surface potential difference on the interface. While these two definitions may seem different, they are not essentially different as the work function is roughly equivalent to the chemical
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.

hutchphd said:
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.

## What is the definition of absolute electrode potential?

The absolute electrode potential is the measure of the potential difference between an electrode and a standard hydrogen electrode (SHE) under standard conditions, which is defined as 1 M concentration of H+ ions, a pressure of 1 atm, and a temperature of 25°C.

## How is absolute electrode potential different from standard electrode potential?

The standard electrode potential is the measure of the potential difference between an electrode and a standard hydrogen electrode under standard conditions, but without considering the concentration of H+ ions. The absolute electrode potential takes into account the concentration of H+ ions, which can affect the potential difference.

## What factors affect the absolute electrode potential?

The absolute electrode potential is affected by the nature of the electrode material, the concentration of H+ ions, temperature, and pressure. It can also be influenced by the presence of other ions or molecules in the solution.

## Why is the standard hydrogen electrode used as a reference in determining absolute electrode potential?

The standard hydrogen electrode (SHE) is used as a reference because it has a fixed and well-defined potential of 0 V. This allows for the comparison of the potential of other electrodes and the determination of their absolute electrode potential.

## How is the absolute electrode potential used in electrochemical reactions?

The absolute electrode potential is used to predict the direction and extent of electrochemical reactions. If the potential of an electrode is more positive than the SHE, it will act as an anode and undergo oxidation. If the potential is more negative, it will act as a cathode and undergo reduction. The difference in potential between two electrodes can also be used to calculate the electromotive force (EMF) of a cell.

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