Tafel equation

The Tafel equation is derived from the field of electrochemistry and approximately describes the relationship between the current density at an electrode and the electrode potential. It was named after Julius Tafel, who had found in 1905 empirically. The equation table is helpful in calculations of the cell voltage of electrochemical cells, especially for the electrolysis. Also for the discussion of the voltage drop in a fuel cell at a given current, it is important here is a statement of the equation:

• At a given current the electrochemically induced voltage drop is lower, the higher the exchange current of the cell.

The exchange current is a function of the catalyst used in the fuel cell. Therefore, it is an object of the development of fuel cell to find catalysts that maximize that current.

The Tafel equation holds only approximately in a central power area. For smaller current intensities, the precise Butler -Volmer equation has to be used.

Formula of the Tafel equation

This includes:

U: the voltage drop R: the universal gas constant T: the absolute temperature α: passage or symmetry factor z: number of electrons transferred F: Faraday's constant The exchange current density i: the current density