Decomposition potential or Decomposition voltage, in electrochemistry, refers to the minimum voltage (difference in electrode potential) between anode and cathode of an electrolytic cell that is needed for electrolysis to occur.
The voltage at which electrolysis is thermodynamically preferred is the difference of the electrode potentials as calculated using the Nernst equation. Often the actual voltage needed for electrolysis exceeds the thermodynamical value. The additional voltage is referred to as overpotential and is especially high in electrolysis reactions that involve gases, such as oxygen, hydrogen or chlorine. Increasing voltage above the decomposition potential can increase the rate of reaction..