Standard Reduction Potential Definition

Reference electrode for pH measurements

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The standard reduction potential is the potential in volts generated by a reduction half-reaction compared to the standard hydrogen electrode at 25 °C, 1 atm and a concentration of 1 M. The standard reduction potential is defined relative to a standard hydrogen electrode, which is assigned the potential 0.00 V.
Standard reduction potentials are denoted by the variable E0.


The reduction of water:
2 H2O + 2 e- → H2 + 2 OH-
has a E0 = 1.776 V


  • Stumm, W.; Morgan, J. J. (1981). Aquatic Chemistry (2nd ed.). John Wiley & Sons, New York.