overpotential

over- +‎ potential

overpotential (plural overpotentials)

1. (physics) The difference between the electric potential of an electrode or cell under the passage of a current and the thermodynamic value of the electrode or cell potential in the absence of electrolysis
   • 1998 June 12, Erik Reddington et al., “Combinatorial Electrochemistry: A Highly Parallel, Optical Screening Method for Discovery of Better Electrocatalysts”, in Science‎, volume 280, number 5370, DOI:10.1126/science.280.5370.1735, pages 1735-1737:

     One of the factors that limits their development and use is that known anode and cathode electrocatalysts produce useful current densities only at high overpotentials.

• overvoltage