Battery knowledge · Electrochemistry fundamentals
Overpotential
The extra voltage, beyond the equilibrium potential, needed to drive a reaction at a given rate at one electrode. Activation overpotential pays for charge transfer, concentration overpotential for depleted reactant, and both appear as polarization at the terminals. [1]
- Abbreviation
- η
- Unit
- V
Example
Overpotential drives reaction current
At equilibrium net current is zero. At +50 mV, current density is 2.268 A/m².
Fixed concentrations, symmetric transfer coefficients and no transport limitation.
Explore the graph
At equilibrium, forward and reverse reaction currents cancel.
At equilibrium net current is zero. At +50 mV, current density is 2.268 A/m².
i = 2i₀ sinh(Fη / 2RT)
Illustrative model. Fixed concentrations, symmetric transfer coefficients and no transport limitation.
Use in Lemonergy
Connect reaction sites and transport paths.
This is a reference concept. No executable Lemonergy block has been verified for this term.
References & further reading
Technical references
- Quantities, Units and Symbols in Physical Chemistry, 3rd edition, 2nd printing
IUPAC · 2011
Technical reference · Physical-chemistry notation, thermodynamics, electrochemistry and transport quantities.