## Quick Reference

An equation for the rate of an electrochemical reaction; it describes the current density at an electrode in terms of the overpotential. The Butler-Volmer equation is given by:*j* = *j*_{a} – *j*_{c} = *j*_{e}[exp(1 – α)*F*η/*RT* – exp(– α*F*/*RT*)], where *j*_{a} and *j*_{c} are the individual cathode and anode currents respectively, and *j*_{e} is the equilibrium current, called the exchange current density. By definition *j*_{e} = *j*_{ce} = *j*_{ae}, where *j*_{ce} is the equilibrium cathode current and *j*_{ae} is the equilibrium anode current. *F* is the Faraday constant, η is the overpotential, *R* is the gas constant, *T* is the thermodynamic temperature, and α is a quantity called the transfer coefficient.

*j* = *j*_{a} – *j*_{c} = *j*_{e}[exp(1 – α)*F*η/*RT* – exp(– α*F*/*RT*)]

*Subjects:*
Chemistry.