In generic terms, electrochemical potential is the mechanical work done in bringing 1 mole of an ion from a standard state to a specified concentration and electrical potential. According to the IUPAC definition, it is the partial molar Gibbs energy of the substance at the specified electric potential, where the substance is in a specified phase.  Electrochemical potential can be expressed as
where:
*  is the electrochemical potential of species i, in J/mol,
* μ is the chemical potential of the species i, in J/mol,
* z is the valency (charge) of the ion i, a dimensionless integer,
* F is the Faraday constant, in C/mol,
* Φ is the local electrostatic potential, in V.
In the special case of an uncharged atom, z = 0, and so  = μ.
Electrochemical potential is important in biological processes that involve molecular diffusion across membranes, in electroanalytical chemistry, and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of potential energy through which energy may be conserved.
In cell membranes, the electrochemical potential is the sum of the chemical potential and the membrane potential.