Electrochemical potentials from first principles

The electrochemical potential is the fundamental parameter in the theory of electrochemistry. Not only does it determine the position of electrochemical equilibria but also it acts as the driving force for electron transfer reactions, diffusion-migration phenomena, and phase transformations of all kinds. In the present work, the electrochemical potential is defined as the total work done in transferring a single particle of a substance from a universal reference state to a specified location, at constant temperature and pressure. It is the sum of two scalar fields: the electrostatic potential energy and the chemical potential energy. The electrochemical potential is widely underutilized within the fields of solid-state science and electrochemical engineering. For historical reasons, many authors prefer to analyze driving forces in terms of electrode potentials, concentration gradients, or Gibbs free energies. In this paper, the author provides a short introduction to the electrochemical potential and then shows how some of the major branches of electrochemistry can benefit from using it. Topics examined include the Volta potential difference, the membrane potential difference, the scanning Kelvin probe microscope, the electromotive force, the proton motive force, and the activation of electron transfer.