Electrochemical systems and reactions are ubiquitous in modern energy conversion applications, electrosynthesis, and sensors, to name but a few. Their key property is the ability to control reaction thermodynamics and kinetics through application of an electrode potential. In experiments, the potential of a working electrode is controlled from the backside of an electrode through connections to an external voltage source as shown in Figure . This provides a direct way to manipulate electrode potential i.e. the electrochemical potential of electrons within the bulk of electrode material. External connections and a working electrode (M ) are physically distinct solid phases, which can be viewed as a bath and a system in statistical mechanics, respectively. In this context, constant electrode potential experiments correspond to controlling the electrochemical potential, μbath = μM e , is satisfied. In general, the electrochemical potential of electrons in a given phase i can be written as μi e = µ i e + zF ϕ i