Voltammetry of adsorbed species: Nonideal interactions leading to phase transitions

Phase transition behaviors are not uncommon in voltammetry owning to strong interactions on the surface. By coupling interfacial electrode kinetics with the Frumkin adsorption isotherm, the underlying physicochemical processes occurring in voltammetry-induced phase transition are studied via simulation herein. We report that phase-transition-like behavior is only observable in voltammetry under reversible electrode kinetics, which otherwise would lead to a “disconnection” from the Frumkin adsorption isotherm. In the case when phase transition occurs in the time scale of voltammetry, the simulated interfacial conditions reveal intrusions into the “forbidden” part predicted by the Frumkin adsorption isotherm, which is otherwise inaccessible to the prediction on the assumption of mass transport equilibrium, even if significant excess in bulk concentration is used.