Thermodynamic restrictions on the rate law for faradaic current

Abstract

Thermodynamic considerations are shown to place restrictions on the form of the rate law for faradaic current. These restrictions lead naturally to the identification of system constants which can be associated with the concepts of exchange current density, charge-transfer coefficient, and stoichiometric numbers for the reacting species. These are meaningful experimental parameters independently of any further significance which may attach to them through applicability of detailed theoretical models of the charge-transfer process. They can be separately determined for systems to which small amplitude perturbation techniques are applicable and in which faradaic and non-faradaic currents can be separated. Failure to consider the possibility of non-unit formal stoichiometric numbers is suggested as one possible source of discrepancies and anomalies in rate parameters reported in the literature.