Mass and charge transfer kinetics and coulometric current efficiencies. Part III. Pattern theory and its application to oxidation-reduction electrode processes

Abstract

Electrode processes are divided into three classes on the basis of the speed of the charge-transfer process: fast, which are fully described by masstransfer theory; moderate, which require the complete rigorous mass plus charge-transfer theory; and slow, which can be treated rigorously by a simplified theory. This simplified theory is developed into pattern theory, from which pattern equations are derived that are explicitly descriptive of the behaviour pattern of slow reactions and demonstrate the involvement of mass-transfer processes therein. From pattern theory, methods based upon voltammetric scans are developed for the rapid experimental determination of k and α when the conditional potential and limiting current are measurable and also when either or both are unknown. These methods are applicable in situ during a coulometric determination, and current efficiencies can be evaluated from the values obtained. Calculated and experimental scans and efficiencies show excellent agreement.