Linear sweep voltammetric and chronopotentiometric charge/potential curves for non reversible redox monolayers

A simple equation for the charge/potential (Q/E) dependence of an electroactive monolayer is presented. This equation is valid for any chronopotentiometric or voltammetric electrochemical technique, whatever the degree of reversibility of the molecular film. Particular expressions corresponding to linear sweep and cyclic voltammetry and to chronopotentiometry with a power time programmed current have been deduced, and analogies with the current/potential curves obtained in electrochemical systems under semi-infinite diffusion mass transport control under transient and steady state conditions has been established. Reversible Q/E curves present a time-independent and universal behaviour, which does not depend on the electrochemical technique employed to obtain them. The irreversible charge/potential curves exhibit different behaviour depending on which electrochemical method has been used. Easy methods for estimating thermodynamic and kinetic parameters of the electroactive film in both chronopotentiometric and voltammetric techniques are proposed.