Double potential step chronocoulometry. Part I. A reexamination of EC kinetic theory including the effects of electrode reactant and product adsorption

Calculation of the theoretical double potential step chronocoulometry working curve (|Q_b/Q_f| vs. (kτ)^1/2) for an irreversible pseudo first-order chemical reaction coupled to a heterogeneous charge transfer process (EC mechanism) by finite difference methods revealed an error in the previously published working curve for this situation. The analytical solution to the mass transport equations for the EC mechanism with double potential step boundary conditions is rederived. The working curve, calculated from this new analytical solution, was in close agreement with the finite difference results. In addition, a theoretical treatment is presented for double potential step chronocoulometry where the effect of electrode reactant and product adsorption on the charge ratio, |Q_b/Q_f|, both with and without EC kinetic complications, is incorporated. A procedure whereby experimentally determined charge ratios can be corrected for the effects of reactant and product adsorption has been developed.