Correction to the conventional Klingler-Kochi method for accurate assessment of electrochemical kinetic parameters utilizing cyclic voltammetry

Abstract

The conventional Klingler-Kochi method has been utilized for several decades and has recently gained significant traction in the estimation of electrochemical kinetic parameters. This includes the determination of formal electrode potential ($E_f^0$), standard rate constant ($k^0$) and dimensionless kinetic parameter (ψ) through the technique of cyclic voltammetry. However, the values obtained through this method occasionally exhibit significant discrepancies when compared to those derived from alternative techniques. The validation of the analytically derived Klingler-Kochi equations through alternate theoretical approach namely numerical methods (digital simulations) has revealed inaccuracies, resulting in misleading interpretations of kinetic data. Consequently, the original equations proposed by Klingler-Kochi have been re-derived, resulting in the refinement of the previous equations. This revised approach is referred to as the corrected Klingler-Kochi method, which should be employed for the accurate estimation of $E_f^0$, $k^0$ and ψ for redox couples that adhere to the Butler-Volmer kinetic model, particularly those with a peak potential difference greater than 150 mV and a cathodic charge transfer coefficient (${\alpha }_c$) within the range of 0.3 < ${\alpha }_c$ < 0.7. The assertions are additionally substantiated by experimental validation through voltammetric analysis of the redox couples ${\left[U{O}_2{\left(C{O}_3\right)}_3\right]}^{4-}/{\left[U{O}_2{\left(C{O}_3\right)}_3\right]}^{5-}$, ${\left[\text{Pu}{O}_2{\left(C{O}_3\right)}_3\right]}^{4-}/{\left[\text{Pu}{O}_2{\left(C{O}_3\right)}_3\right]}^{5-}$, $F{e}^{3+}/F{e}^{2+}$ and $E{u}^{3+}/E{u}^{2+}$. Both the conventional and corrected Klingler-Kochi methods yield comparable kinetic results ($E_f^0$ and $k^0$) for the ${\left[U{O}_2{\left(C{O}_3\right)}_3\right]}^{4-}/{\left[U{O}_2{\left(C{O}_3\right)}_3\right]}^{5-}$ couple, which exhibits an ${\alpha }_c$ value near 0.5. However, the conventional Klingler-Kochi method produces inaccurate results for the ${\left[\text{Pu}{O}_2{\left(C{O}_3\right)}_3\right]}^{4-}/{\left[\text{Pu}{O}_2{\left(C{O}_3\right)}_3\right]}^{5-}$, $F{e}^{3+}/F{e}^{2+}$ and $E{u}^{3+}/E{u}^{2+}$ redox couples, where the ${\alpha }_c$ values significantly diverge from 0.5. In contrast, the corrected Klingler-Kochi method accurately predicts the kinetic parameters for all examined redox couples, further corroborated by digital simulations.