Criteria for the selection of the scan rate in the evaluation of the kinetic parameters of the hydrogen oxidation reaction by a potentiodynamic sweep

Abstract

The use of the current density values obtained from a voltammetric sweep at a slow scan rate jvs(η) in place of those of a steady state polarization jss(η) for the determination of the kinetic parameters of the hydrogen oxidation reaction (hor) on a rotating disc electrode was analyzed. Three sets of kinetic parameters similar to those evaluated previously for the noble metals Pt, Ir and Rh, used as electrocatalysts for this reaction, at three different rotation rates (100, 3600 and 10000 rpm) and four different scan rates (10-4, 10-3, 10-2 and 5  10-2 V s-1) were selected for this study. The determination of the hydrogen electrode reaction (HER) polarization resistance, around the equilibrium condition, was also investigated. Finally, the conditions in which the approximation jvs(η) = jss(η) can be considered valid were established for both, the polarization plot and the polarization resistance and practical criteria were established.