Analysis of the applicability of short time chronoamperometry for the kinetic study of the hydrogen oxidation reaction

This work analyses the applicability of the chronoamperometric method for the evaluation of the kinetic parameters of the hydrogen oxidation reaction. It consists in the application of an overpotential step and the subsequent plot of the current density response against the square root of time. The extrapolation of the resulting straight line at short times is assigned to the kinetic current density (jk) at such overpotential (η). Then, from the polarization curve obtained after the evaluation of jk at different η, the parameters exchange current density and Tafel slope are evaluated. This method is only strictly valid for simple reactions without adsorbed intermediates. Therefore, a complete analysis that takes into account all the phenomena involved, including the effect of the pseudocapacitive current due to the adsorbed hydrogen, is carried out. The results obtained confirm the inapplicability of the chronoamperometric method for the kinetic study of the hydrogen oxidation reaction.