Kinetic study of the chlorine electrode reaction on Ti/RuO2 through the polarization resistance. Part III: Proposal of a reaction mechanism

JOSÉ L. FERNÁNDEZ; MARÍA R. GENNERO DE CHIALVO; ABEL C. CHIALVO

ELECTROCHIMICA ACTA

Pergamon

Año: 2002 vol. 47 p. 1145 - 1152

0013-4686

A kinetic mechanism for the chlorine electrode reaction (ClER) on Ti/RuO2 electrodes is proposed. The first step is the oxidation of the superficial sites, where the chloride ion is electroadsorbed giving the atomic chlorine intermediate. The later discharge of chlorine can take place either by recombination of two adsorbed intermediates or by the reaction between the intermediate and the chloride ion, being both chemical steps. The expression of the intrinsic polarisation resistance Rpo as a function of the activity of chloride aCl-o’ and the partial pressure of chlorine p¯Cl2 was obtained from the resolution of the kinetic mechanism and it was compared with experimental data. The correlations of the independent experimental relationships Rpo versus aCl-o’ and Rpo versus p¯Cl2 were remarkably good, giving strong evidence that the ClER takes place through the proposed mechanism on the RuO2 electrodes. The kinetic constants obtained from the correlations were used for the simulation of the dependences of the current density and the surface coverages on overpotential.