EFFECT OF HYDROGEN AND CHLORIDE-IONS ON THE CURRENT-VOLTAGE RESPONSE OF COPPER OXIDES IN GRAPHITE PASTE ELECTRODES

The reduction of CuO and Cu2O powder as well as the oxidation of Cu2O powder were studied by solid-phase voltammetry with electroactive elec trodes in electrolytes 0.05 M KCl + x M HClO4 and 0.05 M HClO4 + x M K Cl. It was shown that the kinetics and mechanism of the electrode reac tions of the copper oxides are determined by the concentrations of the hydrogen and chloride ions. In weakly acidic electrolytes the solid-p hase reduction of CuO ends at the stage of CuCl formation when c(Cl-) less-than-or-equal-to c(H+). The divalent copper oxide is reduced via complexes CuCl2- to the metal when c(Cl-) > c(H+). The CuO is reduced reversibly in a single step, simultaneously by the solid-phase and by an ionic mechanism, when c(H+) greater-than-or-equal-to 0.5 M (c(Cl-) = 0.05 M). Under the same conditions, Cu2O is also reduced by two mech anisms, but their kinetics differ and they are separated in time and p otential. For an oxidation of Cu2O, hydrogen and chloride ions must be present simultaneously in the electrolyte. In weakly acidic electroly tes, chloride ions stimulate the oxidation of Cu2O, but inhibit its re duction.