Reactivite electrochimique de quelques oxydes de vanadium en milieu HCl 1 M

Abstract

The voltammograms recorded for the oxides V 2O 5, NaVO 3, VOSO 4, NaVO 2 and V 2O 3, when incorporated in carbon paste electrodes with conducting binder, show that the electronic transfer occurs between the electrode and the soluble species. The V(V)/V(IV) and V(III)/V(II) systems are reversible and the electrochemical reactions give anodic and cathodic peaks with quite identical potentials, close to that of the standard potential of these systems. The V(IV)/V(III) couple is irreversible and the reduction, shifted towards negative potentials, coalesces with the V(III) to V(II) reduction process. For the oxides containing V(V), the reduction to V(IV) leads to two peaks: the first one is reversible and due to the reduction of the species coming from the instantaneous dissolution of the finest particles, the second one is irreversible and due to the progressive dissolution of the largest particles occuring during the cathodic sweep.