Characterization and Electrochemical Behavior of a Copper Ferrite Obtained by In Situ Precipitation from Aqueous Solutions

Abstract

The chemical composition, crystalline structure and properties of copper-bearing ferrites obtained by in situ coprecipitation from aqueous solutions depend on the experimental conditions. Under optimum conditions of pH, temperature, Fe(II)/Cu(II) ratio, stirrer rate and air flow, a copper-bearing ferrite was obtained, whose chemical composition, determined by potentiometric titration, ICP-AES and XRF, is Cu0,13FeII0,87FeIII2O4ċnH2O. An investigation into the crystalline structure of the ferrite by thermal analysis (TGA, DTG and DSC) and XRD pointed to CuxFe3-xO4ċFe3O4ċCuOċnH2O as the most probable structure. Electrochemical analysis of the solid ferrite was performed in HCl and HClO4 solutions using a carbon paste electrode (CPE). Successive cyclic voltammograms were registered and results suggest that solid species only participate in electrodic reactions during the first scan. In the second and subsequent scans only dissolved species are involved, thus pointing to dissolution phenomena of the solid ferrite in the CPE: In perchloric acid, only peaks corresponding to the redox systems Feads3+ + 1e– ⇔ Feads2+ and Cuads2+ + 2e– ⇔ Cu0 were scanned, whereas in hydrochloric acid, the peaks corresponded to the systems FeCl2,ads+ + le– ⇔ FeClads+ + Cl–, Cuads2+ + Cl– + le– ⇔ CuCl(s) and CuCl)(s) + 1 e– ⇔ Cu(s) + Cl–. The values of the half-peak potentials and their shift with the activity of hydrochloric acid confirmed these reactions. Chronopotentiometric analysis at a CPE containing copper ferrite further confirmed the proposed mechanisms.