Electrochemical dissolution of CrIII and CrIV oxides

Oxidative dissolution of Cr oxides can be easily performed using voltammetry of immobilised microparticles. A combined procedure based on the dependence of current on time and potential (chronoamperometry with potential jumps) is suitable for the determination of the sensitivity of the dissolution rate to electrochemical potential. Applying this procedure, it was found that the rate determining step is preceded by two-electron oxidation in the solid phase that probably proceeds as a reversible equilibration between surface sites of Cr^III, Cr^IV and Cr^V. Voltammetry is sensitive to the phase composition, and so the voltammetric peak potentials obtained under the same conditions increase in the order LaCrO₃2IICr₂O₄<α-Cr₂O₃. The influence of Fe- and Ni-for-Fe substitution on dissolution reactivity is also discussed. Received: 20 February 1998 / Accepted: 31 March 1998