Mössbauer study of oxygen-deficient ZnII-bearing ferrites (ZnxFe3 –xO4 –δ, 0 ⩽x⩽ 1) and their reactivity toward CO2 decomposition to carbon

Abstract

Oxygen-deficient Zn^II-bearing ferrites (Zn_xFe_{3 –x}O_{4 –δ}, 0 ⩽x⩽ 1, δ > 0) have been synthesized and studied for their reactivity in the decomposition of CO₂ to carbon at 300 °C. They were prepared by reducing Zn^II-bearing ferrites with H₂ gas at 300 °C. The oxygen-deficient Zn^II-bearing ferrites consisted of a single phase of a spinel-type structure which was oxygen-deficient compared with stoichiometric composition. Their lattice constants were larger than those of the corresponding stoichiometric spinel. Decomposition of CO₂ to carbon was accompanied by an oxidation of the oxygen-deficient Zn^II-bearing ferrite. The amount of carbon deposited on the solid decreased when the Zn content in the Zn^II-bearing ferrite increased. The decrease in decomposition rate is due to changes in the electron conductivity according to the Zn content in the Zn^II-bearing ferrite. These changes may contribute to its reactivity for decomposition of the CO₂ to carbon.