Mechanism of M Ferrites (M = Cu and Ni) in the CO₂ Decomposition Reaction

M ferrites (M = Ni and Cu) were prepared for the CO 2 decomposition reaction. The mechanisms of reduction and oxidation of M ferrites were investigated by thermogravimetric analysis and X-ray diffraction experiments. Cu ferrite showed excellent redox properties compared to those of Ni ferrite. Cu ferrite lost its oxygen atoms from the lattice by the H 2 reduction at 473 K, which was 150 K lower than the temperature at which Ni ferrite did. The reduction of Cu ferrite at 1073 K formed the mixture of metallic Cu, FeO, and α-Fe, while Ni ferrite gave a Ni−Fe alloy at the same temperature. Reaction of the reduced ferrites with CO 2 oxidized the ferrites by suppling oxygen atoms from CO 2 . The oxidation temperature of the reduced Cu ferrite was 200 K lower, and the weight recovery was faster than that of Ni ferrite. The oxidation with CO 2 at 1073 K could not regenerate their original states and produced the mixture of Fe 3 O 4 and metallic Cu and Ni. On the basis of the understanding of the Cu ferrite redox behaviors, a new mechanism for the CO 2 decomposition reaction was proposed.