Effect of reduction condition on structure stability of NiFe2O4–δ and its catalytic performance of CO2 decomposition

Nickel ferrite, NiFe2O4, with spinel structure was prepared by citrate coordination method. The samples were characterized by X-ray diffraction (XRD) thermal gravimetric analysis (TGA). When the weight of NiFe2O4 sample was 0.5 g, the optimum reduction condition for the preparation of oxygen-deficient nickel ferrite, NiFe2O4–δ, reduced by H2 was as follows: reduction temperature was 320°C, H2 flow rate was 40 mL·min–1 and reduction time was 3 h. The results also showed that the higher reduction temperature and higher H2 flow rate as well as longer reduction time led to an excessive reduction of NiFe2O4–δ and the destructiveness of its spinel structure, resulting in the formation of Fe-Ni alloy Fe(Ni) as well as α-Fe phase.