Inhibited Phase Segregation to Enhance the Redox Performance of NiFe2O4 via CeO2 Modification in the Chemical Looping Process

NiFe2O4 exhibits a desirable application prospect in the chemical looping process because of the high redox activity and oxygen carrying capacity. However, phase segregation resulting from the outward migration of Fe species in NiFe2O4 often occurred, which could lead to serious surface sintering and, thus, a decrease in the redox activity of NiFe2O4 center dot CeO2 was often used as a promising candidate of support to induce the formation of oxygen vacancy, which could improve the diffusion rate of lattice oxygen in oxygen carriers. Herein, we synthesized NiFe2O4 samples doped with different contents of CeO2 using a wet impregnation method. A variety of characterization analyses were conducted to investigate the fundamental mechanism of the interaction between CeO2 and NiFe2O4. It was shown that the CeO2 content with 70 wt % in NiFe2O4 sample (70 CeO2-NiFe2O4) presented an excellent redox performance and the highest resistance to phase segregation, which was due to the formation of adequate oxygen vacancy by the addition of sufficient CeO2. The presence of abundant oxygen vacancy could enhance the mobility of lattice oxygen to prevent the phase segregation and thereby maintain the microstructural integrity of NiFe2O4 during the redox reaction.