Enhanced reducibility and redox stability of Fe2O3 in the presence of CeO2 nanoparticles

CeO2, Fe2O3 and a series of CeO2-modified Fe2O3 oxides with Ce/Fe molar ratios ranging from 5 : 95 to 50 : 50 were prepared by a co-precipitation method and thermally aged at different temperatures, which were compared with corresponding samples prepared by physically mixing CeO2 and Fe2O3. The structural/textural feature, reduction behavior, oxygen storage capacity (OSC), and redox performance of the prepared materials were investigated via XRD, Raman, TEM, BET surface area, XPS, H-2-TPR and oxygen pulse techniques. It was found that CeO2 particles were very small (<10 nm) and highly dispersed on the surface of Fe2O3 rods even after calcination at 800 degrees C. The nano-size effects resulted in strong chemical interaction in the Fe2O3-CeO2 interfaces, which significantly improved Fe2O3 reducibility in the reducing atmosphere. Hematite-like solid solutions were also observed in the mixed oxides, but it only existed on the materials with relatively low CeO2 content (Ce/Fe < 20 : 80). The formation of hematite-like solid solution could improve the surface reduction of Fe2O3, while the deep reduction of Fe2O3 depended mainly on the crystal size of Fe2O3 particles. The size effect played a more important role than solid solution on the reduction behavior of CeO2-modified Fe2O3 oxides. In addition, the presence of CeO2 on Fe2O3 also strongly improved the oxygen storage capacity and redox stability of Fe2O3, which can be attributed to the chemical interaction between cerium and iron oxides, involving the formation of a complex oxide (CeFeO3) after the TPR/OSC redox testing. These data provide useful references to design novel OSC materials for chemical looping technologies.