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

机译：CeO2纳米粒子存在下增强的Fe2O3还原性和氧化还原稳定性

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摘要

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.
机译：通过共沉淀法制备CeO2，Fe2O3和一系列Ce / Fe摩尔比为5:95至50:50的CeO2改性的Fe2O3氧化物，并在不同温度下进行热老化，然后将其与相应的样品进行比较。物理混合CeO2和Fe2O3。通过XRD，拉曼，TEM，BET表面积，XPS，H-2-TPR和氧脉冲技术研究了所制备材料的结构/结构特征，还原行为，储氧量（OSC）和氧化还原性能。发现即使在800摄氏度下煅烧后，CeO2颗粒也非常小（<10 nm）并且高度分散在Fe2O3棒的表面上。纳米尺寸效应导致Fe2O3-CeO2界面中发生强烈的化学相互作用。在还原气氛中提高了Fe2O3的还原性。在混合氧化物中也观察到类似赤铁矿的固溶体，但是它仅存在于CeO2含量相对较低（Ce / Fe <20:80）的材料上。赤铁矿状固溶体的形成可以提高Fe2O3的表面还原度，而Fe2O3的深度还原主要取决于Fe2O3颗粒的晶体尺寸。在CeO2改性的Fe2O3氧化物的还原行为上，尺寸效应比固溶体更重要。此外，Fe2O3上CeO2的存在还极大地改善了Fe2O3的储氧能力和氧化还原稳定性，这可以归因于铈和氧化铁之间的化学相互作用，包括在TPR /之后形成复合氧化物（CeFeO3）。 OSC氧化还原测试。这些数据为设计用于化学环技术的新型OSC材料提供了有用的参考。

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