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Abstract

High-surface-area CexFe1-xO2 solid solutions with about 5 nm in size have been successfully prepared by using ultrahigh surface area carbon material as template and cerium and iron nitrates as oxide precursor. The obtained materials were characterized by means of N2 physisorption, X-ray diffraction, Raman spectroscopy, electron paramagnetic resonance, transmission electron microscopy and energy dispersive X-ray spectroscopy. The redox and catalytic properties of the nanoscale CexFe1-xO2 solid solutions were also evaluated by temperature-programmed reduction and ethanol steam reforming. The results confirm the formation of the nanoscale CexFe1-xO2 solid solutions with cubic phase with fluorite structure, and the process of Ce4+ substitution by the Fe3+ gradually from surface to bulk of CeO2. A small addition of Fe into CeO2 resulted in a remarkable increase in the surface area and oxygen vacancy concentration, and decease the particle size of the solid solution, while further Fe addition decreases the surface area and vacancy concentration of the solid solution ,and increases the particle size of the solid solution. The results from temperature-programmed reduction show that addition of Fe into CeO2 does not only promote the reduction of CeO2, but also increase the oxygen vacancy concentration. The CexFe1-xO2 solid solutions show a significant catalytic activity toward ethanol steam reforming with above 64 % selectivity to hydrogen at 550 oC. The Ce0.90Fe0.10O2 sample presents the superior activity and selectivity to hydrogen compared to CeO2, Fe2O3 and the other solid solutions. The findings exhibit that the carbon template route may be of great potential in synthesis of other solid solutions, and the CexFe1-xO2 solid solutions are potential materials with oxygen storage and ethanol steam reforming.