Microstructure and oxygen evolution of Fe–Ce mixed oxides by redox treatment

Abstract

The relationship between structure and reduction/redox properties of Fe–Ce mixed oxides with a Fe content of 5, 10, 20 or 30mol%, prepared by a coprecipitation method, were investigated by XRD, Raman, TEM, TPR and TPO techniques. It is found that all the iron ions can be incorporated into the ceria lattice to form a solid solution for the FeCe 5 (Fe 5%) sample, but amorphous or crystal Fe2O3 particles were found to be present on the Fe–Ce oxide samples with higher the iron content. The reducibility of single solid solution was much better than the pure CeO2, and the appearance of dispersed Fe2O3 particles improved the surface reducibility of materials. The iron ions incorporated into the CeO2 lattice accelerated the oxygen release from bulk to surface, and surface Fe2O3 particles in close contact to CeO2 acted as a catalyst for the reaction between solid solution and hydrogen. The microstructure of exposed Fe2O3 with Ce–Fe–O solid solution allows the Fe–Ce mixed oxides to own good reducibility and high OSC, which also counteracts the deactivation of the reducibility resulting from the sintering of materials in the redox cycling.