Is iron doping of nanoceria possible at low temperature?

Abstract

Iron doping of ceria (CeO2) was attempted by an aqueous reaction process in the presence of an organic stabilizer. The 2–3 nm diameter nanoparticles were characterized by transmission electron microscopy, X-ray diffractometry, inductively coupled plasma atomic emission spectrometry (ICP-AES), and oxygen storage capacity (OSC). ICP-AES showed that both metals were present, but only crystalline ceria was observed. The estimated amount of Fe incorporated in the ceria phase was about 2–4 at.%, leaving a significant amorphous iron phase postulated to be FeOOH. Heating experiments converted the amorphous phase into crystalline maghemite and hematite phases in the 59 at.% nominal Fe sample. OSC increased linearly with Fe concentration and was appreciably larger than any previously reported OSC values for doped ceria. These results can be explained by the high OSC inherent to the amorphous iron phase, which is converted to a crystalline hematite phase in our OSC measurement. Surprisingly, the OSC cyclability inherent to pure ceria persists in the iron-doped material.