科研之友
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摘要
CeO2 is an important rare earth oxide and can be used in automotive exhaust three-way catalysts on the basis of its oxygen storage capability. Ion doping is an effective method to enhance the oxygen storage capability of CeO2. And when doping a cation whose size is smaller than Ce4+ and valence is lower than +4, it tends to evolve more defects. It is known that defects play important roles in enhancing the oxygen storage capability of CeO2. Therefore, In ion was selected as a dopant cation which matches above two factors of size and valence. In this work, a series of CeO2 with different content of le were synthesized via a two-step process. The precursor was synthesized by a solvothermal method at 200 degrees C using a mixture solvent of (CH2OH)(2) and H2O, as well as Ce(NO3)(3) center dot 6H(2)O and In(NO3)(3) center dot 4.5H(2)O as Ce and In sources, respectively. CeO2 was obtained after the precursor was calcined at 500 degrees C for 2 h in air. It was found that the solid solubility of In3+ in CeO2 was 1% (molar fraction). The doping of 1%In3+ in CeO2 almost had no impact on the morphology of multilayered structure. However, a second phase of small particles appeared and there were some changes of the morphology of multilayered structure when the concentration of In3+ increased further. The specific surface area of the 1%In3+ solid solution was 100 m(2)/g, which was th highest among all the samples, and undoped CeO2 (92 m(2)/g) ranked second. When the content of In3+ was above the solid solubility, i.e., 1%In3+, the specific surface area decreased. The low temperature oxygen storage capability could be improved from 3.6 x10(-4) mol/g for undoped CeO2 to 4.4 x10(-4) mol/g for 1%In3+-doped CeO2. When the In3+ content was greater than or equal to 3%, the low temperature oxygen storage capability decreased at the beginning, and then almost no change. Lattice parameter decreased and the concentration of Ce3+ and oxygen vacancy increased by the doping of In3+. Moreover, lattice parameter, the specific surface area, concentration of oxygen vacancy and low temperature oxygen storage capacity could mark a turning point for 1%In3+. It could be found that the low temperature oxygen storage capability was in relation to both the specific surface area and the concentration of oxygen vacancy of CeO2. In addition, the low temperature reduction peaks shifted towards lower temperatures with the addition of In3+.
- 出版日期2016-5-11
- 单位北京航空航天大学
