1 Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191, China 2 China South Industries Group Corporation, Beijing 100089, China;
Cite this article:
Shizheng ZHANG,Yaohui XU,Tingyu WANG,Ruixing LI,Hongnian CAI. SOLID SOLUBILITY AND OXYGEN STORAGE CAPABILITY OF In3+-DOPED CeO2. Acta Metall Sin, 2016, 52(5): 607-613.
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 In3+ were synthesized via a two-step process. The precursor was synthesized by a solvothermal method at 200 ℃ using a mixture solvent of (CH2OH)2 and H2O, as well as Ce(NO3)36H2O and In(NO3)3?4.5H2O as Ce and In sources, respectively. CeO2 was obtained after the precursor was calcined at 500 ℃ 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 m2/g, which was th highest among all the samples, and undoped CeO2 (92 m2/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 3.6×10-4 mol/g for undoped CeO2 to 4.4×10-4 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+.
Fig.1 XRD spectra of the samples synthesized solvothermally with In/(In+Ce) (molar fraction) of 0 (a), 1% (b), 3% (c), 5% (d) and 10% (e) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
Fig.2 Lattice parameters of the samples synthesized solvothermally with different In/(In+Ce) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
Fig.3 SEM images of the samples synthesized solvothermally with In/(In+Ce) of 0 (a), 1% (b) and 10% (c) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
Fig.4 HRTEM images of the samples synthesized solvothermally with In/(In+Ce) of 0 (a) and 1% (b) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air (d—interplanar spacing of (111) planes)
Fig.5 XPS results of Ce3d core-level for the samples synthesized solvothermally with In/(In+Ce) of 0 (a) and 1% (b) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
Fig.6 Raman spectra of the samples synthesized solvothermally with In/(In+Ce) of 0 (a), 1% (b), 3% (c), 5% (d) and 10% (e) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
Fig.7 Concentration of oxygen vacancies (A600/A460) calculated on Raman spectra of the samples synthesized solvothermally with different In/(In+Ce) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air.
Fig.8 H2 temperature-programmed reduction (H2-TPR) curves of the samples synthesized solvothermally with In/(In+Ce) of 0 (a), 1% (b), 3% (c), 5% (d) and 10% (e) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
Fig.9 Low temperature oxygen storage capability of the samples synthesized solvothermally with different In/(In+Ce) at 200 ℃ for 24 h followed by calcination at 500 ℃ for 2 h in air
[1]
Mori T, Drennan J, Wang Y, Li J G, Lkegami T.J Therm Anal Calorim, 2002; 70: 309
[2]
Steele B C H.Solid State Ionics, 2000; 129: 95
[3]
Wang Z, Kale G M, Ghadiri M.J Am Ceram Soc, 2012; 95: 2863
[4]
Chen Y, Long R W.Appl Surf Sci, 2011; 257: 8679
[5]
Rajendran A, Takahashi Y, Koyama M, Kubo M, Miyamoto A.Appl Surf Sci, 2005; 244: 34
[6]
Liu X, Shu Y, Sato T.Mater Chem Phys, 2009; 116: 421
[7]
Lin K S, Chowdhury S.Int J Mol Sci, 2010; 11: 3226
