The Role of CeO2 as a Gateway for Oxygen Storage over CeO2-Grafted Fe2O3 Composite Materials

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• 作者：Masato Machida ; Takahiro Kawada ; Hiroaki Fujii ; Satoshi Hinokuma
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 5, 2015
• 年：2015
• 卷：119
• 期：44
• 页码：24932-24941
• 全文大小：699K
• ISSN：1932-7455

文摘

The surface grafting of CeO₂ onto Fe₂O₃ with a 1:5 molar ratio produced a thermally stable composite material with greater and faster oxygen storage/release than its separate constituents. In the composite, CeO₂ and Fe₂O₃ were intimately contacted by interfacial Ce鈥揙鈥揊e bonding, and no solid solutions or mixed Ce and Fe oxides were formed after heating at 900 掳C. The oxygen storage capacity and initial rate of oxygen release/storage were both increased in the composite structure by virtue of the Fe₂O₃ and CeO₂, respectively. The reduction鈥搊xidation cycles in which Fe₂O₃ is reduced via Fe₃O₄ to Fe metal by CO or H₂ and then reoxidized by O₂ were stabilized by surface-grafting Fe₂O₃ with CeO₂. In situ Raman spectra demonstrated that the surface-grafted CeO₂ acts as an oxygen gateway, activating the dissociation of O₂ into oxide ions or the recombination of oxide ions into O₂ and transferring oxide ions to/from Fe₂O₃. Meanwhile, Fe₂O₃ acts as an oxygen reservoir that expands the O₂ storage capacity. The composite material was tested in a simulated exhaust gas stream with lean/rich perturbations (which occur in automotive three-way catalysts). The synergistic effect of the surface grafting effectively buffered the system against air-to-fuel ratio fluctuations.