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The surface grafting of CeO 2 onto Fe 2 O 3 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, CeO 2 and Fe 2 O 3 were intimately contacted by interfacial Ce–O–Fe bonding, and no solid solutions or mixed Ce and Fe oxides were formed after heating at 900 °C. The oxygen storage capacity and initial rate of oxygen release/storage were both increased in the composite structure by virtue of the Fe 2 O 3 and CeO 2, respectively. The reduction–oxidation cycles in which Fe 2 O 3 is reduced via Fe 3 O 4 to Fe metal by CO or H 2 and then reoxidized by O 2 were stabilized by surface-grafting Fe 2 O 3 with CeO 2 . In situ Raman spectra demonstrated that the surface-grafted CeO 2 acts as an oxygen gateway, activating the dissociation of O 2 into oxide ions or the recombination of oxide ions into O 2 and transferring oxide ions to/from Fe 2 O 3 . Meanwhile, Fe 2 O 3 acts as an oxygen reservoir that expands the O 2 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.
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Machida et al. (2015) studied this question.
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