In situ Raman spectroscopy evidence of an accessible phase potentially involved in the enhanced activity of La-deficient lanthanum orthoferrite in 3-way catalysis (TWC)

- La-deficient La0.67FeO3 perovskite features original properties under H2O, CO and NO containing atmospheres.
- A iron (III+) oxide phase is reversibly formed at the surface of the La-deficient catalyst.
- Reversible iron segregation together with structural distortion favour the NO reduction in TWC.

We report here on an in situ Raman investigation of stoichiometric and La-deficient LaFeO3 solids along model treatments related to three-way catalysis. Whereas the Raman signature of the stoichiometric compound is only slightly modified by the sequence we have applied, the reversible formation of a new phase based on Fe2IIIO3 in the La-deficient solid was evidenced. This new phase was found to be stabilized under the same experimental conditions which also favor the volumetric expansion of the LFO unit cell. Eventually, this new iron oxide phase was found to be reduced under CO/He mixture and subsequently regenerated under NO.

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