BaFeO3−xPerovskite: An Efficient NOxAbsorber with a High Sulfur Tolerance

The noble metal free perovskite-type BaFeO3−xcatalyst has been synthesized by a sol−gel method containing a small amount of spinel and carbonate. NOxis stored on both perovskite and carbonate, and the formed nitrate on the perovskite can be transferred to the neighboring carbonates to regenerate the storage sites on the perovskite. During the sulfation process, both perovskite and carbonate can be sulfated, and the sulfate species formed on the former one is more easily reduced. The poison of the perovskite catalyst is mainly due to the sulfation of the carbonate. The NOxstorage capacity of the sulfated BaFeO3-950 catalyst, on which a trace amount of carbonate exists, drops only 14% comparing with the fresh catalyst. The iron atoms surrounding the barium atoms closely in the crystal lattice of the perovskite inhibit the sulfation of the barium, inducing a high sulfur tolerance.