Rare-Earth Manganites: Surface-Segregated Platinum Increases Catalytic Activity

Abstract

Crushed and etched lanthanum lead manganite (La(0.7)Pb(0.3)MnO(3)) crystals containing as little as 0.005 atomic percent platinum have significantly higher catalytic activity than free platinum crystals. This higher activity is due to an almost 100-fold segregation of platinum on the surface. The surface platinum concentration found, 0.5 atomic percent, is sufficient to account for the enhanced activity provided that the platinum has the same activity as platinum supported on alumina.

Hexagonal YFe1−xPdxO3−δ: Nonperovskite Host Compounds for Pd2+ and Their Catalytic Activity for CO Oxidation

“…Since the 1970s, mixed oxides with the perovskite structure have been found to be catalytically active for reactions involving automobile emissions control. − A recent noteworthy advance was reported in the three-way automotive catalyst LaFe 0.57 Co 0.38 Pd 0.05 O 3 developed by Tanaka and co-workers. , This catalyst was described as “intelligent” due to its ability to regenerate Pd nanoparticles in response to the redox fluctuations that occur in the exhaust gas stream. They showed, by anomalous X-ray diffraction and X-ray absorption fine structure spectroscopy at the Pd K-edge, that Pd ions migrate out of the host matrix as metallic Pd particles under reducing conditions and reenter the perovskite structure, on the B site, as ions under oxidizing conditions.…”

“…Since the 1970s, mixed oxides with the perovskite structure have been found to be catalytically active for reactions involving automobile emissions control. [1][2][3] A recent noteworthy advance was reported in the three-way automotive catalyst LaFe 0.57 Co 0.38 Pd 0.05 O 3 developed by Tanaka and co-workers. 4,5 This catalyst was described as "intelligent" due to its ability to regenerate Pd nanoparticles in response to the redox fluctuations that occur in the exhaust gas stream.…”