Powder for catalysts and catalyst for exhaust gas purification

Abstract

A catalyst powder according to the present invention is a catalyst powder that includes: a core portion that contains ceria and zirconia; and a surface layer portion that is located on the core portion and contains ceria and zirconia. The ratio (M2/M1) is 0.30 or more and 0.95 or less, the ratio (M2/M1) being the ratio of a mole fraction M2 (mol %) of cerium in the surface layer portion measured using X-ray photoelectron spectroscopy to a mole fraction M1 (mol %) of cerium in the entire powder. It is preferable that the ratio (M4/2/M3/1) between M3/1 and M4/2 is 1.1 or more and 5.0 or less, wherein M3/1 (=M3/M1) represents the ratio between a mole fraction M3 (mol %) of zirconium in the entire powder and a mole fraction M1 (mol %) of cerium in the entirety of the powder, and M4/2 (=M4/M2) represents the ratio between a mole fraction M4 (mol %) of zirconium measured using X-ray photoelectron spectroscopy and a mole fraction M2 (mol %) of cerium measured using X-ray photoelectron spectroscopy.

Dependencies are inferred from the claim text.