Silver-modified manganite and ferrite perovskites for catalyzed gasoline particulate filters

Silver modified manganite (LaSrAgMn) and ferrite (LaSrAgFe) perovskites were synthesized with different Ag loadings and tested for the soot oxidation reaction at low oxygen concentrations (i.e. 1 vol%), as encountered in gasoline direct injection (GDI) engines application. The state and location of Ag determine the catalytic performances of perovskites. On ferrites, Ag is either partially incorporated on the structure or present on the surface as large agglomerates. Lattice Ag+ cations are not catalytically active. Furthermore, large surface Ag particles partially cover surface oxygen vacancies and block their ability to adsorb oxygen. On the other hand, small clusters of Ag and AgO as well as a surface Ag1.8Mn8O16 additional hollandite-type phase are stabilized on manganites surface, improving the reducibility and acting as active sites for soot oxidation.