Three-dimensionally ordered macroporous SnO2-based solid solution catalysts for effective soot oxidation

Abstract

A series of three-dimensionally ordered macroporous (3DOM) SnO2-based catalysts modified by the cations Ce4+, Mn3+, and Cu2+ have been prepared by using a colloidal crystal templating method and tested for soot combustion under loose contact condition. XRD and STEM mapping results confirm that all the secondary metal cations have entered the lattice matrix of tetragonal rutile SnO2 to form non-continuous solid solutions, thus impeding crystallization and improving the surface areas and pore volumes of the modified catalysts. In comparison with regular SnO2 nanoparticles, the 3DOM SnO2 displays evidently improved activity, testifying that the formation of the 3DOM structure can anchor the soot particulates in the macro-pores, which ensures that the contact of the soot particles with the active sites on the 3DOM skeleton is more easily formed, thus benefiting the target reaction. With the incorporation of the secondary metal cations, the activity of the catalyst can be further improved due to the formation of more abundant mobile oxygen species. In summary, these effects are believed to be the major factors responsible for the activity of the catalyst.