  Redox and catalytic performance in total methane oxidation of a
nonostructured ceria-terbia catalyst supported on magnesia is presented and
compared to that of a pure ceria catalyst supported on MgO. The investigated
material, Ce0.5Tb0.5Ox (3% mol.)/MgO, features several remarkable properties: a
quite low total molar loading of the two lanthanide elements, high
reducibility, as well as very high oxygen storage capacity al low temperatures
and higher activity than MgO-supported ceria. In terms of lanthanide atomic
content the catalytic performance of Ce0.5Tb0.5Ox (3% mol.)/MgO largely
improves compared to that of bulk type ceria and ceria-magnesia solid
solutions. Such a behavior implies proper optimization of the usage of
lanthanide elements. A second contribution to atomic economy in the catalyst
design relates to the fact that the new formulation demonstrate a stabilyty in
the redox and catalytic performance against very high temperature treatments.
An investigation on the structure of both the fresh and high-temperature-aged
catalyst at the atomic scale by means of complementary aberration corrected
microscopy techniques, reveals the ocuurrence of a variety of exotic,
lanthanide-containing nanostructures, which span fron isolated, atomically
dispersed Ln species to nonometer-sized CeTbO2-x patches, extended CeTbO2-x
bilayers and 2D CeTbO2-x nanoparticles. Nanoanalytical results evidence the
mixing of the two lanthanides at atomic levels in these nanostructures. The
combined effects of nanostructuring, mixing of the lanthanides at the atomic
level, and interaction with the MgO oxide are the roots of the improvement in
funtional, redox and catalytic properties of the novel Ce0.5Tb0.5Ox (3%
mol.)/MgO catalyst.
