Crystal plane dependent dopant migration that boosts catalytic oxidation

Abstract

CeO₂ rods with {110} facets and cubes with {100} facets were utilized as catalyst supports to probe the effect of crystallographic facets on the iron species and the structure-dependent catalytic performance. In this approach, Fe-doped ceria nanorods and nanocubes with dominantly exposed {110} and {100} crystal planes were respectively prepared and were subjected to pretreatments either in a N₂ or O₂ atmosphere. We find that Fe-doped nanocubes exhibit much better CO oxidation performance after calcination in O₂ than in N₂, even better than nanorods, which is unusual. This interesting observation is because Fe atoms migrate more efficiently to the {100} crystal surfaces, giving rise to a Fe³⁺-rich surface, when Fe-doped catalysts are sintered in O₂, which consequently results in an increase of adsorbed surface oxygen species on nanocubes. Various analysis strategies (TEM, STEM, XRD, N₂-physisorption, H₂-TPR, XPS and Raman) reveal that the crystallographic facets have a strong effect on the iron species, and finally support our hypothesis.