posted on 2015-06-04, 00:00authored byS. Agarwal, X. Zhu, E. J.
M. Hensen, B. L. Mojet, L. Lefferts
The
defect chemistry of reduced ceria nanoshapes was investigated
using in situ Raman and FTIR spectroscopy. Octahedral- and rod-shaped
particles behave similarly upon exposure to CO in terms of formation
of anion Frenkel pair defects and oxygen vacancies. This similarity
is attributed to the preferential exposure of (111) surfaces in both
type of particles. Cube-shaped particles terminated with (100)-oriented
surfaces exhibit very different defect behavior in CO, revealing formation
of oxygen vacancy defects at the expense of existing anion Frenkel
pairs. Octahedra and rods, prereduced in H2, can be further
reduced with CO. In contrast, prereduced cubes can reactively adsorb
CO, forming surface-bicarbonate, only via converting Frenkel-pair
defects to oxygen vacancies, without any further net reduction of
the ceria.