Surface-Dependence of Defect Chemistry of Nanostructured Ceria

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

Defect Chemistry of Ceria Nanorods

Ceria nanorods were investigated using in-situ Raman and FTIR spectroscopy for CO adsorption and subsequent reaction with water at 200 °C and 350 °C. The involvement of defects in ceria nanorods during CO adsorption and reaction with H2O is dependent on the temperature. At 200 oC, most of the carbonate and formate species formed in CO do not involve the creation of defects, while at 350 oC all of the carbonates and formates formed are related to the creation of defects (15% by formates and 85% by mono/bi-dentate carbonates). Finally, at 350°C very stable poly-dentate carbonates are formed that do not induce defects and cannot be regenerated with water