STRUCTURAL PROPERTIES AND NONSTOICHIOMETRIC BEHAVIOR OF CeO₂

Au/CeO2 Catalysts: Structure and CO Oxidation Activity

“…In particular, the interstitial compensation mechanism and oxygen vacancies creation using divalent cation are very frequent. Empirical calculations carried out for M 3+ cations show that the oxygen vacancy compensation mechanism is undoubtedly the preferred route, especially for large dopants cations (radius > 0.8 Å) [48]. Solid solutions with isovalent cations result in a slightly different situation.…”

“…The addition of tiny amounts of Zn and Fe (1 and 2 wt %) notably boost the CO oxidation activity of the Au/CeO 2 -based materials. The results are especially impressive given the fact that all doped catalysts reached full CO conversion at sub-ambient temperatures, while the unmodified Au/CeO 2 /Al 2 O 3 achieved complete CO abatement at around 40 • C. In this specific case, the main difference between Fe and Zn as ceria promoters is that, while Fe 3+ cations can replace Ce 4+ forming a Ce-Fe solid solution [36,48], Zn 2+ does not enter into ceria lattice. However, in both situations, a higher population of oxygen vacancies is identified.…”

“…This redox property strongly depends on the mechanism followed by this solid for the oxygen vacancy formation. Oxygen vacancies are punctual defects specially established at the surface of the material [47,48] and are responsible for the ability of the CeO2 to exchange oxygen species with the environment. In this sense, CeO2 can be considered as an oxygen buffer due to its oxygen storage capacity [49].…”

Ceria Nanoshapes—Structural and Catalytic Properties

“…Cerium oxide (CeO 2 ) has a cubic fluorite structure with space group Fm3m and a unit cell parameter of 5.41 Å at room temperature [29]. The CeO 2 structure consists of a cubic close-packed array with each cerium ion (white circles) coordinated by eight oxygen ions (gray circles), vice versa, oxygen ions are surrounded by four cerium ions in a crystal unit, as illustrated in Figure 1 [30].…”

“…In other words, CeO 2 can undergo substantial oxygen stoichiometric changes in response to change in temperature, oxygen pressure, electric field, and presence of dopants, without undergoing a change in the fluorite crystal structure [31][32][33][34][35][36][37][38]. The transport of oxygen in the ceria lattice results in the creation of intrinsic point defects [29]. These point defects can be created by either thermal disorder or by interaction with the surrounding atmosphere.…”