The surface chemistry of cerium oxide

Abstract

This review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive threeway catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water-gas shift reaction. Ceria's acid-base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focus of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO 2 to CeO 2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. Most surface science studies have been conducted on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thinfilms are also examined.

IR spectroscopy applied to metal oxide surfaces: adsorbate vibrations and beyond

“…The ability to adsorb or give up oxygen varies between the different crystallographic surface orientations, and the corresponding redox-type reactions are likely to be different. Additionally, the chemistry of the same adsorbate proceeding on a fully oxidized CeO 2 surfaces may be substantially distinct from that on a reduced ceria surface due to different oxidation states of surface cerium cations [129]. Here, we present IRRAS results of CO adsorption on macroscopic monocrystalline ceria (1 1 1) and (1 1 0) surfaces.…”

Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI)

“…This occurs due to the 30% lower oxygen vacancy formation energy on the surface of ceria compared to the bulk, which suggests that oxygen exchange between adsorbed species and the ceria surface can occur. When one oxygen vacancy is created, two adjacent Ce 4+ atoms are reduced to Ce 3+ [11]. Therefore, the valence state and intrinsic oxygen defects, along with the partial pressure of oxygen in the surrounding media, allow CONPs to serve as auto-regenerative redox status modulators [12].…”

Reactivity and reaction intermediates for acetic acid adsorbed on CeO2(1 1 1)

“…With this goal in mind, we and others have explored reaction pathways for C1 and C2 oxygenates reacting at single crystal surfaces [3] and CeO 2 nanoparticles with well-defined crystallographic terminations [4,5]. In studies of ethanol dehydrogenation by these CeO 2 nanoparticles, dehydrogenation to acetaldehyde was favored over dehydration to ethylene but the selectivity was found to depend upon surface structure [4].…”