Over the past several years, cerium oxide and CeO2-containing materials have come under intense scrutiny as catalysts and as structural and electronic promoters of heterogeneous catalytic reactions. Recent developments regarding the characterization of ceria and CeO2-containing catalysts are critically reviewed with a special focus towards catalyst interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide. Relevant catalytic and technological applications such as the use of ceria in automotive exhaust emission control and in the formulation of SO x reduction catalysts is described. A survey of the use of CeO2-containing materials as oxidation and reduction catalysts is also presented.

Catalytic Properties of Ceria and CeO2-Containing Materials

Oxidation into CO2 is a major solution to CO abatement in air depollution treatments. The development of catalytic converters led to an extraordinary high number of publications on metal catalysts during the last fifty years. Due to the increasing price of noble metals and to remarkable progresses in oxide syntheses, catalytic oxidation of carbon monoxide over oxide catalysts has recently gained in interest, even if some oxides are known to present remarkable activity since the beginning of the 20th century. In this Review, the kinetics and mechanism of CO oxidation on single and mixed oxides are examined, alongside the catalyst structures

Catalytic Oxidation of Carbon Monoxide over Transition Metal Oxides

The limiting steps of CO oxidation catalyzed by ceria via the Mars−van Krevelen reaction mechanism are identified and investigated by means of density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U). We address the adsorption of CO on the (111) and (110) surfaces, and its oxidation via participation of lattice oxygen leading to vacancy formation and CO2 desorption. CO physisorbs on the (111) ceria surface (Ebind 2 eV) yielding carbonate formation and surface reduction. The DFT+U energy of CO adsorption and oxidation is studied as a function of the parameter U. This analysis demonstrates that the values of U presently used in the literature (U > 4 eV) tend to overestimate the binding energy of CO to ceria surfaces. In contrast, the energy for the complete CO oxidation reaction is effectively independent of U and in good agreement with the available experimental data. The discuss...

CO Adsorption and Oxidation on Ceria Surfaces from DFT+U Calculations

Induced changes in ceria by thermal treatments under vacuum or hydrogen

The rare earth (lanthanide) oxides, although constituting a closely related group of compounds, exhibit a rich variety of characteristic behaviors and solid-state properties, including several features that make them interesting subjects for Catalytic studies. Abundances and costs of these materials parallel those of the rare earth metals themselves, and range from common and fairly inexpensive (e.g. La2O3 and CeO2) to scarce and relatively costly (e.g., Tm2O3 and Lu2O3). All are quite refractory and nonvolatile, having melting points in excess of 2000° C, and some display a complex array of nonstoichiometric compositions. Most of the oxides are paramagnetic, with stable cationic electron configurations containing as many as seven unpaired 4f-electrons, and, as escheated from their periodic location, all are quite strongly basic. However, although the catalytic and surface properties of alkali, alkaline-earth, and other basic oxides have been extensively studied and documented [1], equivalent inf...

Catalytic Properties of Rare Earth Oxides

Catalysis of carbon monoxide oxidation by cerium dioxide: II. Microcalorimetric investigation of adsorption and catalysis

Catalysis of carbon monoxide oxidation by cerium dioxide: I. Correlations between catalytic activity and electrical conductivity

Catalytic properties of thorium oxide in the oxidation of carbon monoxide: I. Calorimetric confirmations of adsorption and catalysis processes

L’etude des spectres d’absorption infrarouge de l’oxyde de carbone et du gaz carbonique chimisorbes sur la thorine a permis de confirmer le mecanisme de l’oxydation catalytique de l’oxyde de carbone sur cet oxyde. L’oxyde de carbone se chimisorbe sur les oxygenes superficiels sous forme de formiate qui peut etre oxyde en carbonate par action ulterieure d’oxygene. Or ce carbonate etant stable jusqu’a 350 °C, la thorine ne pourra etre catalyseur de cette reaction qu’a partir de cette temperature, comme nous l’avions deja constate.

Étude de l'oxydation catalytique de CO sur la thorine par spectrométrie infrarouge

Mise en évidence d'une forme active de l'oxygène dans la réaction d'oxydation du monoxyde de carbone par la mesure de la conductivité électrique du bioxyde de titane (anatase) en cours de catalyse

Jean Veron

Papers

Catalysis of carbon monoxide oxidation by cerium dioxide: II. Microcalorimetric investigation of adsorption and catalysis

Catalysis of carbon monoxide oxidation by cerium dioxide: I. Correlations between catalytic activity and electrical conductivity

Catalytic properties of thorium oxide in the oxidation of carbon monoxide: I. Calorimetric confirmations of adsorption and catalysis processes

Étude de l'oxydation catalytique de CO sur la thorine par spectrométrie infrarouge

Mise en évidence d'une forme active de l'oxygène dans la réaction d'oxydation du monoxyde de carbone par la mesure de la conductivité électrique du bioxyde de titane (anatase) en cours de catalyse