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

II. Structure of Perovskites 1982 A. Crystal Structure 1982 B. Nonstoichiometry in Perovskites 1983 1. Oxygen Nonstoichiometry 1983 2. Cation Nonstoichiometry 1984 C. Physical Properties 1985 D. Adsorption Properties 1986 1. CO and NO Adsorption 1986 2. Oxygen Adsorption 1987 E. Specific Surface and Porosity 1987 F. Thermal Stability in a Reducing Atmosphere 1989 III. Acid−Base and Redox Properties 1990 A. Acidity and Basicity 1990 B. Redox Processes 1991 1. Kinetics and Mechanisms 1992 2. Reduction−Oxidation Cycles 1993 C. Ion Mobility 1993 1. Oxygen Transport 1993 2. Cation Transport 1994 IV. Heterogeneous Catalysis 1995 A. Oxidation Reactions 1995 1. CO Oxidation 1995 2. Oxidation of Hydrocarbons 1996 B. Pollution Abatement 2001 1. NOx Decomposition 2001 2. Exhaust Treatment 2002 3. Stability 2004 C. Hydrogenation and Hydrogenolysis Reactions 2004 1. Hydrogenation of Carbon Oxides 2004 2. Hydrogenation and Hydrogenolysis Reactions 2006

Chemical structures and performance of perovskite oxides.

Solid oxide fuel cells (SOFCs) have the promise to improve energy efficiency and to provide society with a clean energy producing technology. The high temperature of operation (500−1000 °C) enables the solid oxide fuel cell to operate with existing fossil fuels and to be efficiently coupled with turbines to give very high efficiency conversion of fuels to electricity. Solid oxide fuel cells are complex electrochemical devices that contain three basic components, a porous anode, an electrolyte membrane, and a porous cathode. In this short review, a survey of the types and properties of materials that have been considered for each of these components is presented with an emphasis on the requirements for operation at intermediate temperature (500−800 °C). Some directions for future research are discussed.

Materials for Solid Oxide Fuel Cells

Progress in material selection for solid oxide fuel cell technology: A review

Transport properties of solid oxide electrolyte ceramics: a brief review

Vanadium(V) oxide supported on 7-A1203, GO2, Cr2O3, Si02, Ti02, and Zr02 was studied by X-ray fluorescence, by X-ray diffraction, and especially by the combination of Raman spectroscopy and temperature-programmed reduction (TPR) for qualitative and quantitative structural analysis, respectively. Catalysts were prepared via ion-exchange and wet-impregnation methods. The V contents ranged from - 1 to 40 wt % V. At low surface concentrations only surface vanadate phases of two-dimensional character are observed for all carriers. According to Raman and TPR data the structure of these surface vanadate species is independent of the preparation technique. At medium and high surface concentrations, the webimpregnated samples already contain crystalline V20b At equal surface concentrations the ion-exchanged catalysts contain no V205 crystallites. An exception is Si02 on which also crystalline V206 is formed in both preparation techniques. Monolayer stability toward thermal treatment decreases in the order AZO>3 Ti02> Ce02,w hereas on heating ion-exchanged V/Si02 the crystalline V206 spreads out over the silica surface. The reducibilities of the ion-exchanged catalyats, as measured by TPR, can be used as a measure for the contact interaction between vanadia and the carrier oxides. At temperatures of 500-800 K, this interaction ranges from strong with titania to weak with silica as a carrier.

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Vanadium oxide monolayer catalysts. 3. A Raman spectroscopic and temperature-programmed reduction study of monolayer and crystal-type vanadia on various supports

https://ris.utwente.nl/ws/files/6485632/Bond86structure.pdf

Structure and reactivity of titania-supported oxides. Part 1: vanadium oxide on titania in the sub- and super-monolayer regions

Solid state aspects of oxidation catalysis

https://ris.utwente.nl/ws/files/6512956/ion92gellings.pdf

Ion and mixed conducting oxides as catalysts

The temperature-programmed reduction (t.p.r.) of bulk V2O5 has been examined as part of a study of the reducibility of V2O5-containing catalysts. T.p.r. profiles have been studied as a function of flow rate, heating rate and sample weight. From experiments at different flow rates it is concluded that the order of the reduction rate in hydrogen is low or even zero. A rule of thumb has been derived to provide an easy check on possible exhaustion of hydrogen in the feed. The influence of sample weight and heating rate is explained in terms of the formation of water in the sample during reduction. The reduction of bulk V2O5 to V2O3 proceeds in several steps; intermediate species include V6O13 and VO2. The apparent activation energy of ca. 200 kJ mol–1 indicates that solid-state diffusion influences the reduction process of V2O5.

/pdf/factors-influencing-the-temperature-programmed-reduction-17twosbh5b.pdf

P.J. Gellings

Papers

Vanadium oxide monolayer catalysts. 3. A Raman spectroscopic and temperature-programmed reduction study of monolayer and crystal-type vanadia on various supports

Structure and reactivity of titania-supported oxides. Part 1: vanadium oxide on titania in the sub- and super-monolayer regions

Solid state aspects of oxidation catalysis

Ion and mixed conducting oxides as catalysts

Factors influencing the temperature-programmed reduction profiles of vanadium pentoxide