This study reports a thorough investigation of nanosized CuO/CeO 2 materials as an efficient catalyst for decomposition of N 2 O, which is a strong greenhouse gas largely produced by chemical industry. Effect of terminating CeO 2 crystalline planes ({100}, {110} and {111}) on the behavior of CuO dispersed over CeO 2 nanocubes, nanorods and polyhedral crystallites was examined in detail by using a variety of catalyst characterization techniques. The 4 wt. % Cu was found as the most advantageous metal loading, whereas higher Cu content resulted in lower dispersion and formation of significantly less active, segregated bulk CuO phase. It was discovered that CuO/CeO 2 solids should enable both excessive oxygen mobility on the catalyst surface as well as formation of highly reducible Cu defect sites, in order to ensure high intrinsic activity. Detailed studies further revealed that CeO 2 morphology needs to be tailored to expose {100} and {110} high-energy surface planes, as present in CeO 2 nanorods. Oxygen mobility and regeneration of active Cu phase on these surface planes is easier, which in turn facilitates higher catalytic activity through the recombination of surface oxygen atoms and desorption as molecular oxygen that replenishes active sites for subsequent catalytic cycles. As a consequence, CuO supported on CeO 2 nanorods demonstrated lower activation energy (87 kJ/mol) in N 2 O decomposition reaction compared to catalysts based on CeO 2 nanocubes (102 kJ/mol) or polyhedral CeO 2 (92 kJ/mol).

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Microporous and mesoporous siliceous phases (MFI, FAU, MCM-48, MCM-41, and SBA-15) were modified with zinc via aqueous and organometallic routes and characterized with techniques that reflect the structure of the matrix, the distribution of zinc over the matrix, and the structure of the zinc oxide species (XRD, nitrogen physisorption, IR spectroscopy, XPS, X-ray absorption fine structure (XAFS), UV-Vis spectroscopy). For comparison, MFI and MCM-48 were modified with copper alone and characterised by XPS/X-ray induced Auger electron spectroscopy and XAFS. From the results, it can be concluded that zinc interacts strongly with the siliceous surfaces, which prevents the formation of ZnO aggregates even when the coverage exceeds the monolayer limit. While zinc could be well distributed over FAU and mesoporous matrices by treatment with diethyl zinc, it remained on the external surface of MFI, possibly due to pore entrance narrowing by adsorbed species. For MCM-48 and MCM-41, the formation of a thin, probably monolayer surface zinc silicate coating was concluded from the data. With an aqueous impregnation technique, strong changes in the pore system of MCM-48 were noted, which indicate rupture of pore walls and partial structural damage. Different from zinc, copper forms small oxide aggregates upon introduction into micro and mesoporous siliceous matrices

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Copper and zinc were introduced into mesoporous siliceous matrices with the goal of obtaining model methanol synthesis catalysts with intense interaction between copper and the ZnO promoter. The preparation methods included various aqueous routes starting from acetate solutions (into MCM-48) and a route involving an organometallic step-thermolysis of a liquid heterocubane of Zn 4 O 4 type ([CH 3 ZnOCH 2 CH 2 OCH 3 ] 4 ) in a wormhole-type silica of 5 nm average pore size-followed by aqueous Cu (nitrate) impregnation. The materials were characterized by XRD, nitrogen physisorption, N 2 O frontal chromatography, TPR, and EXAFS, and their methanol synthesis activity was measured at 493 K and normal pressure. In the aqueous preparations with acetate solutions, excessive formation of silicates (particularly zinc silicate) led to damage of the pore system. A significant delay in Cu reduction was assigned to the influence of micropores formed, together with some copper silicate formation. These samples exhibited poorly accessible Cu surface areas despite small Cu particle sizes indicated by EXAFS and disappointing methanol synthesis activity. In contrast to this, a highly active catalyst was obtained via the heterocubane route that meets industrial standards in terms of reaction rate per Cu surface area. Orientation studies (EXAFS at the CuK and ZnK edges) reflecting a redox behavior of the ZnO x component illustrate the potential of this catalyst type for use in basic studies of the Cu-ZnO x interaction in methanol synthesis catalysts.

Electronic and structural properties of highly dispersed Pt−Cu alloys supported on zeolite HZSM-5 with narrow particle size distribution (1−2 nm) were studied by transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy of chemisorbed carbon monoxide. FTIR of adsorbed CO proved to be the most sensitive tool for the detection of alloy formation. Dilution of the platinum surface with copper can be recognized by the absence of dipole−dipole interaction between the chemisorbed CO molecules (geometric effect). A strong red shift of the vibration frequency of linearly bonded CO in conjunction with an increase of the relative intensity of bridge-bonded CO is discussed in terms of an electronic effect. All spectroscopic methods demonstrate the ready reoxidation and redispersion of the copper component of the particles and the reversible formation of the alloy again by repeated reduction.

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