The facet-dependent catalytic performance of Fe2O3/CeO2 catalysts for the selective catalytic reduction of NO with NH3 (NH3–SCR) has been investigated using combined experimental and density functional theory (DFT) methods. The structure and surface characteristics of the synthesized samples were characterized by XRD, XPS, TEM, ICP–AES, N2 sorption isotherms, Raman spectra, photoluminescence spectra, H2–TPR, NH3–TPD and NO + O2–TPD. It is found that the CeO2 nanorods and Fe2O3/CeO2 nanorods predominately exposed {110} and {100} facets rather than the stable {111} facets on CeO2 nanopolyhedra and Fe2O3/CeO2 nanopolyhedra. The influence of the micromorphologies and surface properties of CeO2 supports on the NO conversion and N2 selectivity has been compared. The Fe2O3/CeO2 nanorods achieve higher catalytic activity than the Fe2O3/CeO2 nanopolyhedra for NH3–SCR of NO. The synergetic effect between CeO2 supports and Fe2O3 species has been demonstrated. The insight into molecular facet dependence by the DFT method clearly showed that the Fe2O3/CeO2 {110} catalyst is more reactive to NO and NH3 gases than the Fe2O3/CeO2 {111} and naked CeO2 {110}, which agree well with the experimental results. As a result, the outstanding catalytic performance of Fe2O3/CeO2 nanorods is attributed to the adsorbed surface oxygen, oxygen defects and atomic concentration of Fe which are associated with their exposed {110} and {100} facets of nanorods.

CeO 2 nanorods impregnated with 2.5 atom % of NiO (NiO/ CeO 2 nanorods) were successfully synthesized and examined as catalysts for the NH 3 -selective catalytic reduction (NH 3 -SCR) of nitric oxide (NO). The catalytic activity of NiO/CeO 2 nanorods resulted in up to ∼90% NO conversion at 250 °C, which is superior to that of pure CeO 2 nanorods or NiO nanoparticles. Subsequently, extensive studies of the NiO/CeO 2 -catalyzed reduction of NO were conducted using X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, temperature-programmed desorption, and density functional theory periodic calculations. Compared to that of the pure CeO 2 nanorods, the results demonstrated that the NiO/CeO 2 nanorods resulted in (i) a higher concentration of Ce 3+ chemical species, (ii) a larger amount of active O α , (iii) lower temperature reducibility, (iv) a lower amount of energy required for oxygen vacancy distortion, and (v) a significant adsorption of and strong interaction between NO and NH 3 molecules. Our findings therefore elucidated considerable details of the structural properties of the NiO/CeO 2 nanorods that were decisive for achieving a highly efficient conversion of NO by the NH 3 -SCR process at low temperatures.

Fe2O3 nanoparticles anchored in situ on carbon nanotubes via an ethanol-thermal strategy present an excellent DeNOx performance.

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The synthesis of calcium hexaboride (CaB 6 ) powder via the reaction of calcium carbonate (CaCO 3 ) with boron carbide (B 4 C) and carbon has been investigated systematically in the present study. The influences of heating temperature and holding time on the reaction products have been studied using X-ray diffractometry, and the morphologies of CaB 6 obtained at various temperatures and holding times have been investigated via scanning electron microscopy. The interaction in the CaCO 3 -B 4 C-carbon system by which CaB 6 is formed is a solid-phase process that passes through the transition phases Ca 3 B 2 O 6 and CaB 2 C 2 . The optimal conditions for CaB 6 synthesis are a holding time of 2.5 h at a temperature of 1673 K, under vacuum (a pressure of 10 ؊2 Pa). CaB 6 powder has the same morphology as B 4 C, and the properties and the shape of CaB 6 powders can be improved by choosing good-quality raw materials.