Mechanochemical Activation of Cu-CeO2 Mixture as a Promising Technique for the Solid-State Synthesis of Catalysts for the Selective Oxidation of CO in the Presence of H2.

A new ecologically clean method for the solid-phase synthesis of oxide copper-ceria catalysts with the use of the mechanochemical activation of a mixture of Cu powder (8 wt %) with CeO2 was developed. It was established that metallic copper was oxidized by oxygen from CeO2 in the course of mechanochemical activation. The intensity of a signal due to metallic Cu in the X-ray diffraction analysis spectra decreased with the duration of mechanochemical activation. The Cu1+, Cu2+, and Ce3+ ions were detected on the sample surface by X-ray photoelectron spectroscopy. The application of temperature-programmed reduction (TPR) made it possible to detect two active oxygen species in the reaction of CO oxidation in the regions of 190 and 210-220°C by a TPR-H2 method and in the regions of 150 and 180-190°C by a TPR-CO method. It is likely that the former species occurred in the catalytically active nanocomposite surface structures containing Cu-O-Ce bonds, whereas the latter occurred in the finely dispersed particles of CuO on the surface of CeO2. The maximum conversion of CO (98%, 165°C) reached by the mechanochemical activation of the sample for 60 min was almost the same as conversion on a supported CuO/CeO2 catalyst. [ABSTRACT FROM AUTHOR]