APPLICATION OF N-DOPED CARBON NANOTUBES FOR THE PREPARATION OF HIGHLY DISPERSED PdO–CeO2 COMPOSITE CATALYSTS

Pd–CeO2 catalytic composites deposited on the surface of carbon nanomaterials (CNMs) can act as model systems for probing the nature of active sites of catalytic reactions and can be also considered as promising catalysts for low-temperature oxidation reactions. In this work, nitrogen-doped carbon nanotubes (N-CNTs) are used as a support. The Pd–CeO2/N-CNT catalysts are prepared using different methods of synthesis and studied by a complex of physicochemical methods. The activity of the catalysts is tested in the CO oxidation reaction. The nature of solvents and/or precipitants is varied to establish the optimal method of deposition of highly dispersed palladium and CeO2 species on the surface of N-CNTs. It is shown that using NH3 as a precipitant results in the preparation of more active catalysts than the one synthesized using guanidine. The deposition of Ce and Pd precursors from aqueous solutions leads to the formation of highly dispersed PdO particles but does not allow stabilizing ceria particles on the N-CNT surface. The most active Pd–CeO2/N-CNT catalysts containing active components in a highly dispersed state are prepared by using acetone as a solvent. Co-impregnation of the support with Ce and Pd precursors is found to be more effective than the sequential impregnation with the Ce precursor followed by the palladium precursor. Thus prepared Pd–CeO2/N-CNT catalysts are characterized by high activity in the reaction of CO oxidation at low temperatures; the temperature of 50% CO conversion is equal to 80 °C. The obtained results show that carbon nanomaterials can be effectively used to vary the dispersion and degree of interaction between Pd/PdO and CeO2 components determining the catalytic efficiency in the CO oxidation reaction.