Filonenko S. Preparation and physical-chemical properties of bimetallic nanocomposites based on Palladium with transition metals and Copper with noble metals

The work is devoted to determination of the influence of the metal-organic precursor nature, conditions of their preparation and decomposition reactions on the composition, structure, sorption and catalytic properties of bimetallic nanocomposites. The conditions of preparation of metal-organic precursor containing cations of palladium and transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ag) was established. The decomposition of the precursor leads to formation of the nanocomposite which contains bimetallic nanoparticles from 5 to 15 nm in size and amorphous carbon. The catalytic activity of the nanocomposites in oxidation-reduction reaction exemplified by 4-nitrophenol reduction and interconnection of the activity with redox potential of transition metals were shown. Basing on the quantum-chemical calculation data the redistribution of electron density in ethylene molecule bonded with bimetallic clusters was analyzed and the degree of rehybridization of the molecule was quantitatively estimated in the frames of "Atoms in molecules" theory. It was shown that during the pyrolysis in hydrogen atmosphere of copper fulvate obtained by precipitation the synthetic fulvic acid by Cu2+ cations, reduction of copper takes place. Formation of the nanoparticles with round shape and average sizes from 31 nm to 42 nm under the temperature increasing from 300 to 900 °C is observed. Simultaneously for the nanocomposite differences in the textural characteristics are observed. The structure of the nanocomposites changes from mesoporous (Vmeso = 0,14 сm3/g) to microporous (Vmicro = 0,10 сm3/g), and besides improvement of the crystal structure of the metal phase and increment of the carbonization degree of the organic component are observed. Holding the pyrolysis in inert atmosphere leads to partial reduction of the copper and formation of the nanocomposite which contains up to 36 % of carbon and are characterized by microporous structure with small total pore volume (Vmicro = 0,01 сm3/g).