Structural and catalytic properties of Ni–Co spinel and its composites

Pure nickel–cobalt (Ni–Co) spinel and its two composites with active carbon and multi-walled carbon nanotubes (MWCNTs) were synthesized. X-ray diffraction confirmed the nickel cobaltites of cubic syngony and lattice constants for nanosized crystallites. Fourier transform infrared spectra confirmed an inverse spinel consisting of a tetrahedral site $$\hbox {Co}²⁺$$ and octahedral sites $$\hbox {Ni}²⁺$$ and $$\hbox {Co}²⁺$$. Scanning electron microscopy images demonstrated a surface texture typical for spinels and agglomerates of composite particles with active carbon and MWCNTs. All the synthesized samples have a surface area and porosity that are sufficient for the flow of heterogeneous catalytic processes. The micropore volume of the composite with MWCNTs constituted only 4% of the total porosity, while this percentage represented 25% for the composite on the basis of active carbon. The high catalytic activity of Ni–Co spinel is proved in the model reaction of borohydride hydrolysis. To create composite spinel catalysts, active carbon showed itself to be a more efficient carrier for the catalytically active mass of spinel, as compared to MWCNTs.