Synthesis of homo- and hetero-metallic cobalt and zinc nano oxide particles by a calcination process using coordination compounds: their characterization, DFT calculations and capacitance behavioural study

Abstract

Nano cobalt and porous zinc–cobalt oxide particles were synthesized using the concept of coordination compounds of the type [M(II)L,L′] (where M(II) = Co(II) & Zn(II) L= 4-hydroxy benzaldehyde and L′ = piperazine) and were thoroughly characterized. Because the precursors are coordination compounds possessing specific geometry in the crystal lattice, uniform and appropriately sized homo- and heterometallic nanocrystals of Co₃O₄ and ZnO·Co₃O₄ were obtained after a thermal process. The homo and hetero composite particles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), FT IR spectroscopy and electrochemistry. The paramagnetic chemical shift of the methyl protons in DMSO due to the nanoparticles was studied by NMR spectroscopy, which indicated that the cobalt particles were ferromagnetic. The structural design modification and surface area of Co₃O₄ was improved by adding the ZnO component. DFT calculations were done to validate the nano structure. Supercapacitance ability of the nanoparticles was studied by cyclic voltammetry, and electrochemical calculations were performed to determine the microelectronic characteristics of the material. The specific capacitance was estimated at 207.3 and 51.1 F g⁻¹ for the ZnO·Co₃O₄ and Co₃O₄ electrodes, respectively. Clearly, ZnO·Co₃O₄ exhibited a much higher specific capacitance than the Co₃O₄ nanocrystal, which was attributed to better conductivity and higher surface area. The capacitance activity showed multifold enhancement due to the porous nature of Zn oxide in the heterometallic nano ZnO·Co₃O₄ composite.