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.
Highlights
Transition metal oxides have gained considerable interest in recent years owing to their interesting magnetic, optical eld emission and biomedical applications
On the basis of the Transmission electron microscopy (TEM) images, it can be concluded that particle overlap occurred and that different long nanoconjugates were obtained by interfacial reactions and agglomeration
The Co3O4 and mixed oxide Zno$Co3O4 nanoparticles prepared by calcination of the [Co/Zn(II)benzaldehyde$piperazine$H2O] complex at 500 C were characterized by energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM) and TEM
Summary
Many synthetic techniques and routes have been utilized to prepare these nanomaterials, including sol–gel methods,[6] solvothermal synthesis,[7] thermal decomposition of cobalt precursors,[8] sonochemical methods,[9] co-precipitation[10] and microwaveassisted methods.[11] Most of these methods are not feasible for large-scale production owing to the expensive and toxic chemicals required and the use of complex instruments. Researchers are looking for more facile synthetic routes to obtain new nanomaterials of mixed valence oxides by choosing appropriate precursors, which have potential advantages including high yield. We have undertaken the task of preparing homo and hetero-metallic Co3O4, ZnO$Co3O4 mixed-valence oxides possessing different structural morphologies and electrochemical behaviour.[12,13] In this work, we report a new modi ed calcination process that uses the coordination chemistry concept of employing piperazine and aldehyde with metal salts to obtain a uniform single crop of nano Co3O4 and porous ZnO$Co3O4 crystals. The obtained heterobimetallic nanomaterials have mixed oxidation sates, which helps build up the inner electric eld at the junction interface and create more pores in the porous material.[15,16]
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