Construction And Multifunctional Electrochemical Properties Of Co₃O₄-NiCo₂O₄ And ZIF-67@w-NiSO₄·NiS₂ Nanocomposites

With the continuous improvement of material living standards,environmental pollution,human health and energy crisis have gradually become one of the key factors which restricting human sustainable development.Chemically modified electrodes with their high sensitivity,low detection limit,and excellent stability have become important tools for detecting environmental pollution and life interference.As an energy storage device,supercapacitors have also become an advanced technology to alleviate the energy crisis due to its high energy/power density,fast charge/discharge rate and long cycle life.Electrode materials are at the heart of the performance of supercapacitors and electrochemical sensors.The development of materials with more electroactive sites and better energy storage performance is the focus of research on the construction of high-performance supercapacitors and enzyme-free sensors.In Chapter 2,a spinel oxide based strongly coupled Co₃O₄-Ni Co₂O₄ electrode material was prepared,which can be used for fast and efficient biomolecule detection and energy storage applications.Using porous Co₃O₄ nanosheets as growth points,Ni Co₂O₄ nanorods were anchored on the surface of Co₃O₄ to form porous Co₃O₄-Ni Co₂O₄ nanosheets.The scanning electron microscope(SEM),transmission electron microscope(TEM),and X-ray photoelectron spectroscopy(XPS)were carried to confirm the nanostructure and composition of the material.Under the optimal conditions,the sensors based on Co₃O₄-Ni Co₂O₄nanosheets show high electrochemical sensitivity to glucose oxidation and hydrogen peroxide reduction,which are 1463.13?A/(mmol/L·cm²)and 303.42?A/(mmol/L·cm²);The detection limits are as low as 0.112?mol/L and 0.596?mol/L,and both have good selectivity and reproducibility.Co₃O₄-Ni Co₂O₄ coated nickel foam electrode can be used in supercapacitors.It can achieve a high specific capacitance of 1041.2 F/g at a current density of 2 A/g.No significant capacitance attenuation after 5000 cycles at a current density of 5 A/g.The Chapter 3 builds an electrochemical sensor based on ZIF-67@w-NiSO₄·NiS₂composite material for rapid detection of metronidazole(MNZ).ZIF-67 was used as the growth substrate and w-Ni SO₄·Ni S₂ was coated on the surface of ZIF-67 by hydrothermal and subsequent calcination.The nanostructure and composition of the material were confirmed by SEM,TEM,FT-IR and XPS.The sensitivity of ZIF-67@w-NiSO₄·NiS₂ sensor for MNZ detection is 1977.14?A/(mmol/L·cm²),the LOD is as low as 0.009?mol/L,and the linear range is 1?200 and 200?1000?mol/L.The modified sensor can resist interference from multiple traditional living matter,and has good reproducibility,repeatability and stability.The improved performance is attributed to the improved nano-spherical structure.The w-Ni SO₄·Ni S₂ coated on ZIF-67 irregular particles inhibits the stacking of w-Ni SO₄·Ni S₂nanosheets,which makes more catalytic sites Exposed,thereby increasing the catalytic activity of MNZ.High catalytic activity requires effective molecular transport and exposure of active sites.The successful construction of ZIF-67@w-NiSO₄·NiS₂ nanostructures promotes the dispersion of materials on the electrode surface and the migration of reactants on the electrode surface.The activity during multiple catalytic cycles facilitates the full exposure of active sites to achieve high-sensitivity MNZ sensor detection.