The Preparation And Electrochemical Performance Of Porous Cobalt-based Oxides

Metal organic matrix materials(MOFs)have the characteristics of large specific surface area,high porosity,tunable pore size and functional properties,which have become representative materials in porous materials.Using MOFs as the template for the preparation of porous metal oxide semiconductor because of inherited characteristics of MOFs in its structure,with mechanical properties,optical properties and excellent electrochemical performance unique,has been a lot of attention in research,and are widely used in the fields of catalysis,energy storage,drug release and biosensors.In this paper,ZIF-67 was used as the precursor,and zinc and carbon were successfully introduced by chemical coprecipitation method and corresponding heat treatment.Bimetallic oxide Zn0.35Co2.65O4 and core-shell complexes CoO@Co3O4/C were synthesized for electrochemical glucose sensor,electrocatalytic production Oxygen and supercapacitor electrode materials.The main contents are as follows:(1)Using ZIF-67 as template,bimetallic oxide Zn0.35Co2.65O4 was synthesized by chemical coprecipitation method,and The morphologies,crystal structure,and chemical composition of bimetallic oxide were characterized by Scanning Electron Microscope,Transmission Electron Microscope,X-Ray Diffraction and X-Ray Photoelectron Spectroscopy techniques.When the electrolyte is PBS solution of pH=7.4,the electrode exhibits an outstanding performance for determining glucose with a wide window of 13.28 μM-13 mM,a sensitivity of 47.71 μA mM-1cm-2,a low detection limit of 1.3 μM(S/N=3),and fast response time(<3 s).When the electrolyte is 0.1M NaOH solution,the electrode exhibits an outstanding performance for determining glucose with a wide window of 5 μM-13 mM,a sensitivity of 41.8 μA mM-1 cm-2,a low detection limit of 1.41 μM(S/N=3),and fast response time(<2 s).By comparing the performance with Co3O4,the effect of Zn ion introduction on the performance of the sample in glucose detection was analyzed.As a result,it was found that the sample was subjected to enzyme-free glucose detection at pH 7.4 and alkaline solution.(2)With ZIF-67 as precursor,the sample CoO@Co3O4/C composites with core-shell structure was obtained by soaking the glucose solution with surface modification of the samples and annealing heat treatment.The morphologies,crystal structure,and chemical composition of CoO@Co3O4/C composites were characterized by SEM,High Transmission Electron Microscope,XRD and XPS techniques Combined with cyclic voltammetry,constant current charge discharge,AC impedance spectroscopy,and linear voltammetry scanning methods,the properties of composite materials in capacitance and electrocatalytic oxygen evolution were investigated.The results show that the specific capacitance of the sample can reach 184 F g-1 at a current density of 1 mA cm-1.Under the current density of 10 mA cm-1,the overpotential value of CoO@Co3O4/C was 386 mV.And after 6 h stability test,the catalyst remained 83.1% of the original current density.By comparing the specific capacitance and overpotential of the material with Co3O4,we analyzed the influence of the existence of carbon elements on the sample surface and the core-shell structure on the electrochemical properties of the sample.The test results show that the performance of CoO@Co3O4/C has been greatly enhanced both in capacitive and electrocatalytic oxygen evolution.At the same time,combined with surface photovoltaic and transient photovoltaic technologies,the photoinduced charge transfer behavior and transfer mechanism of core-shell composite materials were investigated.The results show that the carbon in the sample has good electron transport and acceptability,and the covalent structure of cobalt-based oxide and carbon accelerates the efficient transmission and separation of photogenerated carriers.The core-shell composite has a longer lifetime to participate in photoelectric reaction,so the sample has good photoelectric properties.