Study On Preparation And Application Of MnO₂ Based Capacitor Electrode Composite Material

The theoretical pseudocapacitance of manganese dioxide material with wide sources,low cost and good environmental compatibility is high?1380 g/F?,so it has great development and application prospects as capacitor electrode material.However,its poor conductivity,proton ion transport and easy stacking of grains result in less active area,which seriously limits the full utilization of its intrinsic capacitance.Therefore,the electrode design and practical research of capacitance deionization technology with low cost,high adsorption capacity,stability and large specific surface area are studied,aiming at the removal of lead ions in water and the controllable construction and development of high capacitance,low-cost,long-life and high-efficiency electrode materials of supercapacitor in water system,and the electrodeposition method suitable for precise control and easy engineering application is selected for preparation.Therefore,in this paper,3D nanostructured nickel foam is selected as the structural body,and the conductive material is poly 2,5-dimethoxyaniline?PDMA?,which has similar properties to PANI as the bottom layer to further reduce internal resistance and provide surface nucleation“interfaces”,provide part of the capacitance,metal elements?CO,Mo?doping to introduce defects and regulate the MnO₂ structure to improve the interface reaction,Faraday process mass transfer and cycle structure stability.In the CDI chapter,we discussed the actual Pb²⁺adsorption performance and the electrochemical performance of the composite in the super electricity chapter,in order to promote the development of MnO₂ capacitor electrode in both.The main work of this paper is as follows:?1?a simple two step anode electrodeposition was used to design the two layer structure of NF/PDMA/MnO₂-Co foam nickel framework.After adding the bottom layer of PDMA,the growth orientation of MnO₂-Co layer was significantly changed,and the cross-linked nano villi structure was formed,and some areas were clustered into special morphology.The unique design and morphology made the capacitance performance and adsorption performance significantly increased.Compared with NF/MnO₂-Co electrode and NF/PDMA electrode,the capacitance is increased by 305.4%and 94.2%respectively,NF/PDMA/MnO₂-Co electrode can reach 208.8 F/g,and the removal rate of NF/PDMA/MnO₂-Co electrode is increased by 2.05 and 1.31 times respectively,and the composite electrode is up to 41.8%.The adsorption kinetics fit indicates that the adsorption process is controlled by a mixture of physical and chemical adsorption,and is limited by the mass transfer of ions and diffusion within the pores.After four cycles of adsorption/desorption,the adsorption of NF/PDMA/MnO₂-Co electrode decreased by 13.7%,with the highest removal rate of 36%?adsorption capacity of 51.7 mg/g?.?2?The sandwich electrode NF/Cu/PDMA/MnO₂-Co-Mo with three-layer structure was designed by three-step electrodeposition.The surface layer showed the vertical growth of cross-linked nanoflakes and gully network structure,and obtained the ion electron transport path and large active surface area which are easy to penetrate and diffuse the electrolyte.At 1 A/g,three-layer NF/Cu/PDMA/MnO₂-Co-Mo electrode jointly contributes a considerable capacitance of 432.22 F/g,which is 6.09 times and1.86 times higher than NF/MnO₂-Co-Mo and NF/Cu/MnO₂-Co-Mo,even at a high current density of 7.5 A/g,it also maintains 75.1%of 1A/g.EIS showed the high conductivity and rapid diffusion properties of the three-layer electrode.After 2000cycles of impulse/discharge,the sandwich electrode still had 73%retention.The decrease of stability after cycling is mainly due to the fast charge/discharge Faraday reaction with large number of times,which causes the corrosion of the surface layer,the collapse of the nanostructure and the damage of the conductive grid.