| Energy conversion and storage research is of great significance to green and sustainable development.At present,in the field of new clean energy storage,the hydrogen energy produced by electrocatalytic water splitting has the characteristics of completely clean and pollution-free,and the supercapacitor has the advantages of fast response speed,high power density and high safety performance.However,the high overpotential of electrocatalytic water splitting limits the industrial application of electrolyzed water,and the low energy density limits the wide application of supercapacitors.In the materials that have been reported in the world,transition metal sulfides,due to the characteristics of low cost and high electronic conductivity,have not only shown significant performance in supercapacitor energy storage(high theoretical capacitance),but also in electrocatalysis(high intrinsic activity).However,the lower effective specific surface area causes the actual performance of a single sulfide to be much lower than the theoretical value.Nanowires with high aspect ratios have significant advantages as electrocatalytic and supercapacitor electrode materials,but such materials prepared by traditional methods are prone to agglomeration,or the bonding force with the matrix is poor,which makes their cycle stability unable to meet practical applications claim.In response to the above problems,this paper designs and prepares a composite structure that combines the advantages of one-dimensional and nano-particles or two-dimensional materials,which increases the active area while solving the problems of poor cycle stability and low electrocatalytic activity.By hydrothermal chemical etching,a network structure of Ni3S2 nanowires intertwined was grown in situ on the surface of nickel foam(NF),and then nanoparticle Fe2O3 and nanosheet Cu(OH)2 were deposited on the surface of Ni3S2 nanowires.Two electrode materials,Fe2O3@Ni3S2 and Cu(OH)2@Ni3S2,were successfully prepared;the reaction kinetic mechanism of surface coating was discussed,and the morphology and structure of the nano coating layer were further optimized;on this basis,a systematic study The electrocatalytic performance of nickel foam supported Fe2O3@Ni3S2,and the energy storage performance and electrocatalytic performance of Cu(OH)2@Ni3S2 are analyzed.(1)Preparation of Fe2O3@Ni3S2 nanostructure supported by foamed nickel and its OER electrocatalytic performanceThe surface layer of the nickel foam substrate is chemically etched by the hydrothermal method,and a network structure of Ni3S2 nanowires is grown in situ,and then Fe2O3 nanoparticles are grown on the surface to form a composite nanostructure.Based on the study of the influence of reaction parameters on the product,it can be known that the appropriate Fe2+concentration and hydrothermal reaction temperature make the nanoparticles grow on the nanowires at intervals,and the optimal preparation conditions are obtained.For the oxygen evolution reaction of electrolyzed water,the electrocatalytic performance of the nickel foam supported Fe2O3@Ni3S2 catalyst is significantly improved compared with that of the nickel foam supported Ni3S2,and it exhibits a very low overpotential of 223 m V at a high current density of 100 m A/cm2.This is because the ultra-long Ni3S2 nanowires have high aspect ratio and high specific surface area,providing a stable structure for electrochemical reactions;Fe2O3nanoparticles contain a large number of lattice defects,which provide more active sites for catalytic reactions.For these reasons,the composite nanostructured nickel foam supported Fe2O3@Ni3S2 catalyst exhibits excellent OER catalytic performance.(2)Study on the energy storage and OER electrocatalytic performance of nickel foam supported Cu(OH)2@Ni3S2On the basis of nickel foam loaded with Ni3S2 nanowires,two-dimensional Cu(OH)2 nanosheets were grown on the surface of Ni3S2 nanowires by chemical deposition,and two-dimensional Cu(OH)2 nanosheets@one-dimensional Ni3S2nanowires heterogeneous structure wre successfully prepared.The electrochemical energy storage and oxygen evolution electrocatalytic properties of the nickel foam supported Cu(OH)2@Ni3S2 material were studied in detail.The results show that as a supercapacitor electrode,the nickel foam loaded Cu(OH)2@Ni3S2 exhibits excellent cycle stability;at a current density of 20 m A/cm2,after 4800 cycles of charge and discharge,the specific capacitance increases by 18.2%;even after 35,000 cycles of charging and discharging,the electrode specific capacitance remained above 110%of the initial value,and the coulombic efficiency remained at 95.6%±0.5%.The assembled solid-state device has good reversibility in the charge and discharge process,and the cycle stability is still outstanding:at a high current density of 50 m A/cm2,after30,000 charge and discharge cycles,the specific capacitance retention rate is always above 98%.In terms of electrocatalytic oxygen evolution,the material in 1 M KOH solution,at a very high current density(100 m A/cm2),the corresponding OER overpotential is only 345 m V;the stability test results of chronopotentiometry show that working for 10 hours at a current density of 100m A/cm2,the performance retention rate is 90%.This is because the Ni3S2 nanowires grown by in-situ etching on the surface provide a stable interface bonding force and ensure the stability of the electrode material;the heterostructure of nanowires and nanosheets can accelerate electron transfer. |
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