Preparation And Electrochemical Properties Of Two-dimensional Sheets And Its Composites

With the increasingly serious energy problems,it is becoming one of the most pressing problems to reduce the consumption of non-sustainable energy sources.The irrational energy depletion is the main reason for energy problem.Electrical energy is the energy utilized efficiently.In the development of modern society,one of the important ways to solve the energy problem is finding large-capacity energy storage devices.As a new energy storage device,the supercapacitor is gradually becoming a hot topic for some researchers due to its characteristics about fast charging and constant current stable discharging.The electrode material is the critical factor to determine the performance of supercapacitor.Two-dimensional material is becomg a hot topic due to its ultrathin and infinite planar.Therefore,two-dimensional electrode materials with superior performance were prepared in this article.And we explore the feasibility of a high-performance supercapacitor electrode material by a testing of electrochemical properties.At first,a sandwich-like composite for application as a pseudocapacitor is prepared via electrostatic assembly of Co-Al LDHs nanosheets and CNTs.The main preparation process is as following:Firstly,the Co-Al LDHs nanosheets were obtained via the exfoliation of Co-Al LDHs.The Co-Al LDHs is the cationic layered material,so the exfoliated nanosheets are positively charged.Secondiy,the negatively charged functional groups on the surfaces of CNTs was obtained by treatment of carboxylation reaction and sodium hydroxide liquid.Both of the materials are dispersed into formamide according to a certain percentage.The self-assembled composite is produced quickly utilizing the electrostatic attraction force.The sandwich-like composite is superimposed by CNTs and Co-Al LDHs nanosheets.The compound has both a large specific surface area and liquid contact area,and good electrical conductivity and transmission efficiency of charged.So the performance of composite has been greatly improved over the Co-Al LDHs.This modified method of two-dimensional material is simple,easy to operate and low cost,so it can be used to produce the most two-dimensional composite.Secondly,nickel sulfide nanosheets array grown on the surface of nickel foam?named as NiS-NF?were synthetized via a simple soaking method.The main preparation process is as following:The precursor of nickel hydroxide grown onto the surface of nickel foam?named as Ni?OH?2-NF?was prepared by the etching nickel foam using hydrochloride.In the Autoclave,the nickel foam reacts with the hydrochloric acid solution.Then Ni?OH?₂-NF growning on the nickel foam substrate occurs ion exchange reaction in NaHS solution.The NiS-NF with the same structure of nickel nanosheet is produce.The electrochemical performance tests shows the two materials have excellent electrochemical performance.Others,due to the novel structure and unique electrode reaction of nickel sulfide nanosheet,NiS-NF has a higher performance than the Ni?OH?₂-NF.The purpose of this process is improving the dispersion and conductive properties of two-dimensional material by growing onto substrate.Growing onto substrate also can improve the electrochemical performance of the two-dimensional material.