| Currently,around the two major problems facing the world,such as energy crisis and environmental pollution,both science and industry have taken fruitful initiatives,and a number of potential technologies have been born one after another.Among them,electrochemical and photochemical technologies are considered to be the more desirable green technologies.Electrochemical technology is applied to electrolytic water,electro synthesis,electro degradation,supercapacitor,secondary battery,fuel cell,zinc-air battery,etc.It involves energy generation,conversion,storage and environmental pollution control,and the core of its technology is the quality of electrode materials.At present,electrode materials used more in electrochemistry are precious metal-based materials,carbon materials and inorganic non-metallic materials,etc.,but each has its own advantages and disadvantages,and there is an urgent need to develop new alternative precious metal efficient electrode materials,which is also one of the frontier hot spots in the research of materials,chemical,chemical and energy disciplines.In the research of electrode materials,composite materials integrate the functions of different monomer components and can also derive sexual functions,which can greatly improve the performance of electrode materials and therefore attract much attention.Based on the existing research on metal-organic framework materials(MOFs)and two-dimensional transition metal carbides and nitrides(MXenes),we have taken advantage of the easily adjustable components,porosity,high specific surface area and modifiability of MOFs and the high specific surface area,high electrical conductivity,adjustable components,controllable nano-layer thickness and acid-base resistance of MXenes to make up for the shortcomings of these two monomers.The new composites were constructed by combining two monomers and two monomers with hydroxide to make up for their own deficiencies,and the electrocatalytic oxygen precipitation(OER)and supercapacitor performance(SC)were investigated to elucidate the electrochemical mechanism,and some regular conclusions were obtained to provide valuable information for the research of these composites.The main work of the paper is as follows.Part I:Reviewed the research progress of two composite monomer materials,MOFs materials and MXenes materials,summarized the applications of the two types of materials,and briefly described the basis for the selection of the thesis.Part II:Constructing three-dimensional graded Ni Co-MOF@Ni1-xCox(OH)2heterostructures by combining heterometallic MOF with heterometallic hydroxide(TMH).The Ni1-xCox(OH)2 nanoflowers with graded structures were pre-designed and synthesized,and Ni Co-MOF nanosheets were grown in situ on the nanoflowers by the solvent thermal method using them as the precursor metal source and semi-sacrificial agent template,and 1,4-benzenedicarboxylic acid(BDC)as the organic assembly building block to assemble and construct the three-dimensional graded Ni Co-MOF@Ni1-xCox(OH)2 heterogeneous structure.By adjusting the amount of BDC,a series of heterostructures with different ratios were obtained.The optimized MOF@TMH-2 sample is a three-dimensional graded heterostructure constructed based on the assembly of ultrathin nanosheets with the thickness of 1.7?1.77 nm,and its specific capacitance is 1855.3 F/g at a current density of 2 A/g,and it has good multiplicative performance and stability.In addition,MOF@TMH-2 also exhibits good electrocatalytic oxygen precipitation(OER)activity at current densities of 10 and 100 m A/cm2,corresponding to overpotentials of 193 m V and 310 m V,respectively,which is superior to single Ni Co-MOF and Ni1-xCox(OH)2 components,and even to most of the reported electrocatalytic materials,and the above can be attributed to The graded heterogeneous structure has abundant active centers and high electrochemical reactivity.Part III:NiMn-LDH/MXene/NF composites were constructed by compounding MXene with good electrical conductivity and abundant surface functional groups with layered double hydroxide(LDH)having a large number of redox reaction sites.Two-dimensional layered MXene(V2C)material was firstly obtained by hydrofluoric acid(HF)etching of MAX(V2Al C)material,and secondly,different contents of V2C were attached to nickel foam by ultrasonic dispersion method,and then NiMn-LDH/(V2C)w(w=10-50 mg)/NF material was obtained by reacting with metal salts in hydrothermal system using it as a template.The best SC performance of composite performance was obtained when the compound amount of MXene was 30 mg,and the specific capacitance was 1600 F/g at a current density of 1 A/g,and the specific capacitance was maintained at 90.5%by 1000 cycles stability test at a current density of 3 A/g,with good stability and good multiplicative performance.In addition,the self-assembled asymmetric supercapacitor with NiMn-LDH/MXene/NF-3 as the positive electrode and activated carbon(AC)as the negative electrode has a high specific capacitance(70.7 F/g,0.1 A/g)and maintains an initial specific capacitance of 93.3%after 6000 constant current charge/discharge cycles,and can obtain an energy of 22.1 Wh/Kg at a power density of 66.6W/Kg.Part IV:The Ni-MOF/MXene heterogeneous materials were constructed by compounding MXene,which has good electrical conductivity and abundant surface functional groups,with Ni-MOF.Firstly,we selected an aromatic polycarboxylic acid organic component 4,4',4'',4'''-benzene-1,2,4,5-tetrayl-tetrabenzoic acid(BTTB)to construct three Ni-MOFs suitable for electrocatalytic studies,tested the crystal structure,and performed basic physicochemical characterization.The three examples of Ni-MOFs are as follows:{[Ni(BTTB)0.5(H2O)2]}n1{[Ni(BTTB)0.5(4,4'-bpy)0.5(H2O)2]}n2{[Ni(BTTB)0.5(bpe)0.5(H2O)]·DMF}n3Three cases of Ni-MOF were tested by SC performance and found that the SC performance of 2D crystalline material 2 was relatively the best;to improve the electrical conductivity and chemical stability of the MOFs materials,they were in situ compounded with three types of MXene nanosheets under hydrothermal conditions,and the influence law of the class of MXene and the amount of compounding on the SC performance of the composite electrodes was explored.It was found that the enhancement effect of introducing V2C-MXene was relatively good,and the best supercapacitance performance was relatively obtained when the addition amount was 3 mg/m L,and the specific capacitance was 244.4 F/g at a current density of 0.5A/g,along with good multiplicative performance and stability.Part V:A summary and outlook of the thesis work. |
PDF Full Text Request