CN113077991B - MXene/nickel phosphate electrode material and preparation method and application thereof - Google Patents
MXene/nickel phosphate electrode material and preparation method and application thereof Download PDFInfo
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- JOCJYBPHESYFOK-UHFFFAOYSA-K nickel(3+);phosphate Chemical compound [Ni+3].[O-]P([O-])([O-])=O JOCJYBPHESYFOK-UHFFFAOYSA-K 0.000 title claims abstract description 162
- 229910000159 nickel phosphate Inorganic materials 0.000 title claims abstract description 161
- 239000007772 electrode material Substances 0.000 title claims abstract description 125
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000002135 nanosheet Substances 0.000 claims abstract description 60
- 239000000463 material Substances 0.000 claims abstract description 50
- 238000006243 chemical reaction Methods 0.000 claims description 64
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 54
- 238000002156 mixing Methods 0.000 claims description 43
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 42
- 238000005530 etching Methods 0.000 claims description 42
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims description 40
- 239000000243 solution Substances 0.000 claims description 37
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 32
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 30
- 229910000402 monopotassium phosphate Inorganic materials 0.000 claims description 30
- 235000019796 monopotassium phosphate Nutrition 0.000 claims description 30
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 claims description 30
- 238000000034 method Methods 0.000 claims description 23
- 238000004729 solvothermal method Methods 0.000 claims description 23
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 238000005342 ion exchange Methods 0.000 claims description 17
- 150000004673 fluoride salts Chemical class 0.000 claims description 15
- 229910001512 metal fluoride Inorganic materials 0.000 claims description 15
- 239000003960 organic solvent Substances 0.000 claims description 14
- 239000011259 mixed solution Substances 0.000 claims description 11
- 239000002904 solvent Substances 0.000 claims description 5
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 4
- 239000010410 layer Substances 0.000 abstract description 65
- 239000002131 composite material Substances 0.000 abstract description 11
- 239000011229 interlayer Substances 0.000 abstract description 9
- 150000002500 ions Chemical class 0.000 abstract description 9
- 238000013508 migration Methods 0.000 abstract description 5
- 230000005012 migration Effects 0.000 abstract description 5
- 238000012546 transfer Methods 0.000 abstract description 5
- 238000009830 intercalation Methods 0.000 abstract description 4
- 230000002687 intercalation Effects 0.000 abstract description 4
- 239000012621 metal-organic framework Substances 0.000 description 39
- 238000005406 washing Methods 0.000 description 34
- 238000001035 drying Methods 0.000 description 20
- 238000003756 stirring Methods 0.000 description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 16
- 239000008367 deionised water Substances 0.000 description 15
- 229910021641 deionized water Inorganic materials 0.000 description 15
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 14
- 238000001878 scanning electron micrograph Methods 0.000 description 12
- 239000000047 product Substances 0.000 description 11
- 239000010936 titanium Substances 0.000 description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 238000004108 freeze drying Methods 0.000 description 7
- 229910000319 transition metal phosphate Inorganic materials 0.000 description 7
- -1 transition metal salts Chemical class 0.000 description 7
- 238000003917 TEM image Methods 0.000 description 6
- 239000006229 carbon black Substances 0.000 description 6
- 125000000524 functional group Chemical group 0.000 description 6
- 238000000227 grinding Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 6
- 239000004810 polytetrafluoroethylene Substances 0.000 description 6
- 238000001291 vacuum drying Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 5
- 238000010981 drying operation Methods 0.000 description 5
- 239000003446 ligand Substances 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 229910021389 graphene Inorganic materials 0.000 description 4
- 239000002243 precursor Substances 0.000 description 4
- 238000000967 suction filtration Methods 0.000 description 4
- 239000011149 active material Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 239000008151 electrolyte solution Substances 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 239000006260 foam Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- 229910000474 mercury oxide Inorganic materials 0.000 description 3
- UKWHYYKOEPRTIC-UHFFFAOYSA-N mercury(ii) oxide Chemical compound [Hg]=O UKWHYYKOEPRTIC-UHFFFAOYSA-N 0.000 description 3
- 230000000877 morphologic effect Effects 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- 239000012917 MOF crystal Substances 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 238000005034 decoration Methods 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 238000002604 ultrasonography Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 description 1
- 229910018553 Ni—O Inorganic materials 0.000 description 1
- HIDACJPWCRPEDW-UHFFFAOYSA-K P(=O)([O-])([O-])[O-].[Ni+2].[Co+2] Chemical compound P(=O)([O-])([O-])[O-].[Ni+2].[Co+2] HIDACJPWCRPEDW-UHFFFAOYSA-K 0.000 description 1
- 241001128148 Pelagostrobilidium liui Species 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910009817 Ti3SiC2 Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- LDDQLRUQCUTJBB-UHFFFAOYSA-N ammonium fluoride Chemical compound [NH4+].[F-] LDDQLRUQCUTJBB-UHFFFAOYSA-N 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- ZGDWHDKHJKZZIQ-UHFFFAOYSA-N cobalt nickel Chemical compound [Co].[Ni].[Ni].[Ni] ZGDWHDKHJKZZIQ-UHFFFAOYSA-N 0.000 description 1
- 230000005595 deprotonation Effects 0.000 description 1
- 238000010537 deprotonation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 239000003792 electrolyte Substances 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000002149 hierarchical pore Substances 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 235000003270 potassium fluoride Nutrition 0.000 description 1
- 239000011698 potassium fluoride Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 235000013024 sodium fluoride Nutrition 0.000 description 1
- 239000011775 sodium fluoride Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
Abstract
The invention relates to the technical field of electrode materials, and provides an MXene/nickel phosphate electrode material and a preparation method and application thereof. The MXene/nickel phosphate electrode material provided by the invention is anchored on the surface of the MXene nanosheet layer, so that the interface transfer resistance between the composite materials is reduced, and the conductivity of the composite materials is improved; the intercalation growth of the nickel phosphate widens the interlayer spacing of the MXene sheets among the MXene sheets and becomes an interlayer strut of the MXene sheets, the structural stability of the material is enhanced while the ion migration is promoted, and the excellent electrochemical performance of large specific capacitance, high stability and high conductivity is shown.
Description
Technical Field
The invention relates to the technical field of electrode materials, in particular to an MXene/nickel phosphate electrode material and a preparation method and application thereof.
Background
The demand of portable electronic devices and the non-uniformity of the space-time distribution of new energy generation have presented a great challenge to the development and innovation of energy storage devices. Among many energy storage devices, the super capacitor is expected to meet the above challenges by virtue of its safety, stability, fast charging, and wide power density interval, and becomes the mainstream energy storage device of the next generation. The relatively poor stability and energy density of supercapacitors are critical factors that limit their practical production applications.
The transition metal phosphate has the characteristics of higher theoretical specific capacitance, rich reserves, environment friendliness and biological friendliness, and the structural stability of the transition metal phosphate is greatly enhanced due to the existence of a firm P-O bond in the structure of the transition metal phosphate, so that the transition metal phosphate is considered as an ideal electrode material of the supercapacitor. Among them, nickel phosphate is favored by researchers because of its excellent electrochemical performance. However, nickel phosphate, although exhibiting several times superior specific capacitance compared to other transition metal phosphates, still has its stability and conductivity itself to be improved.
The existing methods for solving the problem are common in the following methods: doping the transition metal phosphate with other metal elements, and adjusting the proportion of the metal elements to play a synergistic effect among different transition metal salts so as to obtain the high-stability transition metal phosphate taking nickel phosphate as a main component. For example, the prior art (l.tao, j.li, q.zhou, h.zhu, g.hu, j.huang, j.alloys company.2018, 767,789.) discloses that by doping nickel phosphate with metallic cobalt element, the resulting electrode material is 1A g-1Has 630.4C g at a current density of-1The specific capacity and the stability after 1000 cycles are improved by 38 percent compared with the stability of pure nickel phosphate. However, the scheme has the problems of difficult regulation, easy occurrence of obvious phase separation among materials and poor conductivity of the materials. And the second step is as follows: selecting MOFs (cobalt nickel metal organic framework) as a precursor, and carrying out exchange of ligand ions and phosphate radicals through hydrothermal reaction, wherein the cobalt nickel phosphate prepared by the method is 1A g-1808C g at current density-1The specific capacity and the stability of 72.46 percent of the initial capacity are maintained after 2000 times of circulation. However, this approach is difficult to achieve complete exchange of MOFs ligand ions, and thus has poor stability and specific capacitance (z.xiao, y.bao, z.li, x.huai, m.wang, p.liu, l.wang, acsappl.energymater.2019,2,1086.). And thirdly: anchoring nickel phosphate on the surface of the graphene sheet layer to obtain the composite material of graphene and nickel phosphate, wherein the composite material is 0.5A g compared with pure nickel phosphate-1Exhibits a current density of 48mAh g-1The specific capacitance of the composite material is far better than that of common nickel phosphate, the capacity can still keep 92% of the original capacity after 2000 cycles, but due to limited functional groups on the surface of graphene, stable chemical bonds are difficult to form between the nickel phosphate and the graphene, so that the specific capacity is low, and the electrochemical performance is still unsatisfactory (A.A.Mirghni, M.J.MADito, K.O.Oyedotun, T.M.Masikhwa, N.M.Ndiaye, S.J.ray, N.Manyala, RSCAdv.2018,8,11608.).
Therefore, although various schemes are provided to optimize the electrochemical performance and stability of the nickel phosphate electrode material, the conductivity, specific capacitance and stability of nickel phosphate cannot be improved simultaneously by the above methods. Therefore, a nickel phosphate electrode material having a large specific capacitance, excellent stability and high conductivity, and a method for preparing the same are needed.
Disclosure of Invention
The invention aims to provide an MXene/nickel phosphate electrode material, and a preparation method and application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides an MXene/nickel phosphate electrode material which comprises an MXene sheet layer and nickel phosphate balls, wherein the nickel phosphate balls are anchored on the surface of the MXene nanosheet layer and are intercalated between the MXene nanosheet layers.
Preferably, the specific surface area of the MXene/nickel phosphate electrode material is 100-180 m2/g。
The invention also provides a preparation method of the MXene/nickel phosphate electrode material, which comprises the following steps:
(1) mixing the MAX phase material with metal fluoride salt and hydrochloric acid to carry out a first etching reaction to obtain an intermediate; mixing the intermediate with hydrofluoric acid to perform a second etching reaction to obtain an MXene nanosheet layer;
(2) mixing nickel nitrate hexahydrate, terephthalic acid, an organic solvent and the MXene nanosheet layer obtained in the step (1), and carrying out solvothermal reaction to obtain MXene-MOF;
(3) mixing the MXene-MOF obtained in the step (2) with a potassium dihydrogen phosphate solution, and carrying out an ion exchange reaction to obtain the MXene/nickel phosphate electrode material.
Preferably, the mass ratio of the nickel nitrate hexahydrate, the terephthalic acid and the MXene nano-sheet layer in the step (2) is (0.3-3): (0.1-1): 0.05-0.2).
Preferably, the organic solvent in step (2) comprises one or more of N, N-dimethylformamide, N-dimethylacetamide and ethylene glycol.
Preferably, the temperature of the solvothermal reaction in the step (2) is 100-150 ℃, and the time of the solvothermal reaction is 3-12 h.
Preferably, the mass ratio of MXene-MOF in the step (3) to potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution is (0.7:1) - (1: 3).
Preferably, the solvent of the potassium dihydrogen phosphate solution in the step (3) is a mixed solution of ethylene glycol and water.
Preferably, the temperature of the ion exchange reaction in the step (3) is 120-170 ℃, and the time of the ion exchange reaction is 2-9 h.
The invention also provides an application of the MXene/nickel phosphate electrode material in the technical scheme or the MXene/nickel phosphate electrode material prepared by the preparation method in the technical scheme in a supercapacitor electrode material.
The invention provides an MXene/nickel phosphate electrode material which comprises an MXene sheet layer and nickel phosphate balls, wherein the nickel phosphate balls are anchored on the surface of the MXene nanosheet layer and are intercalated between the MXene nanosheet layers. The MXene/nickel phosphate electrode material provided by the invention is anchored on the surface of the MXene nanosheet layer, so that the interface transfer resistance between the composite materials is reduced, and the conductivity of the composite materials is improved; the intercalation growth of the nickel phosphate widens the interlayer spacing of the MXene sheets and becomes an interlayer strut of the MXene sheets, the structural stability of the material is enhanced while the ion migration is promoted, and the excellent electrochemical performance of large specific capacitance, high stability and high conductivity is shown. The experiment result shows that the MXene/nickel phosphate electrode material provided by the invention has obvious redox peaks on CV curves at different sweep rates, and has excellent electrochemical properties; specific capacitances were 639.5, 606.2, 537.6, 444.7, 391.2, 330 and 285C/g, respectively, at current densities of 0.5, 1, 2, 5, 10, 15 and 20A/g, indicating excellent capacitive properties; at a current density of 5A/g, 85% of the final capacity can be maintained after 10000 cycles, and excellent cycling stability is shown.
Drawings
Fig. 1 is an SEM image of an MXene nanosheet made in example 1 of the present invention;
FIG. 2 is an SEM image of MXene-MOF prepared in example 1 of the present invention;
FIG. 3 is an SEM image of MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
FIG. 4 is an XRD pattern of MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
FIG. 5 is an FTIR plot of MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
FIG. 6 is an XPS plot of MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
FIG. 7 is a TEM image of MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
fig. 8 is an adsorption and desorption curve diagram of the MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
FIG. 9 is a graph of CV for electrodes made from MXene/nickel phosphate electrode materials made in example 1 of the present invention;
FIG. 10 is a graph of the GCD of an electrode made of MXene/nickel phosphate electrode material made in example 1 of the present invention;
FIG. 11 is a graph showing the cyclic charge and discharge curves of an electrode made of MXene/nickel phosphate electrode material prepared in example 1 of the present invention;
fig. 12 is an SEM image of an MXene nanosheet made in example 2 of the present invention;
FIG. 13 is an SEM image of MXene/nickel phosphate electrode material prepared in example 2 of the invention;
FIG. 14 is a TEM image of MXene/nickel phosphate electrode material prepared in example 2 of the present invention;
FIG. 15 is a graph of CV for electrodes made from MXene/nickel phosphate electrode material made in example 2 of the present invention;
FIG. 16 is a graph of the GCD of an electrode made of MXene/nickel phosphate electrode material made in example 2 of the present invention;
FIG. 17 is an SEM image of MXene nanosheets prepared in example 3 of the present invention;
FIG. 18 is an SEM image of MXene/nickel phosphate electrode material prepared in example 3 of the present invention;
FIG. 19 is a TEM image of MXene/nickel phosphate electrode material prepared in example 3 of the present invention;
FIG. 20 is a graph of CV for electrodes made from MXene/nickel phosphate electrode material made in example 3 of the present invention;
fig. 21 is a graph of GCD of an electrode made from MXene/nickel phosphate electrode material made in example 3 of the present invention.
Detailed Description
The invention provides an MXene/nickel phosphate electrode material which comprises an MXene sheet layer and nickel phosphate balls, wherein the nickel phosphate balls are anchored on the surface of the MXene nanosheet layer and are intercalated between the MXene nanosheet layer and the MXene/nickel phosphate ball. The MXene/nickel phosphate electrode material provided by the invention is anchored on the surface of the MXene nanosheet layer, so that the interfacial transfer resistance between composite materials can be reduced, and the conductivity of the composite materials can be improved; the intercalation growth of the nickel phosphate widens the interlayer spacing of the MXene sheets and becomes an interlayer strut of the MXene sheets, the structural stability of the material is enhanced while the ion migration is promoted, and the excellent electrochemical performance of large specific capacitance, high stability and high conductivity is shown.
The MXene/nickel phosphate electrode material provided by the invention comprises an MXene sheet layer and nickel phosphate spheres. In the invention, the mass ratio of the MXene nanosheet layer to the nickel phosphate spheres is preferably (1-3): 19-27, and more preferably (1.5-2): 23-24. In the invention, when the mass ratio of the MXene nanosheet layer to the nickel phosphate ball is in the range, the MXene/nickel phosphate electrode material can show more excellent electrochemical performance.
In the invention, the particle size of the nickel phosphate ball is preferably 15-40 nm, and more preferably 20-30 nm. When the particle size of the nickel phosphate ball is in the range, the specific capacitance of the MXene/nickel phosphate electrode material can be improved.
In the invention, the specific surface area of the MXene/nickel phosphate electrode material is preferably 100-180 m2A concentration of 140 to 160 m/g is more preferable2(ii) in terms of/g. In the invention, when the specific surface area of the nickel phosphate in the MXene/nickel phosphate electrode material is in the range, the large specific capacitance of the MXene/nickel phosphate electrode material is favorably improved.
The invention also provides a preparation method of the MXene/nickel phosphate electrode material, which comprises the following steps:
(1) mixing the MAX phase material with metal fluoride salt and hydrochloric acid to carry out a first etching reaction to obtain an intermediate; mixing the intermediate with hydrofluoric acid to perform a second etching reaction to obtain an MXene nanosheet layer;
(2) mixing nickel nitrate hexahydrate, terephthalic acid, an organic solvent and the MXene nanosheet layer obtained in the step (1), and carrying out solvothermal reaction to obtain MXene-MOF;
(3) mixing the MXene-MOF obtained in the step (2) with a potassium dihydrogen phosphate solution, and carrying out an ion exchange reaction to obtain the MXene/nickel phosphate electrode material.
The MAX phase material, metal fluoride salt and hydrochloric acid are mixed for a first etching reaction to obtain an intermediate. In the invention, the MAX phase material is mixed with metal fluoride salt and hydrochloric acid to carry out the first etching reaction, so that abundant-F, -OH and-O functional groups can be formed on the surface of the MAX phase material.
The MAX phase material is not particularly limited in the present invention, and may be a MAX phase material known to those skilled in the art. In the present invention, the MAX phase material preferably comprises Ti2AlC3、Ti2AlC、V2AlC、Ti3SiC2And Nb2One or more of AlC, more preferably Ti2AlC3Or Ti2And (4) AlC. In the invention, when the MAX phase material is in the range, the MXene nanosheet layer with excellent performance is obtained through the first etching reaction and the second etching reaction.
In the present invention, the metal fluoride salt preferably includes one or more of lithium fluoride, ammonium fluoride, potassium fluoride, and sodium fluoride. The source of the metal fluoride salt is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
In the invention, the hydrochloric acid is preferably concentrated hydrochloric acid, and the concentration of the concentrated hydrochloric acid is preferably 4-7 mol/L, and more preferably 5-6 mol/L. In the invention, the metal fluoride salt and hydrochloric acid are used as an etching agent, and abundant-F, -OH and-O functional groups can be formed on the surface of the MAX phase material sheet layer.
In the present invention, when the concentration of the hydrochloric acid is 4 to 7mol/L, the mass ratio of the MAX phase material, the metal fluoride salt and the hydrochloric acid is preferably (2 to 5): 1 to 2): 30 to 80, and more preferably (3 to 4): 1 to 2): 50 to 60. In the present invention, when the mass ratio of the MAX phase material, the metal fluoride salt, and the hydrochloric acid is in the above range, the first etching reaction is more favorably performed sufficiently.
The operation mode of mixing the MAX phase material with the metal fluoride salt and the hydrochloric acid is not particularly limited, and the components can be uniformly mixed.
In the invention, the temperature of the first etching reaction is preferably 35-50 ℃, and more preferably 40-45 ℃; the time of the first etching reaction is preferably 12-48 h, and more preferably 24-36 h. In the present invention, when the temperature and time of the first etching reaction are within the above ranges, the first etching reaction is more favorably performed sufficiently.
In the present invention, the first etching reaction is preferably performed under stirring. The stirring speed is not particularly limited, and all the components can be uniformly mixed. In the present invention, the stirring enables the first etching reaction to proceed sufficiently, forming abundant-F, -OH and-O functional groups on the surface of the MAX phase material sheet.
After the first etching reaction is completed, the invention preferably washes a product obtained by the first etching reaction to obtain an intermediate. In the present invention, the washing reagent is preferably deionized water. In the invention, the washing can remove soluble impurities in the solid obtained by the first etching reaction.
After the intermediate is obtained, the intermediate is mixed with hydrofluoric acid to carry out a second etching reaction, and the MXene nanosheet layer is obtained. In the invention, mixing the intermediate with hydrofluoric acid for a second etching reaction can remove the Al layer in the MAX phase material and create defects and other growth sites on the MXene nanosheets.
The concentration of the hydrofluoric acid is not particularly limited, and the Al layer in the MAX phase material can be sufficiently removed. In the present invention, the mass concentration of the hydrofluoric acid is preferably 25 to 45%, and more preferably 30 to 40%. In the present invention, when the mass fraction of the hydrofluoric acid is within the above range, it is more favorable to sufficiently remove the Al layer in the MAX phase material.
The ratio of the mass of the intermediate to the volume of the hydrofluoric acid is not particularly limited, and the Al layer in the MAX-phase material can be sufficiently removed by adjusting the removal condition of the Al layer in the MAX-phase material. In the present invention, the ratio of the mass of the intermediate to the volume of hydrofluoric acid is preferably (1-4) g (35-70) mL, and more preferably (2-3) g (40-60) mL. In the present invention, when the ratio of the mass of the intermediate to the volume of hydrofluoric acid is in the above range, the Al layer in the MAX phase material can be sufficiently removed.
The operation mode of mixing the intermediate and hydrofluoric acid is not particularly limited, and the components can be uniformly mixed by adopting a mixing mode well known to a person skilled in the art.
In the invention, the temperature of the second etching reaction is preferably 40-60 ℃, and more preferably 50-60 ℃; the time of the second etching reaction is preferably 24-36 h, and more preferably 30-36 h. In the present invention, when the temperature and time of the second etching reaction are within the above ranges, the second etching reaction can be performed sufficiently.
In the present invention, the second etching reaction is preferably performed under stirring. The stirring speed is not particularly limited, and all the components can be uniformly mixed. In the present invention, the stirring enables the second etching reaction to proceed sufficiently to remove the Al layer in the MAX phase material sufficiently.
After the second etching reaction is finished, the MXene nanosheets are preferably obtained by sequentially washing and drying the products obtained by the second etching reaction. The washing and drying operation method of the present invention is not particularly limited, and a washing and drying operation method known to those skilled in the art may be used. In the present invention, the washing preferably includes centrifugal washing using deionized water and absolute ethanol in this order. In the present invention, the drying is preferably freeze-drying. The temperature of the freeze drying is preferably-25 to-45 ℃, and more preferably-35 to-45 ℃; the freeze drying time is preferably 6-24 hours, and more preferably 12-24 hours. In the present invention, when the temperature and time of the freeze-drying are within the above ranges, damage to the MXene nanosheet due to an excessively high drying temperature can be prevented.
After obtaining the MXene nanosheet layer, mixing nickel nitrate hexahydrate, terephthalic acid, an organic solvent and the MXene nanosheet layer, and carrying out solvothermal reaction to obtain MXene-MOF.
In the invention, the terephthalic acid is used as a regulator to slow down the reaction rate and promote the structure of the MOF to be more complete.
In the invention, the mass ratio of the nickel nitrate hexahydrate, the terephthalic acid and the MXene nano-sheet layer is preferably (0.3-3): 0.1-1): 0.05-0.2, and more preferably (1-2): 0.5-1): 0.1-0.15. In the invention, when the mass ratio of the nickel nitrate hexahydrate to the terephthalic acid to the MXene nanosheet layer is within the range, the solvent thermal reaction is facilitated, the MOF crystal form is more perfect, and the obtained MOF can be uniformly distributed between the surface of the MXene nanosheet layer and the layer.
In the present invention, the organic solvent preferably includes N, N-dimethylformamide or a mixture of N, N-dimethylacetamide and ethylene glycol, and more preferably a mixture of N, N-dimethylformamide and ethylene glycol. In the invention, the volume ratio of the N, N-dimethylformamide to the N, N-dimethylacetamide to the ethylene glycol is preferably (4-1): 2-1, and more preferably 3:1. In the invention, the organic solvent provides reaction conditions for the solvothermal reaction, and when the organic solvent is in the range, the solvothermal reaction can be fully performed, and the MOF can be promoted to be more uniformly distributed between the MXene surface and the sheet layer.
The dosage of the organic solvent is not specially limited, and the dosage can be adjusted according to the quality of nickel nitrate hexahydrate, terephthalic acid and MXene nanosheets. In the invention, the volume ratio of the mass of the nickel nitrate hexahydrate to the volume of the organic solvent is preferably (0.3-3) g (80-150) mL, and more preferably (0.3-3) g (100-120 mL).
The operation mode and the mixing time of mixing the nickel nitrate hexahydrate, the terephthalic acid, the organic solvent and the MXene nanosheet layer are not particularly limited, and the components can be uniformly mixed by adopting a solid-liquid mixing mode well known to a person skilled in the art. In the invention, the nickel nitrate hexahydrate, the terephthalic acid, the organic solvent and the MXene nanosheet layer are preferably prepared by dissolving the nickel nitrate hexahydrate in the terephthalic acid to obtain a transparent solution, dispersing the MXene nanosheet layer in the transparent solution under ultrasonic waves to obtain a mixed solution, and then mixing the mixed solution with the ethylene glycol.
In the invention, the temperature of the solvothermal reaction is preferably 100-150 ℃, and more preferably 120-140 ℃; the solvothermal reaction time is preferably 3-12 h, and more preferably 5-10 h. In the invention, when the temperature and the time of the solvothermal reaction are in the ranges, the MOF crystal form is more complete.
The vessel for the solvothermal reaction is not particularly limited in the present invention, and a reaction vessel known to those skilled in the art may be used.
In the present invention, the solvothermal reaction is preferably carried out under stirring. The stirring speed is not particularly limited, and all the components can be uniformly mixed during the solvothermal reaction. In the invention, the stirring can promote the MOF obtained by the solvothermal reaction to be uniformly distributed between the surface of the MXene nanosheet layer and the lamellar layer.
After the solvothermal reaction is finished, the product obtained by the solvothermal reaction is preferably cooled to room temperature and then is sequentially washed and dried to obtain MXene-MOF. The washing and drying operation method is not particularly limited in the present invention, and the washing and drying operation method known to those skilled in the art may be adopted. In the invention, the washing is preferably suction filtration washing, and the reagent for washing is preferably N, N-dimethylformamide and absolute ethyl alcohol. The washing frequency is not specially limited, and impurities in MXene-MOF can be removed.
In the invention, the drying temperature is preferably 30-60 ℃, and more preferably 40-50 ℃; the drying time is preferably 6-48 h, and more preferably 12-24 h. In the present invention, when the drying temperature and time are within the above ranges, MXene-MOF can be sufficiently dried without breaking the structure of MXene-MOF. The drying apparatus of the present invention is not particularly limited, and a drying apparatus known to those skilled in the art may be used. In the present invention, the drying means is preferably an air-blast drying oven.
After MXene-MOF is obtained, mixing the MXene-MOF with a potassium dihydrogen phosphate solution, and carrying out an ion exchange reaction to obtain the MXene/nickel phosphate electrode material.
In the present invention, the mass ratio of MXene-MOF in the potassium dihydrogen phosphate solution to potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution is preferably (0.7:1) to (1:3), and more preferably (0.8:1) to (1: 4). In the present invention, when the mass ratio of the MXene-MOF in the potassium dihydrogen phosphate solution to the potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution is in the above range, the exchange reaction between the ligand ions and the phosphate ions in the MXene-MOF can be sufficiently performed.
In the present invention, the solvent of the potassium dihydrogen phosphate solution is preferably a mixed solution of ethylene glycol and water. In the invention, when the solvent is of the type mentioned above, the ethylene glycol can increase the viscosity of the system, so that the growth of the nickel phosphate is more uniform and compact. In the present invention, the volume ratio of the ethylene glycol to water is preferably 1 (2 to 4), more preferably 1 (2 to 3). In the present invention, when the volume ratio of ethylene glycol to water is in the above range, the growth of nickel phosphate can be more uniform and compact.
The concentration of the potassium dihydrogen phosphate solution is not particularly limited, and the potassium dihydrogen phosphate solution can be adjusted according to the quality of MXene-MOF. In the invention, the concentration of the potassium dihydrogen phosphate solution is preferably 2.5-4 mg/mL, and more preferably 3.3 mg/mL.
In the invention, the temperature of the ion exchange reaction is preferably 120-170 ℃, and more preferably 130-150 ℃; the time of the ion exchange reaction is preferably 2-9 h, and more preferably 4-8 h. In the present invention, when the temperature and time of the ion exchange reaction are within the above ranges, the exchange reaction between the ligand ions and the phosphate ions in MXene-MOF can be sufficiently performed.
After the ion exchange reaction is completed, the product of the ion exchange reaction is preferably cooled to room temperature, and then washed and dried in sequence to obtain the MXene/nickel phosphate electrode material. The washing and drying operation of the present invention is not particularly limited, and washing and drying known to those skilled in the art may be used. In the present invention, the washing is preferably washing with deionized water and absolute ethanol in this order. The washing frequency is not specially limited, and impurities in the MXene/nickel phosphate electrode material can be fully removed.
In the invention, the drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 25-60 ℃, and more preferably 30-50 ℃; the time for vacuum drying is preferably 6-48 h, and more preferably 12-24 h. In the present invention, when the drying temperature and time are within the above ranges, the MXene/nickel phosphate electrode material can be sufficiently dried without damaging the structure thereof.
The preparation method provided by the invention has the advantages that the MAXe phase material is etched in two steps, so that the surface of the prepared MXene nanosheet layer has defects and is distributed with abundant functional groups such as-F, -OH, -O and the like, the in-situ growth of MOFs on the surface is realized due to the action of the surface defects and the deprotonation process of the ligand promoted by the electronegativity of the surface functional groups, and then the MOFs are converted in situ, so that the nickel phosphate is more stably anchored on the MXene nanosheet layer, the interface transfer resistance of the material is greatly reduced, and the stability of the material is enhanced. In addition, due to the MXene lamellar structure, the layered growth of the nickel phosphate is promoted, the specific surface area of the nickel phosphate is greatly increased, and abundant electrochemical active sites are created; the growth of nickel phosphate between MXene sheet layers widens the interlayer spacing of the MXene sheet layers, the stability of the sheet layer structure is enhanced, and the migration of electrolyte ions is greatly promoted, so that the MXene/nickel phosphate electrode material has higher tolerance to volume effect in the charge and discharge processes, and the specific capacitance of the MXene/nickel phosphate electrode material can be improved.
The invention also provides application of the MXene/nickel phosphate electrode material prepared by the preparation method in the technical scheme in a super capacitor electrode material.
The application method of the MXene/nickel phosphate electrode material in the electrode material of the supercapacitor is not particularly limited, and the application method of the electrode material in the electrode material of the supercapacitor, which is well known to those skilled in the art, can be adopted. In the invention, the application method of the MXene/nickel phosphate electrode material in the supercapacitor electrode material is preferably as follows: an electrode prepared from MXene/nickel phosphate electrode material is used as a working electrode. The method for preparing the electrode from the MXene/nickel phosphate electrode material is not particularly limited, and the method for preparing the electrode from the electrode material, which is well known to a person skilled in the art, can be adopted.
In the present invention, the method for preparing the MXene/nickel phosphate electrode material preferably comprises: mixing the nickel phosphate/MXene material with superconducting carbon black, washing with absolute ethanol, mixing the obtained solid with a polytetrafluoroethylene aqueous solution, drying, uniformly coating on foamed nickel, and tabletting to obtain the electrode.
In the invention, the mass ratio of the nickel phosphate/MXene material to the superconducting carbon black is preferably 8: 1; the mass concentration of the aqueous polytetrafluoroethylene solution is preferably 5%. In the present invention, when the mass ratio of the nickel phosphate/MXene material to the superconducting carbon black and the mass concentration of the polytetrafluoroethylene aqueous solution are in the above ranges, an electrode having excellent performance can be produced.
The MXene/nickel phosphate electrode material provided by the invention is anchored on the surface of the MXene nanosheet layer, so that the interface transfer resistance between the composite materials is reduced, and the conductivity of the composite materials is improved; the intercalation growth of the nickel phosphate widens the interlayer spacing of the MXene sheets and becomes an interlayer strut of the MXene sheets, the structural stability of the material is enhanced while the ion migration is promoted, and the excellent electrochemical performance of large specific capacitance, high stability and high conductivity is shown. Therefore, the MXene/nickel phosphate electrode material provided by the invention can be used as an electrode material of a supercapacitor.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Mixing 3g of Ti2AlC3Mixing with 1.98g LiF and 50mL of concentrated hydrochloric acid with the concentration of 4mol/L, stirring at 40 ℃ for 24 hours, carrying out a first etching reaction, washing with deionized water, and centrifuging to obtain an intermediate; and mixing the intermediate with 50mL of hydrofluoric acid with the mass fraction of 45%, keeping the temperature at 50 ℃ and continuously stirring for 24h, carrying out a second etching reaction, then sequentially washing and centrifuging by using deionized water and absolute ethyl alcohol to obtain a black precipitate, and carrying out freeze drying for 12h to obtain the MXene nanosheet layer. Wherein, MAX phase material (Ti)2AlC3) The mass ratio of metal fluoride salt (LiF) to hydrochloric acid is 3:1.98:50, and Ti2AlC3The mass ratio to LiF was 1: 0.66.
(2) Mixing 0.5g of nickel nitrate hexahydrate, 0.15g of terephthalic acid and 150mL of DMF to obtain a transparent solution, dispersing 0.05g of MXene nanosheets prepared in the step (1) in the transparent solution under ultrasound to obtain a mixed solution, mixing the mixed solution with 50mL of ethylene glycol, reacting at 150 ℃ for 6 hours, carrying out solvothermal reaction, stopping heating, continuously stirring until the temperature of the system is reduced to room temperature, and then carrying out suction filtration and washing on the obtained product for three times by using DMF and absolute ethyl alcohol respectively to obtain MXene-MOF. Wherein the mass ratio of the nickel nitrate hexahydrate to the terephthalic acid to the MXene nanosheet layer is 1:0.3: 0.1.
(3) Mixing 50mg of MXene-MOF obtained in the step (2) with 3.3mg/mL potassium dihydrogen phosphate solution (wherein the volume ratio of deionized water to ethylene glycol is 4:1), carrying out ion exchange reaction in a reaction kettle at 150 ℃ for 3h, naturally cooling to room temperature, washing the obtained product with deionized water and absolute ethyl alcohol sequentially for three times, and carrying out vacuum drying at 60 ℃ for 12h to obtain the MXene/nickel phosphate electrode material. Wherein the mass ratio of MXene-MOF to potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution is 1: 1.
The MXene nanosheet layer prepared in the step (1) of example 1 is tested by a scanning electron microscope, and an SEM image of the MXene nanosheet layer is shown in FIG. 1. As can be seen from FIG. 1, after two-step etching, the obtained MXene nanosheet layer has an obvious lamellar structure.
MXene-MOF prepared in the step (2) of example 1 was tested by scanning electron microscopy, and the SEM image of the MXene-MOF is shown in FIG. 2. As can be seen from FIG. 2, the MOFs globules grow uniformly in situ on the MXene surface.
The MXene/nickel phosphate electrode material prepared in the step (3) of example 1 is tested by a scanning electron microscope, and an SEM image of the MXene/nickel phosphate electrode material is shown in FIG. 3. As can be seen from FIG. 3, the nickel phosphate/MXene material can still maintain the morphological characteristics of the precursor.
An XRD (X-ray diffraction) pattern of the MXene/nickel phosphate electrode material prepared in the embodiment is shown in FIG. 4. As can be seen from fig. 4, the nickel phosphate diffraction peaks and the characteristic peaks associated with MXene indicate successful synthesis of the nickel phosphate/MXene material.
An FTIR chart of the MXene/nickel phosphate electrode material prepared in this example obtained by testing the MXene/nickel phosphate electrode material using a fourier-infrared spectrometer is shown in fig. 5. As can be seen from FIG. 5, 1062cm-1And 890cm-1The characteristic peaks nearby prove PO4 3-Presence of a radical of 572cm-1The nearby characteristic peak is attributed to the stretching vibration of Ni-O bond, and the successful synthesis of the nickel phosphate/MXene material is proved.
An XPS chart of the MXene/nickel phosphate electrode material prepared in this example obtained by testing the MXene/nickel phosphate electrode material with an X-ray photoelectron spectrometer is shown in fig. 6. As can be seen from FIG. 6, the MXene/nickel phosphate electrode material contains elements such as nickel, titanium, carbon, phosphorus, oxygen and the like, and the result is consistent with the XRD and infrared test results, thereby proving that the MXene/nickel phosphate electrode material is successfully synthesized.
The MXene/nickel phosphate electrode material prepared in this example was tested by a projection electron microscope, and a TEM image of the MXene/nickel phosphate electrode material is shown in FIG. 7. As can be seen from FIG. 7, in the MXene/nickel phosphate electrode material, nickel phosphate grows uniformly between MXene layers.
The MXene/nickel phosphate electrode material prepared in this example was tested by a specific surface and pore analyzer, and the adsorption and desorption curve of the MXene/nickel phosphate electrode material is shown in FIG. 8. As can be seen from fig. 8, the MXene/nickel phosphate electrode material possesses a large specific surface area, and the presence of hierarchical pores.
Application example 1
Weighing 16mg of nickel phosphate/MXene material, grinding uniformly, adding 2mg of superconducting carbon black, grinding until the mixture is dispersed uniformly, washing with absolute ethyl alcohol, adding 40 mu L of polytetrafluoroethylene aqueous solution with the mass fraction of 5%, ultrasonically dispersing uniformly, placing in an air-blast drying oven for drying at 60 ℃, and uniformly coating the dried mixed material on 1.5 multiplied by 2cm2And pressing the nickel foam into an electrode.
Test example 1
The electrode prepared in application example 1 was used as a working electrode, a mercury oxide electrode was used as a reference electrode, a platinum mesh was used as a counter electrode, an active material electrode was used as a working electrode, and a 1mol/LKOH solution was used as an electrolyte solution, and the supercapacitor performance of the electrode material prepared in example 1 was characterized and tested by using a test instrument, a Shanghai Chenghua electrochemical workstation.
The CV curve of the electrode prepared from the MXene/nickel phosphate electrode material is shown in fig. 9. As can be seen from fig. 9, the CV curves of the electrodes prepared from MXene/nickel phosphate electrode material have obvious redox peaks at different sweep rates, indicating that the electrodes have excellent electrochemical properties.
The GCD curve of electrodes made from MXene/nickel phosphate electrode material is shown in fig. 10. As can be seen from FIG. 10, the charging and discharging curves of the electrodes prepared from the MXene/nickel phosphate electrode material at different current densities more intuitively show the excellent capacitance properties, and the specific capacitances of the electrodes at the current densities of 0.5, 1, 2, 5, 10, 15 and 20A/g are 639.5, 606.2, 537.6, 444.7, 391.2, 330 and 285C/g respectively, which shows that the MXene/nickel phosphate electrode material prepared by the embodiment of the invention has the excellent capacitance properties.
The cyclic charge and discharge curve of the electrode prepared from the MXene/nickel phosphate electrode material is shown in FIG. 11. As can be seen from FIG. 11, the MXene/nickel phosphate electrode material can maintain 85% of the final capacity after 10000 cycles at a current density of 5A/g, and has excellent cycling stability.
Example 2
(1) 2.5g V2AlC with 1.5g NH4F and 40mL of concentrated hydrochloric acid with the concentration of 4mol/L are mixed, the mixture is stirred for 24 hours at the temperature of 40 ℃ for a first etching reaction, and an intermediate is obtained by washing and centrifuging through deionized water; and mixing the intermediate with 40mL of 35% hydrofluoric acid by mass fraction, keeping the temperature at 40 ℃ and continuously stirring for 32h for carrying out a second etching reaction, then sequentially washing and centrifuging by using deionized water and absolute ethyl alcohol to obtain a black precipitate, and freeze-drying for 15h to obtain the MXene nanosheet layer. Wherein, MAX phase material (V)2AlC), metal fluoride salt (NH)4F) The mass ratio of the hydrochloric acid to the hydrochloric acid is 2.5:1.5:40, V2AlC and NH4The mass ratio of F is 5: 3.
(2) Mixing 0.5g of nickel nitrate hexahydrate, 0.2g of terephthalic acid and 250mL of DMF to obtain a transparent solution, dispersing 0.05g of MXene nanosheets prepared in the step (1) in the transparent solution under ultrasound to obtain a mixed solution, mixing the mixed solution with 60mL of ethylene glycol, reacting at 140 ℃ for 9 hours, carrying out solvothermal reaction, stopping heating, continuously stirring until the temperature of the system is reduced to room temperature, and then carrying out suction filtration and washing on the obtained product for three times by using DMF and absolute ethyl alcohol respectively to obtain MXene-MOF. Wherein the mass ratio of the nickel nitrate hexahydrate to the terephthalic acid to the MXene nanosheet layer is 1:0.4: 0.1.
(3) Mixing 35mg of MXene-MOF obtained in the step (2) with 3.3mg/mL potassium dihydrogen phosphate solution (wherein the volume ratio of deionized water to ethylene glycol is 4:1), carrying out ion exchange reaction in a reaction kettle at 140 ℃ for 3h, naturally cooling to room temperature, washing the obtained product with deionized water and absolute ethyl alcohol sequentially for three times, and carrying out vacuum drying at 60 ℃ for 10h to obtain the MXene/nickel phosphate electrode material. Wherein the mass ratio of MXene-MOF to potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution is 0.7: 1.
An SEM (scanning electron microscope) image of the MXene nanosheet layer prepared in the step (1) of the example 2 is shown in FIG. 12. As can be seen from fig. 12, after the two-step etching, the obtained MXene nanosheet has an obvious lamellar structure.
The MXene/nickel phosphate electrode material prepared in the step (3) of the example 2 is tested by using a scanning electron microscope, and an SEM image of the MXene/nickel phosphate electrode material is shown in FIG. 13. As can be seen from fig. 13, the nickel phosphate/MXene material still can maintain the morphological characteristics of the precursor, and the nickel phosphate is uniformly distributed between the layers and on the surface of the MXene material.
The MXene/nickel phosphate electrode material prepared in this example 2 was tested by a projection electron microscope, and a TEM image of the MXene/nickel phosphate electrode material is shown in FIG. 14. As can be seen from fig. 14, in the MXene/nickel phosphate electrode material, nickel phosphate uniformly grows between layers of MXene.
Application example 2
Weighing 16mg of nickel phosphate/MXene material, grinding uniformly, adding 2mg of superconducting carbon black, grinding until the mixture is dispersed uniformly, washing with absolute ethyl alcohol, adding 40 mu L of polytetrafluoroethylene aqueous solution with the mass fraction of 5%, ultrasonically dispersing uniformly, placing in an air-blast drying oven for drying at 60 ℃, and uniformly coating the dried mixed material on 1.5 multiplied by 2cm2And pressing the nickel foam into an electrode.
Test example 2
The electrode prepared in application example 2 was used as a working electrode, a mercury oxide electrode was used as a reference electrode, a platinum mesh was used as a counter electrode, an active material electrode was used as a working electrode, and a 6mol/LKOH solution was used as an electrolyte solution, and the supercapacitor performance of the electrode material prepared in example 2 was characterized and tested by using a test instrument, a Shanghai Chenghua electrochemical workstation.
The CV curve of the electrode prepared from the MXene/nickel phosphate electrode material is shown in fig. 15. As can be seen from fig. 15, the CV curves of the electrodes prepared from the MXene/nickel phosphate electrode material all have obvious redox peaks at different sweep rates, which indicates that the obvious electrochemical reaction occurs, and reveals that the electrodes have excellent supercapacitor performance.
The GCD curve of electrodes made with MXene/nickel phosphate electrode material is shown in fig. 16. As can be seen from fig. 16, the charge and discharge curves of the electrodes prepared from the MXene/nickel phosphate electrode material at different current densities are more visual to show the excellent capacitance properties, and the specific capacitances at the current densities of 0.5, 1, 2, 5, 10 and 15 are 476, 460, 446, 420.5, 391.2, 374 and 320C/g, respectively, which shows that the MXene/nickel phosphate electrode material prepared by the embodiment of the invention has the excellent capacitance properties.
Example 3
(1) 4g of Ti2Mixing AlC with 2g LiF and 70mL of concentrated hydrochloric acid with the concentration of 5mol/L, stirring at 35 ℃ for 36 hours while stirring for carrying out a first etching reaction, and washing and centrifuging by deionized water to obtain an intermediate; and mixing the intermediate with 70mL of hydrofluoric acid with the mass fraction of 40%, keeping the temperature at 45 ℃ and continuously stirring for 24h, carrying out a second etching reaction, then sequentially washing and centrifuging by using deionized water and absolute ethyl alcohol to obtain a black precipitate, and carrying out freeze drying for 12h to obtain the MXene nanosheet layer. Wherein, MAX phase material (Ti)2AlC3) Metal fluoride (LiF) and hydrochloric acid in a mass ratio of 4:3:70, and Ti2The mass ratio of AlC to LiF is 4: 3.
(2) Mixing 1g of nickel nitrate hexahydrate, 0.45g of terephthalic acid and 150mL of DMF to obtain a transparent solution, dispersing 0.08g of MXene nanosheets prepared in the step (1) in the transparent solution under ultrasonic wave to obtain a mixed solution, mixing the mixed solution with 200mL of ethylene glycol, reacting at 170 ℃ for 12 hours, carrying out solvothermal reaction, stopping heating, continuously stirring until the temperature of the system is reduced to room temperature, and then carrying out suction filtration and washing on the obtained product three times by using DMF and absolute ethyl alcohol respectively to obtain MXene-MOF. Wherein the mass ratio of the nickel nitrate hexahydrate to the terephthalic acid to the MXene nanosheet layer is 1:0.45: 0.08.
(3) Mixing 50mg of MXene-MOF obtained in the step (2) with 2.3mg/mL potassium dihydrogen phosphate solution (wherein the volume ratio of deionized water to ethylene glycol is 4:1), carrying out ion exchange reaction in a reaction kettle at 140 ℃ for 6h, naturally cooling to room temperature, washing the obtained product with deionized water and absolute ethyl alcohol sequentially for three times, and carrying out vacuum drying at 60 ℃ for 12h to obtain the MXene/nickel phosphate electrode material. Wherein the mass ratio of MXene-MOF to potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution is 1: 0.7.
An SEM (scanning electron microscope) image of the MXene nanosheet layer prepared in the step (1) of the example 3 is shown in FIG. 17. As can be seen from FIG. 17, after the two-step etching, the obtained MXene nanosheet layer has an obvious lamellar structure.
The MXene/nickel phosphate electrode material prepared in the step (3) of example 3 is tested by a scanning electron microscope, and an SEM image of the MXene/nickel phosphate electrode material is shown in FIG. 18. As can be seen from FIG. 18, the nickel phosphate/MXene material still can maintain the morphological characteristics of the precursor.
The MXene/nickel phosphate electrode material prepared in this example was tested by a projection electron microscope, and a TEM image of the MXene/nickel phosphate electrode material is shown in FIG. 19. As can be seen from fig. 19, in the MXene/nickel phosphate electrode material, nickel phosphate uniformly grows between layers of MXene.
Application example 3
Weighing 16mg of nickel phosphate/MXene material, grinding uniformly, adding 2mg of superconducting carbon black, grinding until the mixture is dispersed uniformly, washing with absolute ethyl alcohol, adding 40 mu L of polytetrafluoroethylene aqueous solution with the mass fraction of 5%, ultrasonically dispersing uniformly, placing in an air-blast drying oven for drying at 60 ℃, and uniformly coating the dried mixed material on 1.5 multiplied by 2cm2And pressing the nickel foam into an electrode.
Test example 3
The electrode prepared in application example 3 was used as a working electrode, a mercury oxide electrode was used as a reference electrode, a platinum mesh was used as a counter electrode, an active material electrode was used as a working electrode, and a 6mol/LKOH solution was used as an electrolyte solution, and the supercapacitor performance of the electrode material prepared in example 3 was characterized and tested using a test instrument, a chenhua electrochemical workstation, in the test apparatus.
The CV curve of the electrode prepared from the MXene/nickel phosphate electrode material is shown in fig. 20. As can be seen from fig. 20, the CV curves of the electrodes prepared from the MXene/nickel phosphate electrode material have obvious redox peaks at different sweep rates, indicating that the electrodes have excellent electrochemical properties.
The GCD curve of electrodes made from MXene/nickel phosphate electrode material is shown in fig. 21. As can be seen from fig. 21, the charging and discharging curves of the electrodes prepared from the MXene/nickel phosphate electrode material at different current densities are more visual to show the excellent capacitance properties, and the specific capacitances of the electrodes at current densities of 0.5, 1, 2, 5, 10, 15 and 20A/g are respectively 801.2, 750.2, 611.3, 480.5, 450, 380 and 350C/g, which indicates that the MXene/nickel phosphate electrode material prepared by the embodiment of the invention has the excellent capacitance properties.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. An MXene/nickel phosphate electrode material comprises an MXene sheet layer and nickel phosphate spheres, wherein the nickel phosphate spheres are anchored on the surface of the MXene nanosheet layer and are intercalated between the MXene nanosheet layers;
the preparation method of the MXene/nickel phosphate electrode material comprises the following steps:
(1) mixing the MAX phase material with metal fluoride salt and hydrochloric acid to carry out a first etching reaction to obtain an intermediate; mixing the intermediate with hydrofluoric acid to perform a second etching reaction to obtain an MXene nanosheet layer;
(2) mixing nickel nitrate hexahydrate, terephthalic acid, an organic solvent and the MXene nanosheet layer obtained in the step (1), and carrying out solvothermal reaction to obtain MXene-MOF;
(3) mixing the MXene-MOF obtained in the step (2) with a potassium dihydrogen phosphate solution, and carrying out an ion exchange reaction to obtain the MXene/nickel phosphate electrode material.
2. The MXene/nickel phosphate electrode material of claim 1, wherein the specific surface area of the MXene/nickel phosphate electrode material is 100-180 m2/g。
3. The method for preparing MXene/nickel phosphate electrode material of claim 1 or 2, comprising the steps of:
(1) mixing the MAX phase material with metal fluoride salt and hydrochloric acid to carry out a first etching reaction to obtain an intermediate; mixing the intermediate with hydrofluoric acid to perform a second etching reaction to obtain an MXene nanosheet layer;
(2) mixing nickel nitrate hexahydrate, terephthalic acid, an organic solvent and the MXene nanosheet layer obtained in the step (1), and carrying out solvothermal reaction to obtain MXene-MOF;
(3) mixing the MXene-MOF obtained in the step (2) with a potassium dihydrogen phosphate solution, and carrying out an ion exchange reaction to obtain the MXene/nickel phosphate electrode material.
4. The method according to claim 3, wherein the mass ratio of the nickel nitrate hexahydrate, the terephthalic acid and the MXene nanosheets in the step (2) is (0.3-3): (0.1-1): (0.05-0.2).
5. The method according to claim 3, wherein the organic solvent in the step (2) comprises one or more of N, N-dimethylformamide, N-dimethylacetamide and ethylene glycol.
6. The preparation method according to claim 3, wherein the temperature of the solvothermal reaction in the step (2) is 100 to 150 ℃, and the time of the solvothermal reaction is 3 to 12 hours.
7. The method according to claim 3, wherein the mass ratio of MXene-MOF to potassium dihydrogen phosphate in the potassium dihydrogen phosphate solution in step (3) is (0.7:1) - (1: 3).
8. The method according to claim 3, wherein the solvent of the potassium dihydrogen phosphate solution in step (3) is a mixed solution of ethylene glycol and water.
9. The method according to claim 3, wherein the temperature of the ion exchange reaction in step (3) is 120 to 170 ℃ and the time of the ion exchange reaction is 2 to 9 hours.
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