MOF/MXene/CF composite nanosheet and synthesis method thereof
阅读说明：本技术 一种MOF/MXene/CF复合纳米片及其合成方法 (MOF/MXene/CF composite nanosheet and synthesis method thereof ) 是由 郭玉香 张瑞楠 郭菁 姚焯 徐东辉 张德航 魏原驰 于 2020-06-15 设计创作，主要内容包括：本发明涉及一种MOF/MXene/CF复合纳米片,MOF/MXene复合纳米材料通过液相沉积法在碳纤维布表面静电自组装得到自支撑结构的复合纳米片。MAX材料处理除掉材料的金属原子,得到MXene材料,MOF材料分解得到金属原子和有机配体,MOF中的金属原子进入MXene材料,而有机配体随着金属原子也进入MXene材料,MOF/MXene复合结构通过液相沉积法在碳纤维布静电自组装形成MOF/MXene/CF复合纳米片。本发明复合纳米片是二次生成的MOF材料穿插于MAX材料蚀刻后得MXene层状结构内部且附着于层状结构表面；二次生成的MOF材料是原MOF分解后得到的有机配体,通过游离金属原子A和有机配体、游离金属节点和有机配体各自产生络合作用自组装在一起。(The invention relates to an MOF/MXene/CF composite nanosheet, wherein the MOF/MXene composite nanomaterial is a composite nanosheet with a self-supporting structure obtained by electrostatic self-assembly on the surface of carbon fiber cloth through a liquid phase deposition method. And (2) treating the MAX material to remove metal atoms of the material to obtain an MXene material, decomposing the MOF material to obtain metal atoms and organic ligands, wherein the metal atoms in the MOF enter the MXene material, the organic ligands also enter the MXene material along with the metal atoms, and the MOF/MXene composite structure is subjected to electrostatic self-assembly on the carbon fiber cloth by a liquid phase deposition method to form the MOF/MXene/CF composite nanosheet. The composite nano sheet is formed by penetrating a secondarily generated MOF material into a MAX material for etching to obtain an MXene layered structure, wherein the MXene layered structure is attached to the surface of the layered structure; the MOF material generated for the second time is an organic ligand obtained after the original MOF is decomposed, and the free metal atom A and the organic ligand, the free metal node and the organic ligand are respectively subjected to complexation and self-assembly.)
1. An MOF/MXene/CF composite nanosheet is characterized in that the MOF/MXene composite nanomaterial is subjected to electrostatic self-assembly on the surface of carbon fiber cloth by a liquid phase deposition method to obtain the composite nanosheet with a self-supporting structure.
2. A synthesis method of MOF/MXene/CF composite nanosheets is characterized in that the MOF/MXene composite nanomaterial is subjected to electrostatic self-assembly on the surface of carbon fiber cloth by a liquid phase deposition method to obtain the MOF/MXene/CF composite nanosheets with self-supporting structures; the method comprises the following specific steps:
step one, etching an MAX material: ball-milling MAX phase materials in an organic solvent or water, carrying out vacuum drying, and then carrying out ball-milling and sieving to obtain submicron-sized powder; immersing the powder in hydrofluoric acid, magnetically stirring for 10-40 h at room temperature, washing with deionized water to remove redundant acid solution, and drying overnight at room temperature to obtain MXene powder;
step two, decomposing the MOF material: decomposing the MOF material at room temperature for 2-5 h in an argon-filled environment by using a mixed solution of carbonate and bicarbonate, fully washing with deionized water to remove redundant salt solution, and drying at room temperature overnight to obtain decomposed MOF powder;
step three, synthesizing the MOF/MXene nano material: adding MXene powder obtained in the first step, decomposed MOF powder obtained in the second step and an alcohol solution into a reaction kettle for synthesis reaction, wherein the molar ratio of the MXene powder to the decomposed MOF powder is (0.8-1.55): 1; carrying out hydrothermal treatment at 150-165 ℃ for 5-7 hours to obtain an MOF/MXene turbid liquid with charges;
purifying the MOF/MXene suspension to remove unreacted ions and organic matters to obtain an MOF/MXene precipitate;
and fifthly, adding an alcoholic solution into the MOF/MXene precipitate, and performing electrostatic self-assembly on the surface of the carbon fiber cloth subjected to impurity removal by using a liquid phase deposition method to obtain the MOF/MXene/CF composite nanosheet.
3. The method for synthesizing MOF/MXene/CF composite nanosheets of claim 2, wherein in the first step, the MAX material is selected from Mn4AlC3、V4AlC3One of (1); the organic solvent is ethanol solution with the concentration of 50 percent; the magnetic stirring speed is 1200 rmp; the pH value of the deionized water after washing is 6.5-8.5.
4. The synthesis method of MOF/MXene/CF composite nanosheets of claim 2, wherein in step two the MOF material is selected from (C)5H5)Mn(CO)3、(C5H5)V(CO)3One of (1); the mixed solution of carbonate and bicarbonate is NaCO3And NaHCO3Mixed liquor of (1), NaCO3And NaHCO3The molar ratio is (0.3-0.5): (0.8-1.1), the concentration of the mixed liquid is 0.8-1.2 mol/L.
5. The synthesis method of the MOF/MXene/CF composite nanosheet according to claim 2, wherein the alcohol solution in the third step is a 10% ethanol solution, and the pressure in the reaction kettle during the synthesis process is 8 MPa.
6. The synthesis method of MOF/MXene/CF composite nanosheets of claim 2, wherein in step four, impurity removal is performed by a centrifuge at a centrifugation rate of 3000 rmp.
7. The synthesis method of the MOF/MXene/CF composite nanosheet according to claim 2, wherein in step five, the carbon fiber cloth impurity removal method comprises: removing impurities by using nitric acid with the concentration of 60%, and carrying out ultrasonic treatment for 45 minutes at the ultrasonic power of 1000W.
8. The synthesis method of MOF/MXene/CF composite nanosheets of claim 2, wherein the alcohol solution concentration in step five is a 10% ethanol solution.
9. The synthesis method of MOF/MXene/CF composite nanosheets according to claim 2, wherein the liquid phase deposition method operates in step five: and immersing the carbon fiber cloth subjected to impurity removal into an alcoholic solution of the MOF/MXene precipitate for more than 35 minutes, pouring the carbon fiber cloth into a 2-methylimidazole solution along with the solution, standing for 2-3 hours, finally washing with deionized water, and drying to obtain the MOF/MXene composite nanosheet.
10. The MOF/MXene/CF composite nanosheet produced by the synthesis method according to claim 2, being used as a lithium battery anode material.
Technical Field
The invention relates to the technical field of composite materials, in particular to a synthesis method of MOF/MXene/CF composite nanosheets.
Background
Currently, the negative electrode material in lithium ion batteries is mainly carbon, such as graphite, soft and hard carbon, or a novel electrode material, such as a silicon carbon negative electrode or a transition metal oxide. With the exhaustion of petroleum energy and the problem of environmental pollution, the requirement of the market for the battery capacity is gradually improved, and the lithium ion battery with the traditional cathode cannot meet the current situation. Under the circumstances, the compound preparation of the novel material and the application of the novel material in the lithium ion battery become research hotspots.
MXene as a novel material is a two-dimensional material with a structure similar to that of graphene, and the chemical formula is marked as Mn+1XnTxWherein M represents a transition metal such as Ti, V, Zr, Mn, etc., X is a carbon element or a nitrogen element, and T is a surface functional group. The MXene layered structure is obtained by etching away the intermediate layer from a precursor MAX phase (a ternary layered compound, A is a III or IV main group element), but the layers are easy to generate self-stacking, and the wetting of electrolyte and the rapid transmission of lithium ions between layers are hindered in the application of the lithium battery. The MOF material is a porous material with a regular pore channel structure, which is formed by combining metal ions and organic ligands through covalent bonds, coordination bonds, intermolecular forces and the like. The MOF material has a regular and controllable three-dimensional pore channel structure, and is beneficial to lithium ion storage and transmission. The CF (carbon fiber) material has high strength, small density, high durability and stable structure, and is suitable for being used in high-acid, alkali, salt and atmospheric corrosion environments.
At present, the application of composite materials in the field of super capacitors such as lithium batteries is in a high-speed development period, and the electrode is always the key point of research as an important part of energy storage of the capacitor. MXene is a graphene-like two-dimensional material discovered in recent years, and has ultrahigh volume specific capacity, metal-grade conductivity, good hydrophilicity and abundant surface chemistryTherefore, the material has wide application in flexible energy storage electrode materials. In a patent (publication number: 109003836B) published by Hubei college of automotive industry, a preparation method and application of an MXene-based flexible fabric electrode are disclosed. Synthesizing the MXene flexible fabric electrode by an electroplating method: mix TiH2Sintering the powder A1 and the powder C according to a ratio, sieving to obtain MAX phase powder, chemically etching the MAX phase powder to obtain MXene material, and performing low-temperature ultrasonic treatment and centrifugation to obtain Ti3C2MXene colloidal solution, and soaking the cleaned fabric in the diluted MXene solution, and vacuum drying. Ti can be effectively avoided in the process3C2By oxidation to TiO2The method has the advantages of obviously improving the capacitance performance, along with low cost, no toxicity and no pollution, and can be applied to the field of super capacitors. MXene is widely concerned due to its high specific capacity, however, due to its serious layer-by-layer stacking phenomenon, it is not favorable for the rapid diffusion of ions in the vertical direction, affecting the specific capacity under the high current density, and due to the worse oxidation resistance of MXene, it seriously affects the conductivity and the cycling stability, so that it becomes important to improve the layer-by-layer stacking phenomenon of MXene and the oxidation resistance by compounding it with the high specific capacity active material.
Metal Organic Frameworks (MOFs) are crystalline framework materials with intramolecular pores formed by self-assembly of metal ions or clusters with organic ligands under certain conditions through coordination bonds. The material has large specific surface area, adjustable pore size and shape and easy modification, and the proton-conducting and electron-conducting MOF material has potential application value in the fields of fuel cells, electrocatalysis, lithium ion batteries, supercapacitors and the like. Other components are introduced into the MOF structure, so that the structure of the MOF can be finely adjusted, the adsorption performance, the catalytic activity, the conductivity and the like are improved, and even the MOF has properties which are not possessed originally. In a patent published by Nanjing post and telecommunications university (publication number: 106611653A), a "one-step" method of making novel MOF composites is disclosed: etching MAXe material to obtain MXene material and free A ions, adding organic ligand molecules while etching, wherein the organic ligand molecules and the A ions are generated on the surface of the MXene materialThe MOF crystals are reacted to form a MOF/MXene composite material having a layered structure of the MOF and MXene materials stacked on each other. In the patent (publication number: 105047435B) published by Shanghai engineering technology university, a method for synthesizing a manganese metal organic framework electrode material by a hydrothermal method and application thereof are disclosed: will contain Mn2+The soluble salt, the organic acid and the bidentate nitrogen-containing ligand are added into deionized water and are stirred and mixed evenly, the mixture is reacted for 48 to 96 hours in a reaction kettle at the temperature of 120-200 ℃, the manganese metal organic framework electrode material can be prepared through the steps of cooling, filtering, washing, drying and the like after the reaction is finished, the specific capacitance can reach 242F/g, and the manganese metal organic framework electrode material can be applied to the occasions of high-power-density power supplies.
MOF has been widely paid attention to its unique pore structure and characteristics of containing transition metal elements, and has been used to successfully prepare electrodes using MOF as an active material or as an active material carrier, and also to prepare electrodes using MOF as a precursor to form an active material or an active material carrier, but MOF as an electrode has slightly poor conductivity compared to other electrode materials, and cannot exert the maximum storage performance of a capacitor using MOF as an electrode to the maximum extent. Secondly, the preparation process of the MOF is complex, the morphology controllability of the MOF is influenced, the stability between preparation layers is poor, and the wide application of the MOF in electrode materials is limited. Therefore, the method has very important significance in finding a composite material which has a stable structure, a large specific surface area, a wider application range and greatly improved charging and discharging coulombic efficiency and cyclicity.
Disclosure of Invention
The invention aims to solve the technical problem of providing a synthesis method of an MOF/MXene/CF composite nanosheet, and overcoming the defects of small space between the traditional MXene composite material layers, easy interlayer stacking and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
an MOF/MXene/CF composite nano-sheet is prepared by carrying out electrostatic self-assembly on the surface of carbon fiber cloth by using a liquid phase deposition method to obtain the composite nano-sheet with a self-supporting structure.
A synthesis method of MOF/MXene/CF composite nanosheets comprises the following specific steps:
step one, etching an MAX material: ball-milling MAX phase materials in an organic solvent or water, carrying out vacuum drying, and then carrying out ball-milling and sieving to obtain submicron-sized powder; immersing the powder in hydrofluoric acid, magnetically stirring for 10-40 h at room temperature, washing with deionized water to remove redundant acid solution, and drying overnight at room temperature to obtain MXene powder;
step two, decomposing the MOF material: decomposing the MOF material at room temperature for 2-5 h in an argon-filled environment by using a mixed solution of carbonate and bicarbonate, fully washing with deionized water to remove redundant salt solution, and drying at room temperature overnight to obtain decomposed MOF powder;
step three, synthesizing the MOF/MXene nano material: adding MXene powder obtained in the first step, decomposed MOF powder obtained in the second step and an alcohol solution into a reaction kettle for synthesis reaction, wherein the molar ratio of the MXene powder to the decomposed MOF powder is (0.8-1.55): 1; carrying out hydrothermal treatment at 150-165 ℃ for 5-7 hours to obtain an MOF/MXene turbid liquid with charges;
purifying the MOF/MXene suspension to remove unreacted ions and organic matters to obtain an MOF/MXene precipitate;
and fifthly, adding an alcoholic solution into the MOF/MXene precipitate, and performing electrostatic self-assembly on the surface of the carbon fiber cloth subjected to impurity removal by using a liquid phase deposition method to obtain the MOF/MXene/CF composite nanosheet.
The MAX material in the first step is selected from Mn4AlC3、V4AlC3One of (1); the organic solvent is ethanol solution with the concentration of 50 percent; the magnetic stirring speed is 1200 rmp; the pH value of the deionized water after washing is 6.5-8.5.
In the second step, the MOF material is selected from (C)5H5)Mn(CO)3、(C5H5)V(CO)3One of (1); the mixed solution of carbonate and bicarbonate is NaCO3And NaHCO3Mixed liquor of (1), NaCO3And NaHCO3The molar ratio is (0.3-0.5): (0.8-1.1), the concentration of the mixed liquid is (0.8-1.2) mol/L.
The alcoholic solution in the third step is an ethanol solution with the concentration of 10 percent, and the pressure in a reaction kettle in the synthesis process is 8 MPa.
And step four, removing impurities by adopting a centrifugal machine, wherein the centrifugal rate is 3000 rmp.
And fifthly, removing impurities from the carbon fiber cloth: removing impurities by using nitric acid with the concentration of 60%, and carrying out ultrasonic treatment for 45 minutes at the ultrasonic power of 1000W.
In the fifth step, the concentration of the alcoholic solution is 10 percent of the alcoholic solution,
the operation of the liquid phase deposition method in the step five: and immersing the carbon fiber cloth subjected to impurity removal into an alcoholic solution of the MOF/MXene precipitate for more than 35 minutes, pouring the carbon fiber cloth into a 2-methylimidazole solution along with the solution, standing for 2-3 hours, finally washing with deionized water, and drying to obtain the MOF/MXene composite nanosheet.
The MOF/MXene/CF composite nanosheet is used for a lithium battery anode material.
The MAX material is treated in the first step by removing metal atoms of the material to obtain an MXene material, the MOF material is decomposed in the second step to obtain metal atoms and organic ligands, the metal atoms in the MOF material enter the MXene material, and the organic ligands enter the MXene material along with the metal atoms, so that the MOF/MXene composite structure is negatively charged, positive charges exist on the surface of the carbon fiber cloth after impurity removal, and electrostatic adsorption sites are provided for the positive charges of the carbon fiber cloth at the positions where the negative charges exist in the MOF/MXene composite structure. And after fully soaking the carbon fiber cloth and an alcoholic solution of the MOF/MXene composite nano material, carrying out electrostatic self-assembly on the carbon fiber cloth by a liquid phase deposition method to form the MOF/MXene/CF composite nano sheet.
Compared with the prior art, the invention has the beneficial effects that:
the composite nano sheet is formed by penetrating a secondarily generated MOF material into a MAX material for etching to obtain an MXene layered structure, wherein the MXene layered structure is attached to the surface of the layered structure; the MOF material generated for the second time is an organic ligand obtained after the original MOF is decomposed, and the free metal atom A and the organic ligand, the free metal node and the organic ligand are respectively subjected to complexation and self-assembly.
MXene materials and MOF materials are combined to form a nano layered material with a sandwich structure, wherein the MXene materials and the MOF materials are stacked in a staggered mode, and the nano layered material is inserted into soft layers of the MXene materials to play a role like a support column on the basis of exerting excellent performance of high volume specific capacity of the MXene, and the stability and microstructure controllability of the MOF material structure are utilized to form a channel and a space which can provide diffusion and storage for ions to the maximum extent and form a stable layered structure, so that the application range is further expanded, and the charge-discharge coulombic efficiency and the cycle performance of the material are improved.
On the basis of the MOF/MXene composite material, carbon fiber Cloth (CF) is introduced, so that the MOF/MXene composite material is synthesized on the CF in situ to form the MOF/MXene/CF composite nanosheet with a stable structure. And secondly, the CF has conductivity and a large specific surface area, so that the storage capacity of the MOF/MXene/CF composite nanosheets to ion pairs is further increased while the stability of the material is improved.
The novel MOF/MXene/CF composite nanosheet is prepared based on the process of decomposing MAX materials and MOF materials and synthesizing the MOF/MXene/CF composite nanosheets on the CF surface, namely, the MOF composite nanosheets with uniform structures are obtained by utilizing the controllability of MXene structures. As a negative electrode material of the lithium battery, the stability, the stored energy and the utilization efficiency of the device are improved.
Detailed Description
The invention is further illustrated by the following examples:
the following examples describe the invention in detail. These examples are merely illustrative of the best embodiments of the present invention and do not limit the scope of the invention.
A synthesis method of MOF/MXene/CF composite nanosheets is characterized in that the MOF/MXene composite nanomaterial is subjected to electrostatic self-assembly on the surface of carbon fiber cloth by a liquid phase deposition method to obtain the MOF/MXene/CF composite nanosheets with self-supporting structures; the method comprises the following specific steps:
step one, etching an MAX material: grinding the MAX material into a MAX material with a submicron size by using a ball mill, and etching the MAX material with the submicron size to obtain free metal atoms A and MXene layered structures; ball-milling MAX phase materials in an organic solvent or water, carrying out vacuum drying, and then carrying out ball-milling and sieving to obtain submicron-sized powder; immersing the powder in hydrofluoric acid, magnetically stirring for 10-40 h at room temperature, washing with deionized water to remove redundant acid solution, and drying overnight at room temperature to obtain MXene powder;
step two, decomposing the MOF material: decomposing the MOF material into metal nodes and organic ligands using an aqueous solution of carbonates and bicarbonates; decomposing the MOF material at room temperature for 2-5 h in an argon-filled environment by using a mixed solution of carbonate and bicarbonate, fully washing with deionized water to remove redundant salt solution, and drying at room temperature overnight to obtain decomposed MOF powder;
step three, synthesizing the MOF/MXene composite nano material: adding MXene powder obtained in the first step, decomposed MOF powder obtained in the second step and an alcohol solution into a reaction kettle for synthesis reaction, wherein the molar ratio of the MXene powder to the decomposed MOF powder is (0.8-1.55): 1; carrying out hydrothermal treatment at 150-165 ℃ for 5-7 hours to obtain an MOF/MXene turbid liquid with charges;
purifying the MOF/MXene suspension to remove unreacted ions and organic matters to obtain an MOF/MXene precipitate;
and fifthly, adding an alcoholic solution into the MOF/MXene precipitate, and performing electrostatic self-assembly on the surface of the carbon fiber cloth subjected to impurity removal by using a liquid phase deposition method to obtain the MOF/MXene/CF composite nanosheet.