MOF-derived high-porosity carbon aerogel and use thereof in supercapacitator

Abstract

The present invention relates to the technical field of supercapacitors, and in particular, relates to an MOF-derived high-porosity carbon aerogel and the use thereof in a supercapacitor. The MOF-deri

Description

A MOF-derived highly porous carbon aerogel and its application in supercapacitors Technical Field

[0001] The present invention relates to the technical field of supercapacitors, and in particular to a MOF-derived high-porous carbon aerogel and application thereof in supercapacitors. Background Art

[0002] Due to severe climate change caused by the burning of fossil fuels, the demand for clean energy sources such as solar, tidal, and wind power is increasing. However, these clean energy sources are subject to significant environmental constraints, leading to widespread attention from scientists as a new energy storage system: supercapacitors. Supercapacitors, also known as electrochemical capacitors, are one of the most promising energy storage devices. Compared with traditional capacitors and batteries, supercapacitors offer many outstanding advantages, including long cycle life, high power and energy density, ease of maintenance, compact size, high capacity, environmental friendliness, a wide operating temperature range, high reliability at high temperatures, and high safety. Their underlying mechanism is a reversible process occurring at the electrode-electrolyte interface, which enables a long life cycle, high power density, and rapid charge and discharge rates. Currently, supercapacitors are widely used in consumer electronics, memory backup systems, and industrial power supplies and energy management. However, commercially available carbon-based supercapacitors suffer from low energy density, which significantly limits their use in practical applications.

[0003] Metal-organic frameworks (MOFs) are a new class of materials that use inorganic metal ions or ion clusters as the core and organic compounds as ligands to form periodic multidimensional nanoporous materials. Compared with traditional materials, MOFs can provide abundant and evenly distributed active centers, and their pore structure is conducive to the rapid diffusion of electrolyte ions. Therefore, MOFs are considered to be ideal supercapacitor materials. However, there is a problem with using MOFs as anode electrode materials: after hundreds of charge and discharge cycles, the pore structure of MOFs will irreversibly collapse. This leads to a sharp decrease in the specific surface area of ​​the electrode, resulting in a decrease in the diffusion site of electrolyte ions and conductivity. This poses a huge challenge to the study of the conductive process of MOFs supercapacitors.

[0004] Summary of the Invention

[0005] Based on the above content, the present invention provides a MOF-derived highly porous carbon aerogel and its application in supercapacitors. The MOF-ZX-5-derived highly porous carbon aerogel of the present invention has high specific capacitance and cycle stability as a supercapacitor material.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a MOF-ZX-5 material, wherein the MOF-ZX-5 material is [Zn(tppa)2Cl2]; the [Zn(tppa)2Cl2] is a single crystal or a powder crystal; the crystal data of the single crystal is: monoclinic system P2 1 / c , the asymmetric unit includes a Zn II ion, two ligand tppa molecules and two chloride ions; the [Zn(tppa)2Cl2] is an octahedral coordination configuration.

[0008] The second technical solution of the present invention is a method for preparing the above-mentioned MOF material, which is method one or method two;

[0009] The method 1 comprises the following steps:

[0010] The ligand is dissolved in a solvent, and then the mixed solution is added and mixed evenly, and then an ethanol solution of ZnCl2 is added, and the mixture is sealed and allowed to stand to obtain a [Zn(tppa)2Cl2] single crystal; the ligand is tris(4-(pyridin-4-yl)phenyl)amine;

[0011] The second method comprises the following steps:

[0012] The ligand is dissolved in a solvent to obtain a ligand solution; the ligand solution is added dropwise to an ethanol solution of ZnCl2, stirred and allowed to stand, and then filtered to obtain a precipitate; the precipitate is dried to obtain the [Zn(tppa)2Cl2] powder crystal; the ligand is tris(4-(pyridin-4-yl)phenyl)amine.

[0013] Furthermore, in method 1, the solvent is chloroform (chloroform can dissolve the ligand tppa), and the molar volume ratio of the ligand to the solvent is 0.01 mmol: 1 mL; the mixed solution is a mixture of chloroform and ethanol in a volume ratio of 1: 1 (the mixture of chloroform and ethanol has the characteristic of low toxicity); the volume ratio of the solvent to the mixed solution is 3: 4 (the product crystal form is best at this ratio); the molar volume ratio of ZnCl2 to ethanol in the ZnCl2 ethanol solution is 0.01 mmol: 3 mL; the volume ratio of the solvent to the ZnCl2 ethanol solution is 1: 1;

[0014] In method 2, the solvent is chloroform; the molar volume ratio of the ligand to the solvent is 0.1-0.2 mmol:15 mL; the molar volume ratio of ZnCl2 to ethanol in the ZnCl2 ethanol solution is 0.01 mmol:3 mL; the volume ratio of the ligand solution to the ZnCl2 ethanol solution is 1:1; the stirring time is 6-10 h; the standing time is 4-12 h; and the drying temperature is 50-100°C.

[0015] In method 1, the sealed and static time is 20 days, the purpose of which is to cultivate a white block single crystal structure suitable for X-ray structural analysis.

[0016] In method 2, the purpose of stirring for 6-10 hours and standing for 4-12 hours is to synthesize powder crystals to meet the requirements of rapid industrialization. This synthesis cannot be used for structural analysis.

[0017] The third technical solution of the present invention is a MOFs-derived high-porous carbon aerogel (MOF-ZX-5-derived high-porous carbon aerogel), which is obtained by calcining and pyrolyzing the above-mentioned MOF-ZX-5 material.

[0018] A fourth technical solution of the present invention is a method for preparing the above-mentioned MOFs-derived highly porous carbon aerogel, which comprises calcining and pyrolyzing the MOF-ZX-5 material to obtain the MOFs-derived highly porous carbon aerogel.

[0019] Furthermore, the calcination and pyrolysis are specifically carried out under an inert atmosphere, heating the material to 700-1000° C. at a rate of 3-5° C. / min and maintaining the temperature for 2-4 hours.

[0020] The fifth technical solution of the present invention is the application of the above-mentioned MOFs-derived highly porous carbon aerogel in supercapacitors.

[0021] The sixth technical solution of the present invention is an electrode material for a supercapacitor, comprising the above-mentioned MOFs-derived highly porous carbon aerogel.

[0022] The seventh technical solution of the present invention is a supercapacitor, wherein the electrode material of the supercapacitor includes the highly porous carbon aerogel derived from the above-mentioned MOF-ZX-5.

[0023] The present invention discloses the following technical effects:

[0024] The gel portion of MOF-based aerogels can support the MOF structure to a certain extent, improving the stability of MOFs during cycling. This invention uses the novel MOF-ZX-5 ([Zn(tppa)2Cl2]) as a precursor to design and synthesize a novel carbon aerogel material (MOF-derived highly porous carbon aerogel) as an electrode material for supercapacitors. The MOF-ZX-5-derived highly porous carbon aerogel has high porosity, a large specific surface area, and excellent capacitance properties. When used as a supercapacitor electrode material, it exhibits high specific capacitance, power density, and energy density, as well as fast charge and discharge rates and good cycling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 shows the Zn content in MOF-ZX-5 of the present invention. II Ion coordination configuration diagram.

[0027] FIG2 is an XRD spectrum of the carbon aerogel prepared in Example 2.

[0028] FIG3 is a TEM image of the carbon aerogel prepared in Example 2.

[0029] FIG4 is a Raman spectrum of the carbon aerogel prepared in Example 2.

[0030] Figure 5 shows the CV curves at different scan rates.

[0031] Figure 6 shows the GCD curves at different current densities in the three-electrode system.

[0032] FIG7 is a diagram of the "diamond" (4, 4) network structure of MOF-ZX-5 of the present invention. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0035] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0036] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0038] Unless otherwise specified, the "room temperature" in the present invention refers to 15-30°C.

[0039] Unless otherwise specified, the chemicals and reagents used in the examples of the present invention can be obtained through commercial channels.

[0040] The chemicals and reagents used in the examples of the present invention were all commercially available analytical grade.

[0041] The electrochemical performance testing method in the embodiment of the present invention is as follows:

[0042] The electrochemical properties of the material sample (carbon aerogel) were tested using a Shanghai Chenhua electrochemical workstation with a three-electrode system at room temperature.

[0043] Preparation of the working electrode: The prepared carbon aerogel material, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1, placed in an agate mortar and ground with a few drops of ethanol until a homogeneous black slurry was obtained, in which the carbon material was the active substance, acetylene black was the conductive agent, and polyvinylidene fluoride was the binder. Subsequently, the mixed black slurry was transferred to a pre-cleaned area of ​​1 cm 2 , on a 2mm thick nickel foam. It was then placed in a 100°C oven and dried for 12 hours. Finally, the dried nickel foam was pressed under a certain high pressure (10MPa) to form a supercapacitor electrode.

[0044] All electrochemical performance tests were performed using a three-electrode system, with the prepared electrode as the working electrode, a platinum wire electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode. A 6 mol / L aqueous KOH solution was used as the electrolyte. Cyclic voltammetry (CV) measurements were performed over the potential range (-1 to 0 V) ​​at scan rates of 5, 10, 20, 50, and 100 mV s. -1 The test results in a similar-shaped curve of current versus potential.

[0045] The constant current charge-discharge test (GCD) was carried out at different current densities of 0.5, 1.0, 2.0, 5.0 and 10 A g according to the mass of the active material on the working electrode in the corresponding potential range (-1 to 0 V) ​​in the CV test. -1 The constant current charge and discharge curve test was carried out. -1 The cycle life of the carbon material was tested by constant current charge and discharge.

[0046] Example 1

[0047] Step 1, synthesis of [Zn(tppa)2Cl2], i.e. MOF-ZX-5

[0048] Dissolve 0.4 mmol of tppa in chloroform (60 mL) to obtain a tppa chloroform solution. Dissolve 0.2 mmol of ZnCl2 in ethanol (60 mL) to obtain a ZnCl2 ethanol solution. Pour the ZnCl2 ethanol solution into a conical flask, and then slowly add the tppa chloroform solution dropwise to the ZnCl2 ethanol solution using a constant pressure dropping funnel. Stir at room temperature for 6 hours. After 12 hours of filtration, collect the white precipitate and wash it three times with 8 mL of ethanol. Finally, dry the white powder at 50°C to obtain a white powdery MOF-ZX-5 crystal sample with a yield of 65%.

[0049] Step 2, preparation of MOF-ZX-5 derived highly porous carbon aerogel (abbreviated as: carbon aerogel)

[0050] The MOF-ZX-5 prepared in step 1 was placed in a tubular furnace, heated to 800°C at a rate of 5°C / min under a nitrogen atmosphere, kept constant for 3 hours, and then naturally cooled to room temperature to obtain a carbon aerogel product.

[0051] The specific surface area of ​​the carbon aerogel prepared in this example is 996 m 2 g -1 , pore size 2.17nm, which is used as the electrode material of supercapacitor at a current density of 0.5A g -1 The specific capacitance reaches 136F g -1 After 2000 cycles, the specific capacitance is still 133F g -1 .

[0052] Example 2

[0053] Step 1, synthesis of [Zn(tppa)2Cl2], i.e. MOF-ZX-5

[0054] Dissolve 0.6 mmol of tppa in chloroform (60 mL) to obtain a chloroform solution of tppa. Dissolve 0.2 mmol of ZnCl2 in ethanol (60 mL) to obtain a ZnCl2 ethanol solution. Pour the ZnCl2 ethanol solution into a conical flask, and slowly add the chloroform solution of tppa to the ethanol solution using a constant pressure dropping funnel. Stir at room temperature for 8 hours, let it stand for 10 hours, then filter and collect the white precipitate. Wash it three times with 10 mL of ethanol. Finally, dry the white powder at 80°C to obtain a white powdery MOF-ZX-5 crystal sample with a yield of 60%.

[0055] Step 2, preparation of MOF-ZX-5 derived highly porous carbon aerogel (abbreviated as: carbon aerogel)

[0056] The MOF-ZX-5 prepared in step 1 was placed in a tubular furnace, heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere, kept constant for 4 hours, and then naturally cooled to room temperature to obtain a carbon aerogel product.

[0057] The specific surface area of ​​the carbon aerogel prepared in this example is 1267 m 2 g -1 , pore size 2.51nm, which is used as the electrode material of supercapacitor at a current density of 0.5A g -1 The specific capacitance reaches 138F g -1 After 2000 cycles, the specific capacitance is still 135F g -1 .

[0058] Figure 2 is the XRD spectrum of the carbon aerogel prepared in Example 2. From Figure 2, it can be observed that the carbon aerogel has two obvious weak broad peaks at around 25° and 44°, corresponding to the (002) and (101) crystal planes of carbon, respectively, indicating that the degree of graphitization of the carbon aerogel is low.

[0059] Figure 3 is a TEM image of the carbon aerogel prepared in Example 2. Figure 2 shows the morphology and pore structure of the carbon aerogel. As can be seen from Figure 3, the carbon aerogel has a thin layer structure that is smooth and flat, and appears translucent and silky. A large number of disordered pore structures exist in the carbon aerogel.

[0060] Figure 4 is a Raman spectrum of the carbon aerogel prepared in Example 2. The graphitization degree of the carbon aerogel material was analyzed by Raman spectroscopy. As shown in Figure 4, 1360 cm -1 The D peak at 1580 cm is related to the disordered carbon structure. The larger the disorder defect, the stronger its intensity. -1 The G peak at is due to the vibration of graphitized carbon atoms. Usually, the relative ratio of the integrated area of ​​the D peak and the G peak (I D / I G ) is used to measure the degree of graphitization of carbon materials. After calculation, the carbon aerogel prepared in Example 2 has an average graphitization degree of 1. D / I G The value is 4.01, which indicates that the carbon aerogel prepared under the conditions of the method of the present invention will destroy the ordered structure of the carbon material, causing random distribution of carbon atoms and minimizing the degree of graphitization, thereby obtaining the most fluffy product.

[0061] Figure 5 shows the CV curves at different scan rates. Cyclic voltammetry (CV) tests were performed in the corresponding potential range (-1 to 0 V) ​​at different scan rates of 5, 10, 20, 50, and 100 mV s -1 The test results show a similar shape to the current versus potential curve. The CV curve shows a large rectangular area, which increases with the increase of the scan rate. As the scan rate and current density increase, the curve deformation becomes more and more serious, which is caused by the limited diffusion of electrolyte ions. For the CV curve, the specific capacitance can be calculated according to formula (1). C = ∫IdV / 2vΔVm (1)

[0062] Where C(F g -1 ), I(A), V(V), v(mV s -1 ) and m(g) represent the specific capacitance, instantaneous current, voltage range, scan rate and mass of active material, respectively. -1 Increase to 100mV s -1 The specific capacitance of the electrode is increased from 145F g -1 Down to 94F g -1This is because the electrolyte does not have enough time to reach the micropore surface at high scan rates, resulting in less stored electrostatic charge.

[0063] Figure 6 shows the GCD curves at different current densities in the three-electrode system. -1 At different current densities, the present invention tested the constant current charge and discharge curves of the working electrode (Figure 6). The specific capacitance can be obtained from the discharge curve using formula (2). C = IΔt / ΔVm (2)

[0064] Where t(s) is the discharge time, and the other variables are consistent with formula (1). According to the charge and discharge test, the electrode has a current density of 0.5, 1, 2, 5 and 10A g -1 The specific capacitances are 130, 120, 116, 106 and 100 F g -1 It is worth noting that the capacitance value decreases slowly with the gradual increase of current density. This is because the specific surface area where ions can reach the contact decreases when the current density increases.

[0065] Example 3

[0066] Step 1, synthesis of [Zn(tppa)2Cl2], i.e. MOF-ZX-5

[0067] Dissolve 0.8mmol tppa in chloroform (60mL) to obtain tppa chloroform solution; dissolve 0.2mmol ZnCl2 in ethanol (60mL) to obtain ZnCl2 ethanol solution; pour the ZnCl2 ethanol solution into a conical flask, and then slowly add the tppa chloroform solution to the ethanol solution through a constant pressure dropping funnel. Stir at room temperature for 10 hours, let it stand for 8 hours, filter and collect the white precipitate, and then wash it with 10mL ethanol 3 times. Finally, dry the white powder at 100°C to obtain a white powdery MOF-ZX-5 crystal sample. Yield: 62%

[0068] Step 2, preparation of MOF-ZX-5 derived highly porous carbon aerogel (abbreviated as: carbon aerogel)

[0069] The MOF-ZX-5 prepared in step 1 was placed in a tubular furnace, heated to 1000°C at a rate of 3°C / min under a nitrogen atmosphere, kept constant for 2 hours, and then naturally cooled to room temperature to obtain a carbon aerogel product.

[0070] The specific surface area of ​​the carbon aerogel prepared in this example is 1293 m 2 g -1 , pore size 4.24nm, which is used as the electrode material of supercapacitor at a current density of 0.5A g -1 The specific capacitance reaches 142F g -1After 2000 cycles, the specific capacitance is still 137F g -1 .

[0071] Figure 1 shows the Zn content in MOF-ZX-5 of the present invention. II Ion coordination configuration diagram. Figure 1 shows the analysis of the single crystal structure of MOF-ZX-5. The space group of MOF-ZX-5 belongs to the monoclinic system P2 1 / c , the asymmetric unit includes a Zn II ions, two ligand tppa molecules and two chloride ions. As shown in Figure 1, each Zn II The ion is coordinated with four nitrogen atoms from different TPPA molecules and two chloride ions to form an octahedral coordination configuration. The Zn-N coordination bond length in the equatorial plane is and the axial Zn-Cl coordination bond length reaches Therefore, Zn II There is an obvious Jahn-Teller effect in ions.

[0072] Figure 7 is a diagram of the "diamond" (4,4) network structure of MOF-ZX-5 of the present invention. Although the TPPA molecule has three nitrogen atoms, only two nitrogen atoms participate in the coordination during the assembly process, that is, each TPPA ligand bridges two Zn II ions, resulting in a two-dimensional "diamond" (4, 4) network with a lattice size of (Figure 7), the pore size reaches the nanometer level.

[0073] Carbon-based electrode materials used in supercapacitors offer excellent reversibility, rapid charging capabilities, long cycle life, and environmental friendliness. However, their relatively low specific capacitance leads to low energy density, restricting their comprehensive applications. MOFs, as a classic porous compound, possess favorable structural characteristics such as long-range ordered structure and large specific surface area. This paper synthesizes a novel carbon aerogel electrode material using a novel macroporous MOF-ZX-5 as a precursor, improving the specific capacitance and energy density of supercapacitor electrode materials.

[0074] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. AMOF-ZX-5 material, wherein the MOF-ZX-5 material is [Zn(tppa)2C12]; the [Zn(tppa)2C12] is single crystal or powder crystal; crystal data of the single crystal are: monoclinic system P2i c, and an asymmetric unit comprises one Zn" ion, two ligand tppa molecules, and two chloride ions; and the [Zn(tppa)2Cl2] is an octahedral coordination configuration.

2. A preparation method of the MOF-ZX-5 material according to claim 1, being a first method or a second method;wherein the first method comprises following steps:dissolving a ligand in a solvent, then adding a mixed solution and mixing evenly, and then adding an ethanol solution of ZnCl2, and sealing and standing to obtain the [Zn(tppa)2Cl2], wherein the ligand is tris(4-(pyridin-4-yl)phenyl)amine;wherein the second method comprises following steps:dissolving a ligand in a solvent to obtain a ligand solution; adding the ligand solution dropwise into an ethanol solution of ZnCL, stirring, standing, performing suction filtration to obtain a precipitate, and drying the precipitate to obtain the [Zn(tppa)2C12]; wherein the ligand is tri s(4-(pyri din-4-yl)phenyl )ami ne.

3. The preparation method according to claim 2, wherein in the first method, the solvent is chloroform, and a molar volume ratio of the ligand to the solvent is 0.01 mmol: 1 mL; the mixed solution is a mixture of chloroform and ethanol with a volume ratio of 1:1; a volume ratio of the solvent to the mixed solution is 3:4; a molar volume ratio of ZnCl2 to ethanol in the ethanol solution of ZnCh is 0.01 mmol:3 mL; and a volume ratio of the solvent to the ethanol solution of ZnCh is 1:1; andin the second method, the solvent is chloroform; a molar volume ratio of the ligand to the solvent is 0.1-0.2 mmol: 15 mL; a molar volume ratio of ZnCh to ethanol in the ethanol solution of ZnCh is 0.01 mmol:3 mL; a volume ratio of the ligand solution to the ethanol solution of ZnCh is 1:1; a stirring duration is 6-10 h; a standing duration is 4-12 h; and a drying temperature is 50- 100°C.

4. An MOFs-derived high-porosity carbon aerogel, being obtained by performing calcination pyrolysis to the MOF-ZX-5 material according to claim 1.

5. A preparation method of the MOFs-derived high-porosity carbon aerogel according to claim 4, wherein the MOF-ZX-5 material is subjected to the calcination pyrolysis to obtain the MOFs-derived high-porosity carbon aerogel.

6. The preparation method according to claim 5, wherein the calcination pyrolysis specifically comprises heating to 700-1000°C at a rate of 3-5°C / min under an inert atmosphere, and keeping a temperature for 2-4 h.

7. An application of the MOFs-derived high-porosity carbon aerogel in supercapacitors according to claim 4.

8. An electrode material of a supercapacitor, comprising the MOFs-derived high-porosity carbon aeroge according to claim 4.

9. A supercapacitor, wherein an electrode material of the supercapacitor comprises the MOFs-derived high-porosity carbon aerogel according to claim 4.

Images