1-nitroanthraquinone covalently modified metal-organic framework composite carbon nanotube self-supporting electrode and preparation method thereof

Abstract

The application discloses a kind of self-supporting electrode based on 1-nitroanthraquinone covalent modification metal organic framework composite carbon nanotube and preparation method thereof.The method first uses one-pot hydrothermal method to prepare CNT@UiO-66-NO2, then solvent thermal method is carried out to the surface of metal organic framework, and 1-nitroanthraquinone is chemically bonded to the surface of metal organic framework by converting nitro functional group into azo bond, to prepare CNT@UiO-66-AQ self-supporting electrode.The preparation method of the application is simple, without post-treatment, the specific capacitance of the prepared electrode is increased by 4 times compared with before modification, 1Ag ‑1 When area specific capacitance reaches 302 mFcm ‑2 , current density is increased by 20 times, specific capacitance is retained up to 71%, specific capacitance retention rate is 100% after 5K cycles, with excellent cycle stability, suitable for supercapacitor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of self-supporting electrodes, and relates to a self-supporting electrode based on 1-nitroanthraquinone covalent modification of metal organic framework composite carbon nanotubes and a preparation method thereof. BACKGROUND

[0002] As an effective and reliable energy storage technology, supercapacitors have attracted much attention due to their fast charge-discharge speed, high power density, long cycle life, safety and environmental protection, and have been widely used in electronic communication, electric vehicles and aerospace systems. The evaluation standards of the electrochemical performance of supercapacitors mainly include energy density, power density and cycle life. As one of the main components of supercapacitors, the performance of electrode materials is closely related to the electrochemical performance of supercapacitors.

[0003] Metal organic frameworks (MOFs) are a kind of porous materials composed of metal nodes and organic ligands, and their structures can be adjusted by changing the properties of metal ions and linkers or post-synthesis modification. Due to their excellent specific surface area, high porosity, adjustable pore size and functionalized porous surface, metal organic frameworks have been synthesized for the study of energy storage, separation, catalysis, sensing, detection and other fields. However, low electrical conductivity, poor mechanical and chemical stability limit their further application in electrochemical energy storage. Carbon nanotubes (CNT) have large specific surface area, high electrical conductivity and excellent cycle life, and their surface can be easily modified by carboxyl groups, etc., and are often used as substrate materials in electrode materials.

[0004] Post-synthesis modification (PSM) of MOFs has been widely used in gas adsorption and separation, catalysis and electrochemical energy storage. Peng et al. reported a post-synthesis modification of MOF@COF-LZU1 using aza-Diels-Alder cycloaddition reaction, and the generated aza-MOFs@COFs hybrid porous material with extended p-delocalization was used for high-performance supercapacitors, which exhibited a specific capacitance of 20.35 mF cm -2 at a current density of 0.2 A cm -2 and a retention rate of 89.3% after 2000 cycles (H. Peng, et al., Synthesis of robust MOFs@COFs Porous Hybrid Materials via anaza-Diels-Alder reaction: Towards high-performance supercapacitor materials. Angewandte Chemie International Edition, 2020, 59, 19602-19609).

[0005] Organic quinone has a very high theoretical capacity, and the specific capacity of the material can be greatly improved by compounding with other materials. However, the physically deposited quinone molecules tend to slowly dissolve into the aqueous electrolyte during long-term use, causing rapid capacity decay. When Sheng et al. electrochemically polymerized 3,4-ethylenedioxythiophene (PEDOT), they added anthraquinone-2-sulfonic acid sodium (AQS) to the electrolyte as a redox dopant. Compared with the original PEDOT, its specific capacity has been greatly improved, but due to the dissolution and diffusion of small molecules during the cycle, its capacity has decreased by almost 20% within 1000 cycles of the initial cycle (L.Y, Sheng, et al. Boosting PEDOT energy storage with redox dopant and electrolyte additive, Chemical Engineering Journal, 2020, 401, 126123). SUMMARY

[0006] The application provides a 1-nitroanthraquinone covalently modified metal organic framework composite carbon nanotube self-supporting electrode and a preparation method thereof.

[0007] The technical scheme of the application is as follows:

[0008] The preparation method of the 1-nitroanthraquinone covalently modified metal organic framework composite carbon nanotube self-supporting electrode is as follows:

[0009] Step 1, carboxylated carbon nanotubes, 1-nitroterephthalic acid, zirconium tetrachloride, concentrated hydrochloric acid and 3-aminobenzoic acid are dissolved in N,N-dimethylformamide (DMF) to form a mixed solution, and hydrothermal reaction is carried out at 100-120℃. After the reaction is completed, the supernatant is removed by centrifugation, and the precipitate is washed with DMF and ethanol respectively to obtain a CNT@UiO-66-NO2 mixture;

[0010] Step 2, the CNT@UiO-66-NO2 mixture is dispersed in a mixed solvent of water and DMF, and 1-nitroanthraquinone is added, and then ultrasonic mixing is carried out until it is uniform. Hydrothermal reaction is carried out at 170-190℃, so that the nitro functional group is converted into an azo bond to covalently connect the anthraquinone molecules on the surface of the metal organic framework. After the reaction is completed, the supernatant is removed by centrifugation, and the precipitate is washed with DMF, dichloromethane (DCM) and ethanol respectively, and then vacuum filtration and drying are carried out to obtain a CNT@UiO-66-AQ self-supporting electrode.

[0011] Preferably, in step 1, the molar ratio of 1-nitroterephthalic acid to zirconium tetrachloride is 1:1.

[0012] Preferably, in step 1, the mass ratio of 1-nitroterephthalic acid and carboxylated carbon nanotubes is 85:20-100, more preferably 85:80.

[0013] Preferably, in step 1, the reaction time is 24-48 hours.

[0014] Preferably, in step 2, the volume ratio of water and DMF in the mixed solvent of water and DMF is 1:1-3:1.

[0015] Preferably, in step 2, the mass ratio of 1-nitroanthraquinone and CNT@UiO-66-NO2 is 1-1.5:1.

[0016] Preferably, in step 2, the reaction time is 12-14 hours.

[0017] The structure of the post-modified MOF composite in the CNT@UiO-66-AQ self-supporting electrode according to the present application is as follows:

[0018] R1 is a metal-organic framework UiO-66-NO2 formed by an organic ligand containing a nitro functional group.

[0019] Compared with the prior art, the present application has the following significant advantages:

[0020] (1) The anthraquinone small molecule and the metal-organic framework are connected by an azo bond in the present application, which will not fall off in subsequent use, and the anthraquinone molecule has redox activity and can improve the specific capacitance of the metal-organic framework;

[0021] (2) The carboxylated carbon nanotube is used as a substrate in the present application, which not only can improve the conductivity of the composite material, but also can make the self-supporting electrode prepared have high rate performance and cycle stability, and the carboxyl groups contained on the surface of the carbon nanotube can provide uniform nucleation sites for the metal-organic framework, which can participate in coordination reaction with metal ions, promote the nucleation of MOFs on the surface and uniform growth;

[0022] (3) The self-supporting electrode of the present application has excellent specific capacitance, and the specific capacitance is as high as 302 mF cm -2 , and high cycle stability, and after 5000 charge-discharge cycles, the specific capacitance has almost no decay, which has wide application prospect in the field of supercapacitors. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The high-resolution electron spectrograms of the CNT@UiO-66-NO2 electrode prepared for Comparative Example 1 and the electrode CNT@UiO-66-AQ prepared in Example 1.

[0024] Figure 2The transmission electron microscopy (TEM) images of the CNT@UiO-66-NO2 electrode prepared for Comparative Example 1 and the electrode CNT@UiO-66-AQ prepared for Example 1.

[0025] Figure 3 The charge-discharge curves of the CNT@UiO-66-NO2 electrode prepared for Comparative Example 1, the CNT@UiO-66-AQ electrode prepared for Example 1, the CNT@UiO-66-AQ electrode prepared for Example 2, and the CNT@UiO-66-AQ electrode prepared for Example 3 at a current density of 1 mA cm-2. -2

[0026] Figure 4 The rate performance comparison chart of the CNT@UiO-66-NO2 electrode prepared for Comparative Example 1 and the electrode CNT@UiO-66-AQ prepared for Example 1.

[0027] Figure 5 The cycle performance chart of the electrode CNT@UiO-66-AQ prepared for Example 1. DETAILED DESCRIPTION

[0028] The application will be further described in conjunction with the examples and the accompanying drawings.

[0029] Example 1

[0030] Preparation of the CNT@UiO-66-AQ self-supporting electrode:

[0031] Dissolve 1-nitroterephthalic acid (85 mg), zirconium tetrachloride (85 mg), concentrated hydrochloric acid (60 μl), and 3-aminobenzoic acid (89 mg) in 7 ml of DMF to obtain a transparent solution by ultrasonic treatment for half an hour. Mix the solution with a CNT suspension of 16 ml (5 mg / ml) and ultrasonically treat for 30 minutes to obtain a uniform mixture. Transfer the mixed suspension to a 50-ml Teflon liner in an autoclave, and perform hydrothermal reaction at 120°C for 48 hours. After cooling to room temperature, centrifugally remove the supernatant, and sequentially wash the precipitate with DMF and ethanol to obtain CNT@UiO-66-NO2 powder.

[0032] Dissolve CNT@UiO-66-NO2 powder (100 mg) and 1-nitroanthraquinone (100 mg) in a mixed solvent of 30 ml of water and 10 ml of DMF, and transfer the solution to an 80-ml Teflon liner in an autoclave after ultrasonic treatment for 30 minutes. Perform hydrothermal reaction at 180°C for 12 hours. After cooling to room temperature, centrifugally remove the supernatant, and sequentially wash the precipitate with DMF, DCM, and ethanol until the supernatant changes from red to clear. Suck-filter the precipitate into a film, and dry at 60°C for 12 hours to obtain a CNT@UiO-66-AQ self-supporting electrode.

[0033] ​The N1s high-resolution electronic spectrum of the product prepared in Example 1 is shown below. Figure 1 As shown in CNT@UiO-66-AQ, the loss of the nitro group and the formation of the azo bond are evident. Transmission electron microscopy (TEM) image is shown below. Figure 2 As shown in (a), anthraquinone small molecules are deposited on the surface of UiO-66-NO2. The prepared CNT@UiO-66-AQ self-supporting electrode is tested at 1 mA cm⁻¹. -2 The charge-discharge curves at current density are shown in the figure below. Figure 3 As shown in curve b, the specific capacitance is as high as 302 mF cm⁻¹. -2 Compared to Comparative Example 1, the specific capacitance was increased by four times, and the voltage window was widened. The rate performance of the electrode prepared in Example 1 is as follows: Figure 4 As shown in curve a, when the current density increases by 20 times, there is a capacitance retention rate of 71.6%, which is much higher than the retention rate of the electrode prepared in Comparative Example 1. The cycling stability of the electrode prepared in Example 1 is as follows: Figure 5 As shown, after 5000 charge-discharge cycles, the specific capacitance shows almost no degradation.

[0034] Comparative Example 1

[0035] Preparation of CNT@UiO-66-NO2 self-supporting electrode

[0036] 1-Nitroterephthalic acid (85 mg), zirconium tetrachloride (85 mg), concentrated hydrochloric acid (60 μl), and 3-aminobenzoic acid (89 mg) were dissolved in 7 ml of DMF and sonicated for half an hour to obtain a transparent solution. This solution was mixed with 16 ml (5 mg / ml) of CNT suspension and sonicated for another 30 minutes to ensure homogeneity. The mixed suspension was transferred to a 50 ml hydrothermal reactor with a tetrafluoroethylene substrate and hydrothermally reacted at 120 °C for 48 hours. After cooling to room temperature, the supernatant was removed by centrifugation. The precipitate was then washed sequentially with DMF and ethanol by centrifugation. The precipitate was filtered to form a membrane and dried at 60 °C for 12 hours to obtain a CNT@UiO-66-NO2 self-supporting electrode.

[0037] The N1s high-resolution electronic spectrum of the product prepared in Comparative Example 1 is shown below. Figure 1 As shown in CNT@UiO-66-NO2, the presence of nitro and amino groups is evident. Transmission electron microscopy (TEM) image is shown below. Figure 2 (b) shows the smooth surface of UiO-66-NO2. The prepared CNT@UiO-66-NO2 self-supporting electrode is shown at 1 mA cm⁻¹. -2 The charge-discharge curves at current density are shown in the figure below. Figure 3 As shown in curve a, the specific capacitance is 80 mF cm. -2 Its rate performance is as follows: Figure 4 As shown in curve b, when the current density increases by 10 times, only 55.5% of the capacitance is retained.

[0038] Example 2

[0039] The 1-nitroterephthalic acid (85 mg), zirconium tetrachloride (85 mg), concentrated hydrochloric acid (60 μl) and 3-aminobenzoic acid (89 mg) were dissolved in 7 ml DMF, and a transparent solution was obtained by ultrasonic treatment for half an hour. The solution was mixed with the CNT suspension 4 ml (5 mg / ml), and the mixture was uniformly mixed by ultrasonic treatment for 30 minutes. The mixed suspension was transferred to a hydrothermal kettle with a teflon liner of 50 ml, and hydrothermal reaction was carried out at 120°C for 48 hours. After cooling to room temperature, the supernatant was removed by centrifugation, and the precipitate was sequentially washed with DMF and ethanol to obtain CNT@UiO-66-NO2 powder.

[0040] The CNT@UiO-66-NO2 powder (100 mg) and 1-nitroanthraquinone (100 mg) were dissolved in a mixed solvent of 30 ml water and 10 ml DMF, and transferred to a hydrothermal kettle with a teflon liner of 80 ml after ultrasonic treatment for 30 min. Hydrothermal reaction was carried out at 180°C for 12 hours. After cooling to room temperature, the supernatant was removed by centrifugation, and the precipitate was sequentially washed with DMF, DCM and ethanol until the supernatant changed from red to clear. The precipitate was suction filtered into a film, and dried at 60°C for 12 hours to obtain a CNT@UiO-66-AQ self-supporting electrode.

[0041] The product prepared in Example 2 had a charge-discharge curve at a current density of 1 mA cm -2 , as shown in curve c in FIG. 2, and a specific capacitance of 250 mF cm -2 , which was slightly lower than that of the final product prepared in Example 1. Figure 3

[0042] Example 3

[0043] The 1-nitroterephthalic acid (85 mg), zirconium tetrachloride (85 mg), concentrated hydrochloric acid (60 μl) and 3-aminobenzoic acid (89 mg) were dissolved in 7 ml DMF, and a transparent solution was obtained by ultrasonic treatment for half an hour. The solution was mixed with the CNT suspension 4 ml (5 mg / ml), and the mixture was uniformly mixed by ultrasonic treatment for 30 minutes. The mixed suspension was transferred to a hydrothermal kettle with a teflon liner of 50 ml, and hydrothermal reaction was carried out at 120°C for 48 hours. After cooling to room temperature, the supernatant was removed by centrifugation, and the precipitate was sequentially washed with DMF and ethanol to obtain CNT@UiO-66-NO2 powder.

[0044] ​CNT@UiO-66-NO2 powder (100 mg) was dissolved in a mixed solvent of 30 ml water and 10 ml DMF with 1-nitroanthraquinone (100 mg), and after ultrasonic treatment for 30 min, it was transferred to a hydrothermal kettle with 80 ml tetrafluoroethylene liner. The hydrothermal reaction was carried out at 180 °C for 12 hours. After cooling to room temperature, the supernatant was removed by centrifugation. The precipitate was sequentially washed with DMF, DCM and ethanol by centrifugation until the supernatant changed from red to clear. The precipitate was filtered into a film, and dried at 60 °C for 12 hours to obtain a CNT@UiO-66-AQ self-supporting electrode.

[0045] The charge-discharge curve of the product prepared in Example 3 at a current density of 1 mA cm -2 is shown in curve d in FIG. 1, and the specific capacitance is 234 mF cm Figure 3 -2. The specific capacitance is slightly lower than that of the final product prepared in Example 1. -2 ​

Claims

1. A method for preparing a self-supporting electrode based on a 1-nitroanthraquinone covalently modified metal-organic framework composite carbon nanotube, characterized in that, The specific steps are as follows: Step 1: Carboxylated carbon nanotubes, 1-nitroterephthalic acid, zirconium tetrachloride, concentrated hydrochloric acid, and 3-aminobenzoic acid are dissolved in DMF to form a mixed solution. The solution is then subjected to hydrothermal reaction at 100-120℃. After the reaction is complete, the supernatant is removed by centrifugation. The precipitate is washed with DMF and ethanol respectively to obtain a mixture of CNT@UiO-66-NO2. Step 2: Disperse the CNT@UiO-66-NO2 mixture in a mixed solvent of water and DMF, then add 1-nitroanthraquinone, mix thoroughly by ultrasonication, and perform a hydrothermal reaction at 170-190℃ to convert the nitro functional group into an azo bond, covalently linking the anthraquinone molecule to the surface of the metal-organic framework. After the reaction is complete, centrifuge to remove the supernatant, wash the precipitate with DMF, DCM and ethanol respectively, filter and dry to obtain the CNT@UiO-66-AQ self-supporting electrode.

2. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of 1-nitroterephthalic acid to zirconium tetrachloride is 1:

1.

3. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of 1-nitroterephthalic acid to carboxylated carbon nanotubes is 85:20-100.

4. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of 1-nitroterephthalic acid to carboxylated carbon nanotubes is 85:

80.

5. The preparation method according to claim 1, characterized in that, In step 1, the reaction time is 24 to 48 hours.

6. The preparation method according to claim 1, characterized in that, In step 2, the volume ratio of water to DMF in the mixed solvent of water and DMF is 1:1 to 3:

1.

7. The preparation method according to claim 1, characterized in that, In step 2, the mass ratio of 1-nitroanthraquinone to CNT@UiO-66-NO2 is 1 to 1.5:

1.

8. The preparation method according to claim 1, characterized in that, In step 2, the reaction time is 12 to 14 hours.

9. A metal-organic framework composite carbon nanotube self-supporting electrode prepared by any one of the preparation methods according to claims 1 to 8.

10. The application of the metal-organic framework composite carbon nanotube self-supporting electrode according to claim 9 in supercapacitors.

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