Three-dimensional carbon nanotube modified graphite felt, and preparation method and application thereof

Abstract

The present application relates to the technical field of all-vanadium redox flow battery electrode, discloses a kind of three-dimensional carbon nanotube modified graphite felt and its preparation method and application, comprising the following steps: by twice vapor deposition carbon nanotube and solvothermal load phthalocyanine on graphite felt, then remove metal nickel by washing, obtain three-dimensional carbon nanotube modified graphite felt, load carbon nanotube on graphite felt can effectively improve conductivity, its three-dimensional structure can effectively increase the catalytic activity site of graphite felt, so as to improve the energy efficiency and voltage efficiency of all-vanadium redox flow battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of all-vanadium redox flow battery electrode, and particularly relates to a three-dimensional carbon nanotube modified graphite felt and a preparation method and application thereof. BACKGROUND

[0002] Graphite felt is widely used in all-vanadium redox flow batteries due to its low price, good chemical stability, high mechanical strength and other characteristics. However, as a vanadium battery electrode material, it has a small specific surface area and insufficient electrocatalytic activity, which has become a bottleneck restricting the further improvement of the energy efficiency of vanadium batteries. Carbon nanotubes have excellent chemical stability, electrical conductivity and large specific surface area, which makes it possible to further improve the electrocatalytic activity of graphite felt electrodes. In view of this, a three-dimensional carbon nanotube modified graphite felt and a preparation method and application thereof are provided. SUMMARY

[0003] The present application aims to provide a three-dimensional carbon nanotube modified graphite felt and a preparation method and application thereof to overcome the deficiencies in the prior art.

[0004] The first aspect of the present application provides a preparation method of a three-dimensional carbon nanotube modified graphite felt, comprising the following steps:

[0005] Step S1: dipping graphite felt in a nickel dispersion solution for reaction to obtain carbon nanotube modified graphite felt;

[0006] Step S2: mixing and stirring a nickel salt, a nitrile source and DMF uniformly, and adding the carbon nanotube modified graphite felt for hydrothermal treatment to obtain hydrothermally treated graphite felt;

[0007] Step S3: growing carbon nanotubes on the hydrothermally treated graphite felt by heat treatment to obtain precursor graphite felt;

[0008] Step S4: cleaning the precursor graphite felt with dilute hydrochloric acid and freeze-drying to obtain three-dimensional carbon nanotube modified graphite felt.

[0009] In a preferred embodiment, in the step S1:

[0010] The particle size of the nickel powder in the nickel dispersion solution is 100-200 nm, and the concentration of the nickel powder is 0.1 mol / L.

[0011] In a preferred embodiment, in the step S1:

[0012] After the graphite felt is dipped in the nickel dispersion solution for reaction, carbon nanotubes are grown by heat treatment, specifically: argon gas is introduced to heat to 750-850 DEG C, and then heat preservation is performed for 0.5 h, then acetylene gas is introduced at a flow rate of 80-120 sccm, and heat preservation is continued for 0.5-3 h, and finally argon gas is introduced to cool down.

[0013] The carbon nanotubes deposited by heat treatment can effectively improve the conductivity and specific surface area of the graphite felt, thereby improving the energy efficiency and voltage efficiency of the all-vanadium redox flow battery.

[0014] In a preferred embodiment, in the step S2:

[0015] The nickel salt is selected from at least one of nickel chloride, nickel nitrate;

[0016] The nitrile source is selected from at least one of 4-hydroxyphthalonitrile, 4,5-dihydroxyphthalonitrile, 4-amino-phthalonitrile, 4-chloro-phthalonitrile.

[0017] In a preferred embodiment, in the step S2:

[0018] The weight ratio of the nickel salt, the nitrile source and the DMF is 1:2:50.

[0019] In a preferred embodiment, in the step S2:

[0020] The temperature of the hydrothermal treatment is 140-180℃, and the time is 8-12h.

[0021] The two-dimensional phthalocyanine is formed by hydrothermal treatment of the nitrile source and the nickel salt, on the one hand, a large number of pores are produced after subsequent pyrolysis and hydrochloric acid treatment, which provides more catalytically active sites for the graphite felt, on the other hand, the carbon nanotubes can be further fixed on the carbon fibers of the graphite felt, improving the structural stability of the graphite felt, and also serving as an efficient catalyst in the generation process of the outermost carbon nanotubes.

[0022] In a preferred embodiment, in the step S3:

[0023] The method for growing the carbon nanotubes by heat treatment is: first, argon is introduced to heat to 750-850℃, and then heat preservation is performed for 0.5h, then a mixed gas composed of hydrogen and argon in a volume ratio of 5:95 is introduced, and then heat preservation is continued for 0.5h, then acetylene gas is introduced at a flow rate of 80-120sccm, and then heat preservation is continued for 0.5-1.5h, and finally argon is introduced to cool down.

[0024] The formation step of the outermost carbon nanotubes additionally introduces a mixed gas, which reduces the nickel oxide in situ to elemental nickel, and can improve the generation amount and bonding strength of the outermost carbon nanotubes.

[0025] In a preferred embodiment, in the step S4:

[0026] The temperature of the freeze-drying is -60℃, and the time is 15h.

[0027] The second aspect of the application provides a three-dimensional carbon nanotube modified graphite felt prepared by the preparation method.

[0028] The third aspect of the application provides an application of the three-dimensional carbon nanotube modified graphite felt, the three-dimensional carbon nanotube modified graphite felt prepared by the preparation method or the three-dimensional carbon nanotube modified graphite felt is applied to a vanadium redox flow battery.

[0029] The application has at least the following beneficial effects:

[0030] The carbon nanotubes deposited by vapor deposition in the application can effectively improve the electrical conductivity and specific surface area of the graphite felt, thereby improving the energy efficiency and voltage efficiency of the vanadium redox flow battery.

[0031] The three-dimensional carbon nanotube structure constructed by vapor deposition, solvothermal, vapor deposition and metal removal can provide more active sites for vanadium ion reaction.

[0032] The nitrile source and nickel salt form a two-dimensional phthalocyanine, and a large number of pores are generated after pyrolysis and hydrochloric acid treatment, thereby providing more catalytically active sites, and the nitrile source contains a large amount of N element, and the doping of the N element can improve the electrochemical performance of the battery.

[0033] The three-dimensional carbon nanotube structure constructed in the application can effectively improve the stability of the carbon nanotube structure loaded on the graphite felt and improve the cycle service life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The scanning electron microscope image of the three-dimensional carbon nanotube modified graphite felt prepared in Example 1 of the application. DETAILED DESCRIPTION

[0035] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application or its application or uses. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0036] Example 1: The following technical solutions are adopted

[0037] Step S1: 0.01 mol of nickel powder is ultrasonically dispersed in 100 g of deionized water to form a 0.1 mol / L nickel powder solution, and the graphite felt is immersed and dried;

[0038] Step S2: The dried graphite felt is placed in a tube furnace, argon is introduced to heat to 800 DEG C and keep for 0.5 h, then acetylene gas is introduced at a flow rate of 100 sccm and kept for 1 h, and finally argon is introduced to cool down to obtain a carbon nanotube modified graphite felt.

[0039] Step S3: 1 part by mass of nickel chloride, 2 parts by mass of 4-hydroxyphthalonitrile were dissolved in 50 parts by mass of DMF and mixed and stirred uniformly, and the carbon nanotube modified graphite felt was hydrothermally treated at 140 DEG C for 8 h;

[0040] Step S4: The graphite felt after hydrothermal treatment was washed and dried, placed in a tube furnace, argon was introduced to heat to 800 DEG C and kept for 0.5 h, then a mixed gas of 5:95 hydrogen and argon was introduced and kept for 0.5 h, finally acetylene gas was introduced and kept for 0.5 h, argon was introduced again to cool down to obtain a precursor graphite felt;

[0041] Step S5: The precursor graphite felt was placed in a 3 mol / L hydrochloric acid solution to remove the metal nickel, washed and freeze-dried to obtain a three-dimensional carbon nanotube modified graphite felt.

[0042] By Figure 1 The scanning electron microscope of the three-dimensional carbon nanotube modified graphite felt can be seen that the graphite felt surface is wrapped with carbon nanotubes and the carbon nanotubes have a three-dimensional structure.

[0043] Example 2: The following technical scheme is adopted

[0044] Step S1: 0.01 mol of nickel powder was ultrasonically dispersed in 100 g of deionized water to form a 0.1 mol / L nickel powder solution, and the graphite felt was immersed and dried;

[0045] Step S2: The dried graphite felt was placed in a tube furnace, argon was introduced to heat to 750 DEG C and kept for 0.5 h, then acetylene gas was introduced at a flow rate of 80 sccm and kept for 0.5 h, finally argon was introduced to cool down to obtain a carbon nanotube modified graphite felt;

[0046] Step S3: 1 part by mass of nickel nitrate, 2 parts by mass of 4,5-dihydroxyphthalonitrile were dissolved in 50 parts by mass of DMF and mixed and stirred uniformly, and the carbon nanotube modified graphite felt was hydrothermally treated at 180 DEG C for 12 h;

[0047] Step S4: The graphite felt after hydrothermal treatment was washed and dried, placed in a tube furnace, argon was introduced to heat to 750 DEG C and kept for 0.5 h, then a mixed gas of 5:95 hydrogen and argon was introduced and kept for 0.5 h, finally acetylene gas was introduced and kept for 0.25 h, argon was introduced again to cool down to obtain a precursor graphite felt;

[0048] Step S5: The precursor graphite felt was placed in a 3 mol / L hydrochloric acid solution to remove the metal nickel, washed and freeze-dried at -60 DEG C for 15 h to obtain a three-dimensional carbon nanotube modified graphite felt.

[0049] Example 3: The following technical scheme is adopted

[0050] Step S1: ultrasonic dispersion of 0.01 mol nickel powder in 100 g deionized water to form a 0.1 mol / L nickel powder solution, graphite felt impregnation, drying;

[0051] Step S2: placing the dried graphite felt in a tube furnace, passing argon to heat to 850℃ for 0.5 h, then passing 100 sccm of acetylene gas for 3 h, and finally passing argon to cool down to obtain carbon nanotube modified graphite felt;

[0052] Step S3: dissolving 1 part by mass of nickel chloride and 2 parts by mass of 4-amino phthalonitrile in 50 parts by mass of DMF, stirring uniformly, and adding the carbon nanotube modified graphite felt for hydrothermal treatment at 160℃ for 10 h;

[0053] Step S4: washing and drying the graphite felt after hydrothermal treatment, placing it in a tube furnace, passing argon to heat to 850℃ for 0.5 h, then passing a mixed gas of 5:95 hydrogen and argon for 0.5 h, finally passing acetylene gas for 1.5 h, and again passing argon to cool down to obtain a precursor graphite felt;

[0054] Step S5: placing the precursor graphite felt in a 3 mol / L hydrochloric acid solution to remove metallic nickel, washing, and freeze-drying at -60℃ for 15 h to obtain a three-dimensional carbon nanotube modified graphite felt.

[0055] Example 4: the following technical scheme is adopted

[0056] Step S1: ultrasonic dispersion of 0.01 mol nickel powder in 100 g deionized water to form a 0.1 mol / L nickel powder solution, graphite felt impregnation, drying;

[0057] Step S2: placing the dried graphite felt in a tube furnace, passing argon to heat to 800℃ for 0.5 h, then passing 100 sccm of acetylene gas for 2 h, and finally passing argon to cool down to obtain carbon nanotube modified graphite felt;

[0058] Step S3: dissolving 1 part by mass of nickel nitrate and 2 parts by mass of 4-chloro phthalonitrile in 50 parts by mass of DMF, stirring uniformly, and adding the carbon nanotube modified graphite felt for hydrothermal treatment at 180℃ for 8 h;

[0059] Step S4: washing and drying the graphite felt after hydrothermal treatment, placing it in a tube furnace, passing argon to heat to 800℃ for 0.5 h, then passing a mixed gas of 5:95 hydrogen and argon for 0.5 h, finally passing acetylene gas for 1 h, and again passing argon to cool down to obtain a precursor graphite felt;

[0060] Step S5: The precursor graphite felt is placed in a 3 mol / L hydrochloric acid solution to remove the metal nickel, washed, and freeze-dried at -60°C for 15 h to obtain a three-dimensional carbon nanotube modified graphite felt.

[0061] Comparative Example 1: The following technical solution is used

[0062] The preparation process is consistent with Example 1, except that no nickel salt is involved in step S3.

[0063] Comparative Example 2: The following technical solution is used

[0064] The preparation process is consistent with Example 1, except that no nitrile source is involved in step S3.

[0065] Comparative Example 3: The following technical solution is used

[0066] The preparation process is consistent with Example 1, except that step S5 is not performed.

[0067] Comparative Example 4: The following technical solution is used

[0068] The preparation process is consistent with Example 1, except that the mixed gas in step S4 is replaced with argon.

[0069] 1. Battery test: The graphite felt prepared in the examples and comparative examples is assembled into an electric pile, and the coulomb efficiency, energy efficiency and voltage efficiency of the electric pile are recorded under the same working condition.

[0070] 2. Powder loss test: The graphite felt prepared in the examples and comparative examples is cut into 3*3 cm and placed in deionized water, oscillated at 30°C for 3 h, then washed with deionized water, dried, and the mass change before and after the graphite felt is weighed.

[0071] The test results are shown in Table 1:

[0072] Table 1: Performance test results of graphite felt in examples and comparative examples

[0073]

[0074] The above test results show that, compared with Comparative Example 1, Examples 1-4 have higher voltage efficiency and energy efficiency, indicating that although the nitrile source is loaded on the graphite felt, the catalytic active sites provided are limited without the participation of nickel salt; compared with Comparative Example 2, Examples 1-4 have higher voltage efficiency and energy efficiency, indicating that although the nickel salt is loaded on the graphite felt, the catalytic active sites provided are limited without the participation of the nitrile source; compared with Comparative Example 3, Examples 1-4 have higher voltage efficiency and energy efficiency, indicating that the three-dimensional carbon nanotube structure constructed by gas deposition, solvothermal, gas deposition and metal removal can provide more active sites for vanadium ion reaction. Compared with Comparative Examples 1-4, Examples 1-4 have better voltage efficiency retention after 200 cycles and smaller change in graphite felt mass, indicating that the three-dimensional carbon nanotube structure constructed by the present application can effectively improve the stability of the carbon nanotube structure loaded on the graphite felt and improve the cycle life of the battery.

[0075] 3. Carbon nanotube yield and structure strength test

[0076] Take 12 pieces of graphite felt of the same specification, test the initial mass, then take 3 pieces of graphite felt each and treat the graphite felt with the preparation methods of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4, respectively, weigh the mass of the graphite felt after the end, and calculate the average mass change M1 of the graphite felt before and after. Finally, place the graphite felt in deionized water, oscillate at 30°C for 3h, then rinse with deionized water, dry, and weigh the average mass change M2 of the graphite felt before and after. The results are shown in Table 2:

[0077] Table 2 Mass change of graphite felt of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4

[0078]

[0079] As can be seen from Table 2, M1 of Example 1 is greater than that of Comparative Example 4, indicating that the use of mixed gas in the formation step of the outermost layer of carbon nanotubes can reduce nickel oxide to elemental nickel in situ, increase the yield of the outermost layer of carbon nanotubes, and the results of M2 show that Example 1 has smaller mass loss than Comparative Example 4, indicating that the carbon nanotubes in Example 1 have greater bonding strength. M1 and M2 of Example 1 are greater than those of Comparative Examples 1 and 2, indicating that the phthalocyanine in the intermediate layer can not only increase the active sites of the graphite felt during the operation of the vanadium battery, but also act as an efficient catalyst during the formation of the outermost layer of carbon nanotubes, and can also fix the inner layer of carbon nanotubes to improve the structural stability.

[0080] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a three-dimensional carbon nanotube-modified graphite felt, characterized by, The method comprises the following steps: Step S1: reacting graphite felt in a nickel dispersion solution to obtain carbon nanotube modified graphite felt; after the graphite felt is reacted in the nickel dispersion solution, carbon nanotubes are grown by heat treatment, specifically: first, argon is introduced to heat to 750-850℃, and then heat preservation is performed for 0.5h; then, acetylene gas is introduced at a flow rate of 80-120sccm, and heat preservation is continued for 0.5-3h; finally, argon is introduced to cool down; Step S2: mixing and stirring a nickel salt, a nitrile source and DMF uniformly, and then adding the carbon nanotube modified graphite felt to perform hydrothermal treatment to obtain hydrothermally treated graphite felt; the nitrile source is at least one selected from 4-hydroxyphthalonitrile, 4,5-dihydroxyphthalonitrile, 4-amino-phthalonitrile and 4-chlorophthalonitrile; Step S3: growing carbon nanotubes by heat treatment on the hydrothermally treated graphite felt to obtain a precursor graphite felt; the method for growing carbon nanotubes by heat treatment is as follows: first, argon is introduced to heat to 750-850℃, and then heat preservation is performed for 0.5h; then, a mixed gas composed of hydrogen and argon at a volume ratio of 5:95 is introduced, and heat preservation is continued for 0.5h; then, acetylene gas is introduced at a flow rate of 80-120sccm, and heat preservation is continued for 0.5-1.5h; finally, argon is introduced to cool down; Step S4: cleaning the precursor graphite felt with dilute hydrochloric acid, and freeze-drying to obtain a three-dimensional carbon nanotube modified graphite felt.

2. The production method according to claim 1, wherein In the step S1: The particle size of the nickel powder in the nickel dispersion solution is 100-200nm, and the concentration of the nickel powder is 0.1mol / L.

3. The production method according to claim 1, wherein In the step S2: The nickel salt is at least one selected from nickel chloride and nickel nitrate.

4. The production method according to claim 1, wherein In the step S2: The weight ratio of the nickel salt, the nitrile source and the DMF is 1:2:

50.

5. The production method according to claim 1, wherein In the step S2: The temperature of the hydrothermal treatment is 140-180℃, and the time is 8-12h.

6. The production method according to claim 1, wherein In the step S4: The temperature of the freeze-drying is -60℃, and the time is 15h.

7. A three-dimensional carbon nanotube modified graphite felt, characterized by, The three-dimensional carbon nanotube modified graphite felt is prepared by the preparation method in any one of claims 1-6.

8. Use of a three-dimensional carbon nanotube-modified graphite felt, characterized by, The three-dimensional carbon nanotube modified graphite felt prepared by the preparation method in any one of claims 1-6 or the three-dimensional carbon nanotube modified graphite felt in claim 7 is applied to a full vanadium liquid flow battery.

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