A preparation method of a cobalt-based carbon nanotube film

Abstract

The present invention provides a method for preparing a cobalt-based carbon nanotube film. First, a cobalt hydroxide fluoride precursor is prepared on a substrate by a hydrothermal method, and then phenolic resin is coated on the precursor. Then, using dicyandiamide as the solid source, under a protective atmosphere, a cobalt-based nitrogen-doped carbon nanotube is prepared by chemical vapor deposition (CVD method). Since the prepared carbon nanotubes are uniform, have a relatively long length, and are uniformly wound around the substrate fibers, forming a tight whole with the substrate, a cobalt-based carbon nanotube film with relatively high mechanical strength is formed. If carbon cloth and stainless steel mesh are used as the substrate, the prepared cobalt-based carbon nanotube film can be repeatedly bent and kneaded without powder falling off.

Description

Technical Field

[0001] The present invention relates to the preparation and application of a cobalt-based nitrogen-doped carbon nanotube film, belonging to the fields of energy and environmental catalysis. Background Art

[0002] In modern society, the demand for energy is increasing, and the global energy and environmental crises are intensifying. Catalysts are of great significance for energy conversion and storage, environmental protection, etc. As a carbon material, carbon nanotubes have many advantages such as corrosion resistance, high electrical conductivity, and easy modification of various active sites, and are a very promising catalytic material. Industrially, carbon nanotube powders are generally synthesized by methods such as CVD and arc discharge, and then carbon nanotube aggregates (such as carbon nanotube papers and carbon nanotube ropes) are obtained through processes such as powder pulping and other processes. If these aggregates are used for catalysis, additional nitrogen doping, functional group modification, loading of other active particles, etc. are required. Summary of the Invention

[0003] In view of this, the present invention provides a method for preparing a cobalt-based carbon nanotube film by CVD carbonization of cobalt hydroxide fluoride, that is, a method for preparing a cobalt-based nitrogen-doped carbon nanotube film by preparing a cobalt hydroxide fluoride nanowire array by a hydrothermal method, then wrapping phenolic resin on its surface and annealing in a dicyandiamide decomposition atmosphere. The preparation includes the following steps:

[0004] S1. Prepare the precursor of cobalt hydroxide fluoride: At room temperature, dissolve cobalt nitrate hexahydrate, urea, and ammonium fluoride in deionized water, where the concentration of cobalt nitrate hexahydrate is 1 mM - 3 mM, the concentration of urea is 6 mM - 12 mM, and the concentration of ammonium fluoride is 2 mM - 6 mM. Stir until the solution is clear, then transfer the substrate (carbon cloth, carbon paper, 100-mesh stainless steel mesh, 500-mesh stainless steel mesh) and the solution to a hydrothermal autoclave, seal it, and place it in a hydrothermal oven for heat preservation. After reacting at 120°C - 160°C for 2 h - 6 h, cobalt hydroxide fluoride can grow on the surface of the substrate. The precursor array attached to the substrate is uniform and very firm, and the surface of the substrate is pink. Taking the 500-mesh fine stainless steel wire as an example, SEM observes that cobalt hydroxide fluoride nanowires grow uniformly on the stainless steel wire fibers, forming an outwardly divergent and relatively ordered array.

[0005] S2. Coating with phenolic resin: At room temperature, place the substrate with cobalt fluoride hydroxide grown in S1 into a mixed solution containing ammonia water, absolute ethanol, resorcinol, and deionized water for 30 min. Then, gradually add dropwise a mixed solution containing formaldehyde and deionized water. After 12 - 24 h, a phenolic resin precursor coating is obtained. Note: First, place the substrate with cobalt fluoride hydroxide into the solution containing resorcinol to allow the surface of cobalt fluoride hydroxide to fully adsorb resorcinol molecules. Then, gradually add dropwise the solution containing formaldehyde to ensure that formaldehyde reacts preferentially with resorcinol on the surface of cobalt fluoride hydroxide to form oligomers and then high polymers to coat the surface of cobalt fluoride hydroxide. Here, resorcinol is used to replace phenol (or p-phenol). Under the catalysis of a base, polymerization can occur at room temperature, thus avoiding the Ostwald ripening of cobalt fluoride hydroxide caused by heating. In addition, after the polycondensation of resorcinol and aldehyde, there are many hydroxyl groups, and the hydrophilicity is much higher than that of the resin of phenol and formaldehyde, which is conducive to the coating of the resin on the substrate material rather than precipitating from the solution preferentially.

[0006] S3. Preparation of cobalt-based carbon nanotube film: Place the precursor of the phenolic resin-coated (grown on the substrate) in the center of a tubular furnace. Use an inert gas as the carrier gas. Put dicyandiamide at the front end of the tubular furnace. Perform CVD reaction at 700 - 900 °C for 1 - 3 h, and then take it out after natural cooling.

[0007] The step of coating with phenolic resin cannot be omitted. Cobalt fluoride hydroxide will be reduced to metallic cobalt in an inert atmosphere and catalyze the growth of carbon nanotubes. At the same time, a large amount of nitrogen will be generated during the decomposition of dicyandiamide to form nitrogen-doped carbon nanotubes. However, without coating with a high polymer, a) carbon nanotubes will accumulate on the surface of the substrate pores due to too fast growth rate instead of growing / wrapping on the fibers inside the substrate; b) the metallic cobalt generated by reduction is easy to aggregate and grow without a high polymer carbonized layer coating. The carbon nanotubes catalyzed by it are very thick, short, or cannot catalyze the growth of long carbon nanotubes and can only form a structure of carbon-coated metal particles.

[0008] The present invention provides a one-step high-temperature CVD reaction to obtain an aggregate with high Co and N contents, cobalt metal particles embedded, and carbon nanotubes wound around the substrate fibers for toughening. In-situ winding growth forms a porous membrane or paper on carbon cloth CC, carbon paper CFP, and stainless steel wire mesh SS substrates with different specifications with a thickness of 0.1 - 2 mm. The cobalt-based carbon nanotube film has good electrocatalytic hydrogen evolution, oxygen evolution, and redox performance, and also has the application prospect of catalyzing the activation of persulfate for environmental catalytic degradation of pollution and sterilization. Description of the Drawings

[0009] Figure 1Digital photos of Example 1. Among them, Figure (a) shows the cobalt hydroxyfluoride precursor grown on a 100-mesh stainless steel mesh, and the inset is the blank sample (100-mesh coarse stainless steel mesh); Figure (b) shows the 100-mesh coarse stainless steel mesh with phenolic resin coated on the cobalt hydroxyfluoride precursor; Figure (c) shows the digital photo of the cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; Figure (d) shows the digital photo of the 100-mesh coarse stainless steel mesh coated with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0010] Figure 2 Digital photos of Example 2. Among them, Figure (a) shows the cobalt hydroxyfluoride precursor grown on a 100-mesh stainless steel mesh, and the inset is the blank sample (100-mesh coarse stainless steel mesh); Figure (b) shows the 100-mesh coarse stainless steel mesh with phenolic resin coated on the cobalt hydroxyfluoride precursor; Figure (c) shows the digital photo of the cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; Figure (d) shows the digital photo of the 100-mesh coarse stainless steel mesh coated with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0011] Figure 3 Digital photos of Example 3. Among them, Figure (a) shows the cobalt hydroxyfluoride precursor grown on a 100-mesh coarse stainless steel mesh, and the inset is the blank sample (100-mesh coarse stainless steel mesh); Figure (b) shows the 100-mesh coarse stainless steel mesh with phenolic resin coated on the cobalt hydroxyfluoride precursor; Figure (c) shows the digital photo of the cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; Figure (d) shows the digital photo of the 100-mesh coarse stainless steel mesh coated with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0012] Figure 4 Digital photos of Example 4. Among them, Figure (a) shows the cobalt hydroxyfluoride precursor grown on a 500-mesh fine stainless steel mesh, and the inset is the blank sample (500-mesh fine stainless steel mesh); Figure (b) shows the 500-mesh fine stainless steel mesh with phenolic resin coated on the cobalt hydroxyfluoride precursor; Figure (c) shows the digital photo of the cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; Figure (d) shows the digital photo of the 500-mesh fine stainless steel mesh coated with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0013] Figure 5 Digital photos of Example 5. Among them, Figure (a) shows the cobalt hydroxyfluoride precursor grown on a 500-mesh fine stainless steel mesh, and the inset is the blank sample (500-mesh fine stainless steel mesh); Figure (b) shows the 500-mesh fine stainless steel mesh with phenolic resin coated on the cobalt hydroxyfluoride precursor; Figure (c) shows the digital photo of the cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; Figure (d) shows the digital photo of the 500-mesh fine stainless steel mesh coated with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0014] Figure 6Digital photos of Example 6. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on a 500-mesh fine stainless steel mesh, and the inset is the blank sample (500-mesh fine stainless steel mesh); in Figure (b), a 500-mesh fine stainless steel mesh coated with phenolic resin on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of the cobalt hydroxyfluoride precursor directly annealed in the atmosphere of dicyandiamide and argon; in Figure (d), digital photo of the 500-mesh fine stainless steel mesh coated with phenolic resin annealed in the atmosphere of dicyandiamide and argon.

[0015] Figure 7 Digital photos of the 500-mesh fine stainless steel mesh after annealing in Example 6 after being bent. Among them, (e) - (h) are photos of repeatedly pressing / releasing with fingers after bending.

[0016] Figure 8 Digital photos of Example 7. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on carbon cloth, and the inset is the blank sample (carbon cloth); in Figure (b), carbon cloth coated with phenolic resin on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of the cobalt hydroxyfluoride precursor directly annealed in the atmosphere of dicyandiamide and argon; in Figure (d), digital photo of the carbon cloth coated with phenolic resin annealed in the atmosphere of dicyandiamide and argon.

[0017] Figure 9 Digital photos of Example 8. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on carbon paper, and the inset is the blank sample (carbon paper); in Figure (b), carbon paper coated with phenolic resin on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of the cobalt hydroxyfluoride precursor directly annealed in the atmosphere of dicyandiamide and argon; in Figure (d), digital photo of the carbon paper coated with phenolic resin annealed in the atmosphere of dicyandiamide and argon.

[0018] Figure 10 Digital photos of Example 9. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on a 100-mesh coarse stainless steel mesh, and the inset is the blank sample (100-mesh coarse stainless steel mesh); in Figure (b), carbon paper coated with phenolic resin on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of the cobalt hydroxyfluoride precursor directly annealed in the atmosphere of dicyandiamide and argon; in Figure (d), digital photo of the 100-mesh coarse stainless steel mesh coated with phenolic resin annealed in the atmosphere of dicyandiamide and argon.

[0019] Figure 11 Digital photos of Example 10. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on a 500-mesh fine stainless steel mesh, and the inset is the blank sample (500-mesh fine stainless steel mesh); in Figure (b), carbon paper coated with phenolic resin on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of the cobalt hydroxyfluoride precursor directly annealed in the atmosphere of dicyandiamide and argon; in Figure (d), digital photo of the 500-mesh fine stainless steel mesh coated with phenolic resin annealed in the atmosphere of dicyandiamide and argon.

[0020] Figure 12 Digital photos of Example 11. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on a 500-mesh fine stainless steel mesh, and the inset is the blank sample (500-mesh fine stainless steel mesh); in Figure (b), carbon paper wrapped with phenolic resin is on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; in Figure (d), digital photo of a 500-mesh fine stainless steel mesh wrapped with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0021] Figure 13 Digital photos of Example 12. Among them, in Figure (a), cobalt hydroxyfluoride precursor grows on a 500-mesh fine stainless steel mesh, and the inset is the blank sample (500-mesh fine stainless steel mesh); in Figure (b), carbon paper wrapped with phenolic resin is on the cobalt hydroxyfluoride precursor; in Figure (c), digital photo of cobalt hydroxyfluoride precursor directly annealed in a dicyandiamide and argon atmosphere; in Figure (d), digital photo of a 500-mesh fine stainless steel mesh wrapped with phenolic resin annealed in a dicyandiamide and argon atmosphere.

[0022] Figure 14 SEM photos of Example 1, (a) 10,000 times (b) 500 times.

[0023] Figure 15 SEM photos of Example 2, (a) 10,000 times (b) 500 times.

[0024] Figure 16 SEM photos of Example 3, (a) 10,000 times (b) 500 times.

[0025] Figure 17 SEM photos of Example 5, (a) 20,000 times (b) 500 times.

[0026] Figure 18 SEM photos of Example 9, (a) 20,000 times (b) 500 times.

[0027] Figure 19 OER linear voltammetry scanning curves measured for the samples prepared in Example 4 and Example 5.

[0028] Figure 20 OER linear voltammetry scanning curve, HER linear voltammetry scanning curve and ORR linear voltammetry scanning curve measured for the sample prepared in Example 6. a is the OER linear voltammetry scanning curve of Example 6, b is the HER linear voltammetry scanning curve of Example 6, and c is the ORR linear voltammetry scanning curve of Example 6.

[0029] Figure 21OER linear voltammetry scanning curve measured for the sample prepared in Example 7.

[0030] Figure 22 OER linear voltammetry scanning curve, HER linear voltammetry scanning curve and ORR linear voltammetry scanning curve measured for the sample prepared in Example 11, wherein, a is the OER linear voltammetry scanning curve of Example 11, b is the HER linear voltammetry scanning curve of Example 11, and c is the ORR linear voltammetry scanning curve of Example 11.

[0031] Figure 23 OER linear voltammetry scanning curve, HER linear voltammetry scanning curve and ORR linear voltammetry scanning curve measured for the sample prepared in Example 12, wherein, a is the OER linear voltammetry scanning curve of Example 12, b is the HER linear voltammetry scanning curve of Example 12, and c is the ORR linear voltammetry scanning curve of Example 12. Specific implementation scheme

[0032] HER, ORR and OER performance LSV test methods in the invention examples: The test is carried out by using a three-electrode system. The sample prepared in the example is used as the working electrode, a carbon rod is used as the counter electrode, and a saturated Hg / HgO electrode is used as the reference electrode. Oxygen needs to be introduced to reach oxygen saturation before the HER, OER and ORR tests can be carried out. The electrolytes used for the HER test, OER test and ORR test are 1M KOH aqueous solution, and the solution is stirred and rotated at 100 revolutions per minute with a magnetic stirrer during the test. The saturated Hg / HgO electrode is calibrated with a reversible hydrogen electrode, and the potentials described hereinafter are all potentials relative to the reversible hydrogen electrode. In the LSV test, the potential ( IR -95%) compensation is automatically carried out by using a Shanghai Chenhua workstation. An X-ray diffractometer of SMART LAB-9 type is used to record the X-ray diffraction pattern. A scanning electron microscope image is obtained by using an Inspect F50 scanning electron microscope (FEI America).

[0033] Example 1

[0034] At room temperature, first, a 100-mesh coarse stainless steel mesh (SS-2) is subjected to hydrophilic treatment, and then 0.582 g of Co(NO 3 ) 2 ·6H 20.6 g of urea and 0.185 g of ammonium fluoride were dissolved in 60 mL of deionized water, and stirred until the solution was clear to form a solution. Subsequently, a 100-mesh coarse stainless steel mesh (SS-2) and the solution were placed in a polytetrafluoroethylene liner and sonicated for 15 min. Then it was sealed and placed in a hydrothermal oven at 130 °C for 3 h. After the oven temperature cooled to room temperature, the SS-2 with cobalt fluoride hydroxide arrays grown in-situ was taken out and rinsed with deionized water multiple times, and then dried at 60 °C for 30 min. Next, the above-prepared SS-2 was placed in a mixed solution containing 0.1 mL of 25% ammonia water, 28.6 mL of ethanol, 40 mg of resorcinol, and 41.4 mL of deionized water and ice-bathed for 30 min. Then, 30 mL of deionized water containing 0.112 mL of formaldehyde was added dropwise under the condition of ice bath. Subsequently, it was stirred at room temperature for 24 h. After the stirring ended, the SS-2 was taken out and rinsed with deionized water multiple times, and dried at 60 °C for 30 min. Finally, the SS-2 wrapped with phenolic resin was placed in the center of a tubular furnace, with argon as the carrier gas. 1 g of dicyandiamide was placed at the front end of the tubular furnace. Starting from room temperature, it was heated at a heating rate of 5 °C / min to 350 °C and held for 2 h, then heated at a heating rate of 2 °C / min to 800 °C and held for 2 h, and then cooled to 200 °C at a rate of 5 °C / min, and then naturally cooled to room temperature and taken out to prepare Co-NCNTs.

[0035] Figure 1 is the digital photo of Example 1, Figure 14 is the SEM image after the hydrothermal reaction of Example 1. It can be seen from the SEM image that outwardly divergent and relatively ordered cobalt fluoride hydroxide nanowire arrays grew uniformly on the surface of the 100-mesh coarse stainless steel mesh.

[0036] Example 2

[0037] The method and steps were the same as those in Example 1, only the hydrothermal reaction temperature was 140 °C, and the product Co-NCNTs was obtained.

[0038] Figure 2 is the digital photo of Example 2, Figure 15 is the SEM image after the hydrothermal reaction of Example 2. It can be seen from the SEM image that outwardly divergent and relatively ordered cobalt fluoride hydroxide nanowire arrays grew uniformly on the surface of the 100-mesh coarse stainless steel mesh.

[0039] Example 3

[0040] The method and steps were the same as those in Example 1, only the hydrothermal reaction temperature was 150 °C, and the product Co-NCNTs was obtained.

[0041] Figure 3 is the digital photo of Example 3, Figure 16It is the SEM image after the hydrothermal reaction in Example 3. It can be seen from the SEM image that an array of cobalt hydroxide fluoride nanowires that diverge outward and are relatively ordered has grown uniformly on the surface of the 100-mesh coarse stainless steel mesh.

[0042] Example 4

[0043] The method and steps are the same as those in Example 1, except that the substrate is replaced with a 500-mesh fine stainless steel mesh (SS-1), and the addition amount of ammonium fluoride during the hydrothermal reaction is 0.1481 g, and the addition amount of urea is 0.6006 g; and during the process of wrapping phenolic resin, the addition amount of resorcinol is 20 mg; then the product Co-NCNTs is obtained.

[0044] Figure 4 It is the digital photo of Example 4. Figure 19 It is the OER linear voltammogram of Example 4. From Figure 19 the OER linear voltammetry scanning curve measured for the sample prepared in Example 4 under the test condition of 1 M KOH, it can be seen that during the OER process, when the current density passing through the electrode is 10 mA / cm 2 , the overpotential corresponding to oxygen evolution in the OER reaction in the alkaline aqueous solution is 257 mV; the potential corresponding to oxygen evolution in the OER reaction is E 10 = 1.487 V.

[0045] Example 5

[0046] The method and steps are the same as those in Example 4, except that the addition amount of resorcinol is 40 mg; then the product Co-NCNTs is obtained.

[0047] Figure 5 It is the digital photo of Example 5. Figure 17 It is the SEM image after annealing of Example 5. Figure 19 It is the OER linear voltammogram of Example 5. It can be seen from the SEM image that the carbon nanotubes are uniformly wrapped on the 500-mesh fine stainless steel mesh, and the annealed nanotubes are wound on the surface of the 500-mesh stainless steel mesh. From Figure 19 the OER linear voltammetry scanning curve measured for the sample prepared in Example 5 under the test condition of 1 M KOH, it can be seen that during the OER process, when the current density passing through the electrode is 10 mA / cm 2 , the overpotential corresponding to oxygen evolution in the OER reaction in the alkaline aqueous solution is 267 mV; the potential corresponding to oxygen evolution in the OER reaction is E 10 = 1.497 V.

[0048] Example 6

[0049] The method and steps are the same as those in Example 4, except that the addition amount of resorcinol is 60 mg; then the product Co-NCNTs is obtained.

[0050] Figure 6 It is the digital photo of Example 6. Figure 20 They are the OER linear voltammetry scanning curve, HER linear voltammetry scanning curve and ORR linear voltammetry scanning curve measured for the sample prepared in Example 6.

[0051] From Figure 20 the OER, HER and ORR linear voltammetry scanning curves measured for the sample prepared in Example 12 under the test condition of 1 M KOH in 2 it can be seen that when the current density passing through the electrode is 10 mA / cm 10 during the OER process, the overpotential corresponding to oxygen production in the OER reaction in the alkaline aqueous solution is 259 mV, and the potential corresponding to oxygen production in the OER reaction is E 2 = 1.489 V; when the current density passing through the electrode is 10 mA / cm 1 / 2 during the HER process, the overpotential corresponding to oxygen production in the HER reaction in the alkaline aqueous solution is 249 mV; the half-wave potential corresponding to the ORR reaction is E 10 = 0.866 V, ΔE = E 1 / 2 - E

[0052] It should be noted that if the cobalt hydroxide fluoride precursor is directly annealed in a dicyandiamide and argon atmosphere (that is, without the step of wrapping with phenolic resin), the prepared sample, especially when the toughness of the substrate itself is insufficient (the 500-mesh fine stainless steel mesh will become brittle when annealed at a high temperature above 700 °C), is very easy to break, as Figure 6 (c) shows. However, the carbon nanotubes prepared by the method of the present invention are toughened due to the growth of the internal fibers of the winding substrate, the sample does not break, and can be bent repeatedly, as Figure 7 (e)-(h) show.

[0053] Example 7

[0054] The method and steps are the same as those in Example 4, only the addition amount of resorcinol is 80 mg; then the product Co-NCNTs is obtained.

[0055] Figure 8 It is the digital photo of Example 7, Figure 21 and it is the OER linear voltammetry curve of Example 7. From Figure 21 the OER linear voltammetry scanning curve measured for the sample prepared in Example 7 under the test condition of 1 M KOH in 2 it can be seen that when the current density passing through the electrode is 10 mA / cm 10 during the OER process, the overpotential corresponding to oxygen production in the OER reaction in the alkaline aqueous solution is 262 mV; the potential corresponding to oxygen production in the OER reaction is E

[0056] Example 8

[0057] The method and steps are the same as those in Example 5, except that the substrate is replaced with carbon cloth (CC), and the product Co-NCNTs is obtained.

[0058] Figure 9 It is the digital photo of Example 8.

[0059] Example 9

[0060] The method and steps are the same as those in Example 8, except that the substrate is replaced with carbon paper (CFP), and the product Co-NCNTs is obtained.

[0061] Figure 10 It is the digital photo of Example 9. Figure 18 It is the SEM photo of Example 9 after annealing.

[0062] Example 10

[0063] The method and steps are the same as those in Example 1, except that SS-2 wrapped with phenolic resin is mixed with 1 g of dicyandiamide and then put into a tubular furnace. Under an argon atmosphere, it is heated from room temperature to 350 °C at a heating rate of 5 °C / min and held for 2 h, then heated to 800 °C at a heating rate of 2 °C / min and held for 2 h, and then cooled to 200 °C at a rate of 5 °C / min, and taken out after natural cooling to room temperature to prepare Co-NCNTs.

[0064] Figure 11 It is the digital photo of Example 10.

[0065] Example 11

[0066] The method and steps are the same as those in Example 6, except that it is finally heated to 700 °C and held for 2 h to obtain the product Co-NCNTs.

[0067] Figure 12 It is the digital photo of Example 11. Figure 22 It is the linear voltammetry curves of OER, HER and ORR of Example 11 under the test conditions of 1M KOH. From Figure 22 the OER, HER and ORR linear voltammetry scanning curves measured from the sample prepared in Example 11 under the test conditions of 1 M KOH in, it can be seen that during the OER process, when the current density passing through the electrode is 10 mA / cm 2 , the overpotential corresponding to oxygen evolution in the OER reaction in the alkaline aqueous solution is 205 mV, and the potential corresponding to oxygen evolution in the OER reaction is E 10 = 1.435V; during the HER process, when the current density passing through the electrode is 10 mA / cm 2At this time, the overpotential corresponding to hydrogen production in the HER reaction in the alkaline aqueous solution is 248 mV; the half-wave potential corresponding to the ORR reaction is E 1 / 2 = 0.905 V, ΔE = E 10 - E 1 / 2 = 0.53 V.

[0068] Example 12

[0069] The method and steps are the same as those in Example 6, except that the temperature is finally raised to 900 °C and kept warm for 2 h to obtain the product Co-NCNTs.

[0070] Figure 13 It is a digital photo. Figure 23 For the linear voltammetry curves of OER, HER and ORR in Example 12 under the test conditions of 1 M KOH. From Figure 23 the OER, HER and ORR linear voltammetry scanning curves measured by the sample prepared in Example 12 under the test conditions of 1 M KOH in it, it can be seen that during the OER process, when the current density passing through the electrode is 10 mA / cm 2 At this time, the overpotential corresponding to oxygen production in the OER reaction in the alkaline aqueous solution is 252 mV, and the potential corresponding to oxygen production in the OER reaction is E 10 = 1.482 V; during the HER process, when the current density passing through the electrode is 10 mA / cm 2 At this time, the overpotential corresponding to hydrogen production in the HER reaction in the alkaline aqueous solution is 245 mV; the half-wave potential corresponding to the ORR reaction is E 1 / 2 = 0.876 V, ΔE = E 10 - E 1 / 2 = 0.606 V.

Claims

1. A preparation method of a cobalt-based carbon nanotube film, characterized in that, the specific preparation method is as follows: S1. Prepare the precursor of cobalt basic fluoride: Dissolve cobalt nitrate hexahydrate, urea and ammonium fluoride in deionized water to obtain a mixed solution. Then, put the substrate and the mixed solution into a polytetrafluoroethylene inner liner, seal it and put it into a hydrothermal box to keep warm for a certain time. After rinsing and drying, obtain a needle-like cobalt basic fluoride array; S2. Coating with phenolic resin: At room temperature, hang the needle-like cobalt basic fluoride array in a mixed solution containing ammonia water, absolute ethanol, resorcinol and deionized water. Then, dropwise add a mixed solution containing formaldehyde and deionized water. After standing for a period of time, obtain a precursor of coated phenolic resin. The concentration of the resorcinol is 0.2 - 1.2 mg / mL, the molar ratio of resorcinol to formaldehyde is 1:1 - 2, the volume ratio of absolute ethanol to water is 1:2 - 3, the addition amount of ammonia water is 0.05% - 0.2% of the total solution volume, and polymerize at room temperature for 12 h - 36 h; S3. Prepare the cobalt-based carbon nanotube film: Put the precursor of coated phenolic resin in the center of a tube furnace, use an inert gas as the carrier gas, put dicyandiamide at the front end of the tube furnace, and the mass ratio of dicyandiamide to the precursor of coated phenolic resin is 10 - 30:

1. Carry out CVD reaction at a certain temperature for 1 - 3 h, and take it out after natural cooling.

2. The preparation method of the cobalt-based carbon nanotube film according to claim 1, characterized in that, in S1, the concentration of cobalt nitrate hexahydrate in the mixed solution is 1 mM - 3 mM, the concentration of urea is 6 mM - 12 mM, and the concentration of ammonium fluoride is 2 mM - 6 mM.

3. The preparation method of the cobalt-based carbon nanotube film according to claim 1, characterized in that, in S1, the hydrothermal temperature is 120°C - 160°C, and the time is 2 h - 6 h.

4. The preparation method of the cobalt-based carbon nanotube film according to claim 1, characterized in that, in S1, the substrate includes carbon cloth CC, carbon paper CFP, and stainless steel wire mesh SS.

5. The preparation method of the cobalt-based carbon nanotube film according to claim 1, characterized in that, the CVD reaction temperature is 700°C - 900°C, and the reaction time is 1 h - 3 h.

Images