Highly graphitized carbon tube grid of scaffold-like structure as well as preparation method and application of highly graphitized carbon tube grid

Abstract

The invention belongs to the technical field of carbon nanomaterials, and particularly relates to a highly graphitized carbon tube grid of a scaffold-like structure and a preparation method and application of the highly graphitized carbon tube grid. The preparation method comprises the following steps: taking aluminum oxide with interconnected pore channels inside as a template, and obtaining a three-dimensional interconnected nickel nanorod grid film through an electro-deposition method; by utilizing the catalytic graphitization property of metal nickel and regulating and controlling parameters of acetylene when the acetylene is decomposed on the surface of the metal nickel, the problem that three-dimensional highly-graphitized carbon with controllable morphology and size cannot be synthesized due to nickel deformation caused by a catalytic mechanism is solved, and the highly-graphitized carbon tube grid with a scaffold-like structure is obtained; and the crystallinity of the carbon tube grid film is effectively improved at a relatively low temperature. The preparation process is simple, feasible and environment-friendly, and equipment is low in cost and common. A smooth ion transport channel provided by the vertical carbon tube array and a rapid electron conduction network provided by the highly graphitized interconnected carbon tube structure are expected to be used in the fields of alternating current filtering, high power output and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon nanomaterials, and particularly relates to a highly graphitized carbon tube grid with a scaffolding-like structure, a preparation method thereof, and uses thereof. Background Art

[0002] Three-dimensional carbon tube mesh membranes, with vertical carbon tubes interconnected by lateral carbon tubes, effectively prevent agglomeration between adjacent vertical carbon tubes. They possess high structural stability and an effective open-pore structure, providing fast ion transport channels and promising applications in electrochemical capacitors with high power output and linear filtering. However, the fast frequency response of electrochemical capacitors requires not only fast ion transport but also fast electron conduction. Three-dimensional carbon tube mesh membranes, prepared using three-dimensional porous alumina as a template and chemical vapor deposition (CVD), exhibit poor crystallinity and slow electron conduction, even when deposited at ultra-high temperatures of 1000°C. To achieve the desired frequency response, the thickness of the CTU mesh membrane (the height of the vertical CTUs) must be sacrificed, but this results in a reduction in the device's specific capacitance and energy density. Therefore, it is crucial to improve the conductivity of these interconnected 3D CTU mesh membranes to achieve fast frequency response and high power while increasing electrode loading and capacity.

[0003] Graphite is the most thermodynamically stable allotrope of carbon under standard conditions. 2Graphite forms covalent bonds in a triangular hybridized manner and is arranged in a hexagonal pattern. This unique structure gives graphite excellent electrical conductivity and chemical stability. Numerous experiments have demonstrated that increasing the degree of graphitization can effectively improve the electrical conductivity of carbon materials. Transition metal nickel has the property of catalyzing graphitization, which can increase the degree of graphitization of carbon materials at relatively low temperatures. However, the mechanism of nickel-catalyzed growth of graphitic carbon is as follows: at a certain temperature, hydrocarbon compounds first pyrolyze on the nickel surface to form a Ni-C alloy. Due to the free energy difference between amorphous carbon and graphitic carbon, as the Ni-C alloy on the nickel surface reaches a supersaturated state, the dissolved carbon precipitates on the nickel surface in the form of graphitic carbon. Density functional theory (DFT) predicts that the C-Ni bond energy is greater than the energy consumed by the formation of the Ni-C interface steps. Therefore, the diffusion of nickel atoms along the interface to the free surface is energetically favorable and may ultimately lead to their reshaping onto nickel particles, preventing the precipitated graphitic carbon from growing along the original nickel surface, making the graphitic carbon morphology difficult to control. Although there are documents on the preparation of graphitized carbon tubes by catalysis of nickel nanowires, the morphology and size of the obtained carbon tubes are not fully controllable, and there are problems such as breakage and deformation. Although this has little effect on one-dimensional structures, it is fatal for three-dimensional structures. Deformation will cause the three-dimensional framework to collapse and the original morphology cannot be maintained. Therefore, existing work has remained on the preparation of one-dimensional graphitized carbon tubes, and graphitized carbon tubes with three-dimensional structures with controllable morphology and size have not yet been achieved. How to controllably synthesize highly graphitized carbon tubes and interconnect them to form a highly graphitized carbon tube network with a scaffold-like structure is a huge challenge. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a method for preparing a scaffold-like highly graphitized carbon tube grid. This preparation method uses alumina with interconnected pores as a template to obtain a three-dimensional interconnected nickel nanorod grid film by electrodeposition. By utilizing the catalytic graphitization properties of metallic nickel and regulating the temperature, pressure, time, gas flow rate, etc. during the decomposition of acetylene on its surface, the problem of nickel deformation caused by the catalytic mechanism, which leads to the inability to synthesize three-dimensional highly graphitized carbon with controllable morphology and size, is overcome. A scaffold-like highly graphitized carbon tube grid with chemically connected lateral graphitized carbon tubes and adjacent upright graphitized carbon tubes is obtained, effectively improving the crystallinity of the carbon tube grid film at relatively low temperatures. The preparation process is simple, feasible, environmentally friendly, and requires inexpensive and common equipment. The smooth ion transport channels provided by the upright carbon tube array and the fast electron conduction network provided by the highly graphitized interconnected carbon tube structure make it promising for applications in fields such as AC filtering and high power output.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a highly graphitized carbon tube grid with a scaffold-like structure, comprising the following steps:

[0006] S1. Using a three-dimensional porous alumina with interconnected pores as a template, depositing metallic nickel nanorods within the interconnected pores by electrodeposition. The deposited nickel nanorods can accurately replicate the morphology of the internal pores of the three-dimensional porous alumina, forming a three-dimensional interconnected nickel nanorod mesh membrane with the alumina template;

[0007] S2. Using a selective chemical etching method, all components except metallic nickel are removed, and the upright nickel nanorods are connected to the lateral nickel nanorods to form a scaffold-like, three-dimensionally interconnected nickel nanorod mesh membrane;

[0008] S3. Decomposing acetylene by chemical vapor deposition and utilizing the catalytic graphitization property of metallic nickel to deposit a layer of graphitized carbon tubes on the surface of the nickel nanorod mesh film, thereby obtaining a scaffold-like, three-dimensionally interconnected highly graphitized carbon tube / nickel nanorod mesh film composite material;

[0009] S4. The nickel nanorod mesh film in the highly graphitized carbon tube / nickel nanorod mesh film composite material is removed by a selective chemical etching method to obtain a highly graphitized carbon tube mesh with a scaffold-like structure.

[0010] Further improvements in the preparation method of highly graphitized carbon tube grids as scaffold-like structures:

[0011] Preferably, the preparation method of the three-dimensional porous alumina with interconnected pores inside is as follows: at a DC constant voltage of 0-5°C and 185-195V, an aluminum sheet containing trace iron, silicon, and copper impurities is used as an anode and graphite is used as a cathode, and they are immersed in an anodic oxidation electrolyte for 8-48 hours, and then the anodic oxidation voltage is gradually reduced to 45-60V within 1-3 hours and then taken out, the aluminum content of the aluminum sheet is 99.5-99.8wt%, and the total impurity content is ≤0.5wt%; then vacuum immersed in a phosphoric acid solution with a temperature of 35-45°C and a concentration of 5-10wt% for 30-60min, and after rinsing with deionized water, a three-dimensional porous alumina with interconnected pores can be obtained, with residual aluminum due to no anodic oxidation.

[0012] Preferably, the anodic oxidation electrolyte is a mixed solution prepared by adding phosphoric acid and ethanol to deionized water, wherein the concentration of phosphoric acid is 0.25-0.35 mol / L and anhydrous ethanol accounts for 1 / 10 of the total volume of the mixed solution.

[0013] Preferably, the specific steps of step S1 of electro-depositing metal nickel nanorods are as follows: a high-purity nickel sheet with a nickel content of ≥99.99% is used as an anode, and a three-dimensional porous alumina with interconnected pores inside with aluminum remaining due to no anodic oxidation is used as a cathode, and the cathode and the anode are immersed in an electro-deposition solution at the same time, wherein the solvent of the electro-deposition solution is deionized water, the concentration of nickel sulfate is 0.1-0.15 mol / L, the concentration of nickel chloride is 0.1-0.15 mol / L, and the concentration of boric acid is 0.5 mol / L, and the current density is first 1-4 mA / cm 2 The deposition was carried out under a constant current of 10 min, and then the current density was 0.2-1 mA / cm 2 Deposition under constant current for 5-30h.

[0014] Preferably, in the selective chemical etching method of step S2, the etching liquid used is a saturated SnCl4 solution and a 1-3 mol / LNaOH solution; in the selective chemical etching method of step S4, a 1-3 mol / L hydrochloric acid solution is used to remove the nickel nanorod mesh membrane in the highly graphitized carbon tube / nickel nanorod mesh membrane composite material at 30-60°C.

[0015] Preferably, in step S3, acetylene is decomposed by chemical vapor deposition, and the catalytic graphitization properties of metallic nickel are utilized to deposit a layer of graphitized carbon tubes on the surface of the nickel nanorod grid membrane. The specific steps are as follows: the nickel nanorod grid membrane is clamped with a carbon layer-covered copper foam and placed in a porcelain boat with openings at both ends, which is placed in a high-temperature tube furnace. After heating to 550-650°C at a rate of 5°C / min at a pressure of -0.1MPa to -0.08MPa, in an H2 / Ar mixed atmosphere containing 10% H2 and a gas flow rate of 50-100sccm, C2H2 is introduced at a flow rate of 2-20sccm for 10s-10min, and then cooled to room temperature in a normal pressure Ar atmosphere and a gas flow rate of 30-80sccm, and the surface is cleaned by plasma.

[0016] A second object of the present invention is to provide a highly graphitized carbon tube grid with a scaffold-like structure obtained by the method for preparing a highly graphitized carbon tube grid with a scaffold-like structure as described in any one of the above.

[0017] A third object of the present invention is to provide an application of the above-mentioned scaffold-like structure of highly graphitized carbon tube grid in electrochemical capacitors.

[0018] The application of the highly graphitized carbon tube grid as the scaffold-like structure in electrochemical capacitors is further improved:

[0019] Preferably, the scaffold-like highly graphitized carbon tube grid is cut into two pieces of equal area and placed on a metal Pt sheet current collector as symmetrical electrodes, isolated by a diaphragm, injected with electrolyte and then packaged to obtain an electrochemical capacitor device.

[0020] Preferably, the electrolyte is a 0.8-1.2 mol / L aqueous sulfuric acid solution, packaged in a PET film.

[0021] The beneficial effects of the present invention compared to the prior art are:

[0022] (1) The present invention provides a method for preparing a highly graphitized carbon tube grid with a scaffold-like structure. The present invention uses porous anodic aluminum oxide with three-dimensional interconnected pores as a template, and the three-dimensional porous aluminum oxide has aluminum remaining due to the lack of anodic oxidation; first, a method of electroplating is used to deposit metal nickel nanorods under the confinement induction of the template pores, and the deposited nickel nanorods can accurately replicate the morphology of the internal pores of the three-dimensional porous aluminum oxide, forming a three-dimensional interconnected nickel nanorod grid membrane with an aluminum oxide template; then, a selective chemical etching method is used to remove other components except the metal nickel (the aluminum remaining due to the lack of anodic oxidation and the three-dimensional porous aluminum oxide with interconnected pores), to obtain a three-dimensional interconnected nickel nanorod grid membrane with a scaffold-like structure composed of upright nickel nanorods and lateral nickel nanorods connected to each other; wherein a saturated SnCl4 solution is used to etch and remove the aluminum remaining due to the lack of anodic oxidation, and a 1-3 mol / L NaOH solution is used to etch and remove the three-dimensional porous aluminum oxide with interconnected pores. Then, at relatively low temperatures, the catalytic graphitization properties of nickel are exploited to manipulate the temperature, pressure, time, and gas flow rate during the decomposition of acetylene on the surface to produce a composite material consisting of a three-dimensional interconnected, highly graphitized carbon tube / nickel nanorod mesh with a scaffolding-like structure. Finally, the three-dimensional interconnected nickel nanorod mesh membrane is removed by selective chemical etching to obtain a scaffolding-like, highly graphitized carbon tube mesh. This preparation method is simple, feasible, environmentally friendly, requires inexpensive and readily available equipment, and offers a low production cost.

[0023] (2) The present invention provides a highly graphitized carbon nanotube grid with a scaffold-like structure. The carbon nanotube grid has a scaffold-like structure, with horizontal carbon nanotubes chemically connected between vertical carbon nanotubes. The height and diameter of the carbon nanotubes can both be adjusted, and both the vertical carbon nanotubes and the horizontal carbon nanotubes are highly graphitized. The horizontal carbon nanotubes can effectively prevent agglomeration between adjacent vertical carbon nanotubes, enabling smooth ion migration channels to be provided both inside the vertical carbon nanotubes and in the gaps between adjacent carbon nanotubes; the integrated scaffold-like structure composed of highly graphitized carbon nanotubes chemically connected is a fast electron conduction network, effectively improving the conductivity of the electrode material. Therefore, using this highly graphitized carbon nanotube grid with a scaffold-like structure as the electrode of an electrochemical capacitor can improve the response speed and power performance of the device, and has important application value in the field of electrochemical capacitors with high power output and linear filtering.

[0024] (3) The highly graphitized carbon nanotube grid with a scaffold-like structure provided by the present invention can be used as the electrode of a fast frequency (<kHz) response electrochemical capacitor. The electrochemical capacitor assembled from it has an area specific capacitance as high as 2.34 mF / cm at a frequency of 120 Hz. 2 , and the phase angle is -81.7°; at a high scan rate of 500 V / s, the cyclic voltammetry curve can still maintain a nearly rectangular shape, and at a large current density of 500 mA / cm 2 , the galvanostatic charge-discharge curve shows an ideal isosceles triangle; it exhibits good electrochemical performance and the potential as a fast response supercapacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the preparation process of the highly graphitized carbon nanotube grid with a scaffold-like structure according to the present invention.

[0026] Figure 2 is the structural characterization of Example 1, Comparative Example 1 and Comparative Example 2. Among them Figure 2 (a) is a cross-sectional scanning electron microscope (SEM) image of the highly graphitized carbon nanotube grid with a scaffold-like structure (3D-GCTs); Figure 2 (b) is a transmission electron microscope (TEM) image of 3D-GCTs; Figure 2 (c) is a high-resolution transmission electron microscope (HRTEM) image of 3D-GCTs; Figure 2 (d) is an HRTEM image of a three-dimensional self-supporting carbon nanotube grid film (3D-CTs) obtained using alumina as a template; Figure 2 (e) is a cross-sectional SEM image of the sample obtained after chemical vapor deposition outside the scope of this invention; Figure 2 (f) is a TEM image of the sample obtained after chemical vapor deposition outside the scope of this invention.

[0027] Figure 3(a) X-ray diffraction (XRD) patterns of 3D-GCTs and 3D-CTs; Figure 3 (b) Raman spectra of 3D-GCTs and 3D-CTs.

[0028] Figure 4 This is the electrochemical performance test of Example 2. Figure 4 (a) and Figure 4 (b) Cyclic voltammetry (CV) curves of the electrochemical capacitor assembled with 3D-GCTs at scan rates from 100 mV / s to 500 V / s. Figure 4 (c) and Figure 4 (d) Electrochemical capacitor assembled with 3D-GCTs at a current density of 0.2 mA / cm 2 Up to 500mA / cm 2 Constant current charge and discharge (GCD) curve.

[0029] Figure 5 The Bode plot (a), Nyquist curve (b), and area specific capacitance and frequency relationship curve (c) obtained from the electrochemical impedance spectroscopy (EIS) of Example 2. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] First, buy from the market or make it yourself:

[0032] Chemicals and instruments used in the anodizing process: aluminum sheets containing trace impurities, wherein the aluminum content is 99.5-99.8wt%, and the impurities include iron, silicon, and copper, and the total impurity content is ≤0.5wt%; phosphoric acid; ethanol; graphite; oxidation tank; DC power supply; cold stage;

[0033] Chemicals and instruments used in the electrodeposition process: high-purity nickel sheets; nickel sulfate; nickel chloride; boric acid; electrodeposition tank; DC power supply;

[0034] Chemicals and instruments used in the chemical vapor deposition process: acetylene; hydrogen-argon mixture; argon; high-temperature tube furnace; quartz tube; porcelain boat; vacuum pump;

[0035] Other chemicals and instruments used in the process of preparing highly graphitized carbon tube grids with scaffold-like structures: tin tetrachloride; sodium hydroxide; hydrochloric acid; plasma cleaning machine.

[0036] The present invention discloses a highly graphitized carbon tube grid with a scaffolding-like structure and a preparation method and use thereof, comprising the following steps:

[0037] An aluminum sheet containing impurities including iron, silicon and copper with a total impurity content of ≤0.5wt% and an aluminum content of 99.5-99.8wt% is used as an anode and graphite is used as a cathode. The aluminum sheet is immersed in an anodic oxidation electrolyte with a solvent of deionized water, a phosphoric acid concentration of 0.25-0.35 mol / L and anhydrous ethanol accounting for 1 / 10 of the total volume of the mixed solution. The aluminum sheet is anodic oxidized at 0-5°C and a DC constant voltage of 185-195V for 8-48 hours. The anodic oxidation voltage is then gradually reduced to 45-60V within 1-3 hours, the aluminum sheet is taken out, vacuum-evacuated and immersed in a phosphoric acid solution with a temperature of 35-45°C and a concentration of 5-10wt% for 30-60 minutes, and rinsed with deionized water to obtain a three-dimensional porous aluminum oxide with interconnected pores inside and residual aluminum due to non-anodization.

[0038] A high-purity nickel sheet with a nickel content of ≥99.99% is used as the anode, and a three-dimensional porous alumina with interconnected pores inside with residual aluminum due to no anodic oxidation is used as the cathode. The cathode and anode are simultaneously immersed in an electrodeposition solution with a nickel sulfate concentration of 0.1-0.15 mol / L, a nickel chloride concentration of 0.1-0.15 mol / L, and a boric acid concentration of 0.5 mol / L, in which the solvent is deionized water. The current density is first 1-4 mA / cm 2 The deposition was carried out under a constant current of 10 min, and then the current density was 0.2-1 mA / cm 2 The nickel nanorods were deposited under a constant current of 5-30 h to form a three-dimensional interconnected nickel nanorod mesh film with an aluminum oxide template.

[0039] A selective chemical etching method was used, using a saturated SnCl4 solution to remove the remaining aluminum due to the lack of anodic oxidation; a 1-3 mol / L NaOH solution was used to remove the three-dimensional porous alumina with interconnected pores inside, obtaining a three-dimensional interconnected nickel nanorod grid membrane with a scaffolding-like structure composed of upright nickel nanorods and lateral nickel nanorods connected to each other.

[0040] Acetylene is decomposed by chemical vapor deposition, and the catalytic graphitization property of metallic nickel is utilized to deposit a layer of graphitized carbon tubes on the surface of the nickel nanorod grid membrane. The specific steps are as follows: the nickel nanorod grid membrane is clamped with a carbon layer-covered copper foam and placed in a porcelain boat with two ends opened, which is then placed in a high-temperature tube furnace. The mixture is heated to 550-650°C at a rate of 5°C / min in an H2 / Ar mixed atmosphere containing 10% H2 at a pressure of -0.1MPa to -0.08MPa and a gas flow rate of 50-100sccm. C2H2 is then introduced at a flow rate of 2-20sccm for 10s-10min. The mixture is then cooled to room temperature in an atmospheric pressure Ar atmosphere and a gas flow rate of 30-80sccm. The surface is then cleaned with plasma to obtain a scaffold-like structured, three-dimensionally interconnected, highly graphitized carbon tube / nickel nanorod grid membrane composite material.

[0041] A 1-3 mol / L hydrochloric acid solution is used to selectively chemically etch and remove the three-dimensional interconnected nickel nanorod grid film at 30-60° C. to obtain a highly graphitized carbon tube grid with a scaffold-like structure.

[0042] The highly graphitized carbon tube grid of this type of scaffolding structure is cut into two pieces of equal area and placed on a metal Pt sheet current collector as symmetrical electrodes. After isolation with a diaphragm, 0.8-1.2 mol / L sulfuric acid aqueous electrolyte is injected and then encapsulated with PET film to obtain an electrochemical capacitor device.

[0043] Example 1

[0044] This embodiment provides a method for preparing a highly graphitized carbon tube grid with a scaffold-like structure. The preparation process is as follows: Figure 1 As shown, the specific steps include:

[0045] (1) An aluminum sheet containing impurities including iron, silicon, and copper with a total impurity content of ≤0.5wt% and an aluminum content of 99.5-99.8wt% is used as an anode, and graphite is used as a cathode. The cathode and the anode are immersed in an anodic oxidation electrolyte; the anodic oxidation electrolyte is a mixed solution prepared by adding phosphoric acid and ethanol to deionized water, wherein the phosphoric acid concentration is 0.3mol / L and anhydrous ethanol accounts for 1 / 10 of the total volume of the mixed solution; anodizing for 32 hours at a DC constant voltage of 190V at 3°C, then gradually reducing the anodic oxidation voltage to 55V within 2 hours, taking it out, and then vacuum-immersing it in a phosphoric acid solution with a temperature of 40°C and a concentration of 5wt% for 47 minutes. After rinsing with deionized water, a three-dimensional porous alumina with interconnected pores can be obtained, with residual aluminum due to no anodization.

[0046] A high-purity nickel sheet with a nickel content of ≥99.99% was used as the anode, and a three-dimensional porous alumina with interconnected pores inside was used as the cathode. The cathode and anode were immersed in the electrodeposition solution. The current density was first 1.67 mA / cm 2 The deposition was carried out under a constant current of 10 min and then at a current density of 0.67 mA / cm 2 The electrodeposition solution is a mixed solution obtained by adding nickel sulfate, nickel chloride and boric acid to deionized water, wherein the concentration of nickel sulfate is 0.15 mol / L, the concentration of nickel chloride is 0.15 mol / L, and the concentration of boric acid is 0.5 mol / L.

[0047] (2) Using a selective chemical etching method, the three-dimensional interconnected nickel nanorod mesh membrane with an alumina template was immersed in a saturated SnCl4 solution to remove the remaining aluminum due to the lack of anodic oxidation; it was then immersed in a 3 mol / L NaOH solution to remove the three-dimensional porous alumina with interconnected pores inside. The upright nickel nanorods and the lateral nickel nanorods were interconnected to form a scaffold-like structure and a three-dimensional interconnected nickel nanorod mesh membrane.

[0048] (3) Under -0.1 MPa, utilizing the catalytic graphitization properties of nickel, the nickel nanorod mesh membrane was pressed with a layer of carbon-covered copper foam and placed in a H2 / Ar mixed atmosphere (70 sccm) containing 10% H2. After heating to 640°C at a rate of 5°C / min, C2H2 was introduced at a flow rate of 20 sccm for 1 min. After the reaction, the membrane was cooled to room temperature under a normal pressure Ar atmosphere (50 sccm), and its surface was plasma cleaned to obtain a scaffold-like structure, three-dimensionally interconnected highly graphitized carbon tube / nickel nanorod mesh membrane composite material;

[0049] (4) The highly graphitized carbon tube / nickel nanorod mesh membrane composite material was immersed in a 3 mol / L hydrochloric acid solution, and the three-dimensional interconnected nickel nanorod mesh membrane was selectively chemically corroded and removed at 60°C to obtain a highly graphitized carbon tube mesh with a scaffold-like structure.

[0050] Example 2

[0051] This embodiment uses a scaffold-like structure of highly graphitized carbon tube grids to prepare an electrochemical capacitor, specifically comprising the following steps:

[0052] (1) Cut the highly graphitized carbon tube grid of the scaffold-like structure prepared in Example 1 into pieces with an area of 0.09 cm 2 and place them on a metal Pt sheet current collector as symmetrical electrodes;

[0053] (2) After isolating the two symmetrical electrodes with a water-based diaphragm, inject 1 mol / L sulfuric acid aqueous electrolyte;

[0054] (3) The assembled capacitor is encapsulated using PET film to produce an electrochemical capacitor device.

[0055] Example 3

[0056] This embodiment provides a method for preparing a highly graphitized carbon tube grid with a scaffold-like structure. The preparation process is as follows: Figure 1 As shown, the specific steps include:

[0057] (1) An aluminum sheet containing impurities including iron, silicon, and copper with a total impurity content of ≤0.5wt% and an aluminum content of 99.5-99.8wt% is used as an anode, and graphite is used as a cathode. The cathode and the anode are immersed in an electrolyte; the electrolyte is a mixed solution prepared by adding phosphoric acid and ethanol to deionized water, wherein the phosphoric acid concentration is 0.3mol / L and anhydrous ethanol accounts for 1 / 10 of the total volume of the mixed solution; anodization is carried out at a DC constant voltage of 3°C and 190V for 24 hours, and then the anodization voltage is gradually reduced to 50V within 2 hours. The aluminum sheet is taken out and vacuum-immersed in a phosphoric acid solution with a temperature of 40°C and a concentration of 5wt% for 50 minutes. After rinsing with deionized water, a three-dimensional porous alumina with interconnected pores is obtained, with residual aluminum due to no anodization.

[0058] A high-purity nickel sheet with a nickel content of ≥99.99% is used as the anode, and a three-dimensional porous alumina with interconnected pores inside is used as the cathode. The cathode and anode are immersed in the electrodeposition solution. The current density is 1 mA / cm 2 The deposition was carried out under a constant current of 10 min and then at a current density of 0.67 mA / cm 2 The electrodeposition solution is a mixed solution obtained by adding nickel sulfate, nickel chloride and boric acid to deionized water, wherein the concentration of nickel sulfate is 0.15 mol / L, the concentration of nickel chloride is 0.15 mol / L, and the concentration of boric acid is 0.5 mol / L.

[0059] (2) Using a selective chemical etching method, the three-dimensional interconnected nickel nanorod mesh membrane with an alumina template was immersed in a saturated SnCl4 solution to remove the remaining aluminum due to the lack of anodic oxidation; it was then immersed in a 3 mol / L NaOH solution to remove the three-dimensional porous alumina with interconnected pores inside. The upright nickel nanorods and the lateral nickel nanorods were interconnected to form a scaffold-like structure and a three-dimensional interconnected nickel nanorod mesh membrane.

[0060] (3) Under -0.1 MPa, utilizing the catalytic graphitization properties of nickel, the nickel nanorod mesh membrane was pressed with a carbon-covered copper foam and placed in a H2 / Ar mixed atmosphere (75 sccm) containing 10% H2. After heating to 600°C at a rate of 5°C / min, C2H2 was introduced at a flow rate of 4 sccm for 4 min. After cooling to room temperature under a normal pressure Ar atmosphere (50 sccm), the surface was plasma cleaned to obtain a scaffold-like structure, three-dimensionally interconnected highly graphitized carbon tube / nickel nanorod mesh membrane composite material;

[0061] (4) The highly graphitized carbon tube / nickel nanorod mesh membrane composite material was immersed in a 3 mol / L hydrochloric acid solution, and the three-dimensional interconnected nickel nanorod mesh membrane was selectively chemically corroded and removed at 60°C to obtain a highly graphitized carbon tube mesh with a scaffold-like structure.

[0062] Example 4

[0063] This embodiment uses the highly graphitized carbon tube grid with a scaffold-like structure prepared in Example 3 to prepare an electrochemical capacitor, specifically comprising the following steps:

[0064] (1) Cut the scaffold-like highly graphitized carbon tube grid prepared in Example 3 into two pieces of equal area, and place them on a metal Pt sheet current collector as symmetrical electrodes;

[0065] (2) After isolating the two symmetrical electrodes with a water-based diaphragm, a 0.8 mol / L aqueous sulfuric acid solution was injected as the electrolyte;

[0066] (3) The assembled capacitor is encapsulated using PET film to produce an electrochemical capacitor device.

[0067] Example 5

[0068] This embodiment provides a method for preparing a highly graphitized carbon tube grid with a scaffold-like structure. The preparation process is as follows: Figure 1 As shown, the specific steps include:

[0069] (1) An aluminum sheet containing impurities including iron, silicon, and copper with a total impurity content of ≤0.5wt% and an aluminum content of 99.5-99.8wt% is used as an anode, and graphite is used as a cathode. The cathode and the anode are immersed in an electrolyte; the electrolyte is a mixed solution prepared by adding phosphoric acid and ethanol to deionized water, wherein the phosphoric acid concentration is 0.3mol / L and anhydrous ethanol accounts for 1 / 10 of the total volume of the mixed solution; anodization is carried out at a DC constant voltage of 3°C and 190V for 11 hours, and then the anodization voltage is gradually reduced to 50V within 2 hours. After being taken out, it is immersed in a phosphoric acid solution with a temperature of 40°C and a concentration of 5wt% for 35 minutes. After being rinsed with deionized water, a three-dimensional porous alumina with interconnected pores is obtained, with residual aluminum due to no anodization.

[0070] A high-purity nickel sheet was used as the anode and a three-dimensional porous alumina with interconnected pores inside was used as the cathode. The cathode and anode were immersed in the electrodeposition solution. The current density was 1.67 mA / cm 2 The deposition was carried out under a constant current of 10 min, and then the current density was 0.5 mA / cm 2 The electrodeposition solution is a mixed solution obtained by adding nickel sulfate, nickel chloride and boric acid to deionized water, wherein the concentration of nickel sulfate is 0.15 mol / L, the concentration of nickel chloride is 0.15 mol / L, and the concentration of boric acid is 0.5 mol / L.

[0071] (2) Using a selective chemical etching method, the three-dimensional interconnected nickel nanorod mesh membrane with an alumina template was immersed in a saturated SnCl4 solution to remove the remaining aluminum due to the lack of anodic oxidation; it was then immersed in a 3 mol / L NaOH solution to remove the three-dimensional porous alumina with interconnected pores inside. The upright nickel nanorods and the lateral nickel nanorods were interconnected to form a scaffold-like structure and a three-dimensional interconnected nickel nanorod mesh membrane.

[0072] (3) Under -0.1 MPa, utilizing the catalytic graphitization properties of nickel, the nickel nanorod mesh membrane was pressed with a carbon-covered copper foam and placed in a H2 / Ar mixed atmosphere (70 sccm) containing 10% H2. After heating to 620°C at a rate of 5°C / min, C2H2 was introduced at a flow rate of 4 sccm for 1 min. After cooling to room temperature under a normal pressure Ar atmosphere (50 sccm), the surface was plasma cleaned to obtain a scaffold-like structure, three-dimensionally interconnected highly graphitized carbon tube / nickel nanorod mesh membrane composite material;

[0073] (4) The highly graphitized carbon tube / nickel nanorod mesh membrane composite material was immersed in a 3 mol / L hydrochloric acid solution, and the three-dimensional interconnected nickel nanorod mesh membrane was selectively chemically corroded and removed at 60°C to obtain a highly graphitized carbon tube mesh with a scaffold-like structure.

[0074] Example 6

[0075] This example uses the highly graphitized carbon tube grid with a scaffold-like structure prepared in Example 5 to prepare an electrochemical capacitor, specifically comprising the following steps:

[0076] (1) Cut the scaffold-like highly graphitized carbon tube grid prepared in Example 5 into two pieces of equal area, and place them on a metal Pt sheet current collector as symmetrical electrodes;

[0077] (2) After isolating the two symmetrical electrodes with a water-based diaphragm, a 1.2 mol / L aqueous sulfuric acid solution was injected as the electrolyte;

[0078] (3) The assembled capacitor is encapsulated using PET film to produce an electrochemical capacitor device.

[0079] Comparative Example 1

[0080] This comparative example provides a method for preparing a three-dimensional carbon tube grid film composed of non-graphitized carbon tubes obtained using aluminum oxide as a template, which specifically includes the following steps:

[0081] (1) An aluminum sheet containing impurities including iron, silicon, and copper with a total impurity content of ≤0.5wt% and an aluminum content of 99.5-99.8wt% is used as an anode, and graphite is used as a cathode. The cathode and anode are immersed in an anodic oxidation electrolyte; the anodic oxidation electrolyte is a mixed solution prepared by adding phosphoric acid and ethanol to deionized water, wherein the phosphoric acid concentration is 0.3mol / L and anhydrous ethanol accounts for 1 / 10 of the total volume of the mixed solution; anodizing for 10 hours at a DC constant voltage of 190V at 3°C, then placing it in a saturated SnCl4 solution to corrode the remaining aluminum due to non-anodization, washing it with deionized water, and then immersing it in a phosphoric acid solution at a temperature of 40°C and a concentration of 5wt% for 20 minutes, thereby obtaining a three-dimensional porous alumina with interconnected pores inside and no residual aluminum.

[0082] (2) The three-dimensional porous alumina template with interconnected channels was placed in a high-temperature tube furnace and heated to 650°C at a rate of 5°C / min under an Ar atmosphere of 50 sccm at normal pressure. Subsequently, C2H2 with a flow rate of 10 sccm was introduced for 90 minutes. The C2H2 gas was turned off, and the sample was cooled to room temperature under an Ar atmosphere of 50 sccm. The sample surface was plasma cleaned to obtain a three-dimensional carbon tube grid film with an alumina template.

[0083] (3) The three-dimensional carbon tube mesh film with an alumina template is placed in a 3 mol / L NaOH solution, the alumina template is chemically corroded, and then rinsed and dried to obtain a three-dimensional carbon tube mesh film composed of non-graphitized carbon tubes with an alumina template.

[0084] (4) An electrochemical capacitor was prepared according to the steps of Example 2.

[0085] Comparative Example 2

[0086] This comparative example provides a product and preparation process obtained by pyrolyzing acetylene on the surface of a three-dimensional interconnected nickel nanorod mesh film to catalyze graphitization of carbon tubes, where the growth conditions are not within the scope of the present invention, and specifically includes the following steps:

[0087] (1) preparing a three-dimensional interconnected nickel nanorod mesh film having a scaffold-like structure by referring to steps (1) and (2) of Example 1;

[0088] (2) Under -0.1 MPa, utilizing the catalytic graphitization properties of nickel, the nickel nanorod mesh membrane was placed in a H2 / Ar mixed atmosphere (70 sccm) containing 10% H2, heated to 640°C at a rate of 5°C / min, and then C2H2 was introduced at a flow rate of 4 sccm for 25 minutes. After the end, it was cooled to room temperature under a normal pressure Ar atmosphere (50 sccm) and its surface was plasma cleaned to obtain a scaffold-like structure, three-dimensionally interconnected highly graphitized carbon tube / nickel nanorod mesh membrane composite material;

[0089] (3) The composite material was immersed in a 3 mol / L hydrochloric acid solution, and the three-dimensional interconnected nickel nanorod grid film was selectively removed by chemical etching at 60° C. to obtain the final product.

[0090] (4) An electrochemical capacitor was prepared according to the steps of Example 2.

[0091] Figure 2 The structural characteristics of Example 1, Comparative Example 1 and Comparative Example 2 are shown. Figure 2 (a) is a cross-sectional scanning electron microscope (SEM) image of Example 1; Figure 2 (b) is a transmission electron microscope (TEM) image of Example 1; Figure 2 (c) is a high-resolution transmission electron microscopy (HRTEM) image of Example 1; Figure 2 (d) is the HRTEM image of Comparative Example 1; Figure 2 (e) is a cross-sectional SEM image of Comparative Example 2; Figure 2 (f) is a TEM image of Comparative Example 2. Cross-sectional SEM of Example 1 Figure 2 (a) TEM Figure 2 (b) and HRTEM Figure 2(c) It can be seen that the vertical carbon tubes in this embodiment are chemically connected to the horizontal carbon tubes, there is no agglomeration between the carbon tubes, there are obvious and clear lattice diffraction stripes on the carbon tube wall, and the interplanar spacing is consistent with the (002) plane of graphite, which shows that the carbon tubes obtained by this parameter are highly graphitized. This method can realize an integrated self-supporting highly graphitized carbon tube grid (3D-GCTs) with a scaffold-like structure. In comparison, the HRTEM of Comparative Example 1 shows that the carbon tubes are highly graphitized. Figure 2 (d) shows no lattice fringes, indicating a disordered state, indicating that the three-dimensional self-supporting carbon tube mesh film (3D-CTs) obtained using alumina as a template is non-graphitized; In addition, according to the cross-sectional SEM of Comparative Example 2 Figure 2 (e) and TEM Figure 2 (f) It can be seen that the sample obtained by this parameter did not form a scaffold-like carbon tube grid, and the carbon tubes were severely deformed.

[0092] Figure 3 (a) is the X-ray diffraction (XRD) spectra of Example 1 and Comparative Example 1; Figure 3 (b) is the Raman spectrum of Example 1 and Comparative Example 1. Figure 3 (a) and Figure 3 (b) The graphitic carbon nature of the carbon tube mesh film obtained with three-dimensional interconnected nickel nanorods as the substrate was further confirmed, while the carbon tube mesh film obtained with alumina as the template corresponded to amorphous carbon. Figure 3 The strong, sharp XRD peak at 26.4° in Example 1 (a) is attributed to the (002) plane of graphite, indicating a high degree of graphitization. The XRD pattern of Comparative Example 2 shows no sharp peaks typical of crystalline graphite, but only a single large peak whose width and position are consistent with amorphous carbon. Figure 3 (b) In the Raman spectrum of Example 1, there is a -1 The sharp G band at the center and at 2703cm -1 The strong 2D band near the G peak and the 2D peak are both characteristic peaks of graphite. D / I G This further confirms its highly ordered graphitic carbon nature. In contrast, the Raman spectrum of Comparative Example 1 contains two broad G peaks and D peaks, with no 2D peak observed, corresponding to amorphous carbon.

[0093] Figure 4 The electrochemical performance test of Example 2, wherein Figure 4 (a) and Figure 4 (b) Cyclic voltammetry (CV) curves of the electrochemical capacitor assembled with 3D-GCTs as electrodes at a scan rate of 100 mV / s to 500 V / s. Figure 4 (c) and Figure 4(d) Electrochemical capacitor assembled with 3D-GCTs as electrodes at a current density of 0.2 mA / cm 2 Up to 500mA / cm 2 The specific test steps are as follows: the electrochemical capacitor assembled according to Example 2 is connected to the CHI760E electrochemical workstation of Shanghai Chenhua, and the CV-Cyclic Voltammetry is selected to obtain the CV curve of the sample. The specific parameters are set as follows: Init E (V), Low E (V) and Final E (V) are all 0, High E (V) is 1V, and Scan Rate (V / s) are 0.1, 0.2, 0.5, 100, 200, and 500 respectively; CP-Chronopotentiometry is selected to obtain the GCD curve of the sample, and the specific parameters are set as follows: Cathodic Current (A) and Anodic Current (A) are both 1.8*10 -5 , 4.5*10 -5 、9*10 -5 、9*10 -3 , 1.8*10 -2 , 4.5*10 -2 , High E Limit (V) is 1, Low E Limit (V) is 0, High E Hold Time (sec) and Low E Hold time (sec) are both 0, Current Switching Priority is Potential. Figure 3 It can be seen that the CV curves of the electrochemical capacitor assembled with 3D-GCTs as electrodes are close to rectangular at scan rates from 100 mV / s to 500 V / s, and the CV curves are close to rectangular at 0.2 mA / cm 2 Up to 500mA / cm 2 The GCD curve under current density is an ideal isosceles triangle, showing nearly ideal double-layer capacitance characteristics.

[0094] Figure 5 The Bode plot (a), Nyquist plot (b), and area specific capacitance vs. frequency curve (c) obtained from the electrochemical impedance spectroscopy (EIS) of Example 2 are shown in the following figure. The specific test steps are as follows: the electrochemical capacitor assembled according to Example 2 is connected to a Zahzer Zennium electrochemical workstation, and EIS is selected to test the frequency-related performance of the sample. The specific parameters are set as follows: VOLTAGE is 0, upper limit is 100KHz, lower limit is 100mHz, and AMPLITUDE is 5mV. Figure 4It can be seen that the phase angle of the electrochemical capacitor assembled with 3D-GCTs as electrodes is close to -90° in the low-frequency region; at a frequency of 120 Hz, the area specific capacitance is as high as 2.34 mF / cm 2 , the phase angle is -81.7°; in the Nyquist plot, the imaginary resistance is almost perpendicular to the real axis, and the equivalent series resistance is <0.5Ω; the above results all indicate that the electrochemical capacitor assembled by 3D-GCTs has a high area-specific capacitance and fast frequency response capability.

[0095] In summary, the present invention discloses a highly graphitized carbon tube grid with a scaffolding-like structure, and a preparation method and use thereof. The carbon tube grid is a scaffolding-like structure, and the upright carbon tubes are chemically connected by transverse carbon tubes. The height and diameter of the carbon tubes can be controlled, and both the upright carbon tubes and the transverse carbon tubes are highly graphitized. The transverse carbon tubes can effectively prevent the agglomeration between adjacent upright carbon tubes, so that the interior of the upright carbon tubes and the gaps between adjacent carbon tubes can provide smooth ion migration channels; the integrated scaffolding-like structure composed of chemically connected highly graphitized carbon tubes is a fast electron conduction network, which effectively improves the conductivity of the electrode material. Therefore, using the highly graphitized carbon tube grid with this type of scaffolding structure as an electrode of an electrochemical capacitor can improve the response speed and power performance of the device, and has important application value in the field of electrochemical capacitors with high power output and linear filtering. The preparation method comprises the following steps: using a three-dimensional porous alumina having interconnected pores as a template, first electrodepositing metallic nickel nanorods under the confinement of the template pores by electrodeposition, wherein the deposited nickel nanorods can accurately replicate the morphology of the internal pores of the three-dimensional porous alumina; then, using a selective chemical etching method to remove all components except the metallic nickel, a three-dimensional interconnected nickel nanorod mesh membrane with a scaffold-like structure consisting of vertical nickel nanorods and horizontal nickel nanorods interconnected is obtained; then, at a relatively low temperature, utilizing the catalytic graphitization properties of metallic nickel, by regulating the temperature, pressure, time, gas flow rate, etc. during the decomposition of acetylene on its surface, a composite material of a three-dimensional interconnected highly graphitized carbon tube / nickel nanorod mesh with a scaffold-like structure is obtained; after removing the nickel nanorods, a self-supporting highly graphitized carbon tube mesh with a scaffold-like structure is obtained, in which the horizontal graphitized carbon tubes chemically connect adjacent vertical graphitized carbon tubes. The preparation method adopted by the present invention is simple, feasible, environmentally friendly, has low-cost and common equipment, and has low product preparation cost.

[0096] Although some specific embodiments of the present invention have been described in detail through examples, it should be understood by those skilled in the art that the examples described above are only preferred embodiments of the present invention, rather than all embodiments. Those skilled in the art of the art to which the present invention belongs may make many variations and improvements to the specific embodiments described, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. It should be understood by those skilled in the art that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a highly graphitized carbon tube grid with a scaffold-like structure, characterized in that The following steps are involved: S1. Using a three-dimensional porous alumina with interconnected pores as a template, depositing metallic nickel nanorods within the interconnected pores by electrodeposition. The deposited nickel nanorods can accurately replicate the morphology of the internal pores of the three-dimensional porous alumina, forming a three-dimensional interconnected nickel nanorod mesh membrane with the alumina template; S2. Using a selective chemical etching method, all components except metallic nickel are removed, and the upright nickel nanorods are connected to the lateral nickel nanorods to form a scaffold-like, three-dimensionally interconnected nickel nanorod mesh membrane; S3. Decomposing acetylene by chemical vapor deposition and utilizing the catalytic graphitization property of metallic nickel to deposit a layer of graphitized carbon tubes on the surface of the nickel nanorod mesh film, thereby obtaining a scaffold-like, three-dimensionally interconnected highly graphitized carbon tube / nickel nanorod mesh film composite material; S4. The nickel nanorod mesh film in the highly graphitized carbon tube / nickel nanorod mesh film composite material is removed by a selective chemical etching method to obtain a highly graphitized carbon tube mesh with a scaffold-like structure.

2. The method for preparing a scaffold-like highly graphitized carbon tube grid according to claim 1, characterized in that: The preparation method of the three-dimensional porous alumina with interconnected pores is as follows: at a DC constant voltage of 185-195V and a temperature of 0-5°C, an aluminum sheet containing trace iron, silicon, and copper impurities is used as an anode and graphite is used as a cathode, and they are immersed in an anodic oxidation electrolyte for 8-48 hours. Then, the anodic oxidation voltage is gradually reduced to 45-60V within 1-3 hours and the aluminum sheet is removed. The aluminum content of the aluminum sheet is 99.5-99.8wt%, and the total impurity content is ≤0.5wt%. The aluminum sheet is then vacuum-immersed in a phosphoric acid solution with a temperature of 35-45°C and a concentration of 5-10wt% for 30-60 minutes. After rinsing with deionized water, the three-dimensional porous alumina with interconnected pores can be obtained, with residual aluminum due to no anodic oxidation.

3. The method for preparing a scaffold-like highly graphitized carbon tube grid according to claim 2, characterized in that: The anodic oxidation electrolyte is a mixed solution prepared by adding phosphoric acid and ethanol to deionized water, wherein the concentration of phosphoric acid is 0.25-0.35 mol / L, and anhydrous ethanol accounts for 1 / 10 of the total volume of the mixed solution.

4. The method for preparing a scaffold-like highly graphitized carbon tube grid according to claim 1 or 2, characterized in that: The specific steps of step S1 are as follows: a high-purity nickel sheet with a nickel content of ≥99.99% is used as an anode, and a three-dimensional porous alumina with interconnected pores inside with aluminum remaining due to non-anodization is used as a cathode. The cathode and anode are simultaneously immersed in an electrodeposition solution, wherein the solvent of the electrodeposition solution is deionized water, a nickel sulfate concentration of 0.1-0.15 mol / L, a nickel chloride concentration of 0.1-0.15 mol / L, and a boric acid concentration of 0.5 mol / L. The current density is first 1-4 mA / cm 2 The deposition was carried out under a constant current of 10 min, and then the current density was 0.2-1 mA / cm 2 Deposition under constant current for 5-30h.

5. The method for preparing a scaffold-like highly graphitized carbon tube grid according to claim 1, characterized in that: In the selective chemical etching method of step S2, the etching solutions used are saturated SnCl4 solution and 1-3 mol / L NaOH solution; in the selective chemical etching method of step S4, 1-3 mol / L hydrochloric acid solution is used to remove the nickel nanorod mesh membrane in the highly graphitized carbon tube / nickel nanorod mesh membrane composite material at 30-60°C.

6. The method for preparing a scaffold-like highly graphitized carbon tube grid according to claim 1 or 2, characterized in that: In step S3, acetylene is decomposed by chemical vapor deposition, and a layer of graphitized carbon tubes is deposited on the surface of the nickel nanorod grid membrane by utilizing the catalytic graphitization properties of metallic nickel. The specific steps are as follows: the nickel nanorod grid membrane is clamped with a carbon layer-covered copper foam and placed in a porcelain boat with openings at both ends, which is placed in a high-temperature tube furnace. After heating to 550-650°C at a rate of 5°C / min in a H2 / Ar mixed atmosphere containing 10% H2 at a pressure of -0.1MPa to -0.08MPa and a gas flow rate of 50-100sccm, C2H2 is introduced at a flow rate of 2-20sccm for 10s-10min, and then cooled to room temperature in a normal pressure Ar atmosphere and a gas flow rate of 30-80sccm, and the surface is cleaned by plasma.

7. A highly graphitized carbon tube grid with a scaffold-like structure obtained by the method for preparing a highly graphitized carbon tube grid with a scaffold-like structure according to any one of claims 1 to 6.

8. Use of the highly graphitized carbon tube grid with a scaffold-like structure according to claim 7 in an electrochemical capacitor.

9. The use of the scaffold-like highly graphitized carbon tube grid in an electrochemical capacitor according to claim 8, characterized in that: The highly graphitized carbon tube grid with a scaffold-like structure is cut into two pieces of equal area and placed on a metal Pt sheet current collector as symmetrical electrodes. After isolation with a diaphragm, an electrolyte is injected and then packaged to obtain an electrochemical capacitor device.

10. Application of the scaffold-like highly graphitized carbon tube grid in an electrochemical capacitor according to claim 9, characterized in that: The electrolyte is a 0.8-1.2 mol / L sulfuric acid aqueous solution and is packaged in a PET film.

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