A method for preparing a carbon nanotube material with a loaded alloy core-shell structure

Abstract

The present invention discloses a method for preparing a carbon nanotube material with an alloy core-shell structure. The method comprises the following steps: slowly adding a methanol solution of sodium citrate and a nickel salt to a methanol solution of potassium ferricyanide to react and obtain an iron-nickel Prussian blue analog (FeNi-PBA); then self-polymerizing aniline on the surface of the FeNi-PBA to form a polyaniline-coated FeNi-PBA precursor, FeNi-PBA@PANI; and grinding and uniformly mixing the precursor powder with dicyandiamide, followed by pyrolysis under an inert atmosphere to obtain the carbon nanotube material with an alloy core-shell structure. By adjusting the ratio of FeNi-PBA to polyaniline and the ratio of FeNi-PBA to dicyandiamide, the present invention produces an electrocatalyst with excellent bifunctional catalytic activity for oxygen reduction and oxygen evolution, which can be used as a cathode catalyst in zinc-air batteries. The preparation method of the present invention has the advantages of abundant raw materials, a mature production process, simple operation, controllable specific surface area, and high yield, and is expected to achieve large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc-air battery materials, and particularly relates to a method for preparing a carbon nanotube material with a loaded alloy core-shell structure. Background Art

[0002] Due to the non-renewable nature of fossil fuels and the environmental pollution associated with their use, the development of renewable clean energy has become a hot research area. Energy collection, storage, and conversion are key issues that need to be addressed in the development of renewable energy. Zinc-air batteries (Zn-air batteries) are attracting increasing attention in energy storage due to their abundant zinc reserves, extremely high theoretical energy density and specific capacity, high safety, and low cost. The rates of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) occurring at the cathode of Zn-air batteries during charge and discharge are key factors affecting their efficiency. Therefore, cathode materials must be able to catalyze both OER and ORR effectively. In existing research, platinum-based catalysts are generally considered to exhibit the best catalytic performance for ORR, while iridium or ruthenium nanoparticles are the best catalysts for OER. However, their high cost and poor stability limit their application in rechargeable Zn-air batteries. Therefore, the development of inexpensive, stable, and efficient bifunctional ORR / OER catalysts for the cathode reactions in Zn-air batteries is crucial.

[0003] In existing studies, people have found that Fe has a great effect on the ORR performance of zinc-air batteries, while Ni has a greater impact on the OER performance of zinc-air batteries. Therefore, in some existing technologies, Fe-Ni bimetallic catalysts are used to catalyze the cathode reaction of zinc-air batteries. For example, the patent document with application number CN201910351282.2 discloses the preparation of nickel-iron alloy / nitrogen-doped carbon electrocatalysts and their application in rechargeable zinc-air batteries. The preparation method of the nickel-iron alloy / nitrogen-doped carbon electrocatalyst is as follows: first, a certain amount of nickel nitrate hexahydrate, ferric nitrate nonahydrate, terephthalic acid, triethylenediamine and g-C3N4 are successively added to dimethylformamide to react to obtain a precursor, and then the solvent is evaporated and the remaining solid is annealed in atmosphere to obtain Ni x Fe y / NC bimetallic electrocatalyst. This technical solution uses nitrogen-doped carbon materials as carriers, attaching NiFe alloy particles to the surface of the nitrogen-doped carbon materials to improve the catalytic performance of the NiFe alloy. In this technical solution, during the high-temperature carbonization of the precursor, the chemical bonds between the metal elements and other elements break, which easily leads to metal agglomeration and excessive growth, thereby reducing the ratio of active sites of the nanoparticles and limiting further improvement of the performance of this type of catalyst. In addition, during the continuous charging and discharging process, the electrode material may undergo morphological changes, causing the NiFe alloy particles attached to the surface of the nitrogen-doped carbon material to fall off, affecting the battery's service life. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a carbon nanotube material with a loaded alloy core-shell structure. The carbon nanotube material prepared by this method has good dispersion of metal nanoparticles and excellent ORR / OER dual catalytic function.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a carbon nanotube material with an alloy core-shell structure comprises the following steps:

[0007] (1) Preparation of FeNi-PBA: Sodium citrate and nickel salt are dissolved in water to obtain solution A; hexacyanoferrate is dissolved in water to obtain solution B; solution A and solution B are mixed and reacted, and then the solid product is separated to obtain FeNi-PBA;

[0008] (2) Preparation of FeNi-PBA@PANI: FeNi-PBA and surfactant prepared in step (1) were added to deionized water, stirred and dispersed, and aniline and polymerization initiator were added to allow aniline to undergo polymerization reaction on the surface of FeNi-PBA to generate polyaniline and coat FeNi-PBA. The solid product was then separated to obtain FeNi-PBA@PANI.

[0009] (3) Preparation of FeNi@NC: The FeNi-PBA@PANI prepared in step (2) is placed in a heating furnace and subjected to high-temperature pyrolysis under the conditions of adding carbon source material and nitrogen source material to obtain FeNi@NC, i.e., a carbon nanotube material with an alloy core-shell structure.

[0010] Prussian blue analogue (PBA) is a type of coordination compound formed by transition metal ions and cyanide. 2+ With Fe(CN)6 4- FeNi-PBA bimetallic precursor was prepared, and Fe 2+ and Ni 2+A stable bond is formed, and then a surfactant is used to make the FeNi-PBA precursor form dispersed particles in water, and aniline monomer and an initiator that can initiate the polymerization of aniline monomer are added thereto. Under the induction of the FeNi-PBA precursor and the surfactant, the aniline monomer polymerizes on the surface of the FeNi-PBA precursor particles to form a high molecular polymer. As the polymerization reaction proceeds, the high molecular polymer wraps the FeNi-PBA precursor to form a core-shell structure to obtain FeNi-PBA@PANI. Finally, the FeNi-PBA@PANI is placed in a tubular furnace and supplemented with carbon source materials and nitrogen source materials for high-temperature pyrolysis. During the high-temperature pyrolysis process, cyanide gas formed by the decomposition of Prussian blue analogues will reduce metal ions to form bimetallic nanoparticles and provide a small amount of carbon source and nitrogen source. Under the catalysis of the bimetallic nanoparticles, the supplemented carbon source material and nitrogen source material will grow with the bimetallic nanoparticles as the base point to form a nitrogen-doped carbon nanotube structure. In some embodiments, the carbon source material and the nitrogen source material can be two substances that can provide carbon elements and nitrogen elements respectively. For example, the carbon source material can be an alkane and the nitrogen source material can be nitrogen. In other embodiments, the carbon source material and the nitrogen source material can be a substance that can provide both carbon elements and nitrogen elements, such as urea, g-C3N4, etc. In the prior art, when using Prussian blue analogues to prepare carbon nanotube materials, the Prussian blue analogues are usually mixed with materials such as urea and pyrolyzed at high temperature, or alkanes and nitrogen are introduced while the Prussian blue analogues are pyrolyzed at high temperature. During the implementation of the above method, if the Prussian blue analogues decompose too quickly under high temperature conditions, it is easy to cause the formed nano-metal particles to agglomerate before being coated with carbon nanotubes, resulting in a decrease in the active site ratio. The present invention adopts the core-shell structure of FeNi-PBA@PANI to avoid the occurrence of this problem to a certain extent. On the one hand, the polyaniline coating layer itself can separate the FeNi-PBA particles; on the other hand, during the high-temperature pyrolysis process, the decomposition of polyaniline itself will provide a certain amount of carbon and nitrogen sources. Since the carbon and nitrogen sources provided by polyaniline are formed around the metal nanoparticles, they can induce the growth of carbon nanotubes on the outer layer of the metal nanoparticles, avoiding the agglomeration of the metal nanoparticles before being coated with carbon nanotubes.

[0011] Furthermore, the carbon source and nitrogen source materials are both dicyandiamide.

[0012] Furthermore, the nickel salt in step (1) is nickel nitrate, and the hexacyanoferrate is potassium ferrocyanide.

[0013] Furthermore, the polymerization initiator in step (2) includes a water-soluble initiator and an organic protonic acid.

[0014] Furthermore, the water-soluble initiator is ammonium persulfate, and the organic protonic acid is phytic acid.

[0015] Furthermore, the molar ratio of potassium ferrocyanide to nickel nitrate hexahydrate in step (1) is 1:(1.5-2.5).

[0016] Furthermore, the molar ratio of FeNi-PBA to polymer monomer aniline in step (2) is (2.75-9.64):1.

[0017] Furthermore, in step (2), the molar ratio of aniline to surfactant is 1:(0.4-0.6), and the molar ratio of aniline to oxidant is 1:1.

[0018] Furthermore, the mass ratio of FeNi-PBA@PANI to dicyandiamide described in step (3) is 1:(10~80).

[0019] Furthermore, the temperature of the high-temperature pyrolysis in step (3) is 500-800°C, and the heating rate is 2-5°C / min.

[0020] Another object of the present invention is to provide a carbon nanotube material with an alloy core-shell structure obtained by the above-mentioned preparation method. The carbon nanotube material comprises at least an end structure formed by FeNi alloy particles and a tail structure formed by nitrogen-doped carbon nanotubes that coats the FeNi alloy particles and extends from the FeNi alloy particles.

[0021] In summary, the application of the present invention can achieve the following beneficial effects:

[0022] (1) The present invention uses Prussian blue analogues as precursors. Prussian blue analogues have high specific surface area and crystallinity, rich functional groups and special structural stability, which can obtain stable Fe 2+ and Ni 2+ , and Prussian blue analogues can simultaneously provide carbon source, nitrogen source and evenly distributed metal source, making it easy to prepare FeNi nanoalloy particles with uniform particle size and good dispersion and induce the growth of carbon nanotubes.

[0023] (2) In the present invention, a polyaniline coating layer is formed on the surface of FeNi-PBA through a polymerization reaction. The polyaniline coating layer is conducive to the dispersion of nano-alloy particles formed by FeNi-PBA, and can provide a carbon source and a nitrogen source during the high-temperature cracking process to induce the growth of carbon nanotubes and reduce the agglomeration of nano-alloy particles.

[0024] (3) The present invention uses dicyandiamide as a supplementary material for carbon and nitrogen sources. Dicyandiamide is cheap and readily available, and the raw materials are widespread. Using dicyandiamide as an auxiliary carbon and nitrogen source has a simple production method and low equipment requirements. Compared with the method of using alkanes and nitrogen as carbon and nitrogen sources, the operation is simpler.

[0025] (4) The carbon nanotube material prepared by the present invention comprises at least an end structure formed by FeNi alloy particles and a tail structure formed by nitrogen-doped carbon nanotubes that coat the FeNi alloy particles and extend from the FeNi alloy particles. Since the FeNi alloy particles are in a coated state, the structure has strong stability during charge and discharge. Nitrogen doping on the carbon nanotubes can allow electrolyte ions to enter the carbon inner layer from the carbon outer layer, thereby activating the carbon material and improving the electron transport characteristics and electrochemical reactivity of the carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the transmission electron microscopy characterization result of FeNi@NC prepared in Example 1;

[0027] Figure 2 is the nitrogen adsorption-desorption isotherm of FeNi@NC prepared in Example 1;

[0028] Figure 3 The cyclic voltammetry test results of FeNi@NC prepared in Example 1 under saturated O2 and saturated Ar respectively;

[0029] Figure 4 The ORR performance comparison test results of FeNi@NCx and 40% Pt / C prepared in Examples 1 to 5 are shown;

[0030] Figure 5 The OER performance comparison test results of FeNi@NCx and 40% IrO2 prepared in Examples 1 to 5 are shown;

[0031] Figure 6 The ORR performance comparison test results of FeNi@NCy and 40% Pt / C prepared in Examples 6 to 10 are shown;

[0032] Figure 7 The OER performance comparison test results of FeNi@NCy and 40% IrO2 prepared in Examples 6 to 10;

[0033] Figure 8 Graph showing the ORR performance comparison test results of FeNi@NCT and 40% Pt / C prepared in Example 1 and Example 11;

[0034] Figure 9 This is a comparison test result of the OER performance of FeNi@NCT and 40% IrO2 prepared in Example 1 and Example 11. DETAILED DESCRIPTION

[0035] The present invention is further described below through examples and drawings.

[0036] Example 1

[0037] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0038] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0039] Step 2:

[0040] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0041] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:45, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0042] The alloy-loaded core-shell carbon nanotube material obtained in this example is denoted as FeNi@NCx (x=4.82).

[0043] Example 2

[0044] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0045] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0046] Step 2:

[0047] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 9.64:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 19.3 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0048] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:45, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0049] The carbon nanotube material with an alloy core-shell structure obtained in this example is denoted as FeNi@NCx (x=9.64).

[0050] Example 3

[0051] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0052] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0053] Step 2:

[0054] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 3.86:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 48.25 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0055] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:45, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0056] The carbon nanotube material with an alloy core-shell structure obtained in this example is denoted as FeNi@NCx (x=3.86).

[0057] Example 4

[0058] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0059] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0060] Step 2:

[0061] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 3.21:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 57.9 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0062] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:45, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0063] The carbon nanotube material with an alloy core-shell structure obtained in this example is denoted as FeNi@NCx (x=3.21).

[0064] Example 5

[0065] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0066] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0067] Step 2:

[0068] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 2.75:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 67.55 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0069] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:45, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0070] The carbon nanotube material with an alloy core-shell structure obtained in this example is denoted as FeNi@NCx (x=2.75).

[0071] Combine Figure 4 It can be seen that in the ORR test experiment, when the molar ratio of FeNi-PBA to aniline monomer increases from 2.75 to 9.64, the ORR reaction rate does not change significantly, but the onset potential fluctuates greatly. The onset potential is the largest when the molar ratio is 3.86 and 4.82. Figure 5It can be seen that in the OER test experiment, when the molar ratio increases from 2.75 to 3.86, the catalytic performance decreases and is lower than the test results of the IrO2 catalyst. When the molar ratio increases from 3.86 to 4.82, the catalytic performance improves and is close to the test results of the IrO2 catalyst. When the molar ratio increases from 4.82 to 9.64, the catalytic performance decreases.

[0072] comprehensive Figure 4 and Figure 5 It can be seen that when the molar ratio of FeNi-PBA to aniline monomer changes, the ORR catalytic performance and OER catalytic performance of the catalyst change in roughly the same way. When the molar ratio of FeNi-PBA to aniline monomer is 4.82, better ORR catalytic performance and OER catalytic performance can be obtained at the same time. Therefore, in Examples 1 to 5, the optimal molar ratio x of FeNi-PBA to aniline monomer is 4.82:1.

[0073] Example 6

[0074] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0075] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0076] Step 2:

[0077] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0078] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:10, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0079] The alloy-loaded core-shell carbon nanotube material obtained in this example is denoted as FeNi@NCy (y=10).

[0080] Example 7

[0081] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0082] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0083] Step 2:

[0084] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0085] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:20, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0086] The alloy-loaded core-shell carbon nanotube material obtained in this example is denoted as FeNi@NCy (y=20).

[0087] Example 8

[0088] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0089] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0090] Step 2:

[0091] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0092] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:30, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0093] The carbon nanotube material with an alloy core-shell structure obtained in this example is denoted as FeNi@NCy (y=30).

[0094] Example 9

[0095] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0096] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0097] Step 2:

[0098] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0099] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:60, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0100] The alloy-loaded core-shell carbon nanotube material obtained in this example is denoted as FeNi@NCy (y=60).

[0101] Example 10

[0102] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0103] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0104] Step 2:

[0105] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0106] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:80, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 700°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0107] The carbon nanotube material with an alloy core-shell structure obtained in this example is denoted as FeNi@NCy (y=80).

[0108] It should be noted that the FeNi@NC-45 in the figure refers to the catalyst prepared in Example 1. Figure 6 and Figure 7 It can be seen that in the ORR performance test experiment and the OER performance test experiment, when the mass ratio of dicyandiamide to FeNi-PBA@PANI increases from 10 to 80, the ORR catalytic performance and OER catalytic performance of the catalyst fluctuate. Figure 6 It can be seen that when the mass ratio of dicyandiamide increases, the ORR reaction rate increases, but dicyandiamide has little effect on the reaction rate when it exceeds a certain mass ratio. As the mass ratio of dicyandiamide increases, the size of the onset potential fluctuates significantly. Among them, FeNi@NC-45, that is, when the mass ratio of dicyandiamide to FeNi-PBA@PANI is 45, has the largest onset potential, so FeNi@NC-45 has the best ORR catalytic effect. Figure 7 As can be seen from the results, the OER reaction rate fluctuates with the increase in the mass ratio of dicyandiamide. The OER catalytic performance of FeNi@NC-45 is closest to the test results of the IrO2 catalyst. Therefore, in general, when the mass ratio y of dicyandiamide to FeNi-PBA@PANI is 45:1, the catalyst has the best ORR and OER dual catalytic performance.

[0109] Example 11

[0110] This embodiment provides a method for preparing a carbon nanotube material with an alloy core-shell structure, which specifically includes the following steps:

[0111] Step 1: Add sodium citrate dihydrate and nickel nitrate hexahydrate to deionized water and stir evenly to form solution A. The concentration of nickel nitrate hexahydrate in solution A is 30 mmol / L, and the concentration of sodium citrate is 45 mmol / L. Then, add potassium ferrocyanide to the deionized water and mix evenly to form solution B. The concentration of potassium ferrocyanide in solution B is 40 mmol / L. Solution B is slowly added to solution A. The molar ratio of potassium ferrocyanide to nickel nitrate is 1:1.5. Stir at a constant speed for 24 hours. Centrifuge the product and dry it to obtain FeNi-PBA material;

[0112] Step 2:

[0113] Sodium dodecylbenzenesulfonate and the FeNi-PBA prepared in step 1 were added to deionized water and ultrasonically stirred for 4 hours to obtain a dispersion, wherein the concentration of FeNi-PBA in the dispersion was 4.168 mol / L, and aniline monomer, phytic acid and ammonium persulfate were added to obtain a reaction solution, wherein the molar ratio of sodium dodecylbenzenesulfonate to aniline monomer was 0.5:1, the molar ratio of FeNi-PBA to aniline monomer was 4.82:1, the ratio of ammonium persulfate to aniline monomer was 1:1, the concentration of phytic acid was 0.5 mol / L, and the concentration of aniline monomer was 38.6 mol / L. After the reaction was completed, the reaction solution was centrifuged to separate the product at a centrifuge speed of 10000 rpm for 5 min, and the FeNi-PBA@PANI precursor powder was obtained after drying;

[0114] Step 3: Grind and mix FeNi-PBA@PANI and dicyandiamide in a mass ratio of 1:45, and then place them in a tubular furnace and pyrolyze them at high temperature under an inert atmosphere to obtain FeNi@NC, that is, a carbon nanotube material with an alloy core-shell structure; the heating rate during the high-temperature pyrolysis process is 5°C / min, after heating at 500°C for 2h, the temperature is increased to 800°C and heated for another 2h, and the flow rate of the inert gas nitrogen is 100ml / min.

[0115] The alloy-loaded core-shell carbon nanotube material obtained in this example is denoted as FeNi@NCT (T=800).

[0116] It should be noted that Figure 8 and Figure 9 The FeNi@NC-700 in the table refers to the catalyst prepared in Example 1. Figure 6 We can see that with the increase of pyrolysis temperature, the onset potential of ORR performance increases, but the reaction rate decreases. Figure 7 We can see that its OER performance decreases sharply with the increase of pyrolysis temperature, so the most suitable pyrolysis temperature is 700℃.

[0117] The specific embodiments described herein are merely illustrative of the spirit of the present invention and are not intended to limit the present invention. Modifications to the technical solutions described in the aforementioned embodiments, or equivalent substitutions of some of the technical features, or other similar works, do not depart from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for preparing a carbon nanotube material with an alloy core-shell structure, characterized in that: The following steps are involved: (1) Preparation of FeNi-PBA: Sodium citrate and nickel salt are dissolved in water to obtain solution A; hexacyanoferrate is dissolved in water to obtain solution B; solution A and solution B are mixed and reacted, and then the solid product is separated to obtain FeNi-PBA; (2) Preparation of FeNi-PBA@PANI: FeNi-PBA and surfactant prepared in step (1) were added to deionized water, stirred and dispersed, and aniline and polymerization initiator were added to allow aniline to undergo polymerization reaction on the surface of FeNi-PBA to generate polyaniline and coat FeNi-PBA. The solid product was then separated to obtain FeNi-PBA@PANI; the molar ratio of FeNi-PBA to aniline monomer was (3.86-9.64):1; (3) Preparation of FeNi@NC: The FeNi-PBA@PANI prepared in step (2) is placed in a heating furnace and subjected to high-temperature pyrolysis at 500-800°C under the condition of adding dicyandiamide to obtain FeNi@NC, i.e., a carbon nanotube material with an alloy core-shell structure; the mass ratio of FeNi-PBA@PANI to dicyandiamide is 1:(30-60); the carbon nanotube material at least comprises an end structure formed by FeNi alloy particles and a tail structure formed by nitrogen-doped carbon nanotubes that coat the FeNi alloy particles and extend from the FeNi alloy particles.

2. The method for preparing a carbon nanotube material with an alloy core-shell structure according to claim 1, characterized in that: The nickel salt described in step (1) is nickel nitrate, and the hexacyanoferrate is potassium ferrocyanide.

3. The method for preparing a carbon nanotube material with an alloy core-shell structure according to claim 2, characterized in that: The molar ratio of potassium ferrocyanide to nickel nitrate in step (1) is 1:(1.5-2.5).

4. The method for preparing a carbon nanotube material with an alloy core-shell structure according to claim 1, characterized in that: The polymerization initiator in step (2) includes a water-soluble initiator and an organic protonic acid.

5. The method for preparing a carbon nanotube material with an alloy core-shell structure according to claim 4, characterized in that: The water-soluble initiator is ammonium persulfate, and the organic protonic acid is phytic acid.

6. The method for preparing a carbon nanotube material with an alloy core-shell structure according to claim 1, characterized in that: In step (2), the molar ratio of aniline to surfactant is 1:(0.4-0.6), and the molar ratio of aniline to initiator is 1:

1.

7. The method for preparing a carbon nanotube material with an alloy core-shell structure according to claim 1, characterized in that: The heating rate of the high-temperature pyrolysis in step (3) is 2-5°C / min.

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