Nitrogen atom doped two-dimensional carbon material with controllable interlayer spacing as well as preparation method and application of nitrogen atom doped two-dimensional carbon material

Abstract

The invention discloses a nitrogen atom-doped two-dimensional carbon material with controllable interlayer spacing as well as a preparation method and application thereof, and belongs to the field of bromine-based flow batteries. The nitrogen atom-doped two-dimensional carbon material with the controllable interlayer spacing comprises a layered inorganic salt template and a nitrogen-containing substance, the nitrogen-containing substance is intercalated or complexed between the layered inorganic salt templates; the layered inorganic salt template contains a pore structure. The prepared electrode material has the beneficial characteristics of controllable morphology, simple preparation method, low cost, high catalytic activity, good stability and the like. The prepared electrode material improves the catalytic activity of the electrode, inhibits diffusion of bromine, and effectively improves the efficiency and service life of the bromine-based flow battery.

Description

Technical Field

[0001] The present application relates to a nitrogen-doped two-dimensional carbon material with controllable layer spacing, a preparation method thereof, and an application thereof, belonging to the field of bromine-based flow batteries. Background Art

[0002] To achieve the global energy transformation and the dual-carbon goals, new energy power generation technologies such as wind energy and solar energy have developed rapidly. In the context of the energy Internet, large-scale energy storage technologies can be matched with renewable energy to overcome their disadvantages of intermittency and volatility, which is one of the keys to realizing the large-scale application of renewable energy. The flow battery technology has received attention in the field of large-scale energy storage technologies due to its advantages such as high safety, independently designable power and capacity, and environmental friendliness. Among them, the bromine-based flow battery has low cost and high energy density, and has broad application prospects in the field of user-side energy storage. The zinc-bromine flow battery has developed rapidly and has been in the commercial demonstration stage, but the bromine-based flow battery still faces many common challenges: the catalytic activity of the bromine electrode pair is low, and the reaction kinetics does not match the negative electrode; bromine has strong volatility, which causes environmental problems and at the same time leads to the loss of active substances, reducing the performance and service life of the battery; bromine diffuses to the negative electrode and chemically reacts with the active substances on the negative electrode side, resulting in self-discharge of the battery.

[0003] Two-dimensional carbon materials have advantages such as good electrical conductivity, high surface area, high chemical / electrochemical activity and durability, rich active sites, and adjustable heteroatom doping, and are widely used in the fields of catalysis and electrochemical energy storage. For two-dimensional porous carbon materials with controllable morphology and large specific surface area, developing simpler and more effective preparation schemes is still a major challenge. Summary of the Invention

[0004] According to one aspect of the present application, there is provided a nitrogen-doped two-dimensional carbon material with controllable layer spacing, which has a regular two-dimensional layered structure, the nitrogen element content and layer spacing can be regulated, has high catalytic activity for bromine, and at the same time captures bromine and polybromides in the layered porous structure by means of the size effect. When used as the positive electrode material of a bromine-based flow battery, it can significantly improve the battery efficiency and inhibit self-discharge.

[0005] The nitrogen-doped two-dimensional carbon material with controllable layer spacing described in the present application includes: a layered inorganic salt template and a nitrogen-containing substance;

[0006] The nitrogen-containing substance is intercalated or complexed between the layered inorganic salt templates;

[0007] The layered inorganic salt template has a pore structure.

[0008] Optionally, the layered inorganic salt template is selected from any one or more of ferric chloride, zinc nitrate, and magnesium hydroxy silicate.

[0009] Optionally, the nitrogen-doped two-dimensional carbon material has a regular two-dimensional layered structure.

[0010] Optionally, the interlayer spacing of the nitrogen-doped two-dimensional carbon material is Preferably, the interlayer spacing of the nitrogen-doped two-dimensional carbon material is Preferably, the interlayer spacing of the nitrogen-doped two-dimensional carbon material is

[0011] Optionally, the interlayer spacing of the nitrogen-doped two-dimensional carbon material is independently selected from any value in or the range value between any two of the above.

[0012] Optionally, the specific surface area of the nitrogen-doped two-dimensional carbon material is 200 - 1500 m 2 / g; preferably, the specific surface area of the nitrogen-doped two-dimensional carbon material is 400 - 1000 m 2 / g; more preferably, the specific surface area of the nitrogen-doped two-dimensional carbon material is 600 - 1000 m 2 / g.

[0013] Optionally, the specific surface area of the nitrogen-doped two-dimensional carbon material is independently selected from 200 m 2 / g, 205 m 2 / g, 210 m 2 / g, 300 m 2 / g, 400 m 2 / g, 500 m 2 / g, 600 m 2 / g, 650 m 2 / g, 700 m 2 / g, 800 m 2 / g, 850 m 2 / g, 900 m 2 / g, 950 m 2 / g, 1000 m 2 / g, 1500 m 2 / g or the range value between any two of the above.

[0014] Optionally, the nitrogen content of the nitrogen-doped two-dimensional carbon material is 5 - 50%; preferably, the nitrogen content of the nitrogen-doped two-dimensional carbon material is 20 - 50%; more preferably, the nitrogen content of the nitrogen-doped two-dimensional carbon material is 30 - 50%.

[0015] Optionally, the nitrogen content of the nitrogen-doped two-dimensional carbon material is independently selected from any value of 5%, 10%, 20%, 30%, 35%, 40%, 45%, 50% or the range value between any two of the above.

[0016] Optionally, the forms of nitrogen atom existence in the nitrogen-containing substance include any one or more of pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen, and oxidized nitrogen. Preferably, the forms of nitrogen atom existence in the nitrogen-containing substance include pyridine nitrogen and graphitic nitrogen.

[0017] Optionally, in the nitrogen-containing substance, graphitic nitrogen accounts for 30 - 70%; preferably, in the nitrogen-containing substance, graphitic nitrogen accounts for 40 - 60%.

[0018] Optionally, in the nitrogen-containing substance, pyridine nitrogen accounts for 10 - 30%; preferably, in the nitrogen-containing substance, pyridine nitrogen accounts for 12 - 25%.

[0019] In another aspect of the present application, a preparation method of the nitrogen-doped two-dimensional carbon material is provided, including: mixing a layered inorganic salt template raw material and a nitrogen-containing organic precursor, grinding, performing heat treatment under an inert gas, cooling to obtain a black product, subjecting the black product to acid treatment, washing with water, centrifuging, and drying to obtain the nitrogen-doped two-dimensional carbon material.

[0020] Optionally, the layered inorganic salt template raw material is selected from any one or more of ferric chloride hexahydrate, zinc nitrate hexahydrate, and magnesium hydroxy silicate;

[0021] Preferably, the nitrogen-containing organic precursor is selected from any one or more of dopamine hydrochloride, aniline, methylamine, and ethylenediamine.

[0022] Optionally, the inert gas is nitrogen or argon.

[0023] Optionally, when performing acid treatment, the acid used is hydrochloric acid or sulfuric acid.

[0024] Optionally, the molar ratio of the layered inorganic salt template raw material to the nitrogen-containing organic precursor is 1:14 - 5:1; preferably, the molar ratio of the layered inorganic salt template raw material to the nitrogen-containing organic precursor is 1:10 - 3:1.

[0025] Optionally, the molar ratio of the layered inorganic salt template raw material to the nitrogen-containing organic precursor is independently selected from any value of 5:1, 3:1, 2:1, 1:1, 1:2, 1:5, 1:10, 1:14 or the range value between any two of the above.

[0026] Optionally, the concentration of the acid is 0.1 - 2M; preferably, the concentration of the acid is 0.5 - 1M.

[0027] Optionally, the temperature of the heat treatment is 200-900°C. Preferably, the temperature of the heat treatment is 300-600°C.

[0028] Optionally, the temperature of the heat treatment is independently selected from any value of 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or a range value between any two of the above.

[0029] Optionally, the time of the heat treatment is 1-6h. Preferably, the time of the heat treatment is 2-4h.

[0030] Optionally, the time of the heat treatment is independently selected from any value of 1h, 2h, 3h, 4h, 5h, 6h or a range value between any two of the above.

[0031] Optionally, during the heat treatment, the gas flow rate of the inert gas is 10-100 ml / min. Preferably, during the heat treatment, the gas flow rate of the inert gas is 20-60 ml / min.

[0032] Optionally, during the heat treatment, the heating rate is 2-10°C / min. Preferably, during the heat treatment, the heating rate is 5-10°C / min.

[0033] Optionally, the time of the acid treatment is 12-36h. Preferably, the time of the acid treatment is 20-30h.

[0034] Specifically, the time of the acid treatment is 24h.

[0035] Optionally, the rotation speed of the centrifugation is 7000-10000 rad / s.

[0036] Optionally, the temperature of the drying is 40-90°C, and the time of the drying is 10-30h; preferably, the temperature of the drying is 70-90°C, and the time of the drying is 22-26h.

[0037] Optionally, by grinding until all the solid powders become a flowable black liquid.

[0038] Another aspect of the present application provides a cathode material, including a substrate and the nitrogen-doped two-dimensional carbon material;

[0039] The nitrogen-doped two-dimensional carbon material is supported on one side surface of the substrate.

[0040] Optionally, the substrate is selected from any one or more of carbon felt, graphite felt, and carbon cloth.

[0041] Optionally, the loading amount of the nitrogen-doped two-dimensional carbon material on the substrate is 1-20 mg / cm 2, preferably, the loading amount of the nitrogen atom-doped two-dimensional carbon material on the substrate is 5-15 mg / cm 2 .

[0042] On the other hand, the present application provides a method for preparing the positive electrode material, including: coating the nitrogen atom-doped two-dimensional carbon material on one side surface of the substrate to obtain the positive electrode material.

[0043] Optionally, the method for preparing the positive electrode material for the bromine flow battery includes: mixing the nitrogen atom-doped two-dimensional carbon material, an organic solvent, and a binder, ultrasonicating, and coating on one side surface of the substrate to obtain the positive electrode material for the bromine flow battery.

[0044] Optionally, the binder is selected from any one or more of Nafion, polyvinylidene fluoride, and polytetrafluoroethylene.

[0045] Optionally, the mass ratio of the binder to the nitrogen atom-doped two-dimensional carbon material is 1:(1-10), preferably, the mass ratio of the binder to the nitrogen atom-doped two-dimensional carbon material is 1:(2-6).

[0046] Specifically, the mass ratio of the binder to the nitrogen atom-doped two-dimensional carbon material is 1:5.

[0047] Optionally, the mass ratio of isopropanol to the nitrogen atom-doped two-dimensional carbon material is (20-100):1, and further preferably (30-80):1.

[0048] Specifically, the mass ratio of isopropanol to the nitrogen atom-doped two-dimensional carbon material is 60:1.

[0049] On the other hand, the present application provides an application of the positive electrode material in a bromine flow battery.

[0050] The beneficial effects that the present application can produce include:

[0051] (1) The nitrogen atom-doped two-dimensional carbon material with controllable interlayer spacing in the present application has a regular two-dimensional layered structure, has a super-large specific surface area, rich nitrogen content, accelerates mass diffusion, significantly improves the catalytic activity of the bromine electrode reaction, and improves the battery efficiency;

[0052] (2) The morphology and interlayer spacing of the nitrogen atom-doped two-dimensional carbon material in the present application are controllable. By adjusting the interlayer spacing, bromine species can be confined between layers, inhibiting their migration and diffusion to the negative electrode, thereby inhibiting the self-discharge of the battery, having good stability, and effectively improving the efficiency and life of the bromine flow battery;

[0053] (3) This application is prepared by the template method. Using inorganic salts as templates, after complexation or intercalation with organic precursors, high-temperature pyrolysis is carried out, and then the templates are removed. The process is simple, the operation is convenient, the cost is low, it can be mass-produced, and it is safe and environmentally friendly. Description of the Drawings

[0054] Figure 1a SEM image of Comparative Example 1, with a size of 1 μm;

[0055] Figure 1b SEM image of Comparative Example 4, with a size of 1 μm;

[0056] Figure 1c SEM image of Example 1, with a size of 1 μm;

[0057] Figure 1d SEM image of Example 2, with a size of 100 nm;

[0058] Figure 1e SEM image of Example 3, with a size of 100 nm;

[0059] Figure 1f SEM image of Example 4, with a size of 100 nm;

[0060] Figure 2 Comparison chart of layer spacings of Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, Example 1, Example 2, Example 2, and Example 4;

[0061] Figure 3 Specific surface area comparison chart of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1, Example 2, Example 3, and Example 4;

[0062] Figure 4 Nitrogen content comparison chart of Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, Example 1, Example 2, Example 2, and Example 4;

[0063] Figure 5 Chart of the proportion of different nitrogen types in Comparative Example 4, Example 1, Example 2, and Example 3;

[0064] Figure 6 Catalytic activity comparison chart of Comparative Example 7, Comparative Example 8, Comparative Example 9, Comparative Example 10, Example 5, Example 6, Example 7, and Example 8;

[0065] Figure 7 At a current density of 80 mA / cm 2 Self-discharge performance chart of the zinc-bromine flow batteries assembled in Comparative Example 7, Comparative Example 9, Comparative Example 10, Comparative Example 11, Example 5, Example 6, Example 7, and Example 8;

[0066] Figure 8 At a current density of 80 mA / cm 2 The performance graphs of the zinc-bromine flow batteries assembled in Comparative Example 7, Comparative Example 9, Comparative Example 10, Comparative Example 11, Example 5, Example 6, Example 7, and Example 8. Detailed implementation manners

[0067] The present application will be described in detail below in conjunction with examples, but the present application is not limited to these examples.

[0068] Unless otherwise specified, the raw materials in the examples of the present application are all purchased through commercial channels.

[0069] In the examples of the present application, a scanning electron microscope (JSM-7800F and SUI510) was used to perform SEM tests on the materials obtained in the comparative examples and examples.

[0070] In the examples of the present application, an X-ray diffractometer (XRD, D8 ADVANCE ECO) was used to detect the structures of the comparative examples and examples, and the layer spacing was calculated according to the Bragg equation.

[0071] X-ray photoelectron spectroscopy (XPS, Thermo ESCALAB 250XI) was used to analyze the nitrogen element in the comparative examples and examples.

[0072] In the examples of the present application, a gas adsorption analyzer (ASAP2010 / ASAP2010M) was used for N 2 adsorption / desorption measurement to study the specific surface area of the material. The Brunauer-Emmett-Teller (BET) method was used to calculate the specific surface area.

[0073] In the examples of the present application, an electrochemical workstation Gamry multi-channel system (Gamry Interface 1000, Gamry Interface 3000) was used to perform CV tests on the materials obtained in the comparative examples and examples.

[0074] Comparative Example 1:

[0075] Weigh 10 mmol of sodium chloride and 10 mmol of dopamine hydrochloride and mix them in a mortar and grind until all the solid powders turn into a flowable black liquid. Immediately transfer the resulting mixture to a porcelain boat and conduct heat treatment in an argon atmosphere. The argon flow rate is 50 ml / min, the temperature is 500 °C, the time is 3 h, and the heating rate is 5 °C / min. After the reaction ends, cool it to room temperature to obtain a black product. Treat the obtained black product with 0.6 M hydrochloric acid for 24 h and then wash it with deionized water multiple times, centrifuge it at a rotational speed of 8000 rad / s, and dry it at 80 °C for 24 h to obtain Comparative Example 1. It has a non-two-dimensional layered structure, a specific surface area of 73.62 m 2 / g, and the nitrogen element content is 0.

[0076] Comparative Example 2:

[0077] Weigh 10 mmol of ferric sulfate and 10 mmol of dopamine hydrochloride and mix them in a mortar and grind until all the solid powders turn into a flowable black liquid. Immediately transfer the resulting mixture to a porcelain boat and conduct heat treatment in an argon atmosphere. The argon flow rate is 50 ml / min, the temperature is 500 °C, the time is 3 h, and the heating rate is 5 °C / min. After the reaction ends, cool it to room temperature to obtain a black product. Treat the obtained black product with 0.6 M hydrochloric acid for 24 h and then wash it with deionized water multiple times, centrifuge it at a rotational speed of 8000 rad / s, and dry it at 80 °C for 24 h to obtain Comparative Example 2. It has a non-two-dimensional layered structure, a specific surface area of 69.10 m 2 / g, and the nitrogen element content is 0.

[0078] Comparative Example 3:

[0079] Weigh 10 mmol of ferric chloride hexahydrate and 10 mmol of phenol and mix them in a mortar and grind until all the solid powders turn into a flowable black liquid. Immediately transfer the resulting mixture to a porcelain boat and conduct heat treatment in an argon atmosphere. The argon flow rate is 50 ml / min, the temperature is 500 °C, the time is 3 h, and the heating rate is 5 °C / min. After the reaction ends, cool it to room temperature to obtain a black product. Treat the obtained black product with 0.6 M hydrochloric acid for 24 h and then wash it with deionized water multiple times, centrifuge it at a rotational speed of 8000 rad / s, and dry it at 80 °C for 24 h to obtain Comparative Example 3. It has a two-dimensional layered structure, and the layer spacing is The specific surface area is 197.24 m 2 / g, and the nitrogen element content is 0.

[0080] Comparative Example 4:

[0081] Weigh 100 mmol of ferric chloride hexahydrate and 10 mmol of dopamine hydrochloride and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the resulting mixture to a porcelain boat and conduct heat treatment in an argon atmosphere with an argon flow rate of 50 ml / min, a temperature of 500 °C, a time of 3 h, and a heating rate of 5 °C / min. After the reaction ends and cools to room temperature, a black product is obtained. The obtained black product is treated with 0.6 M hydrochloric acid for 24 h and then washed repeatedly with deionized water, centrifuged at a speed of 8000 rad / s, and dried at 80 °C for 24 h to obtain Comparative Example 4. Two-dimensional layered structure with an interlayer spacing of The specific surface area is 201.53 m 2 / g, the nitrogen element content is 2.10%, and the proportions of graphitic nitrogen and pyridinic nitrogen are 48.55% and 13.78% respectively.

[0082] Comparative Example 5:

[0083] Weigh 10 mmol of ferric chloride hexahydrate and 10 mmol of dopamine hydrochloride and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the resulting mixture to a porcelain boat and conduct heat treatment in an argon atmosphere with an argon flow rate of 50 ml / min, a temperature of 500 °C, a time of 0.5 h, and a heating rate of 5 °C / min. After the reaction ends and cools to room temperature, a black product is obtained. The obtained black product is treated with 0.6 M hydrochloric acid for 24 h and then washed repeatedly with deionized water, centrifuged at a speed of 8000 rad / s, and dried at 80 °C for 24 h to obtain Comparative Example 5. Two-dimensional layered structure with an interlayer spacing of The specific surface area is 204.13 m 2 / g, the nitrogen element content is 3.20%, and the proportions of graphitic nitrogen and pyridinic nitrogen are 48.97% and 14.23% respectively.

[0084] Comparative Example 6:

[0085] Weigh 10 mmol of ferric chloride hexahydrate and 10 mmol of dopamine hydrochloride and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the resulting mixture to a porcelain boat and conduct heat treatment in an argon atmosphere with an argon flow rate of 50 ml / min, a temperature of 100 °C, a time of 3 h, and a heating rate of 5 °C / min. After the reaction ends and cools to room temperature, a black product is obtained. The obtained black product is treated with 0.6 M hydrochloric acid for 24 h and then washed repeatedly with deionized water, centrifuged at a speed of 8000 rad / s, and dried at 80 °C for 24 h to obtain Comparative Example 6. Two-dimensional layered structure with an interlayer spacing of The specific surface area is 200.71 m 2 / g, the nitrogen element content is 3.70%.

[0086] Comparative Example 7:

[0087] Commercialized pristine carbon felt, with dimensions of 3 cm * 3 cm * 5 mm.

[0088] Electrochemical performance test (CV): Cut a circular piece with a diameter of 6 mm and a thickness of 2 mm from the above-mentioned pristine carbon felt. With the help of an electrochemical workstation (Gamry Multichannel Systeminstallation, Reference 3000), use a three-electrode system to evaluate the electrochemical activity of the material. The CV test conditions are as follows: The working electrode is the pristine carbon felt, the reference electrode is the Ag / AgCl electrode, the counter electrode is the graphite plate, and the electrolyte is 2M ZnBr 2 + 3M KCl + 0.4M MEPBr (N,N-methyl-ethylpyrrolidinium bromide), and the scanning rate is 10 mV / s.

[0089] Self-discharge performance test: Assemble a zinc-bromine flow battery. Both the positive and negative electrodes use untreated pristine carbon felt electrodes, the separator is a commercial Daramic porous membrane, and the electrolyte is 2M ZnBr 2 + 3M KCl + 0.4M MEPBr. Perform 15 charge-discharge cycles under the condition of a current density of 80 mA / cm 2 Then, after leaving it standing for 24 h, test the Coulomb efficiency of the 16th cycle.

[0090] Battery performance test under the condition of a current density of 80 mA / cm 2 : Assemble a zinc-bromine flow battery. Both the positive and negative electrodes use pristine carbon felt electrodes, the separator is a commercial Daramic porous membrane, and the electrolyte is 2M ZnBr 2 + 3M KCl + 0.4M MEPBr.

[0091] Comparative Example 8:

[0092] After thoroughly grinding Comparative Example 1, weigh 0.05 g and mix it evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and spray it on a pristine carbon felt with dimensions of 3 cm * 3 cm * 5 mm by ultrasonic treatment for several hours.

[0093] Electrochemical performance test (CV): Cut a circular piece with a diameter of 6 mm and a thickness of 2 mm from the above-mentioned Comparative Example 8 as the working electrode, and other conditions are the same as those in Comparative Example 7.

[0094] Self-discharge performance test: Use the above-mentioned Comparative Example 8 for the positive electrode and an untreated pristine carbon felt electrode for the negative electrode, and other conditions are the same as those in Comparative Example 7.

[0095] Battery performance test under the condition of a current density of 80 mA / cm 2The battery performance test was carried out under the following conditions: the positive electrode used the above Comparative Example 8, the negative electrode used the untreated original carbon felt electrode, and other conditions were the same as those in Comparative Example 7.

[0096] Comparative Example 9:

[0097] 0.05 g of the well-ground Comparative Example 3 was weighed and mixed evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and then sprayed on the original carbon felt with a size of 3 cm * 3 cm * 5 mm after ultrasonic treatment for several hours.

[0098] Electrochemical performance test (CV): The above Comparative Example 9 was cut into a circle with a diameter of 6 mm and a thickness of 2 mm as the working electrode, and other conditions were the same as those in Comparative Example 7.

[0099] Self-discharge performance test: The positive electrode used the above Comparative Example 9, the negative electrode used the untreated original carbon felt electrode, and other conditions were the same as those in Comparative Example 7.

[0100] The battery performance test was carried out under the condition that the current density was 80 mA / cm 2 : The positive electrode used the above Comparative Example 9, the negative electrode used the untreated original carbon felt electrode, and other conditions were the same as those in Comparative Example 7.

[0101] Comparative Example 10:

[0102] 0.05 g of the well-ground Comparative Example 4 was weighed and mixed evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and then sprayed on the original carbon felt with a size of 3 cm * 3 cm * 5 mm after ultrasonic treatment for several hours.

[0103] Electrochemical performance test (CV): The above Comparative Example 10 was cut into a circle with a diameter of 6 mm and a thickness of 2 mm as the working electrode, and other conditions were the same as those in Comparative Example 7.

[0104] Self-discharge performance test: The positive electrode used the above Comparative Example 10, the negative electrode used the untreated original carbon felt electrode, and other conditions were the same as those in Comparative Example 7.

[0105] The battery performance test was carried out under the condition that the current density was 80 mA / cm 2 : The positive electrode used the above Comparative Example 10, the negative electrode used the untreated original carbon felt electrode, and other conditions were the same as those in Comparative Example 7.

[0106] Example 1:

[0107] Weigh 10 mmol of ferric chloride hexahydrate and 10 mmol of dopamine hydrochloride and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the obtained mixture to a porcelain boat and conduct heat treatment in an argon atmosphere with an argon flow rate of 50 ml / min, a temperature of 500 °C, a time of 3 h, and a heating rate of 5 °C / min. After the reaction ends, cool it to room temperature to obtain a black product. Treat the obtained black product with 0.6 M hydrochloric acid for 24 h and then wash it with deionized water multiple times, centrifuge it at a speed of 8000 rad / s, and dry it at 80 °C for 24 h to obtain Example 1. Two-dimensional layered structure, the layer spacing is The specific surface area is 653.98 m 2 / g, the nitrogen element content is 39.80%, and the proportions of graphitic nitrogen and pyridinic nitrogen are 50.26% and 15.81% respectively.

[0108] Example 2:

[0109] Weigh 10 mmol of ferric chloride hexahydrate and 50 mmol of dopamine hydrochloride and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the obtained mixture to a porcelain boat and conduct heat treatment in an argon atmosphere with an argon flow rate of 50 ml / min, a temperature of 500 °C, a time of 3 h, and a heating rate of 5 °C / min. After the reaction ends, cool it to room temperature to obtain a black product. Treat the obtained black product with 0.6 M hydrochloric acid for 24 h and then wash it with deionized water multiple times, centrifuge it at a speed of 8000 rad / s, and dry it at 80 °C for 24 h to obtain Example 2. Two-dimensional layered structure, the layer spacing is The specific surface area is 868.11 m 2 / g, the nitrogen element content is 45.20%, and the proportions of graphitic nitrogen and pyridinic nitrogen are 59.82% and 20.26% respectively.

[0110] Example 3:

[0111] Weigh 10 mmol of ferric chloride hexahydrate and 10 mmol of aniline and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the obtained mixture to a porcelain boat and conduct heat treatment in an argon atmosphere with an argon flow rate of 50 ml / min, a temperature of 500 °C, a time of 3 h, and a heating rate of 5 °C / min. After the reaction ends, cool it to room temperature to obtain a black product. Treat the obtained black product with 0.6 M hydrochloric acid for 24 h and then wash it with deionized water multiple times, centrifuge it at a speed of 8000 rad / s, and dry it at 80 °C for 24 h to obtain Example 3. Two-dimensional layered structure, the layer spacing is The specific surface area is 677.32 m 2 / g, the nitrogen element content is 37.40%, and the proportions of graphitic nitrogen and pyridinic nitrogen are 41.06% and 14.81% respectively.

[0112] Example 4:

[0113] Weigh 10 mmol of zinc nitrate hexahydrate and 10 mmol of dopamine hydrochloride and place them in a mortar for mixing and grinding until all the solid powders turn into a flowable black liquid. Immediately transfer the obtained mixture to a porcelain boat and conduct heat treatment in an argon atmosphere. The argon flow rate is 50 ml / min, the temperature is 400 °C, the time is 4 h, and the heating rate is 5 °C / min. After the reaction ends and cools to room temperature, a black product is obtained. The obtained black product is treated with 0.6 M hydrochloric acid for 24 h and then washed repeatedly with deionized water, centrifuged at a speed of 8000 rad / s, and dried at 80 °C for 24 h to obtain Example 4. The two-dimensional layered structure has an interlayer spacing of The specific surface area is 982.67 m 2 / g, the nitrogen element content is 42.10%, and the proportions of graphitic nitrogen and pyridinic nitrogen are 48.25% and 16.34% respectively.

[0114] Example 5:

[0115] After thoroughly grinding Example 1, weigh 0.05 g and mix it evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and spray it on the original carbon felt with dimensions of 3 cm * 3 cm * 5 mm after ultrasonic treatment for several hours.

[0116] Electrochemical performance test (CV): Cut out a circle with a diameter of 6 mm and a thickness of 2 mm from the above Example 5 as the working electrode, and the other conditions are the same as those in Comparative Example 7.

[0117] Self-discharge performance test: Use the above Example 5 as the positive electrode and the untreated original carbon felt electrode as the negative electrode, and the other conditions are the same as those in Comparative Example 7.

[0118] The battery performance test is carried out under the condition that the current density is 80 mA / cm 2 : Use the above Example 5 as the positive electrode and the untreated original carbon felt electrode as the negative electrode, and the other conditions are the same as those in Comparative Example 7.

[0119] Example 6:

[0120] After thoroughly grinding Example 2, weigh 0.05 g and mix it evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and spray it on the original carbon felt with dimensions of 3 cm * 3 cm * 5 mm after ultrasonic treatment for several hours.

[0121] Electrochemical performance test (CV): Cut out a circle with a diameter of 6 mm and a thickness of 2 mm from the above Example 5 as the working electrode, and the other conditions are the same as those in Comparative Example 7.

[0122] Self-discharge performance test: The positive electrode uses the above-mentioned Example 6, and the negative electrode uses the untreated original carbon felt electrode. Other conditions are the same as those in Comparative Example 7.

[0123] The current density is 80 mA / cm 2 Under this condition, the battery performance test is carried out: The positive electrode uses the above-mentioned Example 6, and the negative electrode uses the untreated original carbon felt electrode. Other conditions are the same as those in Comparative Example 7.

[0124] Example 7:

[0125] After thoroughly grinding Example 3, 0.05 g is weighed and mixed evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and then sprayed on the original carbon felt with a size of 3 cm * 3 cm * 5 mm after ultrasonic treatment for several hours.

[0126] Electrochemical performance test (CV): Cut out a circle with a diameter of 6 mm and a thickness of 2 mm from the above-mentioned Example 3 as the working electrode. Other conditions are the same as those in Comparative Example 7.

[0127] Self-discharge performance test: The positive electrode uses the above-mentioned Example 7, and the negative electrode uses the untreated original carbon felt electrode. Other conditions are the same as those in Comparative Example 7.

[0128] The current density is 80 mA / cm 2 Under this condition, the battery performance test is carried out: The positive electrode uses the above-mentioned Example 7, and the negative electrode uses the untreated original carbon felt electrode. Other conditions are the same as those in Comparative Example 7.

[0129] Example 8:

[0130] After thoroughly grinding Example 4, 0.05 g is weighed and mixed evenly with 0.2 g of 0.05 wt% Nafion solution and 3 g of isopropanol, and then sprayed on the original carbon felt with a size of 3 cm * 3 cm * 5 mm after ultrasonic treatment for several hours.

[0131] Electrochemical performance test (CV): Cut out a circle with a diameter of 6 mm and a thickness of 2 mm from the above-mentioned Example 5 as the working electrode. Other conditions are the same as those in Comparative Example 7.

[0132] Self-discharge performance test: The positive electrode uses the above-mentioned Example 8, and the negative electrode uses the untreated original carbon felt electrode. Other conditions are the same as those in Comparative Example 7.

[0133] The current density is 80 mA / cm 2 Under this condition, the battery performance test is carried out: The positive electrode uses the above-mentioned Example 8, and the negative electrode uses the untreated original carbon felt electrode. Other conditions are the same as those in Comparative Example 7.

[0134] The raw materials and conditions of the comparative examples and examples are shown in the following table.

[0135]

[0136]

[0137] Figure 1a SEM image of Comparative Example 1 Figure 1b SEM image of Comparative Example 4 Figure 1c SEM image of Example 1 Figure 1d SEM image of Example 2 Figure 1e SEM image of Example 3 Figure 1f SEM image of Example 4. It can be seen from the figure that when using a non - layered inorganic salt template (Comparative Example 1) or when the layered inorganic salt template is severely in excess (Comparative Example 4), the obtained material has an irregular two - dimensional layered structure. While when the molar ratio of the layered inorganic salt template to the organic precursor is within a suitable range (Examples 1, 2, 3, 4), the material prepared by the present invention has a regular two - dimensional layered structure, and by changing conditions such as the types, ratios, and heat treatment time of the layered inorganic salt template and the organic precursor, the density of the structure can be changed, making the interlayer more compact or loose.

[0138] Figure 2 Comparison chart of interlayer spacing of Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, Example 1, Example 2, Example 3, and Example 4. The interlayer spacings are respectively It can be seen from the figure that when the structure of the organic precursor is different (Comparative Example 3), the addition amount is less (Comparative Example 4), the heat treatment time is too short resulting in insufficient intercalation / complexation reaction (Comparative Example 5), or the heat treatment time is too short resulting in insufficient intercalation / complexation reaction (Comparative Example 6), the interlayer spacing of the obtained material is relatively small, about or so. While when the molar ratio of the layered inorganic salt template to the organic precursor is within a suitable range and conditions such as the heat treatment temperature and time are adjusted to make the reaction sufficient (Examples 1, 2, 3, 4), the interlayer spacing of the two - dimensional carbon material prepared by the present invention can be regulated to make the interlayer more loose.

[0139] Figure 3 Comparison chart of specific surface areas of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1, Example 2, Example 3, and Example 4. The specific surface areas are respectively 73.62 m 2 g -1 ,69.10 m 2 g -1 ,197.24 m 2 g -1 ,201.53 m 2 g -1 ,653.98 m 2 g -1 ,868.11 m2 g -1 ,677.32 m 2 g -1 ,982.67 m 2 g -1 。As can be seen from the figure, when using non-layered inorganic salt templates (Comparative Example 1 and Comparative Example 2), materials with a layered structure cannot be obtained, so their specific surface areas are relatively small. When the structures of the organic precursors are different (Comparative Example 3) or the addition amounts are small (Comparative Example 4), it is impossible to fully intercalate or complex the inorganic salt template layers to increase their effective exposed areas, so the specific surface area only increases slightly. When the molar ratio of the layered inorganic salt template to the organic precursor is within a suitable range and the heat treatment temperature and time are adjusted to make the reaction sufficient (Examples 1, 2, 3, and 4), the interlayer spacing of the two-dimensional carbon material prepared in the present invention can be adjusted. The increased interlayer spacing exposes more active areas, and different pore structures are generated after pickling to remove the template, resulting in a significant increase in the specific surface area.

[0140] Figure 4 Figure for comparing the nitrogen contents of Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, Example 1, Example 2, Example 2, and Example 4. The nitrogen element contents are 0.00%, 2.10%, 3.20%, 3.70%, 39.80%, 45.20%, 37.40%, and 42.10% respectively. If an organic precursor containing an amino group is not used, the nitrogen element content of the obtained material is 0 (Comparative Example 3); if the addition amount of the organic precursor containing an amino group is small (Comparative Example 4), when the heat treatment time is too short (Comparative Example 5) or the heat treatment time is too short to fully introduce the ammonia-containing precursor into the interlayer (Comparative Example 6), the nitrogen element content in the prepared material is less than 5%. When the molar ratio of the layered inorganic salt template to the organic precursor is within a suitable range and the heat treatment temperature and time are adjusted to make the reaction sufficient (Examples 1, 2, 3, and 4), the amino group can be effectively introduced into the interlayer, and the nitrogen element content in the material prepared in the present invention is as high as more than 35%.

[0141] Figure 5Graph showing the proportion of different nitrogen types in Comparative Example 4, Example 1, Example 2, and Example 3. In Comparative Example 4, the content of graphitic nitrogen is 45.78% and the content of pyridinic nitrogen is 22.05%. In Example 1, the content of graphitic nitrogen is 50.26% and the content of pyridinic nitrogen is 15.81%. In Example 2, the content of graphitic nitrogen is 59.82% and the content of pyridinic nitrogen is 20.26%. In Example 3, the content of graphitic nitrogen is 41.06% and the content of pyridinic nitrogen is 14.81%. When the type and addition amount of the organic precursor are changed or the heat treatment conditions are changed (Comparative Example 4, Example 1, Example 2, Example 3), not only the nitrogen content of the obtained material will be changed, but also the proportion of different types of nitrogen will be affected. For example, when dopamine hydrochloride is used as the organic precursor, the content of graphitic nitrogen and pyridinic nitrogen will be significantly increased (Comparative Example 4, Example 1, Example 2).

[0142] Figure 6 Graph comparing the catalytic activities of Comparative Example 7, Comparative Example 8, Comparative Example 9, Comparative Example 10, Example 5, Example 6, Example 7, and Example 8. Compared with the raw carbon felt (Comparative Example 7), when a non-layered material (Comparative Example 8), a material with a nitrogen content of 0 (Comparative Example 9), or a material with a low nitrogen content and a small specific surface area due to insufficient reaction (Comparative Example 10) is supported, the catalytic activity of the electrode only increases slightly. However, the material of the present invention has a large specific surface area and a high nitrogen content, especially a relatively high proportion of graphitic nitrogen and pyridinic nitrogen (relatively strong catalytic ability for bromine), so its catalytic activity is significantly enhanced (Example 5, Example 6, Example 7, Example 8).

[0143] Figure 7 Graph showing the self-discharge performance of the zinc-bromine flow batteries assembled with Comparative Example 7, Comparative Example 9, Comparative Example 10, Comparative Example 11, Example 5, Example 6, Example 7, and Example 8 under the condition of a current density of 80 mA / cm 2 The Coulomb efficiencies are 42.62%, 43.10%, 44.24%, 43.53%, 74.28%, 79.11%, 71.32%, and 76.67% respectively. It can be seen from the graph that the Coulomb efficiencies of the original carbon felt (Comparative Example 7) and the electrodes prepared from non-two-dimensional layered structures, small specific surface areas, and low nitrogen contents (Comparative Example 9, Comparative Example 10, Comparative Example 11) are all lower than 45% after being placed for 24 hours, while the Coulomb efficiencies of the batteries assembled with the materials prepared by the present invention (Example 5, Example 6, Example 7, Example 8) can reach 74%, 79%, 71%, and 77%. The self-discharge performance is significantly improved, indicating that the structure of the electrode material of the present invention is beneficial to inhibiting the migration and diffusion of bromine and slowing down the capacity loss of the battery.

[0144] Figure 8 Graph showing the self-discharge performance of the zinc-bromine flow batteries assembled with Comparative Example 7, Comparative Example 9, Comparative Example 10, Comparative Example 11, Example 5, Example 6, Example 7, and Example 8 under the condition of a current density of 80 mA / cm 2Performance diagrams of the zinc-bromine flow batteries assembled under the conditions of Comparative Example 7, Comparative Example 9, Comparative Example 10, Comparative Example 11, Example 5, Example 6, Example 7, and Example 8. It can be seen from the figure that the coulombic efficiency and voltage efficiency of the zinc-bromine flow batteries assembled with the original carbon felt (Comparative Example 1) and the electrodes prepared with non-two-dimensional layered structures, small specific surface areas, and low nitrogen contents (Comparative Example 9, Comparative Example 10, Comparative Example 11) are about 96% and 78%, respectively. However, the coulombic efficiency and voltage efficiency of the batteries assembled with the materials prepared in the present invention (Example 5, Example 6, Example 7, Example 8) are significantly increased. This is because the larger interlayer spacing of the two-dimensional layered structure increases the effective active area, provides more reactive sites, and its rich nitrogen content further catalyzes the reaction of the bromine positive electrode. At the same time, the transport of substances between the layers is accelerated, further accelerating the reaction kinetics and increasing the reversibility of the reaction. On the other hand, the layered structure is beneficial to restricting the migration and diffusion of large-sized bromine complexes, inhibiting the loss of active substances, so the coulombic efficiency and voltage efficiency of the battery are greatly improved.

[0145] As described above, the above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A nitrogen-doped two-dimensional carbon material with controllable layer spacing, characterized in that, it includes: a layered inorganic salt template and a nitrogen-containing substance; the nitrogen-containing substance is intercalated or complexed between the layered inorganic salt templates; the layered inorganic salt template has a pore structure.

2. The nitrogen-doped two-dimensional carbon material according to claim 1, characterized in that, it has a regular two-dimensional layered structure; Preferably, the interlayer spacing of the nitrogen atom-doped two-dimensional carbon material is Preferably, the interlayer spacing of the nitrogen atom-doped two-dimensional carbon material is Preferably, the interlayer spacing of the nitrogen atom-doped two-dimensional carbon material is Preferably, the specific surface area of the nitrogen atom-doped two-dimensional carbon material is 200-1500 m 2 / g; Preferably, the specific surface area of the nitrogen atom-doped two-dimensional carbon material is 400-1000 m 2 / g; Preferably, the nitrogen atom content of the nitrogen-doped two-dimensional carbon material is 5-50%; Preferably, the nitrogen atom content of the nitrogen-doped two-dimensional carbon material is 20-50%; Preferably, the nitrogen atom content of the nitrogen-doped two-dimensional carbon material is 30-50%.

3. The nitrogen-doped two-dimensional carbon material according to claim 1, characterized in that, the forms of nitrogen atoms in the nitrogen-containing substance include: any one or more of pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen, and oxidized nitrogen; Preferably, in the nitrogen-containing substance, graphitic nitrogen accounts for 30-70%; Preferably, in the nitrogen-containing substance, graphitic nitrogen accounts for 40-60%; Preferably, in the nitrogen-containing substance, pyridine nitrogen accounts for 10-30%; Preferably, in the nitrogen-containing substance, pyridine nitrogen accounts for 12-25%; Preferably, the layered inorganic salt template is selected from any one or more of ferric chloride, zinc nitrate, and magnesium hydroxy silicate.

4. A method for preparing the nitrogen-doped two-dimensional carbon material according to any one of claims 1-3, characterized in that, it includes: Mix the raw material of the layered inorganic salt template and the nitrogen-containing organic precursor, grind, perform heat treatment under an inert gas, cool to obtain a black product, perform acid treatment on the black product, wash with water, centrifuge, and dry to obtain the nitrogen-doped two-dimensional carbon material.

5. The method for preparing the nitrogen-doped two-dimensional carbon material according to claim 4, characterized in that, the raw material of the layered inorganic salt template is selected from any one or more of ferric chloride hexahydrate, zinc nitrate hexahydrate, and magnesium hydroxy silicate; Preferably, the nitrogen-containing organic precursor is selected from any one or more of dopamine hydrochloride, aniline, methylamine, and ethylenediamine; Preferably, the molar ratio of the raw material of the layered inorganic salt template to the nitrogen-containing organic precursor is 1:14-5:1; Preferably, the molar ratio of the raw material of the layered inorganic salt template to the nitrogen-containing organic precursor is 1:10-3:1; Preferably, the inert gas is nitrogen or argon; Preferably, when performing acid treatment, the acid used is hydrochloric acid or sulfuric acid.

6. The method for preparing the nitrogen-doped two-dimensional carbon material according to claim 4, characterized in that, the temperature of the heat treatment is 200-900 °C; Preferably, the temperature of the heat treatment is 300-600 °C; Preferably, the time of the heat treatment is 1-6 h; Preferably, the time of the heat treatment is 2-4 h; Preferably, when performing heat treatment, the gas flow rate of the inert gas is 10-100 ml / min; Preferably, when performing heat treatment, the heating rate is 2-10 °C / min; Preferably, the time of the acid treatment is 12-36 h; Preferably, the rotation speed of the centrifuge is 7000-10000 rad / s; Preferably, the temperature of the drying is 40-90 °C, and the time of the drying is 10-30 h.

7. A cathode material, characterized in that, it comprises a substrate and the nitrogen atom-doped two-dimensional carbon material according to any one of claims 1-3; the nitrogen atom-doped two-dimensional carbon material is supported on one side surface of the substrate.

8. The cathode material according to claim 7, characterized in that, The loading amount of the nitrogen atom-doped two-dimensional carbon material on the substrate is 1-20 mg / cm 2 ; Preferably, the loading amount of the nitrogen atom-doped two-dimensional carbon material on the substrate is 5-15 mg / cm 2 ; preferably, the substrate is selected from any one or more of carbon felt, graphite felt, and carbon cloth.

9. A preparation method of the cathode material according to claim 7 or 8, characterized in that, it includes: coating the nitrogen atom-doped two-dimensional carbon material on one side surface of the substrate to obtain the cathode material.

10. An application of the cathode material according to claim 7 or 8 in a bromine-based flow battery.

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