Nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst and preparation method thereof

Abstract

The invention discloses a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst and a preparation method thereof, and belongs to the technical field of oxygen evolution electrocatalyst preparation. The preparation method of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst comprises the following steps: soaking cattail wool in a cobalt nitrate solution, taking out and drying to obtain an intermediate product; and mixing the intermediate product with dicyandiamide, and calcining to obtain the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst. In the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst, nitrogen doping optimizes the electronic structure of biomass carbon, increases active sites, improves the conductivity of the material, and is beneficial to rapid transfer and conduction of electrons in the oxygen evolution reaction process; and the cobalt catalyzes the growth of the carbon nanotubes on the biomass carbon, so that the specific surface area of the material is further increased, more reaction active sites are provided, and meanwhile, the structural stability of the material is enhanced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oxygen evolution electrocatalyst preparation, and more particularly relates to a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst and a preparation method thereof. BACKGROUND

[0002] Water electrolysis hydrogen production is a clean and efficient hydrogen production method and has attracted widespread attention, and an oxygen evolution reaction catalyst is a key thereof. At present, with the progress of science and technology, people have higher and higher requirements for the performance of the oxygen evolution reaction catalyst, for example, in the field of large-scale water electrolysis hydrogen production or high-performance fuel cells, the activity, stability and other aspects of the catalyst have strict requirements. At present, noble metal Ru and its alloy materials are still the most efficient oxygen evolution catalysts, but the problems of high cost, low abundance of reserves and poor stability greatly limit their application in commerce. Therefore, it is necessary to develop efficient, relatively abundant non-noble metal electrocatalysts to replace platinum-based materials.

[0003] In recent years, in the field of oxygen evolution reaction catalysts, carbon-based catalysts have always shown great application potential and are favored by researchers. The newly developed carbon-based catalysts in recent years mostly use graphene or carbon nanotubes as carriers. These materials have excellent electrical conductivity and chemical stability, but the high preparation cost and complicated synthesis process seriously restrict their large-scale commercial application. Therefore, it is of great practical significance to explore carbon-based oxygen evolution catalysts with simple preparation process, low cost and excellent catalytic performance.

[0004] Based on this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst and a preparation method thereof, so as to solve the problems of low catalytic activity, high preparation cost and difficulty in large-scale utilization of existing oxygen evolution catalysts, and to realize the preparation of carbon-based oxygen evolution catalysts with simple preparation process, low cost and excellent catalytic performance.

[0006] To achieve the above-mentioned purpose, the present application provides the following solutions.

[0007] One of the technical solutions of the present application provides a preparation method of a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst, comprising the following steps:

[0008] The puhuang is soaked in a cobalt nitrate solution, taken out and dried to obtain an intermediate product; the intermediate product and dicyandiamide are mixed and calcined to obtain the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst.

[0009] Preferably, the pua fur before use also includes the steps of washing and drying, specifically: the pua fur is washed with water and anhydrous ethanol alternately, each time for 15-30 min of ultrasonic washing; and then is placed in an oven for drying at 50-60 DEG C.

[0010] Preferably, the concentration of the cobalt nitrate solution is 0.3-0.5 mol / L.

[0011] Preferably, the soaking time is 12-20 h.

[0012] Further, the drying is freeze-drying.

[0013] Preferably, the mass ratio of the intermediate product and dicyandiamide is 0.3:(1.2-3.6).

[0014] Preferably, the calcination is carried out under a nitrogen atmosphere; the calcination temperature is 700-900 DEG C, the temperature rising rate is 5 DEG C / min, and the holding time is 1.5-2 h.

[0015] Preferably, the preparation method comprises the following steps:

[0016] The pua fur is uniformly dispersed in a cobalt nitrate solution after washing and drying, is soaked, and is freeze-dried to obtain an intermediate product; the intermediate product and dicyandiamide are respectively placed in two porcelain boats, are placed in a nitrogen atmosphere tube furnace, are calcined by programmed heating to a calcination temperature to obtain the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst; and the porcelain boat containing dicyandiamide is placed on the side of the nitrogen atmosphere tube furnace gas inlet.

[0017] The second technical scheme of the present application provides the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst prepared by the above preparation method.

[0018] The technical principle of the present application is as follows:

[0019] The biomass soaked in the cobalt nitrate solution is annealed with dicyandiamide in a tube furnace, in the annealing process, the biomass is carbonized under high temperature to form biomass carbon, at the same time, dicyandiamide is decomposed to generate active groups containing nitrogen, and the active groups react with the biomass carbon to make the nitrogen atoms successfully doped into the lattice structure of the biomass carbon, in addition, the carbon source in the system is catalyzed by cobalt ions to grow on the surface of the biomass carbon in situ to form a nitrogen-doped biomass carbon composite material with a unique structure, in the composite material, the nitrogen doping optimizes the electronic structure of the biomass carbon, increases the active sites, and improves the conductivity of the material, which is beneficial to the rapid transfer and conduction of electrons in the oxygen evolution reaction process, and the growth of the carbon nanotubes further increases the specific surface area of the material, provides more reaction active sites, and enhances the structural stability of the material, the cobalt element participates in and promotes the whole reaction system during the reaction, and finally makes the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst exhibit excellent oxygen evolution catalytic performance, which can be used as a good oxygen evolution catalyst.

[0020] The biomass carbon refers to a carbon-rich material generated by pyrolysis of biomass under oxygen-limited or oxygen-free conditions. The carbon material has good chemical properties and high conductivity, and is widely used in the fields of energy and catalysis. The biomass carbon is simple to prepare, has a wide source, low cost and good performance, and is suitable for large-scale production. The present application develops a low-cost nitrogen-doped puccoon biomass carbon-based carbon nanotube oxygen evolution catalyst material, which maximizes the core advantages, suppresses the shortcomings, fully plays the synergistic complementary effect, and improves the performance of the composite catalyst.

[0021] The present application discloses the following technical effects:

[0022] (1) The present application uses puccoon biomass as a carbon source, uses cobalt nitrate solution and dicyandiamide as raw materials, realizes in-situ growth of carbon nanotubes on puccoon biomass carbon through a tube furnace annealing process, and successfully prepares a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst.

[0023] (2) The preparation process has mild and easy-to-control conditions, the whole process is simple and efficient, and has good environmental friendliness and low energy consumption characteristics. In the annealing process, no additional impurity removal step is needed, the prepared composite material has high purity, the carbon nanotubes are uniformly distributed on the puccoon biomass carbon, and the nitrogen doping effect is significant, which provides feasibility for large-scale industrial production.

[0024] (3) The puccoon biomass raw material used in the present application has a wide source and low cost, and has a renewable advantage. The obtained nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst has high conductivity and high chemical stability of biomass carbon, and enhanced catalytic active sites of carbon nanotubes. As an oxygen evolution catalyst, it exhibits excellent electrochemical performance.

[0025] (4) The application discloses a preparation method of a nitrogen-doped biomass carbon-based carbon nanotube composite material, which is realized through a simple process, is simple in process flow, low in energy consumption and green in environment protection, is low in cost and convenient in operation based on easily obtained raw materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 X-ray diffraction patterns (XRD) of nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalysts obtained in Example 1 and Comparative Example 1, wherein a is Example 1, and b is Comparative Example 1;

[0027] Figure 2 Scanning electron microscope (SEM) images of nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalysts obtained in Example 1 and Comparative Example 1, wherein a is the SEM images of Example 1 at different magnifications, and b is the SEM images of Comparative Example 1 at different magnifications;

[0028] Figure 3 An EDS spectrum of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in Example 1;

[0029] Figure 4 Polarization curves of nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalysts obtained in each example and comparative example, wherein a is Example 1, b is Example 2, c is Example 3, and d is Comparative Example 1;

[0030] Figure 5 A 24h stability curve of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in Example 1 tested by chronoamperometry. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of the application and not restrictive of the application. It will be understood that the detailed description and specific examples, while indicating certain embodiments of the application, are intended to be illustrative only and are not intended to limit the scope of the application.

[0032] It should be understood that the terms used in the present application merely describe particular embodiments and are not intended to limit the present application. In addition, for the numerical ranges in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range within the larger range, as well as the intermediate values within the stated ranges, and any other stated value or intermediate value within the stated ranges are also included in the present application. The upper limit and the lower limit of these smaller ranges can be included or excluded independently from the range.

[0033] Unless otherwise indicated, all technical and scientific terms have the same meaning as those one of ordinary skill in the art of the disclosure would understand. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. All documents mentioned herein are incorporated by reference to disclose and describe in further detail the methods and / or materials associated with the documents. In the case of conflict between the disclosure of the present specification and the documents incorporated by reference, the present specification will control.

[0034] Many modifications and variations of the present disclosure described in the detailed description of the disclosure can be made by those of skill in the art without departing from the scope or spirit of the disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure. The specification and examples of the disclosure are illustrative only.

[0035] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more other elements can be added or otherwise included.

[0036] It should be noted that the present disclosure does not describe in detail the conventional operation means in the art, and is not the focus of the present disclosure.

[0037] The raw materials used in the following examples and comparative examples of the present disclosure are commercially available unless otherwise specified, and the source of the commercially available products does not affect the technical effects of the present disclosure.

[0038] In the examples and comparative examples of the present disclosure, the freeze-drying conditions are -80℃ for 36h.

[0039] Example 1

[0040] The cattail down is removed from the cattail rod and placed in a beaker, and then washed alternately with deionized water and anhydrous ethanol until clean, and then placed in an oven for constant temperature drying at 50-60℃; 300mg of the dried product is taken and immersed in 50mL of a 0.5mol / L cobalt nitrate solution for 12h, and then taken out and placed in a freeze-drying oven for freeze-drying. The freeze-dried product and 3.6g of dicyandiamide are respectively placed in two porcelain boats, which are placed in a tube furnace, and the porcelain boat containing dicyandiamide is placed on the side of the nitrogen inlet of the tube furnace, and calcined at 800℃ for 1.5h at a heating rate of 5℃ / min under a nitrogen atmosphere to obtain a black product, which is a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst.

[0041] The XRD pattern of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in the present example is shown in FIG. a, from which it can be seen that the XRD curve is consistent with the XRD standard card JCPDS NO.150806 of cobalt, indicating that the biomass carbon supported cobalt particle material is successfully prepared. Figure 1 a, from which it can be seen that the XRD curve is consistent with the XRD standard card JCPDS NO.150806 of cobalt, indicating that the biomass carbon supported cobalt particle material is successfully prepared.

[0042] The SEM image of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment is shown below. Figure 2 As shown in Figure a, it can be seen that in the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst, carbon nanotubes grow uniformly on biomass carbon.

[0043] The EDS spectrum of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment is as follows: Figure 3 As shown.

[0044] Figure 3 The image shows the EDS spectrum of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in Example 1. Figure 3 This demonstrates that nitrogen was successfully doped into the prepared nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst.

[0045] Electrochemical tests were performed on the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment, and the results are as follows: Figure 4 As shown in Figure a. Testing revealed that the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment achieved an oxygen evolution current density of 20 mA / cm². 2 The overpotential is 400mV (the theoretical equilibrium potential for the oxygen evolution reaction in water electrolysis is 1.23V), indicating good catalytic activity.

[0046] The stability of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment was tested by chronoamperometry, and the results are as follows: Figure 5 As shown.

[0047] Figure 5 The 24-hour stability curve of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in Example 1 was tested using chronoamperometry. Figure 5 It can be seen that the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment maintains good stability within 24 hours.

[0048] Example 2

[0049] Same as Example 1, except that the dried product was soaked in a cobalt nitrate solution with a concentration of 0.6 mol / L.

[0050] Electrochemical tests were performed on the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment, and the results are as follows: Figure 4 As shown in Figure b. Testing revealed that the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this embodiment achieved an oxygen evolution current density of 20 mA / cm². 2 The overpotential at that time is 500mV.

[0051] Example 3

[0052] The same as example 1, except that the dried product is soaked in a cobalt nitrate solution with a concentration of 0.4 mol / L.

[0053] The nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this example is subjected to electrochemical testing, and the results are shown in Figure 4 The nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this example is subjected to electrochemical testing, and the results are shown in 2 The nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst obtained in this example is subjected to electrochemical testing, and the results are shown in

[0054] It can be seen from the comprehensive analysis that the concentration of the cobalt nitrate solution used for soaking the biomass affects the catalytic performance of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst. The parameters of example 1 are the preferred parameters, and under these preferred parameters, a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst with moderate carbon nanotube content and uniform distribution is obtained, which makes the prepared composite catalyst have excellent catalytic activity.

[0055] Comparative example 1 (omitting the addition of cobalt nitrate and dicyandiamide)

[0056] The cattail down is removed from the cattail rod and placed in a beaker, and deionized water and anhydrous ethanol are alternately washed clean, and then placed in an oven for constant temperature drying at 50-60°C; 300 mg of the dried product is placed in a freeze-drying oven and freeze-dried. The freeze-dried product is placed in a tube furnace and calcined at 800°C for 1.5 h under a nitrogen atmosphere at a heating rate of 5°C / min, obtaining a black product, which is a pure biomass carbon oxygen evolution catalyst.

[0057] The XRD pattern of the pure biomass carbon oxygen evolution catalyst obtained in this comparative example is shown in Figure 1 The XRD curve is consistent with the standard card of carbon, indicating that the pure biomass carbon oxygen evolution catalyst is successfully prepared.

[0058] The SEM image of the pure biomass carbon oxygen evolution catalyst obtained in this comparative example is shown in Figure 2 It can be seen that the cattail biomass carbon has a unique bamboo joint structure.

[0059] The pure biomass carbon oxygen evolution catalyst obtained in this comparative example is subjected to electrochemical testing, and the results are shown in Figure 4 The pure biomass carbon oxygen evolution catalyst obtained in this comparative example is subjected to electrochemical testing, and the results are shown in 2The overpotential at the time was 706 mV. Compared with the overpotential (400 mV, 500 mV, 520 mV) of the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalysts obtained in Comparative Example 1, Example 2 and Example 3 at the same current density, it can be seen that the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalysts obtained in Example 1, Example 2 and Example 3 can more efficiently promote the oxygen evolution reaction, that is, the same current density is reached under smaller additional energy input, thereby reducing energy consumption.

[0060] Comparative Example 2 (omitting the addition of cobalt nitrate)

[0061] The cattail down was taken off from the cattail stick and placed in a beaker, and then washed clean with deionized water and anhydrous ethanol alternately, and then placed in an oven for constant temperature drying at 50-60°C. 300 mg of the dried product was placed in a freeze-drying oven for freeze-drying. The freeze-dried product and 3.6 g of dicyandiamide were respectively placed in two porcelain boats, which were placed in a tube furnace and calcined at 800°C for 1.5 h under a nitrogen atmosphere at a temperature rising rate of 5°C / min to obtain the product.

[0062] The same verification method as in Example 1 and Comparative Example 1 was used to verify the catalytic effect of the obtained product, and the results showed that without using a cobalt catalyst, the growth of carbon nanotubes would be almost impossible, and the catalytic activity would be significantly reduced.

[0063] Comparative Example 3 (omitting the addition of dicyandiamide)

[0064] The cattail down was taken off from the cattail stick and placed in a beaker, and then washed clean with deionized water and anhydrous ethanol alternately, and then placed in an oven for constant temperature drying at 50-60°C. 300 mg of the dried product was placed in a freeze-drying oven for freeze-drying. The freeze-dried product and 3.6 g of dicyandiamide were respectively placed in two porcelain boats, which were placed in a tube furnace and calcined at 800°C for 1.5 h under a nitrogen atmosphere at a temperature rising rate of 5°C / min to obtain the product.

[0065] The same verification method as in Example 1 and Comparative Example 1 was used to verify the catalytic effect of the obtained product, and the results showed that the cattail down was only carbonized to form low-activity amorphous carbon, and could not form carbon nanotubes, resulting in a significant decrease in catalytic performance.

[0066] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0067] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and, while certain modifications are discussed, it is desired to be protected in accordance with the spirit and scope of the application. Therefore, the application is not limited to the specific embodiments shown and described, but only by the scope of the appended claims, unless otherwise specified.

Claims

1. A method for preparing a nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst, characterized in that, Includes the following steps: The cotton was soaked in a cobalt nitrate solution, removed and dried to obtain an intermediate product; the intermediate product was mixed with dicyandiamide and then calcined to obtain the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst.

2. The preparation method according to claim 1, characterized in that, The cattail fluff also includes washing and drying steps before use.

3. The preparation method according to claim 1, characterized in that, The concentration of the cobalt nitrate solution is 0.3–0.5 mol / L.

4. The preparation method according to claim 1, characterized in that, The soaking time is 12 to 20 hours.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the intermediate product to dicyandiamide is 0.3:(1.2-3.6).

6. The preparation method according to claim 1, characterized in that, The calcination is carried out under a nitrogen atmosphere; the calcination temperature is 700-900℃, the heating rate is 5℃ / min, and the holding time is 1.5-2h.

7. The preparation method according to claim 1, characterized in that, Includes the following steps: After washing and drying, the cattail fluff was evenly dispersed in a cobalt nitrate solution and soaked, then freeze-dried to obtain an intermediate product. The intermediate product and dicyandiamide were placed in two ceramic boats respectively, and then placed in a nitrogen atmosphere tube furnace. The temperature was increased to the calcination temperature by a programmed process to obtain the nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst. The ceramic boat containing dicyandiamide is placed on one side of the nitrogen atmosphere tubular furnace inlet.

8. The nitrogen-doped biomass carbon-based carbon nanotube oxygen evolution catalyst prepared by the preparation method according to any one of claims 1 to 7.

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