A three-functional electrocatalytic material, its preparation method and application

Abstract

A preparation method of a three-functional electrocatalytic material provided by the present invention comprises the following steps: (1) Ultrasonically disperse humic acid evenly in deionized water, add cobalt chloride and stir, and then perform freeze-drying to obtain a precursor; (2) Calcinate the precursor obtained by freeze-drying in step (1) at a high temperature, perform acid washing and then nitrogen doping to obtain a three-functional electrocatalytic material. The preparation method of the three-functional electrocatalytic material provided by the present invention utilizes the synergistic effect of Co nanoparticles and Co-N-C to simultaneously catalyze the oxygen reduction reaction, hydrogen evolution reaction and oxygen evolution reaction, so as to improve the catalytic activity and stability of the material. The present invention uses a nitrogen-doped non-metal-based carbon material to prepare a three-functional electrocatalytic carbon material that can simultaneously catalyze the oxygen reduction reaction, hydrogen evolution reaction and oxygen evolution reaction, and solves the problems of high cost, low reserves and poor stability of noble metal catalysts in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a trifunctional electrocatalytic material, a preparation method thereof, and an application thereof. Background Art

[0002] High-performance chemical energy storage materials and devices are the core for realizing the conversion, storage, and utilization of clean energy. As a representative of chemical energy storage systems, lithium-ion batteries have been widely applied. However, lithium-ion batteries have problems such as poor safety, low recovery rate, scarce resources, high price, and serious environmental pollution, becoming a bottleneck for the development of the new energy industry and a resistance to sustainable development. Therefore, from the perspectives of rich resources and environmental friendliness, constructing low-cost and environmentally friendly energy storage devices is crucial for the innovation of the new energy industry.

[0003] However, due to the different interfacial resistances between the cathode and the anode and the complex electron transfer in the oxygen reaction, the overpotential value of the energy storage material is relatively high. Therefore, developing an ideal catalyst to reduce the overpotentials of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) to an ideal state has become the key to the wide application of zinc-air batteries. Currently, noble metals platinum and iridium / ruthenium are excellent catalysts for ORR and OER respectively, but their high cost and poor cycling performance seriously restrict their large-scale production. Therefore, non-noble metal-based single-atom catalysts have received extensive attention due to their high intrinsic activity, maximized atomic utilization rate, and unique coordination structure. Carbon substrates play an important role in metal single-atom catalysts for zinc-air batteries. Bonding heteroatoms such as C, N, O, and S with metal atoms to prepare monodispersed metal atom active centers can maximize the utilization of metal precursors and flexibly regulate the activity of metal centers. However, ordinary carbon materials are extremely prone to corrosion in an alkaline environment, causing the aggregation of metal atoms and the collapse of the structure, thus seriously affecting the service life of the catalyst. Therefore, developing trifunctional electrocatalytic materials with high performance is of great significance.

[0004] Therefore, the prior art needs to be improved. Summary of the Invention

[0005] The purpose of the present invention aims at the deficiencies of the prior art and provides a trifunctional electrocatalytic material, a preparation method thereof, and an application thereof.

[0006] The first purpose of the present invention is to provide a trifunctional electrocatalytic material, which is a trifunctional carbon material that simultaneously catalyzes the oxygen reduction reaction, the hydrogen evolution reaction, and the oxygen evolution reaction.

[0007] The second purpose of the present invention is to provide a preparation method of the above-mentioned trifunctional electrocatalytic material. The preparation method is simple to operate and solves the problems of high cost and low reserves of noble metal catalysts in the prior art.

[0008] The third object of the present invention is to provide a use of the above-mentioned trifunctional electrocatalytic material, which is applied in the catalytic oxygen reduction reaction, hydrogen evolution reaction and oxygen evolution reaction, and has excellent electrocatalytic performance.

[0009] The fourth object of the present invention is to provide another use of the above-mentioned trifunctional electrocatalytic material, which is applied in the field of electrocatalytic energy conversion and storage.

[0010] The technical solution of the present invention is realized as follows:

[0011] A preparation method of a trifunctional electrocatalytic material includes the following steps:

[0012] (1) Ultrasonically disperse humic acid evenly in deionized water, add cobalt salt and stir, and then perform freeze-drying to obtain a precursor;

[0013] (2) Calcinate the precursor obtained by freeze-drying in step (1) at high temperature, perform acid washing and then nitrogen doping to obtain a trifunctional electrocatalytic material.

[0014] For the preparation method of a trifunctional electrocatalytic material as described above, in step (1), the concentration of the humic acid in deionized water is 0.05 - 0.2 g / mL.

[0015] For the preparation method of a trifunctional electrocatalytic material as described above, the cobalt salt is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0016] For the preparation method of a trifunctional electrocatalytic material as described above, in step (1), the mass ratio of the cobalt salt to the humic acid is (1 - 3):(1 - 3).

[0017] For the preparation method of a trifunctional electrocatalytic material as described above, in step (1), the power of the ultrasonic wave is 220 - 280 W, and the ultrasonic time is 5 - 20 min.

[0018] For the preparation method of a trifunctional electrocatalytic material as described above, in step (1), the conditions of the freeze-drying are: drying at -70 - 90 °C for 20 - 24 h.

[0019] For the preparation method of a trifunctional electrocatalytic material as described above, in step (2), the conditions of the high-temperature calcination, acid washing and nitrogen doping are: in a nitrogen atmosphere, heating at a heating rate of 5 °C / min to 700 - 1000 °C and holding for 2 - 3.5 h, then cooling, and performing acid washing with a 1.5 - 2.5 M HCl solution at 85 - 95 °C for 22 - 26 h, and then in an ammonia atmosphere, holding at 750 - 850 °C for 0.5 - 1.5 h, and then cooling to obtain a trifunctional electrocatalytic material.

[0020] Based on the same inventive concept, the present invention also provides a trifunctional electrocatalytic material, which is obtained by using the preparation method of a trifunctional electrocatalytic material as described above.

[0021] Based on the same inventive concept, the present invention also provides an application of a trifunctional electrocatalytic material in catalyzing oxygen reduction reaction, hydrogen evolution reaction and oxygen evolution reaction.

[0022] Based on the same inventive concept, the present invention also provides an application of a trifunctional electrocatalytic material in the field of electrocatalytic energy conversion and storage.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The preparation method of a trifunctional electrocatalytic material provided by the present invention utilizes the synergistic effect of Co nanoparticles and Co-N-C to simultaneously catalyze oxygen reduction, hydrogen evolution and oxygen evolution reactions, realizing the improvement of the catalytic activity and stability of the material. Among them, the half-wave potential of ORR can reach 0.85 V, OER can reach 1.61 V@10 mA cm -2 , and HER can reach -0.1 V@10 mA cm -2 .

[0025] 2. The preparation method of a trifunctional electrocatalytic material provided by the present invention uses a nitrogen-doped non-metal-based carbon material to prepare a trifunctional electrocatalytic carbon material that can simultaneously catalyze oxygen reduction, hydrogen evolution and oxygen evolution reactions, solving the problems of high cost, low reserves and poor stability of noble metal catalysts in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a scanning electron microscope image of a trifunctional electrocatalytic material prepared in Example 1 of the present invention;

[0027] Figure 2 is a linear sweep polarization curve graph of ORR (a), OER (b) and HER under 1M KOH (c) in Examples 1-3 of the present invention;

[0028] Figure 3 is a linear sweep polarization curve graph of ORR (a), OER (b) and HER (c) under 1M KOH in Examples 1, Comparative Examples 1-2 of the present invention;

[0029] Figure 4 is a comparison graph of the anti-methanol poisoning experiment of the commercial noble metal catalyst Pt / C in Example 1 of the present invention and Comparative Example 3;

[0030] Figure 5 is a comparison graph of the ORR stability of the commercial noble metal catalyst Pt / C in Example 1 of the present invention and Comparative Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the content in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0033] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified.

[0034] The materials, reagents, etc. used in the following embodiments can be obtained from commercial sources unless otherwise specified.

[0035] A preparation method of a trifunctional electrocatalytic material includes the following steps:

[0036] (1) Ultrasonically disperse humic acid evenly in deionized water, add cobalt salt and stir, and then perform freeze-drying to obtain a precursor.

[0037] (2) Calcinate the precursor obtained by freeze-drying in step (1) at high temperature, perform acid washing and then nitrogen doping to obtain a trifunctional electrocatalytic material.

[0038] The technical principle of the present invention is as follows: Humic acid can coordinate with cobalt ions to avoid the agglomeration of metallic cobalt during calcination and increase the active sites for catalytic reactions. In addition, humic acid can undergo strong metal-support interactions with cobalt as a carbon substrate, enhancing the catalytic activity and stability of the catalyst. Preferably, the cobalt salt is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate. More preferably, the cobalt salt is cobalt chloride. Cobalt chloride as a metallic cobalt source can provide active sites for catalytic reactions, contributing to enhancing catalytic activity. Metallic cobalt also helps to improve the graphitization degree of carbon and enhance the conductivity of the catalyst. Freeze-drying can endow the catalyst with a rich specific surface area and pore structure, thereby providing abundant active sites during the catalytic process. Acid washing can remove unstable metal particles and relatively large particles, providing a porous structure. Thereby, the catalytic activity and stability of the catalyst can be improved. The catalyst in the present invention has a structure of heteroatom-doped carbon coupled with cobalt, and the electronic interaction between the carbon support and the metal can optimize the catalytic reaction path and enhance the catalytic activity.

[0039] Preferably, in the step (1), the concentration of the humic acid in deionized water is 0.05 - 0.2 g / mL. More preferably, in the step (1), the concentration of the humic acid in deionized water is 0.15 - 0.2 g / mL. Most preferably, in the step (1), the concentration of the humic acid in deionized water is 0.15 g / mL.

[0040] More preferably, in the step (1), the mass ratio of cobalt chloride to humic acid is (1 - 3):(1 - 3). Most preferably, in the step (1), the mass ratio of cobalt chloride to humic acid is 3:1. Under this condition, cobalt metal can be evenly loaded on the carbon material to form a Co-N-C material with good catalytic performance. If the mass ratio of cobalt chloride to humic acid is greater than 3:1, too high cobalt content will cause cobalt particles to agglomerate, resulting in a reduction of catalytic sites; if the mass ratio of cobalt chloride to humic acid is less than 3:1, too low cobalt content will not achieve good catalytic performance.

[0041] Preferably, in the step (1), the power of the ultrasonic wave is 220 - 280 W, and the ultrasonic time is 5 - 20 min. More preferably, in the step (1), the power of the ultrasonic wave is 220 - 280 W, and the ultrasonic time is 5 - 15 min. Most preferably, in the step (1), the power of the ultrasonic wave is 220 W, and the ultrasonic time is 15 min. Under this condition, the humic acid can form a homogeneous liquid, which is more conducive to the dispersion of cobalt salt.

[0042] Preferably, in the step (1), the conditions for freeze-drying are: drying at -70 - 90 °C for 20 - 24 h. Preferably, in the step (1), the conditions for freeze-drying are: drying at -80 - 90 °C for 20 - 24 h. Most preferably, in the step (1), the conditions for freeze-drying are: drying at -80 °C for 24 h. Under this condition, a loose porous structure can be quickly formed, and the morphology and structure of the sample can be well maintained.

[0043] Preferably, in the step (2), the conditions for high-temperature calcination, pickling, and nitrogen doping are as follows: in a nitrogen atmosphere, the temperature is raised to 700 - 1000 °C at a heating rate of 5 °C / min and maintained for 2 - 3.5 h, then cooled, and pickled with a 1.5 - 2.5 M HCl solution at 85 - 95 °C for 22 - 26 h. Then, in an ammonia atmosphere, the temperature is maintained at 750 - 850 °C for 0.5 - 1.5 h, and then cooled to obtain a trifunctional electrocatalytic material. More preferably, in the step (2), the conditions for high-temperature calcination, pickling, and nitrogen doping are as follows: in a nitrogen atmosphere, the temperature is raised to 750 - 850 °C at a heating rate of 5 °C / min and maintained for 2 - 3.5 h, then cooled, and pickled with a 1.5 - 2.5 M HCl solution at 85 - 95 °C for 22 - 26 h. Then, in an ammonia atmosphere, the temperature is maintained at 750 - 850 °C for 1 - 1.5 h, and then cooled to obtain a trifunctional electrocatalytic material. Most preferably, the conditions for high-temperature calcination, pickling, and nitrogen doping are as follows: in a nitrogen atmosphere, the temperature is raised to 800 °C at a heating rate of 5 °C / min and maintained for 2 h, then cooled, and pickled with a 2 M HCl solution at 90 °C for 24 h. Then, in an ammonia atmosphere, the temperature is maintained at 800 °C for 1 h, and then cooled to obtain a trifunctional electrocatalytic material. Under these conditions, high-temperature calcination can improve the graphitization degree of the carbon support, enhance the conductivity of the catalyst, and strengthen the interaction between the metal and the carbon support, thereby improving the activity and stability of the catalyst. The cooling in this step of the present invention is natural cooling.

[0044] Based on the same inventive concept, the present invention also provides a trifunctional electrocatalytic material prepared by using the preparation method of a trifunctional electrocatalytic material as described above. The material prepared by the present invention has a large number of pore structures, which is beneficial to the mass transfer during the electrocatalytic reaction and the exposure of active sites.

[0045] Based on the same inventive concept, the present invention also provides an application of a trifunctional electrocatalytic material in the catalytic oxygen reduction reaction, hydrogen evolution reaction, and oxygen evolution reaction.

[0046] Based on the same inventive concept, the present invention also provides an application of a trifunctional electrocatalytic material in the field of electrocatalytic energy conversion and storage.

[0047] To further understand the present application, the following examples are used to specifically describe a trifunctional electrocatalytic material and its preparation method provided by the present invention.

[0048] Example 1

[0049] (1) Ultrasonically disperse 3 g of humic acid evenly in 20 mL of deionized water, add 9 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W, and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -80 °C for 24 h;

[0050] (2) Under a nitrogen atmosphere, heat the freeze-dried precursor at a heating rate of 5 °C / min to 800 °C and hold for 2 h, then cool down, and perform pickling with 2 M HCl solution at 90 °C for 24 h. Then, under an ammonia atmosphere, hold at 800 °C for 1 h and cool down to obtain a trifunctional electrocatalytic material.

[0051] Example 2

[0052] (1) Ultrasonically disperse 3 g of humic acid evenly in 20 mL of deionized water, add 3 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W, and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -80 °C for 24 h;

[0053] (2) Under a nitrogen atmosphere, heat the freeze-dried precursor at a heating rate of 5 °C / min to 800 °C and hold for 2 h, then cool down, and perform pickling with 2 M HCl solution at 90 °C for 24 h. Then, under an ammonia atmosphere, hold at 800 °C for 1 h and cool down to obtain a trifunctional electrocatalytic material.

[0054] Example 3

[0055] (1) Ultrasonically disperse 3 g of humic acid evenly in 20 mL of deionized water, add 6 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W, and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -80 °C for 24 h;

[0056] (2) Under a nitrogen atmosphere, heat the freeze-dried precursor at a heating rate of 5 °C / min to 800 °C and hold for 2 h, then cool down, and perform pickling with 2 M HCl solution at 90 °C for 24 h. Then, under an ammonia atmosphere, hold at 800 °C for 1 h and cool down to obtain a trifunctional electrocatalytic material.

[0057] Example 4

[0058] (1) Ultrasonically disperse 3 g of humic acid evenly in 20 mL of deionized water, add 9 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W, and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -90 °C for 20 h;

[0059] (2) The freeze-dried precursor was heated to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and held for 2 h, then cooled down. It was pickled with 2 M HCl solution at 90 °C for 24 h, and then held at 800 °C for 1 h in an ammonia atmosphere and cooled down to obtain a trifunctional electrocatalytic material.

[0060] Example 5

[0061] (1) 3 g of humic acid was ultrasonically dispersed evenly in 20 mL of deionized water, 9 g of cobalt chloride was added and stirred, and then freeze-dried to obtain a precursor. In this example, the power of ultrasonic wave was 220 W and the ultrasonic time was 15 minutes. The conditions for freeze-drying were: drying at -80 °C for 24 h;

[0062] (2) The freeze-dried precursor was heated to 850 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and held for 2 h, then cooled down. It was pickled with 2 M HCl solution at 90 °C for 24 h, and then held at 850 °C for 1 h in an ammonia atmosphere and cooled down to obtain a trifunctional electrocatalytic material.

[0063] Example 6

[0064] (1) 3 g of humic acid was ultrasonically dispersed evenly in 20 mL of deionized water, 9 g of cobalt chloride was added and stirred, and then freeze-dried to obtain a precursor. In this example, the power of ultrasonic wave was 220 W and the ultrasonic time was 15 minutes. The conditions for freeze-drying were: drying at -80 °C for 24 h;

[0065] (2) The freeze-dried precursor was heated to 750 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and held for 2 h, then cooled down. It was pickled with 2 M HCl solution at 90 °C for 24 h, and then held at 750 °C for 1.5 h in an ammonia atmosphere and cooled down to obtain a trifunctional electrocatalytic material.

[0066] Example 7

[0067] (1) 3 g of humic acid was ultrasonically dispersed evenly in 20 mL of deionized water, 9 g of cobalt chloride was added and stirred, and then freeze-dried to obtain a precursor. In this example, the power of ultrasonic wave was 280 W and the ultrasonic time was 5 minutes. The conditions for freeze-drying were: drying at -80 °C for 24 h;

[0068] (2) The freeze-dried precursor was heated to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and held for 2 h, then cooled down. It was pickled with 2 M HCl solution at 90 °C for 24 h, and then held at 800 °C for 1 h in an ammonia atmosphere and cooled down to obtain a trifunctional electrocatalytic material.

[0069] Example 8

[0070] (1) Ultrasonically disperse 3 g of humic acid evenly in 15 mL of deionized water, add 9 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -80 °C for 24 h;

[0071] (2) Under a nitrogen atmosphere, heat the freeze-dried precursor at a heating rate of 5 °C / min to 800 °C and hold for 2 h, then cool down, and perform pickling with 2 M HCl solution at 90 °C for 24 h. Then, under an ammonia atmosphere, hold at 800 °C for 1 h and cool down to obtain a trifunctional electrocatalytic material.

[0072] Comparative Example 1

[0073] (1) Ultrasonically disperse 3 g of humic acid evenly in 20 mL of deionized water, add 9 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -80 °C for 24 h;

[0074] (2) Under a nitrogen atmosphere, heat the freeze-dried precursor at a heating rate of 5 °C / min to 700 °C and hold for 2 h, then cool down, and perform pickling with 2 M HCl solution at 90 °C for 24 h. Then, under an ammonia atmosphere, hold at 700 °C for 1 h and cool down to obtain the electrocatalytic material of this comparative example.

[0075] Comparative Example 2

[0076] (1) Ultrasonically disperse 3 g of humic acid evenly in 20 mL of deionized water, add 9 g of cobalt chloride and stir, then perform freeze-drying to obtain a precursor; in this example, the power of ultrasonic treatment is 220 W and the ultrasonic time is 15 minutes; the conditions for freeze-drying are: drying at -80 °C for 24 h;

[0077] (2) Under a nitrogen atmosphere, heat the freeze-dried precursor at a heating rate of 5 °C / min to 800 °C and hold for 2 h, then cool down, and perform pickling with 2 M HCl solution at 90 °C for 24 h to obtain the electrocatalytic material of this comparative example.

[0078] Comparative Example 3

[0079] Commercial noble metal catalyst Pt / C, purchased from Aladdin, CAS No. 7440-06-4.

[0080] Disperse the above-prepared catalyst material in a mixed solution of 0.3 mL of ethanol, 0.15 mL of ultrapure water and 0.06 mL of Nafion colloidal solution, and perform ultrasonic treatment for 20 min to obtain 0.51 mL of ink solution for standby.

[0081] Using a three - electrode test system, ORR, OER, and HER electrocatalytic performance tests were carried out in electrolyte solutions of 0.1 M KOH, 1 M KOH, and 1 M KOH respectively through a Chenhua CHI760E electrochemical workstation.

[0082] The test conditions are as follows:

[0083] ORR test: The test was carried out using a three - electrode system. The three electrodes were a platinum wire as the counter electrode, a saturated Ag / AgCl electrode as the reference electrode, and a rotating ring - disk electrode as the working electrode. 5 μl of the ink was dropped onto the ring - disk electrode with an area of 0.1256 cm 2 . After natural drying at room temperature, the prepared electrode was assembled into the rotating ring - disk electrode device. Before the test, pure oxygen was passed into the electrolyte for 30 min and the oxygen supply was maintained. The sweep rate was set to 10 mV s -1 , and the scanning range was set to 0.3 V - 1.05 V (vs RHE). The rotation speed was set to 400 rpm - 1600 rpm.

[0084] OER test: The test was carried out using a three - electrode system. The three electrodes were a carbon rod as the counter electrode, a reversible hydrogen electrode as the reference electrode. 40 μL of the ink was dropped onto a glassy carbon electrode with an area of 0.07065 cm 2 and dried naturally as the working electrode. The test environment was 1 M KOH solution, and the polarization curve was tested at a scanning rate of 10 mV s -1 within the potential range of 1.0 V - 2.0 V (vs RHE).

[0085] HER test: The test was carried out using a three - electrode system. The three electrodes were a carbon rod as the counter electrode, a reversible hydrogen electrode as the reference electrode. 5 μL of the ink was dropped onto a glassy carbon electrode with an area of 0.07065 cm 2 and dried naturally as the working electrode. The test environment was 1 M KOH solution, and the polarization curve was tested at a scanning rate of 10 mV s -1 within the potential range of - 0.6 V - 0.1 V (vs RHE).

[0086] Figure 1 This is the scanning electron microscope image of a trifunctional electrocatalytic material prepared in Example 1 of the present invention. From Figure 1 it can be seen that the material prepared in the example of the present invention has more pore structures, which is beneficial to the mass transfer during the electrocatalytic reaction and the exposure of active sites.

[0087] Figure 2 This is the linear sweep polarization curve graph of ORR (a), OER (b), and HER under 1 M KOH (c) in Examples 1 - 3 of the present invention. From Figure 2As can be seen, the ORR half-wave potential of Example 1 reached 0.85 V, and the OER could reach 1.61 V@10 mA cm -2 , and the HER could reach -0.1 V@10 mA cm -2 , all showing relatively high catalytic activities, indicating that the dosage of cobalt chloride has a significant effect on the catalytic performance of the material.

[0088] Figure 3 This is the linear sweep polarization curve graph of ORR (a), OER (b) and HER (c) under 1 M KOH for Example 1 and Comparative Examples 1-2 of the present invention. As can be seen from Figure 3 it, Example 1 still shows the optimal catalytic activity, indicating that the doping of nitrogen element and the pyrolysis temperature of 800 °C have a strong influence on the performance of the material. For ORR, the half-wave potentials of Comparative Example 1 and Comparative Example 2 are at 0.8 V, while the half-wave potential of Example 1 reached 0.85 V, reflecting the influence of nitrogen doping on the catalytic ORR activity of the material, and also reflecting the synergistic effect of Co particles, Co-N-C and nitrogen-doped carbon. Similarly, the overpotentials corresponding to the current densities of OER and HER in Comparative Example 1 and Comparative Example 2 at 10 mA cm -2 are much higher than those of Example 1, which is not conducive to the progress of the catalytic reaction, and once again reflects the trifunctional high catalytic activity of the material prepared by the present invention.

[0089] Figure 4 This is the comparison graph of the methanol tolerance experiment of the commercial noble metal catalyst Pt / C of Example 1 and Comparative Example 3 of the present invention. As can be seen from Figure 4 it, after adding methanol, the current of the trifunctional electrocatalytic material prepared in Example 1 of the present invention does not fluctuate much, but the current of Pt / C changes significantly and the current drops rapidly, indicating that the material prepared by the present invention has good methanol tolerance.

[0090] Figure 5 This is the comparison graph of the ORR stability of the commercial noble metal catalyst Pt / C of Example 1 and Comparative Example 3 of the present invention. As can be seen from Figure 5 it, the trifunctional electrocatalytic material prepared in Example 1 of the present invention is slightly better than the ORR stability of the commercial noble metal catalyst Pt / C. That is to say, the stability of the trifunctional electrocatalytic material prepared in Example 1 of the present invention can reach or even exceed the ORR stability of the commercial noble metal catalyst Pt / C, but the cost is much lower than that of the commercial noble metal catalyst Pt / C.

[0091] The preparation method of a three-functional electrocatalytic material provided by the present invention utilizes the synergistic effect of Co nanoparticles and Co-N-C to simultaneously catalyze the oxygen reduction reaction, hydrogen evolution reaction, and oxygen evolution reaction, achieving an improvement in the catalytic activity and stability of the material. The present invention uses a nitrogen-doped non-metallic carbon material to prepare a three-functional electrocatalytic carbon material that can simultaneously catalyze the oxygen reduction reaction, hydrogen evolution reaction, and oxygen evolution reaction, solving the problems of high cost, low reserves, and poor stability of noble metal catalysts in the prior art.

[0092] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a trifunctional electrocatalytic material, characterized in that, It includes the following steps: (1) Ultrasonically disperse humic acid uniformly in deionized water, add cobalt salt and stir, and then perform freeze-drying to obtain a precursor; the power of the ultrasonic treatment is 220 - 280 W, and the ultrasonic time is 5 - 15 min; the mass ratio of the cobalt salt to humic acid is (1 - 3):(1 - 3); (2) Calcinate the precursor after freeze-drying in step (1) at high temperature, perform pickling and then nitrogen doping; in step (2), the conditions for the high-temperature calcination, pickling and nitrogen doping are as follows: under a nitrogen atmosphere, heat up to 750 - 850 °C at a heating rate of 5 °C / min and hold for 2 - 3.5 h, cool down, and perform pickling with 1.5 - 2.5 M HCl solution at 85 - 95 °C for 22 - 26 h, and then under an ammonia atmosphere, hold at 750 - 850 °C for 1 - 1.5 h, cool down to obtain a trifunctional electrocatalytic material.

2. The preparation method of a trifunctional electrocatalytic material according to claim 1, characterized in that, In step (1), the concentration of the humic acid in deionized water is 0.05 - 0.2 g / mL.

3. The preparation method of a trifunctional electrocatalytic material according to claim 1, wherein, In step (1), the cobalt salt is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate.

4. The preparation method of a trifunctional electrocatalytic material according to claim 2, wherein, In step (1), the conditions for the freeze-drying are: drying at -70 - 90 °C for 20 - 24 h.

5. A three-functional electrocatalytic material, characterized in that, It is prepared by using the preparation method of a trifunctional electrocatalytic material described in any one of claims 1 to 4.

6. Application of the trifunctional electrocatalytic material prepared by the preparation method of the trifunctional electrocatalytic material described in any one of claims 1 to 4 or the trifunctional electrocatalytic material described in claim 5 in the catalytic oxygen reduction reaction, hydrogen evolution reaction, and oxygen evolution reaction.

7. Application of the trifunctional electrocatalytic material prepared by the preparation method of the trifunctional electrocatalytic material described in any one of claims 1 to 4 or the trifunctional electrocatalytic material described in claim 5 in the field of electrocatalytic energy conversion and storage.

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