A sea urchin-like material, its preparation method and uses

Abstract

This invention discloses a sea urchin-like material, which is spherical in shape with a diameter of 3.0-6.0 μm. The outer periphery of the spherical sea urchin-like shape is composed of nanotubes. Small spheres with a core-shell structure are uniformly embedded within the matrix of the spherical sea urchin-like material and on the tops of some nanotubes. This invention also discloses a method for preparing the sea urchin-like material and its application in the electrocatalytic two-electron oxygen reduction reaction to prepare hydrogen peroxide electrode materials. The sea urchin-like material of this invention exhibits superior electrocatalytic two-electron oxygen reduction performance.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology, specifically relating to a sea urchin-like material, its preparation method, and its use as an electrode material for the electrocatalytic two-electron oxygen reduction reaction to prepare hydrogen peroxide. Background Technology

[0002] Hydrogen peroxide, a common oxidant, is widely used in medical disinfection and wastewater treatment. In recent years, oxygen reduction reactions based on the two-electron pathway, with their sustainable in-situ production advantages, have shown promise as a replacement for the energy-intensive anthraquinone process, enabling cleaner hydrogen peroxide production. Carbon materials, as typical electrocatalysts, possess advantages such as abundant surface active sites, fast electron transport speed, and high stability. However, the hydrogen peroxide production under pure carbon catalysis is relatively low, and most allotropes of carbon materials tend to follow the four-electron pathway, generating the competing product water, reducing reaction selectivity and significantly limiting their application in electrocatalytic hydrogen peroxide production (see Chemical Engineering Journal 2024, 479; Applied Catalysis B: Environmental 2022, 307; and Applied Catalysis B: Environmental 2024, 341). By combining carbon materials with low-cost, abundant transition metals, the advantages of high conductivity of carbon materials and high activity and selectivity of transition metal materials are combined. The electron distribution around the active site is adjusted by the metal-carrier interaction, thereby regulating the binding strength between the active site and the intermediate product *OOH. This enables the production of hydrogen peroxide with high activity, high selectivity and high stability.

[0003] Currently, various strategies for improving the catalytic performance of transition metal-carbon composites have been reported to achieve efficient hydrogen peroxide production, such as heteroatom doping and morphology control. However, the construction of electrocatalysts based on metal-coated core-shell structures for hydrogen peroxide production remains largely unreported. Efficient hydrogen peroxide production can be achieved by anchoring metal phosphide core-shell heterostructures onto carbon nanosheets through the carbonization and phosphating of two-dimensional nickel-based precursors (see Small Methods, 2024, 2301560). Structures with coated nickel metal particles can also be constructed using three-dimensional porous carbon-derived melamine foam as a substrate (see Journal of Materials Chemistry A, 2023, 11, 10204-10212). The choice of precursor is crucial in the construction of core-shell structures. Metal-organic frameworks (MOFs) can form stable structures with uniform metal distribution and large carbon framework extension areas through the self-assembly of inorganic metal centers and ligands; by introducing additional compounds, it is hoped that catalysts with specific structures can be synthesized. In this process, simplifying the catalyst preparation process and reducing the types of reactants are key to the efficient electrocatalytic production of hydrogen peroxide. Further research is needed on the control of core-shell structure morphology and shell thickness, as well as the synergistic effect between the outer carbon layer and the inner metal.

[0004] The present invention is proposed to solve the above problems. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a spherical sea urchin-like material and its preparation method, and applies the spherical sea urchin-like material of this invention to the field of electrocatalytic two-electron oxygen reduction reaction electrode materials. The preparation method of this invention uses MOF as a precursor, synthesizing a sea urchin-like material rich in nanotubes through hydrothermal and two-stage calcination. The preparation method of this invention uses a nanoflower-like nickel-based metal-organic framework (Ni-MOF) as an intermediate, obtaining a spherical sea urchin-like structure material rich in nitrogen-doped carbon nanotubes through the addition of melamine and two-stage calcination; melamine, as an additional carbon and nitrogen source, decomposes into carbon fragments and generates reducing gas NH3 during calcination, thus nitrogen-doping the carbon structure; the calcined product retains the overall spherical structure of Ni-MOF, and during calcination, due to the reducing atmosphere of hydrogen, argon, ammonia, etc., Ni… 2+The material is reduced to Ni metal particles, which are then encapsulated in situ by a nitrogen-doped carbon layer, forming a core-shell structure with Ni metal particles as the core and the nitrogen-doped carbon layer as the shell. The thickness of the nitrogen-doped carbon layer is adjustable from 5 to 15 nm. The Ni metal particles catalyze the formation of carbon nanotube structures, extending outwards to form dense nitrogen-doped carbon nanotubes with a length of 40-150 nm and a diameter of 10-20 nm, distributed on the outer periphery of the spherical sea urchin-shaped material. The nitrogen-doped carbon nanotubes are uniformly distributed on the surface of the spherical sea urchin-shaped material. Furthermore, TEM analysis revealed that small spheres with core-shell structures are uniformly embedded at the tips of some nanotubes and inside the spherical carbon matrix. The preparation method of this invention can effectively control the morphology of the spherical sea urchin-shaped material, especially the shell thickness of the small spheres with core-shell structures, by changing the amount of melamine. The obtained material is used as an electrode material for the electrocatalytic two-electron oxygen reduction reaction to prepare hydrogen peroxide, which can promote the electron and mass transfer process, optimize the binding energy of the intermediate *OOH, and achieve efficient preparation of hydrogen peroxide.

[0006] The technical solution of this invention is as follows:

[0007] The first aspect of the present invention discloses a sea urchin-like material, wherein the material is spherical in shape and has a diameter of 3.0-6.0 μm; the outer periphery of the spherical sea urchin shape is composed of nanotubes; and small spheres with a core-shell structure are uniformly embedded in the matrix of the spherical sea urchin-like material and on the top of some nanotubes.

[0008] Preferably, the diameter of the core in the core-shell structure is 10-100 nm; and the thickness of the shell layer in the core-shell structure is 5-15 nm.

[0009] Preferably, the nanotubes have a length of 40-150 nm and a diameter of 10-20 nm.

[0010] Preferably, the material is composed of nitrogen-doped carbon; the core of the core-shell structure is a Ni metal particle, and the shell of the core-shell structure is also nitrogen-doped carbon.

[0011] Preferably, the material has the following composition: Ni is (2-15) at%, C is (80-90) at%, and N is (1.5-6.0) at%. at% is atomic percentage.

[0012] The second aspect of this invention discloses a method for preparing the sea urchin-like material, comprising the following steps:

[0013] (1) Preparation of Ni-MOF: A certain amount of N,N-dimethylformamide, anhydrous ethanol and deionized water are mixed evenly to obtain solution A; a certain amount of terephthalic acid and nickel chloride hexahydrate are dissolved in solution A in sequence to obtain solution B; solution B is sonicated for a period of time and reacted at 160℃ for 12h, separated and washed 3-4 times, and then freeze-dried to obtain the Ni-MOF;

[0014] (2) Preparation of Ni-MOF and melamine mixture: Ni-MOF and melamine obtained in step (1) are dispersed in anhydrous ethanol in a certain proportion, mixed at a certain temperature for a period of time, and then the ethanol is evaporated by heating to obtain solid.

[0015] (3) Preparation of sea urchin-like material: The solid obtained in step (2) is heated to 525-550℃ in a mixed atmosphere of hydrogen and argon for 2-3 hours for the first stage of calcination; then the temperature is further increased to 1000-1200℃ for 2-3 hours for the second stage of calcination; thus, the sea urchin-like material is obtained.

[0016] Preferably, in step (2), the mass ratio of Ni-MOF to melamine is 1:(1-3); first, the mixture is stirred at 25°C for 10-20 hours, and then the temperature is raised to 60°C and the mixture is stirred until the ethanol evaporates.

[0017] Preferably, in step (3), the first stage of calcination uses a hydrogen to argon volume ratio of 1:9, a flow rate of 100-200 sccm, a temperature of 550℃, a heating rate of 2℃ / min, and a holding time of 2h; the second stage of calcination uses a temperature of 1100℃, a heating rate of 3℃ / min, and a holding time of 3h.

[0018] The third aspect of this invention discloses the use of the sea urchin-like material in the preparation of hydrogen peroxide electrode material for the electrocatalytic two-electron oxygen reduction reaction.

[0019] The beneficial effects of this invention are:

[0020] 1. The sea urchin-like material of the present invention comprises core-shell structured spheres, wherein the core is a Ni metal particle and the shell is a nitrogen-doped carbon layer with an adjustable thickness of 5-15 nm. The core-shell structured spheres are uniformly embedded within the carbon matrix and at the tips of some nanotubes. Compared with existing core-shell structured nitrogen-doped carbon materials, the core-shell structured spheres of the present invention are more stable. The sea urchin-like material of the present invention, used as an electrode material for preparing hydrogen peroxide, exhibits excellent two-electron oxygen reduction performance; the nitrogen-doped shell carbon and the internal nickel metal particle of the core-shell structured spheres fully cooperate, resulting in optimal binding energy strength of *OOH at the active site, achieving hydrogen peroxide selectivity exceeding 90% over a wide potential window, stability exceeding 10 hours, and a hydrogen peroxide production effect of nearly 800 mg / L within 2 hours. The material of this invention combines the advantages of carbon materials and transition metal materials. It leverages the high conductivity and stability of traditional carbon materials, and when combined with transition metals, it synergistically improves the electronic states around the active sites through metal-carrier interactions, giving the material higher hydrogen peroxide selectivity and activity. Furthermore, the formation of the core-shell structure effectively prevents the escape of internal metal particles, resulting in a relatively stable structure.

[0021] 2. The preparation method of the sea urchin-like material of the present invention uses a metal-organic framework material as the precursor, which has a rich porous structure. Compared with conventional zeolite imidazole ester (ZIF) framework materials, the sea urchin-like material of the present invention has a more stable structure. The preparation method of the present invention uses hydrothermal and two-stage calcination, which is simple, quick, and uses relatively few types of raw materials. After the raw materials are mixed evenly, the first stage of calcination allows melamine to be better converted into a g-C3N4 structure through polyaddition and thermal polymerization reactions. The second stage of calcination forms a dispersed nanotube morphology. The material obtained by the preparation method of the present invention is used to prepare electrode materials for hydrogen peroxide, which better promotes electron and mass transfer, facilitates the full diffusion of reactant oxygen and reaction product hydrogen peroxide, and provides a more suitable environment for the formation of intermediate *OOH.

[0022] 3. The preparation method of the sea urchin-like material of the present invention provides an effective means of adjusting the shell thickness of the core-shell structure by adjusting the amount of melamine added. The preparation method of the present invention synthesizes spherical sea urchin-like materials with nanotubes of different densities on the periphery, and small spheres with a core-shell structure are uniformly embedded in the matrix of the spherical sea urchin-like material and on the top of some nanotubes; thereby changing the electron density distribution inside and outside the core-shell structure small spheres, achieving precise control from carbon layer thickness to electrocatalytic performance, and clarifying the structure-activity relationship between morphology and performance. Melamine plays multiple roles in the preparation of the material of the present invention: in terms of morphology, it provides an additional carbon and nitrogen source to support nanotube growth; at high temperature, it decomposes to generate NH3 to reduce metal ions for nucleation; during calcination, it achieves nitrogen doping of the outer carbon layer, further regulating the electron distribution state around the active sites. Attached Figure Description

[0023] Figure 1 This is a SEM image of the Ni-MOF obtained in Example 1.

[0024] Figure 2 The images are SEM images of Ni@C (a), Ni@NCNTs-1 (b), Ni@NCNTs-1.5 (c) and Ni@NCNTs-3 (d) obtained in Comparative Example 1 and Examples 1-3.

[0025] Figure 3 These are TEM images of Ni@C (a), Ni@NCNTs-1 (b), Ni@NCNTs-1.5 (c), and Ni@NCNTs-3 (d) obtained in Comparative Example 1 and Examples 1-3.

[0026] Figure 4 These are TEM images of Ni@C (a), Ni@NCNTs-1 (b), Ni@NCNTs-1.5 (c), and Ni@NCNTs-3 (d) with different carbon layer thicknesses obtained in Comparative Example 1 and Examples 1-3.

[0027] Figure 5 The images show the XRD patterns of Ni@C, Ni@NCNTs-1, Ni@NCNTs-1.5, and Ni@NCNTs-3 obtained in Comparative Example 1 and Examples 1-3.

[0028] Figure 6 The graphs show the performance of the materials obtained in Comparative Example 1 and Examples 1-3 in the electrocatalytic two-electron oxygen reduction reaction, corresponding to the polarization curve (a) and selectivity curve (b) of the rotating ring disk electrode.

[0029] Figure 7 The graphs (a) and (b) show the stability of the electrocatalytic two-electron oxygen reduction reaction and the hydrogen peroxide production obtained in Example 1. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be noted that the examples described below are only used to illustrate and explain the present invention in detail, and the application scope of the present invention is not limited by the conditions in the examples.

[0031] Example 1

[0032] Step 1: Preparation of Ni-MOF: Mix 32 mL of N,N-dimethylformamide, 2 mL of anhydrous ethanol, and 2 mL of deionized water thoroughly to obtain solution A; dissolve 0.1246 g of terephthalic acid and 0.2229 g of nickel chloride hexahydrate sequentially in solution A to obtain solution B; sonicate solution B for 30 min, then transfer it to a sealed autoclave and react at 160 °C for 12 h. Then centrifuge in 70% ethanol aqueous solution (first at 10000 rpm, then at 6000 rpm) 3-4 times for separation and washing; freeze-dry to obtain Ni-MOF.

[0033] The obtained SEM images of Ni-MOF are as follows Figure 1 As shown, it exhibits a spherical nanoflower morphology.

[0034] Step 2: Preparation of a uniformly dispersed Ni-MOF and melamine mixture: Take 0.2g of Ni-MOF obtained in Step 1 and 0.3g of melamine and disperse them in 50mL of anhydrous ethanol. Transfer the mixture to a heating mantle and stir at 25℃ for 12h. Then raise the temperature to 60℃ and continue stirring until the ethanol evaporates to dryness.

[0035] Step 3: Preparation of sea urchin-like material: The mixture obtained in Step 2 was loaded into a quartz boat and then placed in the quartz tube of a tube furnace; the temperature was increased to 550℃ at a heating rate of 2℃ / min under a mixed atmosphere of hydrogen and argon with a volume fraction of 1:9 and held for 2h to fully generate a graphitized carbon nitride structure; the temperature was further increased to 1100℃ at a heating rate of 3℃ / min and held for 3h to form a nitrogen-doped nanotube structure; the obtained material was named Ni@NCNTs-1.5.

[0036] The SEM image of Ni@NCNTs-1.5 obtained from the test is shown below. Figure 2 As shown in c, the obtained material is spherical and urchin-like; the TEM image is as follows. Figure 3 As shown in c and 4c, the spherical sea urchin-like outer periphery is composed of nanotubes, i.e., nitrogen-doped carbon nanotubes are uniformly distributed on the outer periphery of the sea urchin-like material. The length of the nanotubes is about 80 nm and the diameter is about 15 nm. Small spheres with a core-shell structure are uniformly embedded on the top of some nanotubes. The shell thickness of the small spheres with the core-shell structure is about 8.96 nm and the diameter of the core is about 58 nm.

[0037] Comparative Example 1: Same as Example 1, but without the addition of melamine.

[0038] The steps are the same as in Example 1.

[0039] Step 2: Same as Step 3 in Example 1; the obtained material is named Ni@C. The SEM image of Ni@C obtained is shown below. Figure 2 As shown in a; by Figure 2As can be seen from a, compared to the precursor Ni-MOF, the surface of Ni@C is rougher and has metal particle loading, but no nanotube distribution was observed; the TEM image of Ni@C is shown below. Figure 3 As shown in a and 4a; by Figure 3 From a and 4a, we can see that the metal particles have a relatively large diameter, approximately 120 nm; the core-shell structure is not obvious, and the carbon layer thickness is 2.86 nm.

[0040] Example 2

[0041] The steps are the same as in Example 1.

[0042] Step 2: Preparation of a uniformly dispersed Ni-MOF and melamine mixture: Take 0.2g of Ni-MOF obtained in Step 1 and 0.2g of melamine and disperse them in 50mL of anhydrous ethanol. Transfer the mixture to a heating mantle and stir at 25℃ for 12h. Then raise the temperature to 60℃ and continue stirring until the ethanol evaporates to dryness.

[0043] Step 3 is the same as in Example 1; the obtained material is named Ni@NCNTs-1. The SEM image of Ni@NCNTs-1 is shown below. Figure 2 As shown in b, the obtained material is spherical and urchin-like; the TEM image is as follows. Figure 3 As shown in b and 4b, the surface is sparsely distributed with nanotubes; some nanotubes are also uniformly embedded with core-shell structured spheres on their tops. The shell thickness of the core-shell structured spheres is about 5.75 nm, and the diameter of the core is about 46 nm.

[0044] Example 3

[0045] The steps are the same as in Example 1.

[0046] Step 2: Preparation of a uniformly dispersed Ni-MOF and melamine mixture: Take 0.2g of Ni-MOF obtained in Step 1 and 0.6g of melamine and disperse them in 50mL of anhydrous ethanol. Transfer the mixture to a heating mantle and stir at 25℃ for 12h. Then raise the temperature to 60℃ and continue stirring until the ethanol evaporates to dryness.

[0047] Step 3 is the same as in Example 1; the prepared catalyst is named Ni@NCNTs-3; the SEM image of Ni@NCNTs-3 is shown below. Figure 2 As shown in d, the obtained material is spherical and urchin-like; the TEM image is shown below. Figure 3 As shown in d and 4d, the surface is also sparsely distributed with nanotubes; small spheres with core-shell structure are also uniformly embedded on the top of some nanotubes. The shell thickness of the small spheres with core-shell structure is about 11.70 nm, and the diameter of the core is about 58 nm.

[0048] Figure 5The images show the XRD patterns of Ni@C, Ni@NCNTs-1, Ni@NCNTs-1.5, and Ni@NCNTs-3 obtained in Comparative Examples 1 and Examples 1-3. Figure 5 It can be seen that the material composition is graphitic carbon and elemental Ni. Table 1 shows the elemental content of the materials prepared in Examples 1-3 and Comparative Example 1, which was determined by SEM-EDS.

[0049] Table 1 Elemental Content

[0050]

[0051] Example 4: Ni@C, Ni@NCNTs-1, Ni@NCNTs-1.5 and Ni@NCNTs-3 obtained from the comparative example and the example were used for electrocatalytic two-electron oxygen reduction reaction.

[0052] The method is as follows: The activity, selectivity, and stability of the two-electron oxygen reduction reaction were tested on a rotating ring-disc electrode using 0.1M KOH as the electrolyte. An Ag / AgCl electrode was used as the reference electrode, and a platinum mesh as the counter electrode. 5 mg of the materials obtained in Comparative Example 1 and Examples 1-3 were dispersed in 690 μL of water, 300 μL of ethanol, and 10 μL of 5 wt% Nafion solution, respectively, and sonicated for 1 h. 5 μL of the mixture was then drop-cast onto the glassy carbon of the rotating ring-disc electrode as the working electrode, with a mass loading of 0.1 mg / cm³. 2 The voltage is corrected using the following formula: E RHE =E Ag / AgCl +0.059V×pH+0.197V.

[0053] Before measurement, a stable electrochemical environment was achieved by cyclic voltammetry (CV) at a scan rate of 50 mV / s for 10 cycles under a nitrogen atmosphere. Oxygen was then introduced, and the polarization curve was measured using linear sweep voltammetry (LSV), with a ring voltage of 1.4 V, a disk voltage of 0-1 V, and a scan rate of 5 mV / s. The H2O2 selectivity and the number of transferred electrons were determined using the following formula: and Calculate; where N C For platinum ring collection efficiency, I d For disk current, I r It is the loop current.

[0054] The yield of H₂O₂ was tested in an H-type electrolytic cell using 0.1 M KOH as the electrolyte. The materials obtained in Comparative Example 1 and Examples 1-3 were respectively drop-coated onto carbon paper as working electrodes, with a loading of 0.1 mg / cm³. 2 An Ag / AgCl electrode was used as the reference electrode, and a graphite rod as the counter electrode. H₂O₂ was determined and its concentration calculated using cerium ion titration and UV-Vis spectrophotometry. The reaction was based on: 2Ce4+ +H₂O₂→2Ce 3+ 2H + O2; The formula for calculating Faraday efficiency is: Among them, C H2O2 V represents the cumulative concentration of H2O2 in the H pool. cell Where is the volume of the cathode electrolyte, F is the Faraday constant, I is the current magnitude, and t is the test time.

[0055] Figure 6 The figures show the performance of the materials obtained in the proportions and examples for the electrocatalytic two-electron oxygen reduction reaction, corresponding to the polarization curve (a) and selectivity curve (b) of the rotating ring disk electrode. Figure 7 These are the stability graph (a) and hydrogen peroxide production graph (b) of the electrocatalytic two-electron oxygen reduction reaction of the material obtained in Example 1. Figure 6 and Figure 7 It can be seen that the Ni@NCNTs-1.5 material obtained in Example 1 has the best performance in electrocatalytic two-electron oxygen reduction reaction; it has a hydrogen peroxide selectivity of over 90% and a stability of over 10 hours under a wide potential window, and a hydrogen peroxide production effect of nearly 800 mg / L within 2 hours.

[0056] Comparative Example 2

[0057] The method used is the one reported in Small Methods, 2024, 2301560. First, a two-dimensional nanosheet precursor is synthesized via a hydrothermal method. Subsequently, a metal phosphide core-shell heterostructure is anchored onto the nanosheet through two high-temperature calcinations (one carbonization and one phosphating), with a nickel phosphide shell thickness of approximately 8 nm. This method uses a hydrothermal + calcination + phosphating preparation process, which is cumbersome, makes it difficult to control the shell thickness of the core-shell structure, and results in a less than one-third yield of hydrogen peroxide produced by electrocatalysis compared to this invention.

[0058] Comparative Example 3

[0059] The technical solution used is reported in Journal of Materials Chemistry A, 2023, 11, 10204-10212. Commercially available melamine sponge is used as a precursor, and synthesized via a hydrothermal-calcination method with graphene oxide, urea, boric acid, and nickel salt. This method involves a wide variety of raw materials and does not further regulate the core-shell structure, resulting in a catalyst with a two-electron oxygen reduction selectivity of less than 90%.

[0060] The above description is only used to detail the specific embodiments of the present invention, but the technical solutions proposed by the present invention are not limited to the above methods. All equivalent modifications and variations made by those skilled in the art to the technology proposed by the present invention without departing from the basic principles of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A sea urchin-like material, characterized in that, The material is in the shape of a spherical urchin, with a diameter of 3.0-6.0 μm; the outer periphery of the spherical urchin is a nanotube, and the nanotube is a nitrogen-doped carbon nanotube; and a small sphere with a core-shell structure is uniformly embedded in the matrix of the spherical urchin and on the top of part of the nanotube; the core of the core-shell structure is a Ni metal particle, and the shell layer is a nitrogen-doped carbon layer.

2. The sea urchin-like material according to claim 1, wherein, The diameter of the core of the core-shell structure is 10-100 nm; and the thickness of the shell layer of the core-shell structure is 5-15 nm.

3. The sea urchin-like material of claim 1, wherein, The nanotube has a length of 40-150 nm and a diameter of 10-20 nm.

4. The sea urchin-like material of claim 1, wherein, The composition of the material is: Ni is (2-15) at%, C is (80-90) at%, and N is (1.5-6.0) at%.

5. The method for preparing the sea urchin-like material according to any one of claims 1-4, characterized in that, The method comprises the following steps: (1) preparing Ni-MOF: a certain amount of N,N-dimethylformamide, anhydrous ethanol and deionized water are uniformly mixed to obtain solution A; a certain amount of terephthalic acid and nickel chloride hexahydrate are sequentially dissolved into solution A to obtain solution B; solution B is ultrasonically treated for a period of time, and then reacted at 160℃ for 12 h; after separation and washing for 3-4 times, the Ni-MOF is obtained by freeze-drying; (2) preparing a mixture of Ni-MOF and melamine: the Ni-MOF prepared in step (1) and melamine are dispersed in anhydrous ethanol at a certain ratio, mixed at a certain temperature for a period of time, and then the ethanol is evaporated by heating to obtain a solid; (3) preparing the urchin-shaped material: the solid obtained in step (2) is heated to 525-550℃ under a mixed gas atmosphere of hydrogen and argon for a first-stage calcination of 2-3 h; and then heated to 1000-1200℃ for a second-stage calcination of 2-3 h; thus the urchin-shaped material is obtained.

6. The production method according to claim 5, wherein In step (2), the amount of Ni-MOF and melamine added is such that the mass ratio of Ni-MOF to melamine is 1: (1-3); first, the mixture is stirred at 25℃ for 10-20 h, and then heated to 60℃ for further stirring and mixing until the ethanol is evaporated.

7. The preparation method according to claim 5, characterized in that, In step (3), in the first-stage calcination, the volume ratio of hydrogen to argon is 1:9, the flow rate is set to 100-200 sccm, the temperature is 550℃, the heating rate is 2℃ / min, and the holding time is 2 h; in the second-stage calcination, the temperature is 1100℃, the heating rate is 3℃ / min, and the holding time is 3 h.

8. Use of the urchin-shaped material according to any one of claims 1-4 for preparing an electrode material for electrocatalytic two-electron oxygen reduction reaction.

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