A non-noble metal orr catalyst and a method for preparing the same

Abstract

The application discloses a non-noble metal ORR catalyst and a preparation method thereof, and belongs to the technical field of electrocatalysis. The method comprises the following steps: (1) 5,10,15,20-tetra(4-cyanophenyl) porphyrin and a nickel salt are added into an organic solvent, and a supramolecular crystal precursor UPC-S7 is synthesized through a solvothermal reaction; (2) the supramolecular crystal precursor UPC-S7 is carbonized under an inert atmosphere to obtain a Ni@NC material; (3) the Ni@NC material is oxidized under an oxygen-containing atmosphere to obtain a Ni / NiO@NC material; and (4) the Ni / NiO@NC material is sequentially immersed in a nitric acid solution and an ammonia solution for etching, and after washing and drying, a non-noble metal ORR catalyst is obtained. The catalyst prepared by the application does not contain noble metals such as platinum at all, the raw material cost is significantly reduced on the basis of guaranteeing the ORR activity and stability of the catalyst, and a new scheme is provided for solving the cost bottleneck of fuel cells.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a non-noble metal ORR catalyst and its preparation method. Background Technology

[0002] The oxygen reduction reaction (ORR) is the core cathode reaction in clean energy devices such as fuel cells and metal-air batteries. Its slow kinetics severely limit the overall performance of the battery. Currently, commercial platinum-carbon (Pt / C) catalysts are the benchmark catalysts for ORR, but the scarcity, high cost, and poor stability / methanol tolerance of platinum greatly restrict the large-scale commercial application of these energy technologies.

[0003] Transition metal-nitrogen-carbon (MNC) materials are considered one of the most promising alternatives to platinum. Among them, nickel-based catalysts have attracted attention due to their high abundance on Earth and potential activity. However, pure nickel-based catalysts suffer from poor conductivity, insufficient active sites, and excessively strong adsorption energy for oxygen intermediates, resulting in less than ideal ORR activity and stability. Summary of the Invention

[0004] Based on the above-mentioned technical problems, this invention proposes a non-precious metal ORR catalyst and its preparation method.

[0005] The technical solution adopted in this invention is:

[0006] A method for preparing a non-noble metal ORR catalyst includes the following steps:

[0007] (1) Preparation of supramolecular crystal precursor UPC-S7: 5,10,15,20-tetra(4-cyanophenyl)porphyrin and nickel salt were added to an organic solvent and the supramolecular crystal precursor UPC-S7 was synthesized by solvothermal reaction;

[0008] (2) Carbonization treatment: The supramolecular crystal precursor UPC-S7 obtained in step (1) is carbonized in an inert atmosphere to obtain Ni@NC material;

[0009] (3) Oxidation treatment: The Ni@NC material obtained in step (2) is oxidized in an oxygen-containing atmosphere to obtain Ni / NiO@NC material;

[0010] (4) Etching treatment: The Ni / NiO@NC material obtained in step (3) is successively immersed and etched with nitric acid solution and ammonia solution, and then washed and dried to obtain a non-precious metal ORR catalyst.

[0011] The beneficial technical effects of the present invention are as follows:

[0012] (1) Completely non-precious metals: The catalyst prepared by this invention does not contain any precious metals such as platinum. While ensuring the ORR activity and stability of the catalyst, the raw material cost is significantly reduced, providing a new solution to the cost bottleneck of fuel cells.

[0013] (2) Precise Regulation and Synergistic Effect of Heterogeneous Structure: This invention innovatively employs an "acid / base two-step etching method" to etch the precursor after carbonization and oxidation. This step not only cleans the material surface and creates more pores, but more importantly, it can regulate the molar ratio of metallic Ni to nickel oxide NiO in the final catalyst. Moreover, the inventors discovered that the molar ratio of metallic Ni to nickel oxide NiO affects the ORR performance of the catalyst, especially when the Ni:NiO molar ratio in the catalyst is 1:3.2, the heterojunction interface synergistic effect is the strongest, and the ORR performance reaches the optimal level. The essence of this synergistic effect is that the metallic Ni sites have suitable adsorption energy for the ·OOH intermediate, which is conducive to the initial activation of O2 molecules and the formation of ·OOH; while the adjacent NiO sites can effectively adsorb and activate H2O molecules, promoting H2O formation. + The supply of these two closely adjacent active sites at the nanoscale works together to greatly promote the rate-determining step of the ORR reaction, the breaking of the OO bond, thereby significantly improving the reaction kinetics.

[0014] (3) Efficient four-electron reaction pathway: Koutecky-Levich curve tests confirmed that the catalyst of this invention is dominated by an efficient direct four-electron transfer pathway (electron transfer number n≈3.9), which is the same as the mechanism of commercial Pt / C, ensuring high reaction efficiency.

[0015] (4) Hierarchical pore structure and high specific surface area: This invention uses porphyrin-based supramolecular crystals as precursors, and after carbonization, oxidation and etching, a hierarchical pore structure with micropores and mesopores is formed. Under optimal conditions, the specific surface area is as high as 550 m². 2 Above / g, it greatly promotes mass transfer and rapid electron transfer between reactants and products.

[0016] (5) Simple process and easy to scale up: The raw materials are readily available, no complicated equipment is required, the steps are clear, and the conditions are mild, making it very suitable for large-scale industrial production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the synthesis of the Ni / NiO@NC-1 non-noble metal ORR catalyst in Example 1 of the present invention;

[0018] Figure 2The XRD comparison diagrams are of the Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, and Ni / NiO@NC-1 catalysts prepared in Examples 1-4 of this invention.

[0019] Figure 3 The images show SEM comparisons of the Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, and Ni / NiO@NC-1 catalysts prepared in Examples 1-4 of this invention; where (a) is the SEM image of the Ni / NiO@NC-0.3 catalyst, (b) is the SEM image of the Ni / NiO@NC-0.5 catalyst, (c) is the SEM image of the Ni / NiO@NC-0.9 catalyst, and (d) is the SEM image of the Ni / NiO@NC-1 catalyst.

[0020] Figure 4 The image shows the HR-TEM characterization of the Ni / NiO@NC-1 catalyst prepared in Example 1 of this invention.

[0021] Figure 5 Comparison of nitrogen adsorption-desorption isotherms for the Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, and Ni / NiO@NC-1 catalysts prepared in Examples 1-4 of this invention;

[0022] Figure 6 The Koutecky-Levich curve of the Ni / NiO@NC-1 catalyst prepared in Example 1 of this invention in 0.1 M KOH solution is shown.

[0023] Figure 7 The linear sweep voltammetry curves of the Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, and Ni / NiO@NC-1 catalysts prepared in Examples 1-4 of this invention and commercial Pt / C in oxygen-saturated 0.1 M KOH solution are compared.

[0024] Figure 8 This is a comparison chart of the stability test results of the Ni / NiO@NC-1 catalyst prepared in Example 1 of this invention and commercial Pt / C. Detailed Implementation

[0025] To effectively replace platinum catalysts, ideal high-performance non-precious metal catalysts not only need to meet the basic requirement of low cost, but more importantly, they must approach or even surpass platinum-based materials in core performance aspects such as catalytic activity, reaction pathway, and long-term stability. However, existing non-precious metal catalysts often struggle to achieve breakthroughs in multiple performance dimensions simultaneously, which has become a major obstacle restricting their practical application.

[0026] Based on the aforementioned needs, this invention provides a high-performance non-noble metal ORR catalyst and its preparation method that achieves performance breakthroughs through interface engineering strategies. The core of this catalyst lies in the successful construction and precise control of the Ni / NiO heterostructure. Specifically, this invention uses a structurally well-defined porphyrin-based supramolecular crystal as a precursor and, through a multi-step synergistic process of "carbonization-oxidation-etching," ultimately obtains a composite material in which metallic Ni and nickel oxide NiO nanoparticles are co-embedded in a nitrogen-doped carbon matrix.

[0027] The key to this invention lies in the introduction of a precisely controllable "acid / alkali etching" post-treatment process. This step not only effectively removes amorphous carbon and increases the specific surface area of ​​the material, but more importantly, it allows for precise control of the molar ratio of metallic Ni to nickel oxide (NiO) in the final product by adjusting the concentration of the etching solution. Nitric acid solution selectively dissolves some nickel oxide (NiO), while ammonia solution further regulates the surface chemical state. By controlling the concentration of the etching solution, Ni or NiO can be selectively removed, thereby adjusting their ratio. In particular, when the molar ratio of Ni to NiO is controlled to 1:3.2, the synergistic effect of the heterojunction interface reaches its optimal state. Of course, the acid / alkali etching post-treatment process can also be combined with the aforementioned steps to optimize the pore structure and surface chemical properties of the material. Metallic Ni sites tend to adsorb ·OOH intermediates, while NiO sites efficiently promote the adsorption and activation of H2O molecules. The synergistic effect of the two at the nano-interface significantly reduces the reaction energy barrier for OO bond breaking, thereby greatly optimizing the ORR kinetics. Ultimately, the catalyst exhibits oxygen reduction activity (half-wave potential 0.79 V) comparable to commercial Pt / C in alkaline media and excellent stability, and follows an efficient four-electron transfer pathway, providing strong material support for the development of low-cost, high-performance energy conversion devices.

[0028] The present application will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the scope of the present application.

[0029] Unless otherwise specified, all chemical reagents used in the following examples were purchased commercially.

[0030] Example 1:

[0031] (1) Preparation of supramolecular crystal precursor UPC-S7;

[0032] Weigh 0.02 g of 5,10,15,20-tetra(4-cyanophenyl)porphyrin and 0.2 g of nickel nitrate hexahydrate and dissolve them in 2 mL of N,N-dimethylformamide (DMF). Sonicate for 5 minutes, seal and allow to stand in an oven at 90 °C for 72 hours to obtain purple UPC-S7 crystals. After washing with DMF and ethanol, dry at 80 °C.

[0033] (2) Carbonization;

[0034] Take 100 mg of UPC-S7 crystals, dry them under vacuum at 140 °C for 3 hours, place them in a tube furnace, heat them to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold them at that temperature for 3 hours, and then cool them naturally to obtain Ni@NC material.

[0035] (3) Oxidation;

[0036] The Ni@NC material was placed in a tube furnace and heated to 400°C at a rate of 5°C / min under air atmosphere, and held for 0.5 hours to obtain Ni / NiO@NC material.

[0037] (4) Etching;

[0038] Take 20 mg of Ni / NiO@NC material, disperse it in 2 mL of 20 wt% nitric acid solution, stir in the dark for 12 hours, and filter. Redisperse the obtained solid in 2 mL of 36 wt% ammonia water, stir in the dark for 12 hours, filter, wash several times with water and ethanol, and dry under vacuum at 60 °C to obtain the final product, denoted as Ni / NiO@NC-1.

[0039] Figure 1 This is a schematic diagram of the synthesis of the Ni / NiO@NC-1 non-noble metal ORR catalyst. The diagram shows the process of obtaining the Ni / NiO@NC-1 non-noble metal ORR catalyst through a three-step process of "high-temperature inert carbonization - low-temperature directional oxidation - acid / base reconstruction" using porphyrin-nickel supramolecular crystals as the single carbon / nitrogen / metal cosource.

[0040] Example 2:

[0041] (1) Preparation of UPC-S7;

[0042] Weigh 0.02 g of 5,10,15,20-tetra(4-cyanophenyl)porphyrin and 0.2 g of nickel nitrate hexahydrate and dissolve them in 2 mL of N,N-dimethylformamide (DMF). Sonicate for 5 minutes, seal and allow to stand in an oven at 90 °C for 72 hours to obtain purple UPC-S7 crystals. After washing with DMF and ethanol, dry at 80 °C.

[0043] (2) Carbonization;

[0044] Take 100 mg of UPC-S7 crystals, dry them under vacuum at 140 °C for 3 hours, place them in a tube furnace, heat them to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold them at that temperature for 3 hours, and then cool them naturally to obtain Ni@NC material.

[0045] (3) Oxidation;

[0046] The Ni@NC material was placed in a tube furnace and heated to 400°C at a rate of 5°C / min under air atmosphere, and held for 0.5 hours to obtain Ni / NiO@NC material.

[0047] (4) Etching;

[0048] Take 20 mg of Ni / NiO@NC material, disperse it in 2 mL of 18 wt% nitric acid solution, stir in the dark for 12 hours, and filter. Redisperse the obtained solid in 2 mL of 33 wt% ammonia water, stir in the dark for 12 hours, filter, wash several times with water and ethanol, and dry under vacuum at 60 °C to obtain the final product, denoted as Ni / NiO@NC-0.9.

[0049] Example 3:

[0050] (1) Preparation of UPC-S7;

[0051] Weigh 0.02 g of 5,10,15,20-tetra(4-cyanophenyl)porphyrin and 0.2 g of nickel nitrate hexahydrate and dissolve them in 2 mL of N,N-dimethylformamide (DMF). Sonicate for 5 minutes, seal and allow to stand in an oven at 90 °C for 72 hours to obtain purple UPC-S7 crystals. After washing with DMF and ethanol, dry at 80 °C.

[0052] (2) Carbonization;

[0053] Take 100 mg of UPC-S7 crystals, dry them under vacuum at 140 °C for 3 hours, place them in a tube furnace, heat them to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold them at that temperature for 3 hours, and then cool them naturally to obtain Ni@NC material.

[0054] (3) Oxidation;

[0055] The Ni@NC material was placed in a tube furnace and heated to 400°C at a rate of 5°C / min under air atmosphere, and held for 0.5 hours to obtain Ni / NiO@NC material.

[0056] (4) Etching;

[0057] Take 20 mg of Ni / NiO@NC material, disperse it in 2 mL of 10 wt% nitric acid solution, stir in the dark for 12 hours, and filter. The resulting solid is then redispersed in 2 mL of 18 wt% ammonia water, stirred in the dark for 12 hours, filtered, washed several times with water and ethanol, and dried under vacuum at 60 °C to obtain the final product, denoted as Ni / NiO@NC-0.5.

[0058] Example 4:

[0059] (1) Preparation of UPC-S7;

[0060] Weigh 0.02 g of 5,10,15,20-tetra(4-cyanophenyl)porphyrin and 0.2 g of nickel nitrate hexahydrate and dissolve them in 2 mL of N,N-dimethylformamide (DMF). Sonicate for 5 minutes, seal and allow to stand in an oven at 90 °C for 72 hours to obtain purple UPC-S7 crystals. After washing with DMF and ethanol, dry at 80 °C.

[0061] (2) Carbonization;

[0062] Take 100 mg of UPC-S7 crystals, dry them under vacuum at 140 °C for 3 hours, place them in a tube furnace, heat them to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold them at that temperature for 3 hours, and then cool them naturally to obtain Ni@NC material.

[0063] (3) Oxidation;

[0064] The Ni@NC material was placed in a tube furnace and heated to 400°C at a rate of 5°C / min under air atmosphere, and held for 0.5 hours to obtain Ni / NiO@NC material.

[0065] (4) Etching;

[0066] Take 20 mg of Ni / NiO@NC material, disperse it in 2 mL of 6 wt% nitric acid solution, stir in the dark for 12 hours, and filter. Redisperse the obtained solid in 2 mL of 10 wt% ammonia water, stir in the dark for 12 hours, filter, wash several times with water and ethanol, and dry under vacuum at 60 °C to obtain the final product, denoted as Ni / NiO@NC-0.3.

[0067] The catalysts prepared in Examples 1-4 of this invention were subjected to systematic physical characterization and electrochemical performance testing to verify the beneficial effects of this invention.

[0068] (1) Analysis of phase, morphology and elemental composition;

[0069] like Figure 2As shown, the XRD patterns of all catalysts exhibit characteristic diffraction peaks of metallic Ni at 44.5° and 51.8°, characteristic diffraction peaks of NiO at 37.3°, 43.3°, and 62.9°, and a (002) crystal plane diffraction peak of carbon at approximately 26.2°, confirming the existence of the Ni / NiO heterostructure. The carbon peak intensity increases with increasing acid / base etching concentration, indicating that Ni / NiO@NC-1 has the highest degree of graphitization. However, excessively high etching concentrations may lead to over-etching of the material, which could degrade its performance.

[0070] like Figure 3 As shown in the SEM images, all samples maintained the macroscopic morphology of the precursor, but the surface defects of the material became more obvious with the increase of acid / base concentration.

[0071] like Figure 4 As shown in the HR-TEM image, lattice fringes with interplanar spacing of 0.200 nm and 0.240 nm can be clearly observed in Ni / NiO@NC-1, which correspond to the (111) crystal plane of metallic Ni and the (111) crystal plane of NiO, respectively, which intuitively proves the successful construction of Ni / NiO heterojunction.

[0072] The elemental content of the catalyst was determined using an elemental analyzer and ICP-AES, and the molar ratio of Ni to NiO was calculated. The results are summarized in Table 1. This data clearly demonstrates that the Ni / NiO ratio can be precisely controlled by adjusting the etching concentration.

[0073] Table 1

[0074]

[0075] (2) Specific surface area and pore structure analysis;

[0076] like Figure 5 As shown in the nitrogen adsorption-desorption isotherms, all samples exhibited type IV isotherm characteristics, confirming the presence of mesoporous structures. The specific surface area measurements are shown in the table above; Ni / NiO@NC-1 had the largest specific surface area, consistent with increased surface defects and etching-induced pore formation.

[0077] (3) Oxygen reduction performance and reaction kinetics analysis;

[0078] The ORR performance of the catalyst was tested in a three-electrode system using a rotating disk electrode. The electrolyte was an oxygen-saturated 0.1 M KOH solution, and the scan rate was 10 mV / s. The results are as follows: Figure 7As shown, the catalyst performance of the four examples varies significantly with changes in etching concentration and Ni / NiO ratio. Ni / NiO@NC-1 (Example 1) has the most positive half-wave potential (0.793 V) and the largest limiting current density (-5.49 mA / cm²), and its activity is significantly better than the products of the other examples and comparable to that of commercial 20% Pt / C.

[0079] To further explore the nature of its high performance, Koutecky-Levich (KL) analysis was performed on Ni / NiO@NC-1. For example... Figure 6 As shown, the KL curves (J) are obtained under different potentials (0.4 V - 0.65 V). -1 vs. ω -1 / 2 All exhibit good linearity and parallelism. Calculated according to the KL equation, its average electron transfer number (n) is 3.9. This result demonstrates that Ni / NiO@NC-1 dominates a highly efficient four-electron ORR pathway, explaining its high activity from a reaction kinetic perspective, and is consistent with the mechanism by which Ni / NiO heterostructure synergistically promotes OO bond breaking.

[0080] (4) Stability testing;

[0081] Chorometric testing was conducted at 0.3 V (vs. RHE) in an oxygen-saturated 0.1 M KOH solution at 1600 rpm for 10 hours. The results are as follows: Figure 8 As shown, Ni / NiO@NC-1 (Example 1) retained 87.1% of its initial current after the test, while commercial 20% Pt / C only retained 53.5%, demonstrating that the catalyst prepared by this invention has extremely excellent stability.

[0082] Based on the above embodiments, the present invention also has the following embodiments.

[0083] Example 5:

[0084] (1) Preparation of supramolecular crystal precursor UPC-S7;

[0085] Weigh 0.02 g of 5,10,15,20-tetra(4-cyanophenyl)porphyrin and 0.2 g of nickel nitrate hexahydrate and dissolve them in 2 mL of N,N-dimethylformamide (DMF). Sonicate for 5 minutes, seal and allow to stand in an oven at 95 °C for 80 hours to obtain purple UPC-S7 crystals. After washing with DMF and ethanol, dry at 80 °C.

[0086] (2) Carbonization;

[0087] Take 100 mg of UPC-S7 crystals, dry them under vacuum at 140 °C for 3 hours, place them in a tube furnace, heat them to 850 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold them at that temperature for 3 hours, and then cool them naturally to obtain Ni@NC material.

[0088] (3) Oxidation;

[0089] The Ni@NC material was placed in a tube furnace and heated to 350°C at a rate of 5°C / min under air atmosphere, and held for 0.5 hours to obtain Ni / NiO@NC material.

[0090] (4) Etching;

[0091] Take 20 mg of Ni / NiO@NC material, disperse it in 2 mL of 20 wt% nitric acid solution, stir in the dark for 12 hours, and filter. Redisperse the obtained solid in 2 mL of 36 wt% ammonia water, stir in the dark for 12 hours, filter, wash several times with water and ethanol, and dry under vacuum at 60 °C to obtain the final product.

[0092] Example 6:

[0093] (1) Preparation of UPC-S7;

[0094] Weigh 0.02 g of 5,10,15,20-tetra(4-cyanophenyl)porphyrin and 0.2 g of nickel nitrate hexahydrate and dissolve them in 2 mL of N,N-dimethylformamide (DMF). Sonicate for 5 minutes, seal and allow to stand in an oven at 85 °C for 60 hours to obtain purple UPC-S7 crystals. After washing with DMF and ethanol, dry at 80 °C.

[0095] (2) Carbonization;

[0096] Take 100 mg of UPC-S7 crystals, dry them under vacuum at 140 °C for 3 hours, place them in a tube furnace, heat them to 750 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold them at that temperature for 2 hours, and then cool them naturally to obtain Ni@NC material.

[0097] (3) Oxidation;

[0098] The Ni@NC material was placed in a tube furnace and heated to 450°C at a rate of 5°C / min under air atmosphere, and held for 0.8 hours to obtain Ni / NiO@NC material.

[0099] (4) Etching;

[0100] Take 20 mg of Ni / NiO@NC material, disperse it in 2 mL of 18 wt% nitric acid solution, stir in the dark for 12 hours, and filter. Redisperse the obtained solid in 2 mL of 33 wt% ammonia water, stir in the dark for 12 hours, filter, wash several times with water and ethanol, and dry under vacuum at 60 °C to obtain the final product.

Claims

1. A method for preparing a non-noble metal ORR catalyst, characterized in that, Includes the following steps: (1) Preparation of supramolecular crystal precursor UPC-S7: 5,10,15,20-tetra(4-cyanophenyl)porphyrin and nickel salt were added to an organic solvent and the supramolecular crystal precursor UPC-S7 was synthesized by solvothermal reaction; (2) Carbonization treatment: The supramolecular crystal precursor UPC-S7 obtained in step (1) is carbonized in an inert atmosphere to obtain Ni@NC material; (3) Oxidation treatment: The Ni@NC material obtained in step (2) is oxidized in an oxygen-containing atmosphere to obtain Ni / NiO@NC material; (4) Etching treatment: The Ni / NiO@NC material obtained in step (3) is successively immersed and etched with nitric acid solution and ammonia solution, and then washed and dried to obtain a non-precious metal ORR catalyst. The molar ratio of metallic Ni to nickel oxide NiO in the catalyst is 1:3.0-1:3.

5.

2. The method for preparing a non-noble metal ORR catalyst according to claim 1, characterized in that, In step (1): the nickel salt is nickel nitrate hexahydrate; the molar ratio of 5,10,15,20-tetra(4-cyanophenyl)porphyrin to nickel nitrate hexahydrate is 1:20-1:30; the organic solvent is N,N-dimethylformamide; the temperature of the solvothermal reaction is controlled at 85-95℃, and the reaction time is 60-80 hours.

3. The method for preparing a non-noble metal ORR catalyst according to claim 1, characterized in that, In step (2): the inert atmosphere is nitrogen or argon; during carbonization, the heating rate is controlled at 4-6℃ / min, the temperature is raised to 750-850℃ and held for 2-4 hours.

4. The method for preparing a non-noble metal ORR catalyst according to claim 1, characterized in that, In step (3): the oxygen-containing atmosphere is air or oxygen atmosphere; during oxidation, the heating rate is controlled at 4-6℃ / min, the temperature is raised to 350-450℃ and held for 0.4-0.8 hours.

5. The method for preparing a non-noble metal ORR catalyst according to claim 1, characterized in that, In step (4): the concentration of the nitric acid solution is 5-25 wt%, and the concentration of the ammonia solution is 10-40 wt%.

6. The method for preparing a non-noble metal ORR catalyst according to claim 5, characterized in that: During the immersion etching process, the Ni / NiO@NC material is first stirred in a nitric acid solution in the dark for 10-14 hours, then filtered and stirred in an ammonia solution in the dark for another 10-14 hours.

7. The method for preparing a non-noble metal ORR catalyst according to claim 5, characterized in that: By adjusting the concentrations of nitric acid and ammonia, the molar ratio of metallic Ni to nickel oxide (NiO) in the catalyst can be controlled between 1:3 and 1:

8.

8. A non-noble metal ORR catalyst prepared by the method according to any one of claims 1-7, characterized in that: The catalyst is a heterostructure material in which Ni and NiO nanoparticles are co-embedded in a nitrogen-doped carbon matrix, and its specific surface area is not less than 250 m². 2 / g, and has a multi-level pore structure with both micropores and mesopores.

9. The non-noble metal ORR catalyst as described in claim 8, characterized in that: In 0.1 M KOH solution, the number of electrons transferred in the oxygen reduction reaction is 3.8-4.0.

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