Non-noble metal ORR catalyst and preparation method thereof

Abstract

The invention discloses a non-noble metal ORR catalyst and a preparation method thereof, and belongs to the technical field of electro-catalysis. The method comprises the following steps: (1) adding 5, 10, 15, 20-tetra (4-cyanophenyl) porphyrin and nickel salt into an organic solvent, and synthesizing a supramolecular crystal precursor UPC-S7 through solvothermal reaction; (2) carbonizing the supramolecular crystal precursor UPC-S7 in an inert atmosphere to obtain a Ni-coated NC material; (3) oxidizing the Ni-coated NC material in an oxygen-containing atmosphere to obtain a Ni / NiO-coated NC material; and (4) sequentially soaking and etching the Ni / NiO-coated NC material by using a nitric acid solution and an ammonia water solution, and then washing and drying to obtain the non-noble metal ORR catalyst. The prepared catalyst does not contain precious metal such as platinum, the raw material cost is remarkably reduced on the basis of ensuring the ORR activity and stability of the catalyst, and a new scheme is provided for solving the cost bottleneck of a fuel cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrocatalysis, in particular to a non-noble metal ORR catalyst and a preparation method thereof. BACKGROUND

[0002] Oxygen reduction reaction (ORR) is the core cathode reaction of clean energy devices such as fuel cells and metal-air batteries. Due to its slow kinetics, it seriously restricts the overall performance of the battery. At present, commercial platinum carbon (Pt / C) catalyst is the benchmark catalyst for ORR, but the scarcity, high cost and poor stability / methanol tolerance of platinum greatly limit the large-scale commercial application of these energy technologies.

[0003] Transition metal-nitrogen-carbon (M-N-C) materials are considered as one of the most potential platinum substitutes. Among them, nickel-based catalysts are concerned due to their high earth abundance and potential activity. However, pure nickel-based catalysts have problems such as poor conductivity, insufficient active sites, and too strong adsorption energy for oxygen intermediates, which leads to unsatisfactory ORR activity and stability. SUMMARY

[0004] Based on the above technical problems, the present application provides a non-noble metal ORR catalyst and a preparation method thereof.

[0005] The technical solution adopted by the present application is as follows: A preparation method of a non-noble metal ORR catalyst, comprising the following steps: (1) Preparation of supramolecular crystal precursor UPC-S7: 5,10,15,20-tetra(4-cyanophenyl) porphyrin and nickel salt are added to an organic solvent to synthesize supramolecular crystal precursor UPC-S7 by solvothermal reaction; (2) Carbonization treatment: the supramolecular crystal precursor UPC-S7 obtained in step (1) is carbonized under inert atmosphere to obtain Ni@NC material; (3) Oxidation treatment: the Ni@NC material obtained in step (2) is oxidized under an oxygen-containing atmosphere to obtain Ni / NiO@NC material; (4) Etching treatment: the Ni / NiO@NC material obtained in step (3) is immersed and etched with nitric acid solution and ammonia solution in sequence, and then washed and dried to obtain a non-noble metal ORR catalyst.

[0006] The beneficial technical effects of the present application are as follows: (1) Complete non-noble metal: the catalyst prepared by the present application does not contain platinum and other noble metals, and the raw material cost is significantly reduced on the basis of ensuring the ORR activity and stability of the catalyst, which provides a new solution to the cost bottleneck of fuel cells.

[0007] (2) Heterostructure precise regulation and synergistic effect: The application innovatively adopts "acid / alkali two-step etching method" to etch the precursor after carbonization and oxidation treatment. This step can not only clean the material surface and create more pores, but more importantly, it can regulate the molar ratio of metal Ni and nickel oxide NiO in the final catalyst. Moreover, the inventors found that the molar ratio of metal Ni and nickel oxide NiO has an impact on the ORR performance of the catalyst, especially when the molar ratio of Ni:NiO in the catalyst is 1:3.2, the heterojunction interface synergistic effect is the strongest, and the ORR performance is optimal. The essence of this synergistic effect is that the metal Ni site has a suitable adsorption energy for the ·OOH intermediate, which is beneficial to the initial activation of O2 molecules and the formation of ·OOH; and the adjacent NiO site can effectively adsorb and activate H2O molecules, promote the formation of H + OH, and further promote the formation of H2O. This closely adjacent two active sites on the nanoscale work together to greatly promote the breaking of the O-O bond, the rate-determining step of the ORR reaction, thereby significantly improving the reaction kinetics.

[0008] (3) Efficient four-electron reaction path: Through Koutecky-Levich curve test, it is proved that the catalyst of the application is dominated by the efficient direct four-electron transfer path (electron transfer number n≈3.9), which is the same as the mechanism of commercial Pt / C, ensuring high reaction efficiency.

[0009] (4) Multistage pore and high specific surface area: The application takes porphyrin-based supramolecular crystals as precursors, and after carbonization, oxidation treatment and etching, a multistage pore structure with micropores and mesopores is formed, and the specific surface area under optimal conditions is as high as 550 m 2 / g or more, greatly promoting the mass transfer of reactants and products and the rapid transfer of electrons.

[0010] (5) Simple process, easy to scale up: The entire preparation process of the application is easy to obtain raw materials, does not require complex equipment, has clear steps and mild conditions, and is very suitable for industrial large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a synthesis schematic diagram of the non-noble metal ORR catalyst Ni / NiO@NC-1 in Example 1 of the application; Figure 2 is an XRD comparison chart of the catalysts Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9 and Ni / NiO@NC-1 prepared in Examples 1-4 of the application; Figure 3SEM comparison chart of Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, Ni / NiO@NC-1 catalysts prepared in examples 1-4 of the present application; wherein (a) is the SEM chart of Ni / NiO@NC-0.3 catalyst, (b) is the SEM chart of Ni / NiO@NC-0.5 catalyst, (c) is the SEM chart of Ni / NiO@NC-0.9 catalyst, and (d) is the SEM chart of Ni / NiO@NC-1 catalyst; Figure 4 HR-TEM characterization chart of Ni / NiO@NC-1 catalyst prepared in example 1 of the present application; Figure 5 Nitrogen adsorption-desorption isotherm comparison chart of Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, Ni / NiO@NC-1 catalysts prepared in examples 1-4 of the present application; Figure 6 Koutecky-Levich chart of Ni / NiO@NC-1 catalyst prepared in example 1 of the present application in 0.1 M KOH solution; Figure 7 Linear sweep voltammetry comparison chart of Ni / NiO@NC-0.3, Ni / NiO@NC-0.5, Ni / NiO@NC-0.9, Ni / NiO@NC-1 catalysts prepared in examples 1-4 of the present application and commercial Pt / C in oxygen-saturated 0.1 M KOH solution; Figure 8 Stability test comparison chart of Ni / NiO@NC-1 catalyst prepared in example 1 of the present application and commercial Pt / C. DETAILED DESCRIPTION

[0012] To achieve effective replacement of noble metal platinum catalyst, an ideal high-performance non-noble metal catalyst not only needs to meet the basic requirement of low cost, but more importantly, it needs to approach or even surpass platinum-based materials in core performances such as catalytic activity, reaction path and long-term stability. However, existing non-noble metal catalysts often fail to achieve breakthrough in multiple performance dimensions at the same time, which becomes the main obstacle to their practical application.

[0013] The present application provides a high-performance non-noble metal ORR catalyst and a preparation method thereof by interface engineering strategy to achieve performance breakthrough based on the above-mentioned needs. The core of the catalyst is to successfully construct and accurately control the Ni / NiO heterojunction. Specifically, the present application uses a structure-defined porphyrin-based supramolecular crystal as a precursor, and through a multi-step synergistic process of "carbonization-oxidation-etching", finally obtains a composite material in which metal Ni and nickel oxide NiO nanoparticles are embedded in a nitrogen-doped carbon matrix.

[0014] The key of the present application is also to introduce a step of accurately controllable "acid / alkali etching" post-processing. This step not only can effectively remove amorphous carbon and increase the specific surface area of the material, but more importantly, can accurately control the molar ratio of metal Ni and nickel oxide NiO in the final product by adjusting the concentration of the etching solution. Nitric acid solution can selectively dissolve part of nickel oxide (NiO), and ammonia solution can further adjust the surface chemical state. By controlling the concentration of the etching solution, Ni or NiO can be selectively removed to adjust their ratio. Especially when the molar ratio of Ni to NiO is adjusted to 1:3.2, the synergistic effect of the heterojunction interface reaches the best state. Of course, the acid / alkali etching post-processing process can also be combined with the above-mentioned steps to optimize the pore structure and surface chemical properties of the material. Metal 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 on the nanometer interface significantly reduces the reaction energy barrier of O-O bond breaking, thereby greatly optimizing the ORR kinetic process. Finally, the catalyst exhibits oxygen reduction activity comparable to commercial Pt / C (half-wave potential 0.79 V) and excellent stability in alkaline medium, and follows an efficient four-electron transfer path, providing strong material support for the development of low-cost, high-performance energy conversion devices.

[0015] The present application will be further described in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0016] The chemical reagents used in the following examples were purchased through commercial channels unless otherwise specified.

[0017] Example 1: (1) Preparation of supramolecular crystal precursor UPC-S7; 0.02g 5,10,15,20-tetrakis(4-cyanophenyl)porphyrin and 0.2g nickel nitrate hexahydrate were dissolved in 2mL N,N-dimethylformamide (DMF), ultrasonic for 5 minutes, sealed and placed in a 90℃ oven for 72 hours of reaction, to obtain purple UPC-S7 crystal. After washing with DMF and ethanol, it was dried at 80℃.

[0018] (2) carbonization; Take 100 mg of UPC-S7 crystal, after vacuum drying at 140 °C for 3 hours, place it in a tube furnace, under nitrogen atmosphere, heat to 800 °C at a rate of 5 °C / min, keep for 3 hours, and get Ni@NC material after natural cooling.

[0019] (3) oxidation; Place the above Ni@NC material in a tube furnace, heat to 400 °C at a rate of 5 °C / min under air atmosphere, keep for 0.5 hours, and get Ni / NiO@NC material.

[0020] (4) etching; 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 with water and ethanol several times, and get the final product after vacuum drying at 60 °C, which is recorded as Ni / NiO@NC-1.

[0021] Figure 1 The synthesis of Ni / NiO@NC-1 non-noble metal ORR catalyst is shown in the figure. It is shown that by using porphyrin-nickel supramolecular crystal as a single carbon / nitrogen / metal co-source, through the three-step process of "high-temperature inert carbonization-low-temperature directional oxidation-acid / alkali reconstruction", Ni / NiO@NC-1 non-noble metal ORR catalyst is obtained.

[0022] Example 2: (1) preparation of UPC-S7; Weigh 0.02 g of 5,10,15,20-tetrakis(4-cyanophenyl) porphyrin and 0.2 g of nickel nitrate hexahydrate into 2 mL of N,N-dimethylformamide (DMF), ultrasonic for 5 minutes, seal and place in a 90 °C oven for 72 hours, get purple UPC-S7 crystal, wash with DMF and ethanol, and dry at 80 °C.

[0023] (2) carbonization; Take 100 mg of UPC-S7 crystal, after vacuum drying at 140 °C for 3 hours, place it in a tube furnace, under nitrogen atmosphere, heat to 800 °C at a rate of 5 °C / min, keep for 3 hours, and get Ni@NC material after natural cooling.

[0024] (3) oxidation; Place the above Ni@NC material in a tube furnace, heat to 400 °C at a rate of 5 °C / min under air atmosphere, keep for 0.5 hours, and get Ni / NiO@NC material.

[0025] (4) etching; Take 20 mg of Ni / NiO@NC material, disperse in 2 mL of 18 wt% nitric acid solution, stir in the dark for 12 hours, filter. The resulting solid is redispersed in 2 mL of 33 wt% ammonia, stir in the dark for 12 hours, filter, wash with water and ethanol several times, vacuum drying at 60 ℃ to obtain the final product, recorded as Ni / NiO@NC-0.9.

[0026] Example 3: (1) Preparation of UPC-S7; Take 0.02 g of 5,10,15,20-tetrakis(4-cyanophenyl) porphyrin and 0.2 g of nickel nitrate hexahydrate, dissolve in 2 mL of N,N-dimethylformamide (DMF), ultrasonic for 5 minutes, seal and react in 90 ℃ oven for 72 hours, get purple UPC-S7 crystal, clean with DMF and ethanol, and dry at 80 ℃.

[0027] (2) Carbonization; Take 100 mg of UPC-S7 crystal, vacuum drying at 140 ℃ for 3 hours, then put it in a tube furnace, heat to 800 ℃ at a rate of 5 ℃ / min under nitrogen atmosphere, keep for 3 hours, and get Ni@NC material after natural cooling.

[0028] (3) Oxidation; Put the above Ni@NC material in a tube furnace, heat to 400 ℃ at a rate of 5 ℃ / min under air atmosphere, keep for 0.5 hours, and get Ni / NiO@NC material.

[0029] (4) Etching; Take 20 mg of Ni / NiO@NC material, disperse in 2 mL of 10 wt% nitric acid solution, stir in the dark for 12 hours, filter. The resulting solid is redispersed in 2 mL of 18 wt% ammonia, stir in the dark for 12 hours, filter, wash with water and ethanol several times, vacuum drying at 60 ℃ to obtain the final product, recorded as Ni / NiO@NC-0.5.

[0030] Example 4: (1) Preparation of UPC-S7; Take 0.02 g of 5,10,15,20-tetrakis(4-cyanophenyl) porphyrin and 0.2 g of nickel nitrate hexahydrate, dissolve in 2 mL of N,N-dimethylformamide (DMF), ultrasonic for 5 minutes, seal and react in 90 ℃ oven for 72 hours, get purple UPC-S7 crystal, clean with DMF and ethanol, and dry at 80 ℃.

[0031] (2) Carbonization; Take 100 mg of UPC-S7 crystal, after vacuum drying at 140 ℃ for 3 hours, place it in a tube furnace, heat to 800 ℃ at a rate of 5 ℃ / min under nitrogen atmosphere, and keep for 3 hours, and then get Ni@NC material after natural cooling.

[0032] (3) oxidation; Place the above Ni@NC material in a tube furnace, heat to 400 ℃ at a rate of 5 ℃ / min under air atmosphere, and keep for 0.5 hours to obtain Ni / NiO@NC material.

[0033] (4) etching; 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. Redispersed in 2 mL of 10 wt% ammonia water, stir in the dark for 12 hours, filter, wash with water and ethanol several times, and vacuum dry at 60 ℃ to obtain the final product, denoted as Ni / NiO@NC-0.3.

[0034] The catalysts prepared in Examples 1-4 of the present application are used for systematic physical characterization and electrochemical performance testing to verify the beneficial effects of the present application.

[0035] (1) phase, morphology and element composition analysis; As shown in Figure 2 , the XRD patterns of all catalysts show characteristic diffraction peaks of metal Ni at 44.5° and 51.8°, characteristic diffraction peaks of NiO at 37.3°, 43.3° and 62.9°, and a (002) crystal face diffraction peak of carbon at about 26.2°, confirming the presence of Ni / NiO heterostructure. With the increase of acid / alkali etching concentration, the carbon peak intensity increases, indicating that the graphitization degree of Ni / NiO@NC-1 is the highest. However, too high etching concentration may lead to excessive etching of the material, thereby reducing the performance.

[0036] As shown in the SEM patterns of Figure 3 , all samples maintain the macroscopic morphology of the precursor, but with the increase of acid / alkali concentration, the surface defects of the material are more obvious.

[0037] As shown in the HR-TEM patterns of Figure 4 , in Ni / NiO@NC-1, the crystal lattice fringes with a crystal face spacing of 0.200 nm and 0.240 nm can be clearly observed, corresponding to the (111) crystal face of metal Ni and the (111) crystal face of NiO, respectively, which directly proves the successful construction of Ni / NiO heterojunction.

[0038] The elemental contents of the catalysts were determined by elemental analyzer and ICP-AES, and the molar ratio of Ni to NiO was calculated. The results are summarized in Table 1. The data clearly shows that the precise control of the Ni / NiO ratio can be achieved by adjusting the etching concentration.

[0039] Table 1

[0040] (2) Specific surface area and pore structure analysis; As shown in the nitrogen adsorption-desorption isotherms of Figure 5 , all samples exhibit type IV isotherm characteristics, confirming the existence of mesoporous structure. The specific surface area determination results are shown in the above table. Ni / NiO@NC-1 has the largest specific surface area, which is consistent with the increase of surface defects and the etching pore-forming effect.

[0041] (3) Oxygen reduction performance and reaction kinetics analysis; The ORR performance of the catalysts was tested in a three-electrode system using a rotating disc electrode. The electrolyte was 0.1 M KOH solution saturated with oxygen, and the scan rate was 10 mV / s. As shown in Figure 7 , the performance of the catalysts prepared in the four examples varies significantly with the etching concentration and the 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), which is significantly better than the products of other examples, and is comparable to commercial 20% Pt / C.

[0042] To further explore the nature of its high performance, Koutecky-Levich (K-L) analysis was performed on Ni / NiO@NC-1. As shown in Figure 6 , at different potentials (0.4 V - 0.65 V), the K-L curves (J -1 vs. ω -1 / 2 ) all show good linearity and parallelism. According to the K-L equation, the average electron transfer number (n) is 3.9. This result proves that Ni / NiO@NC-1 is dominated by an efficient four-electron ORR path, which explains the reason for its high activity from the reaction kinetics level, and is consistent with the mechanism of Ni / NiO heterojunction synergistically promoting O-O bond breaking.

[0043] (4) Stability test; The chronoamperometry test was performed at a voltage of 0.3 V (vs. RHE) in 0.1 M KOH solution saturated with oxygen at a rotation speed of 1600 rpm for 10 hours. The results are shown in Figure 8As shown, Ni / NiO@NC-1 (Example 1) can still maintain 87.1% of the initial current after the end of the test, while the commercial 20% Pt / C only remains 53.5%, proving that the catalyst prepared by the application has extremely excellent stability.

[0044] On the basis of the above-mentioned embodiments, the application also has the following embodiments.

[0045] Example 5: (1) Preparation of supramolecular crystal precursor UPC-S7; 0.02g 5,10,15,20-tetrakis(4-cyanophenyl) porphyrin and 0.2g nickel nitrate hexahydrate were dissolved in 2mL N,N-dimethylformamide (DMF), ultrasonic for 5 minutes, sealed and placed in a 95 ℃ oven for 80 hours of reaction, to obtain purple UPC-S7 crystal, which was washed with DMF and ethanol and dried at 80 ℃.

[0046] (2) Carbonization; 100mg UPC-S7 crystal was taken, dried at 140 ℃ for 3 hours under vacuum, placed in a tube furnace, heated to 850 ℃ at a rate of 5 ℃ / min under nitrogen atmosphere, and kept for 3 hours, and then naturally cooled to obtain Ni@NC material.

[0047] (3) Oxidation; The above-mentioned Ni@NC material was placed in a tube furnace, heated to 350 ℃ at a rate of 5 ℃ / min under air atmosphere, and kept for 0.5 hours to obtain Ni / NiO@NC material.

[0048] (4) Etching; 20mg Ni / NiO@NC material was taken and dispersed in 2mL 20 wt% nitric acid solution, stirred in the dark for 12 hours, and filtered. The obtained solid was dispersed in 2mL 36 wt% ammonia water, stirred in the dark for 12 hours, and filtered. After washing with water and ethanol for several times, the final product was obtained after vacuum drying at 60 ℃.

[0049] Example 6: (1) Preparation of UPC-S7; 0.02g 5,10,15,20-tetrakis(4-cyanophenyl) porphyrin and 0.2g nickel nitrate hexahydrate were dissolved in 2mL N,N-dimethylformamide (DMF), ultrasonic for 5 minutes, sealed and placed in a 95 ℃ oven for 80 hours of reaction, to obtain purple UPC-S7 crystal, which was washed with DMF and ethanol and dried at 80 ℃.

[0050] (2) Carbonization; Take 100 mg of UPC-S7 crystals, after vacuum drying at 140 ℃ for 3 hours, place them in a tube furnace, heat to 750 ℃ at a rate of 5 ℃ / min under nitrogen atmosphere, keep for 2 hours, and after natural cooling, obtain Ni@NC material.

[0051] (3) oxidation; Place the above Ni@NC material in a tube furnace, heat to 450 ℃ at a rate of 5 ℃ / min under air atmosphere, keep for 0.8 hours, and obtain Ni / NiO@NC material.

[0052] (4) etching; 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 with water and ethanol several times, and after vacuum drying at 60 ℃, 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.

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: The molar ratio of metallic Ni to nickel oxide NiO in this catalyst is 1:3.0-1:3.

5.

10. 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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