Preparation method and application of transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst

Abstract

The present application relates to the technical field of non-noble metal electrocatalyst, and particularly relates to a preparation method and application of a transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst, comprising the following steps: step one: preparing a nitrogen-doped porous walnut-like carbon nanosphere; step two: preparing a transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst; the present application uses a double-template strategy to prepare a walnut-like carbon nanosphere carrier, uniformly adsorbs transition metal cations on the surface of the carrier through interface charge interaction, and again introduces a nitrogen-containing compound to avoid agglomeration of the transition metal in a pyrolysis process, thereby preparing a porous walnut-like carbon nanosphere structure electrocatalyst with a high-dispersion transition metal-N x active site, which is suitable for an oxygen reduction reaction of a cathode of a hydrogen-oxygen exchange membrane fuel cell.

Description

Technical Field

[0001] This invention relates to the field of non-precious metal electrocatalyst technology, specifically to a method for preparing and applying a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst. Background Technology

[0002] In polymer electrolyte membrane fuel cells (MEFs), the oxygen reduction reaction (ORR) occurs at the cathode, while the hydrogen oxidation reaction (HOR) of fuel H2 is completed at the anode. This allows the chemical energy of the fuel H2 to be directly converted into electrical energy, offering advantages such as environmental friendliness, low operating temperature, high energy conversion efficiency, high power density, and low operating noise. It has wide applications in aviation, aerospace, marine, rail transportation, electronic equipment, and backup power supplies, and is particularly valuable in the field of new energy vehicles. However, the slow ORR reaction rate at the cathode requires a large amount of electrocatalyst to accelerate the reaction process. Currently, the widely used ORR electrocatalysts are platinum-based, and platinum reserves are limited and expensive, hindering the commercialization of MEFs. Therefore, developing low-cost, highly active, and highly stable non-precious metal electrocatalysts is one of the effective ways to promote their commercialization. Currently researched non-precious metal electrocatalysts mainly include transition metal carbon, nitrogen, oxygen, sulfur, and phosphides, as well as transition metal-nitrogen-carbon electrocatalysts. Among them, transition metal-nitrogen-carbon materials are considered the most promising non-precious metal electrocatalysts for application in MEFs.

[0003] Traditionally, transition metal-nitrogen-carbon materials are obtained by directly pyrolyzing a mixture of nitrogen source, carbon source, and transition metal. For example, Wang Rongfang et al. obtained transition metal-nitrogen-carbon materials by directly pyrolyzing bipyridine, carbon nanotubes, and transition metal salts. However, due to the poor ability of carbon nanotubes to anchor single atoms, subsequent acid treatment is required to remove the transition metal nanoparticles generated during pyrolysis before obtaining the transition metal-nitrogen-carbon materials, which is a cumbersome process (Wang Rongfang, Wang Wei, Wang Hui, Ma Yanjiao, Northwest Normal University, Application No.: 201210008568.9). Zong Lingbo et al. obtained transition metal-nitrogen-carbon nanosphere materials by pyrolyzing activated carbon spheres, nitrogen source, and transition metal salt. However, the preparation of activated carbon spheres involves hydrothermal synthesis, alkali activation, and water washing steps, which is complex (Zong Lingbo, Wu Weicui, Chen Xin, Zhang Wenjun, Wang Lei, Qingdao University of Science and Technology, Application No.: 202011269900.8). In recent years, transition metal-nitrogen-carbon materials have been obtained by directly pyrolyzing metal-organic frameworks (MOFs). For example, Xiang Zhonghua et al. used two ligands and a metal source to directly synthesize a uniformly distributed MOF polymer, and then prepared a high-performance ORR electrocatalyst through high-temperature carbonization. However, due to the high-temperature carbonization, some transition metal-N bonds were destroyed, the transition metal aggregated, and the number of active sites decreased (Xiang Zhonghua, Xu Li, Yue Xianjin, Beijing University of Chemical Technology, Application No.: 201910798129.4). Wang Ding et al. used Fe-doped ZIF-8 as a precursor and added a secondary nitrogen source to successfully obtain a single-atom dispersed iron-based electrocatalyst through high-temperature heat treatment. However, the morphology of the precursor was not well maintained, which was not conducive to the full exposure of active sites (Wang Ding, Tao Xiafang, Yang Juan, Zhou Yazhou, Jiangsu University, Application No.: 202010705526.5). Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing and applying a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst, characterized by comprising the following steps:

[0007] Step 1: Preparation of nitrogen-doped porous walnut-shaped carbon nanospheres

[0008] First, nitrogen / carbon source dopamine hydrochloride, emulsifier 1,3,5-trimethylbenzene, surfactant P123 and triblock copolymer F127 were dispersed in a water / ethanol mixed solution. After sonication, ammonia water, a polymerization initiator, was quickly added. The reaction was carried out at room temperature for 2-5 h. After centrifugation and washing, walnut-shaped polymeric compound A was obtained.

[0009] Then, the walnut-shaped polymer compound A was placed in an inert atmosphere and carbonized at a temperature of 600–100 °C for 0.5–4 h to obtain nitrogen-doped porous walnut-shaped carbon nanospheres B.

[0010] Step 2: Preparation of transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere electrocatalysts

[0011] First, the nitrogen-doped porous walnut-shaped carbon nanospheres B obtained in step one were dispersed in an aqueous / ethanol solution containing a transition metal salt, and then sonicated to obtain a suspension. Second, the suspension was placed at 40–90 °C. o In a water bath, transition metal cations are uniformly adsorbed onto the surface of nitrogen-doped porous walnut-shaped carbon nanospheres B. Then, after the water / ethanol has completely evaporated, the nitrogen-doped porous walnut-shaped carbon nanospheres C coated with transition metal salts are further ground and mixed uniformly with a nitrogen-containing compound to obtain composite D. Finally, composite D is placed in an inert atmosphere and carbonized at 600–1100 °C for 0.5–4 h to obtain a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structured electrocatalyst E.

[0012] Preferably, the nitrogen-containing compound is one or a mixture of two or more of the following: urea, dicyandiamide, 4,4'-bipyridine, 2,2'-bipyridine, o-phenanthroline, melamine, phenylenediamine, and 4,4'-diaminoterphenyl.

[0013] Preferably, in steps one and two, the inert atmosphere is one or a mixture of two or more of helium, argon, and nitrogen.

[0014] Preferably, in step one, the concentration of the nitrogen / carbon source dopamine hydrochloride in the water / ethanol mixed solution is 1–50 mg / ml. -1 The concentration of the emulsifier 1,3,5-trimethylbenzene in the water / ethanol mixed solution is 0.01–1 ml. -1 The concentration of the surfactant P123 in the water / ethanol mixed solution is 1–10 mg / ml. -1 The concentration of the triblock copolymer F127 in the water / ethanol mixed solution is 1–10 mg / ml. -1 The concentration of the polymerization directing agent ammonia in the water / ethanol mixed solution is 0.01–1 ml. -1 .

[0015] Preferably, in step one, the ultrasound duration is 0.1 to 1 hour.

[0016] Preferably, in step two, the transition metal salt is one or more of the chlorides, sulfates, nitrates, and acetylacetone salts of iron, cobalt, nickel, copper, and manganese.

[0017] Preferably, in step two, the concentration of the nitrogen-doped porous walnut-shaped carbon nanospheres B in the water / ethanol solution of the transition metal salt is 1–20 mg / ml. -1 The concentration of the transition metal salt in the water / ethanol solution is 0.1–1 mmol / L. -1 .

[0018] Preferably, in step two, the mass ratio of the nitrogen-doped porous walnut-shaped carbon nanospheres C coated with transition metal salts to the nitrogen-containing compound is 0.1 to 1.

[0019] Preferably, in step two, the ultrasound duration is 0.1 to 2 hours.

[0020] This invention provides a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere electrocatalyst prepared by the aforementioned method.

[0021] This invention provides an application of a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst in the oxygen reduction reaction at the cathode of a hydroxide exchange membrane fuel cell.

[0022] The present invention has the following beneficial effects:

[0023] The transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere electrocatalyst prepared in this invention has high electrocatalytic activity and is suitable for the oxygen reduction reaction at the cathode of a hydroxide exchange membrane fuel cell.

[0024] This invention employs a dual-template strategy to prepare walnut-shaped carbon nanosphere supports. Transition metal cations are uniformly adsorbed onto the support surface through interfacial charge interactions. The reintroduction of nitrogen-containing compounds further enhances the dispersion of transition metal atoms during pyrolysis, increasing the number and density of active sites. Furthermore, the walnut-shaped structure of the electrocatalyst is retained after high-temperature heat treatment, exhibiting a large specific surface area and high porosity, which facilitates the utilization of active sites and improves mass transport and charge transfer. The preparation method provided by this invention is simple, uses abundant raw materials, and is inexpensive. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope (SEM) image of walnut-like polymeric compound A in Example 2 of the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the Fe,N-doped porous walnut-shaped carbon nanosphere electrocatalyst E in Example 2 of the present invention;

[0027] Figure 3 This is a transmission electron microscope (TEM) image of the Fe, N-doped porous walnut-shaped carbon nanosphere electrocatalyst E in Example 2 of the present invention.

[0028] Figure 4 The N2 adsorption-desorption curves of the Fe, N-doped porous walnut-shaped carbon nanosphere electrocatalyst E in Example 2 of the present invention are shown.

[0029] Figure 5 The alkaline oxygen reduction curves of Fe,N-doped porous walnut-shaped carbon nanosphere electrocatalyst E and commercial platinum / carbon electrocatalyst in Example 2 of the present invention are shown.

[0030] Figure 6 The chronocurrent curves are shown for Fe,N-doped porous walnut-shaped carbon nanosphere electrocatalyst E and commercial platinum / carbon electrocatalyst in Example 2 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] The platinum / carbon (20 wt%, Johnson Matthey) used in the following examples was commercially available. Example 1

[0033] A method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst, the method comprising the following steps:

[0034] Step 1: Preparation of nitrogen-doped porous walnut-shaped carbon nanospheres

[0035] Dopamine hydrochloride (0.6 g), a nitrogen / carbon source, 1,3,5-trimethylbenzene (1.6 ml), a surfactant P123 (0.1 g), and a triblock copolymer F127 (0.3 g) were dispersed in a water / ethanol mixture (20 / 20 ml). After sonication for 0.5 h, ammonia (1.5 ml), a polymerization initiator, was rapidly added, and the reaction was carried out at room temperature for 2.0 h. After centrifugation and washing, walnut-shaped polymeric compound A was obtained. Walnut-shaped polymeric compound A was carbonized in a N2 atmosphere at 800 ℃ for 2.0 h to obtain nitrogen-doped porous walnut-shaped carbon nanospheres B.

[0036] Step 2: Preparation of Fe, N-doped porous walnut-shaped carbon nanosphere electrocatalysts

[0037] Nitrogen-doped porous walnut-shaped carbon nanospheres B (100 mg) were dispersed in a 0.2 mM, 10 ml FeSO4 aqueous / ethanol solution and sonicated for 1.0 h to obtain a suspension. The suspension was then placed at 85°C. o In a water bath of C, Fe 2+ The Fe salt-coated nitrogen-doped porous walnut-shaped carbon nanospheres B were uniformly adsorbed on the surface of the nanospheres. After the water / ethanol was completely evaporated, the Fe salt-coated nitrogen-doped porous walnut-shaped carbon nanospheres C (75 mg) were further ground and mixed with melamine (300 mg) to obtain composite D. The composite D was carbonized in N2 atmosphere at 800 °C for 2.0 h to obtain Fe, N-doped porous walnut-shaped carbon nanosphere electrocatalyst E.

[0038] like Figure 1 As shown, SEM results indicate that the product obtained in step one is a walnut-shaped carbon nanosphere with a diameter of ~205 nm.

[0039] like Figure 2 As shown, SEM results indicate that the product obtained in step two still maintains a walnut-shaped carbon nanosphere structure with a diameter of ~203 nm.

[0040] like Figure 3 As shown, TEM results indicate that the product obtained in step two does not contain Fe-based nanoparticles.

[0041] like Figure 4 As shown in the N2 adsorption-desorption curve, the product obtained in step two has a mesoporous structure.

[0042] like Figure 5 The prepared Fe,N-doped porous walnut-shaped carbon nanosphere electrocatalyst exhibits superior alkaline ORR activity compared to commercial platinum / carbon.

[0043] like Figure 6 As shown, the prepared Fe,N-doped porous walnut-shaped carbon nanosphere electrocatalyst exhibits better alkaline ORR stability than commercial platinum / carbon. Example 2

[0044] A method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst, the method comprising the following steps:

[0045] Step 1: Preparation of nitrogen-doped porous walnut-shaped carbon nanospheres

[0046] Nitrogen / carbon source dopamine hydrochloride (0.4 g), emulsifier 1,3,5-trimethylbenzene (1.8 ml), surfactant P123 (0.2 g), and triblock copolymer F127 (0.4 g) were dispersed in a water / ethanol mixture (20 / 20 ml). After sonication for 1.0 h, ammonia water (1.5 ml) was rapidly added as a polymerization initiator, and the reaction was carried out at room temperature for 2.0 h. After centrifugation and washing, walnut-shaped polymeric compound A was obtained. Walnut-shaped polymeric compound A was carbonized in an Ar atmosphere at 800 °C for 2.0 h to obtain nitrogen-doped porous walnut-shaped carbon nanospheres B.

[0047] Step 2: Preparation of Co,N-doped porous walnut-shaped carbon nanosphere electrocatalysts

[0048] Nitrogen-doped porous walnut-shaped carbon nanospheres B (100 mg) were dispersed in a water / ethanol solution of Co(NO3)2 (0.2 mM, 10 ml) and sonicated for 1.0 h to obtain a suspension; the suspension was then placed at 80 °C. o In a water bath of C, Co 2+ The nitrogen-doped porous walnut-shaped carbon nanospheres B were uniformly adsorbed on the surface of the nanospheres. After the water / ethanol was completely evaporated, the nitrogen-doped porous walnut-shaped carbon nanospheres C (75 mg) coated with Co salt were further ground and mixed with dicyandiamide (500 mg) to obtain composite D. The composite D was placed in an Ar atmosphere and carbonized at 800 °C for 2.0 h to obtain Co,N-doped porous walnut-shaped carbon nanosphere electrocatalyst E. Example 3

[0049] A method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst, the method comprising the following steps:

[0050] Step 1: Preparation of nitrogen-doped porous walnut-shaped carbon nanospheres

[0051] Dopamine hydrochloride (0.4 g), a nitrogen / carbon source, 1,3,5-trimethylbenzene (1.8 ml), a surfactant P123 (0.2 g), and a triblock copolymer F127 (0.3 g) were dispersed in a water / ethanol mixture (20 / 20 ml). After sonication for 0.5 h, ammonia (2.0 ml), a polymerization initiator, was rapidly added, and the reaction was carried out at room temperature for 2.0 h. After centrifugation and washing, walnut-shaped polymeric compound A was obtained. Walnut-shaped polymeric compound A was placed in Ar and carbonized at 900 °C for 2.0 h to obtain nitrogen-doped porous walnut-shaped carbon nanospheres B.

[0052] Step 2: Preparation of Cu, N-doped porous walnut-shaped carbon nanosphere electrocatalysts

[0053] Nitrogen-doped porous walnut-shaped carbon nanospheres B (100 mg) were dispersed in a CuCl2 water / ethanol solution (0.3 mM, 10 ml) and sonicated for 2.0 h to obtain a suspension; the suspension was then placed at 85°C. o In a water bath of C, Cu 2+ The Cu-doped porous walnut-shaped carbon nanospheres B were uniformly adsorbed on the surface of the urea. After the water / ethanol was completely evaporated, the Cu-doped porous walnut-shaped carbon nanospheres C (75 mg) coated with Cu salt were further ground and mixed with urea (400 mg) to obtain composite D. The composite D was placed in Ar and carbonized at 900 °C for 2.0 h to obtain Cu, N-doped porous walnut-shaped carbon nanosphere electrocatalyst E. Example 4

[0054] A method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst, the method comprising the following steps:

[0055] Step 1: Preparation of nitrogen-doped porous walnut-shaped carbon nanospheres

[0056] Nitrogen / carbon source dopamine hydrochloride (0.8 g), emulsifier 1,3,5-trimethylbenzene (1.6 ml), surfactant P123 (0.2 g), and triblock copolymer F127 (0.5 g) were dispersed in a water / ethanol mixture (20 / 20 ml). After sonication for 0.5 h, ammonia water (1.5 ml) was rapidly added as a polymerization initiator, and the reaction was carried out at room temperature for 2.0 h. After centrifugation and washing, walnut-shaped polymeric compound A was obtained. Walnut-shaped polymeric compound A was carbonized in a N2 atmosphere at 800 ℃ for 1.0 h to obtain nitrogen-doped porous walnut-shaped carbon nanospheres B.

[0057] Step 2: Preparation of Mn, N-doped porous walnut-shaped carbon nanosphere electrocatalysts

[0058] Nitrogen-doped porous walnut-shaped carbon nanospheres B (100 mg) were dispersed in a water / ethanol solution of Mn(acac)2 (0.2 mM, 10 ml), and sonicated for 1.0 h to obtain a suspension; the suspension was then placed at 85°C. o In a water bath of C, Mn 2+ Mn-doped porous walnut-shaped carbon nanospheres B were uniformly adsorbed on the surface of the nanospheres. After the water / ethanol was completely evaporated, the nitrogen-doped porous walnut-shaped carbon nanospheres C (75 mg) coated with Mn salt were further ground and mixed with melamine (300 mg) to obtain composite D. Composite D was carbonized in N2 atmosphere at 800 °C for 1.0 h to obtain Mn, N-doped porous walnut-shaped carbon nanosphere electrocatalyst E. Example 5

[0059] A method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst, the method comprising the following steps:

[0060] Step 1: Preparation of nitrogen-doped porous walnut-shaped carbon nanospheres

[0061] Dopamine hydrochloride (0.6 g), a nitrogen / carbon source, 1,3,5-trimethylbenzene (1.6 ml), a surfactant P123 (0.1 g), and a triblock copolymer F127 (0.3 g) were dispersed in a water / ethanol mixture (20 / 20 ml). After sonication for 0.5 h, ammonia (1.5 ml), a polymerization initiator, was rapidly added, and the reaction was carried out at room temperature for 2.0 h. After centrifugation and washing, walnut-shaped polymeric compound A was obtained. Walnut-shaped polymeric compound A was carbonized in a N2 atmosphere at 800 ℃ for 2.0 h to obtain nitrogen-doped porous walnut-shaped carbon nanospheres B.

[0062] Step 2: Preparation of Fe, N-doped porous walnut-shaped carbon nanosphere electrocatalysts

[0063] Nitrogen-doped porous walnut-shaped carbon nanospheres B (50 mg) were dispersed in a 0.2 mM, 10 ml water / ethanol solution of Fe(NO3)2 and sonicated for 1.0 h to obtain a suspension. The suspension was then placed at 85°C. o In a water bath of C, Fe 2+ The Fe-doped porous walnut-shaped carbon nanospheres B were uniformly adsorbed on the surface of the nanospheres. After the water / ethanol was completely evaporated, the Fe-doped porous walnut-shaped carbon nanospheres C (75 mg) were further ground and mixed with melamine (300 mg) to obtain composite D. The composite D was carbonized in a N2 atmosphere at 800 °C for 2.0 h to obtain Fe, N-doped porous walnut-shaped carbon nanosphere electrocatalyst E.

[0064] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a transition metal / nitrogen-doped porous walnut-like carbon nanospheres structure electrocatalyst, characterized in that, It comprises the following steps: Step one: preparation of nitrogen-doped porous walnut-like carbon nanospheres First, disperse nitrogen / carbon source hydrochloric acid dopamine, emulsifier 1, 3, 5-trimethylbenzene, surfactant P123 and triblock copolymer F127 in water / ethanol mixed solution, after ultrasonic, quickly add polymerization director ammonia, under room temperature condition, react for 2-5 h; centrifugal washing obtains walnut-like polymer compound A; the concentration of nitrogen / carbon source hydrochloric acid dopamine in water / ethanol mixed solution is 1-50 mg / ml -1 ; The concentration of emulsifier 1, 3, 5-trimethylbenzene in water / ethanol mixed solution is 0.01-1 ml / ml -1 ; The concentration of surfactant P123 in water / ethanol mixed solution is 1-10 mg / ml -1 ; The concentration of triblock copolymer F127 in water / ethanol mixed solution is 1-10 mg / ml -1 ; The concentration of polymerization director ammonia in water / ethanol mixed solution is 0.01-1 ml / ml -1 ; The ultrasonic time of ultrasonic is 0.1-1 h; Then, the walnut-like polymer compound A is carbonized at a temperature of 600-100 ℃ in an inert atmosphere for 0.5-4 h to obtain nitrogen-doped porous walnut-like carbon nanospheres B. Step two: preparation of transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst First, the nitrogen-doped porous walnut-like carbon nanospheres B obtained in step one are dispersed in a water / ethanol solution containing a transition metal salt, and after ultrasonic treatment, a suspension is obtained; the concentration of the nitrogen-doped porous walnut-like carbon nanospheres B in the water / ethanol solution of the transition metal salt is 1-20 mg / ml -1 ; the concentration of the transition metal salt in the water / ethanol solution is 0.1-1 mmol / l -1 ; the ultrasonic treatment time is 0.1-2 h; Secondly, the suspension is placed in a water bath at 40-90 ℃ to make the transition metal cations uniformly adsorbed on the surface of the nitrogen-doped porous walnut-like carbon nanospheres B. Thirdly, when the water / ethanol is completely volatilized, the nitrogen-doped porous walnut-like carbon nanospheres C coated with transition metal salt are further uniformly mixed with nitrogen-containing compounds to obtain a composite D; the mass ratio of the nitrogen-doped porous walnut-like carbon nanospheres C coated with transition metal salt to the nitrogen-containing compounds is 0.1-1. Finally, the composite D is carbonized at a temperature of 600-1100 ℃ in an inert atmosphere for 0.5-4 h to obtain a transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst E.

2. The method for preparing a transition metal / nitrogen-doped porous carbon nanosheet structure electrocatalyst according to claim 1, characterized in that: In step two, the transition metal salt is one or two or more of chlorides, sulfates, nitrates, and acetylacetone salts of iron, cobalt, nickel, copper, and manganese.

3. The method of claim 1, wherein the transition metal / nitrogen-doped porous carbon nanospheroid structure electrocatalyst is prepared by the following steps: (1) preparing a transition metal / nitrogen-doped porous carbon nanospheroid structure electrocatalyst precursor; and (2) calcining the transition metal / nitrogen-doped porous carbon nanospheroid structure electrocatalyst precursor. In step two, the nitrogen-containing compound is one or a mixture of two or more of urea, dicyandiamide, 4,4'-dipyridyl, 2,2'-dipyridyl, o-phenanthroline, melamine, phenylenediamine, and 4,4'-diaminotriphenyl.

4. The method for preparing a transition metal / nitrogen-doped porous walnut-shaped carbon nanosphere structure electrocatalyst according to claim 1, characterized in that: In step one and step two, the inert atmosphere is one or a mixture of two or more of helium, argon, and nitrogen.

5. A transition metal / nitrogen-doped porous carbon nanospheroid structure electrocatalyst, characterized in that: The transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst is prepared by the method of any one of claims 1-4.

6. Use of the transition metal / nitrogen-doped porous walnut-like carbon nanosphere structure electrocatalyst of claim 5 in the oxygen reduction reaction of the cathode of a hydrogen-oxygen exchange membrane fuel cell.

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