Porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction and preparation method thereof

Abstract

The application provides a porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction and a preparation method. The preparation method comprises the following steps: adding 4,4-diamino diphenyl ether and pyromellitic dianhydride into a solvent, uniformly mixing, and preparing a polyamide acid precursor spinning solution; electrospinning the prepared polyamide acid precursor spinning solution to prepare polyamide acid nanofibers; immersing the prepared polyamide acid nanofibers in a mixed metal salt solution containing cobalt salt, lanthanum salt and zinc salt to prepare polyamide acid nanofiber precursors loaded with metal ions; and performing programmed temperature heat treatment on the prepared polyamide acid nanofiber precursors loaded with metal ions in a protective atmosphere to prepare the porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction. The prepared porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction has excellent electrochemical oxygen reduction reaction and oxygen evolution reaction bifunctional catalytic activity.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterojunction and its preparation method. Background Technology

[0002] With rapid socio-economic development, traditional fossil fuels such as coal, oil, and natural gas are facing an increasing crisis of scarcity. Large-scale use of these non-renewable resources can easily cause irreversible damage to the ecological environment. Meanwhile, renewable energy sources such as wind and solar power rely on supporting energy storage systems to ensure a continuous and stable output of electricity. Zinc-air batteries, due to their flat discharge platform, high energy density, environmental friendliness, and low cost, have become a promising energy storage technology.

[0003] In zinc-air batteries, the electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key processes determining their performance. Currently, noble metal materials such as Pt and Ru exhibit excellent electrocatalytic activity in both ORR and OER; however, the scarcity and high cost of these precious metals significantly limit their large-scale application in zinc-air batteries. Therefore, developing non-noble metal bifunctional electrocatalysts for ORR / OER that combine high activity with low cost has become a crucial direction for advancing this field, possessing significant research value and broad application prospects.

[0004] One-dimensional carbon nanofibers, as electrocatalyst supports, possess structural advantages such as high aspect ratio, large specific surface area, excellent conductivity, and low preparation cost. These properties facilitate rapid electron conduction along the fiber axis. However, pure carbon materials themselves have limited catalytic activity for electrochemical oxygen reduction and oxygen evolution reactions, making it difficult to provide sufficient reactive centers. Therefore, it is usually necessary to introduce electrocatalytically active components into their structure to enhance overall performance. For example, the prior art CN117026425B discloses the preparation of iron-cobalt alloy-doped carbon nanofiber electrocatalysts through electrostatic melting combined with high-temperature carbonization. This type of method introduces a zinc source and uses zinc oxide to etch the carbon film encapsulating the alloy particles at high temperature, thereby exposing more alloy active sites and improving catalytic performance to a certain extent. However, such catalysts based on bimetallic alloys still have shortcomings. First, the electrochemical oxygen reduction reaction and the oxygen evolution reaction are two processes with opposite electron transfer directions. The surface electronic structure of single-metal phase catalysts, represented by iron-cobalt alloys, needs to simultaneously satisfy the optimal adsorption of intermediates of both the electrochemical oxygen reduction reaction and the oxygen evolution reaction. This is thermodynamically difficult to achieve, resulting in limited improvement in bifunctional catalytic activity. Second, improvements are mostly focused on physically exposing existing active sites using methods such as pore-forming and etching, while breakthroughs in the chemical properties of the active sites themselves are limited. Third, the accessibility and utilization rate of the active sites of this electrocatalyst are limited. Although pore-forming technology increases the specific surface area of ​​the support, during high-temperature carbonization, the newly generated metal nanoparticles are easily encapsulated by amorphous carbon or graphitic carbon layers. Although this carbon encapsulation effect can stabilize the metal particles, it also blocks the contact between the active sites and the electrolyte. The actual exposed active interface that can be used for catalysis is far lower than the theoretical value. Fourth, transition metals such as iron are prone to oxidation, dissolution, and agglomeration under strongly alkaline and high-potential operating conditions, leading to alloy structure destruction and rapid activity decay, posing a challenge to long-term stability.

[0005] Therefore, there is an urgent need in this field for a non-precious metal bifunctional electrocatalyst that combines high activity and low cost for both electrochemical oxygen reduction and oxygen evolution reactions. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure and its preparation method.

[0007] In a first aspect, this application provides a method for preparing a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure, comprising the following steps:

[0008] S1: Add 4,4-diaminodiphenyl ether and pyromellitic dianhydride to the solvent and mix evenly to prepare a polyamic acid precursor spinning solution;

[0009] S2: Electrospin the polyamic acid precursor spinning solution obtained in step S1 to obtain polyamic acid nanofibers.

[0010] S3: The polyamic acid nanofibers obtained in step S2 are impregnated in a mixed metal salt solution containing cobalt salt, lanthanum salt and zinc salt to obtain a polyamic acid nanofiber precursor loaded with metal ions.

[0011] S4: The polyamic acid nanofiber precursor loaded with metal ions obtained in step S3 is subjected to programmed temperature heat treatment under a protective atmosphere to obtain a porous carbon nanofiber electrocatalyst loaded with a cobalt / lanthanum hydroxide heterostructure.

[0012] The programmed temperature rise heat treatment process involves raising the temperature to 300°C at a rate of 2°C / min, then raising it to 600°C at a rate of 5°C / min, and finally raising it to 900°C at a rate of 3°C / min, and holding it at that temperature for 30 minutes.

[0013] Further, in step S1, the molar ratio of 4,4-diaminodiphenyl ether to pyromellitic dianhydride is (0.98-1.02):1; preferably, the molar ratio of 4,4-diaminodiphenyl ether to pyromellitic dianhydride is 1:1.

[0014] In step S1, the molar ratio of 4,4-diaminodiphenyl ether to pyromellitic dianhydride is (0.98-1.02):1. Under this ratio, the functional groups of 4,4-diaminodiphenyl ether and pyromellitic dianhydride react almost completely, and a high molecular weight, high viscosity polyamic acid solution can be prepared. This is a prerequisite for successfully obtaining continuous and uniform polyamic acid nanofibers by electrospinning.

[0015] Furthermore, the solvent in step S1 is N,N-dimethylformamide.

[0016] Furthermore, the solid content of the polyamic acid precursor spinning solution obtained in step S1 is 15wt%-25wt%.

[0017] Furthermore, the electrospinning process parameters in step S2 include a spinning voltage of 20-30 kV, a receiving distance of 10-20 cm, and a feed speed of 0.5-2.0 mL / h.

[0018] Furthermore, in step S3, the molar ratio of cobalt, lanthanum, and zinc in the mixed metal salt solution containing cobalt, lanthanum, and zinc is 1:(1-1.2):(4-6); preferably, the molar ratio of cobalt, lanthanum, and zinc is 1:1:5.

[0019] Furthermore, the total concentration of the mixed metal salt solution in step S3 is 0.1 mol / L-1.0 mol / L; preferably, the total concentration of the mixed metal salt solution is 0.1 mol / L-0.7 mol / L.

[0020] Furthermore, in step S3, the cobalt salt, lanthanum salt, and zinc salt are independently selected from acetate, nitrate, or chloride; preferably, the cobalt salt, lanthanum salt, and zinc salt are acetate.

[0021] Secondly, this application provides a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure, which is prepared by the method described in the first aspect.

[0022] Furthermore, the porous carbon nanofiber electrocatalyst with a supported cobalt / lanthanum hydroxide heterojunction uses porous carbon nanofibers as a support, on which a cobalt / lanthanum hydroxide heterojunction formed in situ from cobalt nanoparticles and lanthanum hydroxide nanoparticles is loaded.

[0023] Furthermore, the surface of the porous carbon nanofibers has a porous structure generated by in-situ etching.

[0024] Thirdly, this application provides a metal-air battery, including a porous carbon nanofiber electrocatalyst with a supported cobalt / lanthanum hydroxide heterojunction prepared by the method of the first aspect.

[0025] Furthermore, the metal-air battery is a zinc-air battery.

[0026] In the preparation method of the first aspect of this application, the molar ratio of cobalt, lanthanum, and zinc in the mixed metal salt solution containing cobalt, lanthanum, and zinc is 1:(1-1.2):(4-6). The total concentration of the mixed metal salt solution in step S3 is 0.1 mol / L-1.0 mol / L, and the molar ratio of cobalt to lanthanum is 1:(1-1.2). A slight excess of lanthanum helps to form a complete coating or a richer interface around the cobalt particles, thereby providing more alkaline sites to promote the oxygen evolution reaction. The amount of zinc ensures moderate etching of carbon nanofibers, allowing the carbon nanofibers to maintain their macroscopic morphology and electrical integrity while generating a rich, interconnected porous structure, preventing insufficient or excessive etching. Moderate etching also removes the thin layer of carbon coating on the surface of the cobalt / lanthanum hydroxide heterojunction, allowing its active sites to be more fully exposed to the electrolyte, solving the common carbon encapsulation problem in high-temperature carbonization. The pore-forming process of zinc is highly synergistic with the formation process of the cobalt / lanthanum hydroxide heterojunction. The porous structure provides the heterojunction with a large loading space and exposed surface, while the high activity of the heterojunction fully utilizes the mass transfer advantages of the porous structure. The molar ratio of cobalt, lanthanum, and zinc achieves the optimal match between the degree of pore-forming, the composition of the heterojunction, and the strength of the support, ensuring that while constructing a high specific surface area porous conductive network, the active centers of the cobalt / lanthanum hydroxide heterojunction with a tight interface can be synthesized in situ and fully exposed.

[0027] By controlling the total concentration of the mixed metal salt solution within 0.1-1.0 mol / L, the efficient and uniform loading of the active components is effectively ensured. This concentration range avoids insufficient loading of active centers due to excessively low concentrations, and also prevents problems such as salt surface crystallization, pore blockage, and precursor structure damage caused by excessively high concentrations.

[0028] In the preparation method of the first aspect of this application, the programmed temperature heat treatment process in step S4 involves heating to 300°C at a rate of 2°C / min, then to 600°C at a rate of 5°C / min, and finally to 900°C at a rate of 3°C / min, holding at that temperature for 30 min. During the low-temperature segment of the programmed temperature rise to 300°C, a mild imidization process occurs, where polyamic acid undergoes dehydration and cyclization to transform into polyimide. During the medium-temperature segment of the programmed temperature rise to 600°C, the polyimide begins to carbonize, and simultaneously, zinc acetate decomposes into zinc oxide. The slow temperature rise provides a solid-phase reaction between zinc oxide and carbon. Sufficient reaction time was provided to initiate the carbonization and pore-forming process. At a programmed temperature of 900°C, carbon atoms rearranged, increasing the degree of graphitization and dramatically enhancing conductivity. Simultaneously, the residual carbon reacted completely with zinc oxide, fixing the pore structure. At 900°C, zinc completely volatilized, ensuring that the final product was free of zinc residue. Under a carbon-reducing atmosphere, cobalt and lanthanum precursors were converted into cobalt and lanthanum hydroxide. The slow heating at this stage allowed sufficient surface migration and interfacial contact time for metallic cobalt and lanthanum hydroxide, enabling in-situ self-assembly to form a tight heterojunction.

[0029] Compared with the prior art, this application includes the following beneficial technical effects:

[0030] The method for preparing porous carbon nanofiber electrocatalysts supported on cobalt / lanthanum hydroxide heterojunctions provided in this application involves a carbonization process where zinc oxide, generated from the decomposition of zinc acetate, reacts with carbon to achieve in-situ etching of the carbon matrix, forming porous carbon nanofibers with micropores and / or mesopores. These porous carbon nanofibers exhibit high conductivity and a large specific surface area. This porous structure not only provides abundant space for active sites but also significantly enhances mass transfer efficiency due to the porous structure generated by in-situ etching. Simultaneously, lanthanum acetate and cobalt acetate are converted into elemental cobalt and lanthanum hydroxide during carbonization, forming a cobalt / lanthanum hydroxide heterojunction, which grows in situ on the porous carbon nanofibers. The porous structure of the carbon nanofibers fully exposes the cobalt / lanthanum hydroxide heterojunction. This heterojunction, through interfacial electron transfer, enriches the cobalt side with electrons to optimize the oxygen reduction reaction and depletes the lanthanum hydroxide side to optimize the oxygen evolution reaction, achieving highly efficient synergy of dual-functional activities. This allows the heterojunction to act as a highly efficient active center driving the catalytic reaction, greatly enhancing the oxygen electrocatalytic performance of the prepared electrocatalyst.

[0031] Furthermore, lanthanum hydroxide is chemically stable in alkaline environments and binds firmly to cobalt particles, preventing their aggregation, migration, or loss. Simultaneously, its alkaline surface may mitigate the corrosion of the carbon support, thereby endowing the prepared electrocatalyst with excellent long-cycle stability. Attached Figure Description

[0032] The present application will be described in further detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of this disclosure. Furthermore, unless specifically indicated, the drawings are only schematic representations of the composition or structure of the described objects and may contain exaggerated depictions, and the drawings are not necessarily drawn to scale.

[0033] Figure 1 A schematic diagram illustrating the preparation method of porous carbon nanofiber electrocatalysts supported on cobalt / lanthanum hydroxide heterostructures.

[0034] Figure 2 Transmission electron microscopy (TEM) images of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofiber electrocatalysts supported on cobalt / lanthanum hydroxide heterostructures are shown below. Specifically, A is a TEM image of cobalt-loaded carbon nanofibers; B is a TEM image of lanthanum hydroxide-loaded carbon nanofibers; C is a TEM image of porous carbon nanofibers; and D is a TEM image of a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure.

[0035] Figure 3 XRD patterns of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofiber electrocatalysts supported on cobalt / lanthanum hydroxide heterojunctions.

[0036] Figure 4 The graph shows the oxygen reduction reaction performance of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofibers with cobalt / lanthanum hydroxide heterojunctions.

[0037] Figure 5 The graph shows the oxygen evolution reaction performance of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofibers with cobalt / lanthanum hydroxide heterostructures. Detailed Implementation

[0038] The following is in conjunction with the appendix Figures 1 to 5 This application will be described in detail.

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0040] Chemicals and reagents

[0041] Unless otherwise specified, all other reagents used in the embodiments of this application are from conventional commercially available products.

[0042] The specific implementation method of this application is as follows.

[0043] Example 1

[0044] This embodiment provides a method for preparing a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure, such as... Figure 1 As shown, it includes the following steps:

[0045] S1: 2.68 g of 4,4-diaminodiphenyl ether was added to 14.4 g of N,N-dimethylformamide, and 2.92 g of pyromellitic dianhydride was added in batches while stirring. The mixture was stirred for 2 h to obtain a polyamic acid precursor spinning solution.

[0046] S2: Add the polyamic acid precursor spinning solution obtained in step S1 into the electrospinning device. Control the distance between the spinning needle with a diameter of 1 mm and the fiber receiving device at 15 cm. Use a booster to make the spinning solution extrusion speed 1 mL / h and the spinning voltage 25 kV. Under the action of the high voltage electrostatic field, the spinning solution is fully stretched and forms polyamic acid nanofibers on the collecting plate.

[0047] S3: Dissolve 2 mmol cobalt acetate, 2 mmol lanthanum acetate, and 10 mmol zinc acetate in 20 mL of deionized water to prepare a mixed metal salt solution. Then, completely immerse the polyamic acid nanofibers prepared in step S2 in the mixed metal salt solution to obtain a metal ion-loaded polyamic acid nanofiber precursor.

[0048] S4: The polyamic acid nanofiber precursor loaded with metal ions obtained in step S3 is heated to 300°C at 2°C / min in a nitrogen atmosphere, then to 600°C at 5°C / min, and finally to 900°C at 3°C / min and held at that temperature for 30 min to carry out imidization and carbonization reactions, thereby obtaining a porous carbon nanofiber electrocatalyst loaded with a cobalt / lanthanum hydroxide heterostructure.

[0049] The porous carbon nanofiber electrocatalyst with supported cobalt / lanthanum hydroxide heterostructure obtained in step S4 was dispersed in a mixture of 250 μL N,N-dimethylformamide and 250 μL deionized water, and then 50 μL of 5% Nafion solution was added dropwise. The mixture was ultrasonically dispersed for 30 min to obtain catalyst ink. The catalyst ink was then loaded onto a glassy carbon electrode by drop coating and electrochemical tests were performed.

[0050] Based on Example 1, this application studied the composition of the mixed metal salt solution in step S3. The specific parameters are shown in Table 1. Other raw material components and process parameters are the same as in Example 1.

[0051] Table 1. Compositional parameters of mixed metal salt solutions

[0052]

[0053] This application conducted transmission electron microscopy, XRD, oxygen reduction reaction performance tests, and oxygen evolution reaction performance tests on the porous carbon nanofiber electrocatalysts, cobalt-supported carbon nanofibers, lanthanum hydroxide-supported carbon nanofibers, and porous carbon nanofibers prepared in Examples 1-4, respectively. The results are as follows: Figures 2-5 As shown.

[0054] Figure 2 Transmission electron microscopy (TEM) images of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofiber electrocatalysts supported on cobalt / lanthanum hydroxide heterostructures are shown. Co@CNF represents the cobalt-loaded carbon nanofibers prepared in Example 2, La(OH)3 represents the lanthanum hydroxide-loaded carbon nanofibers prepared in Example 3, Zn@PCNF represents the porous carbon nanofibers prepared in Example 4, and Co / La(OH)3@PCNF represents the porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure prepared in Example 1. Figure 2 As can be seen, the surface of carbon nanofibers loaded with cobalt nanoparticles exhibits a large number of carbon nanotube structures. The surface of carbon nanofibers loaded with lanthanum hydroxide nanoparticles is covered with a dense layer of metal nanoparticles. Porous carbon nanofibers have abundant carbon bubble structures. The porous carbon nanofibers loaded with cobalt / lanthanum hydroxide heterojunctions have a large number of protrusions and carbon nanotubes on their surface, and are also loaded with dense metal nanoparticles, indicating that the catalyst has both a large specific surface area structure and a high density of active sites, which is expected to synergistically improve its electrochemical performance.

[0055] Figure 3XRD patterns of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofiber electrocatalysts with cobalt / lanthanum hydroxide heterojunctions are shown. Co@CNF represents the cobalt-loaded carbon nanofibers prepared in Example 2, La(OH)3 represents the lanthanum hydroxide-loaded carbon nanofibers prepared in Example 3, Zn@PCNF represents the porous carbon nanofibers prepared in Example 4, and Co / La(OH)3@PCNF represents the porous carbon nanofiber electrocatalyst with a cobalt / lanthanum hydroxide heterojunction prepared in Example 1. Figure 3 Analysis revealed that cobalt acetate was reduced to metallic cobalt during carbonization. Lanthanum acetate was converted to lanthanum hydroxide. Zinc acetate was converted to zinc vapor and completely volatilized, leaving only characteristic carbon peaks. The presence of both cobalt and lanthanum hydroxide peaks in the sample with the supported cobalt / lanthanum hydroxide heterojunction indicates the formation of a cobalt-lanthanum hydroxide heterojunction by the catalyst; however, no zinc diffraction peaks were detected, further confirming that zinc was completely volatilized during carbonization.

[0056] Figure 4 The graphs show the oxygen reduction reaction performance of cobalt-loaded carbon nanofibers, lanthanum hydroxide-loaded carbon nanofibers, porous carbon nanofibers, and porous carbon nanofiber electrocatalysts supported on cobalt / lanthanum hydroxide heterojunctions. In these graphs, Co@CNF represents the cobalt-loaded carbon nanofibers prepared in Example 2, La(OH)3 represents the lanthanum hydroxide-loaded carbon nanofibers prepared in Example 3, Zn@PCNF represents the porous carbon nanofibers prepared in Example 4, and Co / La(OH)3@PCNF represents the porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterojunction prepared in Example 1. Figure 4 As shown, the half-wave potential of cobalt-loaded carbon nanofibers and lanthanum hydroxide-loaded carbon nanofibers is 0.82 V, the half-wave potential of porous carbon nanofibers is 0.69 V, while the half-wave potential of porous carbon nanofibers loaded with cobalt / lanthanum hydroxide heterojunction is increased to 0.88 V, indicating that the catalyst has excellent oxygen reduction reaction catalytic performance.

[0057] Figure 5 The graphs show the oxygen evolution reaction performance of porous carbon nanofiber electrocatalysts supported on cobalt, lanthanum hydroxide, and cobalt / lanthanum hydroxide heterojunctions. Co@CNF represents the cobalt-supported carbon nanofibers prepared in Example 2, La(OH)3 represents the lanthanum hydroxide-supported carbon nanofibers prepared in Example 3, Zn@PCNF represents the porous carbon nanofibers prepared in Example 4, and Co / La(OH)3@PCNF represents the cobalt / lanthanum hydroxide-supported porous carbon nanofiber electrocatalyst prepared in Example 1. Figure 5 As shown, at 10 mA cm -2At a given current density, the potential of cobalt-loaded carbon nanofibers is 1.64 V, corresponding to an overpotential of 410 mV. Carbon nanofibers loaded with lanthanum hydroxide and porous carbon nanofibers exhibit almost no oxygen evolution reaction activity. However, porous carbon nanofibers loaded with a cobalt / lanthanum hydroxide heterostructure have a potential of 1.53 V and an overpotential of only 300 mV. Figure 4 and Figure 5 The results show that the prepared electrocatalyst has good bifunctional catalytic activity for both oxygen reduction and oxygen evolution reactions, and is suitable for zinc-air battery systems.

[0058] In summary, the porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterojunction prepared in this application possesses the following advantages: metallic zinc has a low melting and boiling point, reacting with carbon to form porous carbon nanofibers; porous carbon nanofibers exhibit strong conductivity, large specific surface area, and numerous attachable active sites; the cobalt / lanthanum hydroxide heterojunction possesses powerful catalytic capabilities for oxygen reduction and oxygen evolution reactions; therefore, the porous carbon nanofiber framework provides conductive pathways and a large number of attachable sites, while the fully exposed cobalt / lanthanum hydroxide heterojunction provides numerous reactive sites for oxygen reduction and oxygen evolution reactions, greatly enhancing the oxygen electrocatalytic performance of the electrode material.

[0059] The present application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the embodiments above are only for the purpose of helping to understand the present disclosure and its core ideas. It should be noted that those skilled in the art can make several improvements and modifications to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure, characterized in that, Includes the following steps: S1: Add 4,4-diaminodiphenyl ether and pyromellitic dianhydride to the solvent and mix evenly to prepare a polyamic acid precursor spinning solution; S2: Electrospin the polyamic acid precursor spinning solution obtained in step S1 to obtain polyamic acid nanofibers. S3: The polyamic acid nanofibers obtained in step S2 are impregnated in a mixed metal salt solution containing cobalt salt, lanthanum salt and zinc salt to obtain a polyamic acid nanofiber precursor loaded with metal ions. S4: The polyamic acid nanofiber precursor loaded with metal ions obtained in step S3 is subjected to programmed temperature heat treatment under a protective atmosphere to obtain a porous carbon nanofiber electrocatalyst loaded with a cobalt / lanthanum hydroxide heterostructure. The programmed temperature rise heat treatment process is as follows: the temperature is increased to 300°C at 2°C / min, then increased to 600°C at 5°C / min, and finally increased to 900°C at 3°C / min, and held at that temperature for 30 min. In step S3, the molar ratio of cobalt, lanthanum, and zinc in the mixed metal salt solution containing cobalt, lanthanum, and zinc is 1:(1-1.2):(4-6). The total concentration of the mixed metal salt solution in step S3 is 0.1 mol / L-0.7 mol / L.

2. The method for preparing the porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure as described in claim 1, characterized in that, In step S1, the molar ratio of 4,4-diaminodiphenyl ether to pyromellitic dianhydride is (0.98-1.02):

1.

3. The method for preparing the porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure as described in claim 1, characterized in that, The solid content of the polyamic acid precursor spinning solution obtained in step S1 is 15wt%-25wt%.

4. The method for preparing the porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure as described in claim 1, characterized in that, In step S3, the cobalt salt, lanthanum salt, and zinc salt are independently selected from acetate, nitrate, or chloride.

5. A porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterostructure, prepared by any one of the preparation methods of claims 1-4.

6. The porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterojunction as described in claim 5, characterized in that, The porous carbon nanofiber electrocatalyst with a supported cobalt / lanthanum hydroxide heterojunction uses porous carbon nanofibers as a support, on which a cobalt / lanthanum hydroxide heterojunction formed in situ from cobalt nanoparticles and lanthanum hydroxide nanoparticles is loaded.

7. The porous carbon nanofiber electrocatalyst supported on a cobalt / lanthanum hydroxide heterojunction as described in claim 5, characterized in that, The porous carbon nanofibers have a porous structure formed by in-situ etching.

8. A metal-air battery comprising a porous carbon nanofiber electrocatalyst with a supported cobalt / lanthanum hydroxide heterojunction prepared by any one of the preparation methods of claims 1-4.

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