ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies and Al-air battery

Abstract

The present invention relates to a ZIF-L-derived multidimensional cross-linked Fe-N-C catalyst containing oxygen vacancies and an Al-air battery. The present invention has the following beneficial effects: 1. A multidimensional cross-linked Fe-N-C electrocatalyst containing oxygen vacancies is prepared by using ZIF-L as a precursor and co-pyrolyzing Fe(NO3)3·9H2O and carbon nanomaterials, which has a high specific surface area and a strong electron-proton transfer ability. 2. The multidimensional cross-linked Fe-N-C catalyst containing oxygen vacancies derived from the ZIF-L achieves a higher ORR electrocatalytic performance with a lower oxygen vacancy concentration, specifically showing a higher half-wave potential and current density. 3. The multidimensional cross-linked Fe-N-C catalyst containing oxygen vacancies derived from the ZIF-L has a higher Al-air battery performance, specifically showing a higher power density. Finally, the preparation method of the present invention has the advantages of abundant raw material sources and low cost, a simple preparation process and easy industrial development.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing cathode oxygen reduction reaction catalysts for aluminum-air batteries, and in particular to a method for preparing a ZIF-L-derived Fe-NC catalyst having a multidimensional cross-linked structure containing oxygen vacancies, a ZIF-L-derived Fe-NC catalyst having a multidimensional cross-linked structure containing oxygen vacancies prepared using the method, an Al-air battery comprising the catalyst, and a method for preparing the Al-air battery. Background Art

[0002] With high theoretical specific energy (8100Wh·kg -1 ) is a device that uses a high-purity Al alloy as the negative electrode, oxygen absorbed from the air as the positive electrode, and KOH or NaOH solution as the electrolyte to directly convert chemical energy into electrical energy. The reaction process of the Al-air battery makes this type of battery not subject to the control of the Carnot cycle. It has many advantages such as high energy density, low environmental pollution, and a wide range of material sources, and has become one of the research hotspots at home and abroad. However, the kinetics of the reduction reaction of oxygen at the cathode of the Al-air battery is too slow, which limits the commercial development of the Al-air battery. Therefore, the development of the electrochemical performance of the catalyst at the oxygen reduction reaction position of the cathode air electrode of the Al-air battery has an important role in promoting the large-scale development of the Al-air battery. Although Pt / C catalyst has become the most widely used catalyst material on the market, it is limited by its low reserves and high cost. It is particularly important to explore non-precious metal catalysts and non-metallic catalysts.

[0003] Among non-precious metal catalysts, carbon-based materials offer advantages such as low cost, high conductivity, and rapid mass transfer. However, due to the uniform distribution of electron clouds around carbon atoms, the electrocatalytic activity of carbon-based catalysts is poor. Heteroatom doping can effectively change the electron cloud distribution around carbon atoms. For example, the introduction of heteroatoms such as Fe and N enables Fe-NC catalysts to effectively reduce the adsorption energy of oxygen intermediates, thereby improving the electrocatalytic activity of the catalyst. However, Fe-NC catalysts currently also face disadvantages such as a small number of active sites and low activity density.

[0004] Metal-organic frameworks (MOFs) have a regular porous structure and rich structural designability, making them an ideal support for designing transition metal-based catalysts. The use of MOFs to design low-cost, high-performance transition metal-nitrogen-carbon (MNC) ORR electrocatalysts has attracted widespread attention from researchers. Among them, zeolitic imidazolate frameworks (ZIFs), as a member of the metal framework organic structure (MOFs), can provide a large number of microporous structures, making it possible to expose more active sites. In addition, ZIFs can effectively avoid the aggregation of metal atoms and improve mass transfer and heat transfer rates, making them one of the promising materials for the preparation of excellent oxygen reduction catalysts.

[0005] Oxygen vacancies, a type of metal oxide defect, are formed when oxygen in the crystal lattice of metal oxides is separated under specific external conditions (such as high temperature, reduction treatment, etc.), resulting in oxygen deficiency. The generation of oxygen vacancies (Vo) in metal oxides can create unsaturated sites, enhance the adsorption of reactants, and thus affect the catalytic performance of the oxygen reduction reaction. In addition, the construction of oxygen vacancy defects can promote the efficient transfer of electrons from the catalyst surface to oxygen molecules by affecting the electronic structure and geometric structure. Therefore, using ZIFs as metal-organic framework precursors to create oxygen vacancies and provide more active centers for catalysts has become one of the important means to improve catalytic activity.

[0006] Prior art CN109100405B discloses a nitrogen-doped porous C / CeO with adjustable oxygen vacancy concentration. 2-x Preparation method and application of nanocomposite materials. This catalyst uses ZIF-67 as a metal-organic framework. CeO2 is generated at high temperature, and under low oxygen partial pressure conditions, oxygen atoms located in the interstitial spaces of CeO2 escape to form oxygen vacancies. The catalyst prepared in this way is used for highly sensitive detection of hydrogen peroxide at low potentials and has excellent anti-interference properties. However, high-temperature treatment causes CeO2 to undergo or increase particle size, thereby reducing the specific surface area of ​​CeO2. In addition, the prior art CN113563601A also discloses a cation-deficient ZIF-type porous material and its preparation method and application. This material uses ZIF-8 as a metal-organic framework precursor, synthesizes imidazolyl cationic ligands in an organic solvent, and reacts them with metal salts to obtain a cation-deficient ZIFs-type porous material. However, the ZIF-8 used has a well-defined 3D pore structure, which is not conducive to the mass transfer of reactive oxygen intermediates, resulting in poor electrochemical performance.

[0007] Given the aforementioned shortcomings of existing technologies, increasing the specific surface area of ​​defective catalysts and enhancing their mass transfer rates have become key goals in improving defective electrocatalysts. Hybrid / multidimensional hierarchical structures can achieve the synergistic integration of different structural units, effectively increasing the specific surface area of ​​the catalyst and the dispersion of active particles, improving the aggregation of active particles, and increasing the utilization of active sites.

[0008] Prior art CN109174150A discloses a preparation method and application of a CQDs / CdIn2S4 / N-rGO multidimensional photocatalyst. This catalyst is synthesized by hydrothermally synthesizing a CQDs / CdIn2S4 / N-rGO composite catalyst by modifying less active graphene to form reduced graphene oxide, achieving the purpose of degrading 2,4-dichlorophenol. The multidimensional structure creates a heterojunction, improving the catalyst's catalytic performance. However, the hydrothermal synthesis conditions are relatively harsh and energy consumption is high, making it less practical. Secondly, prior art CN111097395A discloses a multidimensional TiO2 "facet heterojunction" cubic empty box catalyst constructed using a seed-grown method and its application. The formation of the multidimensional TiO2 "facet heterojunction" increases the specific surface area, improving the catalyst's selectivity and catalytic performance, but is thermodynamically unstable. Furthermore, prior art CN111146447B discloses an alloy catalyst with a multidimensional pore structure, its preparation method, and its application. The electrochemically active area of ​​the multidimensional catalyst prepared using this method is more than 3.5 times that of commercial Pt / C catalysts. However, the alloy nanoparticles of noble metals and transition metals prepared by this method are relatively expensive, reducing the practicality of the catalyst.

[0009] Therefore, how to better utilize ZIFs as precursors to prepare Fe-NC oxygen reduction catalysts that are conducive to mass transfer and have excellent catalytic activity, and to develop economical and practical Fe-NC-based air electrodes with excellent electrochemical performance, thereby reducing the cost of Al-air batteries, is a technical problem that needs to be solved urgently. This research will promote the industrial development of Al-air batteries. Summary of the Invention

[0010] Problems to be solved by the invention

[0011] In this context, the present invention has conducted an in-depth study on the preparation process of Fe-NC-based air electrodes, and for the first time proposed a preparation method for ZIF-L-derived multidimensional cross-linked Fe-NC catalysts containing oxygen vacancies and their application in Al-air batteries, with the aim of providing a preparation method for air electrodes with a simple preparation process, low price and high catalytic performance.

[0012] A multidimensional cross-linked Fe-NC catalyst rich in oxygen vacancies was derived and synthesized using ZIF-L as a precursor. On the one hand, based on the CN produced by calcining ZIF-L, carbon nanomaterials were added to increase the specific surface area of ​​the catalyst. By changing the type of carbon nanomaterials, the structure of the catalyst was regulated to achieve the purpose of constructing a multidimensional cross-linked structure and forming a highly conductive channel, thereby improving the conductivity and catalytic activity of the catalyst. On the other hand, by regulating the concentration of oxygen vacancies in the catalyst, the electronic structure and geometric structure of the catalyst active center were adjusted, unsaturated sites were created, the adsorption of reactants was enhanced, and the electrocatalytic performance of the catalyst was improved.

[0013] Solutions for solving problems

[0014] The present invention relates to:

[0015] 1. A method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies, characterized by comprising the following steps:

[0016] Step (1): Prepare 0.8-1.2 mol·L -1 Imidazole aqueous solution and 0.1~1mol·L -1 Soluble zinc salt aqueous solution and 0.05~0.1mol·L -1 Aqueous solution of soluble iron salts;

[0017] Step (2): mixing the imidazole aqueous solution and the soluble zinc salt aqueous solution in step (1) and stirring for 12 to 24 hours to synthesize 2D ZIF-L leaf-like crystals;

[0018] Step (3): weighing a carbon nanomaterial at a ratio of 80 to 110 g relative to 1 mol of Fe ions, and then adding the carbon nanomaterial to a mixed solvent consisting of acetone, ethanol, and distilled water in a volume ratio of 1:1:1, and ultrasonically treating the mixture for 0.1 h to 1 h to form a uniform carbon nanomaterial suspension;

[0019] Step (4), centrifuging the carbon nanomaterial suspension obtained in step (3) and vacuum drying to obtain a pretreated carbon nanomaterial;

[0020] Step (5): mixing the soluble iron salt aqueous solution with the pretreated carbon nanomaterial in step (4) and stirring for 0.5 h to 1.5 h to obtain a mixed solution, which is recorded as: Fe-C mixed solution;

[0021] Step (6): mixing the ZIF-L leaf-shaped crystals obtained in step (2) with the Fe-C mixed solution in step (5) and stirring for 24 to 85 hours;

[0022] Step (7): centrifuging the mixed solution stirred in step (6) and then vacuum drying to obtain a Fe-NC precursor mixture;

[0023] Step (8), calcining the mixture obtained in step (7) in a tubular furnace to obtain a finished Fe-NC catalyst.

[0024] 2. The method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to Project 1 is characterized in that the soluble iron salt is selected from one or more of FeCl3·6H2O, Fe(NO3)3·9H2O, and Fe2(SO4)3·9H2O.

[0025] 3. The method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to Project 1 is characterized in that the soluble zinc salt is selected from one or more of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O, ZnCl2·H2O, and Zn(OH)2.

[0026] 4. The method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to Project 1 is characterized in that the type of imidazole substance is selected from one or more of 2-methylimidazole, benzimidazole, and purine.

[0027] 5. The method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to item 1, characterized in that the carbon nanomaterial is one or more of carbon nanotubes, activated carbon, graphene oxide, and reduced graphene oxide.

[0028] 6. The method for preparing the ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to Project 1 is characterized in that the volume ratio of the soluble iron salt aqueous solution, the soluble zinc salt aqueous solution and the imidazole substance aqueous solution is 1:0.9~1.2:1~1.2.

[0029] 7. A ZIF-L-derived multi-dimensional cross-linked Fe-NC catalyst containing oxygen vacancies, which is prepared by the preparation method according to items 1 to 6.

[0030] 8. A method for preparing an Al-air battery, comprising the following steps:

[0031] Step (1): preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies by the preparation method according to any one of items 1 to 6;

[0032] Step (2): stirring the binder PTFE emulsion and anhydrous ethanol in a volume ratio of 1:250 to form a suspension;

[0033] Step (3): relative to 1 part by mass of the binder PTFE emulsion described in step (2), weighing 0.5 to 1.5 parts by mass of the Fe-NC catalyst and 0.15 to 0.3 parts by mass of carbon black;

[0034] Step (4): uniformly mixing the Fe-NC catalyst and carbon black in step (3), adding the mixture to the suspension in step (2) and stirring;

[0035] Step (5): separating the mixture stirred in step (4) to obtain a solid-phase catalyst mixture;

[0036] Step (6): coating the solid-phase catalyst mixture obtained in step (5) on both sides of the nickel foam to form a catalyst layer, and stacking a hydrophobic air-permeable layer on the catalyst layer on one side, and then pressing to form an air electrode precursor;

[0037] Step (7): placing the air electrode precursor obtained in step (6) in a vacuum drying oven for drying to obtain an air electrode;

[0038] Step (8): The air electrode obtained in step (7) is used as a cathode, a pure aluminum plate is used as an anode, and an alkaline electrolyte is added to form an Al-air battery.

[0039] 9. The preparation method according to item 8, characterized in that the nickel foam of step (6) is sequentially treated with 0.1 mol·L -1 The hydrochloric acid aqueous solution, acetone and distilled water were each ultrasonically treated for 10 to 30 minutes.

[0040] 10. An Al-air battery prepared by the preparation method of item 8.

[0041] Effects of the Invention

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention provides a method for preparing the multidimensional cross-linked Fe-NC electrocatalyst containing oxygen vacancies by using ZIF-L as a precursor and co-pyrolyzing it with Fe(NO3)3·9H2O and carbon nanomaterials. The catalyst has good ORR electrochemical performance, specifically exhibiting a higher half-wave potential and current density.

[0044] Secondly, the multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies derived from the ZIF-L exhibits tunable oxygen vacancy concentration and high Al-air battery performance.

[0045] Finally, the preparation method of the present invention has the advantages of abundant raw material sources and low cost, simple preparation process and easy industrial development. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a process flow chart of the Al-air battery of the present invention.

[0047] Figure 2 These are scanning electron microscope (SEM) images of the multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies derived from ZIF-L prepared by the present invention, wherein (a) is the SEM image of Comparative Example 1; (b) and (c) are SEM images of Example 1 at different scales; and (d) is the SEM image of Example 2.

[0048] Figure 3 Figure 1 is a transmission electron microscope (TEM) image of Example 1 of the multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies derived from ZIF-L prepared by the present invention, wherein (a) is the overall TEM image of Example 1; (b) and (c) are local enlarged images of (a); (d) is a selected area electron diffraction image of Example 1; (e) and (f) are local enlarged images of (b); (g) is a local enlarged image of (c); (h) and (i) are high-angle annular dark field models of HRTEM of Example 1.

[0049] Figure 4 1 and 2 are X-ray diffraction (XRD) patterns and specific surface area and pore size distribution (BET) patterns of Examples 1 and 2 and Comparative Example 1. (a) is an XRD pattern; (b) is a BET pattern.

[0050] Figure 5 1 and 2 are cyclic voltammograms (CV) and linear sweep voltammograms (LSV) of Examples 1 and 2 and Comparative Example 1, wherein (a) is a cyclic voltammogram; (b) is a linear sweep voltammogram.

[0051] Figure 6 The X-ray photoelectron spectra (XPS) of Example 1 and Examples 3 to 5 are shown in Figure 1. (a) is an O1s high-resolution spectrum, and (b) is an Fe 2p high-resolution spectrum.

[0052] Figure 7 The cyclic voltammograms (CV) and linear sweep voltammograms (LSV) of Example 1 and Examples 3 to 5, as well as the half-wave potential and oxygen vacancy trend diagrams of the key parameters of the electrochemical performance of Example 1 and Examples 3 to 5, are shown in FIG. 1 , wherein (a) is the cyclic voltammogram; (b) is the linear sweep voltammogram; and (c) is the half-wave potential and oxygen vacancy trend diagram of the key parameters of the electrochemical performance.

[0053] Figure 8These are the polarization curves and power curves obtained from the Al-air battery assembled with Pt / C catalyst in Example 1. DETAILED DESCRIPTION

[0054] Unlike well-established 3D ZIFs (e.g., ZIF-67, ZIF-8), 2D leaf-shaped ZIF-Ls (ZIF-Ls) possess large cavities within their crystal layers, facilitating gas capture and adsorption. Furthermore, the abundant polar groups within the layered 2D ZIF-Ls enhance polarization at metal sites, making them more accessible for adsorption. High-temperature calcination facilitates the release of metal nodes with lower boiling points from the ZIF-L crystals, facilitating the exchange of metal cations, forming oxygen vacancies, and CN materials. Furthermore, the incorporation of advanced nanocarbon materials, such as carbon nanotubes (CNTs), activated carbon, graphene oxide (GO), and reduced graphene oxide (rGO), can mitigate the aggregation of metal active centers and enhance catalytic activity. Therefore, the introduction of additional nanocarbon materials into ZIF-L-based catalysts can increase the catalyst's specific surface area, improve the dispersion of catalytically active particles, mitigate the aggregation of active particles, and enhance the utilization of active sites. Among various carbon nanomaterials, carbon nanotubes are particularly preferred because they have good one-dimensional tubular structure and structural stability, can also serve as nanoreactors, and are generally used to synthesize multidimensional structures from interconnected nanoparticles.

[0055] Therefore, the multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies prepared using leaf-like zeolite imidazolate framework (ZIF-L) as the metal framework organic precursor is a new positive electrode catalytic material for Al-air batteries and has research and development prospects.

[0056] The present invention adopts imidazole substances such as 2-methylimidazole, benzimidazole, purine, etc. as nitrogen source and adds soluble zinc salts such as Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O, ZnCl2·H2O, Zn(OH)2, etc., and dissolves them in water to form Zn 2+Linked with deprotonated imidazoles, they form a 2D leaf-like ZIF-L structure. Due to its large surface area and abundant surface active sites, ZIF-L with a 2D leaf-like ZIF structure is a suitable self-sacrificing precursor for the preparation of Fe-NC catalytic materials. By introducing Fe ions through high-temperature co-pyrolysis with soluble iron salts such as Fe(NO₃)₃·9H₂O, the ZIF-L can release the metal-centered Zn ions, which can then coordinate with the Fe ions to form Fe-NC catalysts rich in oxygen vacancies. Secondly, the introduction of carbon nanomaterials such as carbon nanotubes, activated carbon, graphene oxide, and reduced graphene oxide as catalysts can effectively increase the specific surface area of ​​the catalyst and alleviate the aggregation of metal centers. The construction of a multidimensional cross-linked structure by reacting with carbon nanomaterials can effectively enhance the catalyst's proton-electron transfer capacity and increase the collision probability of reaction intermediates contacting the catalyst's active centers, thereby improving the catalyst's electrochemical performance and reaction kinetics.

[0057] On the one hand, the Zn nodes in the 2D leaf-shaped ZIF-L have a lower boiling point, allowing them to form CN materials upon high-temperature calcination. In CN materials, since nitrogen has a greater electronegativity than carbon, this carbon-nitrogen bond is polarized, resulting in positive charges on the nearby carbon atoms doped with N, which is more favorable for O adsorption. Secondly, the doping of Fe ions reduces the electron cloud density around them, facilitating better interaction between Fe ions and N and C, promoting the redox coupling required for the ORR. Furthermore, due to the different radii of the metal (Fe, Zn) ions, the surrounding atoms cannot maintain their original equilibrium, causing oxygen in the lattice to escape as electrically neutral oxygen molecules, simultaneously forming positively charged oxygen vacancies in the crystal. The formation of oxygen vacancies changes the electron cloud density around the metal (Fe) center, creating unsaturated sites and promoting the migration of Fe ions to higher or lower valence states. Therefore, the replacement of metal (Fe, Zn) cations during calcination forms oxygen vacancies with electrochemical activity for the ORR, increasing the number of adsorption sites on the catalyst and enhancing the density of active sites, thereby promoting the rate of the oxygen reduction reaction. Applying this type of oxygen vacancy-rich Fe-NC catalyst to the air electrode catalyst layer of Al-air batteries can improve the power density and power generation efficiency of Al-air batteries. Furthermore, by varying the concentration of soluble zinc salts to control the oxygen vacancy concentration, the effect of Fe-NC catalysts with different oxygen vacancy concentrations on the ORR electrochemical performance was explored.

[0058] On the other hand, by introducing advanced carbon nanomaterials (such as CNTs, C, GO, rGO) as carbon nanomaterials in the catalyst, it can be used to construct a multidimensional cross-linked structure and establish a conductive highway. The multidimensional cross-linked structure can effectively increase the specific surface area of ​​the catalyst and provide a higher pore structure, thereby enhancing the proton-electron transport capacity of the oxygen molecule reaction site (solid-liquid-gas coexistence) and the collision probability of the active center. Secondly, the multidimensional cross-linked structure Fe-NC catalyst has the characteristics of Fe being polymorphic and multivalent. Polymorphic and multivalent Fe-based catalysts can help to adsorb O2, obtain more electrons, and thus enhance the ORR electrocatalytic activity of the catalyst. At the same time, Fe 3+ / Fe 2+ The active redox behavior of cations in the triangular structure can effectively improve the conductivity of the catalyst, improve electrolyte diffusion and faster interfacial charge transfer, and activate electron holes to provide more active sites, thereby exhibiting higher ORR electrocatalytic activity.

[0059] Based on this, a multi-dimensional cross-linked Fe-NC catalyst-based air electrode containing oxygen vacancies derived from ZIF-L exhibits high electrochemical performance in the field of Al-air batteries. The preparation method is simple, green, environmentally friendly, and low-cost, which is conducive to the large-scale application of Fe-NC negative electrode materials in the Al-air battery industry. The present invention mainly focuses on the preparation of oxygen reduction air electrode catalysts. The purpose is to develop an economical and practical Fe-NC-based air electrode with excellent electrochemical performance, thereby reducing the cost of Al-air batteries. The present invention has certain reference value for the industrial development of Al-air batteries.

[0060] The present invention prepares a multi-dimensional cross-linked Fe-NC catalyst containing oxygen vacancies derived from ZIF-L by a simple pyrolysis method, and uses the catalyst in the catalyst layer of the air electrode and assembles it into an Al-air battery, such as Figure 1 shown.

[0061] The preparation method of the ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies of the present invention comprises the following steps:

[0062] Step (1): Prepare 0.8-1.2 mol·L -1 Imidazole aqueous solution and 0.1~1mol·L -1 Soluble zinc salt aqueous solution and 0.05~0.1mol·L -1 Aqueous solution of soluble iron salts.

[0063] The volume ratio of the soluble iron salt aqueous solution, the soluble zinc salt aqueous solution and the imidazole substance aqueous solution is 1:0.9-1.2:1-1.2, more preferably 1:1:1. Maintaining the volume ratio of the three aqueous solutions in this range is more conducive to sufficient coordination of free metal ions in the solution and avoiding lattice transformation of the crystal.

[0064] The soluble iron salt is selected from one or more of FeCl3·6H2O, Fe(NO3)3·9H2O, and Fe2(SO4)3·9H2O, preferably Fe(NO3)3·9H2O.

[0065] The soluble zinc salt is selected from one or more of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O, ZnCl2·H2O, and Zn(OH)2. Zn(NO3)2·6H2O is preferred.

[0066] The imidazole substance is selected from one or more of 2-methylimidazole, benzimidazole, and purine, preferably 2-methylimidazole.

[0067] Step (2): The aqueous solution of the imidazole substance and the aqueous solution of the soluble zinc salt in the above step (1) are mixed and stirred for 12 hours to 24 hours to synthesize 2D ZIF-L leaf-like crystals. The stirring time is kept within this range, which is beneficial to providing a larger specific surface area and pore structure for the synthesis of the Fe-NC catalyst, making it easier for the catalyst to obtain accessible active sites, and more preferably 16 hours to 20 hours.

[0068] Step (3): Weighing a carbon nanomaterial at a ratio of 80 to 110 g relative to 1 mol of Fe ions in step (1), and then adding the carbon nanomaterial to a mixed solvent consisting of acetone, ethanol and distilled water in a volume ratio of 1:1:1 and ultrasonically treating it for 0.1 h to 1 h to form a uniform carbon nanomaterial suspension.

[0069] Keeping the ultrasonic treatment time within the range of 0.1h to 1h is more conducive to fully pretreating the carbon nanomaterial while saving time costs and cleaning pollutants and oil layers on the surface of the carbon nanomaterial. The more preferred ultrasonic treatment time is 20 to 40min to obtain better results.

[0070] Step (4) centrifuges the carbon nanomaterial suspension obtained in step (3) and then vacuum-dries it to obtain a pretreated carbon nanomaterial, thereby eliminating the interference of the cleaning solution solvent in step (3).

[0071] The carbon nanomaterial is one or more of carbon nanotubes, activated carbon, graphene oxide, and reduced graphene oxide, preferably carbon nanotubes.

[0072] Step (5): The soluble iron salt aqueous solution in step (1) and the pretreated carbon nanomaterial in step (4) are mixed and stirred for 0.5 h to 1.5 h to obtain a mixed solution, which is recorded as: Fe-C mixed solution.

[0073] In step (5), the stirring time is not particularly limited and is preferably 0.5h to 1.5h, more preferably 0.5h to 1h, so as to be more conducive to the full attachment of Fe to the carbon nanomaterial, so as to subsequently form a multi-dimensional cross-linked structure of Fe / Fe2O3 nanoparticles wrapped in carbon nanomaterials, which is more conducive to providing a conductive highway for the catalyst and accelerating the electron-proton transfer rate.

[0074] Step (6): The ZIF-L leaf-shaped crystals obtained in step (2) are mixed with the Fe-C mixture in step (5) and stirred for 24 to 85 hours, preferably 48 to 72 hours. This is done while taking time into consideration and further facilitating sufficient competitive reactions between metal ions, facilitating cation exchange and the subsequent formation of Fe / Fe2O3 / Fe-N composite particles with oxygen vacancies.

[0075] In step (6), the aqueous solution of the imidazole substance and the aqueous solution of the soluble zinc salt in step (2) are mixed and stirred, and then mixed with the aqueous solution of the soluble iron salt and the carbon nanomaterial suspension in step (5) and stirred to obtain a mixed solution. Compared with the existing technology, it is more conducive to constructing a multidimensional cross-linked structure based on the formation of active particles containing oxygen vacancies, promoting faster electron-proton transfer and transmission of the catalyst, and increasing the specific surface area of ​​the catalyst and the possibility of exposure of active sites.

[0076] Step (7): centrifuge the mixed solution after stirring in step (6) and vacuum dry it to obtain a mixture

[0077] Step (7): centrifuging the mixed solution after stirring in step (6) and vacuum drying to obtain a mixture.

[0078] The centrifugal speed is not particularly limited and is preferably 3000 to 5000 r·min -1 , more preferably 3500~4500r·min -1 The centrifugation time is not particularly limited and is preferably 4 to 10 minutes, more preferably 5 to 7 minutes; the drying time is not particularly limited and is preferably 12 to 32 hours, more preferably 18 to 24 hours; the drying temperature is not particularly limited and is preferably 60 to 70°C. This is more conducive to sufficient drying of the catalyst and facilitates subsequent calcination.

[0079] Step (8), calcining the mixture obtained in the above step (7) in a tubular furnace to obtain a Fe-NC catalyst.

[0080] The calcination temperature is not particularly limited, preferably 700 to 1000°C, more preferably 800 to 900°C. The calcination time is not particularly limited, preferably 2 to 5 hours, more preferably 3 to 4 hours. The heating rate is 1 to 10°C min -1 , preferably 4 to 6 ° C·min -1 . Calcination in a temperature range greater than 700°C is more conducive to the ZIF-L crystal not undergoing lattice transformation and forming the required CN material. Calcination in a temperature range of around 900°C is more conducive to the coordinated Zn ions being more easily released and further coordinated with Fe ions, thereby forming Fe / Fe2O3 / Fe-N composite particles with oxygen vacancies, creating more active sites for the catalyst, changing the electron cloud density around the metal center, and promoting the adsorption and reaction of oxygen-containing intermediate molecules. Secondly, in this temperature range, the carbon nanomaterials attached with Fe ions will react fully to form a multi-dimensional cross-linked structure of carbon nanomaterials wrapped around Fe / Fe2O3 nanoparticles, improving the conductivity of the catalyst, providing the catalyst with a higher specific surface area and pore structure, and increasing the accessibility of the catalyst's active sites. Calcination in a temperature range greater than 1000°C is prone to the aggregation of metal sites, which is not conducive to the exposure of active sites, thereby reducing the electrochemical activity of the catalyst.

[0081] The preparation method of the Al-air battery of the present invention comprises the following steps:

[0082] Step (1): Prepare a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies by the above method.

[0083] Step (2): The binder PTFE emulsion and anhydrous ethanol are stirred evenly in a volume ratio of 1:250 to form a suspension.

[0084] Step (3): relative to 1 part by mass of the binder PTFE emulsion described in step (2), weigh 0.5 to 1.5 parts by mass of the Fe-NC catalyst and 0.15 to 0.3 parts by mass of carbon black.

[0085] Step (4): The Fe-NC catalyst, carbon black, and suspension from step (2) are mixed and stirred for 1 to 3 hours. Preferably, the Fe-NC catalyst and carbon black from step (3) are mixed evenly before being mixed with the suspension from step (2). This is more conducive to uniform mixing of the Fe-NC catalyst, carbon black, and binder PTFE emulsion, so that a catalyst layer with the Fe-NC catalyst, carbon black, and binder PTFE emulsion evenly distributed is subsequently pressed.

[0086] Step (5): separating the mixture stirred in step (4) to obtain a solid phase catalyst mixture.

[0087] Step (6): coating the solid-phase catalyst mixture obtained in step (5) on both sides of the nickel foam to form a catalyst layer, and stacking a hydrophobic air-permeable layer on the catalyst layer on one side, and then pressing to form an air electrode precursor.

[0088] The hydrophobic breathable layer is not particularly limited and may be any hydrophobic breathable layer known in the art, preferably a PTFE membrane.

[0089] The solid phase mixture obtained in step (5) can be evenly coated on both sides of the nickel foam, which can more advantageously increase the reaction site of the ORR reaction occurring at the cathode air electrode of the Al-air battery and improve the discharge capacity of the Al-air battery.

[0090] Preferably, the nickel foam of step (6) is sequentially treated with 0.1 mol·L -1 The hydrochloric acid aqueous solution, acetone, and distilled water are each ultrasonically treated for 10 to 30 minutes, more preferably 15 to 25 minutes. Limiting the time to this range is more conducive to achieving a better effect of removing oxides and stains on the surface of the nickel foam and the solvent residue after each treatment while taking into account time costs.

[0091] There is no particular restriction on the pressing time and pressure of the air electrode, which are commonly used in the art, but preferably the time is 30 to 40 minutes and the pressure is 0.3 to 0.6 MPa, which is more conducive to forming an air electrode with uniform distribution and moderate density. When the pressure is less than 0.3 MPa, the solid phase mixture material in step (5) is coated on the pretreated nickel foam and cannot be well bonded to the hydrophobic breathable layer, and leakage may occur, and the areas with poor bonding may have problems such as incomplete ORR reaction and slow reaction rate. When the pressure is greater than 0.6 MPa, the solid phase mixture material in step (5) is coated on the nickel foam and has too high bonding ability with the hydrophobic breathable layer, and cannot provide a good area for solid-liquid-gas coexistence, which is not conducive to the ORR reaction occurring at the cathode air electrode of the Al-air battery.

[0092] The thickness of the air electrode is not particularly limited, and may be, for example, 0.5 to 1.5 mm, 25 to 30 mm in length, and 25 to 30 mm in width.

[0093] Step (7): The air electrode precursor obtained in step (6) is placed in a vacuum drying oven for drying. The vacuum drying temperature and time are not particularly limited, but preferably the drying temperature is 40-60°C and the drying time is 2-3 hours. A drying temperature below 40°C may result in excessively long drying times, while a drying temperature above 60°C may easily cause agglomeration of the material.

[0094] Step (8): The air electrode obtained in the above step (7) is used as the cathode, the pure aluminum plate is used as the anode, and alkaline electrolyte is added to form an Al-air battery.

[0095] The pure aluminum plate is an aluminum plate known in the prior art, for example, a pure aluminum plate with Al≥99.99%, which can provide a sufficient amount of Al ions for the Al-air battery reaction and promote the reaction.

[0096] In step (9), the alkaline electrolyte is a KOH solution. Battery discharge products in a salt solution will form a gel, increasing battery resistance and reducing battery efficiency. This will not occur with an alkaline KOH solution. In addition, an alkaline KOH solution is more conducive to corroding the aluminum oxide layer on the surface of the metal aluminum plate, and has a higher specific energy density and specific power density, thereby outputting a larger current density and power.

[0097] The concentration of the alkaline electrolyte is not particularly limited, but is preferably 4 to 10 mol·L -1 .

[0098] The technical solution of the present invention is further described below through specific embodiments.

[0099] Unless otherwise specified, the raw materials used in the examples of the present invention are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art. For example, Zn(NO3)2·6H2O, Fe(NO3)3·9H2O, and 2-methylimidazole were all analytically pure standards purchased from Shanghai Aladdin Reagent Co., Ltd.; acetone and anhydrous ethanol were analytically pure standards purchased from Fuchen (Tianjin) Chemical Reagent Co., Ltd.; carbon nanotubes were purchased from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences; and activated carbon was purchased from Kuraray, Japan.

[0100] Al-air battery air electrode material, the preparation method is as follows:

[0101] Example 1:

[0102] Prepare 50mL of 0.08mol·L -1 Fe(NO3)3·9H2O aqueous solution, 0.2mol·L -1 Zn(NO3)2·6H2O aqueous solution and 0.9mol·L -1 40 mL of 2-methylimidazole aqueous solution and Zn(NO3)2·6H2O aqueous solution were measured and stirred for 16 h to form 2D ZIF-L leaf-like crystals. 300 mg of carbon nanotubes were weighed and added to a cleaning solution consisting of acetone, ethanol and distilled water (the volume ratio of acetone, ethanol and distilled water was 1:1:1) and ultrasonically treated for 0.5 h to form a uniformly dispersed carbon nanotube suspension. The carbon nanotube suspension was stirred at 4500 r·min -1The pretreated carbon nanotubes were centrifuged at 4500 r / min for 5 minutes. The Fe(NO3)3·9H2O aqueous solution was then mixed with the pretreated carbon nanotubes and stirred for 0.5 h to obtain a mixed solution of carbon nanotubes with Fe ions attached. The obtained ZIF-L crystals were mixed with the mixed solution of carbon nanotubes with Fe ions attached and stirred for 72 h. -1 After centrifugation at 500 nm for 5 minutes, the mixture was vacuum dried at 70°C for 24 hours to obtain a mixture. The dried mixture was then placed in a tube furnace and heated to 900°C at a heating rate of 5°C / min and calcined for 3 hours to obtain an Fe-NC catalyst, which was designated as Fe-N-CNTs-900-0.2.

[0103] 40 μL of binder PTFE emulsion (polytetrafluoroethylene PTFE emulsion, solid content: 60%) and anhydrous ethanol were measured and stirred in a volume ratio of 1:250 to form a PTFE suspension; 60 mg of Fe-N-CNTs-900-0.2 and 10 mg of carbon black were weighed; the Fe-N-CNTs-900-0.2 catalyst and carbon black were mixed evenly and added to the PTFE suspension and stirred for 2 h; then the mixture was separated to obtain a solid-phase catalyst mixture; 20 mL of 0.1 mol·L -1 The nickel foam was sequentially treated with 0.1 mol·L -1 The hydrochloric acid solution, acetone, and distilled water were each ultrasonically treated for 20 minutes. The solid-phase catalyst mixture was then coated on both sides of the nickel foam to form a catalyst layer. A PTFE membrane was then laminated on one side of the catalyst layer and pressed to form an air electrode. The resulting air electrode was dried in a vacuum drying oven at 60°C for 2 hours. The resulting air electrode served as the cathode, a pure aluminum plate as the anode, and 10 mol·L -1 The KOH alkaline electrolyte constitutes an Al-air battery, which is recorded as Al-air battery-1.

[0104] The half-wave potential of Fe-N-CNTs-900-0.2 obtained by the above method is: 0.882V vs. RHE. The battery performance of Al-air battery-1: the maximum power density is: 45.34mW·cm -2 The maximum power density is at a current density of 55.43 mA·cm -2 .

[0105] Example 2:

[0106] The Fe-NC catalyst was obtained in the same manner as in Example 1, except that the carbon nanotubes were replaced with activated carbon. This was designated Fe-NC-900. An Al-air battery assembled with the Fe-NC-900 catalyst as the air electrode catalyst layer was designated Al-air battery-2.

[0107] The ORR electrochemical activity of Fe-NC-900 is relatively high, as shown in the following: the half-wave potential of Fe-NC-900 is 0.871 V vs. RHE.

[0108] Example 3:

[0109] In addition to changing the concentration of Zn(NO3)2·6H2O aqueous solution to 0.15 mol·L -1 In addition, Fe-NC catalyst was obtained in the same manner as in Example 1 and recorded as Fe-N-CNTs-900-0.15. Al-air battery assembled with Fe-N-CNTs-900-0.15 catalyst was recorded as Al-air battery-3.

[0110] The ORR electrochemical activity of Fe-N-CNTs-900-0.15 is relatively high, as shown in the following: the half-wave potential of Fe-NC-900 is 0.791 V vs. RHE.

[0111] Example 4:

[0112] In addition to changing the concentration of Zn(NO3)2·6H2O aqueous solution to 0.6 mol·L -1 In addition, Fe-NC catalyst was obtained in the same manner as in Example 1 and recorded as Fe-N-CNTs-900-0.6. Al-air battery assembled with Fe-N-CNTs-900-0.6 catalyst was recorded as Al-air battery-3.

[0113] The ORR electrochemical activity of Fe-N-CNTs-900-0.6 is relatively high, as shown in the following: the half-wave potential of Fe-NC-900 is 0.751 V vs. RHE.

[0114] Example 5:

[0115] In addition to changing the concentration of Zn(NO3)2·6H2O aqueous solution to 1 mol·L -1 In addition, Fe-NC catalyst was obtained in the same manner as in Example 1 and was designated as Fe-N-CNTs-900-1. An Al-air battery assembled with the Fe-N-CNTs-900-1 catalyst was designated as Al-air battery-5.

[0116] The ORR electrochemical activity of Fe-N-CNTs-900-1 is high, as shown in the following: the half-wave potential of Fe-NC-900 is 0.731 V vs. RHE.

[0117] Comparative Example 1:

[0118] Prepare 50mL of 0.08mol·L -1 Fe(NO3)3·9H2O aqueous solution, 0.2mol·L -1 Zn(NO3)2·6H2O aqueous solution and 0.9mol·L -1 2-methylimidazole aqueous solution. Separately measure 40 mL of 2-methylimidazole aqueous solution and Zn(NO3)2·6H2O aqueous solution, and mix and stir for 16 h to form 2D ZIF-L leaf-like crystals. In addition, measure 40 mL of 0.08 mol·L -1 The Fe(NO3)3·9H2O aqueous solution was added and the stirring was continued for 72h. The stirred mixed solution was heated at 4500r·min -1 After centrifugation at 5000rpm for 5min, the mixture was dried under vacuum at 70℃ for 24h to obtain a mixture. The dried mixture was then placed in a tube furnace and heated at 5℃·min -1 The temperature was raised to 900 °C at a heating rate of 10000 °C and calcined for 3 h to obtain a Fe-NC catalyst, which was recorded as Fe-N-900.

[0119] The half-wave potential of Fe-N-900 is: 0.863V vs.RHE.

[0120] The morphology of the ZIF-L derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies was analyzed, and its SEM and TEM images showed that Figure 2 、 Figure 3 According to the SEM and TEM analysis results, compared with the Fe-N-900 catalyst synthesized without carbon nanomaterials (Comparative Example 1), after adding carbon nanomaterials (Example 1, Example 2), the crystal particles containing oxygen vacancies in the Fe-NC catalyst (the circled part) can be more exposed, as shown in Figure 2. Figure 2 (bd) This result shows that the carbon nanomaterials with advanced carbon nanomaterials as catalysts can improve the exposure of the active centers of the catalyst, improve the problem of metal crystal aggregation, and improve the dispersion of crystal particles. Secondly, the local enlarged SEM image of the carbon nanomaterials with CNTs as the carbon nanomaterials (Example 1) (as shown in FIG Figure 2 (c) shows that the catalyst is composed of a cross-linked structure of crystalline particles containing oxygen vacancies and CNTs encapsulating Fe nanoparticles. This result is also confirmed by TEM results, such as Figure 3 (ac) shown. Figure 3 (b) is a crystal particle containing oxygen vacancies, Figure 3 (c) is a CNT wrapped with Fe nanoparticles. A disordered edge layer caused by oxygen vacancies was found on the surface of the crystal particles containing oxygen vacancies ( Figure 3 (e) black dotted line), flare edge layer ( Figure 3 (hi) Dashed line diagram) and the Fe atoms that may overflow at the oxygen vacancy ( Figure 3 (f) Circled part). Figure 3 (g) shows that the Fe valence states of Fe-containing nanoparticles encapsulated in CNTs are 0 and 3, and exist as Fe / Fe2O3.

[0121] According to the SAED of Example 1 ( Figure 3 (d) shows that the Fe in the Fe-NC catalyst mainly exists in the form of Fe, Fe2O3, and Fe-N. This result is consistent with the XRD results (such as Figure 4 (a) is consistent. BET results show that after adding carbon nanomaterials (Example 1, Example 2), the specific surface area of ​​Fe-NC catalyst increases. The specific surface area of ​​Comparative Example 1 is 61.68 mg g -1 The specific surface area of ​​Example 1 is 236.41 mg·g -1 The specific surface area of ​​Example 2 is 108.78 mg·g -1 .

[0122] The electrochemical results of Comparative Example 1 and Examples 1 and 2 (such as Figure 5 The results show that the addition of carbon nanomaterials (Examples 1 and 2) enhances the ORR electrochemical performance of the Fe-NC catalyst. Specifically, the half-wave potential of Comparative Example 1 is 0.863 V vs. RHE; the half-wave potential of Example 1 is 0.882 V vs. RHE; and the half-wave potential of Example 2 is 0.871 V vs. RHE.

[0123] These results indicate that the construction of a multidimensional cross-linked structure can effectively improve the reaction kinetics and proton-electron transfer capacity of the catalyst. Therefore, the multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies has better electrochemical performance.

[0124] To further explore the effect of oxygen vacancy concentration on the electrochemical performance of the catalyst ORR, we compared Example 1 and Examples 3 to 5. XPS results (such as Figure 6 The results show that the presence of oxygen vacancies leads to changes in the binding energy of atoms around the oxygen vacancies, which verifies the existence of oxygen vacancies. The concentration trend of oxygen vacancies is determined based on the proportion of oxygen vacancies in the catalyst oxygen atoms and the offset of Fe 2p binding energy, as shown in Figure 2. Figure 7(c) Shown by the black line.

[0125] The ORR electrochemical performance of Examples 1 and 3 to 5 was tested, and the trend of the key parameter, half-wave potential, changing with the oxygen vacancy concentration was obtained, as shown in FIG. Figure 7 (c) As shown. The results show that lower oxygen vacancy concentrations exhibit higher electrochemical performance. Specifically, in Example 1, the oxygen vacancy concentration is 30.1, and the half-wave potential is 0.882V vs. RHE; in Example 3, the oxygen vacancy concentration is 33.6, and the half-wave potential is 0.791V vs. RHE; in Example 4, the oxygen vacancy concentration is 35.3, and the half-wave potential is 0.751V vs. RHE; in Example 5, the oxygen vacancy concentration is 36.9, and the half-wave potential is 0.731V vs. RHE. This is because a higher concentration of oxygen vacancies causes a higher degree of unsaturation, which makes the adsorption capacity of the reaction intermediates too strong and is not conducive to their desorption. This shows that the oxygen vacancy concentration of the multi-dimensional cross-linked structure Fe-NC catalyst has a greater influence on the electrochemical performance of the catalyst. A lower oxygen vacancy concentration provides the catalyst with a suitable degree of unsaturation, which is beneficial to promoting the ORR reaction of the catalyst.

[0126] The performance test of Al-air battery was carried out on Example 1 and Pt / C catalyst. Figure 8 The results show that Example 1 has higher discharge current density and power density than Pt / C catalyst. Specifically, the maximum power density of Fe-N-CNTs-900-0.2 is 45.34 mW·cm -2 The maximum power density is at a current density of 55.43 mA·cm -2 The maximum power density of the Pt / C catalyst is 15.43 mW·cm -2 The maximum power density is at a current density of 17.46 mA·cm -2 This indicates that the multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies has lower cost and higher performance, and is expected to replace Pt / C catalyst in industrial application.

[0127] In summary, the ZIF-L-derived Fe-NC catalyst containing oxygen vacancies prepared by the present invention exhibits excellent ORR electrochemical performance and Al-air battery performance. The preparation method described in the present invention has readily available raw materials, low equipment cost, simple operation, short time consumption, and is suitable for promotion of industrial production. The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. The present invention is not limited to the above embodiments. The knowledge described in the above embodiments and the description illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and such changes and improvements all fall within the scope of the invention to be protected. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies, characterized in that The steps include: Step (1): Prepare 0.8-1.2 mol·L -1 Imidazole aqueous solution and 0.1~1mol·L -1 Soluble zinc salt aqueous solution and 0.05~0.1mol·L -1 Aqueous solution of soluble iron salts; Step (2): mixing the imidazole aqueous solution and the soluble zinc salt aqueous solution in step (1) and stirring for 12 to 24 hours to synthesize 2D ZIF-L leaf-like crystals; Step (3): weighing a carbon nanomaterial at a ratio of 80 to 110 g relative to 1 mol of Fe ions, and then adding the carbon nanomaterial to a mixed solvent consisting of acetone, ethanol, and distilled water in a volume ratio of 1:1:1, and ultrasonically treating the mixture for 0.1 h to 1 h to form a uniform carbon nanomaterial suspension; Step (4), centrifuging the carbon nanomaterial suspension obtained in step (3) and vacuum drying to obtain a pretreated carbon nanomaterial; Step (5): mixing the soluble iron salt aqueous solution with the pretreated carbon nanomaterial in step (4) and stirring for 0.5 h to 1.5 h to obtain an Fe-C mixed solution; Step (6): mixing the ZIF-L leaf-shaped crystals obtained in step (2) with the Fe-C mixed solution in step (5) and stirring for 24 to 85 hours; Step (7): centrifuging the mixed solution stirred in step (6) and then vacuum drying to obtain a Fe-NC precursor mixture; Step (8), calcining the Fe-NC precursor mixture obtained in step (7) in a tubular furnace to obtain a Fe-NC catalyst, wherein the calcination temperature is greater than 700°C and less than 1000°C.

2. The method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to claim 1, characterized in that The soluble iron salt is selected from one or more of FeCl3·6H2O, Fe(NO3)3·9H2O, and Fe2(SO4)3·9H2O.

3. The method for preparing the ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to claim 1, characterized in that The soluble zinc salt is selected from one or more of Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O, ZnCl2·H2O, and Zn(OH)2.

4. The method for preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to claim 1, characterized in that The imidazole substances are selected from one or more of 2-methylimidazole, benzimidazole and purine.

5. The method for preparing the ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to claim 1, characterized in that The carbon nanomaterial is one or more of carbon nanotubes, activated carbon, graphene oxide, and reduced graphene oxide.

6. The method for preparing the ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies according to claim 1, characterized in that The volume ratio of the soluble iron salt aqueous solution, the soluble zinc salt aqueous solution and the imidazole substance aqueous solution is 1:0.9-1.2:1-1.

2.

7. A ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies, prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing an Al-air battery, characterized in that: The following steps are involved: Step (1): preparing a ZIF-L-derived multidimensional cross-linked Fe-NC catalyst containing oxygen vacancies by the preparation method according to any one of claims 1 to 6; Step (2): mixing the binder PTFE emulsion and anhydrous ethanol in a volume ratio of 1:250 to form a PTFE suspension; Step (3): relative to 1 part by mass of the binder PTFE emulsion described in step (2), weighing 0.5 to 1.5 parts by mass of the Fe-NC catalyst and 0.15 to 0.3 parts by mass of carbon black; Step (4): uniformly mixing the Fe-NC catalyst and the carbon black in step (3), adding the mixture to the PTFE suspension in step (2) and stirring; Step (5): separating the catalyst mixture material stirred in step (4) to obtain a solid-phase catalyst mixture material; Step (6): coating the solid-phase catalyst mixture obtained in step (5) on both sides of the nickel foam to form a catalyst layer, and stacking a hydrophobic air-permeable layer on the catalyst layer on one side, and then pressing to form an air electrode precursor; Step (7): placing the air electrode precursor obtained in step (6) in a vacuum drying oven for drying to obtain an air electrode; Step (8): The air electrode obtained in step (7) is used as a cathode, a pure aluminum plate is used as an anode, and an alkaline electrolyte is added to form an Al-air battery.

9. The preparation method according to claim 8, characterized in that The nickel foam of step (6) was sequentially treated with 0.1 mol·L -1 The hydrochloric acid aqueous solution, acetone and distilled water were each ultrasonically treated for 10 to 30 minutes. 10 . An Al-air battery prepared by the preparation method according to claim 8 .

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