Preparation method and application of MOF (Metal Organic Framework) derived carbon catalyst for regulating and controlling oxygen reduction catalytic performance based on surface strain

Abstract

The invention discloses a preparation method and application of an MOF (Metal Organic Framework) derived carbon catalyst for regulating and controlling oxygen reduction catalytic performance based on surface strain. The method comprises the following steps: firstly, constructing a cubic MOF core under the assistance of a cationic surface active agent template through coordination self-assembly of a cobalt ion node and an imidazole ligand; then, an MOF heterogeneous core-shell layer is constructed on the surface of the core through a zinc ion mediated epitaxial growth technology, and a double-layer cubic MOF precursor with a clear core-shell interface is formed. Through carbonization treatment at different temperatures, the core MOF generates controllable surface strain in the carbonization process, metal active site coordination and electronic structures can be adjusted, and the adsorption strength of sites to oxygen reduction intermediates is optimized. A rigid porous carbon frame formed after carbonization of an epitaxial MOF heterogeneous core-shell layer constructs a three-dimensional through mass transfer network through micro-mesoporous synergy, meanwhile, the rigid porous carbon frame and the strained core form a nanoscale space isolation area, and thermal migration of metal active sites and Ostwald curing are effectively inhibited by means of the geometric confinement effect. The activity and the stability of the catalyst are remarkably improved based on multiple synergistic effects caused by evolution of an intrinsic micro-nano structure induced by surface strain. The MOF derived carbon catalyst for regulating and controlling the oxygen reduction catalytic performance based on the surface strain, provided by the invention, is simple in preparation process and low in cost, and shows excellent performance and wide application prospect in a zinc-air battery.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen reduction electrocatalysts, and particularly relates to a preparation method and application of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain. Background Art

[0002] The oxygen reduction reaction (ORR) is a key half-reaction in a new energy conversion device, the zinc-air battery. However, its slow heterogeneous reaction kinetics severely restricts the energy conversion efficiency of the battery system. Developing ORR catalysts with both high intrinsic activity and stability has become a research hotspot in this field. Currently, although commercial platinum-based catalysts exhibit excellent catalytic performance, they face difficulties such as scarce reserves, poor durability, and high costs for large-scale applications, which fundamentally limit their industrial application in zinc-air batteries.

[0003] In recent years, metal-organic frameworks (MOFs), as periodically ordered porous crystalline materials, have attracted extensive attention in the field of electrocatalytic materials due to their structural designability, topological structure diversity (such as ZIF, MIL series), and rich M-N x active site characteristics. Based on the carbonization strategy, MOF precursors can be transformed into carbon-based catalytic materials with both three-dimensional conductive networks and nano-cluster / atomically dispersed active sites. Such MOF-derived carbon catalysts not only break through the intrinsic activity limit of traditional carbon materials but also exhibit the dual advantages of controllable precursor cost and adjustable synthesis routes, providing a potential solution for replacing commercial platinum-based catalysts. However, during the carbonization process of MOF-derived carbon catalysts, the thermal driving effect often causes metal ions to migrate to the matrix surface and agglomerate, which will lead to the shedding and loss of active sites during the electrocatalytic reaction process. In addition, as catalytic active centers, metal atoms have too strong adsorption on ORR intermediates, restricting the smooth progress of the subsequent proton-electron transfer process, thereby reducing the intrinsic activity of the catalyst. To address the above problems, it is urgent to rationally design the precursor structure to provide an additional protective layer for active sites and achieve precise regulation of the local reaction environment, thereby effectively suppressing atomic migration and agglomeration and optimizing the adsorption strength of intermediates, so as to improve the activity and stability of the catalyst and ultimately achieve the efficient preparation of non-precious metal oxygen reduction catalysts with low cost and excellent catalytic performance. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a preparation method and application of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain. This catalyst innovatively introduces a surface strain regulation mechanism to adjust the coordination and electronic structure of metal active sites, optimize the adsorption strength of oxygen reduction intermediates on the sites, and construct a three-dimensional through-mass transfer network through the synergy of micro-mesopores. With the help of the geometric confinement effect, the thermal migration and Ostwald ripening of metal active sites are effectively inhibited, and the activity and stability of the catalyst are improved. This method has a simple process and low cost, providing a new technical solution for the development of efficient and economical non-precious metal oxygen reduction catalysts.

[0005] The core concept of the present invention is to adopt a surface strain regulation strategy. First, a cubic MOF core is constructed using an imidazole ligand, a cationic surfactant, and a cobalt ion node; then, through a zinc ion-mediated epitaxial growth technique, a MOF hetero-core-shell layer is constructed on the surface of the core. After the obtained double-layer cubic MOF precursor is dried, it is heat-treated at different carbonization temperatures in an inert gas atmosphere to finally prepare a MOF-derived carbon catalyst. During the carbonization process, a controllable surface strain is generated in the cubic MOF core to adjust the coordination and electronic structure of metal active sites, thereby optimizing the adsorption strength of oxygen reduction reaction intermediates. The rigid porous carbon framework formed by the epitaxial MOF hetero-core-shell layer after carbonization constructs a three-dimensional through-mass transfer network through the synergy of micropores and mesopores, and forms a nanoscale spatial isolation region with the strained core, effectively inhibiting the thermal migration and Ostwald ripening of metal active sites with the help of the geometric confinement effect. Due to the multiple synergistic effects caused by the evolution of the intrinsic micro-nano structure induced by surface strain, the activity and stability of the catalyst are significantly improved.

[0006] To solve the above technical problems, the first aspect of the present invention provides a preparation method of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain, including the following steps:

[0007] (1) Mix and disperse an imidazole ligand, a cationic surfactant, and a cobalt salt in a solvent, react under certain conditions, filter, and vacuum dry to obtain a cubic MOF core;

[0008] (2) Mix and disperse the cubic MOF core with an imidazole ligand and a zinc salt in a solvent, react under certain conditions, filter, and vacuum dry to obtain a cubic double-layer structure MOF precursor;

[0009] (3) Carbonize the cubic double-layer structure MOF precursor in an inert atmosphere to obtain an oxygen reduction catalyst with a cubic outer layer and different strain degrees in the inner layer.

[0010] Preferably, the imidazole ligand described in steps (1) and (2) preferably includes one or more of 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, and 5-methylimidazole;

[0011] Preferably, the cationic surfactant described in step (1) includes one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and tetracosyltrimethylammonium bromide;

[0012] Preferably, the cobalt salt described in step (1) includes one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt oxalate;

[0013] Preferably, the zinc salt described in step (2) includes one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, and zinc oxalate;

[0014] Preferably, the certain conditions in step (1) are: the stirring time is 1 h, the standing time is 6 h, the stirring speed is 400 rpm, the solvent is water, and the temperature of the drying oven is set at 60 °C;

[0015] Preferably, the certain conditions in step (2) are: the stirring time is 1 h, the standing time is 6 h, the stirring speed is 400 rpm, the solvent is water, and the temperature of the drying oven is set at 60 °C;

[0016] Preferably, the temperature of carbonization in step (3) is 800 °C, the time of carbonization is 2 h, and the heating rate to the carbonization temperature is 5 °C / min.

[0017] Preferably, the mass ratio of the imidazole ligand, cationic surfactant, and cobalt salt described in step (1) is 1:0.02:0.08. The mass ratio of the cubic MOF core, nitrogen-containing functional group imidazole ligand, and zinc salt described in step (2) is 1:17.00:1.20.

[0018] The second aspect of the present invention provides a MOF-derived carbon oxygen reduction catalyst for regulating oxygen reduction catalytic performance based on surface strain synthesized by the preparation method.

[0019] The present invention also provides the application of the MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain in the cathode of a battery, wherein the battery is a zinc-air battery.

[0020] The present invention has the following advantages and beneficial effects compared with the prior art:

[0021] 1. The present invention innovatively introduces a surface strain regulation mechanism during the carbonization process. By utilizing the difference in thermal shrinkage between the inner core and the outer core-shell structure of the double-layer MOF precursor, strain is induced in the core, while the outer carbon framework is stable, thereby realizing the regulation of the coordination environment and electron density of metal catalytic active sites. This process effectively adjusts the d-orbital energy level of the metal active center, optimizes the binding ability of oxygen molecules to the active sites, and simultaneously reduces the activation energy of the oxygen reduction reaction, significantly accelerating the reaction kinetics rate and improving the catalytic performance.

[0022] 2. The present invention utilizes the synergistic effect of the strain effect of the core and the rigid carbon framework of the outer core-shell to form a nanoscale spatial isolation region inside the catalyst. This unique structure can not only construct an effective three-dimensional through-hole mass transfer network but also significantly inhibit the thermal migration and Ostwald ripening of metal active sites by means of the geometric confinement effect.

[0023] 3. The present invention optimizes the distribution state of metal sites through surface strain regulation, improves the exposure degree of metal sites, thereby increasing the contact probability between oxygen and active sites in the catalytic reaction, and greatly enhancing the catalytic activity and stability.

[0024] 4. The present invention has the advantages of low reagent cost, high preparation efficiency, good repeatability, etc. The preparation process is simple and easy to operate, and the catalytic activity of the prepared catalyst can be comparable to that of commercial platinum-based catalysts. Description of the Drawings

[0025] Figure 1 SEM image of Co-NC@Zn-NC-800 prepared in Example 1

[0026] Figure 2 STEM image of Co-NC@Zn-NC-800 prepared in Example 1

[0027] Figure 3 STEM image of Co-NC@Zn-NC-700 prepared in Example 2

[0028] Figure 4 STEM image of Co-NC@Zn-NC-900 prepared in Example 3

[0029] Figure 5 STEM image of Co-NC@Zn-NC-1000 prepared in Example 4

[0030] Figure 6 X-ray powder diffraction test results of the MOF-derived carbon catalysts for regulating the oxygen reduction catalytic performance based on deformation prepared in Examples 1-4.

[0031] Figure 7Linear sweep voltammograms of the MOF-derived carbon catalysts prepared in Examples 1-7 and commercial 20 wt% Pt / C in Example 1 at 1600 rpm in a saturated oxygen 0.1 M potassium hydroxide solution.

[0032] Figure 8 Galvanostatic discharge curves and power density curves of a zinc-air battery assembled with the Co-NC@Zn-NC-800 catalyst prepared in Example 1 and commercial 20 wt% Pt / C as the cathode. Detailed Description of the Invention

[0033] The above content of the present invention will be further described in detail below through examples. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. Any non-essential improvements and adjustments made to the present invention based on the above content of the present invention should still fall within the protection scope of the present invention.

[0034] Example 1

[0035] (1) A mixed solution was prepared by dissolving 7.5 g of 2-methylimidazole, 150 mg of cetyltrimethylammonium bromide, 600 mg of cobalt nitrate, and 200 mL of deionized water. It was ultrasonically dispersed evenly at room temperature, stirred at 400 rpm for 1 h, and then left to stand for 6 h. The product was collected after centrifugation and vacuum filtration, and the product was dried in vacuo at 60 °C for 6 h to obtain cubic MOF cores with a size of about 200 nm.

[0036] (2) A mixed solution was prepared by dissolving 1.0 g of the cubic MOF cores synthesized in Example 1(1), 8.5 g of 2-methylimidazole, 600 mg of zinc nitrate, and 200 mL of deionized water. It was ultrasonically dispersed evenly at room temperature, stirred at 400 rpm for 1 h, and then left to stand for 6 h. The product was collected after centrifugation and vacuum filtration, and the product was dried in vacuo at 60 °C for 6 h to obtain double-layer cubic MOF precursors.

[0037] (3) 1.0 g of the double-layer cubic MOF precursors synthesized in Example 1(2) was placed in a tube furnace. Under an argon atmosphere, it was heated to 800 °C at a heating rate of 5 °C / min, held for 2 h, and then cooled to obtain the Co-NC@Zn-NC-800 catalyst with a maximum interlayer spacing of about 55 nm.

[0038] Example 2

[0039] (1) A mixed solution was prepared by dissolving 7.0 g of 5-methylimidazole, 200 mg of cetyltrimethylammonium bromide, 450 mg of cobalt acetate and 200 mL of deionized water. It was ultrasonically dispersed until homogeneous at room temperature, stirred at 400 rpm for 1.5 h and left standing for 7 h. The product was collected after centrifugation and vacuum filtration, and then dried in vacuo at 60 °C for 6 h to obtain cubic MOF cores with a size of approximately 230 nm.

[0040] (2) A mixed solution was prepared by dissolving 1.0 g of the cubic MOF cores synthesized in Example 2(1), 8.0 g of 5-methylimidazole, 450 mg of zinc oxalate and 200 mL of deionized water. It was ultrasonically dispersed until homogeneous at room temperature, stirred at 400 rpm for 1.5 h and left standing for 7 h. The product was collected after centrifugation and vacuum filtration, and then dried in vacuo at 60 °C for 6 h to obtain a double-layer cubic MOF precursor.

[0041] (3) 1.0 g of the double-layer cubic MOF precursor obtained in Example 2(2) was placed in a tubular furnace filled with argon and heated to 700 °C at a heating rate of 3 °C / min. After continuous carbonization for 2 h, the temperature was decreased to obtain a Co-NC@Zn-NC-700 catalyst with a maximum interlayer spacing of approximately 40 nm.

[0042] Example 3

[0043] (1) A mixed solution was prepared by dissolving 7.5 g of 5-methylimidazole aqueous solution, 80 mg of cetyltrimethylammonium bromide, 700 mg of cobalt sulfate and 200 mL of deionized water. It was ultrasonically dispersed until homogeneous at room temperature, stirred at 500 rpm for 1 h and left standing for 5 h. The product was collected after centrifugation and vacuum filtration, and then dried in vacuo at 60 °C for 6 h to obtain cubic MOF cores with a size of approximately 230 nm.

[0044] (2) A mixed solution was prepared by dissolving 1.0 g of the cubic MOF cores synthesized in Example 3(1), 8.0 g of 5-methylimidazole aqueous solution, 700 mg of zinc sulfate and 200 mL of deionized water. It was stirred at 500 rpm for 1 h and left standing for 5 h. The product was collected after centrifugation and vacuum filtration, and then dried in vacuo at 60 °C for 6 h to obtain a double-layer cubic MOF precursor.

[0045] (3) 1.0 g of the double-layer cubic MOF precursor synthesized in Example 3(2) was placed in a tubular furnace filled with argon and heated to 900 °C at a heating rate of 5 °C / min. After continuous carbonization for 2 h, the temperature was decreased to obtain a Co-NC@Zn-NC-900 catalyst with a maximum interlayer spacing of approximately 65 nm.

[0046] Example 4

[0047] (1) A mixed solution was prepared by dissolving 7.5 g of 2-methylimidazole, 250 mg of cetyltrimethylammonium bromide, 650 mg of cobalt nitrate and 200 mL of deionized water. The mixture was stirred at 400 rpm for 0.5 h and then left to stand for 5 h. The product was collected by centrifugation and vacuum filtration, and then vacuum dried at 60 °C for 6 h to obtain cubic MOF cores with a size of about 230 nm.

[0048] (2) A mixed solution was prepared by dissolving 1.0 g of the cubic MOF cores synthesized in Example 4(1), 9.0 g of 2-methylimidazole, 600 mg of zinc chloride and 200 mL of deionized water. The mixture was stirred at 400 rpm for 0.5 h and then left to stand for 7 h. The product was collected by centrifugation and vacuum filtration, and then vacuum dried at 60 °C for 6 h to obtain double-layer cubic MOF precursors.

[0049] (3) 1.0 g of the double-layer cubic MOF precursors synthesized in Example 4(2) was placed in a tubular furnace filled with argon and heated to 1000 °C at a heating rate of 4 °C / min. After continuous carbonization for 1 h, the temperature was decreased to obtain the Co-NC@Zn-NC-1000 catalyst with a damaged interlayer structure.

[0050] Example 5

[0051] Referring to Example 1, the only difference was that the carbonization temperature was adjusted to 750 °C to obtain the Co-NC@Zn-NC-750 catalyst with a maximum interlayer spacing of about 50 nm.

[0052] Example 6

[0053] Referring to Example 1, the only difference was that the carbonization temperature was adjusted to 850 °C to obtain the Co-NC@Zn-NC-850 catalyst with a maximum interlayer spacing of about 60 nm.

[0054] Example 7

[0055] Referring to Example 1, the only difference was that the carbonization temperature was adjusted to 950 °C to obtain the Co-NC@Zn-NC-950 catalyst with a maximum interlayer spacing of about 70 nm.

[0056] Comparative Example 1

[0057] This Comparative Example 1 was commercial 20 wt% Pt / C.

[0058] Comparative Example 2

[0059] Referring to Example 1, the difference was that step (2) of Example 1 was not carried out and other conditions remained unchanged to obtain the Co-NC-800 catalyst.

[0060] Comparative Example 3

[0061] Referring to Example 1, the difference is that cobalt nitrate in step (1) of Example 1 is replaced with zinc nitrate in equal proportion, and step (2) of Example 1 is not carried out, and other conditions remain unchanged, to obtain the Zn-NC-800 catalyst.

[0062] Comparative Example 4

[0063] Referring to Example 1, the difference is that zinc nitrate is not added in step (2) of Example 1, and other conditions remain unchanged, to obtain the Co-NC@NC-800 catalyst.

[0064] Comparative Example 5

[0065] Referring to Example 1, the difference is that cobalt nitrate in step (1) of Example 1 is replaced with zinc nitrate in equal proportion, and zinc nitrate is not added in step (2) of Example 1, and other conditions remain unchanged, to obtain the Zn-NC@NC-800 catalyst.

[0066] Comparative Example 6

[0067] Referring to Example 1, the difference is that the stirring condition in step (2) of Example 1 is changed to stirring in an ice-water bath, and other conditions remain unchanged, to obtain the Co-NC / Zn-NC-800 catalyst.

[0068] Comparative Example 7

[0069] Referring to Example 1, the difference is that 2-methylimidazole, zinc nitrate and deionized water in step (2) of Example 1 are pre-mixed and stirred for 1 h, and then the cubic MOF core is added, and other conditions remain unchanged, to obtain the Co-NC-Zn-NC-800 catalyst.

[0070] Comparative Example 8

[0071] Referring to Example 1, the difference is that imidazole ligands and cationic surfactants are not added in step (2) of Example 1, and other conditions remain unchanged, and finally the Co-NC-Zn-800 catalyst is obtained.

[0072] Comparative Example 9

[0073] Referring to Example 1, the difference is that the cubic MOF core, zinc nitrate and deionized water in step (2) of Example 1 are pre-mixed and stirred for 1 h, and then 2-methylimidazole is added, and other conditions remain unchanged, to obtain the Co-NC+Zn-NC-800 catalyst.

[0074] Comparative Example 10

[0075] Referring to Example 1, the difference is that the cubic MOF core, 2-methylimidazole, and deionized water in step (2) of Example 1 are premixed and stirred for 1 h, and then zinc nitrate is added. The carbonization temperature in step (3) of Example 1 is adjusted to 850 °C to obtain the Co-NC&Zn-NC-850 catalyst.

[0076] Performance Test

[0077] 1. Microstructure

[0078] Figure 1 The SEM image of the oxygen reduction catalyst Co-NC@Zn-NC-800 prepared in Example 1 shows that Figure 1 it can be seen that the catalyst Co-NC@Zn-NC-800 maintains a cubic morphology, the particle size is about 230 nm, and there are no obvious particulate phases on the surface, proving that the carbonization treatment does not cause a large amount of metal sites to agglomerate and precipitate, so that the active sites are evenly distributed inside the catalyst.

[0079] 2. Surface Strain Analysis

[0080] Figures 2 - 5 The STEM images of the oxygen reduction catalysts Co-NC@Zn-NC-800, Co-NC@Zn-NC-700, Co-NC@Zn-NC-900, and Co-NC@Zn-NC-1000 prepared in Examples 1-4 are shown respectively. It can be observed from the figure that when the carbonization temperature increases from 700 to 900 °C, the micro-mesoporous structure on the outer layer of the particles gradually increases, and the surface strain degree of the core inside the particles also gradually increases, forming an obvious nano-scale space isolation region between the outer layer and the core-shell. When the carbonization temperature is increased to 1000 °C, the internal core structure collapses due to the stress exceeding its thermo-mechanical stability limit, and the bilayer structure cannot be maintained.

[0081] 3. Composition Analysis

[0082] Figure 6 The wide-angle X-ray diffraction patterns of the oxygen reduction catalysts Co-NC@Zn-NC-800, Co-NC@Zn-NC-700, Co-NC@Zn-NC-900, and Co-NC@Zn-NC-1000 prepared in Examples 1-4 are shown, where: the abscissa 2-Theta represents the diffraction angle 2θ, and the ordinate Intensity represents the intensity of the diffraction peak. It can be seen from Figure 6 the figure that the catalysts all show a (002) diffraction peak of carbon near 23°, and diffraction peaks of Co(111), (200), and (220) appear near 44.3°, 51.5°, and 75.9° respectively, and there are no diffraction peaks of other phases. This shows that the catalyst contains elemental Co nanoparticles.

[0083] 4. Catalytic Activity

[0084] The oxygen reduction performance of the oxygen reduction catalysts prepared in Examples 1-7 and Comparative Examples 1-10 was tested in a three-electrode system. The specific steps are as follows: The oxygen reduction catalysts prepared in Examples 1-7 and the powders of Comparative Examples 1-10 were separately dispersed in ethanol, and a proton conductor binder (5% Nafion solution) was added to prepare catalyst inks (each 1 mL of catalyst ink contained 20 μL of proton conductor binder), and then sonicated for 30 min. Then, the ink-like solution was dropped onto the surface of a glassy carbon electrode and air-dried naturally to form a catalyst film, which was used as a working electrode for testing. A platinum wire was used as the counter electrode, and silver chloride was used as the reference electrode, and the corresponding electrode potential was converted to the reversible hydrogen electrode (RHE) potential to test the oxygen reduction half-wave potential of each catalyst in saturated oxygen 0.1 M potassium hydroxide. The linear sweep voltammogram (LSV spectrum) of the oxygen reduction catalysts prepared in Examples 1-7 and Comparative Example 1 in a saturated oxygen alkaline electrode solution is as Figure 7 shown (in the figure, the abscissa Potential represents voltage, and the ordinate Current density represents current density). At the same time, the oxygen reduction half-wave potentials of the corresponding catalysts of Examples 1-7 and Comparative Examples 1-10 are shown in Table 1 in detail.

[0085] Table 1

[0086] As can be seen from Table 1, the oxygen reduction half-wave potential of the oxygen reduction catalyst prepared in Example 1 in an alkaline electrolyte (saturated oxygen 0.1 M potassium hydroxide) is 0.84 V, showing excellent oxygen reduction catalytic performance.

[0087] Compared with Example 1, in Examples 2-7, due to different carbonization temperatures, the outer layer lacks a micro-mesoporous structure or the surface strain degree of the core is too weak or too strong, affecting the mass transfer efficiency and the electronic structure of the active sites, resulting in the oxygen reduction catalytic performance being inferior to that of Example 1. However, except for Example 2 (Co-NC@Zn-NC-700), the oxygen reduction half-wave potentials of the oxygen reduction catalysts prepared in Examples 3-7 in an alkaline electrolyte (0.1 M potassium hydroxide) are 0.78-0.82 V, and they also have good oxygen reduction catalytic performance.

[0088] Compared with Example 1, the oxygen reduction half-wave potential of commercial 20 wt% Pt / C in Comparative Example 1 is only 0.81 V, and its oxygen reduction catalytic performance is significantly lower than that of Example 1. This shows that the catalyst prepared in Example 1 has better oxygen reduction catalytic performance than commercial 20 wt% Pt / C catalyst.

[0089] Comparative Examples 2-5, as compared with Example 1, although the same carbonization temperature was used, due to the lack of bilayer structure design in the preparation process, the absence of introduction of metal salts or the change of key synthesis steps, there were deficiencies in the interfacial structure and nano-space isolation region of the material, insufficient active sites and electron structure mismatch. The oxygen reduction half-wave potential was only 0.73 - 0.76 V, and the oxygen reduction catalytic performance was significantly lower than that of Example 1.

[0090] Comparative Examples 6-10, as compared with Example 1, although having the same elemental composition, due to the differences in key synthesis processes, the hetero-interfaces were incompatible, and a cubic bilayer hetero-structure could not be constructed, resulting in the failure of surface strain regulation behavior. The oxygen reduction half-wave potential was only 0.59 - 0.75 V, and the oxygen reduction catalytic performance was far inferior to that of Example 1.

[0091] 5. Application Analysis

[0092] Figure 8 The constant current discharge curves and power density curves of the zinc-air battery with the catalysts of Example 1 and Comparative Example 1 as the cathode catalyst are shown. The power density of the zinc-air battery assembled with the Co-NC@Zn-NC-800 catalyst prepared in Example 1 was 164 mW cm -2 ², higher than that of the commercial 20 wt% Pt / C catalyst. The experimental data show that the Co-NC@Zn-NC-800 catalyst exhibits excellent catalytic activity and working condition adaptability in the zinc-air battery system. Its performance advantages are derived from the surface strain-optimized coordination and electron structure of metal active sites, the three-dimensional through-hole mass transfer network jointly constructed by micropores and mesopores accelerating the transport rate of reactants, and the nano-scale space isolation region and geometric confinement effect effectively suppressing the thermal migration and Ostwald ripening of metal active sites. Based on the multiple synergistic effects caused by the intrinsic micro-nano structure evolution induced by surface strain, the activity and stability of the catalyst are significantly improved, providing a key material solution for the performance optimization of zinc-air batteries.

[0093] For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made without creative labor. Therefore, all simple improvements made by those skilled in the art based on the disclosure of the present invention should fall within the protection scope of the present invention. The above embodiments are the preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made thereto shall fall within the protection scope of the present invention.

Claims

1. A preparation method and application of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain, characterized in that, It includes the following steps: (1) Mix and disperse an imidazole ligand, a cationic surfactant, and a metal cobalt salt in a solvent, react under certain conditions, filter, and vacuum dry to obtain a cubic MOF core, where the aspect ratio of the length, width, and height of the cubic MOF core is close to 1:1:1; (2) Mix and disperse the cubic MOF core, an imidazole ligand, and a zinc salt in a solvent, react under certain conditions, filter, and vacuum dry to obtain a cubic double-layer structure MOF precursor, where the volume ratio of the inner and outer layers of the cubic double-layer MOF precursor is 1:1.5; (3) Place the cubic double-layer structure MOF precursor in an inert atmosphere for carbonization treatment to prepare an oxygen reduction catalyst with a cubic structure of the outer core-shell and different degrees of deformation of the inner core. The imidazole ligand described in steps (1) and (2) preferably includes one or more of 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, and 5-methylimidazole; The cationic surfactant described in step (1) includes one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and tetracosyltrimethylammonium bromide; The metal cobalt salt described in step (1) includes one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt oxalate; The metal zinc salt described in step (2) includes one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, and zinc oxalate.

2. The preparation method of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain according to claim 1, characterized in that, The certain conditions described in steps (1) and (2) are as follows: first stir for 0.5 - 1 h, then stand for 5 - 8 h, the stirring speed is 400 - 600 rpm, and the solvent used is one or more of water, ethanol, and methanol.

3. The preparation method of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain according to claim 1, characterized in that The carbonization temperature range described in step (2) is 700 - 1000 °C, the carbonization time is 1 - 3 h, and the heating rate to the carbonization temperature is 3 - 5 °C / min.

4. The preparation method of a MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain according to claim 1, characterized in that, The mass ratios of the imidazole ligand to the cationic surfactant and the cobalt salt described in step (1) are 1:(0.01 - 0.06) and 1:(0.05 - 0.10), respectively. The mass ratios of the cubic MOF core to the imidazole ligand and the zinc salt described in step (2) are 1:(15.00 - 20.00) and 1:(1.00 - 1.50), respectively.

5. A MOF-derived carbon oxygen reduction catalyst with surface strain-regulated oxygen reduction catalytic performance prepared by the preparation method of the MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain described in any one of claims 1 - 4.

6. Use of the MOF-derived carbon catalyst for regulating oxygen reduction catalytic performance based on surface strain in a battery cathode, characterized in that, The battery is a zinc-air battery.

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