M-N-C catalyst synthesis method

Abstract

The invention relates to the technical field of catalyst preparation, in particular to an M-N-C catalyst synthesis method which comprises the following steps: S101, obtaining a metal precursor and an MOF material, and determining dynamic loading conditions of metal elements based on a preset metal gasification temperature; s102, high-temperature gas phase transmission is executed, the metal precursor is gasified to form metal steam under the protective atmosphere, the pore structure of the MOF material is regulated and controlled through the dynamic temperature gradient, and the metal steam and the MOF material are made to react on a gas-solid phase interface; and S103, on the basis of the gas-solid phase interface reaction, optimizing the ratio of the metal-Nx site to the MOF derived carbon site to obtain the M-N-C catalyst with double active sites. When the catalyst is synthesized, the catalyst with the same catalytic effect can be synthesized by using an extremely low amount of metal elements, and the catalyst obtained by the method has extremely high active sites, so that the catalyst has remarkable cost benefits in industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a method for synthesizing an MNC catalyst. Background Art

[0002] As the global energy transition accelerates, the development of efficient and low-cost electrocatalytic materials has become the key to solving the problems of fossil fuel consumption and environmental pollution. MNC catalysts, due to their high activity, high stability and controllable electronic structure, have shown great potential in important electrocatalytic fields such as oxygen reduction reaction and carbon dioxide reduction reaction. However, traditional synthesis methods generally have problems such as low raw material utilization, complex processes and high costs.

[0003] Existing synthesis methods, including co-precipitation, seed growth, hard template, soft template, self-template, self-oxidation-reduction and electrospinning, can all make the material have a very high half-slope potential, reaching about 0.88V. However, these synthesis methods waste raw materials, have high synthesis costs, and are not conducive to industrial production. Summary of the Invention

[0004] The present invention aims to solve the technical problems existing in the prior art and provides a method for synthesizing an MNC catalyst.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: A method for synthesizing an MNC catalyst comprises the following steps: S101, obtaining a metal precursor and a MOF material, and determining a dynamic loading condition of the metal element based on a preset metal vaporization temperature; S102, performing high-temperature gas phase transmission to vaporize the metal precursor and form metal vapor under a protective atmosphere, and regulating the pore structure of the MOF material through a dynamic temperature gradient to cause the metal vapor to react with the MOF material at the gas-solid interface; S103, Optimizing Metal-N Based on Gas-Solid Interface Reaction x The ratio of carbon sites to MOF-derived carbon sites was adjusted to obtain MNC catalysts with dual active sites.

[0006] Preferably, the metal precursor includes a compound group consisting of a metal precursor selected from ferric nitrate hexahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, ferric acetylacetonate, manganese acetylacetonate, platinum acetylacetonate, ferrous chloride, cobalt chloride, and platinum chloride, wherein the nitrate is preferably selected from ferric nitrate hexahydrate or cobalt nitrate hexahydrate, the acetylacetonate is preferably selected from ferric acetylacetonate or platinum acetylacetonate, and the chloride is preferably selected from nickel chloride or platinum chloride. All precursors must be vacuum dried before use to remove crystal water and screened by particle size to ensure particle uniformity. The mass ratio of the metal precursor to the MOF material is controlled within the range of 1:5 to 1:20.

[0007] Preferably, the MOF material is ZIF-8 or ZIF-67, and its pore structure is dynamically controlled by a preset etchant (such as tannic acid or hydrochloric acid) at a high temperature. The specific parameters of the etching process include: S1, the etchant concentration is 5-10g / L ethanol or aqueous solution, the etching time is 12-24 hours, and the etching temperature is 25-60°C. By controlling the etching time and temperature, the pore size distribution and specific surface area of ​​the MOF material can be precisely controlled; S2. The etched MOF material needs to undergo post-processing steps such as centrifugation (3000-5000 rpm, 10 min), washing with deionized water 3-5 times, and vacuum drying at 60°C for 24 h; Preferably, the high-temperature gas phase transport includes a first temperature interval and a second temperature interval. The first temperature interval heats the metal precursor to its initial vaporization temperature at a heating rate of 5-10°C / min. The second temperature interval is used for the deep combination of metal vapor and MOF material, and the temperature gradient is adjusted in real time based on the metal vaporization rate. The holding time of each temperature zone is dynamically adjusted by online analysis of the metal vapor partial pressure by a mass spectrometer to ensure that the metal species are evenly distributed on the MOF carrier in the form of atoms or nanoclusters.

[0008] Preferably, the high-temperature stage adopts pulse heating, including multiple temperature cycle cycles, each cycle consists of a rapid heating stage and a heat preservation stage, the heating rate is 10-15°C / min, and the heat preservation time of the heat preservation stage is 10-30 minutes. The rapid heating stage is achieved by induction heating or microwave-assisted heating, and the heat preservation stage adopts traditional resistance heating to maintain temperature stability. The maximum temperature of each pulse cycle is set to 90% to 110% of the metal vaporization temperature. Through 3-5 cycles of pulse treatment, the dispersion of metal nanoparticles can be improved, and the particle size distribution is 2-5nm. The dispersion of metal nanoparticles is optimized by intermittent thermal shock to avoid agglomeration.

[0009] Preferably, the nitrogen doping level is regulated at high temperature by introducing a second preset gas such as NH3 or H2, wherein the NH3 flow rate is 10-50 mL / min and the H2 flow rate is 5-20 mL / min, so as to accurately determine the active site density and type. The specific operation process is as follows: S1. During the holding stage after the metal vaporization is completed, gases precisely controlled by a mass flow meter are introduced into the reaction system. The gas mixing ratio is adjusted according to the requirements of the target active sites, usually 1:1 to 4:1; S2, doping treatment time is 30-120 minutes, the treatment temperature is maintained at 800-1000 ℃, the introduction of NH3 can promote the metal-N x The formation of active sites is facilitated by H2, while H2 helps to regulate the reduction degree and defect density of the carbon support.

[0010] Preferably, during the synthesis process, the phase change process of the metal precursor and the structural evolution of the MOF material are tracked in real time by in-situ X-ray diffraction (XRD), the metal vapor partial pressure and gas product composition are monitored in real time by mass spectrometry (MS), and the changes in surface functional groups are observed by infrared spectroscopy. When incomplete metal vaporization is detected, the holding time is automatically extended by 10-20 minutes. When metal agglomeration is detected, the system immediately adjusts the temperature gradient or introduces pulse cooling to ensure the ideal bonding state between the metal and the MOF material. Preferably, the MOF material after the reaction is recovered by centrifugation or filtration, and the specific steps include: S1. After the reaction is completed, the system is cooled to room temperature, the reaction product is taken out, and the metal species adsorbed on the surface are removed by ultrasonic-assisted solvent washing; S2, after centrifugation (4000 rpm, 15 min), acid treatment (0.1 M HCL, 2 h) to remove residual metal, and finally vacuum drying (80 ° C, 12 h) and light calcination (300 ° C, 2 h, N2 atmosphere) to restore its porous structure; S3. The regenerated MOF carrier is characterized to confirm that its specific surface area recovery rate is greater than 90%, and after vacuum drying, it can be put back into high-temperature reaction to achieve continuous preparation of the catalyst.

[0011] Preferably, the metal-N is determined by X-ray photoelectron spectroscopy XPS or transmission electron microscopy. x sites and the synergistic effect of MOF-derived carbon sites, where XPS is used to analyze the chemical state of nitrogen species and TEM is used to observe the size distribution of metal nanoparticles; Preferably, a fluidized bed reactor is used to achieve large-scale continuous preparation of the catalyst, wherein the temperature control accuracy in the reactor is ±5°C, the gas flow rate is 100-500 L / h, and the catalyst single batch output can reach 1-10 kg.

[0012] The beneficial effects of the present invention are: when synthesizing this catalyst, the present invention can use an extremely low amount of metal elements to synthesize a catalyst with the same catalytic effect. The catalyst obtained by this method has extremely high active sites, which makes the catalyst significantly cost-effective in industrial applications. In addition, due to its high atomic utilization rate, the batch preparation of the catalyst in the reaction process is greatly improved, thereby reducing the waste of metal elements and increasing the yield of the product. The stability of this catalyst is also remarkable. It can still maintain a high catalytic performance after tens of thousands of cycles and can be applied to various metal elements. Different metal elements have different vaporization temperatures. At this temperature, the metal elements will combine with the MOF material as the gas flows, thereby synthesizing a material with the same catalytic effect as the metal elements. This type of synthesized material not only has the active sites of the metal elements in ORR, but the MOF material also has active sites at this high temperature. The two different active sites complement each other to improve the active sites of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a flow chart of the present invention; Figure 2 This is a comparison chart of the ORR performance of the MOF material of the present invention and the Fe-NC material fired separately; Figure 3 This is a diagram showing the ORR performance improvement of the MOF and Fe-NC co-fired according to the present invention; Figure 4 is a performance defect diagram of the non-co-fired material of the present invention; Figure 5 This is a diagram to verify the feasibility of industrialization. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0015] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of this application, "plurality" means two or more, unless otherwise specifically specified.

[0016] In the description of this application, the term "for example" is used to mean "used as an example, illustration or explanation". Any embodiment described as "for example" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any person skilled in the art to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art will recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present invention with unnecessary details. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in this application.

[0017] like Figure 1 This embodiment provides: a method for synthesizing an MNC catalyst, comprising the following steps: S101. Obtaining a metal precursor and MOF material: Based on a preset metal vaporization temperature, the dynamic loading conditions of the metal element are determined through thermodynamic calculations to ensure atomic-level contact and uniform distribution of the metal precursor and the MOF material during the vaporization process; S102, performing high-temperature gas phase transport: vaporizing the metal precursor to form metal vapor under a protective atmosphere (such as nitrogen or argon), and simultaneously regulating the pore structure and surface chemical properties of the MOF material through a dynamic temperature gradient, so that the metal vapor and the MOF material react at the gas-solid interface; S103, determine the distribution of active sites: based on the kinetic parameters of the gas-solid interface reaction, optimize the metal-N x The ratio of carbon sites to MOF-derived carbon sites was optimized, and finally an efficient MNC catalyst with dual active sites was obtained.

[0018] Furthermore, the metal precursor includes volatile metal compounds such as nitrates, acetylacetonates or chlorides of Fe, Mn, Co, Ni or Pt, wherein the nitrate is preferably selected from ferric nitrate hexahydrate or cobalt nitrate hexahydrate because it can produce uniform metal oxide intermediates during the heating process, the acetylacetonate is preferably selected from ferric acetylacetonate or platinum acetylacetonate, such precursors have a low sublimation temperature and good thermal decomposition properties, the chloride is preferably selected from nickel chloride or platinum chloride, all precursors must be vacuum dried (60-80 ° C, 12h) before use to remove crystal water, and particle size screening (100-200 mesh) is performed to ensure particle uniformity, and the mass ratio of metal precursor to MOF material is controlled in the range of 1:5 to 1:20.

[0019] The metal precursor is selected from the compound group consisting of ferric nitrate hexahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, ferric acetylacetonate, manganese acetylacetonate, platinum acetylacetonate, ferrous chloride, cobalt chloride and platinum chloride.

[0020] Furthermore, the MOF material is ZIF-8 or ZIF-67, and its pore structure is dynamically controlled by a preset etchant (such as tannic acid or hydrochloric acid) at a high temperature stage. The specific parameters of the etching process include: S1, the etchant concentration is 5-10g / L ethanol or aqueous solution, the etching time is 12-24 hours, and the etching temperature is 25-60°C. By controlling the etching time and temperature, the pore size distribution and specific surface area of ​​the MOF material can be precisely controlled; S2. The etched MOF material needs to undergo post-processing steps such as centrifugation (3000-5000 rpm, 10 min), washing with deionized water 3-5 times, and vacuum drying at 60°C for 24 h; This dynamic reconstruction process enables the MOF material to produce abundant mesopores and macropores while maintaining its skeleton structure, providing an ideal carrier environment for the subsequent diffusion and anchoring of metal vapor.

[0021] Furthermore, the high-temperature gas-phase transport includes a first temperature range (800-1000°C) and a second temperature range (1000-1200°C). In the first temperature range, the metal precursor is heated to its initial vaporization temperature at a heating rate of 5-10°C / min. This stage mainly realizes the thermal decomposition and preliminary vaporization of the metal precursor. The second temperature range is used for the deep combination of metal vapor and MOF material, and the temperature gradient is adjusted in real time based on the metal vaporization rate. The holding time of each temperature zone is dynamically adjusted (usually 30-120min) by online analysis of the metal vapor partial pressure by a mass spectrometer. This gradient temperature control method can effectively avoid premature agglomeration of metal particles and ensure that the metal species are evenly distributed on the MOF carrier in the form of atoms or nanoclusters.

[0022] Furthermore, the high-temperature stage adopts pulse heating, including multiple temperature cycle cycles, each cycle consists of a rapid heating stage and a heat preservation stage, the heating rate is 10-15℃ / min, and the heat preservation time of the heat preservation stage is 10-30 minutes. The rapid heating stage is achieved by induction heating or microwave-assisted heating, which can increase the local temperature to the target value in a short time. The heat preservation stage adopts traditional resistance heating to maintain temperature stability. The maximum temperature of each pulse cycle is set to 90% to 110% of the metal vaporization temperature. Through 3-5 cycles of pulse treatment, the dispersion of metal nanoparticles can be significantly improved, and the particle size distribution is 2-5nm. The dispersion of metal nanoparticles is optimized by intermittent thermal shock to avoid agglomeration.

[0023] The advantages of pulsed thermal synthesis are: the thermal shock generated by rapid heating can effectively inhibit the surface diffusion of metal atoms and prevent their agglomeration, and the intermittent insulation stage provides sufficient time for the chemical bonding between the metal and the MOF carrier. The process parameters can be optimized and determined through preliminary experiments based on the characteristics of different metal precursors.

[0024] Furthermore, the nitrogen doping level is regulated at high temperature by introducing a second preset gas such as NH3 or H2, with an NH3 flow rate of 10-50 mL / min and an H2 flow rate of 5-20 mL / min, thereby accurately determining the active site density and type. The specific operation process is as follows: S1. During the holding stage after the metal vaporization is completed, gases precisely controlled by mass flow meters are introduced into the reaction system (NH3 flow rate is 10-50 mL / min, H2 flow rate is 5-20 mL / min). The gas mixing ratio is adjusted according to the requirements of the target active sites, usually 1:1 to 4:1; S2, doping treatment time is 30-120 minutes, the treatment temperature is maintained at 800-1000 ℃, the introduction of NH3 can promote the metal-N x The formation of active sites, H2 helps to regulate the reduction degree and defect density of the carbon support. By changing the type, flow rate and treatment time of the doping gas, the content and distribution of nitrogen species on the catalyst surface can be precisely controlled, thereby regulating its catalytic activity and selectivity for specific reactions.

[0025] Furthermore, during the synthesis process, the phase change process of the metal precursor and the structural evolution of the MOF material are tracked in real time through in-situ X-ray diffraction (XRD), the metal vapor partial pressure and gas product composition are monitored in real time through mass spectrometry (MS), and the changes in surface functional groups are observed through infrared spectroscopy. When incomplete metal vaporization is detected, the holding time is automatically extended by 10-20 minutes. When metal agglomeration is detected, the system immediately adjusts the temperature gradient or introduces pulse cooling to ensure the ideal bonding state between the metal and the MOF material. Furthermore, the MOF material after the reaction is recovered by centrifugation or filtration, and the specific steps include: S1. After the reaction is completed, the system is cooled to room temperature, the reaction product is taken out, and the metal species adsorbed on the surface are removed by ultrasonic-assisted solvent washing; S2, after centrifugation (4000 rpm, 15 min), acid treatment (0.1 M HCL, 2 h) to remove residual metal, and finally vacuum drying (80 ° C, 12 h) and light calcination (300 ° C, 2 h, N2 atmosphere) to restore its porous structure; S3. Characterization confirmed that the regenerated MOF carrier has a specific surface area recovery rate of >90%, and after vacuum drying, it can be put back into the high-temperature reaction to achieve continuous preparation of the catalyst. The number of cycles can reach 3-5, and the catalytic performance decay after each cycle does not exceed 5%.

[0026] Furthermore, the metal-N x The synergistic effect of the sites and MOF-derived carbon sites was used to quantitatively characterize the chemical state of the nitride by XPS analysis, and the size distribution and spatial positioning of the metal nanoparticles were revealed by TEM analysis.

[0027] It should be noted that X-ray photoelectron spectroscopy (XPS) is used to quantitatively analyze the chemical state of surface elements, especially the N1s spectrum can distinguish pyridinic nitrogen, metal-N x Transmission electron microscopy combined with elemental surface scanning can intuitively display the size distribution and spatial positioning of metal nanoparticles, and synchrotron radiation X-ray absorption fine structure spectroscopy can analyze the coordination environment and electronic structure of metals.

[0028] Furthermore, a fluidized bed reactor is used to achieve large-scale continuous preparation of the catalyst, wherein the temperature control accuracy in the reactor is ±5°C, the gas flow rate is 100-500L / h, and the catalyst single batch output can reach 1-10kg. Example

[0029] like Figure 3 This embodiment provides: a pulsed thermal synthesis of a Fe-NC catalyst, comprising the following steps: S1. Precursor preparation: dissolve ferric nitrate hexahydrate in anhydrous methanol to prepare a 0.1 M solution, and ultrasonicate for 30 minutes to ensure complete dissolution. The ZIF-8 material is pre-etched with tannic acid for 24 hours, washed by centrifugation, and dried in vacuo at 60°C for 12 hours to obtain a modified support with a pore size of 5-30 nm. S2, pulse thermal synthesis: the precursor and ZIF-8 were mixed at a mass ratio of 1:10, placed in a quartz boat, and placed in a tube furnace; S3. Pulse heating in nitrogen atmosphere: first pulse: heating to 900°C at 10°C / min and holding for 10 min; second pulse: heating to 1100°C at 5°C / min and holding for 2 h; S3, by NH3 pulse input (once every 30min) to control nitrogen doping, Fe-N x / C catalyst.

[0030] It should be noted that by comparing the ORR curves of co-fired and single-fired samples, the half-slope potential of the co-fired sample increased to 0.92 V, and the Tafel slope decreased to 68 mV / dec, proving that the pulse heating and NH3 regulation effectively formed the metal-N x / carbon dual active sites, Figure 3 The two overlapping curves show the complete cooperation between MOF and metal species, which is different from the single fired Figure 2 In stark contrast. Example

[0031] like Figure 2 、 5 This embodiment provides: a gradient temperature field synthesis of a Co-NC catalyst, comprising the following steps: S1. Gradient temperature design: Cobalt acetylacetonate and ZIF-67 were mixed at a ratio of 1:5 to avoid interference from the same elements. Three temperature zones were controlled: the first temperature zone: 800°C (1h, decomposition of Co precursor); the second temperature zone: 1000°C (2h, diffusion of Co vapor); the third temperature zone: 1150°C (1h, Co-N x bonding); S2, monitor the decomposition products of Co(acac) by online mass spectrometry, adjust the H2 flow in real time, when Co + When the signal decreases, the H2 flow rate is increased to suppress Co agglomeration; It should be noted that the catalyst synthesized by the gradient temperature field Figure 5 The half-slope potential of group C reached 0.92V, and the active site density was 22 sites / nm² ( Figure 2 Group B), dynamic control of mass spectrometry feedback increased the Co dispersion by 90%, Figure 2 The performance of MOF alone in the Co-N x Additional contribution of sites. Example

[0032] like Figure 4 This embodiment provides: MOF cyclic regeneration of Pt-NC catalyst, comprising the following steps: S1, first reaction: H2PtCl6 was loaded on ZIF-8 and gasified at 1000℃ for 3 hours to obtain the initial catalyst with a Pt loading of 1wt%; S2. Support regeneration: After the reaction, MOF was ultrasonically washed with DMF at 40kHz for 1h, and then treated with 0.1MHNO3 to remove the Pt residue on the surface. The specific surface area of ​​the regenerated support was restored to 95%; S3. Secondary synthesis: H2PtCl6 was reloaded and reacted under the same conditions. After regeneration, the half-height width of the Pt(111) crystal plane diffraction peak remained unchanged, indicating that the Pt dispersion was not affected.

[0033] It should be noted that the half-slope potential of the Pt catalyst synthesized by regenerating MOF support (the third cycle) was maintained at 0.90 V, and the XRD Figure 4 The Pt(111) crystal plane is not shifted, which proves that the regeneration process does not destroy the support structure. Figure 4 The comparison of the ineffective mixed samples highlights the core role of co-gasification. After 5 cycles, the cost is reduced by 70%, corresponding to Figure 5 Group A uses 50% less metal.

[0034] Comparison Table Example 3: Effect of MOF cycle number on performance Through the synergistic effect of metal vaporization temperature and MOF reconstruction, atomic-level dispersion is achieved, breaking through traditional constant-temperature sintering, avoiding metal agglomeration, and the MOF carrier is recycled, which is in line with the concept of green chemistry.

[0035] Figure 4 The XRD pattern shows that the Pt(111) peak position does not shift even after 5 cycles, proving that the crystal structure is stable. Figure 5 The performance curve of group A shows that the ORR activity is still better than that of the conventional method after 3 cycles.

[0036] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0037] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0038] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0039] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0040] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0041] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0042] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for synthesizing an MNC catalyst, characterized in that: The following steps are involved: S101, obtaining a metal precursor and a MOF material, and determining a dynamic loading condition of the metal element based on a preset metal vaporization temperature; S102, performing high-temperature gas phase transmission to vaporize the metal precursor and form metal vapor under a protective atmosphere, and regulating the pore structure of the MOF material through a dynamic temperature gradient to cause the metal vapor to react with the MOF material at the gas-solid interface; S103, Optimizing Metal-N Based on Gas-Solid Interface Reaction x The ratio of carbon sites to MOF-derived carbon sites was adjusted to obtain MNC catalysts with dual active sites.

2. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The metal precursor is selected from the compound group consisting of ferric nitrate hexahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, ferric acetylacetonate, manganese acetylacetonate, platinum acetylacetonate, ferrous chloride, cobalt chloride and platinum chloride.

3. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The MOF material is one of ZIF-8 and ZIF-67, and its pore structure is dynamically controlled by a preset etchant in the high temperature stage. The specific parameters of the etching process include: S1, the etchant concentration is 5-10g / L ethanol or aqueous solution, the etching time is 12-24 hours, and the etching temperature is 25-60℃; S2. The etched MOF material needs to undergo post-processing steps of centrifugation, deionized water washing and vacuum drying.

4. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The high-temperature gas phase transport includes a first temperature range and a second temperature range. The temperature gradient is determined based on the metal vaporization rate. The first temperature range is 800-1000°C for the initial vaporization of the metal precursor, and the second temperature range is 1000-1200°C for the deep combination of metal vapor and MOF material.

5. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The high temperature stage adopts pulse heating, including multiple rapid heating and holding stages to optimize metal dispersion, with a heating rate of 10-15°C / min and a holding time of 10-30 minutes in the holding stage.

6. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The active site density is determined by regulating the nitrogen doping level at the high temperature stage by introducing a second preset gas.

7. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: During the synthesis process, the degree of metal vaporization is monitored by in situ X-ray diffraction and mass spectrometry, and the temperature parameters are dynamically adjusted.

8. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The MOF material after the reaction is recovered and re-submitted to the high-temperature reaction to achieve continuous preparation of the catalyst.

9. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: The metal-N x The synergistic effect of the sites and MOF-derived carbon sites was used to quantitatively characterize the chemical state of the nitride by XPS analysis, and the size distribution and spatial positioning of the metal nanoparticles were revealed by TEM analysis.

10. The method for synthesizing an MNC catalyst according to claim 1, characterized in that: A fluidized bed reactor is used to achieve large-scale continuous preparation of the catalyst.

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