Microreactor for electrochemically synthesizing ammonia as well as ammonia synthesizing system and method

Abstract

The invention provides a microreactor for electrochemically synthesizing ammonia, the microreactor comprises a membrane electrode assembly and two flow field plates, the membrane electrode assembly comprises a flaky cathode, an anode and a proton exchange membrane, the cathode comprises a substrate and a nitrogen reduction electrocatalyst, and the substrate is a silicon carbide-hexagonal boron nitride composite ceramic material with a porous structure. The electrochemical ammonia synthesis system further comprises a gas supply unit, an electrolyte circulating unit, a power supply, a detection unit, a product separation unit and an intelligent control unit. The invention further provides an electrochemical ammonia synthesis method which comprises the steps of system preparation and activation, continuous reaction process, online monitoring and optimal control, product collection and the like. The porous SiC-BN composite ceramic is used as a cathode substrate material, so that the reaction efficiency is greatly improved, and meanwhile, the transmission rate of reactants and products is also improved. The gas-liquid-solid three-phase reaction interface in the membrane electrode assembly is greatly improved, and the stability of the membrane electrode assembly under the microscopic condition is also greatly enhanced.

Description

Technical Field

[0001] This invention relates to the field of electrochemical ammonia synthesis technology, and more particularly to microreactors, ammonia synthesis systems, and methods for electrochemical ammonia synthesis. Background Technology

[0002] Ammonia is one of the world's most produced inorganic chemicals. As a core raw material for fertilizer manufacturing, ammonia supports global food production and ensures food security. In the industrial sector, it is widely used in the synthesis of numerous chemical products, including pharmaceuticals, plastics, and fibers. Currently, almost all industrial ammonia synthesis is carried out via the Haber-Bosch process, which involves the reaction of nitrogen and hydrogen under catalysts, high temperature, and high pressure. This process requires high temperatures (350-500 degrees Celsius) and high pressures (15-25 MPa), resulting in enormous energy consumption and the emission of hundreds of millions of tons of carbon dioxide annually. To achieve carbon neutrality, developing "green ammonia" synthesis technologies driven by renewable energy under milder conditions is crucial.

[0003] Electrochemical nitrogen reduction reaction for ammonia synthesis, driven by electricity, has attracted considerable attention because it theoretically allows for the production of ammonia from water and nitrogen at ambient temperature and pressure. Compared to traditional processes, this technology offers several advantages: First, the reaction conditions are mild, significantly reducing equipment requirements and energy consumption; second, if powered by renewable energy, a near-zero carbon emission green synthesis process can be achieved; and third, its reaction unit is modular and miniaturized, offering high production flexibility and the potential for decentralized deployment, reducing transportation costs and risks.

[0004] However, this technology is currently still in the laboratory exploration stage and faces several challenges in its practical application: for example, the nitrogen-nitrogen triple bond is extremely stable and difficult to activate, resulting in slow reaction kinetics and extremely low current efficiency (Faraday efficiency); the traditional electrolytic cells commonly used in laboratories (such as H-type cells) have low reactant mass transfer efficiency, and the gas-liquid-solid three-phase reaction interface is limited and unstable, failing to meet the industrial requirements for reaction rate and stability. Furthermore, existing research largely focuses on the development of nanocatalysts, lacking a systematic solution from a reaction engineering perspective that combines high-performance catalysts with advanced reactors that maximize their efficiency. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a microreactor, a synthesis system and method for electrochemical ammonia synthesis, which solves the problems of low reaction efficiency, insufficient mass transfer efficiency and stability of the reactor in the prior art.

[0006] In a first aspect, the present invention proposes a microreactor for electrochemical ammonia synthesis. The microreactor is a sandwich structure with a membrane electrode assembly as its core, including the membrane electrode assembly and two flow field plates. The flow field plates form a cathode reaction chamber and an anode reaction chamber with the cathode and anode of the membrane electrode assembly, respectively. It also includes a temperature control component that is configured in conjunction with the membrane electrode assembly and the flow field plates. The membrane electrode assembly includes a sheet-like cathode and anode, and a proton exchange membrane sandwiched between the cathode and the anode. The cathode includes a substrate and a nitrogen reduction electrocatalyst supported on the surface of the substrate. The substrate is a porous silicon carbide-hexagonal boron nitride composite ceramic material.

[0007] Furthermore, the cathode includes a substrate and a nitrogen reduction electrocatalyst supported on the surface of the substrate, wherein the substrate is a porous silicon carbide-hexagonal boron nitride composite ceramic material.

[0008] Furthermore, the substrate is prepared by the following method: silicon carbide powder, flake-shaped hexagonal boron nitride powder, and a composite sintering aid composed of aluminum nitride and yttrium oxide are mixed and slurried, and a green body with a three-dimensional interconnected pore structure is formed by direct-write molding 3D printing technology; the green body is subjected to controlled pre-oxidation treatment in an air atmosphere; finally, it undergoes a two-step reaction sintering under a protective atmosphere, including a liquid phase generation stage and a high-temperature densification stage, to obtain a dense and conductive porous ceramic material matrix.

[0009] Preferably, the nitrogen reduction electrocatalyst includes bismuth nanocatalysts, iron single-atom catalysts, or ruthenium-based nanoclusters, which are loaded onto the pores and surface of a ceramic substrate by electrodeposition or impregnation calcination.

[0010] Furthermore, the flow field plate includes a cathode flow field plate and an anode flow field plate. The cathode flow field plate has flow channels etched on the cathode side, thereby forming a cathode reaction chamber with the cathode. The anode flow field plate has flow channels etched on the anode side, thereby forming an anode reaction chamber with the anode. The cathode flow field plate has a nitrogen and electrolyte common inlet and a product outlet communicating with the flow channels on the cathode side. The anode flow field plate has an electrolyte inlet and an electrolyte outlet communicating with the flow channels on the anode side.

[0011] Furthermore, the temperature control component includes an independent cooling / heating channel integrated inside the flow field plate. The cooling / heating channel is connected to an external constant temperature circulation device to achieve precise temperature control of the reaction zone through fluid medium circulation.

[0012] Preferably, the anode is a titanium felt or carbon paper coated with an oxygen evolution catalyst.

[0014] Secondly, this invention proposes an electrochemical ammonia synthesis system using the aforementioned microreactor, which, in addition to the microreactor, also includes:

[0015] A gas supply unit, which is connected to the flow field plate of the microreactor, is used to supply nitrogen feedstock to the microreactor;

[0016] An electrolyte circulation unit, which is connected to the flow field plate of the microreactor, is used to provide electrolyte and output the ammonia generated and mixed in the electrolyte;

[0017] A power source, electrically connected to the microreactor, is used to provide a potential difference between the cathode and anode of the membrane electrode assembly.

[0018] The detection unit is connected to the output terminal of the electrolyte circulation unit and is used to detect the ammonia concentration in the electrolyte.

[0019] The product separation unit is connected to the output terminal of the electrolyte circulation unit to achieve the separation of ammonia and electrolyte;

[0020] The intelligent control unit includes a microprocessor, which is electrically connected to the microreactor, gas supply unit, electrolyte circulation unit, power supply, product separation unit, and detection unit to control the operation of the entire system.

[0022] Thirdly, the present invention also proposes an electrochemical method for synthesizing ammonia using the above-described system, comprising the following steps:

[0023] S1. System preparation and activation: Electrolyte is introduced into the anode reaction chamber and the cathode chamber respectively, and high-purity nitrogen gas is introduced into the cathode reaction chamber. An initial voltage of 0.1V-0.3V is applied for electrochemical activation.

[0024] S2. Continuous reaction process: The reaction temperature is maintained at 30℃-60℃ by the temperature control component, and the absolute pressure of the system is maintained at 0.1MPa-0.2MPa. High-purity nitrogen gas saturated with electrolyte is continuously introduced into the cathode reaction chamber to form a gas-liquid two-phase flow. Electrolyte or pure water is introduced into the anode chamber. A DC voltage is applied between the cathode and the anode, and the cathode potential is controlled between -0.4V and -0.8V relative to the reversible hydrogen electrode.

[0025] S3. Online monitoring and optimization control: The ammonia concentration in the cathode outlet liquid is monitored in real time by the detection unit. The intelligent control unit automatically adjusts the applied voltage or nitrogen flow rate according to the measured instantaneous ammonia yield, so that the system always operates near the highest Faraday efficiency range.

[0026] S4. Product Collection: The ammonia-containing cathode outlet liquid is guided to the product separation unit, where high-purity ammonia products are recovered through membrane separation, distillation, or gas stripping.

[0027] Preferably, the electrolyte includes one of dilute sulfuric acid, lithium sulfate, or lithium chloride solution.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention employs a high-strength, chemically stable, and tunably conductive porous SiC-BN composite ceramic as the cathode substrate material for the membrane electrode assembly. Its three-dimensionally interconnected hierarchical porous structure provides the catalyst with a much larger and more stable loading area than traditional carbon cloth or foam metal, thereby significantly improving reaction efficiency and enhancing the transport rates of reactants and products. Combined with the enhancement of the three-phase reaction interface in the microfluidic membrane electrode assembly reactor, the Faradaic efficiency of electrochemical ammonia synthesis can be increased from the current level of generally below 10% to over 30%, with a space-time yield increase of one to two orders of magnitude.

[0030] 2. In this invention, a membrane electrode assembly is used as the core microreactor for electrochemical ammonia synthesis, which realizes the transformation from macroscopic reaction to microscopic reaction. Compared with the traditional H-type electrolytic cell, the contact rate between reactants and reaction interface is greatly increased, and the corresponding mass transfer efficiency is greatly improved. At the same time, the gas-liquid-solid three-phase reaction interface in the membrane electrode assembly is greatly improved, and its stability under microscopic conditions is also greatly enhanced.

[0031] 3. This invention adopts a modular structure, with each microreactor being a separate standard module. Industrial-grade production capacity can be achieved by simply connecting multiple standard modules in parallel. The production capacity is linearly adjustable, perfectly solving the core problem of chemical scale-up and providing a reliable technical prototype for building a distributed, flexible, and adjustable "green ammonia" plant. Detailed Implementation

[0032] The technical solutions of the present invention will be further described below with reference to the embodiments.

[0033] Example 1:

[0034] First, the cathode of the electrode assembly in this embodiment was prepared. Silicon carbide powder with an average particle size of 0.8 μm (70% by volume), hexagonal boron nitride powder with a flake diameter of 2-5 μm (12% by volume), and a composite sintering aid consisting of aluminum nitride and yttrium oxide mixed in a 1:1 molar ratio (6% of the total powder mass) were ball-milled with a dispersant (ammonium polyacrylate, 0.7% of the total powder mass) and deionized water (40% of the total powder mass) to form a uniform slurry. The slurry was then printed into a porous circular green body with a diameter of 2 cm and a thickness of 2 mm using a direct-write 3D printer. The green body was pre-oxidized by heat treatment at 900°C in air for 2 hours. Subsequently, under an argon atmosphere, the temperature was first increased to 1520°C at a rate of 5°C / min and held for 1.5 hours, then increased to 1920°C and held for 1 hour to complete sintering, yielding a gray-black porous SiC-BN composite ceramic disc. Bismuth hydroxide precursor was loaded onto the ceramic disc by impregnation, and then subjected to electrochemical reduction treatment to obtain a cathode loaded with bismuth nanocatalyst.

[0035] The cathode, perfluorosulfonic acid membrane, and IrO2-coated titanium anode are hot-pressed together to form an independent membrane electrode assembly. This assembly, along with a cathode flow field plate and an anode flow field plate, forms a microreactor. The cathode flow field plate has flow channels etched on its cathode-facing side, forming a cathode reaction chamber between it and the cathode. The anode flow field plate has flow channels etched on its anode-facing side, forming an anode reaction chamber between it and the anode. The cathode flow field plate, on its side away from the cathode, has a common inlet for nitrogen and electrolyte, and a product outlet connected to the flow channels. The anode flow field plate, on its side away from the anode, has an electrolyte inlet and an electrolyte outlet connected to the flow channels. The flow field plates integrate cooling / heating channels independent of the flow channels, which are connected to an external constant-temperature circulation device. Precise temperature control of the reaction zone is achieved through fluid medium circulation. The use of membrane electrode assemblies and flow field plates to form a microreactor is existing technology in fuel cells and will not be elaborated upon here.

[0036] The electrochemical ammonia synthesis system in this embodiment has four microreactors connected in parallel. The cathode inlets and outlets of the four microreactors are each connected in parallel to an electrolyte circulation pump, and the anode inlets and outlets of the four microreactors are each connected in parallel to another electrolyte circulation pump, achieving electrolyte circulation. The cathode inlets of the four microreactors are then connected in parallel to a multi-channel horizontal flow pump equipped with a nitrogen mass flow controller, serving as a nitrogen supply unit. The cathode outlets are connected in parallel to an online UV-Vis spectrometer, serving as a detection unit, to continuously monitor the intensity of the characteristic absorption peak of ammonia in the effluent. A DC power supply is provided in parallel with the cathodes and anodes of the four microreactors. Finally, a product separation unit is installed at the cathode outlet to separate ammonia from the electrolyte, while oxygen is separated at the anode outlet.

[0037] The specific steps of the above-mentioned electrochemical ammonia synthesis system during ammonia synthesis are as follows:

[0038] (1) System preparation and activation: 0.05 mol / L dilute sulfuric acid electrolyte is introduced into the anode reaction chamber and the cathode chamber respectively, and high-purity nitrogen gas is introduced into the cathode reaction chamber. An initial voltage of 0.2 V is applied for electrochemical activation.

[0039] (2) Continuous reaction process: The reaction temperature is maintained at 45°C by the temperature control component, the absolute pressure of the system is maintained at 0.15MPa, and high-purity nitrogen gas saturated with electrolyte is continuously introduced into the cathode reaction chamber to form a gas-liquid two-phase flow. Electrolyte or pure water is introduced into the anode chamber. A DC voltage is applied between the cathode and the anode, and the cathode potential is controlled at -0.6V relative to the reversible hydrogen electrode.

[0040] (3) Online monitoring and optimization control: The ammonia concentration in the cathode outlet liquid is monitored in real time by the detection unit. The intelligent control unit automatically adjusts the applied voltage or nitrogen flow rate according to the measured instantaneous ammonia yield, so that the system always operates near the highest Faraday efficiency range.

[0041] (4) Product collection: The cathode outlet containing ammonia is connected to a polytetrafluoroethylene membrane distillation device to separate ammonia, and the electrolyte is recycled; the anode outlet is connected to a PTFE membrane deoxygenation device to discharge the generated oxygen, and the remaining electrolyte is recycled.

[0042] The system ran continuously for 120 hours. Online monitoring data showed that the ammonia yield of the four microreactors remained highly consistent, with an average ammonia yield stabilizing at 1.8 × 10⁻⁶ per square centimeter per hour. -10 The average Faraday efficiency remained at approximately 34%. During operation, the intelligent control system automatically fine-tuned the nitrogen flow rate several times within the standard range of 5 to 8 ml per minute based on slight fluctuations in the spectral signal to maintain optimal performance. After the experiment, disassembly and inspection revealed that the ceramic electrode structure was intact and there was no significant catalyst detachment.

[0044] Example 2:

[0045] First, the cathode of the electrode assembly in this embodiment was prepared. Silicon carbide powder with an average particle size of 0.8 μm (65% by volume), hexagonal boron nitride powder with a flake diameter of 2-5 μm (10% by volume), and a composite sintering aid consisting of aluminum nitride and yttrium oxide mixed in a 1:1 molar ratio (4% of total powder mass) were ball-milled with a dispersant (ammonium polyacrylate, 0.4% of total powder mass) and deionized water (35% of total powder mass) to form a uniform slurry. The slurry was then printed into a porous circular green body with a diameter of 2 cm and a thickness of 2 mm using a direct-write 3D printer. The green body was pre-oxidized by heat treatment at 900°C in air for 2 hours. Subsequently, under an argon atmosphere, the temperature was first increased to 1520°C at a rate of 5°C / min and held for 1.5 hours, then increased to 1920°C and held for 1 hour to complete sintering, yielding a gray-black porous SiC-BN composite ceramic disc. Bismuth hydroxide precursors are loaded onto the ceramic disc by impregnation (by electrodeposition or impregnation-calcination methods, using bismuth nanocatalysts, iron single-atom catalysts, or ruthenium-based nanoclusters), followed by electrochemical reduction treatment to obtain a cathode loaded with bismuth nanocatalysts.

[0046] In this embodiment, the structure of the microreactor is the same as that in Example 1. The electrochemical ammonia synthesis system uses six of the above-mentioned microreactors, and the rest of the structure is the same as that in Example 1.

[0047] In this embodiment, the specific steps of the electrochemical ammonia synthesis system during ammonia synthesis are as follows:

[0048] (1) System preparation and activation: 0.04 mol / L lithium sulfate electrolyte is introduced into the anode reaction chamber and the cathode chamber respectively, and high-purity nitrogen gas is introduced into the cathode reaction chamber. An initial voltage of 0.1 V is applied for electrochemical activation.

[0049] (2) Continuous reaction process: The reaction temperature is maintained at 30°C by the temperature control component, the absolute pressure of the system is maintained at 0.1MPa, and high-purity nitrogen gas saturated with electrolyte is continuously introduced into the cathode reaction chamber to form a gas-liquid two-phase flow. Electrolyte or pure water is introduced into the anode chamber. A DC voltage is applied between the cathode and the anode, and the cathode potential is controlled at -0.4V relative to the reversible hydrogen electrode.

[0050] (3) Online monitoring and optimization control: The ammonia concentration in the cathode outlet liquid is monitored in real time by the detection unit. The intelligent control unit automatically adjusts the applied voltage or nitrogen flow rate according to the measured instantaneous ammonia yield, so that the system always operates near the highest Faraday efficiency range.

[0051] (4) Product collection: The ammonia-containing cathode outlet liquid is guided to the product separation unit, where high-purity ammonia is recovered by gas stripping, and the remaining electrolyte is recycled. The anode outlet is connected to a PTFE membrane deoxygenation unit to discharge the generated oxygen, and the remaining electrolyte is recycled.

[0052] The system ran continuously for 120 hours. Online monitoring data showed that the ammonia yield of the four microreactors remained highly consistent, with an average ammonia yield stabilizing at 1.7 × 10⁻⁶ per square centimeter per hour. -10 The average Faraday efficiency remained at approximately 33% at around 1000 mmol / L. During operation, the intelligent control system automatically adjusted the nitrogen flow rate several times within the standard range of 6 to 8 mL / min based on slight fluctuations in the spectral signal to maintain optimal performance. After the experiment, disassembly and inspection revealed that the ceramic electrode structure was intact and there was no significant catalyst detachment.

[0054] Example 3:

[0055] First, the cathode of the electrode assembly in this embodiment was prepared. Silicon carbide powder with an average particle size of 0.8 μm (75% by volume), hexagonal boron nitride powder with a flake diameter of 2-5 μm (14% by volume), and a composite sintering aid consisting of aluminum nitride and yttrium oxide mixed in a 1:1 molar ratio (8% of the total powder mass) were ball-milled with a dispersant (ammonium polyacrylate, 1% of the total powder mass) and deionized water (45% of the total powder mass) to form a uniform slurry. The slurry was then printed into a porous circular green body with a diameter of 2 cm and a thickness of 2 mm using a direct-write 3D printer. The green body was pre-oxidized by heat treatment at 900°C in air for 2 hours. Subsequently, under an argon atmosphere, the temperature was first increased to 1520°C at a rate of 5°C / min and held for 1.5 hours, then increased to 1920°C and held for 1 hour to complete sintering, yielding a gray-black porous SiC-BN composite ceramic disc. Bismuth hydroxide precursors are loaded onto the ceramic disc by impregnation (by electrodeposition or impregnation-calcination methods, using bismuth nanocatalysts, iron single-atom catalysts, or ruthenium-based nanoclusters), followed by electrochemical reduction treatment to obtain a cathode loaded with bismuth nanocatalysts.

[0056] In this embodiment, the structure of the microreactor is the same as that in Example 1. The electrochemical ammonia synthesis system uses six of the above-mentioned microreactors, and the rest of the structure is the same as that in Example 1.

[0057] In this embodiment, the specific steps of the electrochemical ammonia synthesis system during ammonia synthesis are as follows:

[0058] (1) System preparation and activation: 0.06 mol / L lithium chloride electrolyte is introduced into the anode reaction chamber and the cathode chamber respectively, and high-purity nitrogen gas is introduced into the cathode reaction chamber. An initial voltage of 0.3 V is applied for electrochemical activation.

[0059] (2) Continuous reaction process: The reaction temperature is maintained at 60°C by the temperature control component, the absolute pressure of the system is maintained at 0.2MPa, high-purity nitrogen gas saturated with electrolyte is continuously introduced into the cathode reaction chamber to form a gas-liquid two-phase flow, and electrolyte or pure water is introduced into the anode chamber; a DC voltage is applied between the cathode and the anode, and the cathode potential is controlled at -0.8V relative to the reversible hydrogen electrode.

[0060] (3) Online monitoring and optimization control: The ammonia concentration in the cathode outlet liquid is monitored in real time by the detection unit. The intelligent control unit automatically adjusts the applied voltage or nitrogen flow rate according to the measured instantaneous ammonia yield, so that the system always operates near the highest Faraday efficiency range.

[0061] (4) Product collection: The ammonia-containing cathode outlet liquid is guided to the product separation unit, where the ammonia is separated by a polytetrafluoroethylene membrane distillation device, and the electrolyte is recycled. The anode outlet is connected to a PTFE membrane deoxygenation device to discharge the generated oxygen, and the remaining electrolyte is recycled.

[0062] The system ran continuously for 120 hours. Online monitoring data showed that the ammonia yield of the four microreactors remained highly consistent, with an average ammonia yield stabilizing at 1.8 × 10⁻⁶ per square centimeter per hour. -10 The average Faraday efficiency remained at approximately 34%. During operation, the intelligent control system automatically fine-tuned the nitrogen flow rate several times within the standard range of 5 to 8 ml per minute based on slight fluctuations in the spectral signal to maintain optimal performance. After the experiment, disassembly and inspection revealed that the ceramic electrode structure was intact and there was no significant catalyst detachment.

[0064] Comparative example:

[0065] A comparative cathode was prepared by replacing the cathode substrate in Example 1 with commercial carbon paper of the same diameter, using the exact same impregnation and reduction process, and loading the same mass of bismuth catalyst.

[0067] The cathodes prepared in the first step of Examples 1-3 and the control cathode prepared in the comparative example were tested in a conventional H-type electrolytic cell. The electrolyte was a 0.1 mol / L lithium sulfate solution, the counter electrode was a platinum sheet, and the reference electrode was a saturated calomel electrode. The reaction was carried out for 2 hours under the condition of a cathode potential of -0.55 V (relative to the reversible hydrogen electrode) and continuous nitrogen gas flow. The ammonia concentration in the liquid phase was determined by the indophenol blue method, and the ammonia yield and Faraday efficiency were calculated. The ammonia yield was calculated as the amount of ammonia produced per square centimeter of electrode area per hour. The results are shown in Table 1:

[0068]

[0069] As can be seen from the above, the cathode of the present invention has a yield of ammonia and a Faraday efficiency that are more than 5 times that of the comparative cathode, demonstrating the unique advantages of the SiC-BN composite ceramic substrate in providing more active sites, enhancing mass transfer, and stabilizing the catalyst.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A microreactor for electrochemical ammonia synthesis, characterized in that: The microreactor is a sandwich structure with a membrane electrode assembly as its core, including the membrane electrode assembly and two flow field plates. The flow field plates form a cathode reaction chamber and an anode reaction chamber with the cathode and anode of the membrane electrode assembly, respectively. It also includes a temperature control component that works in conjunction with the membrane electrode assembly and the flow field plates. The membrane electrode assembly includes a sheet-like cathode and anode, and a proton exchange membrane sandwiched between the cathode and anode. The cathode includes a substrate and a nitrogen reduction electrocatalyst supported on the surface of the substrate. The substrate is a porous silicon carbide-hexagonal boron nitride composite ceramic material.

2. The microreactor for electrochemical ammonia synthesis as described in claim 1, characterized in that, The substrate is prepared by the following method: silicon carbide powder, flake-shaped hexagonal boron nitride powder, and a composite sintering aid composed of aluminum nitride and yttrium oxide are mixed and slurried, and a green body with a three-dimensional interconnected pore structure is formed by direct writing 3D printing technology; the green body is subjected to controlled pre-oxidation treatment in an air atmosphere; finally, it undergoes two-step reaction sintering under a protective atmosphere, including a liquid phase generation stage and a high-temperature densification stage, to obtain a dense and conductive porous ceramic material matrix.

3. The microreactor for electrochemical ammonia synthesis as described in claim 1, characterized in that: The nitrogen reduction electrocatalyst includes bismuth nanocatalysts, iron single-atom catalysts, or ruthenium-based nanoclusters, which are loaded onto the pores and surface of a ceramic substrate by electrodeposition or impregnation calcination.

4. The microreactor for electrochemical ammonia synthesis as described in claim 1, characterized in that: The flow field plate includes a cathode flow field plate and an anode flow field plate. The cathode flow field plate has flow channels etched on the cathode side, thereby forming a cathode reaction chamber with the cathode. The anode flow field plate has flow channels etched on the anode side, thereby forming an anode reaction chamber with the anode. The cathode flow field plate has a nitrogen and electrolyte common inlet and a product outlet connected to the flow channels on the cathode side away from the cathode. The anode flow field plate has an electrolyte inlet and an electrolyte outlet connected to the flow channels on the anode side away from the anode.

5. The microreactor for electrochemical ammonia synthesis as described in claim 1, characterized in that: The temperature control component includes an independent cooling / heating channel integrated inside the flow field plate. The cooling / heating channel is connected to an external constant temperature circulation device, and precise temperature control of the reaction zone is achieved through fluid medium circulation.

6. The microreactor for electrochemical ammonia synthesis as described in claim 1, characterized in that: The anode is a titanium felt or carbon paper coated with an oxygen evolution catalyst.

7. An electrochemical ammonia synthesis system using the microreactor according to any one of claims 1-6, characterized in that, In addition to microreactors, it also includes: A gas supply unit, which is connected to the flow field plate of the microreactor, is used to supply nitrogen feedstock to the microreactor; An electrolyte circulation unit, which is connected to the flow field plate of the microreactor, is used to provide electrolyte and output the ammonia generated and mixed in the electrolyte; A power source, electrically connected to the microreactor, is used to provide a potential difference between the cathode and anode of the membrane electrode assembly. The detection unit is connected to the output terminal of the electrolyte circulation unit and is used to detect the ammonia concentration in the electrolyte. The product separation unit is connected to the output terminal of the electrolyte circulation unit to achieve the separation of ammonia and electrolyte; The intelligent control unit includes a microprocessor, which is electrically connected to the microreactor, gas supply unit, electrolyte circulation unit, power supply, product separation unit, and detection unit to control the operation of the entire system.

8. A method for electrochemically synthesizing ammonia using the system as described in claim 7, characterized in that, Includes the following steps: S1. System preparation and activation: Electrolyte is introduced into the anode reaction chamber and the cathode chamber respectively, and high-purity nitrogen gas is introduced into the cathode reaction chamber. An initial voltage of 0.1V-0.3V is applied for electrochemical activation. S2. Continuous reaction process: The reaction temperature is maintained at 30℃-60℃ by the temperature control component, and the absolute pressure of the system is maintained at 0.1MPa-0.2MPa. High-purity nitrogen gas saturated with electrolyte is continuously introduced into the cathode reaction chamber to form a gas-liquid two-phase flow. Electrolyte or pure water is introduced into the anode chamber. A DC voltage is applied between the cathode and the anode, and the cathode potential is controlled between -0.4V and -0.8V relative to the reversible hydrogen electrode. S3. Online monitoring and optimization control: The ammonia concentration in the cathode outlet liquid is monitored in real time by the detection unit. The intelligent control unit automatically adjusts the applied voltage or nitrogen flow rate according to the measured instantaneous ammonia yield, so that the system always operates near the highest Faraday efficiency range. S4. Product Collection: The ammonia-containing cathode outlet liquid is guided to the product separation unit, where high-purity ammonia products are recovered through membrane separation, distillation, or gas stripping.

9. The microfluidic electrochemical method for ammonia synthesis as described in claim 8, characterized in that: The electrolyte includes one of dilute sulfuric acid, lithium sulfate, or lithium chloride solution.

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