Plasma-assisted green ammonia synthesis system capable of self-maintaining operation

Abstract

A plasma-assisted green ammonia synthesis system capable of self-maintaining operation belongs to the field of chemical engineering and electrochemistry and comprises an air pretreatment module, an ammonia electricity synthesis module and a water supply device. The air pretreatment module is driven by a high-voltage power supply, adopts a dielectric barrier discharge form and is used for efficiently activating nitrogen and oxygen in air, and airflow rich in active nitrogen species is input into an absorption buffer chamber of the ammonia electricity synthesis module through a gas conveying pipeline, is converted into NOx <-> and then enters an electrolysis cathode chamber to be reduced into ammonia; the chambers are accurately separated through anion exchange membranes and cation exchange membranes, so that selective transmission of ions and efficient separation of materials are realized; and the water supply device continuously supplies water to the electrolytic anode chamber to provide a water source required by ammonia synthesis. The method is simple and convenient to operate, supports distributed deployment, can realize continuous ammonia electricity synthesis by taking air and water as raw materials without any electrolyte maintenance, has the remarkable advantages of simple process, stable operation, environment friendliness and the like, and provides a brand new solution for green ammonia synthesis.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical industry and electrochemistry, and relates to a self-sustaining operation plasma-assisted green ammonia synthesis system, in particular to a self-sustaining operation plasma-assisted green ammonia synthesis system without electrolyte replacement and using air and water as raw materials. BACKGROUND

[0002] Ammonia (NH3) is considered as an ideal hydrogen storage medium and a promising zero-carbon fuel due to its high hydrogen content and zero carbon emission during combustion. Currently, ammonia synthesis on an industrial scale mainly relies on the Haber-Bosch process, which needs to be carried out under high temperature and high pressure (400-500℃, 150-250bar), and its energy consumption accounts for about 2% of the global energy consumption and contributes to 1.4% of the global carbon dioxide emissions. The high carbon emission characteristics of the traditional ammonia synthesis process urgently need to be green transformed. The electrochemical nitrogen reduction reaction (NRR) driven by green electricity can realize sustainable green ammonia synthesis at room temperature and pressure, and is considered as a promising alternative route. However, this technology still faces two major challenges: one is the high chemical inertness of nitrogen molecules (the dissociation energy of N≡N bond is as high as 946kJ·mol⁻¹), which leads to difficult activation; the other is the easy occurrence of the competitive hydrogen evolution reaction (HER) during the reaction process, which causes low faradic efficiency and ammonia yield. These problems seriously restrict the practical application feasibility of electrochemical synthesis of ammonia.

[0003] The plasma technology can efficiently activate inert nitrogen molecules, so the plasma-assisted green ammonia synthesis technology has been considered as a way to produce green ammonia in recent years. This method usually includes two processes: activation of nitrogen molecules by plasma and electrochemical reduction of nitrogen oxides. Amal et al. first confirmed the feasibility of this method, but the ammonia yield and selectivity were significantly limited by the interference of residual oxygen in the air. To solve the problem of oxygen interference, Qiao et al. proposed an intermittent plasma-assisted ammonia electro-synthesis method, which realized effective removal of residual oxygen in the electrochemical process, and finally obtained high ammonia yield and selectivity. For example, a device and method for synthesizing ammonia by coupling electrocatalysis based on aeration nanosecond pulse discharge nitrogen fixation are provided in Chinese invention patent (application number 202211234607.7), a nanosecond pulse power is used to excite spark discharge to generate plasma rich in nitrogen oxides (NO x ) from air, and an aqueous solution mainly containing HNO x is obtained after 30 minutes of discharge; then an alkaline substance is added as a cathode electrolyte, and an electrochemical platform is used to carry out electrocatalytic reaction in an H-type electrolytic cell for 60 minutes to synthesize ammonia. A modified metal oxide catalyst and a corresponding plasma-coupled electrocatalytic ammonia synthesis system are provided in Chinese invention patent (application number 202510047505.1), which first generates NO x, the obtained absorption solution is used as a cathode solution to perform electrocatalytic synthesis of ammonia in an H-type electrolytic cell, and a cobalt oxide catalyst modified by plasma treatment is used as the cathode. The core of the intermittent technical route is to decompose the synthesis of green ammonia into two relatively independent stages in time or space: in the first stage, the high energy characteristics of the plasma technology are used to dissociate and oxidize inert nitrogen (N2) molecules to generate nitrogen oxides (such as NO, NO2, etc.), and the nitrogen oxides are absorbed and converted into nitrate or nitrite (NO x - ) by using an absorbent, thereby avoiding the problem of oxygen interference to some extent; in the second stage, the generated nitrate or nitrite is used as a precursor, and the target product ammonia is selectively reduced from the nitrate or nitrite by a nitrate or nitrite reduction reaction (NO x - RR) in an electrochemical process. Our latest research further optimizes the intermittent green ammonia synthesis process from the micro level and develops an effective oxygen removal process for the electrochemical process (an additional argon flushing step is introduced), thereby achieving a high ammonia yield of 40 nmol s -1 cm -2 , and a Faraday efficiency of about 90 %.

[0004] Although the intermittent process has shown high yield and Faraday efficiency in the plasma-assisted green ammonia synthesis, its running stability is still significantly affected by the frequent start-stop operation. In addition, the process needs to be regularly supplemented with an absorbent or replaced with an electrolyte solution (usually potassium hydroxide solution), which significantly increases the operating cost, and about three tons of potassium hydroxide are consumed for the synthesis of one ton of ammonia. From the perspective of practical application and economy, it is crucial to integrate and optimize the current multi-step, intermittent operation mode into a one-step continuous synthesis system to promote the industrial application of the technology. To achieve continuous, efficient and stable green ammonia synthesis, the following problems need to be solved: (1) how to realize efficient and directional transmission of nitrogen oxides from the plasma zone to the electrochemical reduction unit without external separation units; (2) how to maintain the stability of the system, especially the electrolyte, under the requirements of high current density and long-term operation, and avoid frequent replacement of the electrolyte, so as to improve the durability and economy of the overall process. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a self-sustaining operation plasma-assisted green ammonia synthesis system which uses air and water as raw materials and does not need to replace the electrolyte during production operation. The plasma-assisted green ammonia synthesis system is simple to operate, has strong adaptability, supports dispersed and integrated continuous synthesis of green ammonia, and has the characteristics of simple process and high running stability in actual manufacturing.

[0006] To achieve the above object, the technical scheme adopted by the present application is that:

[0007] A self-sustaining operation of plasma assisted green ammonia synthesis system, the plasma assisted green ammonia synthesis system includes air pretreatment module, ammonia electrolysis module 6 and water supply device 17;The air pretreatment module is mainly used for efficient activation of nitrogen and oxygen in air, and the active nitrogen species rich gas flow is input into the absorption buffer chamber 7 of ammonia electrolysis module 6 through gas delivery pipeline, wherein the active nitrogen species is efficiently absorbed by the absorbent in the absorption buffer chamber 7 and converted into NO x - After that, selectively permeate anion exchange membrane 11 into electrolytic cathode chamber 12, reduce to ammonia under the catalysis of cathode electrode 15;The water supply device 17 supplies water to the electrolytic anode chamber 14 through the liquid delivery pipeline, provides the water source required for ammonia synthesis. Specifically:

[0008] The air pretreatment module is plasma air activation device 1, driven by high voltage power supply 4, adopts dielectric barrier discharge form, forms discharge area. The plasma air activation device 1 is connected with the absorption buffer chamber 7 of ammonia electrolysis module 6 through the gas delivery pipeline equipped with air control valve 5.

[0009] The ammonia electrolysis module 6 adopts double membrane three chamber structure, including gas inlet distribution unit 8 and reactor shell. The reactor shell is separated into absorption buffer chamber 7, electrolytic cathode chamber 12 and electrolytic anode chamber 14, wherein the electrolytic cathode chamber 12 is provided with cathode electrode 15 containing catalyst, and the electrolytic anode chamber 14 is provided with anode electrode 16. The absorption buffer chamber 7 and the electrolytic cathode chamber 12 are separated by anion exchange membrane 11, and the electrolytic cathode chamber 12 and the electrolytic anode chamber 14 are separated by cation exchange membrane 13. The gas inlet distribution unit 8 is integrated on the reactor shell and in fluid communication with the absorption buffer chamber 7, mainly used for uniformly distributing the introduced active nitrogen species gas flow in the absorbent in the absorption buffer chamber 7. The absorption buffer chamber 7 is used for receiving the active nitrogen species delivered by the air pretreatment module, and then the active nitrogen species diffuses to the electrolytic cathode chamber 12 through the anion exchange membrane 11, and carries out electrochemical reduction reaction in the presence of cathode electrode 15 containing catalyst and electrolyte, to generate ammonia;The anode electrode 16 in the electrolytic anode chamber 14 receives electrons from the cathode electrode 15, catalyzes oxygen evolution reaction, and thus forms an electrolysis closed loop with the cathode electrode 15 in the electrolytic cathode chamber 12, to maintain the continuous progress of ammonia synthesis process.

[0010] The water supply device 17 is provided with water control valve 18 and water tank 19, the water tank 19 is communicated with electrolytic anode chamber 14 through liquid delivery pipeline, and water control valve 18 is arranged on the liquid delivery pipeline. The water supply device 17 provides the water source required for ammonia synthesis.

[0011] Further, the plasma air activation device 1 adopts dielectric barrier discharge, including outer electrode 2 and inner electrode 3, the discharge area is formed between the coaxially arranged outer electrode 2 and inner electrode 3, and the surface of the inner electrode 3 is covered with an insulating medium layer. Air enters from one end of the plasma air activation device 1, passes through the gap between the coaxial outer electrode 2 and the inner electrode 3, and is transported to the absorption buffer chamber 7 of the ammonia electro-synthesis module 6 after plasma activation in the discharge area. Specifically:

[0012] The outer electrode 2 is a quartz tube with an outer diameter of 25-50 mm, an inner diameter of 20-40 mm, and a length of 350-400 mm; the inner electrode 3 is a quartz double dielectric electrode with a diameter of 8-20 mm; the plasma discharge width is 150-200 mm; the outer electrode 2 is connected to a high-voltage power supply 4, and the inner electrode 3 is grounded to maintain a 0V safety voltage.

[0013] Further, the plasma air activation device 1 can operate in continuous mode.

[0014] Further, the plasma air activation device 1 is a remote plasma source, which is connected to the absorption buffer chamber 7 of the ammonia electro-synthesis module 6 through a gas delivery pipeline.

[0015] Further, the plasma air activation device 1 and the gas delivery pipeline are connected through a pneumatic joint to install an air control valve 5, and the air flow rate is controlled through the air control valve 5.

[0016] Further, in the ammonia electro-synthesis module 6, the material of the reactor shell is an insulator, and the structure is semi-closed. The internal chamber of the reactor shell is mainly used to accommodate electrolyte and maintain a controllable reaction environment.

[0017] Further, the reactor shell includes an observation window or an optical port, which mainly provides an observation window required for in-situ optical monitoring or spectral analysis to monitor the concentration or type of active nitrogen species.

[0018] Further, the reactor shell further includes a plurality of interfaces integrated on the shell, which are standardized designs and can be directly switched to connect to different types of remote plasma sources.

[0019] Further, the air inlet distribution unit 8 includes a gas diffusion layer, a pressure regulating valve, and a sealing structure. The gas diffusion layer is used to disperse the active nitrogen species gas flow into micro-nano bubbles, and then uniformly disperse them in the absorbent; the pressure regulating valve and the sealing structure are used to maintain the pressure balance between the air pretreatment module and the ammonia electro-synthesis module.

[0020] Further, the gas diffusion layer can also be a device that can disperse gas flow, such as an ejector or a multi-hole distributor.

[0021] Further, the air intake distribution unit 8 is arranged below, beside or around the absorption buffer chamber 7.

[0022] Further, the absorption buffer chamber 7 is provided with a tail gas discharge interface 9 at the top, which is connected to a tail gas treatment device 10 for recycling or harmless disposal of the unabsorbed nitrogen active species.

[0023] Further, the absorption agent in the absorption buffer chamber 7 is an alkaline solution containing potassium hydroxide, sodium hydroxide or a mixture of the two. When the alkaline solution is one alkaline solution, its concentration is 0.01-6 mol L -1 When the alkaline solution is a mixture of potassium hydroxide and sodium hydroxide, the molar ratio of potassium hydroxide to sodium hydroxide is 1:1, and the concentration of potassium hydroxide is 0.01-3 mol L -1 .

[0024] Further, the cathode electrode 15 adopts an integrated catalyst structure, which can be one of copper, iron, cobalt, nickel, palladium, or an alloy, oxide and carbon-based composite material containing the above-mentioned metals, for catalyzing the electro-reduction reaction of nitrate or nitrite.

[0025] Further, the anode electrode 16 is also an integrated catalyst structure, which includes one of iridium oxide, ruthenium oxide and platinum for catalyzing the oxygen evolution reaction (OER).

[0026] Further, the electrolytic anode chamber 14 is provided with a water inlet connected to the water tank 19 of the water supply device 17 for inputting water required for ammonia synthesis from the water tank into the system.

[0027] Further, the plasma-assisted green ammonia synthesis system further comprises an input control unit 20 connected to the plasma air activation device 1, which includes a first sensor and an input control system. The first sensor is arranged in the absorption buffer chamber 7 for monitoring the change of NO x - concentration therein and feeding back the electrical signal to the input control system through the control line. The input control system is connected to the high-voltage power supply 4 of the air pretreatment module and the air control valve 5 through the control line, respectively, to receive the NO x - concentration change signal from the first sensor and adjust at least one of the power of the plasma air activation device 1, the air input flow rate or the pressure according to the target ammonia production capacity to make the NO x - generation rate and the NO x - generation rate consistent.x - The consumption rate reaches equilibrium; wherein X = 2, 3, respectively, represent nitrate and nitrite.

[0028] Further, the plasma-assisted green ammonia synthesis system further comprises an output control unit 21 connected with the ammonia electro-synthesis module 6, the output control unit 21 comprising a second sensor and an output control system; the second sensor is arranged in the electrolysis cathode chamber 12, and is used for monitoring the NO x - ion, ammonia concentration change; the output control system is connected with the power supply of the ammonia electro-synthesis module 6 through a control line, and adjusts the cathode potential or current based on the feedback of the second sensor, so as to adapt to different NO x - generation rates, and further realize the regulation of ammonia yield and energy production.

[0029] It should be noted that in the system, the NO x - consumption rate, ammonia generation rate and ammonia energy production value are actually the same, and different terms are used in the description for the convenience of understanding.

[0030] The working principle of the present application is as follows: air enters the plasma air activation device 1 driven by the high-voltage power supply 4, is activated, and is uniformly dispersed into the absorption buffer chamber 7 of the ammonia electro-synthesis module 6 through the air inlet distribution unit 8; the active nitrogen species in the gas flow is efficiently absorbed by the absorbent and converted into nitrate or nitrite ions, and selectively permeates the anion exchange membrane 11 from the absorption buffer chamber 7 into the electrolysis cathode chamber 12, and is catalytically synthesized into ammonia by the cathode electrode 15; at the same time, the alkaline substances generated by the ammonia synthesis reaction in the electrolysis cathode chamber 12 pass through the anion exchange membrane 11 from the electrolysis cathode chamber 12 into the absorption buffer chamber 7 to supplement the alkaline substances consumed in the operation, and maintain the continuous ammonia synthesis of the system.

[0031] The present application has the following beneficial effects:

[0032] (1) The plasma-assisted green ammonia synthesis system designed in the present application is integrated and assembled, and is convenient to manufacture; the process is simple and the yield is high in actual production. The present application adopts a self-sustaining integrated design scheme for the drawbacks of the intermittent plasma-assisted ammonia synthesis path, and improves the system stability.

[0033] (2) The plasma-assisted green ammonia synthesis system is driven by green electricity, realizes zero carbon emission, and only air and water will be continuously introduced into the system during production operation, without the need for regular replacement of electrolyte. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1The flow chart of the self-sustained operation of the plasma-assisted green ammonia synthesis designed for the present application;

[0035] Figure 2 The structural schematic diagram of the self-sustained operation of the plasma-assisted green ammonia synthesis system designed for the present application;

[0036] Figure 3 The structural schematic diagram of the intermittent plasma-assisted green ammonia synthesis system as a comparison;

[0037] Figure 4 、 Figure 5 、 Figure 6 The performance comparison chart of different plasma-assisted green ammonia synthesis devices;

[0038] Figure 7 The data chart of the plasma activation conversion capacity of Example 1 varying with the applied power;

[0039] Figure 8 The data chart of the electrolysis conversion capacity of Example 1 varying with the applied current;

[0040] In the figure, 1 is a plasma air activation device, 2 is an outer electrode, 3 is an inner electrode, 4 is a high-voltage power supply, 5 is an air control valve, 6 is an ammonia electrolysis module, 7 is an absorption buffer chamber, 8 is an air inlet distribution unit, 9 is a tail gas exhaust interface, 10 is a tail gas treatment device, 11 is an anion exchange membrane, 12 is an electrolysis cathode chamber, 13 is a cation exchange membrane, 14 is an electrolysis anode chamber, 15 is a cathode electrode, 16 is an anode electrode, 17 is a water supply device, 18 is a water control valve, 19 is a water tank, 20 is an input control unit, 21 is an output control unit; 22 is a lye absorption device, 23 is an air inlet, 24 is an air outlet, 25 is a liquid inlet, 26 is a liquid outlet, 27 is an absorbent storage tank, 28 is an absorption liquid storage tank, and 29 is an electrolysis device. DETAILED DESCRIPTION

[0041] The present application is further described below by means of the accompanying drawings and examples.

[0042] Example 1

[0043] Figure 1 The schematic diagram of the self-sustained operation of the plasma-assisted green ammonia synthesis system; the present application provides a plasma-assisted green ammonia synthesis system which can be self-sustained without electrolyte replacement and uses air and water as raw materials, comprising an air pretreatment module, an ammonia electrolysis module 6, and a water supply device;

[0044] As Figure 2As shown, the air pretreatment module includes a plasma air activation device 1. The plasma air activation device 1 uses dielectric barrier discharge. The outer electrode 2 is a quartz tube with an outer diameter of 25mm, an inner diameter of 20mm, and a length of 355mm. The inner electrode 3 is a quartz double dielectric electrode with a diameter of 8mm. The plasma discharge width is 150mm, which is the discharge area of ​​the plasma air activation device 1. The outer electrode 2 is connected to a high-voltage power supply 4, and the inner electrode 3 is grounded to maintain a safe voltage of 0V. The plasma air activation device 1 is connected to the absorption buffer chamber 7 of the ammonia electrosynthesis module 6 via a gas delivery pipeline equipped with an air control valve 5. The bottom side chamber wall of the absorption buffer chamber 7 is equipped with an air inlet distribution unit 8 and an exhaust gas outlet 9. The air inlet distribution unit 8 adopts a jet operation mode. The exhaust gas outlet 9 is located on the top chamber wall of the absorption buffer chamber and is connected to the exhaust gas treatment device 10 through a gas delivery pipeline at the top of the absorption buffer chamber. The absorption buffer chamber 7 is connected to the electrolysis cathode chamber 12 via anion exchange membrane 11; the electrolysis cathode chamber 12 is connected to the electrolysis anode chamber 14 via a cation exchange membrane 13. The electrolysis chamber includes a catalytic NO catalyst. x - The cathode 15 of the RR and the anode 16 of the catalytic OER are described. The electrolytic anode chamber 14 is connected to a water supply device 17; the water supply device 17 is connected to a water tank 19 via a water control valve 18. The plasma-assisted green ammonia synthesis system is equipped with an input control unit 20 and an output control unit 21 with detection devices.

[0045] Based on the current density required for industrial-grade electrosynthesis of ammonia (350 mA cm⁻¹) -2 The cathode electrode 15 in the electrolytic cathode chamber 12 is a copper-palladium bimetallic catalyst grown on nickel foam and held by platinum sheet electrode clips. The preparation process is as follows:

[0046] (1) Cut a suitable amount of commercial-grade nickel foam and clean it sequentially with acetone, ethanol, and 100 mM dilute hydrochloric acid. Use the cleaned nickel foam as the working electrode and a platinum sheet as the counter electrode, and electrolyze it in an acidic electrolyte at 100 mA cm⁻¹. -2 Electrodeposition was performed for 300 seconds at a current density. The acidic electrolyte consisted of a bimetallic aqueous solution of 50 mM soluble copper salt and soluble palladium salt (with a copper to palladium molar ratio of 49:1) and 15 mM sodium citrate.

[0047] (2) After the reaction is complete, wash several times with ethanol and ultrapure water and vacuum dry to obtain CuPd bimetallic electrode precursor;

[0048] (3) The synthesized CuPd bimetallic electrode precursor was then immersed in a 1 M KOH solution as the cathode, and a platinum sheet was used as the counter electrode at 350 mA cm⁻¹. -2Under the specified conditions, electroactivation was performed for 1 hour to obtain a copper-palladium bimetallic catalyst grown on nickel foam. After the reaction, the catalyst was washed several times with ethanol and ultrapure water, and then dried in a vacuum environment at 60 °C for 12 hours before use. Both electrodeposition and electroactivation processes used a dual-electrode single-electrolysis cell. The acidic electrolyte volume was 100 mL, containing 50 mM soluble copper and palladium salts, specifically 0.672 g of copper chloride and 0.018 g of palladium chloride. The pH of the electrolyte was adjusted to 1 using hydrochloric acid.

[0049] The anode electrode 16 of the electrolytic anode chamber 14 uses a commercial platinum sheet (working electrode area 1*1 cm). 2 ).

[0050] The method of using the self-sustaining plasma-assisted green ammonia synthesis system provided in Example 1 above includes the following steps:

[0051] (1) According to Figure 2 The connected reaction apparatus is shown, with a copper-palladium bimetallic catalyst (working electrode area 1*1 cm) fixed on a platinum electrode clamp grown on nickel foam. 2 );

[0052] (2) 1 M KOH solution is pre-added to the absorption buffer chamber 7, the electrolytic cathode chamber 12 and the electrolytic anode chamber 14 as absorbent and electrolyte;

[0053] (3) Open the air control valve 5, set the air flow rate, and ventilate for a period of time. After the gas and liquid flow inside the system are mixed and balanced, turn on the high voltage power supply 4 of the plasma air activation device 1 and adjust the plasma power applied. At the same time, adjust the electrolysis input voltage and current. Observe the material concentration in the absorption buffer chamber 7 and the electrolysis cathode chamber 12. After the readings stabilize, adjust the water inlet flow rate in the electrolysis anode chamber 14. Then set the parameters of the input control unit 20 and the output control unit 21, and the system enters the self-sustaining operation state.

[0054] (4) Collect cathodic liquid for product detection.

[0055] The plasma power applied was 61 W, and the air flow rate was 200 mL / min. -1 The electrolysis input current is 350 mA / cm. -2 When the plasma-assisted ammonia synthesis system is in steady state, the anode influent flow rate is 0.9 mL / min. -1 The material concentrations throughout the system remain constant, and the ammonia synthesis rate can reach 34 mg / h. -1 .

[0056] Comparative Example 1

[0057] Figure 3is the device diagram of intermittent plasma assisted green ammonia synthesis; the device mainly comprises a plasma air activation device 1, an alkali liquor absorption device 22 and an electrolysis device 29. The plasma air activation device 1 adopts dielectric barrier discharge, the outer electrode 2 is a quartz tube with an outer diameter of 25 mm, an inner diameter of 20 mm and a length of 355 mm; the inner electrode 3 is a quartz double dielectric electrode with a diameter of 8 mm; the plasma discharge width is 150 mm. The outer electrode 2 is connected to a high-voltage power supply 4, and the inner electrode 3 is grounded to maintain a 0V safety voltage. The plasma air activation device 1 is connected to the alkali liquor absorption device 22 through a gas delivery pipeline equipped with an air control valve 5; the alkali liquor absorption tank 22 comprises an air inlet 23, an air outlet 24, a liquid inlet 25 and a liquid outlet 26; the air inlet 23 is connected to the plasma air activation device 1 through a gas channel arranged at the bottom of the alkali liquor absorption device; the air outlet 24 is arranged on the chamber wall at the top of the alkali liquor absorption tank and is connected to a tail gas treatment device 10 through a gas channel arranged at the top of the alkali liquor absorption tank; the liquid inlet 25 is connected to the absorbent storage tank 27 through a liquid channel; and the liquid outlet 26 is connected to the absorption liquid storage tank 28 through a liquid channel. The electrolysis device 29 is an H-shaped electrolytic cell comprising a cathode 15, an anode 16 and a cation exchange membrane 13.

[0058] To ensure the rigor of the comparative experiment, the intermittent device used in the present comparative example 1, including the plasma air activation device 1, the air control valve 5, the tail gas treatment device 10, the cathode electrode 15, the anode electrode 16 and the cation exchange membrane 13, is consistent with the corresponding components used in the embodiment 1 of the present application; then the intermittent plasma assisted green ammonia synthesis device provided by the above comparative example 1 comprises the following steps:

[0059] (1) according to the connection reaction device shown in Figure 3 , the platinum electrode is fixed on the copper-palladium bimetallic catalyst (working electrode area 1*1 cm 2 ) grown on the foam nickel;

[0060] (2) check the solution residual amount in the absorbent storage tank 27, set the absorbent flow rate; after a period of time, open the air control valve 5, set the air gas flow rate, first ventilate for a period of time, and after the system internal gas-liquid flow is mixed and balanced, open the high-voltage power supply 4 of the plasma air activation device 1, and adjust the plasma applied power;

[0061] (3) collect the absorption liquid in the absorption liquid storage tank 28, supplement the alkaline substance, and remove the residual oxygen contained in the absorption liquid by using the argon gas purging method;

[0062] (4) add the treated absorption liquid as the cathode electrolyte into the electrolysis device 29; at the same time, add 1 M KOH solution as the anode electrolyte into the electrolysis device 29; adjust the electrolysis input voltage and current.

[0063] (5) Collect cathodic liquid for product detection.

[0064] The absorbent was a 1 M KOH solution; the plasma power was 61 W, and the air flow rate was 200 mL / min. -1 The electrolysis current applied was 350 mA cm⁻¹ -2 ;

[0065] Performance tests of Example 1 and Comparative Example 1:

[0066] The batch process achieves high ammonia yield and Faraday efficiency by decomposing the green ammonia synthesis reaction into two relatively independent stages in time or space and using argon purging to remove residual oxygen from the absorbent. However, as... Figure 4 , Figure 5 , Figure 6 As shown, during this process, the cathode electrolyte OH in the electrolysis device 29... - The sharp increase in ion content indicates that the reduction reaction of nitrate or nitrite is accompanied by the formation of hydroxide byproducts. From a thermodynamic perspective, the continuous accumulation of hydroxide ions will severely inhibit the ammonia synthesis reaction, requiring frequent replacement of the cathode electrolyte; at the same time, the alkaline absorption process consumes a large amount of hydroxide ions, requiring continuous replenishment of alkaline substances. These problems collectively limit the practical feasibility of the intermittent plasma-assisted green ammonia synthesis device. In contrast, the self-sustaining plasma-assisted green ammonia synthesis system provided in Example 1 of this invention can maintain a high ammonia yield and high Faradaic efficiency for a long time while keeping the pH value of the cathode electrolyte basically stable, overcoming the shortcomings of the intermittent plasma-assisted green ammonia synthesis device in Comparative Example 1.

[0067] The above examples illustrate that the self-sustaining plasma-assisted green ammonia synthesis system of this invention uses plasma technology to activate air to nitrogen oxides, utilizes alkaline solution to absorb nitrogen oxides and convert them into nitrate or nitrite ions, and replenishes the alkaline substances consumed in the absorption operation based on the alkaline substances generated by the reduction reaction of nitrate or nitrite ions during electrolysis, thus maintaining continuous ammonia synthesis. By rationally controlling the airflow rate, plasma input power, electrolysis applied current, and equipment scale, various indicators required for industrial-grade green ammonia production can be achieved. In addition, the system is powered by renewable energy, achieving zero carbon emissions, and only air and water are continuously pumped into the system to produce ammonia, without the need for periodic electrolyte replacement.

[0068] The above embodiments are merely examples of implementation methods of the present invention; for those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A self-sustained operation plasma assisted green ammonia synthesis system, characterized by, The plasma-assisted green ammonia synthesis system comprises an air pretreatment module, an ammonia electrolysis module (6) and a water supply device (17); The air pre-treatment module is a plasma air activation device (1) driven by a high-voltage power supply (4) in a dielectric barrier discharge form to form a discharge area for efficiently activating nitrogen and oxygen in the air, and inputting the gas flow rich in active nitrogen species into an absorption buffer chamber (7) of an ammonia electro-synthesis module (6) through a gas delivery pipeline, wherein the active nitrogen species is efficiently absorbed by an absorbent in the absorption buffer chamber (7) and converted into NO x - After that, the ammonia is selectively transmitted through an anion exchange membrane (11) into an electrolysis cathode chamber (12) and reduced into ammonia under the catalysis of a cathode electrode (15); and the water supply device (17) continuously supplies water to the electrolysis anode chamber (14) through a liquid delivery pipeline to provide a water source required for ammonia synthesis.

2. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 1, wherein, The ammonia electrolysis module (6) adopts a double-membrane three-chamber structure, comprising an air inlet distribution unit (8) and a reactor shell; the reactor shell is internally partitioned into an absorption buffer chamber (7), an electrolysis cathode chamber (12) and an electrolysis anode chamber (14), wherein the electrolysis cathode chamber (12) is provided with a cathode electrode (15) containing a catalyst, and the electrolysis anode chamber (14) is provided with an anode electrode (16); The absorption buffer chamber (7) and the electrolysis cathode chamber (12) are separated by an anion exchange membrane (11), and the electrolysis cathode chamber (12) and the electrolysis anode chamber (14) are separated by a cation exchange membrane (13); the air inlet distribution unit (8) is integrated on the reactor shell and in fluid communication with the absorption buffer chamber (7) to uniformly distribute the introduced active nitrogen species gas flow in the absorbent in the absorption buffer chamber (7); the absorption buffer chamber (7) is used for receiving the active nitrogen species delivered by the air pretreatment module, and the active nitrogen species diffuses to the electrolysis cathode chamber (12) through the anion exchange membrane (11) to generate ammonia; the anode electrode (16) and the cathode electrode (15) jointly form an electrolysis closed loop to maintain the ammonia synthesis process.

3. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 2, wherein, The water supply device (17) is provided with a water control valve (18) and a water tank (19), the water tank (19) is in communication with the electrolysis anode chamber (14) through a liquid delivery pipeline, and the liquid delivery pipeline is provided with the water control valve (18).

4. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 3, wherein, The plasma air activation device (1) is in communication with the absorption buffer chamber (7) of the ammonia electrolysis module (6) through a gas delivery pipeline provided with an air control valve (5), and the air flow rate is controlled through the air control valve (5).

5. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 4, wherein, The plasma air activation device (1) specifically comprises: The plasma air activation device (1) is in communication with the absorption buffer chamber (7) of the ammonia electrolysis module (6) through a gas delivery pipeline provided with an air control valve (5), and the air flow rate is controlled through the air control valve (5); The plasma air activation device (1) adopts dielectric barrier discharge, comprising an outer electrode (2) and an inner electrode (3), and the discharge region is formed between the coaxially arranged outer electrode (2) and the inner electrode (3), and the surface of the inner electrode (3) is covered with an insulating medium layer; The outer electrode (2) is a quartz tube with an outer diameter of 25-50 mm, an inner diameter of 20-40 mm and a length of 350-400 mm; the inner electrode (3) is a quartz double dielectric electrode with a diameter of 8-20 mm; the plasma discharge width is 150-200 mm; the outer electrode (2) is connected to a high-voltage power supply (4), and the inner electrode (3) is grounded to maintain a 0V safety voltage; The plasma air activation device (1) can operate in a continuous mode; The plasma air activation device (1) is a remote plasma source.

6. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 5, wherein, The reactor shell in the ammonia electrolysis module (6) specifically comprises: The material of the reactor shell is an insulator, and the structure is semi-closed. The reactor shell comprises an observation window or optical port for monitoring the concentration or type of active nitrogen species; The reactor shell further comprises a plurality of interfaces integrated on the shell.

7. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 6, wherein, The gas inlet distribution unit (8) comprises a gas diffusion layer, a pressure regulating valve and a sealing structure; the gas diffusion layer is used to disperse the active nitrogen species gas flow into micro-nano bubbles, so as to uniformly disperse them in the absorbent; the pressure regulating valve and the sealing structure are used to maintain the pressure balance between the air pretreatment module and the ammonia electro-synthesis module; The gas inlet distribution unit (8) is arranged below, beside or around the absorption buffer chamber (7); The absorption buffer chamber (7) is provided with a tail gas discharge interface (9) at the top, which is in communication with a tail gas treatment device (10); The absorbent in the absorption buffer chamber (7) is an alkaline solution containing potassium hydroxide, sodium hydroxide or a mixed solution of the two.

8. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 7, wherein, The cathode electrode (15) adopts an integrated catalyst structure, and the material is one of copper, iron, cobalt, nickel and palladium, or an alloy, oxide or carbon-based composite material containing the above-mentioned metals; the anode electrode (16) is an integrated catalyst structure, and the material includes one of iridium oxide, ruthenium oxide and platinum.

9. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 8, wherein, The plasma-assisted green ammonia synthesis system further comprises an input control unit (20) connected with the plasma air activation device (1), and the input control unit (20) comprises a first sensor and an input control system; The first sensor is arranged in the absorption buffer chamber (7) for monitoring the NO x - The ion concentration changes and feeds back the electric signal to the input control system through the control line; the input control system is connected with the high-voltage power supply (4) and the air control valve (5) of the air pretreatment module respectively, so as to dynamically adjust the plasma air activation device (1) to make the NO x - The generation rate is proportional to the NO x - The consumption rate reaches equilibrium.

10. A self-sustained operation plasma assisted green ammonia synthesis system according to claim 9, wherein, The plasma-assisted green ammonia synthesis system further comprises an output control unit (21) connected with the ammonia electro-synthesis module (6), and the output control unit (21) comprises a second sensor and an output control system; The second sensor is arranged in the electrolysis cathode chamber (12) for monitoring NO in the electrolysis cathode chamber (12) x - Ion, ammonia concentration change; the output control system is connected with the power supply of the ammonia electro-synthesis module (6), and based on the feedback of the second sensor, the cathode potential or current is adjusted to adapt to different NO x - Generation rate, realizing the regulation of ammonia yield and energy production; wherein X=2, 3, respectively, represents nitrate and nitrite.

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