An apparatus and method for nitrogen fixation coupling electrocatalytic ammonia synthesis based on aerated nanosecond pulsed discharge

Abstract

The present invention discloses a device and method for nitrogen fixation by aerated nanosecond pulsed discharge and electrocatalytic ammonia synthesis. The device mainly includes an aerated nitrogen fixation reactor, a nanosecond pulse power supply, an electrochemical platform, an H-type electrolytic cell, a circulating water pump, etc. First, air is introduced into the aerated nitrogen fixation reactor through an air pump, and a nanosecond pulse power supply is used to excite spark discharge to generate a rich NOx plasma. After discharging for 30 minutes, an aqueous solution rich in HNOx is obtained. The discharged solution is transferred into the H-type electrolytic cell through a circulating water pump. The invention prepares a metastable copper catalyst and performs electrocatalysis for 60 minutes using the electrochemical platform to obtain an aqueous solution rich in NH4 + . The present invention designs a device structure based on a liquid-phase aerated nitrogen fixation reactor and coupled with electrocatalytic catalysis, realizing the conversion of nitrogen in the air to HNOx by oxidation first and then to NH3 by electrocatalytic reduction, which is a new green, low-carbon and environmentally friendly way for ammonia synthesis.

Description

Technical Field

[0001] The present invention relates to a device and method for nitrogen fixation by coupling aeration nanosecond pulsed discharge with electrocatalytic ammonia synthesis, and specifically relates to a device and method for oxidizing nitrogen in air to prepare an activated aqueous solution of HNOx by liquid-phase microbubble nanosecond pulsed discharge and coupling electrocatalytic reduction to prepare ammonia synthesis. Background Art

[0002] The main nitrogen fixation methods in nature are biological nitrogen fixation, atmospheric nitrogen fixation, and artificial nitrogen fixation. Currently, the mainstream industrial nitrogen fixation method is still the Haber-Bosch method, which requires high temperature and high pressure and has very high energy consumption. The Haber process consumes 3% - 5% of the world's natural gas per year for hydrogen extraction, consumes 1% - 2% of the world's energy reserves, accounts for 87% of the energy consumption in the fertilizer industry, and emits more than 300 million tons of carbon dioxide per year, accounting for 1.5% of the total greenhouse gas emissions. In order to achieve the national goals of "carbon peak and carbon neutrality", it is urgent to develop new green and low-carbon nitrogen fixation technologies, and then promote the construction of a sustainable "nitrogen cycle" and "ammonia economy".

[0003] Patent CN100393612 introduces a method and device for nitrogen fixation in water. This device and method can preferably fix nitrogen in air in the form of nitrates and nitrites in water. However, the large bubbles of this device are generated through a limited number of aeration micropores. When the generated bubbles are too large, the specific surface area of the bubbles is small, and the NOx gas generated by the plasma dissolves less in water, so the concentration of HNOx in the activated aqueous solution is not high, and the nitrogen fixation energy efficiency is low, etc.; Patent CN102583278A first generates NOx gas through dielectric barrier discharge, and then absorbs it with H2O2 to prepare nitric acid solution, and the input frequency needs to be 9 kHz, and the AC input energy is higher than 110W. This device requires relatively high energy; Patent CN110983356B generates NO x dissolved in water to generate HNO x solution, and then uses an electrocatalytic cell to reduce the HNO x solution. However, the contact area between the plasma jet and the aqueous solution is small and the gas flow rate is large, and it takes a long time to process to generate a high concentration of NOx. At a certain power, the nitrogen fixation efficiency is relatively low, and the concentration of HNO x in the activated aqueous solution is relatively small; Patent CN110983356A synthesizes ammonia through low-temperature jet plasma activation catalysis and single-atom catalysis. The preparation of the catalyst by this method is relatively complex.

[0004] At present, the existing liquid-phase plasma nitrogen fixation method devices have the following deficiencies: (1) Liquid-phase discharge has strict requirements on power supply conditions, such as requiring relatively high energy and high voltage. (2) The currently existing gas-liquid mixed plasma discharges (such as jet plasma, sliding arc plasma) generate NOx A large amount of gas will disperse in the air, and less NOx will dissolve in water. Therefore, it is difficult to absorb the nitrogen fixation of gas-liquid mixed plasma discharge in water, that is, it is difficult to fix the NOx generated by the plasma in water, and the nitrogen fixation efficiency is low; while the dielectric barrier discharge in air has weak selectivity for NOx, and ozone is easily generated during the discharge. (3) When the existing liquid-phase discharge device forms a discharge channel between the high-voltage electrode and the ground electrode in the liquid phase, it will cause electrode corrosion and introduce more heavy metal ions (Fe 3+ 、Cu 2+ etc.). Summary of the Invention

[0005] The present invention designs a simple aeration nitrogen fixation reactor. After applying a pulsed voltage, rich NOx-activated aqueous solution can be collected by discharging in the liquid phase, and combined with electrocatalysis to prepare synthetic ammonia. Through the "air-HNO x -NH3" process, that is, first fix the nitrogen in the air in water as HNO x , and then use electrocatalysis to reduce NOx in the activated water to ammonia, which has been less studied; and the present invention designs the structure of an integrated device for preparing HNOx-activated aqueous solution and electrochemically reducing it, making the miniaturized ammonia production more convenient, fast, green and environmentally friendly.

[0006] In view of the above deficiencies, the present invention aims to propose a device and method for nitrogen fixation by aeration nanosecond pulsed discharge coupled with electrocatalytic synthesis of ammonia. Only a relatively low voltage is required to discharge in the liquid phase, and the energy efficiency is relatively low; compared with the gas phase and the liquid phase not being in direct contact, in this device and method, the discharge plasma is directly dissolved in water with microbubbles as the carrier, which improves the solubility of NO x in water. The high-voltage electrode and the ground electrode are separated by a quartz tube with micropores. During discharge, metal ion corrosion is effectively avoided during discharge; and the HNO x aqueous solution generated by aeration discharge nitrogen fixation can efficiently synthesize ammonia. The present invention is based on a stainless steel aeration head that can continuously generate micron-sized bubbles, and allows active particles such as NO x generated during discharge to dissolve in water with microbubbles as the carrier, which improves the concentration of the HNO x aqueous solution; and the nanosecond pulsed power supply has the characteristics of a fast rising edge, high instantaneous power and low average energy (the rising edge is 10 ns, the instantaneous power can reach 500-800 kW, the single-pulse energy is 7 mJ, and the average power is 7 W), etc., and has the advantage of high energy efficiency; the stainless steel aeration head (high-voltage electrode) and the copper mesh (ground electrode) are separated by a quartz tube with micropores, which has the characteristics of a quasi-microhollow cathode effect, enhances the discharge effect, and has two forms of spark discharge and corona discharge; use an H-type electrolytic cell to reduce the HNO x aqueous solution formed by aeration discharge to synthesize ammonia.

[0007] The nitrogen fixation device and method based on an aeration nanosecond pulse power supply of the present invention use a stainless - steel aeration head as a high - voltage electrode. At the same time, the continuous bubbles generated during the aeration of the stainless - steel aeration head have excellent characteristics, and the nanosecond pulse discharge has a short rising edge, high instantaneous power, and low average power. High - concentration HNO can be generated with low input energy. x ; Subsequently, the generated HNO x is coupled with electrocatalytic ammonia synthesis.

[0008] The present invention adopts the following technical solutions:

[0009] A device for nitrogen fixation coupling electrocatalytic ammonia synthesis based on aeration nanosecond pulse discharge includes an aeration nitrogen fixation reactor, a nanosecond pulse power supply, an air flow meter, an air pump, a first circulating water pump, a second circulating water pump, an H - type electrolytic cell, and an electrochemical platform;

[0010] Inside the aeration nitrogen fixation reactor, there are a stainless - steel aeration head, a quartz tube, and a copper mesh. The stainless - steel aeration head is located inside the quartz tube, and the copper mesh is attached to the outer wall of the quartz tube. There are multiple through - holes on the side wall of the quartz tube;

[0011] The nanosecond pulse power supply is connected to the stainless - steel aeration head; the air inlet of the air flow meter is connected to the air pump, and the air outlet of the air flow meter is connected to the stainless - steel aeration head; the water inlet of the first circulating water pump is connected to pure water or deionized water, and the water outlet of the first circulating water pump is connected to the water inlet of the aeration nitrogen fixation reactor; the water inlet of the second circulating water pump is connected to the water outlet of the aeration nitrogen fixation reactor, and the water outlet of the second circulating water pump is connected to the H - type electrolytic cell; the H - type electrolytic cell is connected to the electrocatalytic platform.

[0012] Furthermore, the device also includes a first stop valve and a second stop valve; the first stop valve is located at the bottom water inlet position of the aeration nitrogen fixation reactor; the second stop valve is located at the bottom water outlet position of the aeration nitrogen fixation reactor, where the first stop valve is connected to the first circulating water pump, and the second stop valve is connected to the second circulating water pump.

[0013] Furthermore, the nanosecond pulse power supply provides pulses with a fast rising edge and high instantaneous power to the aeration nitrogen fixation reactor. The pulses with a fast rising edge and high instantaneous power refer to pulses with a pulse width of 15 ns, a rising edge of 10 ns, and an instantaneous power of up to 500 - 800 kW.

[0014] Furthermore, the NHOx solution in the H - type electrolytic cell is generated by the aeration nitrogen fixation reactor, and the electrochemical platform conducts electrocatalytic experiments on the H - type electrolytic cell.

[0015] Furthermore, the stainless steel aeration head is divided into two parts: the upper part is a Φ6 stainless steel tube for air intake; the lower part is formed by stainless steel powder through high-temperature calcination to form a microporous structure, and the microporous structure is the gap between the powder particles after calcination and agglomeration. The micropores can evenly divide the air into several small air molecules, and can generate microbubbles with a diameter of 0.2-0.5μm during the ventilation process, which are evenly distributed between the high-voltage electrode of the stainless steel aeration head and the external copper mesh ground electrode. The introduction of microbubbles distorts the liquid phase electric field and reduces the breakdown field strength.

[0016] Furthermore, 40 holes with a diameter of 1 mm are arranged on the side wall of the quartz tube, and a copper mesh is attached to the outer wall of the quartz tube.

[0017] Furthermore, the copper mesh is used as a ground electrode; and the stainless steel aeration head is used as a high-voltage electrode.

[0018] Furthermore, the plasma discharge region includes: (a) a blocking region where the high voltage electrode and the ground electrode are connected through a quartz tube wall; and (b) a spark discharge channel formed by the high voltage electrode and the ground electrode through a through hole on the quartz tube wall. The discharge form in the blocking region is corona discharge. The discharge form in the spark discharge channel is spark discharge. The discharge form in the plasma discharge region is mainly spark discharge.

[0019] Furthermore, the plasma discharge region is formed by the high voltage electrode and the ground electrode excited by a nanosecond pulse power supply. There are two discharge forms: corona discharge and spark discharge. The discharge at the dielectric barrier belongs to corona discharge, and the discharge channel formed by the high voltage electrode and the ground electrode is spark discharge.

[0020] A method for synthesizing ammonia based on aerated nanosecond pulse discharge nitrogen fixation coupled with electrocatalytic synthesis, using the device as described in any one of the above items, the method comprising the following steps: an aerated nitrogen fixation reactor is powered by a nanosecond pulse power supply, and air with a predetermined flow rate is provided to it through an air pump and a flow meter; the water inlet of a first circulating water pump is pure water or deionized water, and the water outlet is connected to the water inlet of the aerated nitrogen fixation reactor to provide deionized water or pure water; the water inlet of a second circulating water pump is connected to the water outlet of the aerated nitrogen fixation reactor, and the water outlet is connected to the water inlet of an H-type electrolytic cell, providing the H-type electrolytic cell with aerated nitrogen fixation. The NOx aqueous solution after the reactor reaction; the electrochemical platform electrocatalytically reduces ammonia to the solution in the H-type electrolytic cell; the bottom part of the stainless steel aeration head is calcined from stainless steel powder into a microporous structure that can generate microbubbles and serves as the high-voltage electrode of the aeration nitrogen fixation reactor; the ground electrode is a copper mesh; the quartz tube is between the high-voltage electrode of the stainless steel aeration head and the ground electrode, and there are 40 1mm micropores on the side wall of the quartz tube, and the micropores enhance the electric field strength during discharge; the discharge area is the plasma discharge area that appears between the stainless steel aeration head and the ground electrode when the nanosecond pulse power supply applies a pulse voltage.

[0021] Specifically, the present invention discloses a device for nitrogen fixation by aerated nanosecond pulsed discharge and electrocatalytic ammonia synthesis. The device consists of three parts: an aerated nanosecond pulsed discharge nitrogen fixation unit, an electrocatalytic unit, and a gas supply and circulating water unit. Among them, the aerated nanosecond pulsed discharge nitrogen fixation unit includes an aerated nitrogen fixation reactor 1, a nanosecond pulsed power supply 2, a first circulating water pump 5, and a second circulating water pump 6; the electrocatalytic unit includes an H-type electrolytic cell 7 and an electrochemical platform 8; the gas supply and circulating water unit includes an air flow meter 3 and an air pump 4. Among them, the aerated nitrogen fixation reactor is a unique device designed in the present invention, and its structure includes a stainless steel aeration head 9, a discharge area 10, a quartz tube 11, a copper mesh 12, a first water stop valve 13, and a second water stop valve 14.

[0022] The specific components of the device include an aerated nitrogen fixation reactor 1, a nanosecond pulsed power supply 2, an air flow meter 3, an air pump 4, a first circulating water pump 5, a second circulating water pump 6, an H-type electrolytic cell 7, an electrochemical platform 8, a stainless steel aeration head 9, a discharge area 10, a quartz tube 11, a copper mesh 12, a first water stop valve 13, and a second water stop valve 14.

[0023] The aerated nitrogen fixation reactor 1 is a unique device of the present invention, and its structure includes a stainless steel aeration head 9, a discharge area 10, a quartz tube 11, a copper mesh 12, a first water stop valve 13, and a second water stop valve 14. The stainless steel aeration head 9 in the aerated nitrogen fixation reactor 1 is connected to the nanosecond pulsed power supply 2, and the first water stop valve 13 on the aerated nitrogen fixation reactor 1 is connected to the first circulating water pump 5; the second water stop valve 14 on the aerated nitrogen fixation reactor 1 is connected to the second circulating water pump 6 to control the inflow and outflow of the solution.

[0024] The nanosecond pulsed power supply 2 is connected to the stainless steel aeration head 9 in the aerated nitrogen fixation reactor 1 to provide a pulsed voltage for the aerated nitrogen fixation reactor 1.

[0025] The air inlet of the air flow meter 3 is connected to the air pump 4, and the air outlet is connected to the stainless steel aeration head 9 in the aerated nitrogen fixation reactor 1 to control the gas flow rate.

[0026] The air pump 4 is connected to the air inlet of the air flow meter 3 to provide air with a certain flow rate for the aerated nitrogen fixation reactor 1.

[0027] The water outlet of the first circulating water pump 5 is connected to the first water stop valve 13 to control the inflow rate of water in the aerated nitrogen fixation reactor 1.

[0028] The second circulating water pump 6 is connected to the second water stop valve 14 to control the outflow rate of water in the aerated nitrogen fixation reactor 1.

[0029] The H-type electrolytic cell 7 (single chamber capacity 150 mL) is connected to the outlet of the second circulation pump 6, and the second circulation pump 6 pumps the NOx aqueous solution generated in the nitrogen fixation reactor 1; and the electrocatalytic synthesis of ammonia experiment is controlled by the electrocatalytic platform 8.

[0030] The electrochemistry platform 8 uses a three-electrode system to conduct electrocatalytic experiments on the H-type electrolytic cell 7.

[0031] The stainless steel aeration head 9 serves as the high-voltage electrode of the aeration nitrogen fixation reactor 1 and is connected to the nanosecond pulse power supply 12; at the same time, as microbubbles, it has the characteristics of microbubble generation.

[0032] The plasma discharge region 10 is the region formed by the stainless steel aeration head 9 and the external copper mesh 12 excited by the nanosecond pulse power supply 2.

[0033] The side wall of the quartz tube 11 is laser-drilled with 40 micropores of 1 mm, and the position of the quartz tube 11 is between the stainless steel aeration head 9 and the copper mesh 12.

[0034] The copper mesh 12 is attached to the outer wall of the perforated quartz tube 11 as the ground electrode.

[0035] The water inlet of the first stop valve 13 is connected to the first circulation pump 5, and the water outlet is connected to the water inlet of the aeration nitrogen fixation reactor 1.

[0036] The water inlet of the second stop valve 14 is connected to the aeration nitrogen fixation reactor 1, and the water outlet is connected to the H-type electrolytic cell 7.

[0037] The beneficial effects of the present invention are as follows:

[0038] First, a fast nanosecond pulse power supply (pulse width 15 ns) is used to couple with microbubbles to quickly fix nitrogen in the air with a NOx aqueous solution;

[0039] Second, a highly efficient metastable foam copper catalyst is prepared to reduce and synthesize ammonia from the NOx in the previous step in a short time;

[0040] Third, the preparation of the HNOx activation aqueous solution and the integrated device structure of electrochemical reduction in the present invention make the preparation of small-scale synthetic ammonia convenient, fast, green and environmentally friendly. Its specific features are: (1) The aeration method of the present invention uses the stainless steel aeration head 9 to continuously generate microbubbles of 0.2 - 0.5 μm, and uses the characteristics of long microbubble existence time, large specific area, high mass transfer efficiency, etc. to dissolve efficiently in water; at the same time, the stainless steel aeration head 9 can also be used as a high-voltage electrode, and the effective area during discharge is relatively large. (2) The power supply used in the present invention is the nanosecond pulse power supply 2, which has the characteristics of fast pulse rise time and high instantaneous power, and can stimulate the discharge of the aeration nitrogen fixation reactor at a lower input energy, so that N2 in the atmosphere can be converted into HNO with a higher concentration. xFixed in an aqueous solution. (3) In the present invention, based on the HNO generated by aerated nanosecond pulsed discharge x The aqueous solution uses an H-type electrolytic cell 7 and can efficiently reduce and synthesize ammonia. Description of the Drawings

[0041] Figure 1 Overall device;

[0042] Figure 2 Device diagram of the nitrogen fixation unit based on aerated liquid-phase discharge

[0043] Figure 3 Graph of the concentration of aerated discharge HNOx varying with time;

[0044] Figure 4 Graph of electrocatalytic synthesis of ammonia from HNOx;

[0045] In the figure, 1 is an aerated nitrogen fixation reactor, 2 is a nanosecond pulse power supply, 3 is an air flow meter, 4 is an air pump, 5 is a first circulating water pump, 6 is a second circulating water pump, 7 is an H-type electrolytic cell, 8 is an electrochemical platform, 9 is a stainless steel aeration head, 10 is a discharge area, 11 is a quartz tube, 12 is a copper mesh, 13 is a first water stop valve, and 14 is a second water stop valve. Detailed Embodiments

[0046] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the protection scope of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0047] The present invention discloses a device and method for nitrogen fixation coupling electrocatalytic synthesis of ammonia based on aerated nanosecond pulsed discharge. As Figure 1-2 shown, the device consists of three parts: an aerated nanosecond pulsed discharge nitrogen fixation unit, an electrocatalytic unit, and a gas supply and circulating water unit. Among them, the aerated nanosecond pulsed discharge nitrogen fixation unit includes an aerated nitrogen fixation reactor 1, a nanosecond pulse power supply 2, a first circulating water pump 5, and a second circulating water pump 6; the electrocatalytic unit includes an H-type electrolytic cell 7 and an electrochemical platform 8; the gas supply and circulating water unit includes an air flow meter 3 and an air pump 4.

[0048] The described device and method for nitrogen fixation coupling electrocatalytic synthesis of ammonia based on aerated nanosecond pulsed discharge, the specific components of the experimental device include an aerated nitrogen fixation reactor 1, a nanosecond pulse power supply 2, an air flow meter 3, an air pump 4, a first circulating water pump 5, a second circulating water pump 6, an H-type electrolytic cell 7, and an electrochemical platform 8.

[0049] Inside the aeration nitrogen fixation reactor 1, there are a stainless-steel aeration head 9, a quartz tube 11, and a copper mesh 12. The stainless-steel aeration head 9 is located inside the quartz tube 11, and the copper mesh 12 is attached to the outer wall of the quartz tube 11. There are 40 small holes on the side wall of the quartz tube 11, and the small holes are through holes.

[0050] The nanosecond pulse power supply 2 is connected to the stainless-steel aeration head 9; the air inlet of the air flowmeter 3 is connected to the air pump 4, and the air outlet of the air flowmeter 3 is connected to the stainless-steel aeration head 9; the water inlet of the first circulation water pump 5 is connected to pure water or deionized water, and the water outlet of the first circulation water pump 5 is connected to the water inlet of the aeration nitrogen fixation reactor 1; the water inlet of the second circulation water pump 6 is connected to the water outlet of the aeration nitrogen fixation reactor 1, and the water outlet of the second circulation water pump 6 is connected to the H-type electrolytic cell 7; the H-type electrolytic cell 7 is connected to the electrocatalytic platform 8.

[0051] As Figure 2 shown, the aeration nitrogen fixation reactor 1 is a unique device of the present invention, and its structure includes a stainless-steel aeration head 9, a discharge area 10, a quartz tube 11, a copper mesh 12, a first water stop valve 13, and a second water stop valve 14. The lower opening of the stainless-steel aeration head 9 is a microporous structure formed by sintering stainless-steel powder, which can evenly divide air into several small air molecules, forming a large number of microbubbles with a size of 0.2 - 0.5 μm between the high voltage and the ground electrode. The stainless-steel aeration head 9 also serves as the high-voltage electrode for discharging; the copper mesh 12 serves as the ground electrode; the quartz tube 11 serves as a dielectric barrier, and there are 40 micropores with a diameter of 1 mm on the side wall of the quartz tube 11. The first circulation water pump 5 is sequentially connected to the first water stop valve 13 and the water inlet of the aeration nitrogen fixation reactor 1. The water outlet of the aeration nitrogen fixation reactor 1 is sequentially connected to the second water stop valve 14 and the second circulation water pump 6. The first water stop valve 13 controls the inflow of deionized water into the nitrogen fixation reactor 1; the second water stop valve 14 controls the outflow of the treated activated water from the nitrogen fixation reactor 1; the discharge area 10 includes two parts: corona discharge (the area blocked by the quartz tube wall between the high-voltage electrode and the ground electrode) and spark discharge (the spark discharge channel formed by the high-voltage electrode and the ground electrode through the micropores of the quartz tube wall).

[0052] The nanosecond pulse power supply 2 is connected to the stainless-steel aeration head 9 in the aeration nitrogen fixation reactor 1, providing pulses with a fast rising edge, high instantaneous power (rising edge 10 ns, instantaneous power up to 500 - 800 kW, single-pulse energy 7 mJ, average power 7 W), forming a strong discharge area 10 (corona discharge and spark discharge) in the aeration nitrogen fixation reactor.

[0053] The air inlet of the air flowmeter 3 is connected to the air pump 4, and the air outlet is connected to the stainless-steel aeration head 9 in the aeration nitrogen fixation reactor 1, controlling the air flow rate entering the stainless-steel aeration head 9, and filling the reactor with uniformly sized microbubbles;

[0054] The air pump 4 is connected to the inlet of the air flow meter 3 to provide air with a certain flow rate for the aeration and nitrogen fixation reactor 1. The maximum air flow rate of the air pump can be 10 L / min.

[0055] The outlet of the first circulation water pump 5 is connected to the first water stop valve 13 to control the water inflow rate in the aeration and nitrogen fixation reactor 1.

[0056] The inlet of the second circulation water pump 6 is connected to the second water stop valve 14 to control the water outflow rate in the aeration and nitrogen fixation reactor 1 and provide an activated aqueous solution after discharge treatment for the H-type electrolytic cell 7.

[0057] The H-type electrolytic cell 7 (single chamber capacity 150 mL) is connected to the outlet of the second circulation water pump 6. The second circulation water pump 6 pumps the NOx aqueous solution generated in the nitrogen fixation reactor 1, and an electrocatalytic experiment is carried out through the electrochemical platform 8.

[0058] The electrochemical platform 8 uses three electrodes to carry out an electrocatalytic experiment on the H-type electrolytic cell 7.

[0059] The stainless steel aeration head 9 is divided into upper and lower parts: the upper part is a stainless steel pipe with a diameter of Ф6 for air intake; the lower part is a cylindrical aeration head with a diameter of Ф17 mm and a height of 30 mm formed by sintering stainless steel powder. There are tiny gaps at the powder connection to evenly divide the air into several small air molecules, and microbubbles with a size of 0.2 - 0.5 μm can be formed.

[0060] The plasma discharge region 10 is the region formed by the stainless steel aeration head 9 and the external copper mesh 12 excited by the nanosecond pulse power supply 2, including two parts: corona discharge (the region blocked by the quartz wall between the high-voltage electrode and the ground electrode) and spark discharge (the spark discharge channel formed by the high-voltage electrode and the ground electrode through the small holes in the quartz tube wall). The main discharge form is spark discharge.

[0061] The perforated quartz tube 11 has an inner diameter of 19 mm and an outer diameter of 21 mm. There are 40 microholes with a diameter of 1 mm laser-drilled on the side wall of the quartz tube 11 for exhaust and increasing the discharge field strength; and a layer of copper mesh 12 is attached to the outer wall of the quartz tube 11 as the ground electrode.

[0062] The copper mesh 12 is attached to the outer wall of the perforated quartz tube 11 as the ground electrode.

[0063] The inlet of the first water stop valve 13 is connected to the first circulation pump 5, and the outlet is connected to the inlet of the aeration and nitrogen fixation reactor 1 to control the inflow of deionized water or pure water.

[0064] The inlet of the second water stop valve 14 is connected to the aeration and nitrogen fixation reactor 1, and the outlet is connected to the H-type electrolytic cell 7 through the second circulation water pump to control the outflow of the NOx activated aqueous solution after the reaction in the aeration and nitrogen fixation reactor 1.

[0065] Example 1:

[0066] Open the first water stop valve 13, and supply 200 mL of deionized water or pure water to the aeration nitrogen fixation reactor 1 through the first circulation water pump 5, then close the first water stop valve 13; open the air pump 4 and adjust the air flowmeter 3 to supply air with a flow rate of 2 L / min to the aeration nitrogen fixation reactor 1; turn on the nanosecond pulse power supply to provide a pulse wave with a 10 ns rising edge and an average power of 7 W, and stimulate the aeration nitrogen fixation reactor 1 to discharge for 30 min, then turn off the power supply. After detection, it can be obtained that the concentration of the HNOx solution in the aeration nitrogen fixation reactor 1 is about 5 mmol / L. The change of HNOx concentration is as Figure 3 shown. Using a nanosecond pulse power supply to couple microbubble liquid-phase discharge, the activation of NOx in the aqueous solution almost linearly increases with the discharge time. After discharging for 30 min, the concentration of the NOx aqueous solution can reach 5 mmol / L. After calculation, the nitrogen fixation rate can reach 2 mmol / h, and its energy efficiency can reach 12.6 MJ / mol.

[0067] Example 2:

[0068] After the 200 mL of HNOx solution prepared in Example 1 after 30 min of discharging is treated with 4 mL of 1 M KOH solution, open the second water stop valve 14, and pass it into the H-type electrolytic cell 7 through the second circulation water pump 6, with 100 mL in each single chamber, then close the second water stop valve; the catalyst used here is the treated Cu / Cu2O metastable foam copper with an area of 0.5 * 2 cm 2 The treatment method is that the area of 0.5 * 2 cm 2 is calcined at a high temperature of 300 - 500 °C for 30 min to form CuO foam copper (black), and then the above-mentioned CuO foam copper is electrochemically reduced at a constant potential of -1.3 V vs RHE on the electrochemical platform for 30 min to form a Cu / Cu2O metastable copper catalyst (bronze); use the catalyst treated in the previous step to electrocatalytically treat the above-mentioned NOx solution at a voltage of -1.3 V vs RHE; use this catalyst to treat the above-mentioned NOx aqueous solution, the electrocatalytic treatment time is 60 min, collect and test the concentration of the electrocatalytically synthesized ammonia; continue the above steps and repeat the experiment 5 times. The concentration of electrocatalytically converted NH4 + in the aqueous solution can reach 1.5 mM, and the Faraday efficiency can reach 86%; this catalyst has excellent performance and can be reused; the catalytic effect diagram is as Figure 4 , Based on underwater aeration nitrogen fixation coupled with electrocatalytic reduction for ammonia synthesis, an NH4 solution with a concentration of 1.5 mM can be obtained in a short time + , and the catalyst can be reused.

[0069] The parts not elaborated in the present invention belong to the well-known technologies of those skilled in the art. The above-described embodiments are only descriptions of the preferred embodiments of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An apparatus for nitrogen fixation based on aerated nanosecond pulsed discharge coupled with electrocatalytic ammonia synthesis, characterized in that, It includes an aeration nitrogen fixation reactor (1), a nanosecond pulse power supply (2), an air flow meter (3), an air pump (4), a first circulation water pump (5), a second circulation water pump (6), an H-type electrolytic cell (7) and an electrochemical platform (8); Inside the aeration nitrogen fixation reactor (1), there are a stainless steel aeration head (9), a discharge area (10), a quartz tube (11), a copper mesh (12), a first water stop valve (13) and a second water stop valve (14). The stainless steel aeration head (9) is located inside the quartz tube (11). The copper mesh (12) is attached to the outer wall of the quartz tube (11). There are multiple through holes on the side wall of the quartz tube (11). The stainless steel aeration head (9) serves as the high-voltage electrode for discharging. The lower opening of the stainless steel aeration head (9) is a microporous structure formed by sintering stainless steel powder. Its microporous structure is the gap between the powder particles after sintering. During the ventilation process, microbubbles with a diameter of 0.2 - 0.5 μm are evenly distributed between the high-voltage electrode of the stainless steel aeration head (9) and the external copper mesh (12) ground electrode. The copper mesh (12) serves as the ground electrode. The quartz tube (11) serves as a dielectric barrier. The first circulation water pump (5) is sequentially connected to the first water stop valve (13) and the water inlet of the aeration nitrogen fixation reactor (1). The water outlet of the aeration nitrogen fixation reactor (1) is sequentially connected to the second water stop valve (14) and the second circulation water pump (6). The first water stop valve (13) controls the inflow of deionized water into the nitrogen fixation reactor (1). The second water stop valve (14) controls the outflow of the treated activated water from the nitrogen fixation reactor (1); The nanosecond pulse power supply (2) is connected to the stainless steel aeration head (9) to provide pulses and form a discharge area (10) in the aeration nitrogen fixation reactor. The discharge area (10) includes two parts: corona discharge and spark discharge. The air inlet of the air flow meter (3) is connected to the air pump (4), and the air outlet of the air flow meter (3) is connected to the stainless steel aeration head (9). The water inlet of the first circulation water pump (5) is connected to pure water or deionized water. The water outlet of the second circulation water pump (6) is connected to the H-type electrolytic cell (7). The H-type electrolytic cell (7) is connected to the electrocatalytic platform (8); The nanosecond pulse power supply provides pulses with a fast rising edge and high instantaneous power to the aeration nitrogen fixation reactor. The pulses with a fast rising edge and high instantaneous power refer to pulses with a pulse width of 15 ns, a rising edge of 10 ns, and an instantaneous power of 500 - 800 kW.

2. The apparatus according to claim 1, characterized in that, The device also includes a first water stop valve (13) and a second water stop valve (14). The first water stop valve (13) is located at the water inlet position at the bottom of the aeration nitrogen fixation reactor (1). The second water stop valve (14) is located at the water outlet position at the bottom of the aeration nitrogen fixation reactor (1).

3. The apparatus according to claim 1, characterized in that, The NHOx solution in the H-type electrolytic cell (7) is generated by the aeration nitrogen fixation reactor (1), and the electrochemical platform (8) conducts electrocatalytic experiments on the H-type electrolytic cell (7).

4. The apparatus according to claim 1, characterized in that, The stainless steel aeration head (9) is divided into upper and lower parts: the upper part is a stainless steel tube with a diameter of Ф6 for air intake.

5. The apparatus according to claim 1, characterized in that, The discharge area (10) is a plasma discharge area formed by exciting the high-voltage electrode of the stainless steel aeration head (9) and the external copper mesh (12) ground electrode by the nanosecond pulse power supply (2).

6. The apparatus according to claim 1, characterized in that, The discharge region (10) includes: (a) a region blocked by the quartz tube wall between the high-voltage electrode and the ground electrode; and (b) a spark discharge channel formed by the high-voltage electrode and the ground electrode through the through-holes in the quartz tube wall; the discharge form in the blocked region is corona discharge; the discharge form in the spark discharge channel is spark discharge.

7. The apparatus according to claim 1, characterized in that, There are 40 holes with a diameter of 1 mm on the side wall of the quartz tube (11).

8. A method for nitrogen fixation based on aerated nanosecond pulsed discharge coupled with electrocatalytic ammonia synthesis, characterized in that, Using the device according to any one of claims 1-7, the method includes the following steps: the aeration nitrogen fixation reactor (1) is powered by a nanosecond pulse power supply (2), and air with a predetermined flow rate is provided for it through an air pump (4) and a flow meter (3); the inlet of the first circulation water pump (5) is pure water or deionized water, and the outlet is connected to the inlet of the aeration nitrogen fixation reactor (1) to provide deionized water or pure water; the inlet of the second circulation water pump (6) is connected to the outlet of the aeration nitrogen fixation reactor (1), and the outlet is connected to the inlet of the H-type electrolytic cell (7) to provide the NOx aqueous solution reacted by the aeration nitrogen fixation reactor (1) for the H-type electrolytic cell (7); the electrochemical platform (8) electrocatalytically reduces ammonia in the solution in the H-type electrolytic cell (7); the bottom part of the stainless steel aeration head (9) is calcined from stainless steel powder into a microporous structure capable of generating microbubbles and serves as the high-voltage electrode of the aeration nitrogen fixation reactor (1); the ground electrode is a copper mesh (12); the quartz tube (11) is located between the high-voltage electrode of the stainless steel aeration head (9) and the ground electrode, and there are 40 micropores with a diameter of 1 mm on the inner wall of the quartz tube (11), and the presence of the micropores enhances the electric field strength during discharge; the discharge region (10) is a plasma discharge region that appears between the stainless steel aeration head (9) and the ground electrode of the copper mesh (12) when a pulsed voltage is applied by the nanosecond pulse power supply (2).

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