LiDFOB electrolyte, electrocatalytic ammonia synthesis reactor and its application in lithium metal-mediated nitrogen reduction for ammonia production.

Abstract

This invention relates to a LiDFOB electrolyte, an electrocatalytic ammonia synthesis reactor, and its application in the lithium metal-mediated nitrogen reduction for ammonia production. The electrolyte comprises LiDFOB, an organic solvent, and ethanol, wherein LiDFOB is dissolved in the organic solvent to obtain a solution with a molar concentration of 1–3 M, and ethanol is added, with the amount of ethanol added controlled to be 0.001–1.0% of the volume of the organic solvent. A nitrogen electrocatalytic reaction system is constructed using a flow-type electrocatalytic ammonia synthesis reactor. Nitrogen and hydrogen from nitrogen and hydrogen cylinders are respectively introduced into the cathode and anode chambers of the electrocatalytic ammonia synthesis reactor. The current density applied to the nitrogen electrocatalytic reaction system is controlled to be 6–300 mA / cm². 2 The NH3 product is obtained by alternating cyclic electrolytic catalysis using a deposition-OCV mode. Compared with existing technologies, the maximum bias current density of this invention exceeds 100 mA / cm². 2 It maintains excellent ammonia selectivity and production efficiency even after running continuously for more than 50 hours, making it a more efficient and stable reaction system compared to currently reported electrocatalytic technologies.

Description

Technical Field

[0001] This invention belongs to the field of nitrogen reduction synthesis of ammonia, and in particular relates to a method for preparing ammonia by lithium metal-mediated electrocatalytic conversion of nitrogen. Background Technology

[0002] Ammonia is one of the most important chemicals in modern industry, serving not only as a raw material for the synthesis of chemical fertilizers (such as urea) and amino acids, but also as a potential clean fuel. Global annual industrial ammonia production exceeds 200 million tons. Currently, ammonia production via the Haber-Bosch process consumes approximately 1.8% of global energy, and the carbon dioxide emissions from this process account for 1.8% of total global carbon dioxide emissions. Therefore, developing green energy-driven, low-energy-consumption, and sustainable ammonia synthesis technologies is crucial. Directly synthesizing ammonia from nitrogen using renewable electricity and water is one way to reduce carbon emissions from the chemical industry. Lithium metal-mediated electrocatalytic nitrogen reduction reaction (Li-N₂RR) at ambient temperature and pressure is a highly promising new ammonia synthesis technology.

[0003] WO2024052575A3 discloses a mobile phase electrolyzer for lithium-mediated ammonia synthesis at room temperature and pressure, its preparation, and its application. This mobile electrolyzer employs a three-chamber structure, comprising a nitrogen chamber with a porous copper cathode electrode, a tetrahydrofuran electrolyte chamber with multi-channel LiBF4, and a hydrogen chamber with a PtAu anode catalyst. Although this technology utilizes a lithium-mediated ammonia synthesis mobile phase reaction cell to increase the ammonia synthesis rate, its use of LiBF4 electrolyte results in extremely low operating current and ammonia synthesis efficiency.

[0004] Patent application 202310757017.0 discloses a membrane electrode for lithium-mediated ammonia synthesis, its preparation method, and its application. This membrane electrode employs a "three-in-one" structure, comprising a lithium-deposited stainless steel mesh as the cathode, a lithium-ion-doped polyethylene oxide membrane as the polymer electrolyte film, and carbon paper loaded with a Pt / C catalyst as the anode. The membrane electrode is assembled by pressing in a glove box and can be used in conjunction with a conventional gas diffusion electrolyzer for nitrogen reduction reactions to synthesize ammonia. Although this technology somewhat substitutes for reaction rate and mass transfer efficiency, it uses a solid molten salt electrolyte system, which requires a high temperature of 200-300℃ and has a low lithium-ion transport rate; furthermore, this system generates N... 3- Anions are transported to the anode and react with hydrogen to generate ammonia, resulting in a low operating current density.

[0005] In fact, the current densities reported for highly selective lithium metal dielectric conductive nitrogen reduction are all below 10 mA / cm². 2This is far below the industrial current density required for widespread industrial applications. This is because as the current density increases, the decrease in cathode potential leads to inefficient lithium metal deposition and electrolyte decomposition, resulting in byproducts and a decrease in product selectivity. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art by providing a LiDFOB electrolyte, an electrocatalytic ammonia synthesis reactor, and its application in the lithium metal-mediated nitrogen reduction for ammonia preparation. By introducing lithium metal, the invention promotes the associative decomposition and cleavage of the N≡N triple bond in the N2 molecule, thereby facilitating lithium ion conduction and lithium ion desolvation, promoting efficient lithium metal deposition, achieving a highly efficient lithium metal-nitrogen reaction, and increasing the yield by orders of magnitude.

[0007] The objective of this invention can be achieved through the following technical solution: a LiDFOB electrolyte comprising LiDFOB, an organic solvent and ethanol, wherein LiDFOB is dissolved in the organic solvent to obtain a solution with a molar concentration of 1-3M, and ethanol is added, with the amount of ethanol added controlled to be 0.001-1.0% of the volume of the organic solvent.

[0008] Furthermore, the organic solvent includes one or more of tetrahydrofuran, dimethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and one or more of ethanol, propanol, butanol, or isopropanol.

[0009] The present invention also provides an electrocatalytic ammonia synthesis reaction tank, comprising a cathode gas chamber, an anode gas chamber, and an electrolyte chamber. The cathode gas chamber and the anode gas chamber are respectively disposed on both sides of the electrolyte chamber, wherein the cathode gas chamber is provided with a cathode and a nitrogen inlet, the anode gas chamber is provided with an anode and a hydrogen inlet, and the electrolyte chamber is filled with the LiDFOB electrolyte.

[0010] Furthermore, the anode is prepared by the following method: a stainless steel mesh is used as a supporting electrode and as the working electrode for electroplating, connected to an external circuit as the cathode; two Pt mesh electrodes are used as the counter electrodes, placed opposite the stainless steel mesh on both sides, connected to an external circuit as the anode; the cathode and anode are immersed in a sulfuric acid solution of chloroplatinic acid and chloroauric acid, wherein the molar ratio of Pt, Au, and sulfuric acid is 1:1:200-400, and an A / cm² pressure is applied. 2 Current density, constant current electroplating for 1-5 minutes, controlling the loading of Pt and Au on the supporting electrode to be 40-100 mg / cm³. 2 The prepared stainless steel mesh supported on PtAu was used as the anode catalyst.

[0011] Furthermore, the cathode is a double-layer stainless steel mesh, which has a pore size of 150-180 micrometers on one side and a pore size of 20-40 micrometers on the other side, with the 20-40 micrometer pore mesh surface facing the electrolyte side.

[0012] Furthermore, the electrolyte chamber has a liquid flow channel with a width of 0.5–2 mm.

[0013] This invention also provides an application of lithium metal-mediated nitrogen reduction to prepare ammonia using an electrocatalytic ammonia synthesis reactor. Hydrogen and nitrogen are respectively input into the anode and cathode chambers of the electrocatalytic ammonia synthesis reactor, and the current density applied to the reactor is controlled to be 6–300 mA / cm². 2 The NH3 product was obtained by alternating cyclic electrolytic catalysis using a "deposition-OCV" mode.

[0014] Furthermore, the flow rates of hydrogen and nitrogen gas input into the electrocatalytic ammonia synthesis reactor are controlled to be 50-100 mL / min, and the flow rate of electrolyte is controlled to be 1-3 mL / min.

[0015] Furthermore, the “deposition-OCV” mode consists of electrolytic deposition for 2–60 seconds, open circuit for 30–60 seconds, and 1–6000 cycles.

[0016] Furthermore, during the electrolysis process, lithium ions in the electrolyte are deposited layer by layer on the cathode to form a LiF / Li2CO3 / Li3N SEI structure.

[0017] Furthermore, 0.2-0.5M dilute sulfuric acid is used to absorb the ammonia gas generated in the tail gas at both the cathode and anode outlets. 0.2-0.5M dilute sulfuric acid is added to the electrolyte in the electrolyte chamber to absorb the ammonia gas dissolved in the electrolyte. The cathode catalyst after electrolysis is reacted and absorbed by deionized water to obtain an ammonium ion aqueous solution. The ammonia absorption solution is then heated to obtain ammonia gas.

[0018] Compared with the prior art, the present invention has the following superior effects:

[0019] (1) This invention uses a novel lithium borate salt as the electrolyte. The introduction of lithium metal promotes the associative decomposition and cleavage of the N≡N triple bond in the N₂ molecule, forming active Li₃N, which combines with hydrogen protons in the solution to obtain ammonia. Using this novel electrolyte as the electrolyte in the electrocatalytic ammonia synthesis reactor, hydrogen and nitrogen undergo an electrolytic catalytic reaction. The novel electrolyte promotes the desolvation and conduction of lithium ions in the SEI membrane, forming a high lithium ion conductivity structure, thereby accelerating lithium metal deposition and promoting a high-current nitrogen reduction reaction, achieving a current density of 100 mA / cm² and a Faradaic efficiency of approximately 97% for ammonia. Operating at 100 mA / cm² for 50 hours, the system consistently maintains approximately 80% Faradaic efficiency and approximately 21.5% power conversion efficiency.

[0020] (2) In existing reported technical solutions, the nitrogen-to-ammonia reaction faces problems such as poor selectivity and low yield. This is because the commonly used LiBF4 organic electrolyte generates a solid electrolyte interphase (SEI) rich in LiF and LiH, hindering lithium-ion mass transfer. Consequently, the lithium metal deposition reaction dominates at high current densities, producing numerous byproducts such as dead lithium or organic lithium salts during deposition. Based on this, this invention introduces a novel lithium borate salt: lithium difluorooxalate borate (LiDFOB), which forms an anion-rich lithium-ion solvation structure. This solvation structure facilitates the decomposition of anions to generate an inorganic lithium salt-rich SEI layer, while simultaneously... - Containing functional groups such as BF and -C2O4, it can form a LiF / Li2CO3 SEI structure during decomposition. In the electrocatalytic ammonia synthesis reactor, nitrogen participates in the formation process of the SEI, resulting in a LiF / Li2CO3 / Li3N SEI structure. This SEI layer is rich in Li2CO3 with high ionic conductivity and LiF with high desolvation capability, thereby improving the lithium-ion conduction and lithium-ion desolvation capability of the SEI film, promoting efficient lithium metal deposition, realizing efficient lithium metal nitrogen reaction, and achieving an order-of-magnitude improvement in yield.

[0021] (3) The maximum bias current density of the system of the present invention exceeds 100 mA / cm². 2 (Currently reported technologies are all below 10 mA / cm) 2 It maintains excellent ammonia selectivity and production efficiency even after continuous operation for more than 50 hours, with a maximum of 100 mA / cm². 2 At the given current density, with a Faraday efficiency exceeding 90%, the ammonia yield reached 260 μmol NH3 / cm³. 2 / h is the most advanced and efficient nitrogen reduction ammonia synthesis system reported to date, and it is a more efficient and stable reaction system. Attached Figure Description

[0022] Figure 1 A system diagram of a lithium metal-mediated nitrogen reduction reaction for ammonia synthesis;

[0023] Figure 2 This is a comparison diagram between the present invention and previously reported selective electroreduction ammonia synthesis technologies;

[0024] Figure 3 The Faraday efficiency of ammonia products at different low current densities;

[0025] Figure 4 The Faraday efficiency of ammonia products under different high current densities is given. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] This invention provides a novel, efficient, stable, and continuous system for the electrocatalytic conversion of nitrogen to ammonia. A nitrogen electrocatalytic reaction system is constructed, and ammonia is synthesized using a flow-type electrocatalytic reactor. The construction of the electrocatalytic ammonia synthesis reactor and the ammonia synthesis reaction are as follows:

[0028] (1) A 316 or 304 single-layer stainless steel mesh is used as the support electrode and as the working electrode for electroplating. It is connected to the external circuit as the cathode. Two Pt mesh electrodes are used as the counter electrode, placed opposite the stainless steel mesh on both sides and connected to the external circuit as the anode. The cathode and anode are immersed in a 3M sulfuric acid solution of chloroplatinic acid and chloroauric acid (where the molar ratio of Pt, Au and sulfuric acid is 1:1:200-400, preferably 1:1:300), and an A / cm² pressure is applied. 2 Current density, constant current plating time 1-5 minutes, Pt and Au loading 40-100 mg / cm³ 2 The PtAu supported on the stainless steel mesh was then washed three times alternately with deionized water and ethanol, and dried at 50-70℃ for 10-14 h. The resulting PtAu was used as the anode catalyst.

[0029] (2) A double-layer stainless steel mesh is used as a cathode catalyst. The catalyst has a pore size of 150-180 micrometers on one side and a pore size of 20-40 micrometers on the other side, with the pore size of 20-40 micrometers facing the electrolyte side.

[0030] (3) Dissolve commercially available LiDFOB in an organic solvent (preferably tetrahydrofuran solvent) to obtain a solution with a molar concentration of 1-3M. Add ethanol, controlling the amount of ethanol added to be 0.001-1.0% of the volume of the organic solvent. After stirring, a transparent electrolyte is obtained. The electrolyte concentration is controlled at 1-3M, and the ethanol content is controlled at 0.15-0.35% by volume.

[0031] (4) Construction of the electrocatalytic ammonia synthesis reaction cell: A three-chamber flow electrolytic cell is used as the electrocatalytic reaction device. The material of the three-chamber flow electrolytic cell is stainless steel, Ti, or PEEK, preferably PEEK. The three-chamber flow electrolytic cell includes a cathode, an anode, and an electrolyte chamber. The anode includes an anode gas chamber, a silicone gasket, a PTFE plate, and an anode catalyst. The cathode includes a cathode gas chamber, a silicone gasket, a PTFE plate, and a cathode catalyst. The anode and cathode are located on opposite sides of the electrolyte chamber. A 0.5–2 cm opening is made in the middle of the sidewall of the cathode gas chamber and the anode gas chamber facing each other. 2 A square through hole, with a 0.5-2cm opening at the top center of the through hole. 2 The square through-hole is sealed with a silicone gasket and has a center opening of 0.5–2 cm. 2 A 0.2–1 mm thick PEEK plate with square through-holes has circular through-holes (2–4 mm diameter) on both sides to connect the inlet and outlet. The electrolyte chamber has a 0.5–2 cm diameter opening in the center. 2 A 10-15mm thick PEEK plate with square through-holes has 0.5-2mm flow channels on both sides for electrolyte flow to the cathode and anode. Circular through-holes with a diameter of 2-4mm are located on both sides of the square through-holes, connecting the inlet and outlet ends. The cathode and anode gas chambers are located on opposite sides of the electrolyte chamber. The cathode gas chamber has the cathode catalyst and nitrogen inlet described in step (2), while the anode gas chamber has the anode catalyst and hydrogen inlet described in step (1). The electrolyte chamber is filled with the LiDFOB electrolyte described in step (3). Both the cathode and anode electrolytes are 1-3M LiDFOB organic solutions.

[0032] (5) Figure 1 As shown, high-purity nitrogen gas 1 passes through MFC (gas mass flow controller) 2 and one-way valve 3 in sequence to reach the cathode chamber 4 of the electrocatalytic ammonia synthesis reactor, and high-purity hydrogen gas 5 passes through MFC (gas mass flow controller) 6 and one-way valve 7 in sequence to reach the anode chamber 8 of the electrocatalytic ammonia synthesis reactor. The gas flow rate is 50-100 mL / min, and the electrolyte flow rate in electrolyte chamber 9 is 0.3-1 mL / min, measured with a 1 bar pressure gauge.

[0033] (6) The electrocatalytic ammonia synthesis reactor adopts an alternating cyclic electrolytic catalysis mode of "deposition-OCV", and the electrolysis conditions include: current density of 6-300 mA / cm². 2 The deposition time is 2–60 s, the open-circuit time is 30–60 s, and the cycle is repeated multiple times, preferably 1–1000 times; the reaction pressure is 1 bar.

[0034] Lithium metal deposition and hydrogen oxidation reactions occur on the anode and cathode surfaces, respectively. The resulting lithium metal cracks nitrogen molecules to form Li3N, which reacts with protons generated at the anode, subsequently producing NH3 as a product in a continuous flow electrocatalytic reactor. The reaction formula is as follows:

[0035] Li + + e - =Li (1)

[0036] 6Li + N2 = 2 Li3N (2)

[0037] Li3N + 3EtOH= NH3(g) + 3Li + + 3EtO - (3)

[0038] During multiple electrolysis cycles, in the "deposition-open circuit" reaction mode, DFOB - Anions decompose to form the main LiF / Li2CO3 SEI structure, while nitrogen molecules react with the deposited lithium metal to form Li3N inside the SEI, thus forming the LiF / Li2CO3 / Li3N SEI structure.

[0039] (7) The cathode and anode gases obtained from the electrocatalytic ammonia synthesis reaction tank are absorbed by the cathode gas collection bottle 10 and the anode gas collection bottle 11, which are filled with 0.2M-0.5M H2SO4 solution. The resulting absorption liquid is an ammonium sulfate / sulfuric acid mixture.

[0040] (8) The electrolyte after the reaction in the electrocatalytic ammonia synthesis reaction cell enters the collection bottle 13, and is taken outside the glove box for absorption with an equal volume of 0.2M-0.5M H2SO4 solution. The resulting electrolyte absorption solution is a mixture of ammonium sulfate / LiDFOB / THF.

[0041] (9) The cathode catalyst after the reaction in the electrocatalytic ammonia synthesis reactor is absorbed by deionized water to obtain an ammonium aqueous solution. After heating at 60-80℃, ammonia gas is obtained, and finally a collection liquid of ammonia products is obtained.

[0042] Figure 2 This is a comparison diagram between the present invention and previously reported selective electroreduction ammonia synthesis technologies; it can be seen from the diagram that the current density of the flow-type lithium-mediated ammonia synthesis system is often limited to 10 mA / cm². 2 The highest Faraday efficiency is only 75.6%. This invention uses a novel LiF / Li2CO3 / Li3N SEI structure, breaking through the 100 mA level current density and achieving a Faraday efficiency of nearly 100%, which is of great value for efficient ammonia synthesis.

[0043] Unless otherwise specified, all raw materials and equipment used in this invention are commercially available or commonly used. For example, the lithium difluorooxalate borate used in the following embodiments is the NE-000025 model product commercially available from Duoduo Company.

[0044] Example 1

[0045] A method for preparing ammonia by lithium metal-mediated nitrogen reduction includes the following steps:

[0046] 1) A 316 single-layer stainless steel mesh is used as the supporting electrode and as the working electrode for electroplating. It is connected to the external circuit as the cathode. Two Pt mesh electrodes are used as the counter electrodes, placed opposite the stainless steel mesh on both sides and connected to the external circuit as the anode. The cathode and anode are immersed in a 3M H2SO4 solution containing 10mM H2PtCl6·6H2O and 10mM HAuCl4·3H2O, and an A / cm² pressure is applied. 2 Electroplating was performed at a current density of 80 mg / cm³ for a constant current time of 2 minutes. 2 The PtAu-supported stainless steel mesh was then washed three times alternately with deionized water and ethanol, and dried at 60°C for 12 hours. The resulting PtAu-supported stainless steel mesh was used as the anode catalyst and as the working electrode for electroplating, connected to the external circuit as the anode.

[0047] 2) A double-layer stainless steel mesh was used as the cathode catalyst. The catalyst had 160-micron pores on one side and 30-micron pores on the other side, with the 30-micron pore side facing the electrolyte. The stainless steel mesh was cleaned three times alternately with deionized water and acetone, and finally cleaned once with ethanol. After drying, it was ready for use as the cathode catalyst.

[0048] 3) Dissolve lithium difluorooxalate borate (LiDFOB) in tetrahydrofuran solvent, add ethanol solution, and after stirring, obtain a transparent electrolyte. The electrolyte concentration is controlled at 2M and the ethanol content is controlled at 0.25% by volume.

[0049] 4) Construction of the electrocatalytic ammonia synthesis reactor: A three-chamber flow electrolyzer was used as the electrocatalytic reaction device. The structure of the three-chamber flow electrolyzer includes an anode, a cathode, and an electrolyte. The cathode and anode gas chambers are separated by a 1cm opening in the middle. 2 An 8mm thick PEEK plate with square through-holes has 3mm diameter circular through-holes on both sides to connect the inlet and outlet. The electrolyte chamber uses a flow channel with a 0.5-2mm diameter and a 1cm diameter opening in the middle. 2A 2.5mm thick PEEK plate with square through holes has 3mm diameter circular through holes on both sides of the square holes to connect the gas inlet and outlet. The cathode and anode gas chambers are respectively located on both sides of the electrolyte chamber. The cathode gas chamber includes a gas chamber cavity, the double-layer stainless steel mesh from step 2), and a nitrogen inlet. The anode gas chamber includes a gas chamber cavity, the PtAu-loaded stainless steel mesh from step 1), and a hydrogen inlet. The electrolyte chamber includes a liquid chamber cavity and a Pt metal reference electrode, and the liquid chamber cavity is filled with the aforementioned LiDFOB electrolyte. Both the cathode and anode electrolytes use a 2M LiDFOB tetrahydrofuran solution. 5) High-purity nitrogen is introduced into the cathode gas chamber, and high-purity hydrogen is introduced into the anode gas chamber at a gas flow rate of 75mL / min and an electrolyte flow rate of 0.3mL / min, measured using a 1bar pressure gauge.

[0050] 6) The flow electrolytic cell includes a cathode gas chamber, an anode gas chamber, and an electrolyte chamber. The electrolyte chamber has a liquid flow channel with a width of 1.0 mm. Before electrolysis, nitrogen and hydrogen are introduced into the anode and cathode gas chambers to remove impurities and contaminants. The current density is controlled at 6 mA / cm². 2 The process employs a "deposition-OCV" mode, with a deposition time of 60 seconds, an open-circuit time of 60 seconds, and multiple circulation cycles. The reaction pressure is 1 bar, and the material of the flow reactor is stainless steel.

[0051] 7) The gas obtained after the reaction at the cathode and anode of the reactor is absorbed by 0.2M H2SO4 solution. The resulting electrolyte is absorbed by adding 60ml of 0.2M H2SO4 solution. The nitrogen-containing products on the stainless steel cathode are absorbed by 20ml of aqueous solution.

[0052] Example 2

[0053] In step 6), the current density is controlled at 20 mA / cm². 2 The deposition-OCV mode was adopted, with a deposition time of 5s and an open-circuit time of 30s, and the rest were the same as in Example 1.

[0054] Example 3

[0055] In step 6), the current density is controlled at 50 mA / cm². 2 The deposition-OCV mode was adopted, with a deposition time of 4s and an open-circuit time of 30s, and the rest were the same as in Example 1.

[0056] Example 4

[0057] In step 6), the current density is controlled at 100 mA / cm². 2 The deposition-OCV mode was adopted, with a deposition time of 2s and an open-circuit time of 30s, and the rest were the same as in Example 1.

[0058] Example 5

[0059] In step 6), the "deposition-OCV" mode alternates between 2 seconds of deposition and 30 seconds of OCV, with a controlled application of 150 mA / cm². 2 The current density is the same as in Example 1.

[0060] Example 6

[0061] In step 6), the current density is controlled at 200 mA / cm². 2 The rest is the same as in Example 5.

[0062] Example 7

[0063] In step 6), the current density is controlled at 300 mA / cm². 2 The rest is the same as in Example 5.

[0064] Example 8

[0065] In step 5), the gas flow rate is 50 mL / min, the electrolyte flow rate is 1 mL / min, and the rest is the same as in Example 1.

[0066] Example 9

[0067] In step 5), the gas flow rate is 100 mL / min, the electrolyte flow rate is 3 mL / min, and the rest is the same as in Example 1.

[0068] The products obtained in each embodiment and comparative example were subjected to performance testing, as follows:

[0069] Detection method: Collect the liquid phase containing the product and confirm it by ion chromatography (IC).

[0070] Production rate calculation formula:

[0071]

[0072] Where, n a S is the amount of ammonia produced in the reaction, S is the area of ​​the catalyst used in the reaction, and t is the reaction time.

[0073] Faraday efficiency calculation formula:

[0074]

[0075] Where F is the Faraday constant, n a c is the number of electrons transferred during the formation of 1 mole of ammonia from nitrogen. a The concentration of ammonium ions is detected by ion chromatography, V is the volume of the absorption solution, and Q is the total current.

[0076] Formula for calculating electricity conversion efficiency:

[0077]

[0078] Among them, U NH3 The thermodynamic potential for ammonia oxidation is 1.17 V. total FE is the battery voltage (non-iR compensated) and the Faraday efficiency of the reaction.

[0079] The test results are as follows:

[0080]

[0081]

[0082] From the table above, it can be seen that the yield is 100 mA / cm 2 The current density reaches its maximum at 6-100 mA / cm². 2 At current density, the energy utilization rate is above 20%, and the Faraday efficiency and yield at low current density are not affected by gas flow rate and liquid flow rate.

[0083] like Figure 3 In the range of 6-100 mA / cm 2 At certain current densities, the Faraday efficiency of ammonia can reach 96-98%, and the partial current density can reach 96-98 mA / cm². 2 .

[0084] like Figure 4 In the range of 150-300 mA / cm 2 At certain current densities, the Faraday efficiency of ammonia can reach 30-60%, and the partial current density can reach ~90 mA / cm². 2 .

Claims

1. A LiDFOB electrolyte, characterized in that, The solution includes LiDFOB, an organic solvent, and ethanol. LiDFOB is dissolved in the organic solvent to obtain a solution with a molar concentration of 1–3 M. Ethanol is added, and the amount of ethanol added is controlled to be 0.001–1.0% of the volume of the organic solvent.

2. The LiDFOB electrolyte according to claim 1, characterized in that, The organic solvents include one or more of tetrahydrofuran, dimethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and one or more of ethanol, propanol, butanol, or isopropanol.

3. An electrocatalytic ammonia synthesis reactor, characterized in that, It includes a cathode gas chamber, an anode gas chamber, and an electrolyte chamber. The cathode gas chamber and the anode gas chamber are respectively located on both sides of the electrolyte chamber. The cathode gas chamber is provided with a cathode and a nitrogen gas inlet, and the anode gas chamber is provided with an anode and a hydrogen gas inlet. The electrolyte chamber is filled with the LiDFOB electrolyte as described in claim 1.

4. The electrocatalytic ammonia synthesis reactor according to claim 3, characterized in that, The anode is prepared by the following method: a stainless steel mesh is used as a supporting electrode and as the working electrode for electroplating, connected to an external circuit as the cathode. Two Pt mesh electrodes are used as the counter electrodes, placed opposite the stainless steel mesh on both sides and connected to an external circuit as the anode. The cathode and anode are immersed in a sulfuric acid solution of chloroplatinic acid and chloroauric acid, wherein the molar ratio of Pt, Au, and sulfuric acid is 1:1:200-400, and an A / cm² pressure is applied. 2 Current density, constant current electroplating for 1-5 minutes, controlling the loading of Pt and Au on the supporting electrode to be 40-100 mg / cm³. 2 The prepared stainless steel mesh supported on PtAu was used as the anode catalyst.

5. The electrocatalytic ammonia synthesis reactor according to claim 3, characterized in that, The cathode is a double-layer stainless steel mesh with a pore size of 150-180 micrometers on one side and a pore size of 20-40 micrometers on the other side, with the 20-40 micrometer pore mesh side facing the electrolyte.

6. The electrocatalytic ammonia synthesis reactor according to claim 3, characterized in that, The electrolyte chamber has a liquid flow channel with a width of 0.5 to 2 mm.

7. An application of the electrocatalytic ammonia synthesis reactor described in claim 3 for lithium metal-mediated nitrogen reduction to prepare ammonia, characterized in that, Hydrogen and nitrogen are introduced into the anode and cathode chambers of the electrocatalytic ammonia synthesis reactor, respectively, and the current density applied to the reactor is controlled to be 6–300 mA / cm². 2 The NH3 product was obtained by alternating cyclic electrolytic catalysis using a "deposition-OCV" mode.

8. The application of the lithium metal-mediated nitrogen reduction for ammonia preparation using an electrocatalytic ammonia synthesis reactor according to claim 7, characterized in that, The flow rates of hydrogen and nitrogen gas input into the electrocatalytic ammonia synthesis reactor are controlled at 50-100 mL / min, and the flow rate of electrolyte is controlled at 1-3 mL / min. The "deposition-OCV" mode involves electrolytic deposition for 2–60 seconds, open circuit for 30–60 seconds, and 1–6000 cycles.

9. The application of the lithium metal-mediated nitrogen reduction for ammonia preparation using an electrocatalytic ammonia synthesis reactor according to claim 7, characterized in that, During electrolysis, lithium ions in the electrolyte are deposited layer by layer on the cathode to form a LiF / Li2CO3 / Li3N SEI structure.

10. The application of the lithium metal-mediated nitrogen reduction for ammonia preparation using an electrocatalytic ammonia synthesis reactor according to claim 7, characterized in that, The ammonia gas generated in the tail gas is absorbed by 0.2-0.5M dilute sulfuric acid at both the cathode and anode outlets. 0.2-0.5M dilute sulfuric acid is added to the electrolyte in the electrolyte chamber to absorb the ammonia gas dissolved in the electrolyte. After electrolysis, the cathode catalyst is reacted and absorbed by deionized water to obtain an ammonium ion aqueous solution. Ammonia gas is obtained by heating the above ammonia absorption solution.

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