System and method for efficiently synthesizing ammonia under normal-temperature and normal-pressure conditions

Abstract

The invention belongs to the field of catalytic synthesis, and relates to a method for efficiently synthesizing ammonia under the conditions of normal temperature and normal pressure. N2 and H2 are introduced into the reversible lithium battery, in the discharging process, lithium ions are reduced and deposited on the active metal surface of a cathode, a lithium / metal interface catalyst is constructed in situ, N2 and H2 are converted by the lithium / metal interface catalyst to synthesize a product NH3, and then the catalyst is regenerated in the charging process of the reversible lithium battery, so that continuous generation of NH3 is realized. The lithium / metal interface catalyst based on in-situ construction of the reversible lithium battery in the discharge process provided by the invention can realize efficient catalytic synthesis of NH3 from N2 and H2 at normal temperature and normal pressure. In the process, voltage output can be realized in a catalyst construction stage, and extra energy input is not needed in a synthesis ammonia stage.

Description

Technical Field

[0001] This invention belongs to the field of catalytic synthesis and relates to a method for efficiently synthesizing ammonia under ambient temperature and pressure conditions. Background Technology

[0002] Ammonia (NH3), as a core carrier for maintaining the Earth's nitrogen cycle, has its industrial production efficiency directly related to food security and clean energy storage. The traditional Haber-Bosch ammonia synthesis process, constrained by thermodynamic equilibrium, requires operation under harsh conditions of high temperature and high pressure, resulting in the annual consumption of 1.8% of global fossil fuels and the generation of significant CO2 emissions. Research into a technology capable of synthesizing ammonia under milder conditions has become a key breakthrough in addressing energy and environmental challenges.

[0003] In recent years, electrochemical ammonia synthesis technology coupled with renewable energy sources (solar energy, wind energy, etc.) has been considered the most promising alternative to the traditional Haber-Bosch process. However, this technology faces a double challenge: on the one hand, the extremely high bond energy (941 kJ / mol) of the N≡N triple bond in nitrogen molecules makes activation extremely difficult; on the other hand, the competitive hydrogen evolution reaction (HER) in the aqueous electrolyte system leads to low Faradaic efficiency in ammonia synthesis, which severely restricts the yield and selectivity of ammonia (Guo X, Du H, QuF, et al. Recent progress in electrocatalytic nitrogen reduction[J]. Journal of Materials Chemistry A, 2019, 7(8): 3531-3543.).

[0004] Recent studies have shown that lithium metal possesses a unique ability to activate nitrogen gas at room temperature, enabling efficient activation of nitrogen molecules. Based on this characteristic, lithium-mediated nitrogen reduction provides a new pathway for efficient electrocatalytic ammonia synthesis. However, this system still faces two key challenges: first, the extremely strong reduction potential of lithium metal necessitates a high potential for the reaction, significantly increasing the system's energy consumption; second, the hydrogenation process introduced to maintain a continuous proton supply may trigger side reactions and lead to uncontrolled consumption of active hydrogen species, thereby interfering with ammonia synthesis efficiency (Li S, Fu X, Nørskov JK, et al. Towards sustainable metal-mediated ammoniaelectrosynthesis[J]. Nature Energy, 2024, 9(11): 1344-1349.). Therefore, developing a method for the efficient conversion of N2 and H2 to NH3 at room temperature and pressure is crucial. Summary of the Invention

[0005] The purpose of this invention is to overcome the stringent conditions limiting traditional ammonia synthesis processes by utilizing the in-situ construction of a lithium / metal interface catalyst during the discharge process of a reversible lithium-ion battery, thereby achieving efficient ammonia synthesis from nitrogen and hydrogen under mild conditions. The in-situ catalyst construction based on the reversible lithium-ion battery discharge process enables ammonia preparation without any energy input; simultaneously, catalyst regeneration can be achieved during charging, maintaining continuous ammonia synthesis. This strategy provides a new paradigm for developing modular, low-energy-consumption ammonia synthesis technologies.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: This invention provides a method for efficient ammonia synthesis under ambient temperature and pressure conditions. N2 and H2 are introduced into a reversible lithium battery. During the discharge process, lithium ions are reduced and deposited on the active metal surface of the cathode, and a lithium / metal interface catalyst is constructed in situ. The lithium / metal interface catalyst is used to convert N2 and H2 into the product NH3. Subsequently, the catalyst is regenerated during the charging process of the reversible lithium battery, thereby realizing the continuous generation of NH3.

[0007] Furthermore, the active metal on the cathode is one or more of gold, ruthenium, palladium, and platinum.

[0008] Furthermore, the reversible lithium battery includes a lithium metal anode, a membrane wetted with electrolyte, and a cathode supported on a catalyst.

[0009] Furthermore, the catalyst of the cathode in the reversible lithium battery is obtained by combining an active metal with a multi-walled carbon nanotube support, wherein the active metal is one or more of gold, ruthenium, palladium, and platinum, and the metal content is 5wt%~40wt%.

[0010] Furthermore, the composite method is one or both of the impregnation method and the ball milling method.

[0011] Furthermore, the reversible lithium battery charge / discharge current is 0.1~0.2 mA / cm². -2 The voltage window is 0.7~4.0 V vs. Li. + / Li.

[0012] Furthermore, the volume ratio of N2 to H2 is 3~27:1, and the gas flow rate is 2~20 mL / min.

[0013] Furthermore, during the reaction process, the reaction gas is continuously fed into the reversible lithium battery and collected using a liquid-phase system.

[0014] Furthermore, the liquid-phase circulation system mainly consists of a 0.05 M H2SO4 solution.

[0015] Furthermore, cation chromatography was used to perform qualitative and quantitative analysis of the product NH3.

[0016] The beneficial effects of this invention are as follows: (1) This invention utilizes the discharge process of a reversible lithium battery to construct an active catalyst in situ. This catalyst can achieve efficient activation and conversion of N2 and H2 to NH3, thus improving the ammonia generation rate compared to currently reported ammonia synthesis methods. Specifically, compared to existing lithium-mediated ammonia synthesis systems, its advantages are: a) in-situ construction of the active catalyst at a lower potential; b) ammonia synthesis without any energy input.

[0017] (2) The catalyst of the present invention is constructed in situ using the reversible lithium battery discharge process. The process of synthesizing ammonia is a thermochemical process that not only does not require any energy input, but also is accompanied by voltage output.

[0018] (3) This invention can serve as a potential alternative to the traditional Haber-Bosch ammonia synthesis process. By combining it with a reversible lithium battery, it provides a new possible route for ammonia synthesis under ambient temperature and pressure conditions. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the apparatus for efficient ammonia synthesis under ambient temperature and pressure according to the present invention; Figure 2 The curves for cyclic charging and discharging in Example 1; Figure 3 This is a graph showing the ammonia production during the cyclic charge-discharge process in Example 1; Figure 4 The graph shows the yield of ammonia synthesized in Examples 1-4; Figure 5 The graph shows the ammonia production rates in Examples 1 and 5-7. Figure 6 The graph shows the ammonia production rates in Examples 1 and 8-9. Figure 7 In Example 10 15 Experimental diagram of N2+H2 isotope labeling; In the diagram: 1. Reversible lithium battery, 2. Gas phase system, 3. Product collection system, 101. Cathode, 102. Separator, 103. Anode. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0021] The present invention provides a method for efficient ammonia synthesis at room temperature and pressure, utilizing, for example... Figure 1The apparatus shown includes a reversible lithium battery 1, a gas phase system 2, and a product collection system 3. The reversible lithium battery 1 includes a lithium metal anode 103, a membrane 102 wetted with electrolyte, and a cathode 101 loaded with a catalyst. During discharge, lithium ions are reduced and deposited on the active metal surface of the cathode 101, forming an in-situ lithium / metal interface catalyst. The gas phase system 2 introduces a mixture of N2 and H2 into the reversible lithium battery 1. The liquid phase collection system 3 includes a 0.05 M H2SO4 solution, and the product ammonia is collected in the system. Subsequently, during charging, the reversible lithium battery 1 regenerates the catalyst, achieving continuous catalytic conversion of N2 and H2 to produce NH3.

[0022] Example 1 The method for efficient ammonia synthesis at room temperature and pressure includes the following steps: Step 1: Weigh 700 mg RuCl3 and 400 mg commercial multi-walled carbon nanotubes (purchased from Chengdu Organic Chemical Co., Ltd.), add 40 mL of deionized water, sonicate for 10 minutes, place on a stirring table and stir until the solvent has completely evaporated, then heat at 80°C. o After drying in a C-type forced-air drying oven for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 100°C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min o C, calcined for 2 hours, and cooled to obtain a Ru / CNTs catalyst, wherein the Ru content is 40 wt%; Step 2: Weigh 60 mg of Ru / CNTs catalyst, add 20 mL of ethanol and 1 mL of deionized water, and sonicate for 30 minutes. Add 6 mg of 10 wt% PTFE solution and sonicate for 15 minutes. Spray the prepared ink onto 6 cm × 6 cm commercial carbon paper (TGP-H-060), and then transfer it to 80 °C. o The cathode was obtained by drying it in a vacuum oven for 12 hours. Step 3: The anode is a lithium metal sheet, the electrolyte is LiCF3SO3 / TEGDME (100-200 μL), and the separator is Whatman. The cathode, anode, electrolyte, and separator obtained in Step 2 are assembled into a reversible lithium battery in an Ar atmosphere glove box. Step 4: Introduce a mixture of N2 and H2 gas (N2 to H2 volume ratio of 27:1) into the reversible lithium battery at a flow rate of 20 mL / min; Step 5: Connect the outlet of the reversible lithium battery to a product collection system 3 containing 20 mL of 0.05 M H2SO4; Step 6: After the reversible lithium battery has been stabilized for 12 hours, the battery voltage is between 0.1 and 0.2 mA / cm².-2 The voltage window is 0.7~4.0 V vs. Li. + / Li performs charging and discharging.

[0023] Charge-discharge curves as follows Figure 2 As shown. From Figure 2 It can be seen that Ru / CNTs, as the cathode catalyst of reversible lithium batteries, can achieve stable charge-discharge behavior for 5 consecutive cycles.

[0024] After the reversible lithium battery has finished discharging, 1 mL of solvent from the absorption bottle was taken and analyzed by cation chromatography to quantify the product. The experimental results are as follows: Figure 3 As shown. From Figure 3 It can be seen that Ru / CNTs, as the cathode catalyst of the reversible lithium battery, achieves stable NH3 synthesis during 5 charge-discharge cycles.

[0025] Example 2 The method for efficient ammonia synthesis at room temperature and pressure uses the same preparation method as in Example 1, the difference being the different loading of the active metal Ru on the cathode-supported catalyst, i.e., changing step 1: Weigh 400 mg of multi-walled carbon nanotubes, add 54 mg of RuCl3 and 40 mL of deionized water, ultrasonically disperse for 10 minutes, place on a stirring table and stir until the solvent is completely evaporated, and then dry in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 10 °C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min o C, calcined for 2 hours, and cooled to obtain a Ru / CNTs catalyst, wherein the Ru content was 5 wt%; the remaining steps were the same as in Example 1. Experimental results are as follows: Figure 4 As shown.

[0026] Example 3 The method for efficient ammonia synthesis at room temperature and pressure uses the same preparation method as in Example 1, the difference being the different loading of the active metal Ru on the cathode-supported catalyst, i.e., changing step 1: Weigh 400 mg of multi-walled carbon nanotubes, add 107 mg of RuCl3 and 40 mL of deionized water, ultrasonically disperse for 10 minutes, place on a stirring table and stir until the solvent is completely evaporated, and then dry in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 10 °C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min oC, calcined for 2 hours, and cooled to obtain a Ru / CNTs catalyst, wherein the Ru content was 10 wt%; the remaining steps were the same as in Example 1. Experimental results are as follows: Figure 4 As shown.

[0027] Example 4 The method for efficient ammonia synthesis at room temperature and pressure uses the same preparation method as in Example 1, the difference being the different loading of active metal Ru in the cathode-supported catalyst, i.e., changing step 1: Weigh 400 mg of multi-walled carbon nanotubes, add 270 mg of RuCl3 and 40 mL of deionized water, ultrasonically disperse for 10 minutes, place on a stirring table and stir until the solvent has completely evaporated, and then dry in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 10 °C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min o C, calcined for 2 hours, and cooled to obtain a Ru / CNTs catalyst, wherein the Ru content was 20 wt%; the remaining steps were the same as in Example 1. Experimental results are as follows: Figure 4 As shown.

[0028] Figure 4 The graphs show the yields of NH3 synthesized under different Ru loading cathode catalysts in Examples 1-4. It can be seen that 40wt% Ru / CNTs exhibits the best performance in NH3 synthesis.

[0029] Example 5 The method for efficient ammonia synthesis at room temperature and pressure uses the same preparation method as in Example 1, except that the active metal in the cathode-supported catalyst is Au, i.e., step 1 is changed: 100 mg of multi-walled carbon nanotubes are weighed, 133 mg of tetrachloroauric acid and 40 mL of deionized water are added, ultrasonically dispersed for 10 minutes, and then stirred on a stirring table until the solvent is completely evaporated. The mixture is then dried in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 10 °C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min o C, calcined for 2 hours, and cooled to obtain Au / CNTs catalyst; the remaining steps were the same as in Example 1. Experimental results are as follows: Figure 5 As shown.

[0030] Example 6 The method for efficient ammonia synthesis at room temperature and pressure uses the same preparation method as in Example 1, except that the active metal in the cathode-supported catalyst is Pt, i.e., step 1 is changed: 100 mg of multi-walled carbon nanotubes are weighed, 115 mg of platinum tetrachloride and 40 mL of deionized water are added, ultrasonically dispersed for 10 minutes, and then stirred on a stirring table until the solvent is completely evaporated. The mixture is then dried in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 10 °C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min o C, calcined for 2 hours, and cooled to obtain the Pt / CNTs catalyst; the remaining steps were the same as in Example 1. Experimental results are as follows: Figure 5 As shown.

[0031] Example 7 The method for efficient ammonia synthesis at room temperature and pressure employs the same preparation method as in Example 1, except that the active metal in the cathode-supported catalyst is Pd, i.e., step 1 is changed: 400 mg of multi-walled carbon nanotubes are weighed, 111 mg of palladium chloride and 40 mL of deionized water are added, ultrasonically dispersed for 10 minutes, and then stirred on a stirring table until the solvent is completely evaporated. The mixture is then dried in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated at 10 °C in an atmosphere of 40% H2 and a mixture of H2 and Ar. o Heating rate increased to 250 °C / min o C, calcined for 2 hours, and cooled to obtain the Pd / CNTs catalyst; the remaining steps were the same as in Example 1. Experimental results are as follows: Figure 5 As shown.

[0032] Figure 5 The graphs show the ammonia production yields of different active metal cathode catalysts in Examples 1 and 5-7. It can be seen that, compared with other metals, Ru exhibits higher performance in NH3 synthesis.

[0033] Example 8 A method for efficient ammonia synthesis at room temperature and pressure was developed, employing the same preparation method as in Example 1, except for the volume ratio of the reactants N2 and H2. Specifically, step 4 was changed: a mixture of N2 and H2 gas (N2 to H2 volume ratio 3:1) was introduced into the reversible lithium battery. The remaining steps were the same as in Example 1. Experimental results are as follows: Figure 6 As shown.

[0034] Example 9 A method for efficient ammonia synthesis at room temperature and pressure was developed, employing the same preparation method as in Example 1, except for the volume ratio of the reactants N2 and H2. Specifically, step 4 was changed: a mixture of N2 and H2 gas (N2 to H2 volume ratio 9:1) was introduced into the reversible lithium battery. The remaining steps were the same as in Example 1. Experimental results are as follows: Figure 6 As shown.

[0035] Figure 6 The graphs show the ammonia production under different volume ratios of N2 to H2 in Examples 1 and 8-9. It can be seen that the synthesis of NH3 is optimal when the ratio of N2 to H2 is 27:1.

[0036] Example 10 Step 1: Weigh 700 mg RuCl3 and 400 mg commercial multi-walled carbon nanotubes, add 40 mL of deionized water, sonicate for 10 minutes, place on a stirring table and stir until the solvent has completely evaporated, then dry in a forced-air drying oven at 80°C. o After drying at C for 12 hours, the powder was ground into powder in a mortar and then transferred to a tube furnace. The powder was then heated in an atmosphere of 40% H2 and Ar mixture for 10 hours. o Heat to 250 °C / min o C, calcined for 2 hours, and cooled to obtain Ru / CNTs catalyst; Step 2: Weigh 60 mg of Ru / CNTs catalyst, add 20 mL of ethanol and 1 mL of deionized water, and sonicate for 30 minutes. Add 6 mg of 10 wt% PTFE solution and sonicate for 15 minutes. Spray the prepared ink onto 6 cm × 6 cm commercial carbon paper, and then transfer it to a vacuum oven at 80°C. o Dry at C for 12 hours; Step 3: The lithium battery is assembled in an Ar atmosphere glove box with lithium metal as the anode, LiCF3SO3 / TEGDME (200 μL) as the electrolyte, Whatman membrane as the separator, and Ru / CNTs as the cathode catalyst. Step 4: Use a container with a volume ratio of 27:1 15 A gas bag containing a mixture of N2 and H2 air circulates air into the battery. Step 5: After the battery has been stable for 12 hours, it is discharged at a constant current density.

[0037] After the battery discharged completely, connect the outlet of the gas bag to an absorption bottle containing 10 mL of 0.05 M H₂SO₄ solution. Take 500 μL of the solution from the absorption bottle and perform NMR analysis to qualitatively identify the product. The experimental results are as follows: Figure 7 As shown.

[0038] from Figure 7It can be seen that in the synthesis of ammonia in this system, the source of nitrogen is the introduced reaction gas, rather than the reduction of other impurities.

[0039] Comparative Example 1 Step 1: Weigh 60 mg of CNTs, add 20 mL of ethanol and 1 mL of deionized water, and sonicate for 30 minutes. Add 6 mg of 10 wt% PTFE solution and sonicate for 15 minutes. Spray the prepared ink onto 6 cm × 6 cm commercial carbon paper, and then transfer it to a vacuum oven at 80°C. o Dry at C for 12 hours to obtain the cathode; Step 2: The anode is lithium metal, the electrolyte is LiCF3SO3 / TEGDME (100-200 μL), and the separator is Whatman. The cathode, anode, electrolyte, and separator obtained in Step 1 are assembled into a reversible lithium battery in an Ar atmosphere glove box. Step 3: Introduce a mixture of N2 and H2 gas (N2 to H2 volume ratio of 27:1) into the reversible lithium battery obtained in Step 2 at a flow rate of 20 mL / min. Step 4: Connect the outlet of the reversible lithium battery to a product collection system containing 20 mL of 0.05 M H2SO4 solution; Step 5: After the reversible lithium battery has been stabilized for 12 hours, the battery voltage is between 0.1 and 0.2 mA / cm². -2 The voltage window is 0.7~4.0 V vs. Li. + / Li discharges.

[0040] After the reversible lithium battery has finished discharging, 1 mL of solvent from the absorption bottle was taken and analyzed by cation chromatography to quantify the product. The experimental results are as follows: Figure 5 As shown.

[0041] Comparative Example 2 Step 1: The anode is lithium metal, the electrolyte is LiCF3SO3 / TEGDME (100~200 μL), the separator is Whatman, and the cathode is commercial carbon paper. The reversible lithium battery is assembled in a glove box under Ar atmosphere. Step 2: Introduce a N2 and H2 mixture with a volume ratio of 27:1 into the reversible lithium battery obtained in Step 1 at a flow rate of 20 mL / min. Step 3: Connect the outlet of the reversible lithium battery to a product collection system containing 20 mL of 0.05 M H2SO4 solution; Step 4: After the reversible lithium battery has been stabilized for 12 hours, the battery voltage is between 0.1 and 0.2 mA / cm². -2 The voltage window is 0.7~4.0 V vs. Li. + / Li discharges.

[0042] After the reversible lithium battery has finished discharging, 1 mL of solvent from the absorption bottle is taken for cation chromatography analysis to quantify the product. The experimental results are as follows: Figure 5 As shown.

[0043] Data from Examples 1-10 clearly demonstrate that the lithium / metal interface catalyst proposed in this invention, constructed in situ during the discharge process of a reversible lithium battery, can achieve highly efficient catalytic synthesis of NH3 from N2 and H2 at room temperature and pressure. This process not only achieves voltage output during the interface construction stage but also requires no additional energy input during the ammonia synthesis stage.

[0044] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the scope of protection of the claims of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for efficient ammonia synthesis under ambient temperature and pressure conditions, characterized in that, By introducing N2 and H2 into a reversible lithium battery, lithium ions are reduced and deposited on the active metal surface of the cathode during discharge, and a lithium / metal interface catalyst is constructed in situ. The lithium / metal interface catalyst is used to convert N2 and H2 into the product NH3. Subsequently, the catalyst is regenerated during the charging process of the reversible lithium battery, thereby realizing the continuous generation of NH3.

2. The method according to claim 1, characterized in that, The active metal on the cathode is one or more of gold, ruthenium, palladium, and platinum.

3. The method according to claim 1, characterized in that, The reversible lithium battery includes a lithium metal anode, a membrane impregnated with electrolyte, and a cathode supported on a catalyst.

4. The method according to claim 3, characterized in that, The catalyst of the cathode in the reversible lithium battery is obtained by combining an active metal with a multi-walled carbon nanotube support, wherein the active metal is one or more of gold, ruthenium, palladium and platinum, and the metal content is 5wt%~40wt%.

5. The method according to claim 4, characterized in that, The composite method is one or both of the impregnation method and the ball milling method.

6. The method according to claim 1, characterized in that, The reversible lithium battery has a charge / discharge current of 0.1~0.2 mA / cm². -2 The voltage window is 0.7~4.0 V vs. Li. + / Li.

7. The method according to claim 1, characterized in that, The volume ratio of N2 to H2 is 3~27:1, and the gas flow rate is 2~20 mL / min.

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