Composite proton membrane, preparation method thereof and application of composite proton membrane in synthesis of ammonia

Abstract

The invention provides a composite proton membrane, a preparation method thereof and application of ammonia synthesis. The composite proton membrane comprises a carbon layer, a palladium layer arranged on at least one side of the carbon layer, and an active substance layer arranged on the partial surface, away from the carbon layer, of the palladium layer, and the active material layer comprises a group VIII element. The composite proton membrane can efficiently and stably synthesize ammonia as an electrochemical catalyst, and has excellent stability.

Description

Technical Field

[0001] This invention relates to a composite proton exchange membrane, and more particularly to a composite proton exchange membrane, its preparation method, and its application in ammonia synthesis, belonging to the field of ammonia synthesis technology. Background Technology

[0002] Ammonia synthesis is an important branch of the chemical industry, widely used in the production of nitrogen fertilizers, fibers, explosives, and other products. Electrocatalytic ammonia synthesis technology using nitrogen and water as raw materials under mild conditions is considered a revolutionary technology for the future of ammonia synthesis.

[0003] Electrocatalytic ammonia synthesis technology still faces significant challenges. Due to the non-polar nature of nitrogen, the solubility of nitrogen in currently explored electrolyte systems is not high, thus limiting the mass transfer process. Traditional two-phase electrocatalytic ammonia synthesis technologies can address this by adding alkali metal cations, such as Li. + Na + K + One approach is to increase the solubility of N2 by enhancing association with N2 molecules. However, this method offers limited improvement in solubility and cannot avoid hydrogen evolution competition reactions, which can further affect the subsequent separation and detection of NH3. Alternatively, solutions with relatively high solubility for nitrogen, such as ionic liquids and tetrahydrofuran, can be used as electrolytes. However, these electrolytes are volatile and easily decompose under applied voltage. Some organic electrolytes are highly toxic, and since the boiling points of NH3 and organic electrolytes are close, subsequent separation and purification costs are high.

[0004] To address the problems of traditional two-phase systems, a three-phase system can be used for electrocatalytic ammonia synthesis, directly utilizing nitrogen molecules from the air to achieve the ammonia synthesis reaction, thus avoiding the issue of poor nitrogen solubility. Patent document CN111394740A discloses a method for improving the efficiency of electrocatalytic nitrogen reduction ammonia synthesis. This method employs a three-phase reaction, using a gas diffusion electrode as the cathode. The apparatus includes a gas diffusion electrode, a reference electrode, a salt bridge, a perfluorosulfonic acid proton exchange membrane, a counter electrode, an anode chamber, a cathode chamber, and a gas chamber. The reference electrode is placed in the cathode chamber, and the counter electrode is placed in the anode chamber. The cathode chamber is connected to both the anode chamber and the gas chamber. A perfluorosulfonic acid proton exchange membrane is placed at the connection between the anode chamber and the cathode chamber, and a gas diffusion electrode is placed at the connection between the cathode chamber and the gas chamber. The gas diffusion electrode has a catalyst layer / current collector or microporous layer / gas diffusion layer sandwich structure, with the side of the gas diffusion electrode coated with catalyst material facing the cathode chamber. Patent document CN117230488A discloses an electrochemical ammonia synthesis device and a method and application of synthesizing ammonia using the device. The device includes a cathode flow channel plate, a cathode layer, a diaphragm, a lithium sheet, and an anode conductive plate arranged in sequence. Each component is detachably connected to form a single unit. The cathode flow channel plate has an inlet and an outlet channel communicating with the outside. A gas flow channel is provided on the surface of the cathode flow channel plate in contact with the cathode layer, communicating with the inlet and outlet channels of the cathode flow channel plate, and the gas in the gas flow channel contacts the cathode layer. The cathode layer includes a cathode electrode sheet and a cathode catalyst layer located on the surface of the cathode electrode sheet. This electrochemical ammonia synthesis device can achieve cyclic ammonia synthesis through a simple process flow, with high efficiency and yield, and realizes the recycling of lithium.

[0005] However, the efficiency and stability of existing ammonia synthesis technologies are relatively poor. Therefore, exploring efficient and stable ammonia synthesis technologies to overcome the shortcomings of existing technologies has significant application value. Summary of the Invention

[0006] This invention provides a composite proton exchange membrane, which is a multilayer metal composite structure and can be used as an electrochemical catalyst to efficiently and stably synthesize ammonia with excellent stability.

[0007] This invention provides a method for preparing a composite proton exchange membrane. The method is simple to operate and can prepare the aforementioned composite proton exchange membrane.

[0008] This invention provides an ammonia synthesis reactor that uses the aforementioned composite proton exchange membrane as the cathode to generate ammonia on the surface of the composite proton exchange membrane, while facilitating the separation and detection of ammonia products.

[0009] This invention provides a method for synthesizing ammonia, which can achieve stable and efficient ammonia synthesis and promote the further application of electrocatalytic ammonia synthesis.

[0010] The present invention provides a composite proton exchange membrane, comprising a carbon layer, a palladium layer disposed on at least one side of the carbon layer, and an active material layer disposed on a portion of the surface of the palladium layer away from the carbon layer; the active material layer comprises a Group VIII element.

[0011] In the composite proton exchange membrane described above, the thickness of the palladium layer is 5-10 micrometers.

[0012] In the composite proton exchange membrane described above, the active material layer accounts for 0.1%-5.5% of the mass percentage of the composite proton exchange membrane.

[0013] The composite proton exchange membrane described above is prepared by a method comprising the following steps:

[0014] After activating carbon paper impregnated with palladium salt solution using a reducing agent solvent, the activated intermediate is subjected to palladium plating to obtain a palladium-plated intermediate; the palladium-plated intermediate is then impregnated with a solution including an active metal salt and an organic ligand, followed by calcination to obtain the composite proton exchange membrane.

[0015] In another aspect, the present invention provides a method for preparing the composite proton exchange membrane as described above, comprising the following steps:

[0016] 1) After impregnating the carbon paper in a palladium salt solution, it is then activated in a reducing agent solution to obtain the activated product;

[0017] 2) The activated product was placed in a palladium plating solution at 25-80℃ for palladium plating treatment, and then washed until the pH was 6-8 to obtain the palladium plating intermediate;

[0018] 3) The palladium plating intermediate is impregnated using a solution mixture system including active metal salts and organic ligands, followed by calcination to obtain the composite proton exchange membrane.

[0019] The preparation method described above further includes performing step 1) n times, where n≥1, before the palladium plating treatment.

[0020] The preparation method described above, wherein the active metal salt comprises at least one selected from nitrates, sulfates, chlorides, and acetates; and / or,

[0021] The organic ligand comprises at least one of o-phenanthroline, 2,2-bipyridine, melamine, and phenylalanine; and / or,

[0022] The molar ratio of the active metal salt to the organic ligand is 1:5 to 1:35; and / or,

[0023] The molar concentration of the active metal salt in the solution mixture is 0.01-0.2 mol·L⁻¹. -1 ; and / or,

[0024] The molar concentration of the organic ligand in the solution mixture does not exceed 4 mol·L⁻¹ -1 .

[0025] In the preparation method described above, the protective atmosphere for calcination includes an argon atmosphere and / or a nitrogen atmosphere;

[0026] The calcination process involves a heating rate of 2–10 °C / min, a temperature of 300–800 °C, and a time of 1–5 hours.

[0027] In another aspect, the present invention provides an ammonia synthesis reactor, comprising an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber, wherein an exchange membrane is disposed between the cathode electrolyte reaction chamber and the anode reaction chamber; and a composite proton exchange membrane as described above or a composite proton exchange membrane prepared by the preparation method described above is disposed between the cathode electrolyte reaction chamber and the cathode gas reaction chamber.

[0028] In another aspect, the present invention provides a method for synthesizing ammonia, which is carried out using the ammonia synthesis reactor described above; wherein nitrogen gas is introduced into the cathode gas reaction chamber as a nitrogen source, and an electrolyte solution is introduced into the anode reaction chamber and the cathode electrolyte reaction chamber to conduct charge and provide protons.

[0029] The composite proton exchange membrane of the present invention has a specific structure and can be used as an electrochemical catalyst to efficiently and stably synthesize ammonia with excellent stability.

[0030] The present invention provides a method for preparing the composite proton membrane, which is simple to operate and can prepare the above-mentioned composite proton membrane.

[0031] The ammonia synthesis reactor of the present invention uses the above-mentioned composite proton membrane as the cathode. The cathode membrane generates protons under electroreduction conditions. Utilizing the hydrogen permeability of the composite proton membrane, the protons are transferred from the liquid phase to the gas phase side through the composite proton membrane and adsorbed on the surface of the composite proton membrane as a proton source for ammonia synthesis. At the same time, it facilitates the separation and detection of ammonia products.

[0032] The ammonia synthesis method of the present invention introduces nitrogen gas as a nitrogen source into the mobile phase gas path, and introduces electrolyte solution into the anode reaction chamber and the cathode electrolyte reaction chamber to conduct charge and provide protons, and reacts to generate ammonia at the composite proton membrane. This method can achieve stable and efficient ammonia synthesis and promote the further application of electrocatalytic ammonia synthesis. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a synthetic ammonia reactor provided in a specific embodiment of the present invention;

[0034] Figure 2The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Example 1 of this invention;

[0035] Figure 3 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Example 2 of this invention;

[0036] Figure 4 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Example 3 of this invention;

[0037] Figure 5 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Example 4 of this invention;

[0038] Figure 6 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Example 5 of this invention;

[0039] Figure 7 The electrode potential-current density curves for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Examples 1 and 6 of this invention;

[0040] Figure 8 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Comparative Example 1 of this invention;

[0041] Figure 9 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Comparative Example 2 of this invention;

[0042] Figure 10 The electrode potential-current density curve for electrocatalytic ammonia synthesis in the ammonia synthesis reactor provided in Comparative Example 3 of this invention;

[0043] Figure 11 The electrocatalytic ammonia synthesis cycle curves in the ammonia synthesis reactors provided in Examples 1 and 3 of this invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] The present invention provides a composite proton exchange membrane, comprising a carbon layer, a palladium layer disposed on at least one side of the carbon layer, and an active material layer disposed on a portion of the surface of the palladium layer away from the carbon layer; the active material layer comprises a Group VIII element.

[0046] In detail, the composite proton membrane provided by the present invention has a multilayer structure. This composite proton membrane is used in the field of ammonia synthesis technology and can significantly improve the efficiency of ammonia synthesis.

[0047] Specifically, the composite proton exchange membrane includes a carbon layer, a palladium layer disposed on at least one side of the carbon layer, the palladium layer being composed of elemental palladium, and an active material layer disposed on the surface of the palladium layer away from the carbon layer.

[0048] In one specific embodiment, palladium layers are provided on both sides of the carbon layer. For ease of distinction, they can be referred to as the first palladium layer and the second palladium layer. An active material layer is provided on the surface of the first palladium layer and / or the second palladium layer away from the carbon layer. The active material layer does not completely cover the palladium layer, but is distributed in an island-like pattern on the surface of the palladium layer.

[0049] The active material layer includes Group VIII elements, such as Fe and Ru.

[0050] In one specific embodiment, the active material layer includes Ru.

[0051] The composite proton exchange membrane of the present invention is used in the field of ammonia synthesis technology. Ammonia synthesis is an important branch of the chemical industry and is widely used in the production of nitrogen fertilizers, fibers, explosives and other products.

[0052] The composite proton exchange membrane of the present invention overcomes the transport limitations of gaseous reactants in the electrolyte system by changing the reaction environment, thereby improving the efficiency of ammonia synthesis and facilitating product separation.

[0053] The composite proton exchange membrane of this invention is a multi-layered metal composite structure consisting of a gas diffusion layer, a palladium crystal layer, a palladium layer, and an active layer. This system provides a stable gas-solid interface structure, enabling efficient ammonia synthesis. The inventors speculate that this is due to several factors: First, the composite proton exchange membrane provided by this invention can efficiently supply nitrogen molecules at the catalyst interface, avoiding the problems of low mass transfer rate and low mass transfer flux encountered in liquid-phase mass transfer. Second, the three-phase interface system constructed using the composite proton exchange membrane is more stable than traditional gas diffusion layer electrodes, preventing water flooding during long-term operation and thus avoiding damage to the three-phase interface and a reduction in reaction rate. Third, the palladium membrane has excellent hydrogen permeability. Under the influence of an electric field, hydrogen protons generated from water decomposition can pass through the palladium membrane to the gas phase side. The elements in the active material layer provide abundant active sites for nitrogen adsorption and ammonia synthesis. After hydrogen protons pass through the palladium membrane to the gas phase side, they combine with nitrogen molecules on the surface of the active material layer to generate ammonia. The ammonia molecules then desorb and leave the gas phase for collection.

[0054] Furthermore, in one specific embodiment of the present invention, the thickness of the palladium layer is 5-10 micrometers.

[0055] In detail, the thickness of the palladium layer includes, but is not limited to, a range of 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, or any combination thereof.

[0056] When the thickness of the palladium layer meets the above range, the stability of the gas-solid two-phase reaction can be guaranteed.

[0057] Furthermore, in one specific embodiment of the present invention, the active material layer accounts for 0.1%-5.5% of the mass percentage of the composite proton exchange membrane.

[0058] The active substance layer accounts for a percentage of the mass of the composite proton exchange membrane, including but not limited to 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5.0%, 5.5%, or any combination thereof.

[0059] Furthermore, in one embodiment of the present invention, the above-mentioned composite proton membrane is prepared by a method comprising the following process:

[0060] After activating carbon paper impregnated with palladium salt solution using a reducing agent solvent, the activated intermediate is subjected to palladium plating to obtain a palladium-plated intermediate; the palladium-plated intermediate is then impregnated with a solution including an active metal salt and an organic ligand, followed by calcination to obtain the composite proton exchange membrane.

[0061] Specifically, the carbon layer of the composite proton exchange membrane is a carbon paper layer. The carbon paper is impregnated with a palladium salt solution and then activated using a reducing agent solution to obtain an activated intermediate. Subsequently, the activated intermediate is subjected to palladium plating to form a palladium layer on the surface of the carbon layer, resulting in a palladium-plated intermediate. Then, the palladium-plated intermediate is impregnated with a solution including an active metal salt and an organic ligand to form an active material layer, thus obtaining the aforementioned composite proton exchange membrane.

[0062] A second aspect of the present invention provides a method for preparing the above-mentioned composite proton membrane, comprising the following steps:

[0063] 1) After impregnating the carbon paper in a palladium salt solution, it is then activated in a reducing agent solution to obtain the activated product;

[0064] 2) The activated product was placed in a palladium plating solution at 25-80℃ for palladium plating treatment, and then washed until the pH was 6-8 to obtain the palladium plating intermediate;

[0065] 3) The palladium plating intermediate is impregnated using a solution mixture system including active metal salts and organic ligands, followed by calcination to obtain the composite proton exchange membrane.

[0066] This invention does not limit the specific experimental parameters and materials of the preparation method, as long as a composite proton membrane with a multilayer metal composite structure can be prepared.

[0067] Specifically, the carbon paper was immersed in a solution containing palladium chloride (PdCl2) for 30 minutes, then rinsed with deionized water, and subsequently placed in a reducing agent Sn. 2+ In the solution, gently shake and reduce for 2-3 minutes, then remove and rinse the carbon paper surface again with deionized water. The activated carbon paper is then placed in deionized water at room temperature and washed until the pH is neutral to obtain the activation product.

[0068] The activated product is placed in a palladium plating solution [Pd(NH3)2Cl2] at 25-80℃ and deposited for 20-30 minutes with a magnetic stirrer, depending on the required coating thickness. The carrier surface first changes from gray to black, and then to a bright silver metallic luster. Bubbles are generated throughout the process until the palladium coating is complete. The substrate is then washed with deionized water until the pH reaches 6-8, thus completing the palladium film plating process and yielding the palladium plating intermediate.

[0069] A certain amount of active metal salt, organic ligand and organic solvent are weighed and mixed to obtain a solution. The solution is used to impregnate at least one surface of the palladium plating intermediate, followed by calcination treatment to obtain the composite proton membrane.

[0070] In addition, the carbon paper can be pretreated before activation. Gas diffusion layer carbon paper is selected as the carrier and soaked in anhydrous ethanol for 30 minutes to remove surface contaminants such as dust and grease. Then, the carbon paper is rinsed with deionized water, dried under an infrared lamp for about 10 minutes, and finally placed in an oven to dry at 60°C for 4 hours. The paper is then cut to a size of 1.5*1cm. 2 Save for later use;

[0071] The preparation method of this invention uses an impregnation method to composite palladium and an active metal onto carbon paper for a gas diffusion layer, resulting in a multi-layer structure on the surface of the gas diffusion layer. The method is simple, readily available, and environmentally friendly.

[0072] In one embodiment, prior to the palladium plating process described above, step 1) is performed n times, where n ≥ 1.

[0073] Specifically, the carbon paper was immersed in a solution containing palladium chloride (PdCl2) for 30 minutes, then rinsed with deionized water, and subsequently placed in a reducing agent Sn. 2+ In the solution, gently shake and reduce for 2-3 minutes, then remove and rinse the carbon paper surface again with deionized water. Repeat the above seeding process until the carbon paper surface is a uniform dark gray. This preparation method ensures that the activation product is fully activated, which is beneficial for subsequent palladium plating.

[0074] In one specific embodiment, the active metal salt includes at least one selected from nitrates, sulfates, chlorides, and acetates. This type of metal salt is common, readily available, and easy to prepare.

[0075] In another specific embodiment, the organic ligand includes at least one of o-phenanthroline, 2,2-bipyridine, melamine, and phenylalanine. This type of organic ligand can, in principle, form a "Schiff base structure" with a metal, which is a mononuclear ligand structure and, after high-temperature calcination, can form a stable single-atom supported catalyst.

[0076] In another specific embodiment, the molar ratio of the active metal salt to the organic ligand is 1:5 to 1:35.

[0077] In detail, the molar ratio of the active metal salt to the organic ligand includes, but is not limited to, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, or any combination thereof.

[0078] When the molar ratio of active metal salt to organic ligand is within the above range, it helps to form a high-load catalyst. When the concentration of active metal salt is higher, metal agglomeration may occur, and the catalyst activity will decrease. When the concentration of active metal salt is lower, the catalyst loading is low and the catalyst activity is insufficient.

[0079] In another specific embodiment, the molar concentration of the active metal salt in the solution mixture is 0.01-0.2 mol·L⁻¹. -1 .

[0080] Specifically, based on the total volume of the solution, the molar concentration of the active metal salt includes, but is not limited to, 0.01 mol·L⁻¹. -1 0.02 mol·L -1 0.04 mol·L -1 0.06 mol·L -1 0.08 mol·L -1 0.10 mol·L -1 0.12 mol·L -1 0.14 mol·L -1 0.16 mol·L -1 0.18 mol·L -1 0.20 mol·L⁻¹ 1 Or the range formed by any two of them.

[0081] When the molar concentration of the active metal salt in the solution mixture is within the above range, the loading can be further guaranteed.

[0082] In another specific embodiment, the molar concentration of the organic ligand in the solution mixture does not exceed 4 mol·L⁻¹. -1 .

[0083] Specifically, based on the total volume of the solution, the molar concentration of the organic ligand does not exceed 4 mol·L⁻¹. -1 .

[0084] Furthermore, in one specific embodiment of the present invention, the protective atmosphere for calcination includes an argon atmosphere and / or a nitrogen atmosphere, which are chemically stable and do not react with metals, thus providing effective protection.

[0085] In another specific embodiment, the calcination heating rate is 2-10°C / min, the temperature is 300-800°C, and the time is 1-5 hours.

[0086] In detail, the heating rate of the calcination treatment includes, but is not limited to, a range of 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or any combination thereof; the temperature includes, but is not limited to, a range of 300, 400, 500, 600, 700, 800, or any combination thereof; and the time includes, but is not limited to, a range of 1h, 2h, 3h, 4h, 5h, or any combination thereof.

[0087] In one specific embodiment, the palladium-plated intermediate after impregnation treatment is heated to the calcination temperature at a rate of 5°C / min, and the calcination temperature is 600°C for 5 hours.

[0088] In addition, the calcination process includes a drying process, which is a heat drying process. In one specific embodiment, the palladium-plated intermediate after impregnation is heated in a water bath at 60°C for 4 hours, and then kept at 80°C in an oven for 12 hours.

[0089] This preparation method ensures that each metal layer of the composite proton exchange membrane is thoroughly dried, enabling it to be firmly bonded to the carbon paper in the gas diffusion layer, thus achieving a stable catalytic effect for ammonia synthesis.

[0090] The composite proton membrane obtained by this preparation method has a more stable gas-solid interface structure compared to the three-phase electrocatalytic reaction system constructed with porous carbon paper, which can achieve long-term ammonia synthesis.

[0091] A third aspect of the present invention provides an ammonia synthesis reactor. Figure 1 The diagram shows the apparatus of the present invention, which includes an anode reaction chamber 4, a cathode electrolyte reaction chamber 5, and a cathode gas reaction chamber 6. An exchange membrane 7 is disposed between the cathode electrolyte reaction chamber 5 and the anode reaction chamber 4. The composite proton exchange membrane 8 described above is disposed between the cathode electrolyte reaction chamber 5 and the cathode gas reaction chamber 6.

[0092] Specifically, an exchange membrane 7, including but not limited to a proton exchange membrane, anion exchange membrane, and cation exchange membrane, is disposed between the cathode electrolyte reaction chamber 5 and the anode reaction chamber 4; the aforementioned composite proton membrane 8 is disposed between the cathode electrolyte reaction chamber 2 and the cathode gas reaction chamber 6, with the side of the composite proton membrane 5 impregnated with the active layer facing the cathode gas reaction chamber 6; a counter electrode 9 is disposed in the anode reaction chamber 4, including but not limited to a platinum sheet electrode or a graphite electrode; the counter electrode 9 is connected to the positive terminal of the power supply 10, and the composite proton membrane 8 is connected to the negative terminal of the power supply 10. The electrolyte in the anode reaction chamber 6 releases charge and conducts it to the cathode electrolyte reaction chamber 5. The electrolyte in the cathode electrolyte reaction chamber 5 receives charge and generates protons under electroreduction conditions. Utilizing the hydrogen permeability property of the composite proton membrane 8, the protons permeate through the composite proton membrane 5 from the cathode electrolyte reaction chamber 2 to the cathode gas reaction chamber 6, adsorbing on the surface of the composite proton membrane 8 as a proton source for ammonia synthesis.

[0093] The ammonia synthesis reactor of this invention adopts a composite proton exchange membrane design, which physically isolates nitrogen and water while allowing them to undergo an electrochemical reaction to generate ammonia, thus avoiding the problem of subsequent separation of ammonia products and electrolytes.

[0094] A fourth aspect of the present invention provides a method for synthesizing ammonia, utilizing the aforementioned ammonia synthesis reactor; wherein nitrogen gas is introduced into the cathode gas reaction chamber 6 as a nitrogen source, and an electrolyte solution is introduced into the anode reaction chamber 4 and the cathode electrolyte reaction chamber 5 to conduct charge and provide protons. Specifically, the electrolyte in the cathode electrolyte reaction chamber 5 gains charge and generates protons under electroreduction conditions, which permeate through the composite proton exchange membrane 8 and adsorb onto the surface of the composite proton exchange membrane 8. Nitrogen gas is introduced into the cathode gas reaction chamber 6, and the nitrogen gas reacts continuously with the protons at the composite proton exchange membrane 8 to generate ammonia.

[0095] The ammonia synthesis method of this invention avoids the process of nitrogen dissolving in water before participating in the reaction. Nitrogen in the gas phase can directly reach the catalyst surface, and the mass transfer efficiency of nitrogen molecules is high, which can promote the forward reaction of ammonia synthesis.

[0096] The following detailed description of the composite proton exchange membrane, its preparation method, and its ammonia synthesis method of the present invention will be provided through specific embodiments.

[0097] Example 1

[0098] The preparation method of the composite proton membrane in this embodiment includes the following steps:

[0099] 1) Gas diffusion layer carbon paper, specifically Freudenberg H14C9, was selected as the carrier. It was soaked in anhydrous ethanol for 30 minutes to remove surface contaminants such as dust and grease. The carbon paper was then rinsed with deionized water, dried under an infrared lamp for 10 minutes, and finally placed in an oven at 60°C for 4 hours. The paper was then cut to a size of 1.5 x 1 cm. 2 Save for later use.

[0100] 2) Immerse the carbon paper in a palladium chloride (PdCl2) solution for 30 minutes. After removal, rinse the surface with deionized water, then place it in a reducing agent solution for activation treatment. Gently agitate and reduce for 3 minutes, then remove and rinse the carbon paper surface again with deionized water. Repeat the above immersion-activation process until a uniform palladium crystal layer forms on the surface of the carbon paper. Wash the activated carbon paper in deionized water at room temperature until the pH is neutral to obtain the activated product; wherein the concentration of the palladium chloride solution is 0.1 mol / L. -1 The reducing agent solution is Sn. 2+ Solution, concentration 1 mol L -1 .

[0101] 3) The activated product is placed in a palladium plating solution [Pd(NH3)2Cl2] preheated to 70°C, wherein the Pd ion concentration is 1 mol / L. -1 Under the stirring of a magnetic stirrer, the coating was carried out for 30 minutes until the palladium layer was completed. Then, it was washed with deionized water until neutral to obtain the palladium intermediate.

[0102] 4) Weigh 0.322 g of ruthenium acetate, 7.2 g of o-phenanthroline, and 10 mL of dimethyl sulfoxide, mix thoroughly, and then impregnate one side of the palladium plating intermediate for 30 min. After impregnation, perform a calcination treatment under an argon atmosphere for 5 hours at an argon flow rate of 10 mL / min. -1 The calcination temperature was 600℃, and the heating rate was 5℃ / min. After calcination, the carbon paper was heated and dried, and kept at 80℃ in an oven for 12 hours, and an active layer was formed on the surface to obtain composite proton membrane 1.

[0103] In composite proton exchange membrane 1, the palladium layer has a thickness of 8 micrometers, and the active material layer has a mass percentage content of 3.7%.

[0104] The ammonia synthesis reactor in this embodiment includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 1 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 1 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0105] Example 2

[0106] The difference between Example 2 and Example 1 is that ruthenium acetate in Example 1 is replaced with ferric acetate, while the rest are the same, resulting in composite proton membrane 2.

[0107] In composite proton exchange membrane 2, the palladium layer has a thickness of 8 micrometers, and the active material layer has a mass percentage of 3.7%.

[0108] The ammonia synthesis reactor in this embodiment includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 2 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 2 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0109] Example 3

[0110] The difference between Example 3 and Example 1 is that the o-phenanthroline in Example 1 was replaced with 2,2-bipyridine, while the rest were the same, resulting in composite proton membrane 3.

[0111] The palladium layer in composite proton exchange membrane 3 is 8 micrometers thick, and the loading of the active material layer is 3.7%.

[0112] The ammonia synthesis reactor in this embodiment includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 3 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 3 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0113] Example 4

[0114] The difference between Example 4 and Example 1 is that: ruthenium acetate is 0.966g, o-phenanthroline is 21.6g, and the rest are the same, resulting in composite proton membrane 4.

[0115] In composite proton exchange membrane 4, the palladium layer is 8 micrometers thick, and the loading of the active material layer is 10.8%.

[0116] The ammonia synthesis reactor in this embodiment includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 4 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 4 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0117] Example 5

[0118] The difference between Example 5 and Example 1 is that:

[0119] The activated product was placed in a palladium plating solution [Pd(NH3)2Cl2] preheated to 70°C, wherein the Pd ion concentration was 1.5 mol / L. -1Under magnetic stirring, the coating process lasted for 30 minutes until the palladium layer was complete. The mixture was then washed with deionized water until neutral to obtain the palladium intermediate. The palladium layer in composite proton exchange membrane 5 was 12 micrometers thick, and the loading of the active material layer was 5.5%.

[0120] The ammonia synthesis reactor in this embodiment includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 5 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 5 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0121] Example 6

[0122] The difference between Example 6 and Example 1 is that the calcination temperature rise rate in Example 1 was 5℃ / min, while in Example 1 it was changed to 12℃ / min, and all other conditions remained the same, resulting in composite proton membrane 6.

[0123] In composite proton exchange membrane 6, the palladium layer is 8 micrometers thick, and the active material layer contains 3.7% by mass.

[0124] The ammonia synthesis reactor in this embodiment includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 6 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 6 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0125] Comparative Example 1

[0126] The difference between Comparative Example 1 and Example 1 is that the ammonia synthesis reactor in this comparative example is an H-type reactor, which includes a reaction tank and a Nafion 117 proton exchange membrane. The reaction tank is divided into an anode reaction chamber and a cathode reaction chamber, which are separated by the proton exchange membrane.

[0127] Comparative Example 2

[0128] The gas diffusion electrode is prepared according to the following steps:

[0129] (1) The carbon paper for the gas diffusion layer (Shanghai Hesen) was repeatedly cleaned with acetone and anhydrous ethanol to remove surface oil stains. After drying, it was cut into pieces of 3*3cm size. 2 spare;

[0130] (2) Weigh a certain amount of commercial tungsten oxide and dissolve it in 1-2 mL of a mixed solvent of isopropanol and Nafion with a volume ratio of 95:5. Disperse it ultrasonically for 30 min to obtain a uniformly dispersed slurry.

[0131] (3) The slurry obtained in step (2) is drop-coated onto the center of the gas diffusion layer carbon paper obtained in step (1) to form a gas diffusion electrode with a sandwich structure of catalyst layer / current collector (microporous layer) / hydrophobic and breathable layer, and the catalyst loading is 1-2 mg / cm³. 2 .

[0132] The ammonia synthesis reactor of this comparative example includes a reaction tank, a Nafion 117 proton exchange membrane, and a gas diffusion electrode prepared in this comparative example. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the gas diffusion electrode is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0133] Comparative Example 3

[0134] The method for preparing the composite proton membrane provided in this comparative example includes the following steps:

[0135] 1) Gas diffusion layer carbon paper, specifically Freudenberg H14C9, was selected as the carrier. It was soaked in anhydrous ethanol for 30 minutes to remove surface contaminants such as dust and grease. The carbon paper was then rinsed with deionized water, dried under an infrared lamp for 10 minutes, and finally placed in an oven at 60°C for 4 hours. The paper was then cut to a size of 1.5 x 1 cm. 2 Save for later use.

[0136] 2) Weigh 0.322 g of ruthenium acetate, 7.2 g of o-phenanthroline, and 10 mL of dimethyl sulfoxide, mix thoroughly, and then impregnate one side of carbon paper for 30 min. After impregnation, perform a calcination treatment under an argon atmosphere for 5 hours at an argon flow rate of 10 mL / min. -1 The calcination temperature was 600℃, and the heating rate was 5℃ / min. After calcination, the carbon paper was heated and dried, and kept at 80℃ in an oven for 12 hours, during which an active layer was formed on the surface, thus obtaining a composite proton exchange membrane.

[0137] The active material layer in the composite proton exchange membrane has a mass percentage of 3.9%.

[0138] The ammonia synthesis reactor in this comparative example includes a reaction tank, a Nafion 117 proton exchange membrane, and a composite proton membrane 1 prepared in this embodiment. The reaction tank is divided into an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber. One side of the proton exchange membrane is the anode reaction chamber, and the other side is the cathode electrolyte reaction chamber. One side of the composite proton membrane 1 is the cathode electrolyte reaction chamber, and the other side is the cathode gas reaction chamber.

[0139] Test case

[0140] 1. Catalytic efficiency test

[0141] Ammonia synthesis was carried out using the ammonia synthesis reactors provided in all the embodiments and comparative examples, wherein a Pt sheet electrode was used as the anode, a silver / silver chloride electrode as the cathode, and a composite proton exchange membrane was used as the cathode. Argon gas was introduced to measure the current density in the reactor, and nitrogen gas was introduced into the cathode gas reaction chamber at a flow rate of 1 ml / min. -1 Both the cathode electrolyte chamber and the anolyte chamber are purged with 0.05 mol L⁻¹ -1 The current density in the reactor was measured using an H2SO4 solution. The current density under the same voltage conditions with nitrogen gas was significantly higher than that with argon gas, proving that the ammonia synthesis reaction did indeed occur. Figures 2-10 Electrode potential-current density curves of the ammonia synthesis reaction in the ammonia synthesis reactors provided for various embodiments and comparative examples.

[0142] Depend on Figure 2 and Figure 3 It can be seen that when the absolute value of the electrode potential is greater than 0.6V, under the same electrode potential, the absolute value of the current density using ruthenium is always greater than the absolute value of the current density using iron. This indicates that when the electrode undergoes the same degree of redox reaction, the electrocatalytic efficiency of the active layer material of the composite proton membrane using ruthenium is higher than that using iron.

[0143] Depend on Figures 2-7 and Figure 8 , Figure 9 , Figure 10 It can be seen that, under the same electrode potential, the absolute value of the current density of the ammonia synthesis reactor provided in Examples 1-6 is always not less than the absolute value of the current density of the ammonia synthesis reactor provided in Comparative Examples 1-3. This indicates that when the electrodes undergo the same degree of redox reaction, the electrocatalytic efficiency of the ammonia synthesis reactor provided by the present invention is higher than that of the ammonia synthesis reactor provided in Comparative Examples 1-3.

[0144] 2. Catalytic stability test

[0145] Control current density is 5 mA cm⁻¹ -2 A constant current test was performed, and an electrocatalytic ammonia synthesis experiment was conducted under these conditions. The voltage change data over time was observed and recorded, as detailed in Table 1. Figure 11 The electrocatalytic ammonia synthesis cycle curves in the ammonia synthesis reactors provided in Example 1 and Comparative Example 3 are shown.

[0146] Table 1

[0147]

[0148] As shown in Table 1, the operating conditions for the electrocatalytic ammonia synthesis experiment were 1.1V vs RHE. After running for 600 minutes, the decay rate of the composite proton membranes provided in Examples 1-6 of this invention was no higher than 5.9%, which was much lower than the decay rate of the proton membranes provided in Comparative Examples 1-3, proving that the composite proton membranes provided by this invention have excellent stability.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite proton exchange membrane, characterized in that, It includes a carbon layer, a palladium layer disposed on at least one side of the carbon layer, and an active material layer disposed on a portion of the surface of the palladium layer away from the carbon layer; the active material layer includes a Group VIII element.

2. The composite proton exchange membrane according to claim 1, characterized in that, The thickness of the palladium layer is 5-10 micrometers.

3. The composite proton exchange membrane according to claim 1 or 2, characterized in that, The active material layer accounts for 0.1%-5.5% of the mass percentage of the composite proton exchange membrane.

4. The composite proton exchange membrane according to claim 1 or 2, characterized in that, The proton membrane is prepared by a method comprising the following steps: After activating carbon paper impregnated with palladium salt solution using a reducing agent solvent, the activated intermediate is subjected to palladium plating to obtain a palladium-plated intermediate; the palladium-plated intermediate is then impregnated with a solution including an active metal salt and an organic ligand, followed by calcination to obtain the composite proton exchange membrane.

5. A method for preparing a composite proton exchange membrane according to any one of claims 1-4, characterized in that, Includes the following steps: 1) After impregnating the carbon paper in a palladium salt solution, it is then activated in a reducing agent solution to obtain the activated product; 2) The activated product was placed in a palladium plating solution at 25-80℃ for palladium plating treatment, and then washed until the pH was 6-8 to obtain the palladium plating intermediate; 3) The palladium plating intermediate is impregnated using a solution mixture system including active metal salts and organic ligands, followed by calcination to obtain the composite proton exchange membrane.

6. The preparation method according to claim 5, characterized in that, Before the palladium plating process, step 1) is performed n times, where n ≥ 1.

7. The preparation method according to claim 5, characterized in that, The active metal salt includes at least one selected from nitrates, sulfates, chlorides, and acetates; and / or, The organic ligand comprises at least one of o-phenanthroline, 2,2-bipyridine, melamine, and phenylalanine; and / or, The molar ratio of the active metal salt to the organic ligand is 1:5 to 1:35; and / or, The molar concentration of the active metal salt in the solution mixture is 0.01-0.2 mol·L⁻¹. -1 ; and / or, The molar concentration of the organic ligand in the solution mixture does not exceed 4 mol·L⁻¹ -1 .

8. The preparation method according to claim 5, characterized in that, The protective atmosphere for the roasting includes an argon atmosphere and / or a nitrogen atmosphere. The calcination process involves a heating rate of 2–10 °C / min, a temperature of 300–800 °C, and a time of 1–5 hours.

9. An ammonia synthesis reactor, characterized in that, It includes an anode reaction chamber, a cathode electrolyte reaction chamber, and a cathode gas reaction chamber, wherein an exchange membrane is disposed between the cathode electrolyte reaction chamber and the anode reaction chamber; and a composite proton exchange membrane as described in any one of claims 1-4 or a composite proton exchange membrane prepared by the preparation method described in any one of claims 5-8 is disposed between the cathode electrolyte reaction chamber and the cathode gas reaction chamber.

10. A method for synthesizing ammonia, characterized in that, The ammonia synthesis reactor according to claim 9 is used; wherein nitrogen gas is introduced into the cathode gas reaction chamber as a nitrogen source, and electrolyte solution is introduced into the anode reaction chamber and the cathode electrolyte reaction chamber to conduct charge and provide protons.

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