One-step electrochemical synthesis of ammonia electrode and preparation method and application thereof

Abstract

The application provides a one-step electrochemical synthesis ammonia electrode and a preparation method and application thereof, and the method comprises the following steps: performing pretreatment operation on a porous conductive substrate; forming a cathode catalyst layer and / or an anode catalyst layer on the surface and pores of the porous conductive substrate through electrochemical deposition; mixing polytetrafluoroethylene dispersion liquid, perfluorosulfonic acid resin solution, ultrapure water and ethanol to prepare a binder slurry, and spraying the binder slurry on the surface of the cathode catalyst layer, the anode catalyst layer and the barrier layer; then, stacking the barrier layer and the catalytic electrode layer and performing hot-pressing compounding to obtain an integrated one-step electrochemical synthesis ammonia electrode. Through the processes of electrodepositing the catalyst layer, compounding the binder interface and pressure-keeping hot-pressing, the application improves the bonding stability between the catalyst layer, the porous conductive substrate and the barrier layer in the electrochemical synthesis ammonia device, reduces the interface contact resistance, and improves the mass transfer performance, anti-peeling performance and operation stability of the electrode.

Description

Technical Field

[0001] This application belongs to the field of electrochemical ammonia synthesis technology, and relates to a one-step electrochemical ammonia synthesis electrode, its preparation method and application. Background Technology

[0002] Electrochemical ammonia synthesis technology, as a green technology for ammonia synthesis under mild conditions (room temperature and pressure), avoids the harsh conditions of the traditional Haber process with high temperature and high pressure. It boasts significant advantages such as low energy consumption, environmental friendliness, and simple equipment, and has broad application prospects in the fields of new energy and green chemistry. The electrode, as the core component of the electrochemical ammonia synthesis battery, directly determines the battery's synthesis efficiency, selectivity, and long-term operational stability.

[0003] Currently, the preparation of electrochemical ammonia synthesis electrodes mostly employs traditional processes such as coating and sputtering to load catalysts onto the surface of a conductive substrate to form the electrode structure. However, electrodes prepared by such methods have significant drawbacks: on the one hand, the catalyst layer on the electrode surface is prone to detachment and pulverization, leading to a continuous decline in electrode activity; on the other hand, existing porous electrodes have insufficient barrier properties, easily resulting in problems such as electrolyte leakage and gas cross-permeation, affecting the long-term stable operation of the battery.

[0004] Therefore, there is an urgent need to design a one-step electrochemical ammonia synthesis electrode and its preparation method to overcome the shortcomings of existing technologies and meet the needs of practical applications. Summary of the Invention

[0005] To address the problems of poor barrier effect, easy catalyst detachment, and insufficient battery operation stability of existing electrochemical ammonia synthesis electrodes, the purpose of this application is to provide a one-step electrochemical ammonia synthesis electrode, its preparation method, and its application. By establishing a barrier layer, the mass transfer and pressure stability of the electrode are enhanced.

[0006] To achieve this objective, the following technical solution is adopted in this application: In a first aspect, this application provides a method for preparing a one-step electrochemical ammonia synthesis electrode, the method comprising the following steps: (1) Perform a pretreatment operation on the porous conductive substrate to obtain a pretreated substrate; (2) Electrodeposition is performed on the pretreated substrate obtained in step (1) to form a catalyst layer and obtain a catalytic electrode; (3) Mix polytetrafluoroethylene dispersion, perfluorosulfonic acid resin solution, ultrapure water and ethanol, and then stir and ultrasonically disperse to obtain adhesive slurry; (4) Spray the binder slurry from step (3) onto the surface of the catalyst layer of the catalytic electrode obtained in step (2); (5) Spray the adhesive slurry of step (3) onto at least one surface of the barrier layer to obtain a pretreated barrier layer; (6) Place the pretreatment barrier layer from step (5) on the surface of the catalytic electrode obtained in step (4) and hot-press it to obtain a one-step electrochemical ammonia synthesis electrode.

[0007] As a feasible technical solution of this application, in step (1), the porous conductive substrate is made of any one of titanium felt, stainless steel mesh, carbon paper, nickel foam, titanium mesh, copper foam, silver foam or porous stainless steel.

[0008] As a feasible technical solution of this application, the pretreatment operation includes sequentially performing cleaning pretreatment, drying treatment and etching activation treatment on the porous conductive substrate.

[0009] As a feasible technical solution of this application, the cleaning pretreatment includes sequentially cleaning the porous conductive substrate with organic solvent, alcohol solvent, and deionized water.

[0010] As a feasible technical solution of this application, the etching activation treatment is carried out using an acidic solution or an alkaline solution.

[0011] As a feasible technical solution of this application, the etching activation treatment is carried out using an acidic solution.

[0012] As a feasible technical solution of this application, the acidic solution is a sulfuric acid solution.

[0013] As a feasible technical solution of this application, the concentration of the sulfuric acid solution is 0.1 mol / L to 1 mol / L.

[0014] As a feasible technical solution of this application, the etching activation treatment time is 30 min to 40 min.

[0015] As a feasible technical solution of this application, in step (2), the electrodeposition process includes cathodic electrodeposition process and anodic electrodeposition process.

[0016] As a feasible technical solution of this application, the cathode electrodeposition process is performed in the following manner: Using a copper plate as the counter electrode, electrochemical deposition is performed in a copper-containing electrodeposition solution, and a copper-based cathode catalyst is deposited on the surface and / or pores of a pretreated substrate to obtain a cathode catalytic electrode.

[0017] As a feasible technical solution of this application, the anodic electrodeposition process is performed in the following manner: An inert plate is used as the counter electrode, and electrochemical deposition is carried out in a mixed electrodeposition solution containing platinum and gold precursors. Platinum and gold are co-deposited on the surface and / or pores of the pretreated substrate to obtain an anodic catalytic electrode.

[0018] As a feasible technical solution in this application, the loading of the copper-based cathode catalyst is 0.3 mg / cm³. 2 ~2mg / cm 2 .

[0019] As a feasible technical solution of this application, the copper-based cathode catalyst is at least partially deposited in the internal pores of the pretreated substrate and forms a continuous dense bonding layer on the surface of the pretreated substrate.

[0020] As a feasible technical solution of this application, the molar ratio of platinum to gold in the mixed electrodeposition solution is (1~3):1.

[0021] As a feasible technical solution of this application, the catalyst layer of the anode catalytic electrode includes any one or a combination of at least two or more of the following: platinum / gold bimetallic particles, platinum / gold alloy particles, and composites of platinum particles and gold particles.

[0022] As a feasible technical solution of this application, in step (3), the solid content of the polytetrafluoroethylene dispersion is 20%~30%.

[0023] As a feasible technical solution of this application, the perfluorosulfonic acid resin solution is Nafion D520 solution.

[0024] As a feasible technical solution of this application, the mass ratio of the polytetrafluoroethylene dispersion, the perfluorosulfonic acid resin solution, the ultrapure water and the ethanol is 1:5:(5~20):(5~20).

[0025] As a feasible technical solution of this application, the stirring treatment time is 5 min to 6 min.

[0026] As a feasible technical solution of this application, the ultrasonic dispersion treatment time is 30 min to 40 min.

[0027] As a feasible technical solution of this application, in step (4), the binder slurry is sprayed onto the surface of the catalyst layer of the cathode catalytic electrode and / or the surface of the catalyst layer of the anode catalytic electrode by ultrasonic spraying.

[0028] As a feasible technical solution of this application, the spraying amount of the adhesive slurry is 0.1 mL / cm. 2 ~2mL / cm 2 .

[0029] As a feasible technical solution of this application, in step (5), the thickness of the barrier layer is 10μm~400μm.

[0030] As a feasible technical solution of this application, the amount of adhesive slurry sprayed onto the surface of the barrier layer is 2 mL / cm. 2 ~5mL / cm 2 .

[0031] As a feasible technical solution of this application, the barrier layer is any one of a polymer membrane, a porous polymer membrane, an ion exchange membrane, or a polymer composite membrane that has ion conduction capability and liquid barrier capability.

[0032] As a feasible technical solution of this application, in step (6), the temperature of the hot pressing treatment is 100℃~160℃.

[0033] As a feasible technical solution of this application, the pressure of the hot pressing treatment is 3MPa~10MPa.

[0034] As a feasible technical solution of this application, the hot pressing treatment time is 1 min to 20 min.

[0035] As a feasible technical solution of this application, the flatbed hot press needs to be preheated before the hot pressing process.

[0036] As a feasible technical solution of this application, the pretreatment barrier layer is disposed between the cathode catalytic electrode and the electrolyte and / or between the anode catalytic electrode and the electrolyte.

[0037] Secondly, this application provides a one-step electrochemical ammonia synthesis electrode, which is prepared using the preparation method described in the first aspect, and the one-step electrochemical ammonia synthesis electrode comprises: Porous conductive substrate; Catalyst distributed on the surface and / or within the pores of the porous conductive framework substrate; A binder distributed on the surface and / or internal pores of the catalyst; And a pretreated barrier layer hot-pressed onto the surface of the catalyst; The porous conductive substrate, the catalyst, the binder, and the pretreated barrier layer form an integrated composite structure.

[0038] Thirdly, this application provides an application of the one-step electrochemical ammonia synthesis electrode described in the second aspect, wherein the one-step electrochemical ammonia synthesis electrode is used in the technical field of electrochemical ammonia synthesis.

[0039] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description.

[0040] Compared with the prior art, the beneficial effects of this application are as follows: This application improves the bonding stability between the catalyst layer and the porous conductive substrate and barrier layer in the electrochemical ammonia synthesis unit by electrodepositing the catalyst layer, treating the interface with a composite binder, and using a pressure-holding hot-pressing process. This reduces the interfacial contact resistance and improves the mass transfer performance, anti-peeling performance, and operational stability of the electrode. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A schematic diagram of a one-step electrochemical ammonia synthesis electrode preparation method provided for a specific embodiment of this application; Figure 2 An exploded structural diagram of a one-step electrochemical ammonia synthesis electrode assembly battery provided for a specific embodiment of this application; Figure 3 This is a schematic diagram of the anode composite electrode in Embodiment 1 of this application; Figure 4 This is a schematic diagram of the cathode composite electrode in Embodiment 1 of this application; Figure 5 This is a pressure balance curve of the electrode for the one-step electrochemical ammonia synthesis in Example 1 of this application; Figure 6 This is a graph showing the electrochemical performance of the one-step electrochemical ammonia synthesis electrode in Example 1 of this application. Figure 7 This is a schematic diagram of the anode electrode in Comparative Example 1 of this application; Figure 8 This is a schematic diagram of the cathode electrode structure in Comparative Example 1 of this application; Figure 9 The electrochemical performance test curve of the one-step electrochemical ammonia synthesis electrode in Comparative Example 1 of this application is shown. Figure 10 This is a pressure balance curve of the electrode in the one-step electrochemical ammonia synthesis method in Comparative Example 1 of this application; Figure 11 This is a schematic diagram of the anode electrode structure in Comparative Example 2 of this application; Figure 12 This is a schematic diagram of the cathode electrode structure in Comparative Example 2 of this application; Figure 13This is a pressure equilibrium curve of the electrode in the one-step electrochemical ammonia synthesis method in Comparative Example 2 of this application; Figure 14 This is a graph showing the electrochemical performance of the electrode used in the one-step electrochemical ammonia synthesis process in Comparative Example 2 of this application. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] It should be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0046] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0047] In one specific embodiment, this application provides a method for preparing a one-step electrochemical ammonia synthesis electrode, such as... Figure 1 As shown, the preparation method includes the following steps: (1) Perform a pretreatment operation on the porous conductive substrate to obtain a pretreated substrate; (2) Electrodeposition is performed on the pretreated substrate obtained in step (1) to form a catalyst layer and obtain a catalytic electrode; (3) Mix polytetrafluoroethylene dispersion, perfluorosulfonic acid resin solution, ultrapure water and ethanol, and then stir and ultrasonically disperse to obtain adhesive slurry; (4) Spray the binder slurry from step (3) onto the surface of the catalyst layer of the catalytic electrode obtained in step (2); (5) Spray the adhesive slurry of step (3) onto at least one surface of the barrier layer to obtain a pretreated barrier layer; (6) Place the pretreatment barrier layer from step (5) on the surface of the catalytic electrode obtained in step (4) and hot-press it to obtain a one-step electrochemical ammonia synthesis electrode.

[0048] It should be noted that the processing of steps (2) and (3) in this application is not in any particular order, and the processing of steps (4) and (5) is not in any particular order.

[0049] It should be noted that the preparation method in this application includes selecting a porous conductive framework as a conductive substrate, sequentially cleaning the conductive substrate with organic solvent, alcohol solvent, and deionized water, drying it after cleaning, and then etching and activating the conductive substrate with an acidic solution to remove oil, oxide layer, and impurities from the surface of the conductive substrate; forming a copper-based cathode catalyst layer and a platinum bimetallic anode catalyst layer on the surface and within the pores of the porous conductive substrate by electrochemical deposition, respectively; preparing a binder slurry by mixing polytetrafluoroethylene dispersion, perfluorosulfonic acid resin solution, ultrapure water, and ethanol, and spraying the binder slurry onto the surfaces of the cathode catalyst layer, anode catalyst layer, and barrier layer; subsequently, stacking the barrier layer with the catalytic electrode and hot-pressing composite to obtain an integrated composite electrode assembly. This application improves the bonding stability between the catalyst layer and the porous conductive substrate and barrier layer in the electrochemical ammonia synthesis device, reduces interfacial contact resistance, and improves the mass transfer performance, anti-peeling performance, and operational stability of the electrode through electrodeposition of the catalyst layer, composite binder interface treatment, and pressure-holding hot-pressing process.

[0050] It should be noted that at least one surface in this application may be, for example, one, two, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] In some embodiments, in step (1), the porous conductive substrate is made of any one of titanium felt, stainless steel mesh, carbon paper, nickel foam, titanium mesh, copper foam, silver foam, or porous stainless steel.

[0052] In some embodiments, the pretreatment process includes sequentially performing a cleaning pretreatment, a drying treatment, and an etching activation treatment on the porous conductive substrate.

[0053] In some embodiments, the cleaning pretreatment includes sequentially cleaning the porous conductive substrate with an organic solvent, an alcohol solvent, and a deionized water.

[0054] It should be noted that the organic solvent in this application can be acetone, and the alcohol solvent can be ethanol. No special limitations are made here, and those skilled in the art can choose the appropriate solvent based on the actual situation. Deionized water can be used before and after organic solvent cleaning. Cleaning with deionized water before organic solvent cleaning can remove dust and other impurities from the porous conductive substrate, while cleaning with deionized water after organic solvent cleaning can further remove residual organic solvent from the porous conductive substrate. The combined use of organic solvent and alcohol solvent can further remove oil, oxide layers, and impurities from the porous conductive substrate.

[0055] In some embodiments, the etching activation process is performed using an acidic or alkaline solution.

[0056] In some implementations, the etching activation process is performed using an acidic solution.

[0057] It should be noted that the acidic solution used in this application for etching activation treatment can further enhance the conductivity and surface activity of the porous conductive substrate, thereby constructing a dense bonding layer.

[0058] In some implementations, the acidic solution is a sulfuric acid solution.

[0059] In some embodiments, the concentration of the sulfuric acid solution is 0.1 mol / L to 1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] The concentration of the sulfuric acid solution in this application is 0.1 mol / L to 1 mol / L because within this range it is beneficial to remove the dense oxide layer of the porous conductive framework without excessively corroding the framework structure.

[0061] In some embodiments, the etching activation treatment time is 30 min to 40 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] The etching activation process in this application is 30 min to 40 min because this range is conducive to removing the dense oxide layer of the porous conductive framework without excessively corroding the framework structure.

[0063] In some embodiments, step (2) includes a cathode electrodeposition process and an anodic electrodeposition process.

[0064] In some embodiments, the cathode electrodeposition process is performed as follows: Using a copper plate as the counter electrode, electrochemical deposition is performed in a copper-containing electrodeposition solution, and a copper-based cathode catalyst is deposited on the surface and / or pores of a pretreated substrate to obtain a cathode catalytic electrode.

[0065] It should be noted that in this application, the pretreated porous conductive substrate is placed in an electrodeposition apparatus, with a copper plate as the counter electrode, and electrochemical deposition is performed in a copper-containing electrodeposition solution. This allows a copper-based cathode catalyst to be deposited on the surface and / or within the pores of the porous conductive substrate, forming a cathode catalyst layer that is tightly bonded to the porous conductive substrate. Exemplarily, the pretreated porous conductive substrate is placed on an electrodeposition platform, with a copper plate as the anode, and a current of 0.5–5 A is maintained for 5–30 minutes to deposit the cathode catalyst, forming a dense bonding layer that is tightly bonded to the self-supporting conductive substrate. The catalyst loading is 0.3–2 mg / cm³. 2 .

[0066] In some embodiments, the anodic electrodeposition process is performed as follows: An inert plate is used as the counter electrode, and electrochemical deposition is carried out in a mixed electrodeposition solution containing platinum and gold precursors. Platinum and gold are co-deposited on the surface and / or pores of the pretreated substrate to obtain an anodic catalytic electrode.

[0067] It should be noted that in this application, the treated porous conductive substrate is placed in an electrodeposition apparatus, with an inert plate as the counter electrode, and electrochemical deposition is performed in a mixed electrodeposition solution containing platinum and gold precursors, so that platinum and gold are co-deposited on the surface and / or within the pores of the porous conductive substrate to form an anode catalyst layer with a nano-rough structure; exemplary, the pretreated porous framework is placed on an electrodeposition platform, with an inert plate as the anode, and the mixed electrolyte ratio is Pt and Au with a molar ratio of 1:3. The anode catalyst is deposited at a current of 0.3~4A for 8~40min to construct a nano-rough active layer. Here, the anode catalyst layer has a rough surface composed of nanoscale protrusions, depressions and pores.

[0068] It should be noted that the inert plate in this application can be a graphite plate, platinum sheet, iridium-titanium plate, etc.; no special limitation is made here, and those skilled in the art can make adaptive adjustments according to the actual situation.

[0069] In some embodiments, the loading of the copper-based cathode catalyst is 0.3 mg / cm³. 2 ~2mg / cm 2 For example, it could be 0.3 mg / cm³2 0.5 mg / cm 2 1mg / cm 2 1.5 mg / cm 2 2mg / cm 2 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0070] In some embodiments, the copper-based cathode catalyst is at least partially deposited in the internal pores of the pretreated substrate and forms a continuous, dense bonded layer on the surface of the pretreated substrate.

[0071] In some embodiments, the molar ratio of platinum to gold in the mixed electrodeposition solution is (1~3):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] In this application, the molar ratio of platinum to gold in the mixed electrodeposition solution is (1~3):1 because this range is conducive to better HOR reaction on the anode side electrode.

[0073] In some embodiments, the catalyst layer of the anode catalytic electrode includes any one or a combination of at least two or more of platinum / gold bimetallic particles, platinum / gold alloy particles, and composites of platinum and gold particles.

[0074] It should be noted that the anode catalyst layer in this application includes at least one of platinum / gold bimetallic particles, platinum / gold alloy particles, and a composite of platinum and gold particles. Preferably, a bimetallic catalyst layer containing platinum and gold is selected, and the bimetallic catalyst layer has a nano-rough surface.

[0075] In some embodiments, in step (3), the solid content of the polytetrafluoroethylene dispersion is 20% to 30%, for example, it can be 20%, 22%, 24%, 26%, 28%, 30%, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] The solid content of the polytetrafluoroethylene dispersion in this application is 20% to 30% because this range is beneficial for isolating water in the gas.

[0077] In some embodiments, the perfluorosulfonic acid resin solution is a Nafion D520 solution.

[0078] In some embodiments, the mass ratio of polytetrafluoroethylene dispersion, perfluorosulfonic acid resin solution, ultrapure water and ethanol is 1:5:(5~20):(5~20), for example, it can be 1:5:5:10, 1:5:20:20, 1:5:15:20, 1:5:20:10, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] In this application, the mass ratio of polytetrafluoroethylene dispersion, perfluorosulfonic acid resin solution, ultrapure water and ethanol is 1:5:(5~20):(5~20) because this range is conducive to better dispersion of polymer ionomers.

[0080] It should be noted that, exemplarily, the preparation method of the adhesive slurry in this application can be as follows: 20% PTFE solution, DuPont Nafion D520 solution, ultrapure water, and ethanol are added sequentially in a mass ratio of 1:5:20:20. The mixture is then placed in a dispersion device and subjected to high-speed stirring for 5 minutes and ultrasonic dispersion for 30 minutes to prepare a uniform and stable adhesive slurry.

[0081] In some embodiments, the stirring time is 5 min to 6 min, for example, 5 min, 5.2 min, 5.4 min, 5.6 min, 5.8 min, 6 min, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0082] In some embodiments, the ultrasonic dispersion treatment time is 30 min to 40 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] In some embodiments, in step (4), the binder slurry is sprayed onto the surface of the catalyst layer of the cathode catalytic electrode and / or the surface of the catalyst layer of the anode catalytic electrode by ultrasonic spraying.

[0084] In some embodiments, the adhesive slurry is sprayed at a rate of 0.1 mL / cm². 2 ~2mL / cm 2 For example, it could be 0.1 mL / cm 2 0.5 mL / cm 2 1mL / cm 2 1.5 mL / cm 2 2mL / cm 2 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0085] The application rate of the adhesive slurry in this application is 0.1 mL / cm². 2 ~2mL / cm 2 This is because within this range, it is beneficial for better adhesion of the barrier layer while reducing ohmic resistance; if it is outside this range, excessive adhesive spraying will increase ohmic resistance, while insufficient spraying will not achieve the desired adhesion.

[0086] In some embodiments, in step (5), the thickness of the barrier layer is 10μm to 400μm, for example, it can be 10μm, 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0087] The thickness of the barrier layer in this application is 10μm to 400μm because this range is conducive to having good barrier properties while the concentration polarization remains almost unchanged. If it is not in this range, a barrier layer that is too thick will increase the mass transfer impedance and amplify the concentration polarization, while a barrier layer that is too thin will not play a barrier role.

[0088] In some embodiments, the amount of adhesive slurry sprayed onto the barrier layer surface is 2 mL / cm². 2 ~5mL / cm 2 For example, it could be 2 mL / cm 2 3mL / cm 2 4mL / cm 2 5mL / cm 2 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0089] In some embodiments, the barrier layer is any one of a polymer membrane, a porous polymer membrane, an ion exchange membrane, or a polymer composite membrane that has both ion conduction and liquid barrier capabilities.

[0090] It should be noted that, for example, the pretreatment of the barrier layer in this application can be to select a barrier layer with a thickness of 10~50μm, treat its surface with an adhesive slurry, and spray the slurry at a rate of 2~5mL / cm. 2 This ensures that the barrier layer and the catalyst layer have good compatibility and bonding strength.

[0091] In some embodiments, the temperature of hot pressing in step (6) is 100°C to 160°C, for example, it can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0092] In some embodiments, the pressure of hot pressing is 3MPa to 10MPa, for example, it can be 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0093] In some embodiments, the hot pressing time is 1 min to 20 min, for example, it can be 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0094] In this application, the hot pressing temperature is 100℃~160℃, the pressure is 3MPa~10MPa, and the time is 1min~20min. This is because within this range, it is beneficial to ensure the complete glassy transformation of the adhesive, so that the electrode and the barrier layer can be better bonded, while reducing deformation. At the same time, if the hot pressing time is too long, deformation will occur.

[0095] In some implementations, the flatbed hot press needs to be preheated before hot pressing.

[0096] It should be noted that in this application, the pretreated barrier layer is respectively covered on the surface of the catalyst layer of the prepared cathode / anode skeleton electrode, and hot-pressed using a flat plate hot press. The hot-pressing temperature is 100~160℃, the hot-pressing pressure is 3~10MPa, and the hot-pressing time is 1~20min. During the hot-pressing process, the temperature is first preheated to 80% of the target temperature. After the hot-pressing is completed, the pressure is maintained and the temperature is naturally cooled to below 60℃ before the pressure is released. After the hot-pressing is completed, a composite electrode structure is formed, and the cathode composite electrode and the anode composite electrode form a stacked structure that blocks the liquid electrolyte.

[0097] In some embodiments, a pretreatment barrier layer is disposed between the cathode catalytic electrode and the electrolyte and / or between the anode catalytic electrode and the electrolyte.

[0098] In one specific embodiment, this application provides a one-step electrochemical ammonia synthesis electrode, which is prepared using the above-described preparation method. The one-step electrochemical ammonia synthesis electrode includes: Porous conductive substrate; Catalysts distributed on the surface and / or within the pores of a porous conductive framework substrate; A binder distributed on the surface and / or internal pores of the catalyst; And a pretreated barrier layer hot-pressed onto the catalyst surface; The porous conductive substrate, catalyst, binder, and pretreatment barrier layer form an integrated composite structure.

[0099] It should be noted that the one-step electrochemical ammonia synthesis electrode in this application can be a cathode composite electrode, and the catalyst layer is a copper-based catalyst layer with a loading of 0.3~2 mg / cm³. 2 The composite electrode can be an anode composite electrode, and the catalyst layer is a platinum and gold bimetallic catalyst layer with a nano-rough surface. The thickness of the barrier layer is 10~400μm. The cathode composite electrode and the anode composite electrode form a stacked structure that blocks the liquid electrolyte. A schematic diagram of the exploded structure of the battery assembled with the composite electrodes in this application is shown below. Figure 2 As shown.

[0100] In one specific embodiment, this application provides an application of the above-described one-step electrochemical ammonia synthesis electrode, which is used in the technical field of electrochemical ammonia synthesis.

[0101] It should be noted that electrochemical ammonia synthesis, as a green alternative to the traditional Haber-Bosch process, can achieve the reaction of nitrogen with water or hydrogen-containing substances to produce ammonia under ambient temperature and pressure, avoiding the high energy consumption and large carbon dioxide emissions associated with high temperature and pressure processes. However, existing electrochemical ammonia synthesis technologies still face many bottlenecks. One of the core issues is the insufficient activity and selectivity of the cathode catalyst. The N≡N triple bond in nitrogen molecules is extremely stable (bond energy of 941 kJ / mol), making it difficult to activate and crack under mild conditions. On the other hand, the hydrogen evolution reaction (HER), as a competing reaction, severely reduces the Faradaic efficiency of ammonia, resulting in low energy utilization. The composite electrode provided in this application, through its unique active composite structure, effectively enhances nitrogen adsorption and activation capabilities while suppressing the occurrence of the HER side reaction, significantly improving the ammonia production rate and Faradaic efficiency of electrochemical ammonia synthesis. The composite electrode can be applied to various electrolytic cell configurations and exhibits excellent stability and durability in nitrogen-containing electrolytes or gas-solid-liquid three-phase interface systems, providing a feasible electrode solution for the industrial application of electrochemical ammonia synthesis.

[0102] Example 1 This embodiment provides a one-step electrochemical ammonia synthesis electrode preparation method, which includes the following steps: Pretreatment of porous conductive substrate: Carbon paper was selected as the porous conductive substrate and ultrasonically cleaned with acetone, ethanol and deionized water for 10 min each. After cleaning, it was dried at 80℃ for 60 min. Etching activation treatment was performed with sulfuric acid solution for 5 min to improve the surface activity of carbon paper.

[0103] Preparation of cathode catalytic electrode: Using a copper plate as the counter electrode, electrochemical deposition is performed in a copper-containing electrodeposition solution, and a copper-based cathode catalyst is deposited on the surface and / or pores of the pretreated substrate to obtain the cathode catalytic electrode.

[0104] Preparation of anodic catalytic electrode: Using an inert plate as the counter electrode, electrochemical deposition is carried out in a mixed electrodeposition solution containing platinum and gold precursors. Platinum and gold are co-deposited on the surface and / or pores of the pretreated substrate to obtain the anodic catalytic electrode. The molar ratio of Pt to Au in the mixed electrodeposition solution containing platinum and gold precursors is 1:0.5.

[0105] Barrier layer pretreatment: Select a barrier layer with a thickness of 20μm, a micropore diameter of 0.1μm, and a porosity of 85%. Spray adhesive slurry onto at least one surface of the barrier layer. Plasma modification treatment can be used, with a modification time of 5min, to achieve hydrophilic treatment of the barrier layer surface and improve its compatibility with the adhesive slurry.

[0106] Hot pressing composite: such as Figure 3 and Figure 4 As shown.

[0107] The pretreated barrier layer was applied to the catalyst layer surfaces of the cathode and anode catalytic electrodes, respectively, and then placed in a flat-plate hot press molding machine. The hot pressing parameters were set as follows: hot pressing temperature of 125℃, hot pressing pressure of 3MPa, and hot pressing time of 10min. During the hot pressing process, the temperature was first preheated to 100℃ (80% of the target temperature). After the hot pressing was completed, the pressure was maintained and the temperature was allowed to cool naturally to below 60℃ before the pressure was released to complete the hot pressing composite.

[0108] Post-processing: The one-step electrochemical ammonia synthesis electrode after hot pressing is cut to the required size, the edge burrs are removed by grinding, and its mass transfer efficiency, barrier performance and electrochemical activity are tested to screen out the finished electrodes that meet the requirements.

[0109] It should be noted that the specific methods for detecting mass transfer efficiency, barrier properties, electrochemical activity, and mechanical stability in this application include detecting mass transfer efficiency and electrochemical activity using an electrochemical workstation, and conducting pressure permeation tests on barrier properties using an electrochemical ammonia synthesis fixture.

[0110] In this embodiment, the barrier layer of the electrochemical ammonia synthesis electrode is tightly bonded to the cathode / anode without delamination; the catalyst layer does not detach, and the electrochemical performance is as described above. Figure 5 , Figure 6 As shown, the battery current-mass transfer efficiency is improved by more than 30%, and the electrolyte leakage rate is reduced by more than 80%. When applied to electrochemical ammonia synthesis batteries, the batteries can operate continuously and stably for more than 1200 hours, and the operational stability is significantly improved.

[0111] Comparative Example 1 This comparative example provides a one-step electrochemical ammonia synthesis electrode preparation method, which includes the following steps: Pretreatment of porous conductive substrate: Stainless steel mesh was selected as the conductive substrate and ultrasonically cleaned for 15 minutes each with acetone, deionized water and ethanol to remove surface oil, oxide layer and impurities. After cleaning, it was dried at 90℃ for 45 minutes to improve the conductivity and surface activity of stainless steel mesh.

[0112] The pretreated porous conductive substrate was placed in a copper / platinum plating solution for electrochemical deposition to complete the preparation. The resulting anode and cathode electrodes are shown below. Figure 7 and Figure 8 As shown.

[0113] Cathode electrode fabrication: A copper plate is used as the cathode, and the deposition process is accompanied by local hydrogen evolution. Bubbles are used as dynamic templates to form a dense bonding layer that is tightly bonded to the self-supporting conductive substrate, thus constructing a connected porous copper cathode electrode.

[0114] Anode electrode preparation: An inert plate is used as the anode, and the deposition process is accompanied by local hydrogen evolution. A porous transition layer is formed using bubbles as a dynamic template. A nano-rough active layer is constructed. In the mixed replacement solution, the molar ratio of Pt to Au is 1:0.5 to obtain the Pt-Au anode electrode.

[0115] The catalyst layer of the electrochemical ammonia synthesis electrode prepared in this comparative example did not detach, exhibited poor equilibrium stability, and showed large voltage fluctuations. Figure 9 As shown, the electrolyte leakage rate is high, such as Figure 10 As shown, when applied to an electrochemical ammonia synthesis battery, the battery can only operate for 300 hours.

[0116] Comparative Example 2 This comparative example provides a one-step electrochemical ammonia synthesis electrode preparation method, which includes the following steps: Pretreatment of porous conductive substrate: Stainless steel mesh was selected as the conductive substrate and ultrasonically cleaned for 15 min each with acetone, ethanol and deionized water to remove surface oil, oxide layer and impurities. After cleaning, it was dried at 90℃ for 45 min. Then, plasma activation treatment was performed for 10 min to improve the conductivity and surface activity of stainless steel mesh.

[0117] A stainless steel mesh conductive substrate is pretreated to construct a dense bonding layer; the pretreated self-supporting conductive substrate is then placed in a copper / platinum electroplating solution for electrochemical deposition, resulting in anodes and cathodes that are... Figure 11 and Figure 12 As shown.

[0118] Cathode electrode fabrication: Using a copper plate as the cathode, the deposition process is accompanied by local hydrogen evolution. Bubbles are used as dynamic templates to form a dense bonding layer that is tightly bonded to a self-supporting conductive substrate; thus, a connected porous copper cathode electrode is constructed.

[0119] Anode electrode preparation: An inert plate is used as the anode, and the deposition process is accompanied by local hydrogen evolution. A porous transition layer is formed using bubbles as a dynamic template. A nano-rough active layer is constructed. In the mixed replacement solution, the molar ratio of Pt to Au is 1:0.5, and a Pt-Au anode electrode is obtained.

[0120] Barrier layer pretreatment: Select a barrier layer with a thickness of 20μm, a micropore diameter of 0.1μm, and a porosity of 85%. Spray adhesive slurry onto at least one surface of the barrier layer. Plasma modification treatment can be used, with a modification time of 5min, to achieve hydrophilic treatment of the barrier layer surface and improve its compatibility with the adhesive slurry.

[0121] Post-processing: The prepared electrodes and barrier layers are assembled without hot pressing, cut to the required size, and the edge burrs are removed by grinding. Mass transfer efficiency, barrier performance and electrochemical activity are tested, and finished electrodes that meet the requirements are selected.

[0122] The electrochemical ammonia synthesis electrode prepared in this comparative example showed that the barrier layer adhered well to the electrode without delamination; the catalyst layer did not detach, and the electrochemical performance was as described above. Figure 13 , Figure 14 As shown, the electrolyte leakage rate is reduced by more than 80%. When applied to electrochemical ammonia synthesis batteries, the batteries can operate continuously and stably for more than 900 hours, and the operational stability is significantly improved.

[0123] By comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that Comparative Example 1, which only completes the substrate cleaning, electrodeposition of the catalyst layer and does not set the barrier layer, binder spraying and hot pressing process, has serious problems such as electrolyte leakage, drastic fluctuations in pressure and potential, and easy catalyst detachment. The battery can only operate stably for 300 hours. Comparative Example 2, which adds a modified barrier layer and binder spraying but omits the hot pressing composite step, can reduce the leakage rate by 80% and increase the operating time to 900 hours. However, insufficient interface bonding still causes slow deterioration of pressure and potential.

[0124] In summary, Example 1 of this application, which uses the complete process, demonstrates that the barrier layer and electrode are tightly bonded without delamination, the catalyst does not detach, the electrolyte leakage rate is reduced by more than 80%, the mass transfer efficiency is improved by 30%, the pressure and potential remain stable throughout the operation, and the battery can run continuously and stably for up to 1200 hours. This proves that the modified barrier layer combined with the binder is the basis for suppressing electrolyte leakage, the hot-pressing integrated composite process is the core key to reducing interfacial resistance and significantly improving the electrochemical stability and long-term service capability of the electrode, and the base acid activation can further enhance the bonding strength between the catalyst and the conductive framework. The complete preparation process can significantly improve the overall performance of the electrochemical ammonia synthesis electrode.

[0125] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a one-step electrochemical ammonia synthesis electrode, characterized in that, The preparation method includes the following steps: (1) Perform a pretreatment operation on the porous conductive substrate to obtain a pretreated substrate; (2) Electrodeposition is performed on the pretreated substrate obtained in step (1) to form a catalyst layer and obtain a catalytic electrode; (3) Mix polytetrafluoroethylene dispersion, perfluorosulfonic acid resin solution, ultrapure water and ethanol, and then stir and ultrasonically disperse to obtain adhesive slurry; (4) Spray the binder slurry from step (3) onto the surface of the catalyst layer of the catalytic electrode obtained in step (2); (5) Spray the adhesive slurry of step (3) onto at least one surface of the barrier layer to obtain a pretreated barrier layer; (6) Place the pretreatment barrier layer from step (5) on the surface of the catalytic electrode obtained in step (4) and hot-press it to obtain a one-step electrochemical ammonia synthesis electrode.

2. The preparation method according to claim 1, characterized in that, In step (1), the porous conductive substrate is made of any one of titanium felt, stainless steel mesh, carbon paper, nickel foam, titanium mesh, copper foam, silver foam, or porous stainless steel. The pretreatment operation includes sequentially performing cleaning pretreatment, drying treatment and etching activation treatment on the porous conductive substrate; The cleaning pretreatment includes sequentially cleaning the porous conductive substrate with organic solvent, alcohol solvent, and deionized water. The etching activation treatment is performed using an acidic or alkaline solution; The etching activation treatment is performed using an acidic solution; The acidic solution is a sulfuric acid solution; The concentration of the sulfuric acid solution is 0.1 mol / L to 1 mol / L; The etching activation treatment time is 30 min to 40 min.

3. The preparation method according to claim 1, characterized in that, In step (2), the electrodeposition process includes cathodic electrodeposition and anodic electrodeposition. The cathode electrodeposition process is performed in the following manner: Using a copper plate as the counter electrode, electrochemical deposition is performed in a copper-containing electrodeposition solution, and a copper-based cathode catalyst is deposited on the surface and / or pores of a pretreated substrate to obtain a cathode catalytic electrode. The anodic electrodeposition process is performed as follows: An inert plate is used as the counter electrode, and electrochemical deposition is carried out in a mixed electrodeposition solution containing platinum and gold precursors. Platinum and gold are co-deposited on the surface and / or pores of the pretreated substrate to obtain an anodic catalytic electrode.

4. The preparation method according to claim 3, characterized in that, The loading of the copper-based cathode catalyst is 0.3 mg / cm³. 2 ~2mg / cm 2 ; The copper-based cathode catalyst is at least partially deposited in the internal pores of the pretreated substrate and forms a continuous, dense bonding layer on the surface of the pretreated substrate; The molar ratio of platinum to gold in the mixed electrodeposition solution is (1~3):1; The catalyst layer of the anode catalytic electrode includes any one or a combination of at least two or more of the following: platinum / gold bimetallic particles, platinum / gold alloy particles, and composites of platinum and gold particles.

5. The preparation method according to claim 3, characterized in that, In step (3), the solid content of the polytetrafluoroethylene dispersion is 20%~30%; The perfluorosulfonic acid resin solution is a Nafion D520 solution; The mass ratio of the polytetrafluoroethylene dispersion, the perfluorosulfonic acid resin solution, the ultrapure water and the ethanol is 1:5:(5~20):(5~20); The stirring process takes 5 to 6 minutes. The ultrasonic dispersion treatment time is 30 min to 40 min.

6. The preparation method according to claim 3, characterized in that, In step (4), the binder slurry is sprayed onto the surface of the catalyst layer of the cathode catalytic electrode and / or the surface of the catalyst layer of the anode catalytic electrode by ultrasonic spraying. The application rate of the adhesive slurry is 0.1 mL / cm². 2 ~2mL / cm 2 .

7. The preparation method according to claim 1, characterized in that, In step (5), the thickness of the barrier layer is 10μm~400μm; The adhesive slurry is sprayed onto the surface of the barrier layer at a rate of 2 mL / cm². 2 ~5mL / cm 2 ; The barrier layer is any one of a polymer membrane, a porous polymer membrane, an ion exchange membrane, or a polymer composite membrane that has both ion conduction and liquid barrier capabilities.

8. The preparation method according to claim 3, characterized in that, In step (6), the temperature of the hot pressing treatment is 100℃~160℃; The pressure for the hot pressing process is 3MPa~10MPa; The hot pressing treatment time is 1 min to 20 min; Before the hot pressing process, the flatbed hot press needs to be preheated. The pretreatment barrier layer is disposed between the cathode catalytic electrode and the electrolyte and / or between the anode catalytic electrode and the electrolyte.

9. An electrode for one-step electrochemical synthesis of ammonia, characterized in that, The one-step electrochemical ammonia synthesis electrode is prepared by the preparation method according to any one of claims 1-8, and the one-step electrochemical ammonia synthesis electrode comprises: Porous conductive substrate; Catalyst distributed on the surface and / or within the pores of the porous conductive framework substrate; A binder distributed on the surface and / or internal pores of the catalyst; And a pretreated barrier layer hot-pressed onto the surface of the catalyst; The porous conductive substrate, the catalyst, the binder, and the pretreated barrier layer form an integrated composite structure.

10. An application of the one-step electrochemical ammonia synthesis electrode as described in claim 9, characterized in that, The one-step electrochemical ammonia synthesis electrode is used in the technical field of electrochemical ammonia synthesis.

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