A method for preparing a nickel hollow fiber membrane and applications thereof

Abstract

This application relates to the field of electrocatalytic carbon dioxide reduction and discloses a method for preparing a nickel hollow fiber membrane, comprising the following steps: S1, preparation of casting solution; S2, spinning and film formation: the casting solution is extruded into a tap water bath at a certain speed through spinning extrusion molding, while water is injected into the hollow fiber at a constant speed with gas, causing a phase change between the extruded fiber and water, and then the extruded fiber is soaked in tap water overnight; S3, sintering: oxygen or air is first introduced into a tube furnace for oxidation, and then reduction is carried out under a hydrogen atmosphere to obtain a complete metal hollow fiber membrane. By applying pure nickel hollow fiber to the field of electrocatalytic carbon dioxide reduction, compared with other gas diffusion electrodes, nickel hollow fiber, as a self-supporting gas diffusion electrode, does not require the use of binders such as Nafion solution, and compared with precious metals such as gold, silver, and copper, which are excellent for carbon dioxide reduction, nickel is inexpensive and suitable for large-scale use.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic carbon dioxide reduction, specifically to a method for preparing a nickel hollow fiber membrane and its application. Background Technology

[0002] The extensive use of fossil fuel combustion has led to a sharp increase in atmospheric carbon dioxide levels. Carbon dioxide, as a stable linear molecule, is difficult to reduce. However, electrocatalytic carbon dioxide reduction can be achieved for the following reasons: First, it can be carried out under normal environmental conditions, and the reaction steps are highly controllable. Second, the products of electrochemical reduction can be adjusted by changing the reaction parameters. Third, electrochemical carbon dioxide reduction systems can be used in practical applications. Fourth, the electricity driving the electrochemical carbon dioxide reduction system can be obtained from renewable energy sources such as solar or wind power (providing an energy storage solution for intermittent renewable energy). This is considered one of the most promising carbon dioxide emission reduction technologies.

[0003] Hollow fiber membranes emerged in the 1940s. Due to their porous structure and unique self-supporting properties, they have been widely used in gas separation, water treatment, catalysis, and the petrochemical industry. Since the first use of copper hollow fiber as a cathode for CO2 electrocatalytic reduction in the 2016 reference "Three-dimensional porous hollow fiber copper electrode for efficient and high-speed electrochemical carbon dioxide reduction," research on the electrocatalytic reduction of CO2 using metal hollow fiber electrodes has become increasingly widespread. However, most research on CO2 reduction catalysts focuses on precious metals such as copper, silver, and gold, which are difficult to use universally. Porous nickel hollow fiber not only has the characteristics of high porosity and excellent mechanical strength, but nickel also has good CO2 catalytic reduction properties. In addition, nickel is inexpensive, making it a good self-supporting gas diffusion electrode for CO2 reduction. However, ensuring both high porosity and good self-supporting mechanical properties during the sintering process remains an unsolved problem in the electrocatalytic reduction of CO2 using hollow fiber.

[0004] In addition, the electrocatalytic CO2 reduction process is also affected by the poor solubility of CO2 in the electrolyte, the hydrogen evolution reaction, and the chemical inertness of CO2 itself, resulting in a slow kinetic process. In order to suppress the hydrogen evolution reaction and alleviate the low solubility of CO2, people often use the preparation of gas diffusion electrodes to improve the efficiency of CO2 reduction. However, the traditional gas diffusion electrode manufacturing requires a variety of components and complex manufacturing procedures, and the binder used may age and loosen during long-term electrolysis. Therefore, it is necessary to adopt a simpler method to manufacture a more robust gas diffusion electrode. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing nickel hollow fiber membranes and their applications, which solves the problems that hollow fiber membranes cannot guarantee high porosity while also possessing good self-supporting mechanical properties, and that they cannot be easily manufactured and used on a large scale during the electrocatalytic reduction of CO2.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a nickel hollow fiber membrane, comprising the following steps:

[0007] S1. Preparation of casting solution: Dissolve 5.88g of polysulfone in 25ml of N-methylpyrrolidone and stir continuously at 300r / min until homogeneous. Then add 16.9g of nickel powder in three batches every 2 hours, stirring continuously during the process. When adding the nickel powder for the last time, add 1.41g of polyvinylpyrrolidone at the same time and continue stirring for 3 hours until a homogeneous casting solution is formed.

[0008] S2, Spinning and film formation: The casting solution is extruded from the outer diameter of the injection pump spinneret at a rate of 22 ml / min into a bucket containing a large amount of tap water. At the same time, tap water with a flow rate of 150 ml / min at 2 bar is introduced into the inner diameter of the spinneret to form a hollow structure. The extruded fibers are then soaked in tap water overnight.

[0009] S3. Sintering: The oxidation stage of the nickel hollow fiber is carried out in a tube furnace under an oxygen atmosphere of 60 ml / min, while the reduction stage is carried out in a tube furnace under a hydrogen-nitrogen atmosphere of 100 ml / min. After the oxidation and reduction stages, the nickel hollow fiber membrane is obtained.

[0010] Preferably, in step S3, the heating program for the nickel hollow fiber oxidation stage is as follows: at 25°C, the temperature is increased to 300°C at a rate of 1°C / min and held for 1 hour, then increased to 600°C at a rate of 1°C / min and held for 4 hours, and then decreased to room temperature at a rate of 1°C / min.

[0011] Preferably, in step S3, the heating program for the nickel hollow fiber reduction stage is as follows: at 25°C, the temperature is increased to 800°C at a rate of 5°C / min and held at that temperature for 6 hours, and then decreased to room temperature at a rate of 5°C / min.

[0012] Preferably, in step S3, the hydrogen concentration in the hydrogen-nitrogen mixture is 20%.

[0013] An application of a nickel hollow fiber membrane for evaluating the electrocatalytic reduction performance of carbon dioxide includes the following steps:

[0014] A1. In the designed H-type cell, a nickel hollow fiber membrane is used as the working electrode, an Ag / AgCl electrode is used as the reference electrode, and a platinum sheet electrode is used as the counter electrode for testing.

[0015] A2. The electrolyte is a 0.5M CO2-saturated KHCO3 solution. Before the test, CO2 is bubbled into the solution at a rate of 30 ml / min for 30 min to ensure saturation. During the test, CO2 is continuously bubbled in at a rate of 15 ml / min. The gaseous products are detected online using gas chromatography, and the liquid products are analyzed using nuclear magnetic resonance spectroscopy after electrolysis.

[0016] A3. First, compare the linear voltammetric scan curves of the nickel hollow fiber membrane in Ar-saturated CO2-saturated KHCO3 solution to preliminarily determine its carbon dioxide reduction performance. Then, perform internal and external CO2 passage to scan its linear voltammetric curves and constant potential electrolysis experiments to further determine its carbon dioxide reduction performance.

[0017] Preferably, in step A1, the process of preparing the working electrode using a nickel hollow fiber membrane is as follows: one end of the nickel hollow fiber membrane is coated with conductive silver paste and placed into a conductive copper tube, the connection and the other end are sealed with epoxy resin, and the working electrode is obtained after curing.

[0018] Preferably, in step A3, the linear voltammetric scan is performed at -0.2V to -1.2V (vs RHE), and the constant potential electrolysis experiment is performed at -0.6V to -1.2V (vs RHE).

[0019] This invention provides a method for preparing a nickel hollow fiber membrane and its application. It has the following beneficial effects:

[0020] 1. This invention is the first to apply pure nickel hollow fiber in the field of electrocatalytic reduction of carbon dioxide. Compared with other gas diffusion electrodes, nickel hollow fiber, as a self-supporting gas diffusion electrode, does not require the use of binders such as Nafion solution. Moreover, compared with precious metals such as gold, silver and copper, which are excellent for carbon dioxide reduction, nickel is inexpensive and suitable for large-scale use.

[0021] 2. This invention utilizes dry-wet spinning technology, which involves a three-step process: preparation of casting solution, spinning to form a film, and sintering, to complete the preparation of nickel hollow fiber membranes. The overall method is simple to operate, fast to form, and suitable for industrial production.

[0022] 3. This invention utilizes hollow fiber electrodes as excellent self-supporting gas diffusion electrodes, which not only allows CO2 to be introduced from inside the fiber to form a gas-liquid-solid three-phase interface for reaction, increasing the contact area between CO2 and the catalyst, but also effectively inhibits the hydrogen evolution reaction, thereby promoting the CO2 reduction process. Furthermore, nickel hollow fibers are easier to obtain than the precious metals currently used for carbon dioxide reduction, which helps to save economic costs. Attached Figure Description

[0023] Figure 1 This is a comparison chart of LSV curves obtained from Ni powder with an average particle size of 800 nm and 3-5 μm.

[0024] Figure 2 This is a comparison diagram of the LSV of internally and externally circulated CO2 gas according to the present invention;

[0025] Figure 3 A Faraday efficiency diagram of nickel hollow fiber catalytic reduction of carbon dioxide prepared with nickel powder of the optimal particle size (800 nm) of the present invention;

[0026] Figure 4 This is a diagram showing the current stability of the nickel hollow fiber of the present invention during a long-term 12-hour electrolysis process at -1.0V (vs RHE). Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example:

[0029] The present invention provides a method for preparing a nickel hollow fiber membrane, comprising the following steps:

[0030] S1. Preparation of casting solution: Dissolve 5.88g of polysulfone in 25ml of N-methylpyrrolidone and stir continuously at 300r / min until homogeneous. Then add 16.9g of nickel powder in three batches every 2 hours, stirring continuously during the process. When adding the nickel powder for the last time, add 1.41g of polyvinylpyrrolidone at the same time and continue stirring for 3 hours until a homogeneous casting solution is formed.

[0031] S2, Spinning and film formation: The casting solution is extruded from the outer diameter of the injection pump spinneret at a rate of 22 ml / min into a bucket containing a large amount of tap water. At the same time, tap water with a flow rate of 150 ml / min at 2 bar is introduced into the inner diameter of the spinneret to form a hollow structure. The extruded fibers are then soaked in tap water overnight.

[0032] S3. Sintering: The oxidation stage of the nickel hollow fiber is carried out in a tube furnace under an oxygen atmosphere of 60 ml / min, while the reduction stage is carried out in a tube furnace under a hydrogen-nitrogen atmosphere of 100 ml / min. After the oxidation and reduction stages, the nickel hollow fiber membrane is obtained.

[0033] Compared with existing technologies, this invention is the first to apply pure nickel hollow fiber in the field of electrocatalytic reduction of carbon dioxide. Compared with other gas diffusion electrodes, nickel hollow fiber, as a self-supporting gas diffusion electrode, does not require the use of binders such as Nafion solution. Moreover, compared with precious metals such as gold, silver and copper, which are excellent for carbon dioxide reduction, nickel is inexpensive and suitable for large-scale use.

[0034] The following details each step in the preparation method of a nickel hollow fiber membrane provided in the embodiments of the present invention.

[0035] S1. Preparation of casting solution: Dissolve 5.88g of polysulfone in 25ml of N-methylpyrrolidone and stir continuously at 300r / min until homogeneous. Then add 16.9g of nickel powder in three batches every 2 hours, stirring continuously during the process. When adding the nickel powder for the last time, add 1.41g of polyvinylpyrrolidone at the same time and continue stirring for 3 hours until a homogeneous casting solution is formed.

[0036] Specifically, in this step, the casting solution is prepared by uniformly mixing a certain amount of metal powder, long-chain polymer, organic solvent, and thickener.

[0037] S2, Spinning and film formation: The casting solution is extruded from the outer diameter of the injection pump spinneret at a rate of 22 ml / min into a bucket containing a large amount of tap water. At the same time, tap water with a flow rate of 150 ml / min at 2 bar is introduced into the inner diameter of the spinneret to form a hollow structure. The extruded fibers are then soaked in tap water overnight.

[0038] Specifically, in this step, the film is spun into a film: the film is formed mainly by spinning and extrusion molding. The casting solution is extruded into a tap water bath at a certain speed, while water is injected into the hollow fiber with gas at a constant speed, so that the extruded fiber and water undergo a phase change. Then the extruded fiber is soaked in tap water overnight.

[0039] S3. Sintering: The oxidation stage of the nickel hollow fiber is carried out in a tube furnace under an oxygen atmosphere of 60 ml / min, while the reduction stage is carried out in a tube furnace under a hydrogen-nitrogen atmosphere of 100 ml / min. After the oxidation and reduction stages, the nickel hollow fiber membrane is obtained.

[0040] Specifically, in this step, sintering: the sintering process generally involves first introducing oxygen or air into a tube furnace for oxidation, and then reducing it under a hydrogen atmosphere to obtain a complete metal hollow fiber membrane.

[0041] To analyze the application fields of the nickel hollow fiber membrane prepared in the embodiments of the present invention, the experimental procedure for judging its performance in electrocatalytic reduction of carbon dioxide is described in detail below.

[0042] Please see the appendix Figure 1 - Appendix Figure 4 An application of a nickel hollow fiber membrane for evaluating the electrocatalytic reduction performance of carbon dioxide includes the following steps:

[0043] A1. In the designed H-type cell, a nickel hollow fiber membrane is used as the working electrode, an Ag / AgCl electrode is used as the reference electrode, and a platinum sheet electrode is used as the counter electrode for testing.

[0044] Specifically, the process for preparing the working electrode using a nickel hollow fiber membrane is as follows: one end of the nickel hollow fiber membrane is coated with conductive silver paste and inserted into a conductive copper tube. The connection and the other end are sealed with epoxy resin. After curing, the working electrode is obtained.

[0045] A2. The electrolyte is a 0.5M CO2-saturated KHCO3 solution. Before the test, CO2 is bubbled into the solution at a rate of 30 ml / min for 30 min to ensure saturation. During the test, CO2 is continuously bubbled in at a rate of 15 ml / min. The gaseous products are detected online using gas chromatography, and the liquid products are analyzed using nuclear magnetic resonance spectroscopy after electrolysis.

[0046] A3. First, compare the linear voltammetric scan curves of the nickel hollow fiber membrane in Ar-saturated CO2-saturated KHCO3 solution to preliminarily determine its carbon dioxide reduction performance. Then, perform internal and external CO2 passage to scan its linear voltammetric curves and constant potential electrolysis experiments to further determine its carbon dioxide reduction performance.

[0047] Specifically, the carbon dioxide reduction performance was initially determined using linear voltammetric scanning curves: the current density of nickel hollow fibers prepared from 800 nm nickel powder and 3-5 μm nickel powder showed significant differences between the current density under CO2 saturated atmosphere and under Ar atmosphere. Figure 1 );

[0048] Furthermore, subsequent experiments were conducted using both internal and external CO2 flow to scan its linear voltammetry curves and potentiostatic electrolysis, followed by data comparison and analysis. Figure 2 );

[0049] Furthermore, linear voltammetric scans were performed at -0.2V to -1.2V (vs RHE), and potentiostatic electrolysis experiments were conducted at -0.6V to -1.2V (vs RHE). Methane, carbon monoxide, and hydrogen were observed as products in gas chromatography, while NMR showed no liquid phase products. It was found that at -1.0V (vs RHE), the methane Faradaic efficiency was as high as 57.78%. Figure 3 ), current density -54.27 mA cm -2Furthermore, the current density did not decrease during the 12-hour electrolysis process, indicating that the nickel hollow fiber membrane has good stability. Figure 4 ).

[0050] In summary, the main process of evaluating the electrocatalytic reduction performance of nickel hollow fiber membranes for carbon dioxide reduction is as follows: Testing was conducted using a three-electrode system in a customized H-type cell in a 0.5M KHCO3 solution saturated with Ar and CO2. The carbon dioxide reduction performance of the nickel hollow fiber membrane was initially determined by comparing the linear voltammetric scan curves (LSV curves) under argon and carbon dioxide saturated atmospheres. Subsequently, potentiostatic electrolysis experiments (It curves) were performed at different potentials, and the products were detected.

[0051] Simultaneously, this study first prepared nickel hollow fibers and then used them as electrodes for carbon dioxide reduction research. It was found that the nickel hollow fiber membrane prepared from nickel powder with a particle size of 0.8 μm exhibited a methane Faradaic efficiency as high as 57.78% at a potential of -1.0 V (vs RHE) and a current density of -54.27 mA cm⁻¹. -2 The overall electrocatalytic reduction efficiency of carbon dioxide is better.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a nickel hollow fiber membrane, characterized in that, Includes the following steps: S1. Preparation of casting solution: Dissolve 5.88g of polysulfone in 25ml of N-methylpyrrolidone and stir continuously at 300r / min until homogeneous. Then add 16.9g of nickel powder in three batches every 2 hours, stirring continuously during the process. When adding the nickel powder for the last time, add 1.41g of polyvinylpyrrolidone at the same time and continue stirring for 3 hours until a homogeneous casting solution is formed. S2, Spinning and film formation: The casting solution is extruded from the outer diameter of the injection pump spinneret at a rate of 22 ml / min into a bucket containing a large amount of tap water. At the same time, tap water with a flow rate of 150 ml / min at 2 bar is introduced into the inner diameter of the spinneret to form a hollow structure. The extruded fibers are then soaked in tap water overnight. S3, Sintering: The oxidation stage of the nickel hollow fiber is carried out in a tube furnace under an oxygen atmosphere of 60 ml / min, while the reduction stage is carried out in a tube furnace under a hydrogen-nitrogen atmosphere of 100 ml / min. After the oxidation and reduction stages, the nickel hollow fiber membrane is obtained. In step S3, the heating program for the nickel hollow fiber oxidation stage is as follows: at 25°C, the temperature is increased to 300°C at a rate of 1°C / min and held for 1 hour, then increased to 600°C at a rate of 1°C / min and held for 4 hours, and then decreased to room temperature at a rate of 1°C / min. In step S3, the heating program for the nickel hollow fiber reduction stage is as follows: at 25°C, the temperature is increased to 800°C at a rate of 5°C / min and held for 6 hours, then decreased to room temperature at a rate of 5°C / min.

2. The method for preparing a nickel hollow fiber membrane according to claim 1, characterized in that, In step S3, the hydrogen concentration in the hydrogen-nitrogen mixture is 20%.

3. The application of the nickel hollow fiber membrane prepared by the method for preparing a nickel hollow fiber membrane according to any one of claims 1-2, characterized in that, Its application in evaluating the performance of electrocatalytic reduction of carbon dioxide includes the following steps: A1. In the designed H-type cell, a nickel hollow fiber membrane is used as the working electrode, an Ag / AgCl electrode is used as the reference electrode, and a platinum sheet electrode is used as the counter electrode for testing. A2. The electrolyte is a 0.5M CO2-saturated KHCO3 solution. Before the test, CO2 is bubbled into the solution at a rate of 30 ml / min for 30 min to ensure saturation. During the test, CO2 is continuously bubbled in at a rate of 15 ml / min. The gaseous products are detected online using gas chromatography, and the liquid products are analyzed using nuclear magnetic resonance spectroscopy after electrolysis. A3. First, compare the linear voltammetric scan curves of the nickel hollow fiber membrane in Ar-saturated CO2-saturated KHCO3 solution to preliminarily determine its carbon dioxide reduction performance. Then, perform internal and external CO2 passage to scan its linear voltammetric curves and constant potential electrolysis experiments to further determine its carbon dioxide reduction performance.

4. The application of the nickel hollow fiber membrane according to claim 3, characterized in that, In step A1, the process of preparing the working electrode using a nickel hollow fiber membrane is as follows: one end of the nickel hollow fiber membrane is coated with conductive silver paste and placed into a conductive copper tube. The connection and the other end are sealed with epoxy resin. After curing, the working electrode is obtained.

5. The application of the nickel hollow fiber membrane according to claim 3, characterized in that, In step A3, the linear voltammetric scan is performed at -0.2V to -1.2V vs RHE, and the constant potential electrolysis experiment is performed at -0.6V to -1.2V vs RHE.

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