A method for preparing a porous nickel electrode by molten salt etching

Abstract

The application first proposes a method for preparing a porous nickel electrode by molten salt etching, comprising the following steps: (a) burying a nickel electrode in etching salt, melting the etching salt, co-heating and keeping warm, and then naturally cooling to room temperature; (b) taking out the nickel electrode and cleaning it. The high-temperature molten salt is used for rapid etching of the electrode, a porous structure of several hundred nanometers to microns can be formed, and the high-energy surface can be exposed to a certain extent, so that the electrode has good activity in the catalytic electrolysis of water, and has obvious advantages in electrocatalytic hydrogen evolution and oxygen evolution, and can be applied to electrocatalytic hydrogen evolution reaction and oxygen evolution reaction; the method has the advantages of simple process, low cost, no pollution, and can be produced on a large scale, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electrode materials and relates to a method for preparing a porous nickel electrode, specifically a method for preparing a porous nickel electrode by etching an electrode substrate with molten salt. Background Technology

[0002] "Green hydrogen" is produced directly from renewable energy sources such as solar and wind power, with virtually no greenhouse gas emissions during the production process. Therefore, the production of "green hydrogen" can convert excess electricity generated from clean energy sources into hydrogen energy for storage, which is of great significance for curbing carbon emissions. Currently, hydrogen production methods mainly include fossil fuel cracking and reforming, water electrolysis, thermochemical water splitting, and photocatalytic hydrogen production. Among these, water electrolysis has advantages such as high conversion efficiency and scalability. Alkaline water electrolysis is currently one of the most important and easily scalable commercial methods, and the catalytic electrodes used in commercial alkaline water electrolysis are mainly nickel-based.

[0003] Porous nickel can greatly improve the electrocatalytic activity of electrodes and is suitable for electrolytic cells with high electrical density and low energy consumption. At present, the main processes for preparing porous nickel include template method, dealloying method, and electrodeposition method. These methods have some shortcomings: (1) The template method mainly uses organic or inorganic microspheres as templates, fills the template gaps with metallic nickel, and forms porous nickel after removing the template. Its porous structure is usually above tens of micrometers; (2) The dealloying method requires high temperature to form an alloy first, and then add acid or alkali to disalloy. This process is usually costly and easy to cause environmental pollution; (3) The electrodeposition method uses hydrogen bubbles to assist in the electrodeposition of porous nickel, which has problems such as uniformity and bonding strength. Therefore, it is urgent to develop a simple, low-cost, low-pollution, scalable and highly active porous nickel preparation method to help the development of alkaline water electrolysis for hydrogen production. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for preparing porous nickel electrodes by molten salt etching.

[0005] To achieve the above technical objectives, the present invention provides a method for preparing porous nickel electrodes by molten salt etching, comprising the following steps:

[0006] (a) The nickel electrode is buried in the etching salt, which melts the etching salt. After being heated and kept at a constant temperature, it is naturally cooled to room temperature.

[0007] (b) After removing the nickel electrode, clean it thoroughly.

[0008] Optimally, in step (a), the etching salt comprises a first inorganic salt and a second inorganic salt, wherein the first inorganic salt is an alkali metal chloride and the second inorganic salt is an inorganic iron salt, and the molar amount of iron ions in the inorganic iron salt is 0.5% to 10.0% of the molar amount of the first inorganic salt.

[0009] Further, in step (a), the molar amount of iron ions in the inorganic iron salt is 2.0% to 5.0% of the molar amount of the first inorganic salt.

[0010] Further, in step (a), the first inorganic salt is sodium chloride or potassium chloride, and the inorganic iron salt is ferric chloride or ferric sulfate.

[0011] Furthermore, in step (a), when the first inorganic salt is potassium chloride, the temperature of the co-heating insulation is 770℃~850℃; when the first inorganic salt is sodium chloride, the temperature of the co-heating insulation is 800℃~820℃.

[0012] Furthermore, in step (a), the co-heating and heat preservation time is 10 min to 2 h.

[0013] Ideally, in step (a), before burying the nickel electrode in the etching salt, the etching salt is ground and stirred evenly at room temperature.

[0014] Ideally, in step (a), the etching salt is heated to melt it, and the heating rate is 15-25°C / min.

[0015] Further, in step (a), the nickel electrode is a nickel-based self-supporting electrode, selected from woven nickel mesh, stretched nickel mesh or nickel foam.

[0016] Ideally, in step (b), the nickel electrode is removed, cleaned with water, and then dried.

[0017] This invention discloses a method for preparing porous nickel electrodes by molten salt etching. The method utilizes high-temperature molten salt to rapidly etch the electrode, forming porous structures ranging from hundreds of nanometers to micrometers. This process exposes high-energy surfaces to a certain extent, giving the electrodes good activity in catalytic water electrolysis reactions. It exhibits significant advantages in electrocatalytic hydrogen evolution and oxygen evolution reactions, and is applicable to both. The method is simple, low-cost, pollution-free, and suitable for large-scale production, showing broad application prospects. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the surface of a 46-mesh nickel wire mesh etched with potassium chloride molten salt obtained in Embodiment 1 of the present invention;

[0019] Figure 2This is a comparative example 1, a scanning electron microscope image of a nickel wire mesh surface obtained by chemical etching using the commonly used FeCl3 solution;

[0020] Figure 3 These are the hydrogen evolution polarization curves of Embodiment 1, Embodiment 2, Comparative Example 1, and nickel mesh in 30wt% KOH solution at 80°C according to the present invention.

[0021] Figure 4 These are the oxygen evolution polarization curves of Embodiment 1, Embodiment 2, Comparative Example 1, and nickel mesh in a 30wt% KOH solution at 80°C. Detailed Implementation

[0022] This invention discloses a method for preparing porous nickel electrodes using molten salt etching, comprising the following steps: (a) burying the nickel electrode in an etching salt, melting the etching salt, maintaining the temperature by heating, and then naturally cooling to room temperature; (b) removing the nickel electrode and cleaning it thoroughly. Rapid etching of the electrode using high-temperature molten salt can form porous structures on the order of hundreds of nanometers to micrometers, and can expose high-energy surfaces to a certain extent, giving it good activity in catalytic water electrolysis reactions. It has significant advantages for electrocatalytic hydrogen evolution and oxygen evolution reactions, and is applicable to both. This method is simple, low-cost, pollution-free, and can be mass-produced, showing broad application prospects.

[0023] In step (a), the etching salt preferably comprises a first inorganic salt and a second inorganic salt, wherein the first inorganic salt is an alkali metal chloride, and the second inorganic salt is an inorganic iron salt, and the molar amount of iron ions in the inorganic iron salt is 0.5% to 10.0% of the molar amount of the first inorganic salt, more preferably 2.0% to 5.0%. In step (a), the first inorganic salt is sodium chloride or potassium chloride, and the inorganic iron salt is ferric chloride or ferric sulfate; when the first inorganic salt is potassium chloride, the co-heating temperature is 770℃ to 850℃; when the first inorganic salt is sodium chloride, the co-heating temperature is 800℃ to 820℃. In step (a), the co-heating time is 10 min to 2 h. In step (a), before burying the nickel electrode in the etching salt, the etching salt is ground and stirred evenly at room temperature. In step (a), the temperature is increased to melt the etching salt at a rate of 15–25 °C / min. In step (a), the nickel electrode is a nickel-based self-supporting electrode, selected from woven nickel mesh, stretched nickel mesh, or nickel foam, which can be cleaned before use. In step (b), the nickel electrode is removed, rinsed with clean water, and then dried. All of the above methods can improve the etching effect of the nickel electrode.

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in this industry.

[0025] Example 1

[0026] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, including the following steps:

[0027] (a) Clean the 46-mesh nickel mesh (4cm×4cm, commercially available) with water and acetone by ultrasonic cleaning for 30 minutes each, then clean it in 3mol / L hydrochloric acid for 5 minutes. Remove the nickel mesh, clean it with water, and then dry it in an oven for later use.

[0028] Grind 100g of potassium chloride and 10g of ferric chloride in a ball mill for 2 hours, and then place the mixture in a corundum crucible.

[0029] The aforementioned dried nickel mesh was buried in a crucible, so that the nickel mesh was in a mixed salt of potassium chloride and ferric chloride; the crucible was placed in a muffle furnace, heated to 780°C (heating rate of 20°C / min), held at that temperature for 30 minutes, then removed and allowed to cool naturally to room temperature;

[0030] (b) After removing the nickel electrode, rinse it several times with clean water (usually 3 to 5 times, depending on actual needs) and then dry it in an oven to obtain a porous nickel electrode.

[0031] Example 2

[0032] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, using the nickel mesh from Example 1, and includes the following steps:

[0033] (a) Grind 100g of sodium chloride and 15g of ferric chloride in a ball mill for 2 hours and then place them in a corundum crucible.

[0034] The aforementioned dried nickel mesh is buried in a crucible, so that the nickel mesh is in a mixed salt of sodium chloride and ferric chloride; the crucible is placed in a muffle furnace and heated to 820°C (heating rate of 20°C / min; the temperature can also be set to 800°C or 810°C according to actual needs), held at that temperature for 30 minutes, then removed and allowed to cool naturally to room temperature;

[0035] (b) After removing the nickel electrode, wash it several times with clean water and then dry it in an oven to obtain a porous nickel electrode.

[0036] Example 3

[0037] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), 46g of potassium chloride and 10g of ferric chloride are put into a ball mill for grinding.

[0038] Example 4

[0039] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), 923.8g of potassium chloride and 10g of ferric chloride are put into a ball mill for grinding.

[0040] Example 5

[0041] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), 229.8g of potassium chloride and 10g of ferric chloride are put into a ball mill for grinding.

[0042] Example 6

[0043] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), 500g of potassium chloride and 10g of ferric chloride are put into a ball mill for grinding.

[0044] Example 7

[0045] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), the crucible is placed in a muffle furnace, heated to 770°C (heating rate of 20°C / min), held for 30 min, and then taken out and allowed to cool naturally to room temperature.

[0046] Example 8

[0047] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), the crucible is placed in a muffle furnace, heated to 850°C (heating rate of 20°C / min), held for 30 min, and then taken out and allowed to cool naturally to room temperature.

[0048] Example 9

[0049] This embodiment provides a method for preparing porous nickel electrodes by molten salt etching, which is basically the same as that in Embodiment 1, except that in step (a), 12.4 g of ferric sulfate is used.

[0050] Comparative Example 1

[0051] This example provides a method for preparing a porous nickel electrode, including the following steps:

[0052] (a) Clean the 46-mesh nickel mesh (4cm×4cm) with water and acetone by ultrasonic cleaning for 30 minutes each, then clean it in 3mol / L hydrochloric acid for 5 minutes. Place the obtained nickel mesh in an oven to dry for later use.

[0053] (b) Place the dried nickel mesh in a 1 mol / L FeCl3 solution and soak it at room temperature for 10 hours. After removing it, rinse it several times with water and then dry it in an oven.

[0054] Comparative Example 2

[0055] This example provides a method for preparing a porous nickel electrode, which is basically the same as that in Example 1, except that in step (a), 30g of potassium chloride and 10g of ferric chloride are ground in a ball mill.

[0056] Comparative Example 3

[0057] This example provides a method for preparing a porous nickel electrode, which is basically the same as that in Example 1, except that in step (a), 1000g of potassium chloride and 10g of ferric chloride are ground in a ball mill.

[0058] Comparative Example 4

[0059] This example provides a method for preparing a porous nickel electrode, which is basically the same as that in Example 1, except that ferric chloride is not added in step (a).

[0060]

[0061]

[0062] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing porous nickel electrodes by molten salt etching, characterized in that, Includes the following steps: (a) The nickel electrode is buried in the etching salt, which melts the etching salt. After being heated and kept at a constant temperature, it is naturally cooled to room temperature. (b) After removing the nickel electrode, clean it thoroughly. The etching salt comprises a first inorganic salt and a second inorganic salt, wherein the first inorganic salt is an alkali metal chloride and the second inorganic salt is an inorganic iron salt, and the molar amount of iron ions in the inorganic iron salt is 0.5% to 10.0% of the molar amount of the first inorganic salt; The nickel electrode is a nickel-based self-supporting electrode, selected from woven nickel mesh, stretched nickel mesh, or foamed nickel; the inorganic iron salt is ferric chloride or ferric sulfate. The first inorganic salt is sodium chloride or potassium chloride. When the first inorganic salt is potassium chloride, the temperature of the co-heating is 770℃~850℃; when the first inorganic salt is sodium chloride, the temperature of the co-heating is 800℃~820℃.

2. The method for preparing porous nickel electrodes by molten salt etching according to claim 1, characterized in that: In step (a), the molar amount of iron ions in the inorganic iron salt is 2.0% to 5.0% of the molar amount of the first inorganic salt.

3. The method for preparing porous nickel electrodes by molten salt etching according to claim 1, characterized in that: In step (a), the co-heating and heat preservation time is 10 min to 2 h.

4. The method for preparing porous nickel electrodes by molten salt etching according to claim 1, characterized in that: In step (a), before burying the nickel electrode in the etching salt, the etching salt is ground and stirred evenly at room temperature.

5. The method for preparing porous nickel electrodes by molten salt etching according to claim 1, characterized in that: In step (a), the temperature is increased to melt the etching salt, and the heating rate is 15~25℃ / min.

6. The method for preparing porous nickel electrodes by molten salt etching according to claim 1, characterized in that: In step (b), the nickel electrode is removed, cleaned with water, and then dried.

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