Preparation method and application of high-purity amorphous nickel hydrogen carbonate electrocatalyst

Abstract

The invention belongs to the technical field of electrocatalysis, and particularly relates to a preparation method and application of a high-purity amorphous nickel hydrogen carbonate electrocatalyst. In order to develop the amorphous Ni-based catalyst which has the characteristics of high purity, stable structure and easiness in large-scale preparation and can maintain efficient catalytic performance under high current density, the high-purity amorphous nickel hydrogen carbonate catalyst is prepared by utilizing a low-temperature coprecipitation method, and the catalyst is stable in structure, shows high activity and ultrahigh stability in an OER test, and is suitable for industrial production. The method is suitable for efficient oxygen evolution reaction under the conditions of high-concentration alkali liquor and large current density, and the process of large-scale practical application of the Ni-based catalyst is greatly promoted. Meanwhile, the method has the advantages of simple process, cheap and easily available raw materials, mild preparation conditions and no need of high-temperature calcination or special atmosphere treatment, and is suitable for industrial-grade large-scale preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and in particular relates to a preparation method and application of a high-purity amorphous nickel bicarbonate electrocatalyst. Background Art

[0002] Currently, in the electrocatalytic applications of new energy conversion technologies such as water electrolysis, carbon dioxide reduction, and nitrogen reduction, the oxygen evolution reaction (OER) is a key step that limits the overall reaction efficiency. Among them, NiFe-based catalysts (such as NiFe-LDH, NiFe oxide, etc.) are a relatively mature class of materials in OER research and are often used in alkaline water systems with low overpotential. However, in high-concentration alkaline environments (such as 6M KOH) or / and high current densities (>500mA·cm -2 ) conditions, its stability is significantly reduced. Meanwhile, although traditional Ni-based catalysts have attracted much attention due to their abundant resources and good stability, crystalline Ni-based materials often still have problems such as limited surface active sites and low conductivity, which leads to their poor performance at high current density (>500mA·cm -2 ) It is difficult to achieve efficient and stable catalytic performance.

[0003] In contrast, amorphous materials have a more disordered structure, which endows them with more surface active sites, better ion transport channels, and greater structural flexibility. Therefore, they are widely considered to be promising candidates for next-generation high-performance OER catalysts. However, the preparation process of existing amorphous Ni-based catalysts is generally plagued by problems such as impurity formation, structural instability, and insufficient purity. These bottlenecks seriously restrict their performance and hinder their large-scale practical application.

[0004] Therefore, the development of amorphous Ni-based catalysts that have high purity, stable structure, easy large-scale preparation, and can maintain efficient catalytic performance at high current density is of key significance and has broad application prospects for promoting technological innovation and industrial development in related fields. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings of the prior art, the present invention provides a method for preparing an amorphous nickel bicarbonate catalyst with a stable structure, mild preparation conditions, and readily available raw materials. The method is simple in process, does not require high-temperature calcination or special atmosphere treatment, and is suitable for industrial-grade large-scale preparation. The prepared catalyst is suitable for high-concentration alkali solution (6M KOH) and high current density (1A·cm -2 ) conditions for efficient oxygen evolution reaction.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst, the method comprising the following steps:

[0008] S1. Dissolve nickel salt in an organic solvent to prepare solution A, and refrigerate at 2-8°C for more than 1 day;

[0009] S2. Dissolve the potassium salt in water to make solution B, and refrigerate at 2-8°C for at least 1 day;

[0010] S3, placing solution A and solution B in an ice-water mixture and stirring, and under vigorous stirring, adding solution B to solution A, and continuing to stir and mix;

[0011] S4. The mixed solution is centrifuged at low temperature and the precipitate is collected. The precipitate is dried and ground to obtain high-purity amorphous nickel bicarbonate powder.

[0012] Preferably, the nickel salt includes one or more of nickel nitrate, nickel sulfate, nickel chloride, and nickel carbonate, and the potassium salt includes one or more of potassium bicarbonate, potassium chloride, potassium sulfate, potassium sulfate, and potassium phosphate.

[0013] More preferably, the nickel salt is nickel nitrate with a purity of 98%, and the potassium salt is potassium bicarbonate with a purity of 99.99%.

[0014] Preferably, in solution A, the concentration of nickel salt is 0.1-10 mmol / 10-100 mL; in solution B, the solubility of potassium salt is 0.2-20 mmol / 5-25 mL.

[0015] Preferably, the volume ratio of solution A to solution B is 2-20:1-5.

[0016] Preferably, in steps S1-S4, the temperature is controlled not to exceed 10°C throughout the entire process.

[0017] The second aspect of the present invention provides a high-purity amorphous nickel bicarbonate electrocatalyst prepared by the preparation method described in the first aspect.

[0018] The third aspect of the present invention provides the use of the high-purity amorphous nickel bicarbonate electrocatalyst described in the second aspect in the oxygen evolution reaction (OER).

[0019] Preferably, the oxygen evolution reaction includes a high concentration of alkali solution (≧6M OH - ) and / or high current density (>500mA·cm -2 ) conditions.

[0020] Preferably, before use, the high-purity amorphous nickel bicarbonate powder according to claim 7 is dissolved in a solvent with a conductive agent and a binder, and then coated on a conductive substrate and dried to form an electrode sheet.

[0021] More preferably, the conductive agent includes carbon black, graphene, carbon nanotubes, and carbon fibers; the binder includes Nafion, polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polytetrafluoroethylene (PTFE); and the conductive substrate includes conductive carbon paper, carbon cloth, nickel foam, graphene film, titanium foil, stainless steel mesh, copper foam, and conductive glass.

[0022] Preferably, the mass ratio of the amorphous nickel bicarbonate powder to the conductive agent is 1-5:1-3.

[0023] Preferably, the solvent is isopropanol, or a mixed solution of water and ethanol (volume ratio 1:1).

[0024] Preferably, the binder is Nafion, and the usage ratio of Nafion to amorphous nickel bicarbonate powder is 30-50 μL: 2-5 mg.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention utilizes a low-temperature coprecipitation method to prepare a high-purity amorphous nickel bicarbonate catalyst. The catalyst has a stable structure and exhibits high activity and ultra-high stability in OER tests. It is suitable for efficient oxygen evolution reaction under conditions of high-concentration alkali solution and high current density, greatly advancing the large-scale practical application of Ni-based catalysts. At the same time, the method is simple in process, the raw materials are cheap and readily available, the preparation conditions are mild, and no high-temperature calcination or special atmosphere treatment is required, making it suitable for industrial-grade large-scale preparation. Specifically, the present invention has the following advantages:

[0027] (1) The raw materials are cheap and readily available, the energy consumption is low, the process is simple, and it is suitable for large-scale preparation;

[0028] (2) This method effectively avoids the problem of impurity generation caused by the hydrolysis process in the traditional co-precipitation method, thereby significantly improving the purity of the product and ensuring its quality and performance;

[0029] (3) The prepared catalyst has a highly amorphous structure and has more active sites;

[0030] (4) The prepared catalyst was tested in high concentration alkali solution (6 M KOH) and high current density (1 A·cm -2 ) conditions, exhibiting excellent OER activity and ultrahigh stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD patterns of nickel bicarbonate catalyst powders prepared in Example 1, Example 2, and Comparative Example 1 and Comparative Example 2;

[0032] Figure 2CV graphs of the electrode sheets prepared in Example 1, Example 2 and Comparative Example 1, Comparative Example 2 after OER testing;

[0033] Figure 3 CV graph of the electrode sheet prepared in Example 3 after OER test;

[0034] Figure 4 This is a graph showing the long-term stability of the electrode sheet prepared in Example 2 in 6M KOH electrolyte during OER. DETAILED DESCRIPTION

[0035] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0036] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0037] Example 1: Preparation of carbon paper loaded with 2°C low-temperature coprecipitated nickel bicarbonate catalyst

[0038] (1) Prepare Solution A: Dissolve 2 mmol of nickel nitrate hexahydrate in 50 mL of anhydrous ethanol in a glass bottle and refrigerate at 2°C for 1 day.

[0039] (2) Prepare solution B: Dissolve 4 mmol of potassium bicarbonate in 5 mL of water in a glass bottle and refrigerate at 2°C for 1 day.

[0040] (3) Using a low-temperature stirring platform, place solution A and solution B in an ice-water mixture and stir for 1 h;

[0041] (4) Under vigorous stirring, solution B was quickly added to solution A and stirred at 600 rpm for 5 minutes;

[0042] (5) Place the mixed solution in a centrifuge tube, centrifuge it in a low-temperature centrifuge (temperature 2°C, speed 8000 rpm, time 5 min) and collect the precipitate:

[0043] (6) Wash the precipitate 3-4 times with 2°C ultrapure water and anhydrous ethanol, and then centrifuge to remove the washing solution;

[0044] (7) Freeze-dry the precipitate at -80°C for 1-2 days;

[0045] (8) taking out the precipitate and grinding it into a flour-like state to obtain high-purity amorphous nickel bicarbonate powder;

[0046] (9) Ink preparation: 4 mg of amorphous nickel bicarbonate powder and 1 mg of conductive carbon black were mixed, and then 480 μL of ultrapure water, 480 μL of anhydrous ethanol, and 40 μL of Nafion were added, and ultrasonicated for 1 h.

[0047] (10) Preparation of electrode sheet: Use a pipette to take 100 μL of ink and evenly apply it on the conductive carbon paper (1×1 cm 2 ) and dried using an infrared lamp;

[0048] (11) OER performance test: The electrode sheet prepared in step (10) was used as the working electrode, Hg / HgO as the reference electrode, and a graphite rod as the counter electrode to construct a three-electrode system. CV tests were performed in 1 M KOH.

[0049] Example 2: Preparation of carbon paper loaded with 8°C low-temperature coprecipitated nickel bicarbonate catalyst

[0050] (1) Prepare Solution A: Dissolve 2 mmol of nickel nitrate hexahydrate in 50 mL of anhydrous ethanol in a glass bottle and refrigerate at 8°C for 1 day.

[0051] (2) Prepare solution B: Dissolve 4 mmol of potassium bicarbonate in 5 mL of water in a glass bottle and refrigerate at 8°C for 1 day.

[0052] (3) Using a low-temperature stirring platform, place solution A and solution B in an ice-water mixture and stir for 1 h;

[0053] (4) Under vigorous stirring, solution B was quickly added to solution A and stirred at 600 rpm for 5 minutes;

[0054] (5) The mixed solution was placed in a centrifuge tube and centrifuged in a low-temperature centrifuge (temperature 2°C, speed 8000 rpm, time 5 min) to collect the precipitate;

[0055] (6) Wash the precipitate 3-4 times with 2°C ultrapure water and anhydrous ethanol and centrifuge to remove the washing solution;

[0056] (7) Freeze-dry the precipitate at -80°C for 1-2 days;

[0057] (8) taking out the precipitate and grinding it into a flour-like state to obtain high-purity amorphous nickel bicarbonate powder;

[0058] (9) Ink preparation: 4 mg of amorphous nickel bicarbonate powder and 1 mg of conductive carbon black were mixed, and then 480 μL of ultrapure water, 480 μL of anhydrous ethanol, and 40 μL of Nafion were added, and ultrasonicated for 1 h.

[0059] (10) Preparation of electrode sheet: Use a pipette to take 100 μL of ink and evenly apply it on the conductive carbon paper (1×1 cm 2 ) and dried using an infrared lamp;

[0060] (11) OER performance test: The electrode sheet prepared in step (10) was used as the working electrode, Hg / HgO as the reference electrode, and a graphite rod as the counter electrode to construct a three-electrode system. CV tests were performed in 1 M KOH.

[0061] Example 3: Preparation of nickel foam loaded with high-purity amorphous nickel bicarbonate catalyst

[0062] (1) preparing high-purity amorphous nickel bicarbonate powder according to steps (1) to (8) of Example 1;

[0063] (2) Ink preparation: 2 mg of amorphous nickel bicarbonate powder and 2 mg of conductive carbon black were mixed, 970 μL of isopropyl alcohol and 30 μL of Nafion were added, and ultrasonication was performed for 1 h.

[0064] (3) Preparation of electrode sheet: Under infrared light, the ink was evenly dropped on the nickel foam (1×1 cm 2 ) until dry;

[0065] (4) OER performance test: The electrode sheet prepared in step (3) was used as the working electrode, Hg / HgO as the reference electrode, and the graphite rod as the counter electrode to construct a three-electrode system in 6M KOH. A high current (1 A cm -2 )test.

[0066] Comparative Example 1: Preparation of carbon paper loaded with room temperature coprecipitated nickel bicarbonate catalyst

[0067] (1) Prepare solution A: Dissolve 2 mmol of nickel nitrate hexahydrate in 50 mL of anhydrous ethanol in a glass bottle and store at room temperature for 1 day.

[0068] (2) Prepare solution B: Dissolve 4 mmol of potassium bicarbonate in 5 mL of water in a glass bottle and leave at room temperature for 1 day;

[0069] (3) Under vigorous stirring at room temperature, solution B was quickly added to solution A and stirred at 600 rpm for 5 minutes;

[0070] (4) Place the mixed solution in a centrifuge tube and centrifuge at room temperature (8000 rpm, 5 min) to collect the precipitate;

[0071] (5) Wash the precipitate 3-4 times with room temperature ultrapure water and anhydrous ethanol, and then centrifuge to remove the washing solution;

[0072] (6) Freeze-dry the precipitate at -80°C for 1-2 days;

[0073] (7) taking out the precipitate and grinding it into a flour-like state to obtain room temperature co-precipitated nickel bicarbonate powder;

[0074] (8) Ink preparation: 4 mg nickel bicarbonate powder and 1 mg conductive carbon black were mixed, and then 480 μL ultrapure water, 480 μL anhydrous ethanol, and 40 μL Nafion were added, and ultrasonicated for 1 h.

[0075] (9) Preparation of electrode sheet: Use a pipette to take 100 μL of ink and evenly apply it on the conductive carbon paper (1×1 cm 2 ) and dried using an infrared lamp;

[0076] (10) OER performance test: The electrode sheet prepared in step (9) was used as the working electrode, Hg / HgO as the reference electrode, and the graphite rod as the counter electrode to construct a three-electrode system and perform CV test in 1 M KOH.

[0077] Comparative Example 2: Preparation of carbon paper loaded with hydrothermal high-temperature co-precipitated nickel bicarbonate catalyst

[0078] (1) Prepare a mixed solution according to steps (1) to (4) of Example 1;

[0079] (2) The mixed solution was transferred to a 100 mL hydrothermal reactor and heated at 200 °C for 20 h;

[0080] (3) The mixed solution was placed in a centrifuge tube and centrifuged to collect the precipitate. The precipitate was then washed three times with ultrapure water and anhydrous ethanol, and the washing solution was removed by centrifugation.

[0081] (4) Dry the precipitate in a 60°C oven overnight;

[0082] (5) taking out the precipitate and grinding it into a flour-like state to obtain high-purity crystalline nickel bicarbonate powder;

[0083] (6) Prepare ink: Mix 4 mg of crystalline nickel bicarbonate powder and 1 mg of conductive carbon black, then add 480 μL of ultrapure water, 480 μL of anhydrous ethanol, and 40 μL of Nafion, and sonicate for 1 h;

[0084] (7) Preparation of electrode sheet: Use a pipette to take 100 μL of ink and evenly apply it on the conductive carbon paper (1×1 cm 2 ) and dried using an infrared lamp;

[0085] (8) OER performance test: The electrode sheet prepared in step (7) was used as the working electrode, Hg / HgO as the reference electrode, and the graphite rod as the counter electrode to construct a three-electrode system and perform CV test in 1 M KOH.

[0086] The catalysts prepared in the examples and comparative examples were characterized in the following manner:

[0087] Figure 1 The XRD patterns of the nickel bicarbonate catalyst powders prepared by Example 1, Example 2 and Control Example 1, Control Example 2. It can be seen that the nickel bicarbonate powder prepared by the traditional hydrothermal reaction is highly crystalline, and its diffraction peak corresponds to PDF card 00-015-0782. The nickel bicarbonate powder prepared by room temperature co-precipitation has a small amount of weak diffraction peaks and obvious bulges, indicating that it is a state of coexistence of amorphous and crystalline. In contrast, the powder prepared by the 8°C low-temperature co-precipitation method has only weak bulges, and the amorphous degree is further improved. The nickel bicarbonate powder prepared by 2°C low-temperature co-precipitation has almost no diffraction peaks and has a high degree of amorphousness.

[0088] Figure 2 The CV graphs of the electrode sheets prepared in Example 1, Example 2 and Comparative Example 1 and Comparative Example 2 were measured after the OER test. The amorphous catalyst prepared by low-temperature coprecipitation at 2°C showed very high activity, surpassing the catalysts prepared at several other temperatures. -2 At a current density of 1.5 GHz, the overpotential is only 282 mV, which is about 100 mV lower than that of the crystalline state.

[0089] Figure 3 The CV graph of the electrode sheet of Example 3 after the OER test is obtained. It can be seen that the amorphous nickel bicarbonate catalyst loaded on the nickel foam exhibits high reaction activity in a high concentration 6M KOH solution. -2 The overpotential is only 435mV at high current density.

[0090] Figure 4 This is a graph showing the long-term stability of the electrode sheet of Example 2 in 6M KOH electrolyte. It can be seen that in a high concentration strong alkaline environment and a large current density of 1A·cm -2 Under these conditions, the amorphous nickel bicarbonate catalyst still showed ultra-high stability, with no obvious performance degradation within 300 hours. Further linear fitting analysis showed that its performance degradation rate was only 67μV·h -1 .

[0091] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst, characterized in that: The following steps are involved: S1. Dissolve nickel salt in an organic solvent to prepare solution A, and refrigerate at 2-8°C for more than 1 day; S2. Dissolve the potassium salt in water to make solution B, and refrigerate at 2-8°C for at least 1 day; S3, placing solution A and solution B in an ice-water mixture and stirring, and under vigorous stirring, adding solution B to solution A, and continuing to stir and mix; S4. The mixed solution is centrifuged at low temperature and the precipitate is collected. The precipitate is dried and ground to obtain high-purity amorphous nickel bicarbonate powder.

2. The method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst according to claim 1, characterized in that: The nickel salt includes one or more of nickel nitrate, nickel sulfate, nickel chloride, and nickel carbonate; the potassium salt includes one or more of potassium bicarbonate, potassium chloride, potassium sulfate, potassium sulfate, and potassium phosphate.

3. The method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst according to claim 2, characterized in that: The nickel salt is nickel nitrate with a purity of 98%, and the potassium salt is potassium bicarbonate with a purity of 99.99%.

4. The method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst according to claim 1, characterized in that: In solution A, the concentration of nickel salt is 0.1-10 mmol / 10-100 mL; in solution B, the solubility of potassium salt is 0.2-20 mmol / 5-25 mL.

5. The method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst according to claim 1, characterized in that: The volume ratio of solution A to solution B is 2-20:1-5.

6. The method for preparing a high-purity amorphous nickel bicarbonate electrocatalyst according to claim 1, characterized in that: In steps S1-S4, the temperature is controlled to be no higher than 10°C throughout the entire process.

7. A high-purity amorphous nickel bicarbonate electrocatalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the high-purity amorphous nickel bicarbonate electrocatalyst according to claim 7 in oxygen evolution reaction.

9. The use according to claim 8, characterized in that The oxygen evolution reaction includes an oxygen evolution reaction under conditions of high concentration alkali solution and / or high current density.

10. The use according to claim 8, characterized in that Before use, the high-purity amorphous nickel bicarbonate powder according to claim 7 is dissolved in a solvent with a conductive agent and a binder, and then coated on a conductive substrate, and dried to form an electrode sheet.

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