Preparation method and application of amorphous carbon-coated nanometer nickel-based hydroxide catalyst

Abstract

The application discloses a preparation method and application of amorphous carbon-coated nanometer nickel-based hydrogen oxidation catalyst, and specifically comprises the following steps: step 1, preparing a precursor containing citrate by a coprecipitation method; step 2, centrifuging, washing and drying the precursor; step 3, reducing and nitriding the precursor by heat treatment; and step 4, grinding and dispersing.The nickel-based hydrogen oxidation catalyst precursor is synthesized by the simple and easy coprecipitation technology, the synthesis cost is low, the yield is high, and the mass production of the nickel-based catalyst can be met; since the citrate is used, the citrate is converted into an amorphous carbon layer during calcination and is coated on the surface of the catalyst, the amorphous carbon layer has a porous structure, the electrolyte is facilitated to contact the surface of the nickel, and the activity and stability of the nickel-based catalyst are enhanced, thereby providing guarantee for the application of the catalyst in hydrogen-nickel batteries or fuel cells.

Description

Technical Field

[0001] This invention relates to the field of non-precious metal hydroxide electrocatalyst preparation technology, and particularly to a method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst. This invention also relates to the application of this catalyst in alkaline fuel cells and nickel-hydrogen batteries. Background Technology

[0002] Over the past century, the excessive exploitation and use of fossil fuels has plunged the world into a severe energy crisis. As a major energy consumer, my country's demand for new renewable energy sources is particularly urgent. Therefore, researching and developing new renewable energy sources is a key strategy for replacing fossil fuels and solving the energy crisis. Hydrogen, due to its high energy density and environmentally friendly reaction products, is considered a new type of renewable commercial energy source. Meanwhile, the hydrogen oxidation reaction (HOR) is a crucial half-reaction in fuel cells / nickel-hydrogen batteries, providing significant energy and greatly determining the energy conversion efficiency. For the hydrogen oxidation reaction, noble metal catalysts such as platinum (Pt), ruthenium (Ru), and palladium (Pd) exhibit excellent catalytic activity, but their large-scale application is hampered by high prices and scarce resources. Therefore, developing high-performance, low-cost, and stable catalysts is imperative.

[0003] Transition metals, due to their abundant reserves and low prices, have become the most promising alternatives to precious metals in hydrogenation catalysts. Among transition metals, nickel, as one of the most common elements, is widely used in electrocatalysis and heterogeneous catalysis due to its low cost, high abundance, and high corrosion resistance in alkaline media. Ni et al. synthesized nickel hydroxide precursors via a hydrothermal method, and obtained Ni-based catalysts after heat treatment of the precursors, which were applied in alkaline hydroxide reactions (Angewandte Chemie International Edition, 2019, 58(22):7445-7449.); Su et al. mixed nickel levulinate with oleylamine and reacted it under high temperature conditions to obtain a precursor, and further heat-treated the precursor to synthesize a non-noble metal nickel-based electrocatalyst for alkaline hydroxide reaction (Advanced Functional Materials, 2021, 31(49): 2106156.); Ni et al. introduced a solvothermal synthesis of nickel-based hydroxide catalyst precursors, and obtained nickel-based catalysts by heat treatment under an ammonia atmosphere, which showed good activity and stability (Nature Materials, 2022, 21(7): 804-810.). Although the above methods can synthesize high-performance and highly stable nickel-based hydroxide catalysts, the entire reaction process is time-consuming, energy-intensive, has low metal utilization, and poor safety and reliability due to the limitations of the precursor synthesis methods. At the same time, the reaction process requires the use of a large amount of organic solvents, which poses a great threat to human health.

[0004] Based on the above, most current industry practices utilize hydrothermal and solvothermal methods to improve the activity and stability of nickel-based hydroxide catalysts. However, these methods do not comprehensively consider issues such as synthesis safety and cost, resulting in limited industrialization prospects. Chemical precipitation, due to its simple preparation process, easily controllable conditions, low operating costs, and short synthesis cycle, has become the preferred industrialization method. It can meet the needs of large-scale production of nickel-based catalysts while ensuring their activity and stability, and comprehensively guaranteeing production safety. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost, high-performance method for preparing amorphous carbon-coated nano-nickel-based hydroxide catalyst suitable for industrial application.

[0006] Another object of the present invention is to provide the application of the above-mentioned nickel-based hydroxide catalyst in alkaline fuel cells and nickel-hydrogen batteries. To achieve its purpose, the present invention adopts the following technical solution: A method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst includes the following steps: Step 1, Preparation of precursor: Dissolve nickel chloride and citric acid in water to obtain a transparent green solution, add an alkaline precipitant, adjust the pH of the solution to 7.5-12, react at a constant temperature for 0.5-10 h, centrifuge, wash, and dry to obtain precursor powder; Step 2, heat treatment to reduce precursor and nitriding: Place the precursor powder from step 1 in a tube furnace and react at 250-450℃ for 1-5 hours in a hydrogen / argon / ammonia atmosphere, then allow it to cool naturally. Step 3, Grinding and Dispersion: Grind the product obtained in Step 2 into a black powder to obtain a nickel-based catalyst.

[0007] As a further preferred embodiment of the technical solution of the present invention, in step 1, the molar ratio of citric acid to nickel salt is 1:0.1-1.

[0008] Furthermore, in step 1, the alkaline precipitant is selected from any one of ammonia, NaOH, and KOH.

[0009] Furthermore, in step 1, the mixture is centrifuged and washed until the supernatant is colorless or light green.

[0010] Furthermore, in step 2, the volume ratio of hydrogen, argon, and ammonia is 1:10-100:4-8.

[0011] The aforementioned amorphous carbon-coated nano-nickel-based hydroxide catalyst can be used in alkaline fuel cells or nickel-hydrogen batteries. Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention synthesizes a nickel-based hydroxide catalyst precursor through a simple and easy co-precipitation technique. The synthesis cost is low and the yield is high, which can meet the requirements for large-scale production of nickel-based catalysts and effectively solves the problems of harsh synthesis conditions and complex raw materials in existing methods. 2. This invention utilizes citrate ions to reduce the aggregation phenomenon during precursor synthesis through the strong interaction between nickel chloride and citric acid; 3. Because this invention uses citrate, during the calcination process, the citrate is converted into an amorphous carbon layer that coats the catalyst surface. The amorphous carbon layer has a porous structure, which facilitates the contact between the electrolyte and the nickel surface, enhances the activity and stability of the nickel-based catalyst, and provides a guarantee for the application of the catalyst in nickel-hydrogen batteries or fuel cells. 4. This invention solves the problem of catalyst agglomeration during thermal reduction and nitriding processes through grinding and dispersion operations.

[0012] In summary, this invention utilizes a co-precipitation method, in which nickel chloride and citric acid coordinate in solution to produce a nickel-based catalyst precursor over a wide pH range. The precursor is then thermally reduced and nitrided under a mixed atmosphere of hydrogen, argon, and ammonia to obtain the nickel-based catalyst. This process effectively avoids particle agglomeration and enhances the catalyst's activity and stability. Attached Figure Description

[0013] Figure 1 This is a SEM image of the amorphous carbon-coated nickel-based catalyst precursor used in Example 4 of this invention; Figure 2 This is a SEM image of the amorphous carbon-coated nickel-based catalyst used in Example 4 of this invention; Figure 3 This is an HR-TEM image of the amorphous carbon-coated nickel-based catalyst used in Example 4 of this invention; Figure 4 The LSV curves of the amorphous carbon-coated catalysts prepared in Examples 4-6 of this invention in 0.1 mol / L KOH solution are shown. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Examples 1-9 The values ​​of each parameter in Examples 1-9 are shown in Table 1.

[0015] Table 1. Parameter values ​​and performance of Examples 1-9 The preparation method of an amorphous carbon-coated nano-nickel-based hydroxide catalyst of the present invention will be described below using Example 4 as an example: Step 1: Dissolve 100 mg NiCl2·6H2O and 17.7 mg C6H7O8·H2O in 100 ml of deionized water to obtain a transparent green mixed solution. Add ammonia to adjust the pH of the solution to 8.0. React at a constant temperature for 10 h, then centrifuge, wash and dry.

[0016] Step 2: Place the dried powder into a tube furnace and heat-treat it at 450°C for 3 hours in a hydrogen / argon / ammonia atmosphere (1:10:4), then allow it to cool naturally.

[0017] Step 3: Grind the product obtained in Step 2 thoroughly into a black powder to obtain a nickel-based catalyst. The prepared nickel-based catalyst has a mass activity of up to 6.70 A / g.

[0018] Figure 1 This is a SEM image of the amorphous carbon-coated nickel-based catalyst precursor used in Example 4. Figure 2This is a SEM image of the amorphous carbon-coated nickel-based catalyst used in Example 4. (The image is obtained through...) Figure 1 , Figure 2 It can be observed that the nickel-based catalyst obtained after the precursor undergoes thermal reduction nitridation treatment exhibits a porous structure on its surface, which provides a larger specific surface area for hydrogen oxidation.

[0019] Figure 3 This is an HR-TEM image of the amorphous carbon-coated nickel-based catalyst used in Example 4. The projection image clearly shows that the gray-black nickel-based catalyst is uniformly coated with amorphous carbon, forming an overall "carbon (shell)-nickel (core)" structure. It is this structure that gives the amorphous carbon-coated nickel-based catalyst its good catalytic activity and stability.

[0020] Figure 4 The LSV curves of the amorphous carbon-coated catalysts prepared in Examples 4-6 of this invention are shown in 0.1 mol / L KOH solution. After correction, a voltage range of 0-50 mV was taken, and kinetic current conversion was performed according to the KL equation to obtain the mass activity of the nickel-based catalysts in Examples 4-6.

[0021] The above description is merely a preferred embodiment of the present invention, and while it is detailed and specific, it should not be construed as limiting the scope of the patent. Commonly known materials and properties used in the solution are not described in detail here. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the embodiments of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and substitutions will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst, characterized in that, Includes the following steps: Step 1, Preparation of precursor: Dissolve nickel chloride and citric acid in water to obtain a transparent green solution, add an alkaline precipitant, adjust the pH of the solution to 7.5-12, react at a constant temperature for 0.5-10 h, centrifuge, wash, and dry to obtain precursor powder; Step 2, heat treatment to reduce precursor and nitriding: Place the precursor powder from step 1 in a tube furnace and react at 250-450℃ for 1-5 hours in a hydrogen / argon / ammonia atmosphere, then allow it to cool naturally. Step 3, Grinding and Dispersion: Grind the product obtained in Step 2 into a black powder to obtain a nickel-based catalyst.

2. The method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst according to claim 1, characterized in that, In step 1, the molar ratio of citric acid to nickel salt is 1:0.1-1.

3. The method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst according to claim 2, characterized in that, In step 1, the alkaline precipitant is selected from any one of ammonia, NaOH, and KOH.

4. A method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst according to any one of claims 1-3, characterized in that, In step 1, centrifuge and wash until the supernatant is colorless or light green.

5. A method for preparing an amorphous carbon-coated nano-nickel-based hydroxide catalyst according to any one of claims 1-3, characterized in that, In step 2, the volume ratio of hydrogen, argon, and ammonia is 1:10-100:4-8.

6. The application of the amorphous carbon-coated nano-nickel-based hydroxide catalyst prepared by the method according to any one of claims 1-3 in alkaline fuel cells or nickel-hydrogen batteries.

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