Porous metal nickel powder, and preparation method and application thereof

Abstract

This invention belongs to the field of metal powder preparation technology, and discloses a porous nickel powder, its preparation method, and its applications. The method includes: preparing nickel oxalate powder as a precursor; forming a nickel coating layer on the surface of the nickel oxalate powder by chemical plating to obtain nickel oxalate@nickel core-shell structured composite particles; subjecting the composite particles to pyrolysis annealing treatment, causing the internal nickel oxalate to decompose and generate gas, and the external nickel coating layer to transform into a porous metal framework, thereby obtaining porous nickel powder. This method is simple, low-cost, and produces nickel powder particles with uniform size, stable pore structure, good connectivity, and large specific surface area, making it suitable as a precursor for electrocatalytic active materials or porous electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of metal powder preparation technology, specifically relating to a porous nickel powder, its preparation method, and its application. Background Technology

[0002] Nickel metal, due to its excellent electrical conductivity, corrosion resistance, and high chemical stability, is widely used in electrochemical catalysis, electrode materials, magnetic materials, and chemical protection. In recent years, with the development of electrocatalysis technology, nickel powders with porous or micro / nano-layered structures have become important precursor materials for the preparation of high-performance electrocatalysts due to their large specific surface area, abundant surface active sites, and good interfacial electron transport capabilities.

[0003] Currently, the main methods for preparing porous or micro / nano-structured nickel powders include chemical reduction, template methods, self-assembly methods, and microemulsion methods. Although these methods can obtain nickel powders with controllable morphology, they generally suffer from problems such as complex preparation processes, high costs, difficulties in template removal, low yields, and insufficient structural stability, making it difficult to achieve a good balance between micron-scale particles and porous structures. In addition, some methods produce nickel powders with wide particle size distributions, non-uniform pore structures, and limited specific surface areas, which are difficult to meet the requirements for structural controllability and reproducibility in electrocatalyst preparation.

[0004] Therefore, there is still a need for existing technologies to provide a porous micron-sized nickel powder with a simple preparation process, high yield, uniform particle size, and stable pore structure, so as to be more suitable for the construction and performance improvement of electrocatalysts. Summary of the Invention

[0005] The purpose of this invention is to provide a porous nickel powder, its preparation method, and its application, which solves the problems of complex preparation process, high cost, low yield, difficulty in simultaneously controlling particle size and pore structure, wide particle size distribution, non-uniform pore structure, and insufficient structural stability in the prior art.

[0006] This invention is achieved through the following technical solution: This invention discloses a method for preparing porous nickel powder, comprising the following steps: S1. Prepare nickel oxalate powder as a precursor; S2. A metallic nickel coating layer is formed on the surface of the nickel oxalate powder by chemical plating to obtain nickel oxalate@nickel core-shell structured composite particles. S3. The nickel oxalate@nickel core-shell composite particles are subjected to pyrolysis annealing treatment, which decomposes the nickel oxalate inside and generates gas, while the outer metallic nickel coating layer is transformed into a porous metal skeleton to obtain porous metallic nickel powder.

[0007] Furthermore, S1 specifically includes: Soluble nickel salt and ammonium oxalate were dissolved in water to prepare nickel salt solution and ammonium oxalate solution, respectively. Ammonium oxalate solution was added to nickel salt solution, and the pH was adjusted to 5.0-6.5 to carry out the precipitation reaction; After the reaction was complete, the precipitate was collected, washed, and dried to obtain nickel oxalate powder.

[0008] Furthermore, the concentration of nickel salt in the nickel salt solution is 0.1~0.5 mol / L, and the concentration of ammonium oxalate in the ammonium oxalate solution is 0.1~0.5 mol / L; the precipitation reaction temperature is 30~60℃, and the time is 10~60 min.

[0009] Furthermore, S2 specifically includes: A chemical plating mixture system was prepared by adding soluble nickel salt, complexing agent, surfactant and nickel oxalate powder obtained from S1 into water; Prepare reducing agent solution; Under heating and stirring conditions, the reducing agent solution is added to the chemical plating mixture, the pH is adjusted to 4-6, and a chemical reduction nickel plating reaction is carried out. After the reaction was completed, the system was cooled to room temperature, and the resulting product was filtered, washed and dried to form a metallic nickel coating layer on the surface of the nickel oxalate powder, thus obtaining nickel oxalate@nickel core-shell structured composite particles.

[0010] Furthermore, in the chemical plating mixture system, the soluble nickel salt is one or more of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, and nickel acetylacetone, with a concentration of 0.2~1.5 mol / L; The complexing agent is one or more of sodium citrate, potassium sodium tartrate, sodium lactate, sodium acetate, ethylenediamine, and triethanolamine, with a concentration of 0.4~1.6 mol / L; The surfactant is one or more of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, polyethylene glycol, and glycine, and the surfactant accounts for 0.05% to 0.3% of the total mass of the chemical plating mixture. The reducing agent is one or more of sodium hypophosphite, sodium formate, sodium borohydride, and sodium hyposulfite, and the concentration of the reducing agent solution is 0.1~2.5 mol / L.

[0011] Furthermore, the conditions for the chemical reduction nickel plating reaction are: reaction temperature 80~95℃, stirring speed 300~600rpm, and reaction time 30~90min.

[0012] Furthermore, the drying process is carried out at a temperature of 60-80℃ for 10-12 hours.

[0013] Furthermore, in step S3, the pyrolysis annealing treatment is carried out at a temperature of 300~600℃ under a hydrogen / argon mixed atmosphere.

[0014] The present invention also discloses a porous nickel powder, which is prepared by the aforementioned preparation method.

[0015] The present invention also discloses the application of the porous nickel powder in the preparation of electrocatalysts or electrode materials.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing porous nickel powder. First, nickel oxalate powder is prepared as a precursor. Then, a nickel coating layer is formed on its surface through chemical plating to obtain nickel oxalate@nickel core-shell composite particles. Finally, pyrolysis annealing is performed. The nickel coating layer formed by chemical plating can be retained and transformed into a porous metal framework during subsequent pyrolysis. Simultaneously, the internal nickel oxalate decomposes to generate gas, forming pores. This effectively avoids the uncontrollable particle size problem caused by free nucleation of nickel ions in traditional chemical reduction methods, achieving pre-design and stable control of particle size and morphology. Furthermore, the pre-construction of the outer metal framework makes the pore structure of the final product more uniform, interconnected, and stable, overcoming the defects of high randomness and easy collapse of pore structure in direct pyrolysis methods. Therefore, this method can simultaneously obtain porous nickel powder with uniform particle size, well-developed pores, and stable structure at the micron scale, and is suitable for the preparation of electrocatalysts and electrode materials with high requirements for structural repeatability. Compared with nickel powder prepared by traditional direct reduction or mechanical pulverization methods, the porous nickel powder prepared by this invention, through a synergistic control strategy of "precursor construction-chemical nickel plating-annealing pore formation," exhibits uniform particle size, stable structure, and adjustable pore distribution. Furthermore, this method features mild reaction conditions, a simple process flow, widely available raw materials, and low cost, making it easy to scale up. It is suitable for preparing highly active and structurally stable nickel powders, providing a new technical route for the large-scale preparation of high-performance electrocatalytic electrode materials.

[0017] Furthermore, by slowly adding the reducing agent solution dropwise to the plating bath containing nickel oxalate particles and maintaining the system pH in a weakly acidic range of 4-6, it is possible to effectively promote the preferential heterogeneous nucleation and deposition of nickel ions on the nickel oxalate surface, rather than the spontaneous formation of new nickel particles in the solution. The addition of a complexing agent can control the concentration of free nickel ions, resulting in a moderate deposition rate and the formation of a dense and uniform nickel coating layer. The addition of a surfactant helps to uniformly disperse nickel oxalate particles in the system and prevents agglomeration. In the resulting core-shell structure, the metallic nickel layer tightly wraps the nickel oxalate core, ensuring the structural integrity of the shell during subsequent pyrolysis and providing continuous and robust support for the final porous framework.

[0018] Furthermore, the operating conditions for the chemical reduction nickel plating reaction are: reaction temperature 80–95℃, stirring speed 300–600 rpm, and reaction time 30–90 min. The higher reaction temperature provides sufficient activation energy for the reduction reaction, enabling reducing agents such as sodium hypophosphite to effectively reduce and deposit nickel ions. The moderate stirring speed ensures the suspension and dispersion of nickel oxalate particles in the reaction system while avoiding coating detachment due to excessive shear force. The 30–90 min reaction time is sufficient to form a continuous and complete metallic nickel coating, and the coating thickness can be controlled by adjusting the time. This synergistic optimization of conditions results in high deposition efficiency and good repeatability in the chemical plating process, allowing for control of production costs and cycle time while ensuring coating quality.

[0019] Furthermore, the pyrolysis annealing treatment is carried out at a temperature range of 300–600 °C under a hydrogen / argon mixed atmosphere. Within this temperature range, nickel oxalate can fully decompose to produce gases such as CO2 and CO. The gas release process creates a rich porous structure inside and on the surface of the particles. Simultaneously, the CO produced during decomposition acts as a reducing gas to aid in the retention of nickel. The hydrogen in the hydrogen / argon mixed atmosphere reduces any trace amounts of nickel oxide that may be present, ensuring that the final product is high-purity metallic nickel. Argon acts as a protective gas to prevent nickel from being oxidized by air. The temperature window of 300–600 °C provides a moderate decomposition reaction rate, ensuring complete decomposition of nickel oxalate without causing excessive sintering of the metallic nickel framework, pore collapse, or particle fusion due to excessively high temperatures. Therefore, this step effectively removes the nickel oxalate core from the core-shell structure, while the outer metallic nickel layer is transformed into a three-dimensional stable framework with a multi-level porous structure, ultimately yielding porous nickel powder with a large specific surface area, interconnected pore structure, and good mechanical stability.

[0020] This invention also discloses porous nickel powder prepared by the above method. Since the particle size is mainly determined by the pre-designed nickel oxalate precursor throughout the preparation process, avoiding small particles or excessively large agglomerates introduced by free nucleation, the overall particle size distribution of the product is concentrated and the morphology is uniform. The continuous and stable metal framework formed after pyrolysis of the chemical plating layer endows the powder with good mechanical strength and structural stability. The gas release path generated by the decomposition of nickel oxalate is guided by the outer framework, resulting in a uniform and interconnected pore distribution, and the effective specific surface area is significantly higher than that of solid nickel powder or irregular porous nickel powder prepared by traditional methods. These product characteristics make it particularly suitable for electrocatalytic and electrode applications requiring large active areas, rapid mass transport, and stable cycling performance.

[0021] This invention also discloses the application of the porous nickel powder in the preparation of electrocatalysts or electrode materials. Due to its high specific surface area, abundant surface active sites, and excellent interfacial electron transport capability, this porous nickel powder provides more active catalytic centers when used in the preparation of electrocatalysts, thereby improving catalytic efficiency. When used in electrode materials, the interconnected pore structure facilitates rapid diffusion of electrolyte ions and efficient electron conduction, reducing polarization resistance. Simultaneously, the micron-sized particles ensure processability and coating stability during electrode preparation, avoiding the problems of easy agglomeration and poor dispersion of nanoparticles. Therefore, this porous nickel powder, as a precursor material for electrocatalysts or electrode materials, can significantly improve the performance and reliability of related devices, meeting the stringent requirements of high-performance electrochemical devices for the controllability and repeatability of electrode material structures. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation process of porous nickel oxalate according to the present invention; Figure 2 The images show the microstructure of the porous nickel powder prepared according to the present invention; wherein, Figure a shows the microstructure of the porous nickel powder at 100 μm; Figure b shows the microstructure of the porous nickel powder at 10 μm; Figure c shows the microstructure of the porous nickel powder at 10 μm in another region; and Figure d shows the microstructure of the porous nickel powder at 1 μm. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0024] The detailed description of the embodiments of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the figures and embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0026] Example 1 like Figure 1 As shown, this invention discloses a method for preparing porous nickel powder, comprising the following steps: 1) Prepare salt solutions of 0.4 mol / L nickel sulfate hexahydrate and 0.4 mol / L ammonium oxalate, respectively, with a solution volume of 150 mL for each solution; 2) Transfer the above nickel salt solution to a constant temperature water bath magnetic stirring reaction device, set the water bath temperature to 40 ℃ and the stirring speed to 300 rpm. After the temperature stabilizes, slowly add the ammonium oxalate solution to the nickel sulfate solution at a constant rate. 3) Under continuous stirring, ammonia water was added dropwise to the mixed solution to adjust the pH of the system to 6, and the reaction was carried out under this condition for 30 min; 4) After the reaction is complete, the system is naturally cooled to room temperature, the precipitate is filtered, washed with deionized water, and then dried to obtain nickel oxalate powder. 5) Weigh 0.15 mol nickel sulfate hexahydrate, 0.225 mol sodium citrate and 0.14 g sodium dodecylbenzenesulfonate and dissolve them in 150 mL of deionized water to prepare a plating solution system; then add 10 g of the above nickel oxalate powder, disperse it fully and transfer the mixture to a constant temperature water bath magnetic stirring reaction device, set the water bath temperature to 85 ℃ and the stirring speed to 400 rpm to obtain a chemical plating mixture system; 6) Weigh 0.3 mol of sodium hypophosphite and dissolve it in 150 mL of deionized water to prepare a reducing agent solution; 7) Under constant temperature and stirring conditions, the above reducing agent solution is slowly added dropwise to the chemical plating mixture at a constant rate, and the pH of the solution is adjusted to 5 by adding ammonia water. The reaction is continued for 60 min under these conditions. 8) After the reaction is complete, the system is naturally cooled to room temperature, the product is filtered, washed with deionized water, and then dried to form a nickel coating layer on the surface of the nickel oxalate powder, thus obtaining nickel oxalate@nickel core-shell structured composite particles.

[0027] 9) The nickel oxalate@nickel core-shell composite particles were placed in a tube furnace and treated at 450°C for 2 hours under a hydrogen-argon mixed atmosphere, and then cooled to room temperature to obtain porous metallic nickel powder.

[0028] Figure 2 These are scanning electron microscope (SEM) images of the porous nickel powder prepared in Example 1 of this invention. Figure a is a low-magnification morphology image (scale bar 100 μm), showing that the obtained nickel powder particles have a relatively uniform size distribution and a consistent overall morphology, exhibiting a spherical aggregate structure. Figures b and c are medium-magnification morphology images (scale bar 10 μm), revealing abundant pore structures on the particle surface with good connectivity between the pores, forming a three-dimensional porous network. Figure d is a high-magnification morphology image (scale bar 1 μm), showing that the particles are composed of fine nickel nanoparticles stacked and connected together, exhibiting a loose porous structure internally, with some areas showing localized hollow features.

[0029] Example 2 In step 6 of Example 1, the 0.3 mol sodium hypophosphite was replaced with 0.027 mol sodium hypophosphite, while the remaining steps remained the same.

[0030] Porous nickel powder was prepared according to the above steps.

[0031] Example 3 In step 6 of Example 1, the 0.3 mol sodium hypophosphite was replaced with 0.063 mol sodium hypophosphite, while the remaining steps remained the same.

[0032] Porous nickel powder was prepared according to the above steps.

[0033] Example 4 (Different precursor preparation conditions: higher pH) Prepare salt solutions of 0.2 mol / L nickel sulfate hexahydrate and 0.2 mol / L ammonium oxalate, respectively, with a solution volume of 200 mL for each solution; The above nickel salt solution was transferred to a constant temperature water bath magnetic stirring reaction device. The water bath temperature was set to 50°C and the stirring speed was set to 400 rpm. After the temperature stabilized, the ammonium oxalate solution was slowly added dropwise to the nickel sulfate solution. Under continuous stirring, ammonia was added dropwise to the mixed solution to adjust the pH of the system to 6.5, and the reaction was carried out under these conditions for 45 min. After the reaction is complete, proceed with steps 4-9 of Example 1 to obtain porous nickel powder.

[0034] Steps 5-8 use the chemical plating formula of Example 1, and the pyrolysis temperature of step 9 is 500℃, with a holding time of 2 h.

[0035] Example 5 (Different electroless plating formulations: higher nickel salt concentration) The precursor preparation steps are the same as steps 1-4 in Example 1; Weigh out 0.30 mol nickel sulfate hexahydrate, 0.40 mol potassium sodium tartrate and 0.20 g polyvinylpyrrolidone and dissolve them in 200 mL deionized water to prepare a plating solution system; then add 10 g of the above nickel oxalate powder, disperse it fully and transfer it to a constant temperature water bath magnetic stirring reaction device, set the water bath temperature to 90℃ and the stirring speed to 500 rpm; Weigh 0.50 mol of sodium hypophosphite and dissolve it in 200 mL of deionized water to prepare a reducing agent solution; Under constant temperature and stirring conditions, the reducing agent solution was slowly added dropwise to the plating solution system, and the pH of the solution was adjusted to 5.5 by adding ammonia water. The reaction was continued for 75 min under these conditions. After the reaction was completed, the powder was washed, dried and pyrolyzed according to steps 8-9 of Example 1 to obtain porous nickel powder.

[0036] Example 6 (Different pyrolysis temperatures: 300℃) The precursor preparation and electroless plating steps are the same as steps 1-8 in Example 1; The nickel oxalate precursor treated with electroless nickel plating was placed in a tube furnace and treated at 300°C for 2 hours in a hydrogen-argon mixed atmosphere, and then cooled to room temperature to obtain porous metallic nickel powder.

[0037] Example 7 (Different pyrolysis temperatures: 600℃) The precursor preparation and electroless plating steps are the same as steps 1-8 in Example 1; The nickel oxalate precursor treated with electroless nickel plating was placed in a tube furnace and treated at 600°C for 2 hours under a hydrogen-argon mixed atmosphere, and then cooled to room temperature to obtain porous metallic nickel powder.

[0038] Example 8 (Different types of nickel salts: nickel chloride) Replace the 0.4 mol / L nickel sulfate hexahydrate in step 1 of Example 1 with 0.4 mol / L nickel chloride hexahydrate, and follow the same steps as in Example 1 to obtain porous nickel powder.

[0039] Example 9 (Different reducing agents: sodium borohydride) The precursor preparation steps are the same as steps 1-4 in Example 1; Replace the 0.3 mol sodium hypophosphite in step 6 of Example 1 with 0.15 mol sodium borohydride, and follow the same steps as in Example 1 to obtain porous metallic nickel powder. Note: Because sodium borohydride has strong reducing activity, the reducing agent solution must be freshly prepared under ice-water bath conditions, and the dropping rate should be appropriately slowed down during the dropping process.

[0040] Example 10 (Different surfactants: polyethylene glycol) The precursor preparation steps are the same as steps 1-4 in Example 1; Replace 0.14 g sodium dodecylbenzenesulfonate in step 5 of Example 1 with 0.20 g polyethylene glycol (molecular weight 4000), and follow the same steps as in Example 1 to obtain porous nickel powder.

[0041] This invention achieves a chemical plating process dominated by heterogeneous deposition induced by the nickel oxalate surface through synergistic control of nickel salt concentration, reducing agent concentration, and reaction kinetics. The resulting nickel deposition layer consists of a buildup of fine nickel particles. On this basis, annealing treatment causes the nickel oxalate precursor to decompose and release gas, while retaining and reconstructing the outer metallic nickel skeleton. This results in the introduction of a uniform and interconnected multi-level porous structure while maintaining the overall size stability of the particles.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing porous nickel powder, characterized in that, Includes the following steps: S1. Prepare nickel oxalate powder as a precursor; S2. A metallic nickel coating layer is formed on the surface of the nickel oxalate powder by chemical plating to obtain nickel oxalate@nickel core-shell structured composite particles. S3. The nickel oxalate@nickel core-shell composite particles are subjected to pyrolysis annealing treatment, which decomposes the nickel oxalate inside and generates gas, while the outer metallic nickel coating layer is transformed into a porous metal skeleton to obtain porous metallic nickel powder.

2. The method for preparing porous nickel powder according to claim 1, characterized in that, S1 specifically includes: Soluble nickel salt and ammonium oxalate were dissolved in water to prepare nickel salt solution and ammonium oxalate solution, respectively. Ammonium oxalate solution was added to nickel salt solution, and the pH was adjusted to 5.0-6.5 to carry out the precipitation reaction; After the reaction was complete, the precipitate was collected, washed, and dried to obtain nickel oxalate powder.

3. The method for preparing porous nickel powder according to claim 2, characterized in that, The concentration of nickel salt in the nickel salt solution is 0.1~0.5 mol / L, and the concentration of ammonium oxalate in the ammonium oxalate solution is 0.1~0.5 mol / L; the precipitation reaction temperature is 30~60℃, and the time is 10~60 min.

4. The method for preparing porous nickel powder according to claim 1, characterized in that, S2 specifically includes: A chemical plating mixture system was prepared by adding soluble nickel salt, complexing agent, surfactant and nickel oxalate powder obtained from S1 into water; Prepare reducing agent solution; Under heating and stirring conditions, the reducing agent solution is added to the chemical plating mixture, the pH is adjusted to 4-6, and a chemical reduction nickel plating reaction is carried out. After the reaction was completed, the system was cooled to room temperature, and the resulting product was filtered, washed and dried to form a metallic nickel coating layer on the surface of the nickel oxalate powder, thus obtaining nickel oxalate@nickel core-shell structured composite particles.

5. The method for preparing porous nickel powder according to claim 4, characterized in that, In the aforementioned chemical plating mixture system, the soluble nickel salt is one or more of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, and nickel acetylacetone, with a concentration of 0.2~1.5 mol / L; The complexing agent is one or more of sodium citrate, potassium sodium tartrate, sodium lactate, sodium acetate, ethylenediamine, and triethanolamine, with a concentration of 0.4~1.6 mol / L; The surfactant is one or more of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, polyethylene glycol, and glycine, and the surfactant accounts for 0.05% to 0.3% of the total mass of the chemical plating mixture. The reducing agent is one or more of sodium hypophosphite, sodium formate, sodium borohydride, and sodium hyposulfite, and the concentration of the reducing agent solution is 0.1~2.5 mol / L.

6. The method for preparing porous nickel powder according to claim 4, characterized in that, The conditions for the chemical reduction nickel plating reaction are: reaction temperature 80~95℃, stirring speed 300~600 rpm, and reaction time 30~90 min.

7. The method for preparing porous nickel powder according to claim 4, characterized in that, The drying process is carried out at a temperature of 60-80℃ for 10-12 hours.

8. The method for preparing porous nickel powder according to claim 1, characterized in that, In step S3, the pyrolysis annealing treatment is carried out at a temperature of 300~600℃ under a hydrogen / argon mixed atmosphere.

9. A porous nickel powder, characterized in that, It is prepared by any one of claims 1 to 8.

10. The application of the porous nickel powder according to claim 9 in the preparation of electrocatalysts or electrode materials.

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