Preparation method of high-dispersion micrometer platinum powder

Abstract

This invention relates to the field of precious metal powder material preparation technology, specifically to a method for preparing highly dispersed micron-sized platinum powder. The method uses chloroplatinic acid as a precursor and hydrazine hydrate as a reducing agent. Equal volumes of aqueous solutions of chloroplatinic acid and hydrazine hydrate are added dropwise at a uniform rate in two stages to a dispersion at 70°C–80°C, with an interval of 3–5 minutes between additions. Mechanical stirring is maintained throughout the process, and the mixture is cooled to room temperature after the reaction. The resulting platinum powder is washed with deionized water until the pH is neutral, then washed with anhydrous ethanol and dried at room temperature. This invention features a simple process flow. By simultaneously adding reactants and controlling the process in stages, it achieves effective separation between the explosive nucleation of platinum atoms and the directional growth of crystal nuclei. This allows for the efficient preparation of high-performance platinum powder, which possesses advantages such as high dispersibility, uniform particle size, high purity, and high yield, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of precious metal powder material preparation technology, specifically to a method for preparing highly dispersed micron-sized platinum powder. Background Technology

[0002] Platinum powder, with its high melting point, excellent catalytic activity, strong corrosion resistance, superior electrical and thermal conductivity, and outstanding high-temperature oxidation resistance, has become an indispensable key material in advanced manufacturing, widely used in electronics, energy conversion, automotive, water treatment, air purification, and healthcare industries. With the continuous upgrading of advanced manufacturing technologies and the increasing demands of the industry, the market is placing more stringent requirements on the performance of platinum powder. Not only does it need to possess high dispersibility and uniform particle size, but it also needs to meet the core requirements of consistency and stability in high-end applications to adapt to large-scale applications in critical scenarios such as high-performance electronic pastes and precision electrodes.

[0003] Traditional methods for preparing platinum powder mainly include physical and chemical methods, as detailed below:

[0004] 1. Physical method

[0005] Physical methods of preparation typically rely on precision equipment and require harsh process conditions such as high temperature and high pressure. They also present technical challenges such as high energy consumption and low production efficiency, making it difficult to achieve large-scale mass production and thus limiting their widespread application in industrial settings.

[0006] 2. Chemical method

[0007] Chemical methods, which allow for the control of platinum powder preparation at room temperature and pressure by adjusting parameters such as reactant concentration, temperature, and pH, offer core advantages such as low production costs, strong process controllability, and ease of industrialization, making them the mainstream choice in the industry. Among these methods, the chemical liquid-phase reduction method, with its simple equipment requirements and controllable costs, has further become the core technology route for the large-scale preparation of platinum powder in the current field.

[0008] However, traditional chemical liquid-phase reduction methods generally adopt a "one-way feeding" or "single-step feeding" mode, that is, platinum precursor is usually added to the reducing agent solution, or the reducing agent solution is added to the platinum precursor solution. The mixture reacts directly in the liquid environment, which leads to the nucleation and growth processes of platinum particles in the reaction system being intertwined and fiercely competitive, making it difficult to achieve precise control. The platinum powder prepared in the end generally has defects such as diverse morphology (mostly non-spherical), discrete particle size distribution, and poor dispersibility due to hard agglomeration.

[0009] Currently published patent literature has conducted research on highly dispersed platinum powder, but the preparation process is complex and the experimental conditions are harsh. For example, patent literature with publication number CN112692274A, entitled "A method for preparing highly dispersed ultrafine platinum powder and its application," in H... + In a strongly acidic environment with a concentration of 1 mol / L to 3 mol / L, platinum powder with an average particle size of 0.45 μm was prepared by directly adding an organic dispersant solution and a reducing agent, hydrazine hydrate, to a chloroplatinic acid solution and stirring the mixture at 80℃ to 90℃. However, in practical applications, those skilled in the art have found that this method cannot effectively control the nucleation and crystal growth rates, resulting in a lack of particle size adjustment capability. It is only suitable for a narrow range of applications with a single requirement for ultrafine platinum powder and cannot meet the differentiated particle size requirements of various high-end fields. Furthermore, the strongly acidic environment is corrosive to the equipment, increasing the selection cost and maintenance difficulty of the production equipment.

[0010] To address the aforementioned problems, those skilled in the art have proposed various improvement schemes. However, in long-term use, these improved schemes have been found to still have significant technical defects. For example, patent document CN116673486A, entitled "A Method for Preparing Highly Dispersible Platinum Powder," describes a method where a dispersant is dissolved in water as the reaction substrate. Platinum salt solution, reducing agent solution, and 5%–20% sodium hydroxide strong alkali solution are added dropwise to the substrate, and the reaction is carried out with stirring at 25°C–65°C. After the reaction, encapsulating agents such as lauric acid, palmitic acid, oleic acid, or fatty acids are added to improve dispersibility, resulting in highly dispersed platinum powder with a particle size of 0.22 μm–1.0 μm that does not require seed crystals. However, in actual industrial applications, those skilled in the art have found that this method involves extremely cumbersome process steps, and the added encapsulating agents easily introduce impurities. The resulting platinum powder is prone to fine powder agglomeration and coarse powder inclusion, making it difficult to meet the suitability of platinum powder for high-performance applications.

[0011] The aforementioned defects and problems have restricted the large-scale application of platinum powder, specifically manifested in the following ways:

[0012] On the one hand, platinum powder with poor dispersibility and flowability will result in poor uniformity and printability of high-performance electronic pastes. The only way to make up for the shortcomings of paste performance is to increase the amount of precious metal platinum, which greatly increases the production cost.

[0013] On the other hand, electrodes prepared from this type of platinum powder are prone to problems such as weak adhesion, poor film density, and uneven surface after sintering, which seriously affect the electrode's electrical conductivity, thermal conductivity, catalytic performance, and long-term stability.

[0014] In summary, how to precisely control the nucleation and growth process of platinum powder to achieve high dispersibility, uniform particle size, and batch stability, while also covering the needs of micron-sized platinum powder preparation to adapt to a wider range of industrial scenarios, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0015] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing highly dispersed micron-sized platinum powder. The method described in this invention features a simple process flow. By controlling the material reaction rate through simultaneous feeding, the first step generates a large number of crystal nuclei in the liquid phase. In the second step, the platinum atoms generated in the reaction directionally settle on the surface of the crystal nuclei, causing the platinum powder particles to grow uniformly. This achieves effective separation between the explosive nucleation of platinum atoms and the directional growth of crystal nuclei, enabling the efficient preparation of high-performance platinum powder. The particle size parameters of the platinum powder obtained by the method described in this invention are stable and controllable. In the prepared platinum powder, the cumulative particle size reaches 90% of the corresponding particle size (D). 90 The particle size corresponding to a cumulative particle size of less than 2.5 μm and reaching 50% is (D) 50 The particle size is 1.0μm to 1.4μm. The platinum powder has advantages such as high dispersibility, uniform particle size, high purity and high yield, which are suitable for the needs of industrial-scale production.

[0016] The objective of this invention is achieved through the following approach:

[0017] A method for preparing highly dispersed micron-sized platinum powder includes the following steps:

[0018] 1) Take equal volumes of aqueous solutions of chloroplatinic acid and hydrazine hydrate, and simultaneously add them dropwise to a dispersion at 70℃~80℃ while stirring. Maintain the temperature of the dispersion at 70℃~80℃ throughout the dropwise addition. The aqueous solutions of chloroplatinic acid and hydrazine hydrate are added in two steps. The first addition takes 1min~3min, followed by an interval of 3min~5min. After the second addition of the remaining solution, stir for another 5min~10min. Cool to room temperature to obtain platinum powder 1.

[0019] 2) The platinum powder 1 obtained in step 1) is repeatedly washed with deionized water until the pH of the washing solution is 7.0±0.5, and then centrifuged to obtain platinum powder 2; platinum powder 2 is washed with anhydrous ethanol and then centrifuged to obtain platinum powder 3.

[0020] 3) The platinum powder 3 obtained in step 2) is spread evenly on a petri dish and left at room temperature for 10h to 24h. After the ethanol has completely evaporated, highly dispersed micron platinum powder is obtained.

[0021] In step 1), the concentration of the chloroplatinic acid aqueous solution is 40 g / L to 200 g / L, and the concentration of the hydrazine hydrate aqueous solution is 20 g / L to 100 g / L.

[0022] In step 1), the dripping is done at a constant rate of 10 ml / min to 20 ml / min.

[0023] In step 1), the preparation process of the dispersion includes: mixing and stirring the dispersant at a mass ratio of 1 g / L to 10 g / L of deionized water to obtain the dispersion.

[0024] In step 1), the dispersant is any one of polyvinylpyrrolidone (PVP), polyethylene glycol, and methylcellulose.

[0025] In step 1), the stirring is mechanical stirring with a stirring speed of 50 r / min to 200 r / min.

[0026] Preferably, chloroplatinic acid is used as a precursor and hydrazine hydrate is used as a reducing agent.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. This invention employs a staged dropwise addition process to precisely control the growth of platinum particles. During the first dropwise addition, rapid nucleation occurs through a low concentration and small amount of material, generating a large number of uniform and stable dispersed crystal nuclei. The interval further consolidates the stability of the dispersed crystal nuclei, preventing early agglomeration. During the second dropwise addition, the platinum atoms generated by reduction do not form new crystal nuclei but only deposit and grow on the surface of existing nuclei. This allows for controllable increase in platinum particle size while slowing down the local reaction rate, preventing excessive aggregation and agglomeration of platinum particles. Subsequent stirring and cooling operations further precisely control the growth of platinum particles, ensuring that the final platinum powder has the advantages of high dispersibility and uniform particle size.

[0029] 2. This invention employs a staged washing-centrifugation process, resulting in platinum powder with high purity, high yield, and good dispersibility. This invention achieves a balance between impurity removal, yield assurance, and dispersibility maintenance through a two-step washing and centrifugation process. The first step involves washing with deionized water to a pH of 7.0±0.5, efficiently dissolving and removing soluble byproducts such as chloride ions and hydrazine derivatives (i.e., removing hydrochloric acid, a reaction product, and incompletely reacted reactants), significantly mitigating the adverse effects of residual impurities on platinum powder purity and catalytic activity. Simultaneously, centrifugation greatly reduces platinum powder loss during washing, ensuring a stable yield. The second step involves a secondary washing of the platinum powder with anhydrous ethanol, which dissolves residual water, removes trace adsorbed impurities, and avoids particle agglomeration caused by water forming liquid bridges between platinum particles during drying. Furthermore, ethanol's rapid evaporation rate and low surface tension maximize the preservation of the previously formed high dispersion and uniform particle size, resulting in platinum powder with high purity, high dispersibility, and high yield.

[0030] 3. This invention employs a room temperature drying design to improve the preparation efficiency and finished product stability of platinum powder. By spreading the washed and centrifuged platinum powder evenly, this invention increases the contact area between the platinum powder and air, accelerating the evaporation of anhydrous ethanol from the surface of the platinum powder, effectively shortening the drying time and improving the preparation efficiency. Simultaneously, allowing the platinum powder to stand at room temperature for 10-24 hours ensures sufficient evaporation of anhydrous ethanol, thereby preventing particle agglomeration, stabilizing the high dispersibility and particle size uniformity of the platinum powder, and ensuring stable final product quality.

[0031] 4. In this invention, the parameters work together to ensure a controllable reaction and consistent batch quality.

[0032] 4-1) In this invention, chloroplatinic acid aqueous solution and hydrazine hydrate aqueous solution are prepared in an equal volume ratio of 1:1 to ensure that chloroplatinic acid aqueous solution and hydrazine hydrate aqueous solution are added dropwise at the same time and react uniformly in a homogeneous liquid environment. Through precise control of the amount of materials, the overall reaction rate can be effectively regulated, and the risk of platinum particle agglomeration caused by local reactant concentration imbalance can be effectively avoided, thereby achieving precise control of the platinum atom generation rate.

[0033] 4-2) This invention uses a peristaltic pump as the dripping device, which can precisely control the amount of chloroplatinic acid aqueous solution and hydrazine hydrate aqueous solution and the dripping rate of 10ml / min to 20ml / min, effectively ensuring that the chloroplatinic acid aqueous solution and hydrazine hydrate aqueous solution are always added synchronously in equal volume ratio: this provides sufficient reaction time for the platinum ion reduction reaction, avoiding violent local reactions and platinum particle agglomeration caused by excessively fast dripping rate; it also prevents problems such as low reaction efficiency and excessively long production cycle caused by excessively slow dripping rate, further enhancing the controllability and stability of the entire reaction process, and effectively ensuring the consistency of product quality in different batches;

[0034] 4-3) The dispersion in this invention is prepared at a ratio of 1 g / L to 10 g / L of dispersant and deionized water, which can ensure that the dispersant (such as polyvinylpyrrolidone, polyethylene glycol or methylcellulose) is fully dissolved in deionized water to form a stable liquid phase dispersion environment. This allows the platinum crystal nuclei generated in the early stage of the reaction to be uniformly and stably dispersed in the dispersion, which is conducive to the uniform diffusion of platinum atoms in the later stage and their final deposition on the surface of the crystal nuclei. At the same time, the spatial steric hindrance effect of the dispersant molecular chain provides continuous and good dispersion support for the growth of platinum powder particles.

[0035] 4-4) The present invention uses mechanical stirring at 50r / min to 200r / min, which can provide continuous and stable shear force and mixing effect, promote the rapid diffusion and contact of platinum ions and reducing agent, and ensure that the generated platinum crystal nuclei are always uniformly suspended in the dispersion, ensuring that platinum atoms are subsequently deposited in an orderly manner on the surface of the crystal nuclei, further consolidating the high dispersibility and particle size uniformity of platinum powder.

[0036] The advantages of this invention are as follows:

[0037] This invention employs a chemical liquid-phase reduction method, combined with heating conditions and a two-step simultaneous feeding process, to precisely add the chloroplatinic acid precursor solution and the reducing agent hydrazine hydrate solution into a system containing a dispersant. This achieves effective separation of the platinum atom nucleation and growth stages, ultimately producing micron-sized platinum powder with uniform particle size distribution and excellent dispersibility.

[0038] The first feeding stage (platinum atom burst nucleation period): Equal volumes of chloroplatinic acid solution and hydrazine hydrate solution are simultaneously added dropwise to a dispersion at a constant temperature (70℃~80℃) at the same rate, achieving rapid mixing under continuous mechanical stirring. The high-temperature environment significantly increases the redox reaction rate of chloroplatinic acid and hydrazine hydrate, promoting the rapid generation of a large number of platinum atoms in the reaction system. When the platinum atom concentration increases and exceeds the critical supersaturation, multiple platinum atoms instantly aggregate to form a large number of crystal nuclei, exhibiting a "burst nucleation" pattern. During this process, the platinum atom concentration in the reaction system rapidly decreases with the formation of crystal nuclei. Simultaneously, due to the steric hindrance effect of the dispersant molecular chains and the homogenization environment brought about by stirring, the newly generated platinum crystal nuclei are uniformly distributed in the dispersion, forming a stable platinum crystal nucleus dispersion system, laying the foundation for subsequent particle growth.

[0039] The second feeding stage (directional growth stage of platinum crystal nuclei): Chloroplatinic acid solution and hydrazine hydrate solution are added synchronously at a constant dropping rate, precisely controlled by a peristaltic pump at a constant dropping rate of 10 ml / min to 20 ml / min, ensuring a stable reduction rate of platinum atoms. During this stage, the concentration of newly generated platinum atoms remains below the critical nucleation concentration, significantly preventing secondary nucleation. Ultimately, these platinum atoms are directionally deposited on the surface of the stable crystal nuclei generated in the first stage through diffusion. Under the homogeneous environment provided by the dispersion, continuous stirring ensures consistent growth conditions for the platinum crystal nuclei, resulting in uniform growth of platinum particles.

[0040] In summary, this invention, through a two-step design of "explosive nucleation followed by directional deposition," combined with processes such as heating, precise speed control, dispersant synergy, and mechanical stirring, effectively solves the problems of uneven particle size and poor dispersibility caused by the chaotic nucleation and growth processes in traditional preparation methods. Ultimately, it obtains micron-sized spherical platinum powder with uniform particle size and excellent dispersibility, significantly improving the product quality stability and industrial application value. Attached Figure Description

[0041] Figure 1 This is a flowchart of a method for preparing highly dispersed micron-sized platinum powder according to the present invention;

[0042] Figure 2 The microstructure (magnification 10000x) and particle size distribution diagram of the platinum powder prepared in Example 1 of this invention are shown.

[0043] Figure 3 The microstructure (magnification 10000x) and particle size distribution diagram of the platinum powder prepared in Example 2 of this invention are shown.

[0044] Figure 4 The microstructure (magnification 10000x) and particle size distribution diagram of the platinum powder prepared in Comparative Example 1 of this invention are shown.

[0045] Figure 5 The images show the microstructure (magnification 10000x) and particle size distribution of the platinum powder prepared in Comparative Example 2 of this invention. Detailed Implementation

[0046] like Figure 1 As shown, a method for preparing highly dispersed micron-sized platinum powder includes the following steps:

[0047] 1) Preparation of precursor and reducing agent solution

[0048] Chloroplatinic acid was used as a precursor for preparing platinum powder, and hydrazine hydrate was used as a reducing agent for preparing platinum powder. Aqueous solutions of chloroplatinic acid with concentrations of 40 g / L to 200 g / L and aqueous solutions of hydrazine hydrate with concentrations of 20 g / L to 100 g / L were prepared respectively.

[0049] 2) Prepare the dispersion and preheat and maintain the temperature.

[0050] Using any one of polyvinylpyrrolidone (PVP), polyethylene glycol, or methylcellulose as a dispersant, the dispersant and deionized water are mixed and stirred until the dispersant is completely dissolved, according to a mass ratio of 1 g / L to 10 g / L. The dispersion is then heated to 70°C to 80°C and kept at this temperature for later use.

[0051] 3) Staged simultaneous dropwise addition of the reaction

[0052] Take equal volumes of the aqueous solutions of chloroplatinic acid and hydrazine hydrate prepared in step 1), and use a peristaltic pump to control the dropping rate of the aqueous solutions of chloroplatinic acid and hydrazine hydrate at a constant dropping rate of 10 ml / min to 20 ml / min. Add the solutions dropwise in two separate, uniform drops to the dispersion prepared in step 2) after incubation. Mechanical stirring is continuously performed during the dropping process.

[0053] After the first addition lasts for 1 to 3 minutes, the addition is paused and maintained for an interval of 3 to 5 minutes. After the interval, the second addition is performed until all the remaining aqueous solutions of chloroplatinic acid and hydrazine hydrate are added. Throughout the addition and reaction process, the dropping rate is kept constant, the mechanical stirring speed is controlled at 50 to 200 rpm, and the temperature of the dispersion is maintained at 70 to 80°C. After all the remaining aqueous solutions of chloroplatinic acid and hydrazine hydrate have been added, stirring is continued at the same stirring speed for 5 to 10 minutes. Then, stirring is stopped and the mixture is allowed to cool naturally to room temperature to obtain primary platinum powder 1.

[0054] 4) Graded washing and centrifugal separation

[0055] The primary platinum powder 1 obtained in step 3) is repeatedly washed with deionized water to remove the soluble byproducts generated in the reaction until the pH value of the washing solution reaches 7.0±0.5. The washed mixture is then centrifuged, the upper washing solution is poured off, and the precipitated platinum powder 2 is collected. An appropriate amount of anhydrous ethanol is added to the collected platinum powder 2, and after stirring and mixing evenly, it is centrifuged again to separate and remove the anhydrous ethanol, thus obtaining the purified platinum powder 3.

[0056] 5) Spread the purified platinum powder 3 obtained in step 4) on a petri dish and place it at room temperature for 10h to 24h. After the anhydrous ethanol has completely evaporated, highly dispersed micron platinum powder is obtained.

[0057] The following is an example of using the above method: Example 1

[0058] A method for preparing highly dispersed micron-sized platinum powder specifically includes the following steps:

[0059] S1. Prepare 1000 mL of chloroplatinic acid aqueous solution with a mass concentration of 50 g / L and 1000 mL of hydrazine hydrate aqueous solution with a mass concentration of 30 g / L.

[0060] S2. Using polyvinylpyrrolidone (PVP) as a dispersant, add 2.5g of PVP to 1000mL of deionized water, stir and mix evenly to obtain a dispersion, and heat the dispersion to 70℃ and keep it warm.

[0061] S3. Using a peristaltic pump to control the dropping rate at 10 ml / min, the aqueous solutions of chloroplatinic acid and hydrazine hydrate obtained in step S1 are added dropwise to the heat-preserving dispersion in step S2 in two separate drops. The first drop is added for 2 min, followed by a 3 min interval, and then the remaining solution is added dropwise.

[0062] Throughout the preparation process, the stirring speed was controlled at 100 r / min and the dispersion temperature was kept constant at 70℃. After the addition was completed, stirring was continued for 5 min to 10 min, then stirring was stopped and the mixture was allowed to cool naturally to room temperature to obtain primary platinum powder 1.

[0063] S4. The primary platinum powder 1 prepared in step S3 is repeatedly washed with deionized water to remove reaction byproducts until the pH of the washing solution is 7.0±0.5. After centrifugation, the upper washing solution is poured off to obtain platinum powder 2. An appropriate amount of anhydrous ethanol is added to the precipitated platinum powder 2, and after stirring and mixing evenly, it is centrifuged again to remove the anhydrous ethanol, and the purified platinum powder 3 is obtained.

[0064] S5. Spread the purified platinum powder 3 collected in step S4 on a petri dish and place it at room temperature for 24 hours. After the anhydrous ethanol has completely evaporated, highly dispersed micron platinum powder is obtained.

[0065] The highly dispersed micron-sized platinum powder obtained by the method described in Example 1 has the following performance characteristics: most platinum powder particles are spherical with smooth surfaces, and the particle size distribution is uniform (its microstructure is as follows). Figure 2 (As shown); the particle size distribution parameter of the platinum powder was measured by particle size analysis, and the particle size distribution parameter was: D 10 =0.57μm, D 50 =1.11μm, D 90 =2.49μm, with good overall dispersion and no obvious agglomeration between particles. Example 2

[0066] A method for preparing highly dispersed micron-sized platinum powder specifically includes the following steps:

[0067] S1. Prepare 1000 mL of chloroplatinic acid aqueous solution with a mass concentration of 50 g / L and 1000 mL of hydrazine hydrate aqueous solution with a mass concentration of 30 g / L.

[0068] S2. Using polyvinylpyrrolidone (PVP) as a dispersant, add 2.5g of PVP to 1000mL of deionized water, stir and mix evenly to obtain a dispersion, and heat the dispersion to 80℃ and keep it warm.

[0069] S3. Using a peristaltic pump to control the dropping rate at 10 ml / min, the aqueous solutions of chloroplatinic acid and hydrazine hydrate obtained in step S1 are added dropwise to the insulated dispersion in step S2 in two simultaneous drops; the first drop is added for 2 min, followed by a 3 min interval, and then the remaining solution is added dropwise.

[0070] Throughout the preparation process, the stirring speed was controlled at 100 r / min and the dispersion temperature was kept constant at 80℃. After the addition was completed, stirring was continued for 5 min to 10 min, then stirring was stopped and the mixture was allowed to cool naturally to room temperature to obtain primary platinum powder 1.

[0071] S4. The primary platinum powder 1 prepared in step S3 is repeatedly washed with deionized water to remove reaction byproducts until the pH of the washing solution is 7.0±0.5. After centrifugation, the upper washing solution is poured off to obtain platinum powder 2. An appropriate amount of anhydrous ethanol is added to the precipitated platinum powder 2, and after stirring and mixing evenly, it is centrifuged again to remove the anhydrous ethanol, and the purified platinum powder 3 is obtained.

[0072] S5. Spread the purified platinum powder 3 collected in step S4 on a petri dish and place it at room temperature for 24 hours. After the anhydrous ethanol has completely evaporated, highly dispersed micron platinum powder is obtained.

[0073] The highly dispersed micron-sized platinum powder obtained by the method described in Example 2 has the following performance characteristics: high overall sphericity, smooth surface of most platinum powder particles, and no obvious impurities adhering to them. Compared with the platinum powder obtained in Example 1 (reaction temperature of 70℃), the platinum powder obtained in Example 2 has better particle size uniformity and more uniform particle size distribution (its microstructure is as follows). Figure 3 (As shown); the particle size distribution parameter of the platinum powder was measured by particle size analysis, and the particle size distribution parameter was: D 10 =0.89μm, D 50 =1.33μm, D 90 =2.07μm, with excellent overall dispersibility and no agglomeration between particles.

[0074] Comparative Example 1

[0075] A method for preparing highly dispersed micron-sized platinum powder specifically includes the following steps:

[0076] S1. Prepare 1000 mL of chloroplatinic acid aqueous solution with a mass concentration of 50 g / L and 1000 mL of hydrazine hydrate aqueous solution with a mass concentration of 30 g / L.

[0077] S2. Using polyvinylpyrrolidone (PVP) as a dispersant, add 2.5g of PVP to 1000mL of deionized water, stir and mix evenly to obtain a dispersion, and heat the dispersion to 60℃ and keep it warm.

[0078] S3. Using a peristaltic pump to control the dropping rate at 10 ml / min, the aqueous solutions of chloroplatinic acid and hydrazine hydrate obtained in step S1 are added dropwise to the heat-preserving dispersion in step S2 in two simultaneous drops; the first drop is added for 1 min, followed by a 3 min interval, and then the remaining solution is added dropwise.

[0079] Throughout the preparation process, the stirring speed was controlled at 100 r / min, and the temperature of the dispersion was kept constant at 60℃. After the addition was completed, stirring was continued for 5 min to 10 min, then stirring was stopped and the mixture was allowed to cool naturally to room temperature to obtain primary platinum powder 1.

[0080] S4. The primary platinum powder 1 prepared in step S3 is repeatedly washed with deionized water to remove reaction byproducts until the pH of the washing solution is 7.0±0.5. After centrifugation, the upper washing solution is poured off to obtain platinum powder 2. An appropriate amount of anhydrous ethanol is added to the precipitated platinum powder 2, and after stirring and mixing evenly, it is centrifuged again to remove the anhydrous ethanol, and the purified platinum powder 3 is obtained.

[0081] S5. Spread the purified platinum powder 3 collected in step S4 on a petri dish and place it at room temperature for 24 hours. After the anhydrous ethanol has completely evaporated, highly dispersed micron platinum powder is obtained.

[0082] The highly dispersed micron-sized platinum powder obtained by the method described in Comparative Example 1 has the following performance characteristics: high sphericity and smooth surface, relatively large primary particle size, and some particles exhibiting a chain-like structure formed by the aggregation of two or more particles (its microstructure is as follows). Figure 4 (As shown); the particle size distribution parameter of the platinum powder was measured by particle size analysis, and the particle size distribution parameter was: D 10 =2.79μm, D 50 =3.81μm, D 90 =5.39μm, with poor overall dispersion.

[0083] Comparative Example 2

[0084] A method for preparing highly dispersed micron-sized platinum powder specifically includes the following steps:

[0085] S1. Prepare 1000 mL of chloroplatinic acid aqueous solution with a mass concentration of 50 g / L and 1000 mL of hydrazine hydrate aqueous solution with a mass concentration of 30 g / L.

[0086] S2. Using polyvinylpyrrolidone (PVP) as a dispersant, add 2.0g of PVP to 1000mL of deionized water, stir and mix evenly to obtain a dispersion, and heat the dispersion to 90℃ and keep it warm.

[0087] S3. Using a peristaltic pump to control the dropping rate at 10 ml / min, the aqueous solutions of chloroplatinic acid and hydrazine hydrate obtained in step S1 are added dropwise to the heat-preserving dispersion in step S2 in two simultaneous drops; the first drop is added for 1 min, followed by a 4 min interval, and then the remaining solution is added dropwise.

[0088] Throughout the preparation process, the stirring speed was controlled at 100 r / min, and the temperature of the dispersion was kept constant at 90℃. After the addition was completed, stirring was continued for 5 min to 10 min, then stirring was stopped and the mixture was allowed to cool naturally to room temperature to obtain primary platinum powder 1.

[0089] S4. The primary platinum powder 1 prepared in step S3 is repeatedly washed with deionized water to remove reaction byproducts until the pH of the washing solution is 7.0±0.5. After centrifugation, the upper washing solution is poured off to obtain platinum powder 2. An appropriate amount of anhydrous ethanol is added to the precipitated platinum powder 2, and after stirring and mixing evenly, it is centrifuged again to remove the anhydrous ethanol, and the purified platinum powder 3 is obtained.

[0090] S5. Spread the purified platinum powder 3 collected in step S4 on a petri dish and place it at room temperature for 24 hours. After the anhydrous ethanol has completely evaporated, highly dispersed micron platinum powder is obtained.

[0091] The highly dispersed micron-sized platinum powder obtained by the method described in Comparative Example 2 has the following performance characteristics: the platinum powder surface is smooth, and its primary particle size is smaller than that of the platinum powders prepared in Example 1 (70℃) and Example 2 (80℃), but there is obvious agglomeration between particles, and locally several particles are agglomerated into chain-like or plate-like structures (their micromorphology is as follows). Figure 5 (As shown); the particle size distribution parameter of the platinum powder was measured by particle size analysis, and the particle size distribution parameter was: D 10 =4.07μm, D 50 =8.89μm, D 90 =16.56μm. The above phenomenon indicates that as the reaction temperature increases (to 90℃), the thermal motion between platinum powder particles intensifies, the probability of particle collision increases, and the agglomeration of particles intensifies.

[0092] This invention, experimentally verified, employs a chemical liquid-phase reduction method. Under a heated environment, the chloroplatinic acid precursor solution and hydrazine hydrate reducing agent solution are simultaneously added dropwise to a dispersion in two stages, successfully achieving effective separation of the platinum atom nucleation and growth stages. The core feeding mode of this invention is "short-time dropwise addition to initiate explosive nucleation, intermittent stabilization of the nuclei, and subsequent continuous addition to achieve directional growth." It utilizes a peristaltic pump for precise speed control and continuous mechanical stirring, providing a controllable environment for the uniform growth of platinum powder particles, which is crucial for ensuring the core performance of highly dispersed micron-sized platinum powder.

[0093] Based on the temperature variation comparison experiments of Examples 1 and 2 and Comparative Examples 1 and 2 (reaction temperatures of 70℃, 80℃, 60℃, and 90℃, respectively), it can be seen that the morphology and dispersibility of micron-sized platinum powder are closely related to the reaction temperature, and the specific control rules are as follows:

[0094] 1. When the reaction temperature is low (e.g., 60℃ in Comparative Example 1), the steric hindrance effect of the dispersant PVP is weak, the reaction rate is relatively slow, resulting in a larger primary particle size of platinum powder (D). 50 =3.81μm), poor uniformity and chain-like agglomeration;

[0095] 2. As the temperature increases (e.g., 70°C in Example 1), the primary particle size of the platinum powder decreases significantly (D... 50 =1.11μm), improved uniformity, and enhanced dispersibility;

[0096] 3. When the temperature reaches 80℃ (as in Example 2), the optimal process effect is achieved, and the prepared platinum powder has high sphericity, smooth surface, and the most concentrated particle size distribution (D). 10 =0.89μm, D 50 =1.33μm, D90=2.07μm), and there is no aggregation between particles, exhibiting excellent dispersibility;

[0097] 4. When the temperature is further increased (e.g., 90℃ in Comparative Example 2), the thermal motion of the platinum powder particles intensifies, the probability of collision and agglomeration between particles increases, forming chain-like and plate-like aggregates, and the particle size distribution widens (D). 50 =8.89μm), resulting in deteriorated dispersion.

[0098] In summary, this invention achieves precise control over the morphology and dispersibility of platinum powder through a process design of "stepwise feeding + parameter control". 80℃ is the optimal reaction temperature, under which micron-sized spherical platinum powder with uniform particle size and good dispersibility can be stably prepared.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing highly dispersed micron-sized platinum powder, characterized in that, Includes the following steps: 1) Take equal volumes of aqueous solutions of chloroplatinic acid and hydrazine hydrate, and simultaneously add them dropwise to a dispersion at 70℃~80℃, stirring continuously while maintaining the dispersion temperature at 70℃~80℃ throughout the process; the aqueous solutions of chloroplatinic acid and hydrazine hydrate are added in two steps, the first addition lasting 1min~3min with an interval of 3min~5min, and the second addition of the remaining solution followed by stirring for 5min~10min; cool to room temperature to obtain platinum powder 1; 2) The platinum powder 1 obtained in step 1) is repeatedly washed with deionized water until the pH of the washing solution is 7.0±0.5, and then centrifuged to obtain platinum powder 2; platinum powder 2 is washed with anhydrous ethanol and then centrifuged to obtain platinum powder 3. 3) The platinum powder obtained in step 2) is left at room temperature for 10h to 24h to obtain highly dispersed micron platinum powder.

2. The preparation method according to claim 1, characterized in that, In step 1), the concentration of the chloroplatinic acid aqueous solution is 40 g / L to 200 g / L, and the concentration of the hydrazine hydrate aqueous solution is 20 g / L to 100 g / L.

3. The preparation method according to claim 1, characterized in that, In step 1), the dripping is done at a constant rate of 10 ml / min to 20 ml / min.

4. The preparation method according to claim 1, characterized in that, In step 1), the preparation process of the dispersion includes: mixing and stirring the dispersant at a mass ratio of 1 g / L to 10 g / L of deionized water to obtain the dispersion.

5. The preparation method according to claim 4, characterized in that, In step 1), the dispersant is any one of polyvinylpyrrolidone, polyethylene glycol, and methylcellulose.

6. The preparation method according to claim 1, characterized in that, In step 1), the stirring is mechanical stirring with a stirring speed of 50 r / min to 200 r / min.

7. The preparation method according to claim 1, characterized in that, Chloroplatinic acid is the precursor, and hydrazine hydrate is the reducing agent.

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