A method for preparing platinum black nanoparticle powder

Abstract

The invention discloses a method for preparing platinum black nanoparticle powder, and relates to the technical field of purification of platinum group metals in precious metal smelting. The method comprises the following steps: first preparing an organic alcohol solution of a platinum salt, adding a sodium hydroxide aqueous solution and mixing uniformly, and then placing the mixture in an ultrasonic reactor for reaction after uniform dispersion. After the reaction is completed, centrifuging to separate a platinum nanoparticle precipitate, placing the platinum nanoparticles in pure water, and repeatedly ultrasonically washing the platinum nanoparticles to remove organic matter and impurity ions; using a solvent exchange method to disperse the platinum nanoparticles in a hot saturated ammonium carbonate aqueous solution, followed by cooling and solid-liquid separation; and heat-treating the solid-phase product to obtain a platinum nanoparticle product. The method has simple process, low cost, low platinum particle loss rate, and the obtained product has good electrochemical activity, large specific surface area, and low apparent density.

Description

Technical Field

[0001] The present invention relates to the technical field of purification of platinum group metals in precious metal smelting, and in particular to a method for preparing platinum black nanoparticle powder. Background Art

[0002] Platinum black nanoparticles (PtBNPs) are black powders that have become a research hotspot in materials science due to their unique nanostructure and surface properties. They possess unique properties such as high surface area, excellent photocatalytic performance, and excellent chemical stability. These characteristics make PtBNPs important for catalysis in hydrogenation, oxidation, selective addition, room-temperature catalytic combustion, and hydrogen production. They also have a wide range of applications in sensing, biomedicine, and energy.

[0003] The main methods for preparing platinum black are chemical reduction and electrochemical methods. In the electrochemical method, platinum salt serves as the anode and electric current serves as the reducing agent. The problem is that it is difficult to obtain solid-phase platinum black powder. In the chemical reduction method, commonly used reducing agents include formaldehyde, hydrazine, sodium formate, sodium borohydride, etc. These reducing agents can reduce chloroplatinic acid to platinum black under certain conditions, and production is achieved through intermittent feeding and unloading of materials in a liquid phase reactor. The problems it has include high energy consumption, strong reducing agents causing the platinum nanocrystals that nucleate and grow in the liquid phase to grow rapidly and agglomerate, making it difficult to achieve a uniform micromorphology of nanoparticles in the catalyst, and the above-mentioned strong reducing agents are highly polluting and the cost of post-processing is high. The use of a weak reducing agent system to perform a liquid phase cluster method for the synthesis of platinum black nanoparticles can effectively avoid these problems. However, this method also has defects, mainly in that during the process of dispersing from the liquid phase to the solid phase powder, due to the interaction between the platinum nanoparticles and water, the platinum secondary particles further agglomerate, resulting in performance loss, and other drying methods have complex processes, high costs, and low yields.

[0004] In summary, how to prepare platinum black with high electrochemical activity, small particle size, high yield and low cost has become an urgent problem in the field. Therefore, a method for preparing platinum black nanoparticle powder is urgently needed to solve this problem. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing platinum black nanoparticle powder to solve the problems mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing platinum black nanoparticle powder, comprising the following steps:

[0007] Step S1: preparing platinum nanoparticles by an ultrasonic liquid phase method; first, preparing an organic alcohol solution of a platinum salt, adding an aqueous sodium hydroxide solution and mixing evenly, and then placing the solution in an ultrasonic reactor for reaction after uniform dispersion. After the reaction is complete, centrifuging to separate the platinum nanoparticle precipitate, and then placing the platinum nanoparticles in pure water and repeatedly ultrasonically washing them to remove organic matter and impurity ions;

[0008] Step S2: dispersing the platinum nanoparticles in a hot saturated ammonium carbonate aqueous solution using a solvent exchange method, followed by cooling and solid-liquid separation;

[0009] Step S3: heat-treating the solid phase product obtained in S2 to obtain a platinum nanoparticle product.

[0010] Preferably, in the above step S1, in the mixed solution of the organic alcohol solution of the platinum salt and the sodium hydroxide, the molar ratio of sodium ions to platinum ions is 1:3-1:8; and the reaction temperature in the ultrasonic reactor is 60-80°C.

[0011] Optionally, in the above preferred embodiment, the concentration of platinum ions in the organic alcohol solution of the platinum salt is 0.05 to 0.2 mol / L, the organic alcohol includes one or more of methanol, ethanol, ethylene glycol, and isopropanol, and the platinum salt includes one or more of chloroplatinic acid, ammonium chloroplatinate, platinum cyclamate, and ammonium nitrosoplatinum; and the concentration of the aqueous sodium hydroxide solution is 0.1 to 1 mol / L.

[0012] In the above preferred embodiment, the ultrasonic power of the ultrasonic reactor is 900-1400 kW, and the reaction time is 0.8-1.5 h.

[0013] Preferably, the temperature of the hot saturated aqueous ammonium carbonate solution is 50-70°C, and the temperature is lowered to 15-25°C.

[0014] Preferably, in the above step S3, the heat treatment temperature is 150-200° C., and the treatment time is 2-4 hours.

[0015] Another technical solution provided by the present invention is that the platinum nanoparticle product prepared according to the above preparation method has an average particle size of less than 130nm and an ECSA greater than 36g / m 2 , with a specific surface area greater than 51m 2 / g.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The preparation method of the platinum black nanoparticle powder uses ammonium carbonate, which is easily decomposed into a gaseous state, as a carrier, which is highly environmentally friendly and low in cost. The easily decomposable carrier leaves no residue in the nanoparticle product. The process is simple and easy to operate, and the fewer post-processing steps for nanoparticle preparation can effectively improve the yield of the powder product compared with other methods. In addition, since the platinum nanoparticles prepared by the ultrasonic liquid phase method have a relatively small and uniform particle size distribution, their agglomeration during the preparation process can be avoided, which is more conducive to utilizing the difference in the solubility of ammonium carbonate at different temperatures, so that this easily decomposable salt is precipitated as a carrier during the drying process of the platinum nanoparticles, reducing the agglomeration of the platinum nanoparticles loaded thereon during the drying process, ensuring that the platinum nanoparticles are completely decomposed as the temperature rises during the final heat treatment process, thereby achieving the purpose of removing the carrier to obtain the nanoparticle product and reducing the possibility of ammonium carbonate residue.

[0018] 2. The preparation method of the platinum black nanoparticle powder is based on the ultrasonic liquid phase method for preparing platinum nanoparticles, and does not adopt an overly complex drying process flow, making the entire process simple, low-cost, and low-loss rate of platinum particles.

[0019] 3. The preparation method of the platinum black nanoparticle powder can effectively reduce the bulk density of the powder and improve its performance. The obtained product has better electrochemical activity and higher specific surface area. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a transmission electron microscope (TEM) microscopic morphology image of platinum nanoparticles in the aqueous dispersion of platinum nanoparticles in Example 1 of the present invention.

[0021] Figure 2 This is a transmission electron microscope (TEM) microscopic morphology image of platinum nanoparticles in the aqueous dispersion of platinum nanoparticles in Comparative Example 1 of the present invention.

[0022] Figure 3 This is the X-ray diffraction spectrum (XRD) of the nano-platinum product obtained after heat treatment in Example 1 of the present invention.

[0023] Figure 4 These are the electrochemical specific surface area test results of the nano-platinum products obtained after heat treatment in the examples of the present invention and the comparative examples. DETAILED DESCRIPTION

[0024] A method for preparing platinum black nanoparticle powder comprises the following steps:

[0025] Step S1: preparing platinum nanoparticles by an ultrasonic liquid phase method; first, preparing an organic alcohol solution of a platinum salt, adding an aqueous sodium hydroxide solution and mixing evenly, and then placing the solution in an ultrasonic reactor for reaction after uniform dispersion. After the reaction is complete, centrifuging to separate the platinum nanoparticle precipitate, and then placing the platinum nanoparticles in pure water and repeatedly ultrasonically washing them to remove organic matter and impurity ions;

[0026] Step S2: dispersing the platinum nanoparticles in a hot saturated ammonium carbonate aqueous solution using a solvent exchange method, followed by cooling and solid-liquid separation;

[0027] Step S3: heat-treating the solid phase product obtained in S2 to obtain a platinum nanoparticle product.

[0028] In order to obtain a larger specific surface area for the product, the following parameters can be further adopted in the above method: in step S1, the molar ratio of sodium ions to platinum ions in the mixed solution of the organic alcohol solution of the platinum salt and the sodium hydroxide is 1:3-1:8; the reaction temperature in the ultrasonic reactor is 60-80°C. Under these conditions, the average particle size of the obtained platinum nanoparticle product is less than 130nm and the ECSA is greater than 36g / m 2 , with a specific surface area greater than 51m 2 / g.

[0029] The specific concentrations and raw materials are selected for reference: the concentration of platinum ions in the organic alcohol solution of platinum salt is 0.05 to 0.2 mol / L, the organic alcohol includes one or more of methanol, ethanol, ethylene glycol, and isopropanol, and the platinum salt includes one or more of chloroplatinic acid, ammonium chloroplatinate, platinum cyclamate, and ammonium nitrosoplatinum; the concentration of the aqueous sodium hydroxide solution is 0.1 to 1 mol / L. It should be noted that these specific concentrations and raw materials are not absolutely necessary conditions for the product to obtain a large specific surface area, but are merely reference examples given for the convenience of implementation.

[0030] In addition, in order to ensure stable product performance, the ultrasonic power of the ultrasonic reactor can be 900-1400kW. Generally, a slight change in this power will not have a significant impact on the results. The power given here is only for the convenience of implementation; the reaction time is 0.8-1.5h. Similarly, a slight increase in the reaction time usually does not have a significant impact on the product. The time given here is only a reference to the complete reaction time, and the specific time can be selected according to actual conditions and material amount.

[0031] For reference, the temperature of the hot saturated ammonium carbonate aqueous solution can be selected to be 50-70°C, and can be cooled to 15-25°C.

[0032] The heat treatment step is a conventional step in the art. In this method, it is mainly for decomposing ammonium carbonate into ammonia, carbon dioxide and water vapor. The starting decomposition temperature of ammonium carbonate is 150°C. Therefore, in the above step S3, the heat treatment temperature is optional, 150-200°C, and the treatment time is 2-4h. Appropriately increasing the temperature and adjusting the heat treatment time within the heat treatment range known in the art will not affect the results.

[0033] The above implementation is further described below through several examples.

[0034] Example 1:

[0035] 5.22g of chloroplatinic acid was completely dissolved in 300mL of ethylene glycol. The solution was placed in an ultrasonic reactor. 100mL of a 0.05M sodium hydroxide aqueous solution was added to the reactor. The reactor was then opened and heated to 65°C to initiate the reaction. The ultrasonic power was 1200kW and the reaction time was 1h. The reaction solution was then cooled and centrifuged to obtain a platinum nanoparticle precipitate. The solution was washed three times with deionized water to obtain an aqueous dispersion of platinum nanoparticles. The microscopic morphology of the dispersion was captured using a transmission electron microscope (TEM). Figure 1 .

[0036] The pure water in the dispersion was exchanged with a saturated ammonium carbonate aqueous solution at 55°C prepared in advance by a solvent exchange method. The dispersion was then cooled to 15°C. White flocculent ammonium carbonate precipitated in the dispersion. The dispersion was filtered to obtain nano-platinum supported on ammonium carbonate. The product was heat-treated at 160°C for 2.5 hours to obtain a nano-platinum product, which is designated as Example 1. The X-ray diffraction spectrum (XRD) test yielded a spectrum as shown in FIG. Figure 3 .

[0037] Example 2:

[0038] 8.70g of chloroplatinic acid was completely dissolved in 500mL of ethylene glycol. The solution was placed in an ultrasonic reactor. 100mL of 0.05M sodium hydroxide aqueous solution was added to the reactor. The reactor was then opened and heated to 75°C to start the reaction. The ultrasonic power was 1000kW and the reaction time was 0.8h. The reaction solution was then cooled and centrifuged to obtain a platinum nanoparticle precipitate. The solution was washed repeatedly with deionized water three times to obtain an aqueous dispersion of platinum nanoparticles. The microscopic morphology of the solution was captured using a transmission electron microscope (TEM). Figure 2 .

[0039] The pure water in the dispersion was exchanged with a pre-prepared saturated aqueous ammonium carbonate solution at 60°C using a solvent exchange method. The dispersion was then cooled to 15°C, and white flocculent ammonium carbonate precipitated in the dispersion. The dispersion was filtered to obtain nano-platinum supported on ammonium carbonate. The product was heat treated at 190°C for 2 hours to obtain a nano-platinum product, which is recorded as Example 2.

[0040] Example 3:

[0041] 12.91g of chloroplatinic acid was completely dissolved in 1000mL of ethylene glycol, and the solution was placed in an ultrasonic reactor. 0.1L of 0.05M sodium hydroxide solution was added to the reactor. The reactor was then opened and heated to 80°C to start the reaction. The ultrasonic power was 1200kW and the reaction time was 1h. The reaction solution was then cooled and centrifuged to obtain a platinum nanoparticle precipitate. The solution was washed repeatedly with deionized water three times to obtain an aqueous dispersion of platinum nanoparticles. The pure water in the dispersion was exchanged with a saturated ammonium carbonate aqueous solution at 65°C configured in advance using a solvent exchange method. The dispersion was then cooled to 20°C and a white flocculent ammonium carbonate precipitate was found in the dispersion. The dispersion was filtered to obtain a nano-platinum loaded on ammonium carbonate. The product was placed in a heat treatment at 200°C for 2h to obtain a nano-platinum product, which is designated as Example 3.

[0042] Example 4:

[0043] Take 10.05g of chloroplatinic acid and completely dissolve it in 600mL of ethylene glycol. Place the solution in an ultrasonic reactor and add 0.1L of 0.05M sodium hydroxide aqueous solution to the reactor. Then open the reactor and heat it to 60℃ to start the reaction. The ultrasonic power is 1400kW and the reaction time is 1h. The reaction solution is then cooled and centrifuged to obtain platinum nanoparticles. It is washed repeatedly with deionized water 3 times to obtain an aqueous dispersion of platinum nanoparticles. Use solvent exchange method to replace the pure water in the dispersion with 70 ℃ The dispersion was cooled to 23°C and white flocculent ammonium carbonate precipitated in the dispersion. The dispersion was filtered to obtain nano-platinum supported on ammonium carbonate. The product was heat-treated at 170°C for 4 hours to obtain a nano-platinum product, which is recorded as Example 4.

[0044] Comparative Example 1:

[0045] 5.22g of chloroplatinic acid was completely dissolved in 300mL of ethylene glycol, and the solution was placed in an ultrasonic reactor. 0.1L of a 0.05M aqueous sodium hydroxide solution was added to the reactor. The reactor was then opened and heated to 65°C to start the reaction. The ultrasonic power was 1200kW and the reaction time was 1h. The reaction solution was then cooled and centrifuged to obtain a platinum nanoparticle precipitate. The solution was washed repeatedly with deionized water three times to obtain an aqueous dispersion of platinum nanoparticles. The dispersion was filtered to obtain a nano-platinum filter cake. The product was heat-treated at 160°C for 2.5h to obtain a nano-platinum product powder, which was recorded as Comparative Example 1.

[0046] Commercial samples were purchased from the market and used in the test experiments together with the above examples and comparative examples. The test results are shown in Table 1 below (the electrochemical specific surface area test results are shown in Table 1 below). Figure 4 ):

[0047] Table 1 Test results

[0048] Yield / % Average particle size / nm <![CDATA[ECSA / g*m -2 ]]> <![CDATA[Bulk density / g*cm -3 > <![CDATA[Specific surface area / m 2 *g -1 > Commercial samples / 192 25.1 0.9 39.7 Experimental Example 1 95.7 121 38.3 0.71 52.3 Experimental Example 2 96.3 116 36.5 0.76 51.3 Example 3 97.0 118 36.1 0.69 53.1 Example 4 96.6 112 38.9 0.73 51.9 Comparative Example 1 96.6 468 17.5 1.35 27.8

[0049] Test result analysis

[0050] 1) Electron microscopy results

[0051] like Figure 1-2 The following are transmission electron micrographs of platinum nanoparticles synthesized in Example 1 and Comparative Example 1, respectively. As can be seen from the figures, the platinum nanoparticles obtained in Example 1 are approximately 3-7 nm in size, with lattice fringes visible on the surface. Compared to the sample in Example 1, the nanoparticles in Comparative Example 1 exhibit more severe agglomeration. Therefore, it can be concluded that the use of a degradable template method can effectively mitigate the agglomeration behavior of platinum nanoparticles during drying, improve the pore structure of the secondary agglomerated particles, and reduce their size.

[0052] 2) X-ray diffraction results

[0053] like Figure 3 As shown in Table 1, X-ray diffraction results confirm that only platinum is present in the synthesized product. Furthermore, product yield testing reveals that this process yields a very high platinum product.

[0054] 3) Oxygen reduction activity test results

[0055] The electrochemical activity of the synthesized platinum nanoparticles was tested using the RDE three-electrode system and electrochemical workstation. Figure 4The results of cyclic voltammetry (CV) testing of the electrochemically active surface area of ​​platinum metal show that the redox peak areas of the curves for Examples 1, 2, and 3 are higher than those for commercial platinum black and significantly higher than those for the comparative example. The electrochemically active surface area (ECSA) of the samples was calculated, and the results are shown in Table 1. The ECSA results for the examples are significantly higher, which is consistent with the electron microscopy results above. Therefore, we believe that the degradable template method described herein can effectively improve the electrochemical activity of nano-platinum catalyst powders.

[0056] 4) Pore structure and size test

[0057] The obtained nano-platinum samples were tested for specific surface area (BET), apparent density, and particle size. The test results are shown in Table 1. It can be seen that the nano-platinum catalyst prepared in the example has a higher specific surface area, lower apparent density, and smaller particle size than the comparative example and commercial samples. In this patent, the use of a degradable template method can effectively improve the pore structure of the nano-platinum particles, increase their specific surface area, and reduce particle agglomeration during the preparation process.

[0058] In summary, the present invention proposes a novel biodegradable template method for preparing platinum nanoparticles. Compared to other existing methods, the present invention utilizes a biodegradable carrier salt, ammonium carbonate, which precipitates as a carrier for the platinum nanoparticles during cooling during the production process and decomposes into a gaseous state during the final drying process. This effectively reduces porosity loss during the drying process of the nanoplatinum particles and reduces nanoparticle agglomeration. Furthermore, the production process does not significantly increase the number of process steps, and the process is simple and low-cost, which helps minimize the loss of nanoplatinum product during the process, offering multiple advantages.

[0059] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims.

[0060] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A method for preparing platinum black nanoparticle powder, characterized in that: The following steps are involved: Step S1: preparing platinum nanoparticles by an ultrasonic liquid phase method; first, preparing an organic alcohol solution of a platinum salt, adding an aqueous sodium hydroxide solution and mixing evenly, and then placing the solution in an ultrasonic reactor for reaction after uniform dispersion. After the reaction is complete, centrifuging to separate the platinum nanoparticle precipitate, and then placing the platinum nanoparticles in pure water and repeatedly ultrasonically washing them to remove organic matter and impurity ions; Step S2: dispersing the platinum nanoparticles in a hot saturated ammonium carbonate aqueous solution using a solvent exchange method, followed by cooling and solid-liquid separation; Step S3: heat-treating the solid phase product obtained in S2 to obtain a platinum nanoparticle product.

2. The method for preparing platinum black nanoparticle powder according to claim 1, wherein: In step S1, in the mixed solution of the organic alcohol solution of the platinum salt and the sodium hydroxide, the molar ratio of sodium ions to platinum ions is 1:3-1:8; and the reaction temperature in the ultrasonic reactor is 60-80°C.

3. The method for preparing platinum black nanoparticle powder according to claim 2, wherein: The platinum ion concentration in the organic alcohol solution of the platinum salt is 0.05-0.2 mol / L, the organic alcohol includes one or more of methanol, ethanol, ethylene glycol, and isopropanol, and the platinum salt includes one or more of chloroplatinic acid, ammonium chloroplatinate, platinum cyclamate, and ammonium nitrosoplatinum; and the concentration of the aqueous sodium hydroxide solution is 0.1-1 mol / L.

4. The method for preparing platinum black nanoparticle powder according to claim 2, wherein: The ultrasonic power of the ultrasonic reactor is 900-1400 kW, and the reaction time is 0.8-1.5 h.

5. The method for preparing platinum black nanoparticle powder according to claim 1, wherein: The temperature of the hot saturated ammonium carbonate aqueous solution is 50-70°C, which is cooled to 15-25°C.

6. The method for preparing platinum black nanoparticle powder according to claim 1, characterized in that: In step S3, the heat treatment temperature is 150-200° C., and the treatment time is 2-4 hours.

7. The platinum nanoparticle product obtained by the method for preparing platinum black nanoparticle powder according to claim 1, characterized in that: The average particle size of the platinum nanoparticle product is less than 130 nm, and the ECSA is greater than 36 g / m 2 , with a specific surface area greater than 51m 2 / g.

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