A method for preparing iridium-coated gallium micro-nano spheres by chemical reduction

Abstract

This invention relates to a method for preparing iridium-coated gallium micro / nanospheres via chemical reduction. The method first involves ultrasonically treating and drying gallium, then dispersing the treated gallium micro / nanospheres in deionized water. Next, a reducing agent solution prepared from a reducing agent and deionized water is added and thoroughly mixed under magnetic stirring. Then, chloroiridium acid is dissolved in deionized water to form an iridium precursor solution, which is added dropwise to the above mixture under heating and stirring. After the reaction is complete, the mixture is allowed to stand, centrifuged, washed, and dried to obtain iridium-coated gallium micro / nanospheres. This invention offers a simple process, mild reaction conditions, requires no complex equipment, provides high coating uniformity and strong coverage, easily adjustable process parameters, good repeatability, and is suitable for further scale-up and batch production.

Description

Technical Field

[0001] This invention relates to a method for preparing iridium-coated gallium micro / nanospheres by chemical reduction, belonging to the field of composite material preparation technology. Background Technology

[0002] Gallium is a metallic material with a low melting point, good fluidity, and unique physicochemical properties, making it valuable for research in functional materials, composite materials, and catalytic materials. Bulk gallium can be dispersed into micro / nano-scale particles or micro / nanospheres through methods such as ultrasonic dispersion, thereby increasing the specific surface area of ​​gallium and providing a good matrix for further surface modification and composite structure construction.

[0003] Metallic iridium possesses excellent chemical stability, corrosion resistance, and surface reactivity, making it an important noble metal functional material. However, iridium resources are relatively scarce and costly, and using bulk iridium or large quantities of iridium material is not conducive to the full utilization of the iridium component. Therefore, dispersing iridium in the form of a coating layer on the surface of other materials is beneficial to improving the dispersion and surface exposure of iridium, and composite materials with special structures and properties can be obtained through interfacial interactions between different components.

[0004] Combining iridium and gallium to construct iridium-coated gallium composite structures offers several advantages. Firstly, gallium micro / nanospheres serve as a substrate, providing a larger surface area for iridium deposition. Secondly, the iridium coating layer on the gallium surface enhances the dispersion of the iridium component and establishes an interfacial structure between iridium and gallium. Therefore, iridium-coated gallium micro / nanospheres hold potential application value in functional materials and related fields.

[0005] Existing methods for preparing metal surface coatings and noble metal composites mainly include physical deposition, electrochemical deposition, chemical reduction, and other multi-step methods. Some methods suffer from problems such as complex preparation processes, high equipment requirements, difficulty in controlling reaction conditions, and insufficient coating uniformity. Furthermore, when preparing iridium-coated gallium composites under liquid-phase conditions, it is necessary to address issues such as the easy aggregation of gallium micro / nano particles, the dispersion of iridium species, difficulty in controlling the deposition process, and uneven surface coating. Therefore, developing a preparation method that is simple in process, has mild reaction conditions, easily controllable parameters, and can form a uniform iridium coating layer on the surface of gallium micro / nanospheres is of great significance. Summary of the Invention

[0006] To address the problems of easy particle aggregation, uneven dispersion of precious metals, difficulty in controlling the coating effect, and complex preparation process in existing metal composite material preparation processes, this invention provides a method for preparing iridium-coated gallium micro / nanospheres by chemical reduction.

[0007] This invention first involves adding metallic gallium to an alcohol solvent and then dispersing it into micro / nano particles through ultrasonic treatment. After settling, centrifugation, and removal of excess solvent, the resulting gallium micro / nano particles are obtained. Subsequently, the obtained gallium micro / nano particles are dispersed in a solvent, and polyvinylpyrrolidone is added to maintain a good dispersion state, resulting in a gallium micro / nanosphere suspension.

[0008] A reducing agent solution, wherein the reducing agent is glucose or ascorbic acid, is prepared by dissolving a reducing agent in deionized water; an iridium source solution is prepared by dissolving chloroiridic acid in deionized water. Under magnetic stirring and heating conditions, the reducing agent is thoroughly mixed with a suspension of gallium micro / nanospheres, and the iridium source solution is added dropwise to the mixture. After the addition is complete, the reaction continues for a certain period of time at a preset temperature, allowing iridium ions to be reduced under the action of the reducing agent, and to nucleate, deposit, and grow in situ on the surface of the gallium micro / nanospheres, thereby forming an iridium coating layer.

[0009] After the reaction was completed, the product was allowed to stand and centrifuged. It was then washed with deionized water to remove residual reactants and soluble impurities, and then dried at a preset temperature to finally obtain iridium-coated gallium micro-nanospheres.

[0010] This invention utilizes the reducing effect of a reducing agent on iridium ions and the dispersing and stabilizing effect of polyvinylpyrrolidone on gallium micro / nanospheres, enabling iridium species to be reduced, nucleated, and deposited in situ on the surface of gallium micro / nanospheres, forming an iridium-coated gallium micro / nanosphere structure. The method of this invention is simple to operate, with mild reaction conditions, requiring no complex preparation equipment, and the process parameters are easy to control. The obtained material exhibits good coating effect and structural uniformity, as well as good reproducibility, and is suitable for further scale-up preparation.

[0011] A method for preparing iridium-coated gallium micro / nanospheres by chemical reduction, the specific steps of which are as follows: (1) Liquid gallium metal was ultrasonically dispersed in a solvent to obtain a suspension of gallium micro-nano particles. After standing, it was washed and dried multiple times with deionized water and ethanol. (2) Add the dried gallium micro-nanoparticles to the polyvinylpyrrolidone solution, mix and stir evenly to obtain gallium micro-nanoparticles; (3) Weigh a certain amount of reducing agent and dissolve it in deionized water, then add it dropwise to an aqueous solution containing gallium and stir until homogeneous; (4) Weigh a certain amount of chloroiridium acid and dissolve it in deionized water. Add it dropwise to the above solution under stirring and heating conditions. After the addition is completed, continue the reaction at a constant temperature. (5) After the reaction is complete, allow the product to cool naturally to room temperature, remove the product that has settled naturally, centrifuge it, and wash it several times. (6) The cleaned powder is dried at a preset temperature to obtain iridium-coated gallium micro / nanosphere powder.

[0012] The solvent used in step (1) is one of ethanol, isopropanol, and propanol.

[0013] In step (1), the concentration of gallium micro / nanoparticle suspension is 5~20 g / L.

[0014] The concentration of the polyvinylpyrrolidone solution in step (2) is 0.8–3.45 μmol / L. The reducing agent in step (3) is one or more of ascorbic acid, glucose and tartaric acid.

[0015] The concentration of the reducing agent in step (3) is 0.05~0.5 mol / L.

[0016] The concentration of chloroiridium acid in step (4) is 0.02 to 0.2 mol / L.

[0017] The heating temperature in step (4) is 60~100 ℃, and the constant temperature reaction time is 1~4 h.

[0018] The dropping rate in step (4) is 1~10 mL / min.

[0019] The drying temperature in step (5) is 20~50 ℃ and the drying time is 6~12 h.

[0020] The mechanism of the chemical reduction method for preparing iridium-coated gallium micro / nanospheres in this invention is as follows: The mechanism is mainly based on dispersion stabilization, interfacial adsorption, and chemical reduction deposition processes. First, gallium metal is ultrasonically treated to form gallium micro / nanospheres. Polyvinylpyrrolidone (PVP) improves the dispersion and stability of the particles in the reaction system and reduces particle aggregation through adsorption on the surface of the gallium micro / nanospheres. Simultaneously, the carbonyl groups in the PPVP molecule can coordinate or adsorb with iridium species in the system, which is beneficial for regulating the distribution and nucleation process of iridium species on the surface of the gallium micro / nanospheres. Upon addition of chloroiridic acid, the iridium chloride complex is gradually reduced under the action of a reducing agent. The reduced iridium species preferentially nucleate heterogeneously on the surface of the gallium micro / nanospheres and continue to deposit and grow with the continuous reduction reaction. Under magnetic stirring and heating, iridium gradually covers the surface of the gallium micro / nanospheres, eventually forming a relatively continuous and uniform iridium coating layer. Factors such as reducing agent concentration, iridium source concentration, polyvinylpyrrolidone dosage, dropping acceleration rate, reaction temperature, and reaction time collectively affect the reduction rate, nucleation density, and deposition process of iridium. By controlling these parameters, iridium-coated gallium micro / nanospheres with good coating uniformity and coverage can be obtained.

[0021] The beneficial effects of this invention are: (1) Advantages of the coating structure: This invention uses gallium micro-nanospheres as the substrate and uses liquid phase chemical reduction to enable iridium species to nucleate, deposit and grow on its surface in situ, which is conducive to forming a relatively uniform iridium coating layer and obtaining iridium-coated gallium micro-nanospheres with a clear structure.

[0022] (2) Good dispersion performance: By adding polyvinylpyrrolidone to the reaction system, the dispersion stability of gallium micro-nanospheres in the liquid system can be improved, the aggregation between particles can be reduced, and the iridium species can be uniformly distributed and deposited on the surface of gallium micro-nanospheres.

[0023] (3) The coating process is easy to control: By adjusting process parameters such as iridium source concentration, reducing agent concentration, reaction temperature, reaction time and drop acceleration rate, the reduction and deposition process of iridium can be controlled, thereby achieving the adjustment of the degree of iridium coating and surface structure.

[0024] (4) Flexible selection of reducing agent: The present invention uses a chemical reduction method to prepare iridium-coated gallium micro-nanospheres. The reducing agent can be glucose or ascorbic acid, which makes the preparation method have good process adaptability and adjustability.

[0025] (5) Simple synthesis process: The present invention adopts liquid phase chemical reduction method, which does not require complicated high temperature and high pressure equipment, the reaction conditions are relatively mild, the preparation steps are simple, the process parameters are easy to control, it has good repeatability, and it is suitable for further scale-up preparation.

[0026] (6) Wide range of applications: The iridium-coated gallium micro-nanospheres prepared by this invention have the structural characteristics of both gallium matrix and iridium coating, and have rich metal interfaces and good surface controllability. They can be used as a new type of metal composite material in catalysis, energy conversion, functional materials and other related fields, and have good application potential. Attached Figure Description

[0027] Figure 1 The images shown are SEM and EDS images of the iridium-coated gallium micro / nanospheres prepared in Example 1. Figure 2 The images shown are SEM and EDS images of the iridium-coated gallium micro / nanospheres prepared in Example 2. Figure 3 The images shown are SEM and EDS images of the iridium-coated gallium micro / nanospheres prepared in Example 3. Figure 4 The image shows the XRD pattern of the iridium-coated gallium micro / nanospheres prepared in the examples. Figure 5 The particle size distribution diagram of the iridium-coated gallium micro / nanospheres prepared in the examples is shown. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0029] Example 1: A method for preparing iridium-coated gallium micro / nanospheres by chemical reduction, the specific steps of which are as follows: (1) Weigh 0.5 g of liquid gallium metal and add it to 100 mL of ethanol. Disperse it by ultrasonication to obtain a gallium micro-nano particle suspension. After standing, centrifuge and wash and dry it multiple times with deionized water and ethanol.

[0030] (2) Weigh 4.64 mg of polyvinylpyrrolidone and dissolve it in 100 mL of deionized water. Add the dried gallium micro-nano particles to the solution and stir magnetically until homogeneous.

[0031] (3) Weigh 0.088 g of ascorbic acid and dissolve it in 10 mL of deionized water. Add the solution dropwise to the gallium micro-nanosphere suspension at a rate of 1 mL / min and stir until homogeneous.

[0032] (4) Weigh 0.103 g of chloroiridium hexahydrate and dissolve it in 10 mL of deionized water. Add the solution dropwise to the mixture at a rate of 1 mL / min under magnetic stirring at 60 °C. After the addition is complete, continue the reaction at a constant temperature for 4 h.

[0033] (5) After the reaction is complete, cool naturally to room temperature, let stand to allow the product to settle naturally, separate by centrifugation, and wash repeatedly with deionized water and ethanol.

[0034] (6) The cleaned product was dried at 20 °C for 12 h to obtain iridium-coated gallium micro-nanosphere powder.

[0035] The SEM and EDS images of the iridium-coated gallium micro / nanospheres in this embodiment are shown below. Figure 1 ,from Figure 1 As can be seen, through careful preparation, we have successfully obtained iridium-coated gallium micro / nanospheres.

[0036] Example 2: A method for preparing iridium-coated gallium micro / nanospheres by chemical reduction, the specific steps of which are as follows: (1) Weigh 1.0 g of liquid gallium metal and add it to 100 mL of propanol. Disperse the gallium micro-nano particles by ultrasonication to obtain a gallium micro-nano particle suspension. After standing, centrifuge and wash and dry the suspension multiple times with deionized water and ethanol.

[0037] (2) Weigh 8.70 mg of polyvinylpyrrolidone and dissolve it in 100 mL of deionized water. Add the dried gallium micro-nano particles to the solution and stir magnetically until homogeneous.

[0038] (3) Weigh 0.360 g of glucose and dissolve it in 10 mL of deionized water. Add the solution dropwise to the gallium micro-nanosphere suspension at a rate of 4 mL / min and stir until homogeneous.

[0039] (4) Weigh 0.670 g of chloroiridium hexahydrate and dissolve it in 10 mL of deionized water. Add the solution dropwise to the mixture at a rate of 4 mL / min under magnetic stirring at 80 °C. After the addition is complete, continue the reaction at a constant temperature for 2 h.

[0040] (5) After the reaction is complete, cool naturally to room temperature, let stand to allow the product to settle naturally, separate by centrifugation, and wash repeatedly with deionized water and ethanol.

[0041] (6) The cleaned product was dried at 40 °C for 8 h to obtain iridium-coated gallium micro / nanosphere powder.

[0042] The SEM and EDS images of the iridium-coated gallium micro / nanospheres in this embodiment are shown below. Figure 2 ,from Figure 2 As can be seen, through careful preparation, we have successfully obtained iridium-coated gallium micro / nanospheres.

[0043] Example 3: A method for preparing iridium-coated gallium micro / nanospheres by chemical reduction, the specific steps of which are as follows: (1) Weigh 2.0 g of liquid gallium metal and add it to 100 mL of isopropanol. Disperse the gallium micro-nano particles by ultrasonication to obtain a gallium micro-nano particle suspension. After standing, centrifuge and wash and dry the suspension multiple times with deionized water and ethanol.

[0044] (2) Weigh 20.0 mg of polyvinylpyrrolidone and dissolve it in 100 mL of deionized water. Add the dried gallium micro-nano particles to the solution and stir magnetically until homogeneous.

[0045] (3) Weigh 0.440 g of ascorbic acid and 0.375 g of tartaric acid and dissolve them in 10 mL of deionized water. Add them to the above gallium micro-nanosphere suspension and stir until homogeneous.

[0046] (4) Weigh 1.03 g of chloroiridium hexahydrate and dissolve it in 10 mL of deionized water. Under magnetic stirring at 100 °C, add it dropwise to the above mixture at a rate of 10 mL / min. After the addition is complete, continue the reaction at a constant temperature for 1 h.

[0047] (5) After the reaction is complete, cool naturally to room temperature, let stand to allow the product to settle naturally, separate by centrifugation, and wash repeatedly with deionized water and ethanol.

[0048] (6) The cleaned product was dried at 50 °C for 6 h to obtain iridium-coated gallium micro / nanosphere powder.

[0049] The SEM and EDS images of the iridium-coated gallium micro / nanospheres in this embodiment are shown below. Figure 3 ,from Figure 3 As can be seen, through careful preparation, we have successfully obtained iridium-coated gallium micro / nanospheres.

[0050] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing iridium-coated gallium micro / nanospheres by chemical reduction, characterized in that, The specific steps are as follows: (1) Liquid gallium metal was ultrasonically dispersed in a solvent to obtain a suspension of gallium micro-nano particles. After standing, it was washed and dried multiple times with deionized water and ethanol. (2) Add the dried gallium micro-nanoparticles to the polyvinylpyrrolidone solution, mix and stir evenly to obtain gallium micro-nanoparticles; (3) Weigh a certain amount of reducing agent and dissolve it in deionized water, then add it dropwise to an aqueous solution containing gallium and stir until homogeneous; (4) Weigh a certain amount of chloroiridium acid and dissolve it in deionized water. Add it dropwise to the above solution under stirring and heating conditions. After the addition is completed, continue the reaction at a constant temperature. (5) After the reaction is complete, allow the product to cool naturally to room temperature, remove the product that has settled naturally, centrifuge it, and wash it several times. (6) The cleaned powder is dried at a preset temperature to obtain iridium-coated gallium micro / nanosphere powder.

2. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: The solvent in step (1) is one or more of ethanol, isopropanol and propanol.

3. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: In step (1), the concentration of gallium micro / nanoparticle suspension is 5~20 g / L.

4. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: In step (2), the concentration of the polyvinylpyrrolidone solution is 0.862–3.45 μmol / L.

5. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: In step (3), the reducing agent is one or more of ascorbic acid, glucose, and tartaric acid.

6. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: The concentration of the reducing agent in step (3) is 0.05~0.5 mol / L.

7. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: The concentration of chloroiridium acid in step (4) is 0.02 to 0.2 mol / L.

8. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: The heating temperature in step (4) is 60~100 ℃, and the constant temperature reaction time is 1~4 h.

9. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: The dropping rate in step (4) is 1~10 mL / min.

10. The method for preparing iridium-coated gallium micro / nanospheres by chemical reduction according to claim 1, characterized in that: The drying temperature in step (5) is 20~50 ℃ and the drying time is 6~12 h.

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