Method for improving the preparation concentration of iridium nanoparticle solution and application

Abstract

The application belongs to the field of noble metal nanomaterials, and particularly relates to a method for improving the concentration of an iridium nanoparticle solution and application, comprising the following steps: precursor system construction: adding iridium chloride trihydrate into ethanol, then adding acetylacetone and stirring until completely dissolved to form an iridium-acetylacetone coordinated precursor system solution; water removal treatment: adding triethyl orthoformate and stirring until uniform; stable system construction: adding citric acid and stirring until uniform; reduction reaction: adding sodium hydroxide ethanol solution, constant temperature stirring reaction, and obtaining an iridium nanoparticle solution. Compared with the prior art, the application solves the problems of poor handling of the precursor in the alcohol phase system, easy generation of byproduct precipitates, and insufficient particle dispersion stability in the prior art. The preparation method of the application realizes the improvement of the concentration, stability and controllability of the preparation process of the iridium nanoparticle solution.

Description

Technical Field

[0001] This invention pertains to the preparation of noble metal nanomaterials, specifically relating to a method and application for increasing the concentration of iridium nanoparticle solutions. Background Technology

[0002] Iridium nanoparticles have important application value in the fields of electrocatalysis and energy conversion due to their excellent catalytic performance, chemical stability and electrochemical activity. Existing public documents, such as Monitoring the structural changes iniridium nanoparticles during oxygen evolution electrocatalysis with operandoX-ray total scattering (Journal of the American Chemical Society, 2024, 146(40): 27517-27527), Influence of temperature on the performance of carbon-andATO-supported oxygen evolution reaction catalysts in a gas diffusion electrode setup (ACS catalysis, 2023, 13(11): 7568-7577), Surfactant-free Irnanoparticles synthesized in ethanol: Catalysts for the oxygen evolutionreaction (Materials Letters, 2022, 308: 131209), Colloids for catalysts: concept for the preparation of superior catalysts of industrial relevance (Angewandte Chemie, 2018, 130(38): In patents 12518-12521 and 2017 / 0194654 A1, as well as in schemes disclosed in CN109226740A and CN118180392A, there are already technical routes for preparing iridium nanoparticles by using iridium chloride or hydrated iridium chloride as a precursor, ethanol as a reaction medium, and heating under alkaline conditions. Related patent US 2017 / 0194654 A1 also shows that ethanol can act as both a solvent and a reducing medium, and the addition of alkaline solution will affect the reduction process and particle formation of the system.

[0003] However, during the process of reproducing the relevant publicly available schemes, the applicant discovered that when anhydrous iridium chloride was used as a precursor, its solubility in ethanol was poor, which was not conducive to constructing a high-concentration and homogeneous precursor system. Public information such as Direct self-condensation of bio-alcohols in the aqueous phase (Green Chemistry, 2014, 16(8): 3971-3977) also indicates that anhydrous iridium chloride has low solubility or poor treatability in ethanol; in contrast, iridium chloride trihydrate is generally more likely to form a treatable precursor system in water or alcohol media, and is therefore more suitable as an iridium source in the ethanol phase reaction. However, although using iridium chloride trihydrate is beneficial to improving the treatability of the precursor in the ethanol system, the introduced water of crystallization will further increase the water content in the system. Under alkaline conditions, iridium salts are known to be prone to hydrolysis, and further form hydroxylated or oxyhydroxylated iridium species. Therefore, in the ethanol-base reaction system, residual moisture may induce the hydrolysis of iridium species and the precipitation of byproducts, thereby affecting the concentration and stability of the target iridium nanoparticle solution. The applicant also observed precipitation formation when reproducing the relevant scheme.

[0004] Furthermore, the dispersion stability and particle size consistency of particles obtained in the traditional iridium chloride-ethanol phase alkali addition system are quite sensitive to specific process windows. The published literature, *Surfactant-free Ir nanoparticles synthesized in ethanol: Catalysts for the oxygen evolution reaction* (Materials Letters, 2022, 308: 131209), indicates that under optimized conditions, stable colloidal iridium nanoparticles of approximately 2 nm can be obtained, even achieving high dispersion. However, it also points out that under high loading or unfavorable dispersion conditions, particle aggregation affects the final catalyst performance. This suggests that the traditional system is not necessarily unstable, but without specific treatment, it is more prone to particle aggregation under higher concentrations or higher loading conditions, thus affecting dispersion stability and particle size distribution consistency.

[0005] Furthermore, in existing technologies, sodium hydroxide is typically added in a fixed amount, solely for adjusting the alkaline reaction environment and promoting the conversion of metal precursors to nanoparticles in the ethanol system. Related patent US 2017 / 0194654 A1 explicitly states that alkaline solutions can neutralize protons generated during ethanol oxidation, thereby enhancing the reducing power of ethanol; and mechanistic studies on the formation process of iridium nanoparticles indicate that the type of alkali and its cations significantly affects the precursor conversion pathway and the final particle size. However, existing disclosures typically only provide the total amount of sodium hydroxide added, failing to distinguish between the portion used to neutralize the acidic components of the system and the portion used to regulate the reduction / nucleation process. This hinders more precise process control of the reaction window and the preparation of stable products.

[0006] Therefore, how to obtain a solution of iridium nanoparticles with high concentration and good dispersibility remains a problem to be solved in the existing technology. Summary of the Invention

[0007] The purpose of this invention is to provide a method and application for improving the concentration of iridium nanoparticle solutions to solve at least one of the aforementioned problems, thereby addressing issues such as poor precursor handling in alcohol-phase systems, easy formation of by-product precipitates, and insufficient particle dispersion stability in existing technologies. The preparation method of this invention improves the concentration, stability, and controllability of the iridium nanoparticle solution preparation process.

[0008] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a method for increasing the concentration of iridium nanoparticle solutions, comprising the following steps: S1. Construction of precursor system: Iridium chloride trihydrate was added to ethanol, then acetylacetone was added and stirred until completely dissolved to form an iridium-acetylacetone coordinated precursor system solution. S2. Dehydration treatment: Add triethyl orthoformate to the precursor system solution obtained in step S1 and stir evenly to obtain the first intermediate system solution; S3. Construction of stable system: Add citric acid to the first intermediate system solution obtained in step S2 and stir to mix evenly to obtain the second intermediate system solution; S4. Reduction reaction: Add sodium hydroxide ethanol solution to the second intermediate system solution obtained in step S3, and stir the reaction at a constant temperature to obtain iridium nanoparticle solution.

[0009] Preferably, in step S1: The molar ratio of iridium chloride trihydrate to acetylacetone is 1:(2~5), which is used to improve the state of iridium chloride trihydrate in the ethanol system.

[0010] Preferably, in step S1: The molar ratio of iridium chloride trihydrate to acetylacetone is 1:(3~4), which is used to improve the state of iridium chloride trihydrate in the ethanol system.

[0011] Preferably, in step S2: The amount of triethyl orthoformate added is 5-15% of the mass of the precursor system solution, which is used to reduce the water content in the system and reduce the hydrolysis of iridium species and the formation of by-product precipitation.

[0012] Preferably, in step S3: The molar ratio of citric acid to iridium chloride trihydrate in step S1 is 1:(1~10), which is used to improve the dispersion stability of the obtained iridium nanoparticles in solution and reduce particle agglomeration.

[0013] Preferably, in step S3: The molar ratio of citric acid to iridium chloride trihydrate in step S1 is 1:(3~5), which is used to improve the dispersion stability of the obtained iridium nanoparticles in solution and reduce particle agglomeration.

[0014] Preferably, in step S4: The molar ratio of sodium hydroxide used to regulate the reaction process in the sodium hydroxide ethanol solution to iridium chloride trihydrate in step S1 is 1:(5~20). The amount of sodium hydroxide used to neutralize citric acid and for the reaction with acetylacetone is determined according to the stoichiometric ratio of the amounts of citric acid and acetylacetone.

[0015] This scheme specifically considers the impact of the addition of citric acid and acetylacetone on sodium hydroxide consumption (if the amount of citric acid is increased but the amount of sodium hydroxide is not changed according to the existing technology, the amount of sodium hydroxide used to react with iridium chloride trihydrate will be consumed and severely insufficient). Therefore, this scheme specifically limits the amount of sodium hydroxide used to control the reaction process. It should be noted that although this scheme calculates sodium hydroxide in two parts, in actual operation and addition, the total calculated amount of sodium hydroxide is still added as a whole (adding it in batches will lead to the formation of a large amount of sodium citrate insoluble in ethanol, the formation of iridium hydroxide precipitate which is not conducive to the reaction, and other adverse consequences). During the coordination process of acetylacetone and iridium ions, free hydrogen ions are generated: 3 acetylacetones can form a complete 6-coordinate structure with one iridium ion, and at the same time generate 3 free hydrogen ions; therefore, an equal amount of sodium hydroxide must also be prepared for the reaction to avoid affecting the normal preparation.

[0016] In particular, the order of adding sodium hydroxide is also a factor affecting the reaction result. It should be added after citric acid and acetylacetone are added to the system. Furthermore, during the addition of sodium hydroxide, it should be added slowly while stirring simultaneously to avoid precipitation occurring midway (the stirring speed is not particularly limited, as long as precipitation is avoided). The main reason for adding sodium hydroxide after citric acid and acetylacetone is to prevent the iridium precursor, water, and sodium hydroxide from appearing simultaneously in the same system. Therefore, by first adding sufficient triethyl orthoformate to remove any water that may be present in the system and creating a highly hygroscopic environment, citric acid and acetylacetone are added (the order of these two is not important), and finally sodium hydroxide is added. This ensures that the water produced by the reaction of sodium hydroxide with acetylacetone and citric acid can be immediately absorbed by triethyl orthoformate. If sodium hydroxide is added prematurely without triethyl orthoformate, it is highly likely that iridium ions will react with hydroxide ions to form insoluble iridium hydroxide precipitate. These precipitates are inert in subsequent reactions, meaning that this portion of iridium is completely wasted, which will greatly reduce the final yield.

[0017] Preferably, in step S4: The molar ratio of sodium hydroxide used to regulate the reaction process in the sodium hydroxide ethanol solution to iridium chloride trihydrate in step S1 is 1:(10~15).

[0018] Preferably, the steps include: S1. Construction of precursor system: Iridium chloride trihydrate was added to ethanol, then acetylacetone was added and stirred until completely dissolved to form an iridium-acetylacetone coordinated precursor system solution; wherein, the molar ratio of iridium chloride trihydrate to acetylacetone was 1:4. S2. Dehydration treatment: Add triethyl orthoformate to the precursor system solution obtained in step S1 and stir evenly to obtain the first intermediate system solution; S3. Construction of a stable system: Add citric acid to the first intermediate system solution obtained in step S2 and stir to mix evenly to obtain the second intermediate system solution; wherein, the molar ratio of iridium chloride trihydrate to citric acid is 1:3; S4. Reduction reaction: Add sodium hydroxide ethanol solution to the second intermediate system solution obtained in step S3, and stir the reaction at a constant temperature of 60~80℃ for 2~4h to obtain iridium nanoparticle solution; wherein, the molar ratio of iridium chloride trihydrate to sodium hydroxide in sodium hydroxide ethanol solution is 1:10.

[0019] Preferably, in step S4: The temperature of the constant-temperature stirring reaction is 70°C, and the reaction time is 3 hours.

[0020] The second aspect of this invention discloses the application of a method for increasing the concentration of iridium nanoparticle solution in the fields of electrocatalysis and energy conversion. Iridium nanoparticles are prepared by the method described in any of the preceding claims, and the iridium nanoparticles are used in the fields of electrocatalysis and energy conversion.

[0021] Preferably, the iridium nanoparticles have a particle size of 2~3.5 nm.

[0022] The working principle of this invention is as follows: The formation of a coordination structure between acetylacetone and iridium chloride trihydrate helps improve the treatment state of the iridium source in the ethanol system and facilitates subsequent reactions.

[0023] The strong hygroscopic properties of triethyl orthoformate are used to remove trace amounts of water from the system, thereby reducing the adverse effects of water on subsequent reactions and minimizing the hydrolysis of iridium species and the formation of byproduct precipitates.

[0024] Citric acid, as a stabilizer, can be adsorbed onto the surface of iridium nanoparticles, which helps to improve the dispersion stability of the obtained iridium nanoparticles in solution and reduce particle aggregation.

[0025] The amount of sodium hydroxide added includes the portion needed for neutralization with citric acid and the portion needed to regulate the reaction process. The amount of sodium hydroxide used to neutralize citric acid is determined according to the stoichiometric ratio based on the actual amount of citric acid added.

[0026] It should be noted that the addition and combination of various materials in this scheme are the key factors in achieving the desired effect. Removing or replacing any of the materials will result in the inability to prepare the product.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. Using iridium chloride trihydrate as the iridium source and coordinating it with acetylacetone helps to improve the treatment state of the iridium source in the ethanol system, thus making it more conducive to constructing a higher concentration and more uniform precursor system.

[0028] 2. By introducing triethyl orthoformate for dehydration treatment, the adverse effects of residual moisture in the system on the alkaline reaction process can be reduced, and the hydrolysis of iridium species and the precipitation of by-products can be decreased.

[0029] 3. By introducing citric acid to construct a stable system, the dispersion stability of the obtained iridium nanoparticles can be improved and the tendency of particle aggregation can be reduced. In this invention, after the obtained iridium nanoparticle solution was placed at room temperature for 30 days, no obvious layering or visible precipitation was observed by the naked eye, indicating that it has good dispersion stability.

[0030] 4. By functionally classifying the amount of sodium hydroxide added and synergistically controlling the ratio of acetylacetone and citric acid (neutralization reaction of citric acid with sodium hydroxide, and neutralization reaction of hydrogen ions generated by acetylacetone during coordination with sodium hydroxide), the controllability of the reaction process can be improved. In this invention, the obtained iridium nanoparticles have a particle size in the range of 2~3nm and exhibit good dispersion.

[0031] 5. The method of the present invention has a relatively simple process flow, mild reaction conditions, and does not require complex equipment, thus having good ease of implementation.

[0032] The applicant conducted UV-Vis absorption spectroscopy tests on the iridium nanoparticle solution obtained by the iridium chloride alcohol phase addition alkali system in patent US 2017 / 0194654 A1 (i.e., iridium salt reduction method) under the same conditions. The results showed that the absorption intensity of the present invention was significantly higher than that of the comparative scheme in patent US 2017 / 0194654 A1; with the absorption intensity at 600 nm as a reference, the preferred scheme of the present invention was approximately 7 times that of the comparative scheme, indicating that the method of the present invention is advantageous for obtaining a higher concentration of iridium nanoparticle solution. Attached Figure Description

[0033] Figure 1 TEM images of iridium nanoparticles from Examples 1-3 and the control scheme (existing technology: anhydrous iridium chloride alcohol phase addition alkali scheme) are shown, where a is the control scheme, b is Example 1, c is Example 2, and d is Example 3.

[0034] Figure 2 The graph shows a comparison of the concentrations of iridium nanoparticle solutions in Examples 1-3 and the control scheme, measured by a UV spectrophotometer (with absorbance at 600 nm as a reference).

[0035] Figure 3 The diagram shows a comparison of the particle size distribution of iridium nanoparticle solutions in Examples 1-3 and the control scheme. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] Unless otherwise specified in the following description, the reagents used are conventional commercial products, the methods used are well-known in the art, and any other matters not covered herein may be handled using existing technologies.

[0038] The present invention aims to provide a method for preparing a high-concentration stable iridium nanoparticle solution, in order to improve the problems of poor handling of iridium precursors in alcohol phase systems, easy formation of by-product precipitates, insufficient particle dispersion stability, and insufficient process control in existing iridium nanoparticle preparation methods, thereby improving the concentration, stability, and controllability of the obtained iridium nanoparticle solution.

[0039] To achieve the above objectives, this invention provides a method for preparing a high-concentration stable iridium nanoparticle solution. This method improves upon existing technologies by synergistically controlling the iridium precursor system, dehydration process, stabilization system, and alkaline reaction conditions, addressing issues such as the handleability of the precursor in the ethanol system, moisture interference, byproduct formation, and insufficient particle dispersion stability. The specific technical solution is as follows: A method for preparing a high-concentration stable iridium nanoparticle solution includes the following steps: S1. Construction of the precursor system: Using iridium chloride trihydrate as the iridium source, ethanol was added as the solvent, followed by acetylacetone. The mixture was stirred until completely dissolved to form an iridium-acetylacetone coordinated precursor system solution; wherein the molar ratio of iridium to acetylacetone was 1:(2~5). The coordination structure between acetylacetone and iridium chloride trihydrate helps to improve the treatment state of the iridium source in the ethanol system and is beneficial to the subsequent reaction.

[0040] S2. Dehydration treatment: Add triethyl orthoformate to the precursor system obtained in step S1 and stir evenly. Utilize the strong hygroscopic properties of triethyl orthoformate to remove trace amounts of water in the system, thereby reducing the adverse effects of water in the system on subsequent reactions and minimizing the hydrolysis of iridium species and the formation of by-product precipitates. The amount of triethyl orthoformate added is 5-15% of the mass of the precursor system.

[0041] S3. Construction of a stable system: Citric acid is added to the system treated by dehydration in step S2 and stirred to mix; wherein the molar ratio of iridium to citric acid is 1:(1~10). Citric acid, as a stabilizer, can be adsorbed on the surface of iridium nanoparticles, which helps to improve the dispersion stability of the obtained iridium nanoparticles in solution and reduce particle agglomeration.

[0042] S4. Reduction reaction: Add sodium hydroxide ethanol solution to the system obtained in step S3, and stir at a constant temperature of 60~80℃ for 2~4h to convert the iridium precursor into iridium nanoparticles; wherein, the amount of sodium hydroxide added includes the part required for neutralizing citric acid and reacting with acetylacetone, as well as the part required for controlling the reaction process (sodium hydroxide exists as a catalyst). In this scheme, the molar ratio of iridium to sodium hydroxide required for controlling the reaction process is 1:(5~20). The amount of sodium hydroxide used for neutralizing citric acid and reacting with acetylacetone is determined according to the actual amount of citric acid and acetylacetone added according to the stoichiometric ratio.

[0043] S5. Cooling to obtain the product: After the reaction is completed, cool to room temperature to obtain a high-concentration stable iridium nanoparticle solution, which can be directly used in subsequent applications without additional separation and purification.

[0044] Preferably, the molar ratio of iridium to acetylacetone is 1:(3~4).

[0045] Preferably, the molar ratio of iridium to citric acid is 1:(3~5).

[0046] Preferably, the molar ratio of iridium to sodium hydroxide, which controls the reaction process, is 1:(10~15).

[0047] More preferably, the molar ratio of iridium to citric acid is 1:3, the molar ratio of iridium to sodium hydroxide required to regulate the reaction process is 1:10, and the molar ratio of iridium to acetylacetone is 1:4.

[0048] More preferably, the reaction temperature in step S4 is 70°C and the reaction time is 3 hours.

[0049] The iridium nanoparticles prepared by this method have a particle size of 2~3 nm.

[0050] The technical solution of the present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Without departing from the concept of the present invention, those skilled in the art can make conventional adjustments to the relevant process conditions and parameters.

[0051] In this scheme, the purity of iridium chloride trihydrate was 99.9%, and acetylacetone, citric acid, triethyl orthoformate, sodium hydroxide, and ethanol were all analytical grade reagents. TEM testing was performed using a Talos F200X G2 transmission electron microscope with an accelerating voltage of 200kV. UV-Vis spectra were acquired using a PerkinElmer LAMBDA950 spectrometer. The relative concentration was calculated based on the absorbance of the colloid at 600nm, and the result of Example 2 was set as unit 1 (for comparison with the result of Example 2).

[0052] Comparison Plan S1. Construction of precursor system: Anhydrous iridium chloride is used as the iridium source, ethanol is added as the solvent, and the mixture is sonicated for more than 30 minutes to form a precursor system solution. S2. Reduction reaction: Add sodium hydroxide ethanol solution to the system obtained in step S1, and stir the reaction at a constant temperature of 60~80℃ for 2~4h (the results obtained under this range are basically the same) to convert the iridium precursor into iridium nanoparticles; wherein, the molar ratio of iridium to sodium hydroxide is 1:10.

[0053] S3. Cooling to obtain the product: After the reaction is completed, cool to room temperature to obtain a high-concentration stable iridium nanoparticle solution, which can be directly used in subsequent applications without additional separation and purification.

[0054] Example 1 Preparation of iridium nanoparticle solution under low ratio conditions: 1. Construction of precursor system: Weigh 0.0295 g of iridium chloride trihydrate (calculated as iridium, molar amount is 0.0001 mol), add it to 10 mL of ethanol, then add 0.0002 mol of acetylacetone (about 20 μL), stir magnetically for 30 min to form the precursor system.

[0055] 2. Dehydration treatment: Add 0.8 mL of triethyl orthoformate to the precursor solution and stir for 15 min to reduce the adverse effects of water in the system on subsequent reactions.

[0056] 3. Construction of a stable system: Add 0.0001 mol of citric acid (approximately 21 mg) and stir for 20 min.

[0057] 4. Reduction reaction: The amount of sodium hydroxide used to neutralize citric acid is 0.0003 mol (12 mg), and the amount of sodium hydroxide used to regulate the reaction process is 0.0005 mol (20 mg). A total of 32 mg of sodium hydroxide is weighed out and 2 mL of ethanol is added to prepare a sodium hydroxide ethanol mixture. This mixture is then slowly added dropwise to the above system. The temperature is then raised to 70 °C and stirred at a constant temperature for 3 h.

[0058] 5. Product Characterization: After the reaction was completed and cooled to room temperature, an iridium nanoparticle solution was obtained. TEM characterization of the obtained iridium nanoparticle solution showed that the particle size of the obtained iridium nanoparticles was approximately 3 nm. Figure 1 b, Figure 3 As shown, the nanoparticles prepared in this example are clearly observed to be uniformly dispersed, exhibiting good dispersion. After the obtained solution was left to stand at room temperature for 30 days, no obvious stratification or visible precipitation was observed by the naked eye.

[0059] Compared to the sample obtained by adding an alkali to the iridium chloride alcohol phase in patent US 2017 / 0194654 A1, the iridium nanoparticle solution obtained in this example exhibits a higher UV-Vis absorption intensity under the same test conditions, such as... Figure 2 As shown; with the absorption intensity at 600 nm as a reference, this example is approximately 2.27 times that of the comparative scheme.

[0060] Example 2 Preparation of iridium nanoparticle solution under preferred formulation conditions: 1. Construction of precursor system: Weigh 0.0295 g of iridium chloride trihydrate (containing 0.0001 mol of iridium), add 10 mL of ethanol, then add 0.0004 mol of acetylacetone (about 40 μL), and stir magnetically for 30 min to form the precursor system.

[0061] 2. Dehydration treatment: Add 0.9 mL of triethyl orthoformate to the above precursor system and stir for 15 min to reduce the adverse effects of water in the system on subsequent reactions.

[0062] 3. Construction of a stable system: Add 0.0003 mol citric acid (approximately 63 mg) and stir for 20 min.

[0063] 4. Reduction reaction: The amount of sodium hydroxide used to neutralize citric acid is 0.0009 mol (36 mg), and the amount of sodium hydroxide used to regulate the reaction process is 0.0010 mol (40 mg). A total of 76 mg of sodium hydroxide is weighed out and 2 mL of ethanol is added to prepare a sodium hydroxide ethanol mixture. This mixture is then slowly added dropwise to the above system. The temperature is then raised to 70 °C and stirred at a constant temperature for 3 h.

[0064] 5. Product Characterization: After the reaction was completed and cooled to room temperature, an iridium nanoparticle solution was obtained. TEM characterization of the obtained iridium nanoparticle solution showed that the particle size of the obtained iridium nanoparticles was approximately 2.6 nm. Figure 1 c, Figure 3 As shown, the nanoparticles prepared in this example are clearly observed to be uniformly dispersed, exhibiting good dispersion. After the obtained solution was left to stand at room temperature for 30 days, no obvious stratification or visible precipitation was observed by the naked eye.

[0065] Compared to the sample obtained by adding an alkali to the iridium chloride alcohol phase in patent US 2017 / 0194654 A1, the iridium nanoparticle solution obtained in this example exhibits a higher UV-Vis absorption intensity under the same test conditions, such as... Figure 2 As shown; with the absorption intensity at 600 nm as a reference, this example is approximately 6.7 times that of the comparative scheme.

[0066] Example 3 1. Construction of precursor system: Weigh 0.0295 g of iridium chloride trihydrate (calculated as iridium, molar amount is 0.0001 mol), add 10 mL of ethanol, then add 0.0005 mol of acetylacetone (about 50 μL), stir magnetically for 30 min to form precursor system.

[0067] 2. Dehydration treatment: Add 1.0 mL of triethyl orthoformate to the precursor solution and stir for 15 min to reduce the adverse effects of water in the system on subsequent reactions.

[0068] 3. Construction of a stable system: Add 0.0010 mol citric acid (approximately 210 mg) and stir for 20 min.

[0069] 4. Reduction reaction: The amount of sodium hydroxide used to neutralize citric acid is 0.0030 mol (120 mg), and the amount of sodium hydroxide used to regulate the reaction process is 0.0020 mol (80 mg). A total of 200 mg of sodium hydroxide is weighed out and 2 mL of ethanol is added to prepare a sodium hydroxide ethanol mixture. This mixture is then slowly added dropwise to the above system, and the temperature is raised to 70 °C and stirred at a constant temperature for 3 h.

[0070] 5. Product Characterization: After the reaction was completed and cooled to room temperature, an iridium nanoparticle solution was obtained. TEM characterization of the obtained iridium nanoparticle solution showed that the particle size of the obtained iridium nanoparticles was approximately 2.8 nm. Figure 1 d, Figure 3 As shown, the nanoparticles prepared in this example are clearly observed to be uniformly dispersed, exhibiting good dispersion. After the obtained solution was left to stand at room temperature for 30 days, no obvious stratification or visible precipitation was observed by the naked eye.

[0071] Compared to the sample obtained by adding an alkali to the iridium chloride alcohol phase in patent US 2017 / 0194654 A1, the iridium nanoparticle solution obtained in this example exhibits a higher UV-Vis absorption intensity under the same test conditions, such as... Figure 2 As shown; with the absorption intensity at 600nm as a reference, this example is approximately 5.5 times that of the comparative scheme.

[0072] Example 4 This example is similar to Example 1, the main difference being that the amount of acetylacetone added is 0.0003 mol.

[0073] The test results showed that its performance was basically the same as that of Example 1, so no further explanation or demonstration is given here.

[0074] It should be noted that tests have shown that further increasing the amount of acetylacetone does not affect the product performance and results. However, considering the cost and initial dissolution, it is recommended to limit the molar ratio of iridium chloride trihydrate to acetylacetone to 1:(3~4).

[0075] Example 5 This example is similar to Example 1, the main difference being that the amount of citric acid added is 0.0005 mol.

[0076] The test results showed that its performance was basically the same as that of Example 1, so no further explanation or demonstration is given here.

[0077] Example 6 This example is similar to Example 3, with the main difference being that the amount of sodium hydroxide added to control the reaction process is 0.0015 mol.

[0078] The test results showed that its performance was basically the same as that of Example 3, so no further explanation or demonstration is given here.

[0079] It should be noted that tests have shown that further increasing the amount of sodium hydroxide will not affect the product performance and results. However, considering the cost, it is recommended to limit the molar ratio of sodium hydroxide used to control the reaction process in the iridium chloride trihydrate to sodium hydroxide ethanol solution to 1:(5~20).

[0080] Example 7 This example is similar to Example 2, with the main difference being that the temperature at which the reduction reaction occurs in step 4 is 60℃ (i.e., the temperature is raised to 60℃) and the time is 4 hours (i.e., constant temperature stirring for 4 hours).

[0081] The test results showed that its performance was basically the same as that of Example 2, so no further explanation or demonstration is given here.

[0082] Example 8 This example is similar to Example 2, with the main difference being that the temperature at which the reduction reaction occurs in step 4 is 80℃ (i.e., the temperature is raised to 80℃) and the time is 2 hours (i.e., constant temperature stirring for 2 hours).

[0083] The test results showed that its performance was basically the same as that of Example 2, so no further explanation or demonstration is given here.

[0084] Comparative Example 1 This comparative example is similar to Example 2, the main difference being that triethyl orthoformate was not added. The result was the formation of a large amount of precipitate, with no nanoparticles generated.

[0085] Comparative Example 2 This comparative example is similar to Example 2, the main difference being that acetylacetone was not added. The results showed low iridium utilization, with most of the iridium being wasted as precipitate.

[0086] Comparative Example 3 This comparative example is similar to Example 2, the main difference being that citric acid was not added. The result was that the product lacked stability, exhibiting significant aggregation after only one week.

[0087] In summary, the present invention, through the synergistic introduction of coordination, dehydration, and stabilization control methods, achieves the goal of reducing the adverse effects of moisture in the system on the alkaline ethanol reaction process while retaining the good treatability of iridium chloride trihydrate, and can obtain a high concentration and well-dispersed iridium nanoparticle solution without the tendency for particle aggregation.

[0088] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for increasing the concentration of iridium nanoparticle solution, characterized in that, Includes the following steps: S1. Construction of precursor system: Iridium chloride trihydrate was added to ethanol, then acetylacetone was added and stirred until completely dissolved to form an iridium-acetylacetone coordinated precursor system solution. S2. Dehydration treatment: Add triethyl orthoformate to the precursor system solution obtained in step S1 and stir evenly to remove water and obtain the first intermediate system solution. S3. Construction of stable system: Add citric acid to the first intermediate system solution obtained in step S2 and stir to mix evenly to obtain the second intermediate system solution; S4. Reduction reaction: Add sodium hydroxide ethanol solution to the second intermediate system solution obtained in step S3, and stir the reaction at a constant temperature to obtain iridium nanoparticle solution.

2. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, In step S1: The molar ratio of iridium chloride trihydrate to acetylacetone is 1:(2~5).

3. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, In step S1: The molar ratio of iridium chloride trihydrate to acetylacetone is 1:(3~4).

4. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, In step S2: The amount of triethyl orthoformate added is 5-15% of the mass of the precursor system solution.

5. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, In step S3: The molar ratio of citric acid to iridium chloride trihydrate in step S1 is 1:(1~10).

6. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, In step S3: The molar ratio of citric acid to iridium chloride trihydrate in step S1 is 1:(3~5).

7. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, In step S4: The molar ratio of sodium hydroxide used to regulate the reaction process in the sodium hydroxide ethanol solution to iridium chloride trihydrate in step S1 is 1:(5~20).

8. The method for increasing the concentration of iridium nanoparticle solution according to claim 7, characterized in that, In step S4: The molar ratio of sodium hydroxide used to regulate the reaction process in the sodium hydroxide ethanol solution to iridium chloride trihydrate in step S1 is 1:(10~15).

9. The method for increasing the concentration of iridium nanoparticle solution according to claim 1, characterized in that, Includes the following steps: S1. Construction of precursor system: Iridium chloride trihydrate was added to ethanol, then acetylacetone was added and stirred until completely dissolved to form an iridium-acetylacetone coordinated precursor system solution; wherein, the molar ratio of iridium chloride trihydrate to acetylacetone was 1:

4. S2. Dehydration treatment: Add triethyl orthoformate to the precursor system solution obtained in step S1 and stir evenly to obtain the first intermediate system solution; S3. Construction of a stable system: Add citric acid to the first intermediate system solution obtained in step S2 and stir to mix evenly to obtain the second intermediate system solution; wherein, the molar ratio of iridium chloride trihydrate to citric acid is 1:3; S4. Reduction reaction: Add sodium hydroxide ethanol solution to the second intermediate system solution obtained in step S3, and stir the reaction at a constant temperature of 60~80℃ for 2~4h to obtain iridium nanoparticle solution; wherein, the molar ratio of iridium chloride trihydrate to sodium hydroxide in sodium hydroxide ethanol solution is 1:

10.

10. The application of a method for increasing the concentration of iridium nanoparticle solution in the fields of electrocatalysis and energy conversion, characterized in that... Iridium nanoparticles are prepared by the method described in any one of claims 1 to 9, and the iridium nanoparticles are used in the fields of electrocatalysis and energy conversion.

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