Nanometer iridium oxide, and preparation method and application thereof

Abstract

The application discloses nano iridium oxide and a preparation method and application thereof, and relates to the technical field of nano materials, in particular to a preparation method of nano iridium oxide, which comprises the following steps: S1: dissolving iridium salt in water, adding an alkaline substance to adjust the pH value of the solution to 11-12 to obtain an iridium salt solution; S2: adding a reverse micelle surfactant to obtain a reverse micelle solution A; S3: adding the reverse micelle surfactant to the weak alkali solution to obtain a reverse micelle solution B; S4: mixing the reverse micelle solutions A and B, and then dispersing under the conditions of ultrasonic and monochromatic light irradiation to obtain an iridium oxide colloidal solution; S5: adding an acidic substance to adjust the pH value of the solution to 7-8; and S6: centrifuging and filtering the mixed solution obtained in the step S5, and then sequentially performing ultrasonic washing, vacuum drying and calcination on the obtained precipitate to obtain nano iridium oxide. The preparation method is simple, the obtained nano iridium oxide has high purity, small particle size, good catalytic activity and high application value.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology. Specifically, this invention relates to a nano-iridium oxide, its preparation method, and its application. Background Technology

[0002] With the increasing demand for low-carbon emission reduction, green hydrogen production technologies have received widespread attention. Electrolysis of water using renewable energy is currently the hydrogen production process with the lowest carbon emissions among various hydrogen production technologies. Among the many water electrolysis hydrogen production processes, proton exchange membrane (PEM) electrolysis is the most commonly used process due to its flexible equipment operation, tight contact between components, low resistance, and ability to produce hydrogen at high current densities. Furthermore, the short response time of the PEM electrolyzer allows it to tolerate power fluctuations and perfectly couple with renewable energy sources.

[0003] The PEM water electrolyzer uses PEM to conduct protons and isolates the gas on both sides of the electrodes, avoiding the drawbacks associated with the use of strongly alkaline liquid electrolytes in alkaline water electrolysis (AWE). The PEM water electrolyzer uses PEM as the electrolyte and pure water as the reactant. Furthermore, the low hydrogen permeability of PEM results in high-purity hydrogen, requiring only the removal of water vapor. The electrolyzer employs a zero-gap structure, resulting in low ohmic resistance, significantly improving the overall efficiency of the electrolysis process, and is also more compact. It has a wide pressure control range, with hydrogen output pressure reaching several megapascals, adapting to rapidly changing renewable energy power inputs. The catalyst is the core component of the electrolyzer, affecting the efficiency of the catalytic reaction.

[0004] Studies have shown that iridium oxide is one of the most widely used oxygen evolution catalysts in commercial applications. This is mainly due to the strong corrosion resistance and stability of iridium oxide, which has shown good catalytic performance in the electrocatalytic water splitting reaction.

[0005] Currently, the main methods for preparing iridium oxide on the market include chemical precipitation and the Adams fusion method. One method of chemical precipitation involves reacting the iridium precursor with an alkali (such as sodium hydroxide) to generate iridium hydroxide, which is then dehydrated at high temperature to produce iridium oxide. Another commonly used method is to first reduce the iridium precursor to elemental iridium, and then heat it to above 1000℃ under oxidizing conditions to produce iridium oxide. The Adams fusion method involves reacting the iridium precursor with excess sodium / potassium nitrate to generate iridium salt, which is then dried and oxidized at high temperature to obtain iridium oxide. However, the iridium oxide obtained by these methods has a relatively large particle size, and the prepared iridium oxide mostly contains elemental iridium impurities, resulting in low purity that cannot meet practical production needs. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a nano-iridium oxide, its preparation method, and its applications.

[0007] In a first aspect, embodiments of the present invention provide a method for preparing nano-iridium oxide, comprising the following steps:

[0008] S1: Dissolve iridium salt in water, add an alkaline substance to adjust the pH of the solution to 11-12, and obtain an iridium salt solution;

[0009] S2: Add a reverse micelle surfactant to the iridium salt solution to obtain reverse micelle solution A;

[0010] S3: Add a reverse micelle surfactant to a weak alkaline solution to obtain reverse micelle solution B;

[0011] S4: After mixing the reverse micelle solution A and the reverse micelle solution B, the mixture is dispersed under ultrasonic and monochromatic light irradiation to obtain an iridium oxide colloidal solution.

[0012] S5: Add an acidic substance to the iridium oxide colloidal solution to adjust the pH value of the solution to 7-8;

[0013] S6: After centrifuging and filtering the mixture obtained in step S5, the precipitate is subjected to ultrasonic washing, vacuum drying and calcination in sequence to obtain the nano-iridium oxide.

[0014] This invention utilizes a reverse micelle surfactant as an auxiliary reagent to prepare an iridium oxide colloidal solution, which, after drying and calcination, yields high-purity iridium oxide nanoparticles. The formation of the colloidal system prevents the iridium oxide particles from agglomerating due to adsorption forces, thus inhibiting their further growth. This results in iridium oxide nanoparticles with small particle size and uniform particle size distribution, improving the quality of the iridium oxide product. Furthermore, this method is simple, easy to operate, and has low manufacturing costs, making it highly valuable for application.

[0015] In some embodiments, in step S1, the iridium salt includes at least one of IrCl3, K2IrCl6, and Ir(O2CCH3)3; the concentration of the iridium salt solution is 1–5 mg / mL.

[0016] And / or, the alkaline substance includes at least one of NaOH, KOH, urea, Na3PO4, ammonia, and Na2CO3.

[0017] In some embodiments, in step S2, the mass ratio of the iridium salt in the iridium salt solution to the reverse micelle surfactant is (2-6):1.

[0018] In some embodiments, in step S3, the weak alkaline solution includes at least one of ammonia solution, urea solution, sodium hydroxide solution, potassium hydroxide solution, sodium phosphate solution, and sodium carbonate solution, and the mass concentration of the weak alkaline solution is 8-20 wt%.

[0019] And / or, in the reverse micelle solution B, the amount of the reverse micelle surfactant added is 10-100 mg / mL.

[0020] In some embodiments, in steps S2 and / or S3, the reverse micelle surfactant includes at least one of cetyltrimethylammonium bromide, 1,4-sorbitol, isosorbide, sodium di(2-ethylhexyl)succinate sulfonate, cocamidopropyl betaine, lauryl ether sulfate, and sodium oleate.

[0021] In some embodiments, in step S4, the mass ratio of the reverse micelle solution A to the reverse micelle solution B is (1-10):(1-10);

[0022] And / or, the ultrasound and the monochromatic light irradiation are performed simultaneously; the temperature of both the ultrasound and the monochromatic light irradiation is room temperature, and the time is 2 to 5 hours;

[0023] And / or, during the ultrasound, the frequency of the ultrasound is 20 to 25 kHz;

[0024] And / or, the wavelength of the monochromatic light is 360–950 nm, and the illuminance is 200–2000 W / m². 2 .

[0025] In some embodiments, in step S5, the acidic substance includes at least one of sulfuric acid, phosphoric acid, hydrochloric acid, boric acid, citric acid, adipic acid, and formic acid.

[0026] In some embodiments, in step S6, the ultrasonic cleaning is performed by sequentially washing with methanol and water;

[0027] And / or, the vacuum drying temperature is 50–130°C, and the drying time is 4–24 hours;

[0028] And / or, the calcination temperature is 400–800°C, and the calcination time is 2–3 hours.

[0029] Secondly, embodiments of the present invention also provide a nano-iridium oxide, which is prepared by the above method, and the particle size of the nano-iridium oxide is 35-110 nm.

[0030] The iridium oxide in the embodiments of the present invention has high purity, good dispersibility, and small particle size.

[0031] Thirdly, the embodiments of the present invention also provide the application of the above-mentioned nano-iridium oxide as an oxygen evolution reaction catalyst in PEM water electrolysis, and the nano-iridium oxide exhibits high catalytic activity.

[0032] The advantages and beneficial effects of this invention are as follows:

[0033] (1) This invention uses a reverse micelle surfactant as an auxiliary reagent to prepare an iridium oxide colloidal solution, and then obtains nano-iridium oxide after drying and calcination. This can avoid the iridium oxide particles from growing further due to agglomeration, thereby obtaining iridium oxide nanoparticles with small particle size and uniform particle size distribution. Moreover, this method is simple, easy to operate, and has low cost. The obtained nano-iridium oxide has high purity and good catalytic activity, and has high application value.

[0034] (2) The present invention uses a high-energy monochromatic light source with good light wave monochromaticity, high energy density, wide energy adjustable range, stable output and low energy consumption. Attached Figure Description

[0035] Figure 1 This is the standard XRD pattern of iridium oxide.

[0036] Figure 2 The XRD patterns of iridium oxide obtained in Examples 1, 2, and 3 of this invention are shown.

[0037] Figure 3 This is a TEM spectrum of iridium oxide prepared in Example 1 of the present invention.

[0038] Figure 4 This is the TEM spectrum of iridium oxide obtained in Example 2 of the present invention.

[0039] Figure 5 The image shows the TEM spectrum of iridium oxide prepared in Comparative Example 1.

[0040] Figure 6 The image shows the TEM spectrum of iridium oxide prepared in Comparative Example 2.

[0041] Figure 7 The graphs show the electrocatalytic oxygen evolution performance test results of iridium oxide prepared in Examples 1-3 and Comparative Examples 1 and 2 of this invention.

[0042] Figure 8 This is a schematic diagram of the ultrasonic monochromatic photocatalytic reactor according to an embodiment of the present invention;

[0043] Among them: 1-monochromatic light source; 2-ultrasonic generator; 3-lens; 4-reaction vessel; 5-stirrer; 6-thermometer; 7-exhaust valve. Detailed Implementation

[0044] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0045] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0046] In this article, the words “contain” and “include” and their various variations mean that other elements or wholes may be included but not specifically described.

[0047] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0048] In a first aspect, embodiments of the present invention provide a method for preparing nano-iridium oxide, comprising the following steps:

[0049] S1: Dissolve iridium salt in water, add an alkaline substance to adjust the pH of the solution to 11-12, and obtain an iridium salt solution;

[0050] S2: Add a reverse micelle surfactant to an iridium salt solution to obtain a reverse micelle solution A;

[0051] S3: Add a reverse micelle surfactant to a weak alkaline solution to obtain reverse micelle solution B;

[0052] S4: After mixing reverse micelle solution A and reverse micelle solution B, the mixture is dispersed under ultrasonic and monochromatic light irradiation to obtain iridium oxide colloidal solution;

[0053] S5: Add an acidic substance to the iridium oxide colloidal solution to adjust the pH of the solution to 7-8;

[0054] S6: After centrifuging and filtering the mixture obtained in step S5, the precipitate is subjected to ultrasonic washing, vacuum drying and calcination in sequence to obtain nano-iridium oxide.

[0055] This invention employs a reverse micelle surfactant as an auxiliary reagent to precipitate metal salts within the reverse micelle micro-water core. The growth of the product particles is limited by the structure of the micro-water core itself and the capacity of the internal metal salt. The surfactant molecules adsorbed on the surface can also prevent particle aggregation and further growth, thereby obtaining iridium oxide nanoparticles with small particle size and uniform particle size distribution. Moreover, this method is simple, easy to operate, low in energy consumption, low in cost, and produces nano-iridium oxide with high purity and good catalytic activity, making it suitable for large-scale industrial production applications.

[0056] The preparation of nano-iridium oxide using the reverse micelle method involves the mixing of components between molecules during the reaction, resulting in products with small particle size and high uniformity. Furthermore, the reaction process is easy to control, yielding products that are difficult to obtain using other methods. In addition, the reaction can be carried out at low temperatures, avoiding the appearance of high-temperature impurities and resulting in high product purity.

[0057] In some specific embodiments, in step S1, the iridium salt includes at least one of IrCl3, K2IrCl6, and Ir(O2CCH3)3; and the concentration of the iridium salt solution is 1 to 5 mg / mL, with non-limiting examples such as 1 mg / mL, 2.5 mg / mL, 3 mg / mL, or 5 mg / mL, etc.

[0058] And / or, alkaline substances include at least one of NaOH, KOH, urea, Na3PO4, ammonia, and Na2CO3.

[0059] In some specific embodiments, in step S2, the mass ratio of iridium salt to reverse micelle surfactant in the iridium salt solution is (2-6):1, and non-limiting examples include 2:1, 4:1, 5:1 or 6:1, etc.

[0060] In some embodiments, in step S3, the weak alkaline solution includes at least one of ammonia solution, urea solution, sodium hydroxide solution, potassium hydroxide solution, sodium phosphate solution, and sodium carbonate solution, and the mass concentration of the weak alkaline solution is 8 to 20 wt%, non-limiting examples include 8 wt%, 10 wt%, 15 wt%, or 20 wt%, etc.

[0061] And / or, in the reverse micelle solution B, the amount of reverse micelle surfactant added is 10 to 100 mg / mL, with non-limiting examples such as 10 mg / mL, 25 mg / mL, 50 mg / mL, 80 mg / mL, or 100 mg / mL.

[0062] In some specific embodiments, in steps S2 and / or S3, the reverse micelle surfactant includes at least one of cetyltrimethylammonium bromide, 1,4-sorbitol, isosorbide, sodium di(2-ethylhexyl)succinate sulfonate, cocamidopropyl betaine, lauryl ether sulfate, and sodium oleate.

[0063] In this embodiment of the invention, the above-mentioned reverse micelle surfactant is selected, which can form water-in-oil micelle particles in aqueous solution. This allows the metal salt to precipitate within the micro-water core of the reverse micelle, preventing the iridium oxide particles from growing further due to aggregation. As a result, iridium oxide nanoparticles with small particle size and uniform particle size distribution can be obtained. Moreover, the raw materials of the above-mentioned reverse micelle surfactant are readily available and have low cost. In addition, the reverse micelle solution A and reverse micelle solution B are prepared separately in this application mainly because the iridium salt and the alkaline reverse micelle system need to be fully dispersed before the reaction. If the iridium salt and the alkaline compound are directly mixed, the reaction will occur prematurely, which will greatly affect the degree of dispersion of the system and is not conducive to the control of the particle size of the product.

[0064] In some specific embodiments, in step S4, the mass ratio of reverse micelle solution A to reverse micelle solution B is (1-10):(1-10), and non-limiting examples include: 1:1, 1:2, 2:5, 4:5, 6:7 or 7:10, etc.

[0065] And / or, ultrasound and monochromatic light irradiation are performed simultaneously; the temperature of both ultrasound and monochromatic light irradiation is room temperature, and the time is 2 to 5 hours, with non-limiting examples such as 2 hours, 3 hours, 4 hours, or 5 hours, etc.

[0066] And / or, during ultrasound, the frequency of the ultrasound is 20 to 25 kHz, non-limiting examples such as 20 kHz, 22 kHz or 25 kHz, etc. Ultrasonic treatment plays a promoting role in chemical reactions, which can accelerate the reaction rate, increase the yield and improve the purity of the product.

[0067] And / or, the wavelength of the monochromatic light is 360–950 nm, and non-limiting examples include: 360 nm, 500 nm, 600 nm, 750 nm, 800 nm, or 950 nm, etc.; the illuminance is 200–2000 W / m². 2 Non-limiting examples include: 200W / m 2 500W / m 2 1000W / m 2 1500W / m 2 Or 2000W / m 2 Monochromatic light is used because its optical and electrical parameters are highly consistent, its working state is less affected by changes in external conditions, and it is more energy-efficient than ultraviolet lamps and xenon lamps, which can be achieved using LED lights.

[0068] It should be further noted that in step S4 of the nano-iridium oxide preparation method of this embodiment, the dispersion is carried out in an ultrasonic monochromatic photocatalytic reactor to ensure that the dispersion conditions of both ultrasonic and monochromatic light irradiation are met simultaneously. A schematic diagram of the ultrasonic monochromatic photocatalytic reactor is shown below. Figure 8As shown, it includes: a monochromatic light source 1, an ultrasonic generator 2, a lens 3, a reaction vessel 4, a stirrer 5, a thermometer 6, and an exhaust valve 7.

[0069] Preferably, the monochromatic light source is provided by an LED lamp, that is, a monochromatic LED light source is set above the reaction vessel, and a high-energy lamp bead is installed inside the light source. When ignited, it radiates a strong and stable monochromatic light wave. The color temperature of the visible light of the white lamp bead is close to that of sunlight. It has high energy density and stable output, making it an ideal light source to replace the traditional gas emission type light source for extracting monochromatic light. Moreover, the light head can illuminate horizontally or vertically, the working height of the light source can be freely adjusted, and the projection lens of the light source adopts a large-diameter quartz lens, which can improve the light collection efficiency. In addition, the internal cooling method of the reactor adopts dual-fan circulation cooling.

[0070] Compared with traditional light sources, the monochromatic light source selected in the embodiments of the present invention has the advantages of low overall energy consumption, good monochromaticity of light waves, high energy density of single wavelength light spot, wide energy adjustable range, and long life.

[0071] In some specific embodiments, in step S5, the acidic substance includes at least one of sulfuric acid, phosphoric acid, hydrochloric acid, boric acid, citric acid, adipic acid, and formic acid.

[0072] In some specific embodiments, in step S6, ultrasonic washing involves sequentially washing with methanol and water.

[0073] And / or, the vacuum drying temperature is 50 to 130°C, and non-limiting examples include 50°C, 80°C, 100°C, 110°C, or 130°C; the drying time is 4 to 24 hours, and non-limiting examples include 4 hours, 6 hours, 10 hours, 15 hours, 20 hours, or 24 hours.

[0074] And / or, the roasting temperature is 400 to 800°C, for example, 400°C, 450°C, 500°C, 600°C, 720°C or 800°C; the roasting time is 2 to 3 hours, for example, 2 hours, 2.5 hours or 3 hours.

[0075] Secondly, embodiments of the present invention also provide a nano-iridium oxide, which is prepared by the above method, and the particle size of the nano-iridium oxide is 35-110 nm, such as 35 nm, 50 nm, 65 nm, 80 nm, 100 nm or 110 nm, etc., without limitation.

[0076] Thirdly, the embodiments of the present invention also provide the application of the above-mentioned nano-iridium oxide as an oxygen evolution reaction catalyst in PEM water electrolysis.

[0077] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Unless otherwise stated, all raw materials used in the embodiments and comparative examples are conventional commercially available products, or can be prepared by known methods. The experimental methods in the embodiments and comparative examples that do not specify specific conditions are conventional methods and conditions well known in the art.

[0078] Example 1

[0079] This embodiment provides a method for preparing nano-iridium oxide, including the following steps:

[0080] S1: Accurately weigh 100mg IrCl3 and dissolve it in 40g of water. Add 150mg NaOH to adjust the pH of the solution to 11.5. Stir well to obtain an iridium salt solution.

[0081] S2: Add 20 mg of hexadecyltrimethylammonium bromide (CTAB) to the above iridium salt solution and stir until homogeneous to obtain a transparent reverse micelle solution A;

[0082] S3: Add 20 mg of cetyltrimethylammonium bromide (CTAB) to 50 mL of a 9.5 wt% dilute ammonia solution, stir and mix thoroughly to obtain reverse micelle solution B;

[0083] S4: After mixing reverse micelle solution A and reverse micelle solution B at a mass ratio of 4:5, a suspended colloidal solution system is formed. This system is then placed in an ultrasonic monochromatic photocatalytic (LED lamp) reactor for dispersion (ultrasonic frequency 20kHz; monochromatic light wavelength 500–600nm; light intensity 500W / m²). 2 After dispersion for 2 hours, an iridium oxide colloidal solution was obtained.

[0084] S5: Add dilute sulfuric acid to the iridium oxide colloidal solution to adjust the pH of the solution to 7.5;

[0085] S6: After centrifuging and filtering the mixture obtained in step S5, the precipitate is ultrasonically washed with methanol and water in sequence; then it is vacuum dried at 90℃ for 6h; finally, the dried material is calcined at 600℃ for 2h to obtain nano-iridium oxide (IrO2), the particle size of which is about 40nm.

[0086] Example 2

[0087] This embodiment provides a method for preparing nano-iridium oxide, including the following steps:

[0088] S1: Accurately weigh 150mg K2IrCl6 and dissolve it in 40g of water. Add 100mg KOH to adjust the pH of the solution to 12, stir well, and obtain an iridium salt solution.

[0089] S2: Add 40 mg of sodium di(2-ethylhexyl)succinate sulfonate to the above iridium salt solution and stir until homogeneous to obtain a light gray, semi-transparent reverse micelle solution A;

[0090] S3: Add 40 mg of sodium di(2-ethylhexyl)succinate sulfonate to 80 mL of 10 wt% urea solution, stir and mix evenly to obtain reverse micelle solution B;

[0091] S4: After mixing reverse micelle solution A and reverse micelle solution B at a mass ratio of 1:2, a suspended colloidal solution system is formed. This system is then placed in an ultrasonic monochromatic photocatalytic (LED lamp) reactor for dispersion (ultrasonic frequency 20kHz; monochromatic light wavelength 600–800nm; light intensity 800W / m²). 2 After dispersion for 2 hours, an iridium oxide colloidal solution was obtained.

[0092] S5: Add dilute hydrochloric acid to the iridium oxide colloidal solution to adjust the pH of the solution to 8;

[0093] S6: After centrifuging and filtering the mixture obtained in step S5, the precipitate is ultrasonically washed with methanol and water in sequence; then it is vacuum dried at 100℃ for 8 hours; finally, the dried material is calcined at 400℃ for 3 hours to obtain nano-iridium oxide (IrO2), the particle size of which is about 50nm.

[0094] Example 3

[0095] This embodiment provides a method for preparing nano-iridium oxide, including the following steps:

[0096] S1: Accurately weigh 150 mg Ir(O2CCH3)3 and dissolve it in 40 g of water. Add 150 mg NaOH to adjust the pH of the solution to 11.5, stir well, and obtain an iridium salt solution.

[0097] S2: Add 35 mL of cocamidopropyl betaine to the above iridium salt solution and stir well to obtain a gray-green, semi-transparent reverse micelle solution A;

[0098] S3: Add 35 mL of cocamidopropyl betaine to 100 mL of a 15 wt% dilute ammonia solution, stir and mix evenly to obtain reverse micelle solution B;

[0099] S4: After mixing reverse micelle solution A and reverse micelle solution B at a mass ratio of 2:5, a suspended colloidal solution system is formed. This system is then placed in an ultrasonic monochromatic photocatalytic (LED lamp) reactor for dispersion (ultrasonic frequency 20kHz; monochromatic light wavelength 700–900nm; light intensity 900W / m²). 2After dispersing for 3 hours, an iridium oxide colloidal solution was obtained.

[0100] S5: Add dilute sulfuric acid to the iridium oxide colloidal solution to adjust the pH of the solution to 7.5;

[0101] S6: After centrifuging and filtering the mixture obtained in step S5, the precipitate is ultrasonically washed with methanol and water in sequence; then it is vacuum dried at 110℃ for 6 hours; finally, the dried material is calcined at 500℃ for 2 hours to obtain nano-iridium oxide (IrO2), the particle size of which is about 35nm.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing iridium oxide powder using the conventional Adams melting method, comprising the following steps:

[0104] S1: Accurately weigh 50 mg of black-green crystalline chloroiridic acid, add it to 100 g of 1.5% potassium nitrate solution, and dissolve it with 800 mg of potassium nitrate in 50 mL of water. Then heat and mix the mixture at 90 °C for 6 h. After the reaction is complete, pour the reaction product into a disc evaporator and evaporate it to dryness to obtain the evaporated solid powder.

[0105] S2: The solid powder was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min. After holding at the temperature for 2 hours, it was taken out and cooled to room temperature. Then, the product was washed with methanol and dried to obtain black iridium oxide particles with a size of about 250 nm.

[0106] Comparative Example 2

[0107] This comparative example provides a method for preparing iridium oxide powder using a conventional hydrothermal synthesis method, including the following steps:

[0108] S1: Accurately weigh 50 mg of black-green crystalline chloroiridic acid and add it to 150 g of 0.2% sodium hydroxide solution. After stirring evenly, place the mixture in a common hydrothermal reactor, seal and stir, and react at 110 °C for 10 h. After the reaction is completed, wash and dry the reaction product with methanol and water respectively.

[0109] S2: The dried reaction product was placed in a muffle furnace and heated to 400°C at a heating rate of 5°C / min. After holding at this temperature for 1 hour, the product was removed and cooled to room temperature. The product was then washed with methanol and dried to obtain black iridium oxide particles with a size of approximately 200 nm.

[0110] The products obtained in Examples 1, 2, and 3 of this invention were characterized by XRD, and the results are as follows: Figure 2 As shown. From Figure 2It can be seen that the products obtained in Examples 1, 2, and 3 of this invention all exhibit obvious diffraction peaks at diffraction angles of 27.2°, 34.5°, 54.1°, and 66.8°, respectively. Figure 1 After comparison with the standard spectrum of iridium oxide, it was confirmed that the diffraction peaks of the crystal planes (110), (101), (211), and (112) of iridium oxide were obtained. It can be clearly seen that the product synthesized by the reverse micelles has basically no impurity peaks, indicating that the iridium oxide prepared in Examples 1, 2, and 3 of this invention has high purity. This is mainly because the presence of the reverse micelles during synthesis inhibits the aggregation of particles.

[0111] To further understand the surface microstructure of iridium oxide, a certain amount of iridium oxide samples from Examples 1, 2, Comparative Example 1, and 2 were characterized by transmission electron microscopy (TEM) to study their surface distribution characteristics. Figure 3 The TEM spectrum of iridium oxide prepared in Example 1; Figure 4 The TEM spectrum of iridium oxide prepared in Example 2; Figure 5 The image shows the TEM spectrum of iridium oxide prepared in Comparative Example 1. Figure 6 The image shows the TEM spectrum of iridium oxide prepared in Comparative Example 2.

[0112] from Figures 3 to 6 It can be seen that the iridium oxide particles prepared in Examples 1 and 2 have small particle sizes, only about 5-10 nm, and the particle size distribution is very uniform. This is mainly because the colloidal system formed during the synthesis of iridium oxide can prevent the agglomeration of iridium oxide particles due to adsorption by interaction forces, and can significantly inhibit particle agglomeration. In contrast, the iridium oxide particles prepared in Comparative Examples 1 and 2 have significantly larger particle sizes and obvious agglomeration effects, with particle sizes ranging from about 10-30 nm, and their particle distribution and shape are irregular. This is mainly because Comparative Example 1 uses the Adams melt method to prepare iridium oxide, which is prone to thermal decomposition and impurities during the preparation process. The adsorption force of the impurities themselves leads to an increase in particle size; moreover, the preparation process uses a high-temperature reaction, which cannot inhibit the aggregation of small particles with high surface free energy into large particles. Comparative Example 2 uses a traditional hydrothermal synthesis process to prepare iridium oxide in an alkaline environment. During this reaction, the alkali in the system reacts rapidly with the added raw materials to generate hydroxides. However, due to the properties of iridium hydroxide, its particle size is relatively large. Therefore, after reheating, the prepared iridium oxide particles are still very large. Moreover, under hydrothermal conditions, the particles are particularly prone to sticking together and growing into fibrous products, which will greatly reduce the specific surface area and active sites of the reaction products.

[0113] To test the actual electrochemical performance of iridium oxide prepared with reverse micelle assistance, appropriate amounts of iridium oxide from Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 were tested, primarily focusing on its electrocatalytic oxygen evolution reaction (OER) performance. The test method followed the standard system: a three-electrode test system using a commonly used calomel electrode as the reference electrode, 0.1M perchloric acid as the solution, and 15 μg of iridium oxide catalyst (accurately weighed) coated on the electrode tip. After oxygen saturation, cv activation was performed, followed by OER testing at a scan rate of 5 mV / s. The test results are shown below. Figure 7 As shown.

[0114] from Figure 7 It is evident that the iridium oxide prepared in Examples 1, 2, and 3 of this invention exhibits significantly better electrocatalytic oxygen evolution performance than the iridium oxide synthesized in Comparative Examples 1 and 2, indicating that the iridium oxide synthesized in these examples is more suitable for PEM water electrolysis to produce hydrogen.

[0115] In summary, it can be seen that the present invention can eliminate the shortcomings of traditional processes such as complex procedures, particle agglomeration, and low purity of iridium oxide. In addition, the nano-iridium oxide prepared by the present invention has good dispersibility, can eliminate the influence of internal diffusion, has small particle size, and has coordination unsaturated active sites, resulting in high catalytic activity and extremely high application value.

[0116] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0117] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing nano iridium oxide, characterized in that, The method comprises the following steps: S1: dissolving iridium salt in water, adding alkaline substance to adjust the pH value of the solution to 11-12 to obtain an iridium salt solution; S2: adding reverse micelle surfactant to the iridium salt solution to obtain a reverse micelle solution A; S3: adding reverse micelle surfactant to the weak base solution to obtain a reverse micelle solution B; S4: mixing the reverse micelle solution A and the reverse micelle solution B, and then dispersing under the conditions of ultrasonic and monochromatic light irradiation to obtain an iridium oxide colloidal solution; S5: adding acidic substance to the iridium oxide colloidal solution to adjust the pH value of the solution to 7-8; S6: centrifugal filtering the mixture obtained in the step S5, and then sequentially performing ultrasonic washing, vacuum drying and calcination on the obtained precipitate to obtain the nano iridium oxide.

2. The method of claim 1, wherein the nano-sized iridium oxide is prepared by the process of claim 1, wherein the process is performed at a temperature of 300 to 600 °C. In the step S1, the iridium salt comprises at least one of IrCl3, K2IrCl6 and Ir(O2CCH3)3; the concentration of the iridium salt solution is 1-5 mg / mL. And / or, the alkaline substance comprises at least one of NaOH, KOH, urea, Na3PO4, ammonia water and Na2CO3.

3. The method for preparing nano-iridium oxide according to claim 1, characterized in that, In the step S2, the mass ratio of the iridium salt in the iridium salt solution to the reverse micelle surfactant is (2-6):

1.

4. The method for preparing nano-iridium oxide according to claim 1, characterized in that, In the step S3, the weak base solution comprises at least one of ammonia water solution, urea solution, sodium hydroxide solution, potassium hydroxide solution, sodium phosphate solution and sodium carbonate solution, and the mass concentration of the weak base solution is 8-20 wt%; And / or, in the reverse micelle solution B, the addition amount of the reverse micelle surfactant is 10-100 mg / mL.

5. The method for preparing nano-iridium oxide according to claim 1, characterized in that, In the steps S2 and / or S3, the reverse micelle surfactant comprises at least one of cetyltrimethylammonium bromide, 1,4-sorbitan, isosorbide, sodium bis(2-ethylhexyl) sulfosuccinate, cocamidopropyl betaine, lauryl polyether sulfate and sodium oleate.

6. The method for preparing nano-iridium oxide according to claim 1, characterized in that, In the step S4, the mass ratio of the reverse micelle solution A to the reverse micelle solution B is (1-10):(1-10); And / or, the ultrasonic and the monochromatic light irradiation are performed simultaneously; the temperature of the ultrasonic and the monochromatic light irradiation is normal temperature, and the time is 2-5 h; And / or, when the ultrasonic is performed, the frequency of the ultrasonic wave is 20-25 kHz; And / or, the monochromatic light has a wavelength of 360-950 nm and an illumination intensity of 200-2000 W / m 2 .

7. The method for preparing nano-iridium oxide according to claim 1, characterized in that, In the step S5, the acidic substance comprises at least one of sulfuric acid, phosphoric acid, hydrochloric acid, boric acid, citric acid and adipic acid.

8. The method for preparing nano-iridium oxide according to claim 1, characterized in that, In the step S6, the ultrasonic washing is sequentially performed using methanol and water; And / or, the temperature of the vacuum drying is 50-130℃, and the drying time is 4-24 h; And / or, the temperature of the calcination is 400-800℃, and the calcination time is 2-3 h.

9. The nano iridium oxide prepared by the preparation method of any one of claims 1-8, characterized in that, The particle size of the nano iridium oxide is 35-110 nm.

10. The nano iridium oxide of claim 9 is used as an oxygen evolution reaction catalyst in PEM water electrolysis.

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