Preparation method of nano iridium catalyst

Abstract

The invention discloses a preparation method of a nano iridium catalyst, which comprises the following steps: S1, dissolving an iridium precursor in water to obtain an iridium precursor solution, and ultrasonically dissolving a dispersing agent in a reducing agent solution to obtain a dispersing agent solution; s2, slowly dropwise adding the dispersing agent solution into the iridium precursor solution under a violent stirring condition, and stirring at room temperature to obtain a mixed solution; s3, heating and refluxing the mixed solution obtained in the step S2; s4, cooling the solution obtained by heating and refluxing in the step S3 to room temperature under vigorous stirring, and then drying to obtain a solid product; and S5, sequentially carrying out sufficient grinding, heat treatment, cleaning and drying on the solid product prepared in the step S4 to finally obtain the nano iridium catalyst. The nano iridium catalyst prepared by the method is relatively small and uniform in synthesis size, good in dispersity and relatively high in catalytic activity.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic material preparation, and in particular to a method for preparing a nano iridium catalyst. Background Art

[0002] Hydrogen energy is regarded as the clean energy with the greatest development potential in the 21st century and has become an important part of the future global energy strategy. Leading hydrogen energy countries have successively adjusted their national hydrogen energy strategies, significantly increased development goals, and increased support. Among them, proton exchange membrane (PEM) water electrolysis hydrogen production technology is a very promising sustainable water electrolysis hydrogen production technology. In scenarios with high wind-solar coupling, the hydrogen production system can achieve second-level start and stop, and can better adapt to the peak and valley changes of wind and solar energy. PEM is a strongly acidic environment with serious corrosion problems, so it is extremely dependent on non-corrosive precious metal materials. Iridium-based catalysts are key catalyst materials required for PEM water electrolysis technology due to their excellent oxygen evolution activity and stability.

[0003] At present, iridium-based catalysts are mainly nano-iridium oxide and iridium black. The nanoparticles are often uneven in size and have poor dispersion, which limits their catalytic performance. Most traditional preparation methods have the disadvantages of relatively complex preparation processes and high costs. Some also have problems such as low purity and low yield, and even involve environmental pollution by hazardous chemicals such as alkali solutions. Therefore, the development and design of an iridium-based catalyst with simple process, small and uniform size, good dispersion, and excellent performance in electrocatalytic water decomposition to produce hydrogen is the future research and development focus of the hydrogen energy industry. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention aims to provide a method for preparing a nano-iridium catalyst.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing a nano-iridium catalyst comprises the following steps:

[0007] S1, dissolving an iridium precursor in water to obtain an iridium precursor solution, and ultrasonically dissolving a dispersant in a reducing agent solution to obtain a dispersant solution;

[0008] S2, slowly dripping the dispersant solution into the iridium precursor solution under vigorous stirring, and stirring at room temperature to obtain a mixed solution;

[0009] S3, heating the mixed solution obtained in step S2 to reflux;

[0010] S4, cooling the solution obtained by heating to reflux in step S3 to room temperature under vigorous stirring, and then drying to obtain a solid product;

[0011] S5, grinding, heat treating, cleaning and drying the solid product obtained in step S4 in sequence to finally obtain a nano-iridium catalyst.

[0012] Furthermore, in step S1, the iridium precursor includes one or more of chloroiridic acid, iridium trichloride, iridium tetrachloride, ammonium hexachloroiridate, and iridium acetate; wherein the mass fraction of the iridium precursor dissolved in water is 0.1-10 mg / mL.

[0013] Furthermore, in step S1, the dispersant is polyvinyl pyrrolidone, the mass fraction of the dispersant dissolved in the reducing agent solution is 1-50 mg / mL, and the mass ratio of the iridium precursor to the dispersant is 1:5-1:10.

[0014] Furthermore, in step S1, the reducing agent solution includes one or both of anhydrous ethanol and ethylene glycol.

[0015] Furthermore, in step S2, the stirring time at room temperature is 12 hours.

[0016] Furthermore, in step S3, the temperature of heating and reflux is 100° C. and the time is 6-12 hours.

[0017] Furthermore, in step S4, the drying method is a combination of one or more of forced air oven drying, rotary evaporation drying and vacuum drying.

[0018] Furthermore, the specific process of step S5 is: grinding the solid product obtained in step S4 by mechanical grinding to obtain a powdered heat treatment precursor, and then evenly dispersing the heat treatment precursor on a crucible for heat treatment, the heat treatment temperature is 450-500°C, the time is 3-5 hours, and the gas atmosphere is air or oxygen; the solid sample after heat treatment is washed with deionized water and then dried in an oven.

[0019] Furthermore, in step S5, an atmosphere furnace or a tube furnace is used for heat treatment.

[0020] The invention also provides a nano-iridium catalyst prepared by the method.

[0021] The beneficial effects of the present invention are:

[0022] 1. It should be noted that polyvinyl pyrrolidone (PVP) is a low-cost, commercialized water-soluble polymer, which is widely used as a dispersant and stabilizer for precious metal nanomaterials. PVP can be multiple-coordinated on the nano surface through the skeleton NC=O, and the binding force of this coordination mode is not strong, which is conducive to the preparation of iridium nanoparticles with controllable particle size and morphology. Compared with the use of sodium borohydride, which is harmful to humans and the environment, as a reducing agent, the alcohol reduction method used in the present invention is simple to operate and green and safe, and also avoids the use of hazardous chemicals such as strong alkali. By heating and refluxing for a long enough time, the reducing agent fully reduces the iridium precursor to iridium nanoparticles and combines with PVP to form a stable iridium nano solution. Then, the excess reducing agent and water are removed by drying to avoid the huge loss caused by filtration in the traditional chemical precipitation method. The dried iridium nano solid is ground to obtain an iridium nano powder so that it can be evenly dispersed in a crucible so that the sample is evenly heated during the heat treatment process. After heat treatment at a certain temperature in air or oxygen atmosphere, PVP is thermally decomposed, and finally the residual reactants and impurities are removed by washing, and a pure nano iridium catalyst product can be obtained after drying. The nano-iridium catalyst prepared by the invention has a small and uniform synthesis size, good dispersibility and high catalytic activity.

[0023] 2. The process of the present invention does not involve precipitation and filtration processes, which can reduce the loss of iridium raw materials;

[0024] 3. The chemical reagents selected are low-cost and environmentally friendly, and avoid the use of hazardous chemicals such as alkali or sodium borohydride;

[0025] 4. The process of the present invention is simple, has good repeatability, simple preparation process and reaction equipment, and is easy to industrialize and scale up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process flow in Examples 1-3 of the present invention.

[0027] Figure 2 This is the X-ray diffraction pattern of the nano-iridium catalyst prepared in Example 1 of the present invention.

[0028] Figure 3 This is a TEM photo of the nano-iridium catalyst prepared in Example 1 of the present invention.

[0029] Figure 4 This is the LSV test curve of the nano-iridium catalyst prepared in Example 1 of the present invention.

[0030] Figure 5 This is the X-ray diffraction pattern of the nano-iridium catalyst prepared in Example 2 of the present invention.

[0031] Figure 6 This is the X-ray diffraction pattern of the nano-iridium catalyst prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0033] Example 1

[0034] This embodiment provides a method for preparing a nano-iridium catalyst. Figure 1 As shown, the following steps are included:

[0035] S1. Weigh 100 mg of iridium trichloride and dissolve it in 1000 mL of ultrapure water to obtain an iridium trichloride aqueous solution (0.1 mg / mL); and weigh 1000 mg of polyvinyl pyrrolidone and ultrasonically dissolve it in 1000 mL of anhydrous ethanol (1 mg / mL). The mass ratio of the iridium precursor iridium trichloride to the dispersant polyvinyl pyrrolidone is 1:10.

[0036] S2. Under vigorous stirring, slowly drip the anhydrous ethanol solution of polyvinyl pyrrolidone into the aqueous solution of iridium trichloride, and stir at room temperature for 12 hours;

[0037] S3, heating the mixed solution obtained in step S2 to 100° C. and heating under reflux for 6 hours;

[0038] S4. The solution after heating under reflux was cooled to room temperature under vigorous stirring, and then dried using a rotary evaporator to obtain a black solid.

[0039] S5, the black solid obtained in step S4 is fully ground to obtain a black powder, and then the black powder is evenly spread on a crucible, heated in a tube furnace, introduced into an air atmosphere, and kept at 450° C. for 3 hours. The heat-treated powder is then washed 5 times with deionized water, placed in a vacuum drying oven at 60° C. and dried for 12 hours to obtain a nano iridium catalyst.

[0040] The nano-iridium catalyst prepared in step S5 was subjected to an LSV curve test: the test equipment was an electrochemical workstation (Chenhua CHI660E), 0.1 mol / L perchloric acid was used as the electrolyte, the LSV test program was set to a scan rate of 2 mV / s, and the test was repeated until the LSV curves overlapped. The last circle of data after the overlap was taken, and the overpotential was the voltage value corresponding to a current density of 10 mA / cm2 minus 1.23 volts.

[0041] Figure 2 This is the X-ray diffraction pattern of the nano-iridium catalyst prepared in Example 1 of the present invention. Figure 2 It can be seen that the prepared product is iridium. Figure 3 This is a TEM photo of the nano-iridium catalyst prepared in Example 1 of the present invention. Figure 3 It can be seen that the prepared nano-iridium catalyst has a size of 1-2 nanometers, is small and uniform in size, and has good dispersion. Figure 4 This is the LSV test curve of the nano-iridium catalyst prepared in Example 1 of the present invention. Figure 4 It can be seen that the nano-iridium catalyst is at 10mA / cm 2 The overpotential at the current density is only 254 mV, indicating that the prepared nano-iridium catalyst has high catalytic activity.

[0042] Example 2

[0043] This embodiment provides a method for preparing nano-iridium. Figure 1 As shown, the following steps are included:

[0044] S1. Weigh 200 mg of iridium trichloride and dissolve it in 50 mL of ultrapure water to obtain an iridium trichloride solution (4 mg / mL); weigh 1000 mg of polyvinyl pyrrolidone and ultrasonically dissolve it in 50 mL of anhydrous ethanol (20 mg / mL), and the mass ratio of the iridium precursor iridium trichloride to the dispersant polyvinyl pyrrolidone is 1:5.

[0045] S2. Under vigorous stirring, slowly drip the anhydrous ethanol solution of polyvinyl pyrrolidone into the iridium trichloride solution, and stir at room temperature for 12 hours;

[0046] S3. The mixed solution obtained in step S2 is heated to 100° C. and heated under reflux for 12 hours.

[0047] S4. The solution after heating under reflux was cooled to room temperature under vigorous stirring, and then placed in a forced air drying oven for drying at 70° C. for 48 hours to obtain a black solid.

[0048] S5, the black solid obtained in step S4 is fully ground to obtain a black powder, and then the black powder is evenly spread on a crucible, heated in a tube furnace, introduced into an air atmosphere, and kept at 500° C. for 3 hours. The heat-treated powder is washed 5 times with deionized water, and then placed in a vacuum drying oven at 60° C. for 12 hours to obtain a nano iridium catalyst after drying.

[0049] Figure 5 This is the X-ray diffraction pattern of nano-iridium prepared in Example 2 of the present invention. Figure 5 It can be seen that the prepared product is iridium.

[0050] Example 3

[0051] This embodiment provides a method for preparing nano-iridium. Figure 1 As shown, the following steps are included:

[0052] S1. Weigh 500 mg of chloroiridic acid and dissolve it in 50 mL of ultrapure water to obtain an aqueous solution of chloroiridic acid (10 mg / mL); weigh 2500 mg of polyvinyl pyrrolidone and dissolve it in 50 mL of ethylene glycol by ultrasonication (50 mg / mL), and the mass ratio of the iridium precursor chloroiridic acid to the dispersant polyvinyl pyrrolidone is 1:5.

[0053] S2. Under vigorous stirring, slowly drip the ethylene glycol solution of polyvinyl pyrrolidone into the aqueous solution of iridium tetrachloride, and stir at room temperature for 12 hours;

[0054] S3. The mixed solution obtained in step S2 is heated to 100° C. and heated under reflux for 8 hours.

[0055] S4. The solution after heating under reflux was cooled to room temperature under vigorous stirring, and the solvent was removed by a rotary evaporator to obtain a black solid.

[0056] S5, the black solid obtained in step S4 is fully ground to obtain a black powder, the black powder is evenly spread on a crucible, heated in a tube furnace, introduced into a nitrogen atmosphere, and kept at 500° C. for 5 hours. The heat-treated powder is washed 5 times with deionized water, and then placed in a vacuum drying oven at 60° C. for 12 hours to obtain a nano-iridium catalyst.

[0057] Figure 6 This is the X-ray diffraction pattern of the nano-iridium catalyst prepared in Example 3 of the present invention. Figure 6 It can be seen that the prepared product is iridium.

[0058] The above results show that Examples 1-3 prepare high-purity nano-iridium catalysts, which have a nanostructure, are small and uniform in size, have good dispersibility, and have high catalytic activity.

[0059] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a nano-iridium catalyst, characterized in that: The steps include: S1, dissolving an iridium precursor in water to obtain an iridium precursor solution, and ultrasonically dissolving a dispersant in a reducing agent solution to obtain a dispersant solution; S2, slowly dripping the dispersant solution into the iridium precursor solution under vigorous stirring, and stirring at room temperature to obtain a mixed solution; S3, heating the mixed solution obtained in step S2 to reflux; S4, cooling the solution obtained by heating to reflux in step S3 to room temperature under vigorous stirring, and then drying to obtain a solid product; S5. Grind, heat-treat, clean and dry the solid product obtained in step S4 in sequence to finally obtain a nano-iridium catalyst.

2. The nano-iridium catalyst according to claim 1, characterized in that: In step S1, the iridium precursor includes one or more of chloroiridic acid, iridium trichloride, iridium tetrachloride, ammonium hexachloroiridate, and iridium acetate; wherein the mass fraction of the iridium precursor dissolved in water is 0.1-10 mg / mL.

3. The nano-iridium catalyst according to claim 1, characterized in that: In step S1, the dispersant is polyvinyl pyrrolidone, the mass fraction of the dispersant dissolved in the reducing agent solution is 1-50 mg / mL, and the mass ratio of the iridium precursor to the dispersant is 1:5-1:

10.

4. The nano-iridium catalyst according to claim 1, characterized in that: In step S1, the reducing agent solution includes one or both of anhydrous ethanol and ethylene glycol.

5. The nano-iridium catalyst according to claim 1, characterized in that: In step S2, the stirring time at room temperature is 12 hours.

6. The nano-iridium catalyst according to claim 1, characterized in that: In step S3, the temperature of heating and reflux is 100° C. and the time is 6-12 hours.

7. The nano-iridium catalyst according to claim 1, characterized in that: In step S4, the drying method is a combination of one or more of forced air oven drying, rotary evaporation drying and vacuum drying.

8. The nano-iridium catalyst according to claim 1, characterized in that: The specific process of step S5 is: grinding the solid product obtained in step S4 by mechanical grinding to obtain a powdered heat treatment precursor, and then evenly dispersing the heat treatment precursor on a crucible for heat treatment. The heat treatment temperature is 450-500°C, the time is 3-5 hours, and the gas atmosphere is air or oxygen; the solid sample after heat treatment is washed with deionized water and then dried in an oven.

9. The nano-iridium catalyst according to claim 1 or 8, characterized in that: In step S5, heat treatment is performed in an atmosphere furnace or a tube furnace.

10. A nano-iridium catalyst prepared by the method according to any one of claims 1 to 9.

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