High-dispersity IrO2 catalyst as well as preparation method and application thereof

Abstract

The invention provides a high-dispersity IrO2 catalyst and a preparation method and application thereof.Compared with the prior art, dopamine hydrochloride and iridium ions are subjected to complexing and then polymerization, a single-particle aggregation state elementary substance iridium / polydopamine precursor similar to a frog egg shape is prepared, and then filtering, drying, grinding, calcining, cleaning and other steps are conducted, so that the high-dispersity IrO2 catalyst is obtained. Finally, the high-dispersity IrO2 catalyst is obtained. The catalyst has excellent performance in PEM electrolyzed water application, and can realize a voltage below 1.688 V at 60 DEG C under a current density of 1A / cm < 2 >. In addition, through polymerization of dopamine hydrochloride complexed iridium ions, the problem that traditional elementary iridium particles cannot be precipitated is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a highly dispersed IrO2 catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasingly serious global energy crisis and environmental pollution problems, the development and utilization of clean energy have become a research hotspot. Hydrogen production by electrolyzing water, as a clean way to produce hydrogen energy, has broad application prospects.

[0003] During the electrolysis of water, the performance of the catalyst directly affects the electrolysis efficiency and economy. At present, IrO2 catalysts have been widely studied due to their excellent catalytic activity and stability, but their high cost and low dispersion limit their large-scale application.

[0004] Traditional preparation methods of IrO2 catalysts mainly include precipitation method, sol-gel method, etc., but the catalysts prepared by these methods often have problems such as poor dispersion and few active sites.

[0005] Therefore, developing a highly dispersed, low-cost and excellent-performance IrO2 catalyst has become an important research direction. By continuously optimizing the catalyst preparation method and technology, it is expected to achieve the large-scale application of the hydrogen energy industry and contribute to the global clean energy transformation. Summary of the Invention

[0006] The purpose of the present invention is to provide a highly dispersed IrO2 catalyst and a preparation method thereof. By dissolving raw materials and dopamine hydrochloride in an ethylene glycol solution to form a single-particle aggregated precursor similar to frog eggs, not only can highly dispersed IrO2 be obtained, but also it can be directly centrifuged and separated, greatly reducing the production difficulty and maintaining the high specific surface area of the final product.

[0007] Another purpose of the present invention is to provide an application of the highly dispersed IrO2 catalyst. The highly dispersed IrO2 catalyst obtained by the above preparation of the present invention shows excellent performance in PEM water electrolysis applications, with characteristics such as low voltage and high current density.

[0008] The specific technical solution of the present invention is as follows:

[0009] A preparation method of a highly dispersed IrO2 catalyst, comprising the following steps:

[0010] 1) Mix an iridium source, a reducing agent, dopamine hydrochloride and a Tris buffer, and heat for reaction;

[0011] 2) Grind after the reaction and then calcine to obtain a highly dispersed IrO2 catalyst;

[0012] In Step 1), the dosage ratio of the iridium source to the reducing agent is 0.2 - 200 g : 100 - 5000 ml;

[0013] In Step 1), the mass ratio of the iridium source to dopamine hydrochloride is 0.2 - 200 : 0.1 - 80;

[0014] In Step 1), the mass ratio of dopamine hydrochloride to the buffer is 3 : 1 - 1 : 1;

[0015] In Step 1), the reducing agent is ethylene glycol; the iridium source is selected from iridium trichloride or chloroiridic acid; the Tris buffer is tris(hydroxymethyl)aminomethane.

[0016] The heating reaction in Step 1) refers to 180 - 200 °C; the duration of the continuous reaction is 30 - 200 minutes;

[0017] In Step 1), after the reaction is completed, it is filtered, washed repeatedly with deionized water, and then dried;

[0018] The grinding in Step 2) refers to grinding in sodium nitrate, using a zirconia ball mill pot, with a ball-to-material ratio between 5 : 1 and 8 : 1, a rotation speed of 100 - 400 revolutions per minute, for 20 - 150 minutes, until the color of the slurry is completely uniform;

[0019] In Step 1), the mass ratio of the iridium source to the sodium nitrate used in Step 2) is 0.2 - 200 : 5 - 5000;

[0020] The calcination in Step 2) refers to calcining at 300 - 500 °C in air or oxygen for 30 - 200 minutes;

[0021] In Step 2), after calcination, it is cooled to room temperature, washed repeatedly with deionized water, centrifuged until the supernatant contains no particles, dried at 60 - 100 °C for 12 - 24 h and ground, with a particle size of 20 nm - 5 μm, to obtain a highly dispersed IrO₂ catalyst.

[0022] A highly dispersed IrO₂ catalyst is prepared by dissolving iridium trichloride or other iridium-containing compounds, dopamine hydrochloride, and Tris buffer in an ethylene glycol solution, by controlling parameters such as the dosage of each raw material, reaction temperature, reaction time, calcination temperature, etc. and its separation and purification means.

[0023] A highly dispersed IrO₂ catalyst provided by the present invention is prepared by the above method, and the primary particle size of the highly dispersed IrO₂ catalyst is between 5 - 10 nm.

[0024] An application of a highly dispersed IrO₂ catalyst provided by the present invention, as a catalyst for the application of electrolyzing water. It exhibits excellent performance, with characteristics such as low voltage and high current density. At 60 °C, 1 A / cm2 The voltage reached below 1.688V at the current density.

[0025] The inventors have found that nano-sized iridium metal single substance with a size of about 3-5 nm can be synthesized by ethylene glycol reduction method, and then oxidized to obtain iridium oxide catalytic material with high specific surface area, but the monodispersed nano-sized metal iridium is already in a suspended state in the ethylene glycol solution, and it cannot be well separated by centrifugation or filtration. The present invention dissolves the iridium-containing compound in a reducing agent and adds dopamine hydrochloride and Tris buffer, then heats the mixed solution to a certain temperature for a period of time, and then filters, dries, adds sodium nitrate to grind, calcines and washes, centrifuges, dries, and finally obtains a highly dispersed IrO2 catalyst.

[0026] In the present invention, ethylene glycol is not only used as a solvent, but also has reducing properties, which assists in regulating the reduction process of the iridium precursor. During the preparation, dopamine hydrochloride first complexes the iridium ions and then self-polymerizes to form PDA particles anchored with elemental iridium particles, forming a "core-shell" structure similar to frog eggs (iridium core / PDA shell). In the early stage of calcination, PDA is also used as a carbon / nitrogen source, and pyrolyzes to generate a porous carbon skeleton during the calcination process, which limits the migration and agglomeration of iridium particles. In the later stage of calcination, the carbon layer is oxidized and escaped (generating CO2) to form a porous structure, which promotes the dispersion of IrO2 nanoparticles. In conjunction with the grinding before the precursor is calcined, the physical agglomeration between the precursor particles is destroyed, the specific surface area is increased, the oxygen diffusion is more uniform during the subsequent calcination, and local sintering is reduced. At the same time, the IrO2 particles generated by calcination have a greater density due to the high crystallinity, which solves the problem that the traditional elemental iridium may be difficult to settle due to the colloidization of ultrafine particles.

[0027] Porous carrier effect: If PDA is not completely oxidized, the residual microporous carbon skeleton can be used as a carrier to load IrO2, forming a "carbon-loaded IrO2" composite structure and increasing the particle sedimentation rate.

[0028] Compared with the prior art, the present invention prepares a single-particle aggregated iridium / polydopamine precursor with a frog egg-like morphology by first complexing dopamine hydrochloride with iridium ions and then polymerizing them, and then undergoes filtering, drying, grinding, calcining and washing to finally obtain a highly dispersed IrO2 catalyst. The catalyst has excellent performance in PEM water electrolysis applications and can be used at 60°C, 1A / cm 2 The voltage below 1.688 V was achieved under the current density. In addition, the method solves the problem that the traditional single iridium particles cannot be precipitated by polymerizing the iridium ions complexed with dopamine hydrochloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM image of the metallic iridium particles obtained in Example 1;

[0030] Figure 2 XRD pattern of the iridium oxide catalyst obtained in Example 1;

[0031] Figure 3 Performance test chart obtained in Example 1. Detailed implementation manners

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the scope of protection of the present invention.

[0033] The test materials and reagents used in the following embodiments can be obtained from commercial sources without special instructions.

[0034] For those not specifying specific technologies or conditions in the embodiments, they can all be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0035] Example 1

[0036] A preparation method of a highly dispersed IrO2 catalyst includes the following steps:

[0037] Take 5 g of iridium trichloride, 2.5 g of dopamine hydrochloride and 2.5 g of tris(hydroxymethyl)aminomethane, dissolve them in 100 ml of ethylene glycol solution, heat up to 190 °C and react for 60 minutes. After the obtained product is filtered and dried, add it to 100 g of sodium nitrate for dispersion. Use a zirconia ball mill pot with a ball-to-material ratio of 5:1, a rotation speed of 200 revolutions per minute, and a time of 100 minutes. Grind until the color of the slurry is completely uniform, calcine in air at 400 °C for 60 minutes, and finally wash repeatedly with deionized water and centrifuge until the supernatant is clear, dry and grind to obtain the product.

[0038] According to the performance test of the "PEM Electrolyzer Performance Test Method" (during the solicitation of opinions stage), at a catalyst loading of 0.8 mg / cm 2 , 60 °C, and a current density of 1 A / cm 2 , the voltage is 1.672 V.

[0039] Figure 1 TEM image of the iridium metal particles obtained in Example 1, and the primary particle size is between 5 - 10 nm. Figure 2 XRD pattern of the iridium oxide catalyst obtained in Example 1; proving the composition of the product.

[0040] Example 2

[0041] A preparation method of a highly dispersed IrO₂ catalyst, comprising the following steps:

[0042] Take 20 g of iridium trichloride, 10 g of dopamine hydrochloride and 5 g of tris(hydroxymethyl)aminomethane, dissolve them in 400 ml of ethylene glycol solution, heat up to 190 °C and react for 60 minutes. After the obtained product is filtered and dried, it is dispersed in 400 g of sodium nitrate. Using a zirconia ball mill pot, the ball-to-material ratio is 6:1, the rotation speed is 300 revolutions per minute, and the time is 40 minutes. Grind until the color of the slurry is completely uniform, calcine in air at 400 °C for 60 minutes, and finally wash repeatedly with deionized water, centrifuge, dry and grind to obtain the product.

[0043] According to the performance test of the "PEM Electrolyzer Performance Test Method" (in the stage of soliciting opinions), the loading is 0.8 mg / cm 2 ,60 °C, 1 A / cm 2 At the current density, the voltage is 1.679 V.

[0044] Example 3

[0045] A preparation method of a highly dispersed IrO₂ catalyst, comprising the following steps:

[0046] Take 10 g of iridium chloroacid, 5 g of dopamine hydrochloride and 2.5 g of tris(hydroxymethyl)aminomethane, dissolve them in 200 ml of ethylene glycol solution, heat up to 180 °C and react for 30 minutes. After the obtained product is filtered and dried, it is dispersed in 200 g of sodium nitrate. Using a zirconia ball mill pot, the ball-to-material ratio is 5:1, the rotation speed is 400 revolutions per minute, and the time is 30 minutes. Grind until the color of the slurry is completely uniform; calcine in air at 350 °C for 30 minutes, and finally wash repeatedly with deionized water, centrifuge, dry and grind to obtain the product.

[0047] According to the performance test of the "PEM Electrolyzer Performance Test Method" (in the stage of soliciting opinions), the loading is 0.5 mg / cm 2 ,60 °C, 1 A / cm 2 At the current density, the voltage is 1.688 V.

[0048] Example 4

[0049] A preparation method of a highly dispersed IrO₂ catalyst, comprising the following steps:

[0050] Take 20 g of iridium chloride hydrate, 10 g of dopamine hydrochloride and 3.5 g of tris(hydroxymethyl)aminomethane, dissolve them in 500 ml of ethylene glycol solution, heat up to 195 °C and react for 30 minutes. The obtained product is filtered and dried, then added to 300 g of sodium nitrate for dispersion. Use a zirconia ball milling tank with a ball-to-material ratio of 6:1, a rotation speed of 300 revolutions per minute, and a time of 40 minutes. Grind until the color of the slurry is completely uniform, calcine in air at 300 °C for 30 minutes, and finally wash repeatedly with deionized water, dry and grind to obtain the product.

[0051] According to the performance test of "PEM Electrolyzer Performance Test Method" (in the stage of soliciting opinions), the loading is 0.8 mg / cm 2 , at 60 °C and a current density of 1 A / cm 2 , the voltage is 1.682 V.

[0052] The description of the above embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of a highly dispersed IrO2 catalyst, characterized in that, The preparation method includes the following steps: 1) Mix an iridium source, a reducing agent, dopamine hydrochloride, and a buffer, and heat for reaction; 2) After the reaction, grind and then calcine to obtain a highly dispersed IrO2 catalyst.

2. The preparation method according to claim 1, characterized in that, In step 1), the dosage ratio of the iridium source to the reducing agent is: 0.2 - 200 g : 100 - 5000 ml.

3. The preparation method according to claim 1 or 2, characterized in that, In step 1), the mass ratio of the iridium source to dopamine hydrochloride is: 0.2 - 200 : 0.1 - 80; the mass ratio of dopamine hydrochloride to the buffer is: 3 : 1 - 1 :

1.

4. The preparation method according to claim 1 or 2, characterized in that, In step 1), the reducing agent is ethylene glycol.

5. The preparation method according to claim 1 or 3, characterized in that, In step 1), the buffer is tris(hydroxymethyl)aminomethane.

6. The preparation method according to claim 1 or 2, characterized in that, The heating reaction in step 1) means 180 - 200 °C; the reaction time is 30 - 200 minutes.

7. The preparation method according to claim 1, wherein The grinding in step 2) means grinding in sodium nitrate.

8. The preparation method according to claim 1, wherein The calcination in step 2) means calcining at 300 - 500 °C in air or oxygen for 30 - 200 minutes.

9. A highly dispersed IrO2 catalyst prepared by the preparation method according to any one of claims 1 - 8.

10. Use of the highly dispersed IrO₂ catalyst according to claim 9, characterized in that, Use as a catalyst for water electrolysis.

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