Iridium oxide catalyst with dendritic pore structure, preparation method and application thereof in proton exchange membrane electrolysis water technology

Abstract

The application relates to an iridium oxide catalyst with a dendritic pore structure, a preparation method and application thereof in proton exchange membrane water electrolysis technology, and belongs to the technical field of water electrolysis. An iridium source is dissolved in water, then a mixed template agent is added, a pore expanding agent is added after dissolution, and a uniform emulsion is obtained after mixing uniformly; an initiator is added to carry out reaction, after the reaction is completed, the mixed solution of water and anhydrous ethanol with a volume ratio of 1:1 is used for centrifugal cleaning for 3-5 times, the template agent is washed away, and the iridium oxide catalyst with the dendritic pore structure is obtained after drying. Compared with commercial iridium oxide catalyst nanoparticles, the prepared iridium oxide catalyst with the dendritic pore structure provides more active sites, meanwhile, the rich pore structure significantly improves the mass transfer capacity of the catalyst, diffusion limitation existing in the poreless material is overcome, therefore, in a low iridium load, the PEM water electrolysis oxygen evolution reaction exhibits higher activity and stability, and high-efficiency oxygen evolution catalytic reaction is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of water electrolysis, and in particular relates to an iridium oxide catalyst with a dendritic pore structure, a preparation method and an application thereof in proton exchange membrane water electrolysis technology. Background Art

[0002] Hydrogen (green hydrogen) produced by electrolysis of water using renewable energy sources represented by photovoltaics and wind power is considered to be a key carrier for the success of energy transformation and has become the focus of various countries' efforts to accumulate strength. Proton exchange membrane (PEM) water electrolysis technology can convert intermittent renewable electricity into high-purity green hydrogen, and has become a key technology for my country's energy transformation. The core component of the PEM electrolyzer, the membrane electrode, gives it advantages such as high energy conversion efficiency, high current density and compact design. Given the large amount of iridium used in commercial membrane electrodes, the demand for iridium will increase significantly when applied on a large scale. However, the annual output of iridium is limited (<10 tons) and the price is high, making the contradiction between supply shortages and surging demand increasingly prominent. Therefore, reducing the amount of iridium in the membrane electrode while maintaining high catalytic performance is crucial for the widespread application of PEM water electrolysis technology.

[0003] In order to reduce the amount of iridium in the membrane electrode, the most important thing is to develop anode catalysts with higher catalytic performance. However, although a variety of new iridium-based materials developed in recent years have shown excellent catalytic activity in the three-electrode test of liquid electrolyzers in the laboratory, their high performance is difficult to reproduce in PEM electrolyzers. This is mainly due to the difference between the idealized three-electrode test conditions and the complex operating environment of the membrane electrode. When the operating circuit density of the PEM electrolyzer reaches the ampere level, the structural stability of the anode catalyst and the mass transfer process of the anode catalyst layer will face greater challenges. For example, in commercial PEM electrolyzers, iridium oxide catalyst nanoparticles are easy to aggregate, resulting in high loading (iridium loading is usually not less than 2 mg cm -2 ), the utilization rate of active sites in the membrane electrode is low, and the transport resistance of water and oxygen is increased. Therefore, it is imperative to design and synthesize iridium oxide catalysts with both high catalytic activity and excellent mass transfer performance. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide an iridium oxide catalyst with a dendritic pore structure, a preparation method and its application in proton exchange membrane water electrolysis technology.

[0005] The invention discloses a method for preparing an iridium oxide catalyst having a dendritic pore structure, comprising the following steps: dissolving an iridium source in water, adding a mixed template agent, adding a pore-enlarging agent after dissolution, and mixing uniformly to obtain a uniform emulsion; adding an initiator to carry out a reaction, and after the reaction is completed, centrifuging and washing 3 to 5 times with a mixed solution of water and anhydrous ethanol in a volume ratio of 1:1, washing away the template agent, and drying to obtain the iridium oxide catalyst having a dendritic pore structure; the obtained iridium oxide catalyst is a porous nanosphere or ellipsoid structure with a particle size of 100 to 400 nm; and the iridium oxide catalyst has an open dendritic pore structure with a pore size of 10 to 30 nm.

[0006] In the above method, the iridium source is one or a mixture of chloroiridic acid, iridium trichloride, iridium tetrachloride, potassium chloroiridate, and sodium chloroiridate;

[0007] In the above method, the mixed template agent is a mixture of EO-PO-EO block copolymer and quaternary ammonium salt surfactant, and the EO-PO-EO block copolymer is F127 (EO 106 -PO 70 -EO 106 )、F108(EO 132 -PO 50 -EO 132 )、P123(EO 20 -PO 70 -EO 20 ), the quaternary ammonium surfactant is a mixture of one or more of lauryl-octadecyltrimethylammonium chloride and lauryl-octadecyltrimethylammonium bromide;

[0008] In the above method, the pore-enlarging agent is one or a mixture of benzene, toluene, and mesitylene;

[0009] In the above method, the initiator is one or a mixture of 3-8% by mass of ammonia water, sodium hydroxide, and sodium borohydride;

[0010] In the above method, in the mixed solution, the mass ratio of iridium source, water, EO-PO-EO block copolymer, quaternary ammonium salt surfactant, pore expander, and initiator is 1:100-500:0.5-3:0.1-1:1-50:0.05-0.5;

[0011] In the above method, the raw materials are mixed uniformly by ultrasonication for 5 to 10 minutes or stirring for 20 to 40 minutes;

[0012] In the above method, the reaction temperature is 50-80° C. and the reaction time is 6-10 hours.

[0013] The iridium oxide catalyst with a dendritic pore structure described in the present invention is prepared by the above preparation method.

[0014] The iridium oxide catalyst with dendritic pore structure can be applied in proton exchange membrane water electrolysis technology.

[0015] The iridium oxide catalyst with dendritic pore structure has the advantages that:

[0016] The iridium oxide catalyst with dendritic pore structure has the advantages that: The iridium source and the template agent are fully combined in an aqueous solution by a one-pot method, and a weak base is added as an initiator, so that the iridium oxide catalyst with dendritic pore structure is obtained by simple heating and stirring. The preparation method is simple, easy to operate, safe and green, the precursor iridium source is selected flexibly, and the industrial production is facilitated. The preparation method is simple, easy to operate, safe and green, the precursor iridium source is selected flexibly, and the industrial production is facilitated. The iridium oxide catalyst with dendritic pore structure prepared by the method has more active sites than the commercial iridium oxide catalyst nanoparticles, and the rich pore structure significantly improves the mass transfer capacity of the catalyst, thereby overcoming the diffusion limitation in the non-porous material. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The SEM image of the iridium oxide catalyst with dendritic pore structure prepared in Example 1 of the present application;

[0018] Figure 2 The TEM image of the iridium oxide catalyst with dendritic pore structure prepared in Example 1 of the present application;

[0019] Figure 3 The catalytic performance diagram of the iridium oxide catalyst with dendritic pore structure prepared in Example 1 of the present application for a PEM water electrolysis membrane electrode device;

[0020] Figure 4 The catalytic stability diagram of the iridium oxide catalyst with dendritic pore structure prepared in Example 1 of the present application for a PEM water electrolysis membrane electrode device. DETAILED DESCRIPTION

[0021] The specific embodiments of the present application are described in detail below in combination with the drawings and examples, so that the scheme of the present application and the advantages of each aspect thereof can be better understood.

[0022] It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments. It is obvious that relevant persons can modify or appropriately change and combine the methods and applications described herein to implement and apply the technology of the present invention without departing from the content, spirit, and scope of the present invention.

[0023] The process conditions in the following examples are exemplary only. The acceptable ranges are as described in the preceding Summary of the Invention. For process parameters not otherwise specified, conventional techniques may be used. Unless otherwise noted, the reagents and instruments used in the technical solutions provided herein can be purchased from conventional channels or on the market.

[0024] Example 1

[0025] In this example, iridium oxide catalyst particles with a dendritic pore structure were prepared using the following method: 0.6 g of iridium trichloride was dissolved in 100 mL of water. After the iridium source was dissolved, 0.5 g of the template block copolymer F127 and 0.1 g of hexadecyltrimethylammonium bromide were added. After the template was dissolved, 3 mL of the pore-enlarging agent mesitylene was added. The mixture was ultrasonicated for 5 minutes or stirred for 30 minutes to form a uniform emulsion. The resulting emulsion was then heated and stirred at 70°C, 3 mL of 5% ammonia water was added dropwise, and the mixture was heated and stirred for 8 hours. After the reaction, the solid product was collected and washed three times with a mixture of water and ethanol in a volume ratio of 1:1. After washing away the template, the product was collected and dried at 80°C to obtain iridium oxide catalyst particles with a dendritic pore structure. The product weighed 0.38 g and had an iridium content of 84%. The product was dried and stored at room temperature.

[0026] The synthesized porous iridium oxide catalyst was characterized and tested. Figure 1 This is a scanning electron microscope (SEM) image of the catalyst, from which it can be seen that the catalyst is approximately spherical particles with a particle size of 100 to 300 nm and a large number of mesopores on the surface. Figure 2 This is a transmission electron microscope (TEM) image of an iridium oxide catalyst. In the image, it can be found that the iridium oxide catalyst has a radially open dendritic pore structure. The pores penetrate deep into the interior of the iridium oxide catalyst particles, and the pore diameter is between 10 and 30 nm.

[0027] The prepared porous structure of the iridium oxide catalyst with dendritic pore structure is used in a PEM water electrolysis device as an anode side oxygen evolution reaction catalyst of a membrane electrode, and a commercial platinum carbon catalyst is used as a cathode side hydrogen evolution reaction catalyst. The catalysts on the anode and cathode are sprayed on both sides of the proton exchange membrane by a catalyst coating film preparation method, and the membrane electrode is assembled with a gas diffusion layer, a bipolar plate, a sealing ring, etc. to form a PEM device. The membrane electrode preparation, PEM electrolysis cell assembly and specific test process are as described in the reference (Angew. Chem. Int. Ed. 2024, e202415032.). The test results are as shown in Table 1. Figure 3 When the anode iridium loading is only 0.50 mg cm -2 -2, the catalytic performance at 80℃ can reach 3.82 A cm -2 @2V, indicating that the catalyst has good membrane electrode device performance, and has a catalytic stability of more than 200 h under a large current density of 2 A cm -2 -2. Figure 4

[0028] In summary, the iridium oxide catalyst with dendritic pore structure prepared in this embodiment can be well adapted to an OER catalyst in an acidic environment, and the material exhibits very high catalytic activity and stability in a membrane electrode water electrolysis test, and has great application potential in a PEM water electrolysis device.

[0029] Example 2

[0030] In this embodiment, the iridium source is changed to 0.4 g of potassium iridate, the reaction temperature is changed to 60℃, and the other synthesis conditions remain unchanged. The iridium oxide catalyst with dendritic pore structure is still obtained, the particle diameter is about 100 nm, the pore size is about 20 nm, and when the anode iridium loading is 0.44 mg cm -2 -2, the catalytic performance at 80℃ can reach 3.69 A cm -2 @2V.

[0031] Example 3

[0032] In this embodiment, the initiator is changed to 5 mL of 5% ammonia water, and the other synthesis conditions remain unchanged. The iridium oxide catalyst with dendritic pore structure is still obtained. The particle diameter is about 80 nm, the pore size is about 10 nm, and when the anode iridium loading is 0.51 mg cm -2 -2, the catalytic performance at 80℃ can reach 3.71 A cm -2 @2V.

[0033] Example 4

[0034] ​This example is the same as Example 1, except that the initiator is changed to 0.1g sodium borohydride, the reaction temperature is changed to 60°C, and other synthesis conditions remain unchanged. An iridium oxide catalyst with a dendritic pore structure is still obtained. The particle diameter is about 100nm, the pore size is about 15nm, and the iridium loading at the anode is 0.63mg cm -2 The catalytic performance can reach 3.72 A cm at 80 °C. -2 @2V.

[0035] Example 5

[0036] This example is the same as Example 1, except that the template agent is changed to 1g of block copolymer F127 and 0.2g of hexadecyltrimethylammonium bromide. Other synthesis conditions remain unchanged. An iridium oxide catalyst with a dendritic pore structure is still obtained. The particle diameter is about 100nm, the pore size is about 20nm, and the iridium loading at the anode is 0.52mg cm -2 The catalytic performance can reach 3.70 A cm at 80 °C. -2 @2V.

[0037] Example 6

[0038] This example is the same as Example 1, except that the template agent is replaced with 0.5g of block copolymer P123 and 0.1g of dodecyltrimethylammonium bromide. Other synthesis conditions remain unchanged. Iridium oxide catalysts with dendritic pore structures are still obtained. The particle diameter is about 200nm, the pore size is about 30nm, and the iridium loading at the anode is 0.48mg cm -2 The catalytic performance can reach 3.73Acm at 80℃. -2 @2V.

[0039] Example 7

[0040] This example is the same as Example 1, except that the template agent is changed to 0.5g of block copolymer F127 and 0.1g of hexadecyltrimethylammonium chloride. Other synthesis conditions remain unchanged. An iridium oxide catalyst with a dendritic pore structure is still obtained. The particle diameter is about 150nm, the pore size is about 25nm, and the iridium loading at the anode is 0.55mg cm -2 The catalytic performance can reach 3.80Acm at 80℃ -2 @2V.

[0041] Example 8

[0042] This example is the same as Example 1, except that the template agent is changed to 0.5g of block copolymer F127 and 0.1g of dodecyltrimethylammonium chloride. Other synthesis conditions remain unchanged. An iridium oxide catalyst with a dendritic pore structure is still obtained. The particle diameter is about 150nm, the pore size is about 20nm, and the iridium loading at the anode is 0.43mg cm-2 The catalytic performance can reach 3.77Acm at 80℃ -2 @2V.

[0043] Example 9

[0044] This example is the same as Example 1, except that the template agent is changed to 0.5g of block copolymer F127 and 0.15g of octadecyltrimethylammonium bromide. Other synthesis conditions remain unchanged. An iridium oxide catalyst with a dendritic pore structure is still obtained. The particle diameter is about 200nm, the pore size is about 25nm, and the iridium loading at the anode is 0.56mg cm -2 The catalytic performance can reach 3.72Acm at 80℃. -2 @2V.

[0045] Example 10

[0046] This example is the same as Example 1, except that the pore-enlarging agent is changed to 5 mL of mesitylene. Other synthesis conditions remain unchanged. An iridium oxide catalyst with a dendritic pore structure is still obtained. The particle diameter is about 200 nm, the pore size is about 30 nm, and the iridium loading at the anode is 0.51 mg cm -2 The catalytic performance can reach 3.79Acm at 80℃. -2 @2V.

[0047] Example 11

[0048] This example is the same as Example 1, except that the pore-enlarging agent is 3 mL of benzene. Other synthesis conditions remain unchanged. Iridium oxide catalysts with dendritic pore structures are still obtained. The particle diameter is about 200 nm, the pore size is about 20 nm, and the iridium loading at the anode is 0.47 mg cm -2 The catalytic performance can reach 3.75Acm at 80℃ -2 @2V.

Claims

1. A method for preparing an iridium oxide catalyst having a dendritic pore structure, characterized in that: The method comprises dissolving an iridium source in water, adding a mixed template agent, adding a pore-enlarging agent after dissolution, and mixing uniformly to obtain a uniform emulsion; adding an initiator to carry out a reaction, and after the reaction is completed, centrifuging and washing 3 to 5 times with a mixed solution of water and anhydrous ethanol in a volume ratio of 1:1, washing away the template agent, and drying to obtain the iridium oxide catalyst having a dendritic pore structure; the obtained iridium oxide catalyst has a porous nanosphere or ellipsoid structure with a particle size of 100 to 400 nm; and the iridium oxide catalyst has an open dendritic pore structure with a pore size of 10 to 30 nm. The mixed template agent is a mixture of EO-PO-EO block copolymer and quaternary ammonium salt surfactant, and the EO-PO-EO block copolymer is F127 (EO 106 -PO 70 -EO 106 )、F108(EO 132 -PO 50 -EO 132 )、P123(EO 20 -PO 70 -EO 20 ), the quaternary ammonium surfactant is a mixture of one or more of dodecyltrimethylammonium chloride and dodecyltrimethylammonium bromide; the pore-enlarging agent is a mixture of one or more of benzene, toluene, and mesitylene; the initiator is a mixture of one or more of ammonia water with a mass fraction of 3-8%, sodium hydroxide, and sodium borohydride.

2. The method for preparing an iridium oxide catalyst having a dendritic pore structure according to claim 1, wherein: The iridium source is one of chloroiridic acid, iridium trichloride, iridium tetrachloride, potassium chloroiridate, and sodium chloroiridate, or a mixture of several of them.

3. The method for preparing an iridium oxide catalyst having a dendritic pore structure according to claim 1, wherein: The raw materials are mixed evenly by ultrasonication for 5 to 10 minutes or stirring for 20 to 40 minutes.

4. The method for preparing an iridium oxide catalyst having a dendritic pore structure according to claim 1, wherein: The reaction temperature is 50-80°C, and the reaction time is 6-10 hours.

5. The method for preparing an iridium oxide catalyst having a dendritic pore structure according to claim 1, wherein: The mass ratio of iridium source, water, EO-PO-EO block copolymer, quaternary ammonium salt surfactant, pore expander, and initiator is 1: 100~500: 0.5~3: 0.1~1: 1~50: 0.05~ 0.

5.

6. An iridium oxide catalyst having a dendritic pore structure, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the iridium oxide catalyst having a dendritic pore structure according to claim 6 in proton exchange membrane water electrolysis technology.

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