A binary metal catalyst, its preparation method and application

Abstract

The application relates to a binary metal catalyst, a preparation method and application thereof, and belongs to the technical field of water electrolysis. The preparation method of the binary metal catalyst comprises the following steps: mixing a platinum precursor and a morphology control agent in a first solvent, first dispersing, first heating reaction to make a first metal precursor form a first metal; washing, filtering and drying to obtain first metal nanorods. The first metal nanorods, an iridium precursor and a complexing agent are mixed in a second solvent, second dispersing, adding a pH regulator to adjust to alkaline, dispersing, second heating reaction to make a second metal precursor form a second metal; washing, filtering and drying to obtain a binary metal catalyst with iridium loaded on platinum nanorods, and the average diameter of platinum is 5-7 nm, the aspect ratio is 6-11, the average particle size of iridium is 2-4 nm, and the surface has hydrophilic groups. The catalyst has a lower overpotential and a higher oxygen evolution initial activity.

Description

Technical Field

[0001] This application relates to the field of water electrolysis technology, and more specifically, to a binary metal catalyst, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane water electrolysis (PEMWE) is a green hydrogen production technology with advantages such as fast response speed, compatibility with renewable energy, and low equipment and process operation and maintenance costs. In recent years, it has received widespread attention from academia and industry.

[0003] However, many obstacles still hinder the large-scale mass production of hydrogen through proton exchange membrane water electrolysis. These include high prices of core raw materials and inconsistent mass production quality, imperfect production processes, and a lack of effective process quality control. Therefore, continuous optimization of core raw materials is necessary, such as improving the production process of precious metal catalysts, to enhance initial product performance and durability while reducing material and process costs.

[0004] The oxygen evolution reaction (OER) at the anode of proton exchange membrane water electrolysis is a redox process involving four electron-proton transfers, typically with an overpotential above 300 mV. Currently, iridium and iridium oxide remain the primary OER catalysts in industrial applications. However, Ir is a precious metal with limited global distribution. Therefore, developing a low-cost, low-energy-consumption, stable, and reliable product structure suitable for large-scale production of acidic proton exchange membrane water electrolysis alloy catalysts is urgently needed. Summary of the Invention

[0005] Based on the above-mentioned shortcomings, this application provides a binary metal catalyst, its preparation method and application, in order to partially or completely improve the problems of low catalytic performance and high cost in related technologies.

[0006] This application is implemented as follows:

[0007] In a first aspect, an example of this application provides a binary metal catalyst. The binary metal catalyst comprises platinum and iridium supported on platinum, wherein the average diameter of the platinum is 5-7 nm and the aspect ratio of the platinum is 6-11, the average particle size of the iridium is 2-4 nm, and the surface of the iridium has hydrophilic groups.

[0008] In the above-described process, the binary metal catalyst contains platinum and iridium. Platinum can reduce the amount of the precious metal iridium used without significantly sacrificing the catalyst's conductivity, thus lowering the cost of the binary metal catalyst. Furthermore, in the binary metal catalyst, the average diameter of platinum is 5-7 nm, and its aspect ratio is 6-11. The average particle size of iridium is 2-4 nm. The iridium particles supported on rod-shaped platinum form an ordered core-shell structure, and the surface of the iridium particles has hydrophilic groups, which can reduce the overpotential of the binary metal catalyst and improve its catalytic performance.

[0009] In conjunction with the first aspect, in one possible implementation, the hydrophilic group includes a hydroxyl group.

[0010] In conjunction with the first aspect, in one possible implementation, the molar ratio of iridium to platinum is 1:0.5-1.

[0011] Optionally, the molar ratio of iridium to platinum is 1:0.5-0.6.

[0012] In the above implementation process, the molar ratio of iridium to platinum in the binary metal catalyst is 1:0.5-1, which can reduce the cost of the catalyst without affecting its conductivity and catalytic performance.

[0013] In a second aspect, this application provides a method for preparing a binary metal catalyst, comprising:

[0014] Preparation of the first metal nanorods: The first metal precursor and the morphology control agent are mixed in the first solvent, dispersed for the first time, and heated for the first time to form the first metal from the first metal precursor; the first metal nanorods are obtained by washing, filtering and drying.

[0015] Preparation of binary metal catalyst: A first metal nanorod, a second metal precursor, and a complexing agent are mixed in a second solvent, dispersed for the second time, and a pH adjuster is added to adjust to alkalinity. The mixture is then dispersed again and heated for the second time to form a second metal from the second metal precursor. The mixture is then washed, filtered, and dried to obtain the binary metal catalyst.

[0016] In the above process, the first metal precursor and the morphology control agent are mixed evenly in the first solvent and then heated to obtain the first metal. The morphology control agent can control the morphology of the first metal, so that the first metal formed by the reaction is rod-shaped, and the first metal nanorod with more highly active crystal faces in the exposed state is obtained. After uniformly mixing the first metal nanorod with the second metal precursor and a complexing agent in a second solvent, the pH was adjusted to alkaline, and a heating reduction reaction was carried out to form multiple second metal particles on the surface of the first metal nanorod. Since the first metal nanorod has many exposed highly active crystal faces, the surface crystal structure and atomic state of the second metal can be adjusted through electronic and stress effects during the formation of the second metal particles, thereby improving the catalytic performance of the catalyst. Furthermore, the complexing agent in the mixed system can limit the grain size increase of the second metal during the thermal reduction process, thus improving the catalytic performance of the catalyst. Further, adjusting the pH of the system to alkaline during the reduction of the second metal allows the metal surface to have more hydrophilic groups after reduction, significantly improving the dispersion efficiency of the catalyst in the ionomer slurry system and the storage stability of the slurry. It also reduces the overpotential of the binary metal catalyst, further enhancing its catalytic performance.

[0017] In conjunction with the second aspect, in one possible implementation, the metal element in the first metal precursor is platinum, and the metal element in the second metal precursor is iridium.

[0018] Optionally, the molar ratio of iridium to platinum is 1:0.5-1.

[0019] In the above-described process, the thermal reduction reaction of the platinum precursor is controlled by a morphology control agent to obtain rod-shaped platinum metal. Then, under the regulation of platinum nanorods, a complexing agent, and a pH agent, the iridium metal precursor is thermally reduced. This allows for the control of the iridium metal's morphology, particle size, surface crystal structure, and surface atomic state, resulting in a platinum-iridium binary metal catalyst with high initial oxygen evolution activity and other catalytic properties, which can improve the efficiency of proton exchange membrane water electrolysis.

[0020] In conjunction with the second aspect, in one possible implementation, the first metal precursor is selected from at least one of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, or platinum nitrate.

[0021] The second metal precursor is selected from at least one of chloroiridium acid or iridium acetylacetonate.

[0022] In the above-described process, using first metal precursors such as chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, or platinum nitrate, rod-shaped platinum metal can be obtained during a thermal reduction reaction regulated by a morphology control agent. Using second metal precursors such as chloroiridium acid or iridium acetylacetonate, fine-crystalline iridium metal loaded onto platinum nanorods can be obtained during a thermal reduction reaction regulated by platinum nanorods, a complexing agent, and a pH agent.

[0023] In conjunction with the second aspect, in one possible implementation, the morphology control agent is selected from at least one of potassium iodide, potassium bromide, benzoic acid, hexadecyltrimethylammonium bromide, or dopamine.

[0024] The complexing agent is selected from at least one of polyvinylpyrrolidone, citric acid, sodium citrate, or ascorbic acid.

[0025] Both the first solvent and the second solvent are independently selected from at least one of formaldehyde, ethylene glycol, or glycerol.

[0026] The pH adjuster is selected from at least one of sodium hydroxide, ammonium bicarbonate, or potassium hydroxide.

[0027] Optionally, the molar ratio of the first metal precursor to the morphology control agent is 2-5:1.

[0028] Optionally, the molar ratio of the second metal precursor to the complexing agent is 1-3:1.

[0029] Optionally, in the preparation step of the binary metal catalyst, a pH adjuster is added to adjust the pH to 9-11.

[0030] In the above-mentioned process, morphology control agents such as potassium iodide, potassium bromide, benzoic acid, hexadecyltrimethylammonium bromide, or dopamine are used in the thermal reaction of the platinum precursor to control the morphology of the platinum metal obtained by thermal reduction to be rod-shaped, giving the platinum nanorods more active crystal faces in the exposed state. By using complexing agents such as polyvinylpyrrolidone, citric acid, sodium citrate, or ascorbic acid to participate in the thermal reduction reaction of the iridium precursor with platinum nanorods and pH adjusters such as sodium hydroxide, ammonium bicarbonate, or potassium hydroxide, the morphology, surface crystal structure, and surface atomic state of the iridium metal can be controlled, resulting in a platinum-iridium binary metal catalyst with high initial oxygen evolution activity.

[0031] In conjunction with the second aspect, in one possible implementation, the temperature of the first heating reaction is 90-110°C; the temperature of the second heating reaction is 150-170°C.

[0032] Optionally, the first heating reaction and / or the second heating reaction may be carried out using microwave reaction, with a power of 1000-5000W.

[0033] Optionally, the temperature of the first heating reaction is 95-105℃.

[0034] Optionally, the temperature of the first heating reaction is 105°C.

[0035] Optionally, the temperature for the second heating reaction is 155-165℃.

[0036] Optionally, the temperature for the second heating reaction is 165°C.

[0037] In the above-mentioned process, a thermal reduction reaction of the platinum precursor was carried out using a microwave reaction with a power of 1000-5000W at a temperature of 90-110℃, which yielded platinum nanorods with a high aspect ratio rod-like structure. A first heating reaction at 105℃ further improved the aspect ratio of the platinum nanorods, thereby enhancing the catalytic activity of the subsequently obtained catalyst.

[0038] Microwave reaction with a power of 1000-5000W and thermal reduction of iridium precursor at 150-170℃ can yield iridium metal with a smaller particle size, further improving the catalytic performance of the catalyst. A second heating reaction at 165℃ can further reduce the particle size of the iridium metal and enhance the catalyst's catalytic activity.

[0039] In conjunction with the second aspect, in one possible implementation, the first dispersion method includes a first shear dispersion, wherein the first shear rate is 200-600 rpm and the first shear duration is 10-60 min.

[0040] The second dispersion method includes a second shear dispersion, with a second shear rate of 400-1000 rpm and a second shear duration of 10-60 min.

[0041] Optionally, the first shearing speed is 400-600 rpm and the first shearing duration is 40-60 min.

[0042] Optionally, the second shearing speed is 600-800 rpm, and the second shearing time is 30-50 min.

[0043] In the above-described process, shearing and dispersing the mixture of platinum precursor and morphology control agent in the first solvent at a shear rate of 200-600 rpm for 10-60 min can improve the aspect ratio of the platinum nanorods obtained by the thermal reduction reaction. Shearing at a shear rate of 400-600 rpm for 40-60 min can further improve the aspect ratio of the platinum nanorods and enhance the catalytic activity of the catalyst subsequently prepared.

[0044] Shearing and dispersing a mixture of platinum nanorods, iridium precursor, and complexing agent in a second solvent at a shear rate of 400-1000 rpm for 10-60 min can reduce the particle size of iridium metal obtained by thermal reduction reaction.

[0045] In a third aspect, examples of this application provide the application of a binary metal catalyst in proton exchange membrane electrolysis of water.

[0046] Optionally, a binary metal catalyst can be used to catalyze the oxygen evolution reaction at the anode of a proton exchange membrane water electrolysis.

[0047] In the above implementation process, the oxygen evolution reaction at the anode of the proton exchange membrane water electrolysis is catalyzed by the binary metal catalyst provided in the first aspect of this application, which can improve the efficiency of proton exchange membrane water electrolysis. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0049] Figure 1 A schematic diagram of the preparation process of the binary metal catalyst provided as an example in this application;

[0050] Figure 2 This is a SEM image of the binary metal catalyst provided in Example 1 of this application;

[0051] Figure 3 This is a TEM image of the binary metal catalyst provided in Example 1 of this application at a lower magnification.

[0052] Figure 4 This is a TEM image of the binary metal catalyst provided in Example 1 of this application at a higher TEM value. Detailed Implementation

[0053] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0054] Proton exchange membrane electrolysis, as a green hydrogen production technology with advantages such as fast response speed, compatibility with renewable energy, and low equipment and process operation and maintenance costs, has received widespread attention from academia and industry in recent years.

[0055] The oxygen evolution reaction at the anode of proton exchange membrane (PEM) water electrolysis is a redox process involving the transfer of four electrons to protons, typically with an overpotential above 300mV. Currently, iridium and iridium oxide remain the primary OER catalysts in industry, but the distribution of Ir precious metals on Earth is limited. High prices of core raw materials, unstable mass production quality, and imperfect production processes are obstacles hindering the large-scale mass production of hydrogen through PEM water electrolysis. Therefore, continuous optimization of core raw materials is necessary, such as improving the production process of precious metal catalysts, to enhance initial product performance and durability while reducing material and process costs.

[0056] To reduce the loading of precious metals, the inventors attempted to use Ir-Pt binary alloys as catalysts. However, the catalytic performance of Ir-Pt binary alloy catalysts was relatively low. Therefore, the inventors controlled the morphology of the Ir-Pt binary alloy to improve its catalytic performance, thereby reducing the cost of the Ir-Pt binary alloy catalyst while simultaneously enhancing its catalytic performance.

[0057] Therefore, this application provides a binary metal catalyst and its preparation method to improve the problems of poor catalytic performance and high cost of catalysts.

[0058] Please see Figure 1 The preparation methods of binary metal catalysts include:

[0059] S1. Preparation of the first metal nanorod:

[0060] The first metal precursor and the morphology control agent are mixed in the first solvent, dispersed for the first time, and heated for the first time to form the first metal; the first metal precursor is washed, filtered and dried to obtain the first metal nanorods.

[0061] By using morphology control agents in the thermal reduction reaction of the first metal precursor, rod-shaped first metal nanorods can be obtained, which have more exposed highly active crystal faces. This allows the first metal nanorods with more exposed highly active crystal faces to be used to control the morphology, surface crystal structure, and surface atomic state of the second metal, thereby obtaining a binary metal catalyst with high catalytic activity.

[0062] In one possible embodiment, the first metal nanorod may be a platinum nanorod. It is understood that a nanorod refers to a rod-shaped structure with an aspect ratio greater than 1.

[0063] Furthermore, the first metal precursor for forming platinum nanorods through thermal reduction can be at least one of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, or platinum nitrate.

[0064] For example, the first metal precursor may be selected from chloroplatinic acid.

[0065] The morphology control agent may be selected from at least one of potassium iodide, potassium bromide, benzoic acid, hexadecyltrimethylammonium bromide, or dopamine.

[0066] For example, the morphology control agent may be selected from potassium iodide.

[0067] In one possible embodiment, the molar ratio of the first metal precursor to the morphology control agent can be 2-5:1.

[0068] For example, the molar ratio of the first metal precursor to the morphology control agent can be one of 2:1, 3:1, 4:1 or 5:1 or any range between two of them.

[0069] In one possible embodiment, the first solvent may be selected from at least one of formaldehyde, ethylene glycol, or glycerol.

[0070] For example, the first solvent may be selected from ethylene glycol.

[0071] Furthermore, the method of mixing the first metal precursor and the morphology control agent in ethylene glycol may include: mixing an ethylene glycol solution of the first metal precursor with an ethylene glycol solution of the morphology control agent.

[0072] Before the thermal reduction reaction, the mixed solution of the first metal precursor and the morphology control agent in the first solvent is first dispersed to form a solution to be reduced in which the first metal precursor and the morphology control agent are uniformly dispersed. This can improve the aspect ratio of the reduced product and obtain the first metal nanorod with a rod-like structure.

[0073] This application does not limit the specific dispersion process. In one possible embodiment, the mixed solution of the first metal precursor and the morphology control agent in the first solvent may be subjected to a first shear dispersion.

[0074] In one possible embodiment, the first shear dispersion is performed at a first speed of 200-600 rpm and the first shear duration is 10-60 min.

[0075] For example, the first shear dispersion speed can be one of 200 rpm, 300 rpm, 400 rpm, 500 rpm or 600 rpm or any range between two of them.

[0076] For example, the first time of the first shear dispersion can be one of 10 min, 20 min, 30 min, 40 min, 50 min or 60 min or any range between two of them.

[0077] Furthermore, a first speed of 400-600 rpm and a first shearing time of 40-60 min can further improve the aspect ratio of the first metal nanorods obtained after the thermal reduction reaction.

[0078] For example, the first shearing speed is 400 rpm and the first shearing time is 60 min.

[0079] For example, the first shearing speed is 600 rpm and the first shearing time is 40 min.

[0080] The temperature of the thermal reduction reaction, controlled by morphology control agents, affects the morphology of the reduction products. To further improve the aspect ratio of platinum nanorods, in one possible implementation, the temperature of the first heating reaction can be 90-110℃.

[0081] For example, the temperature of the first heating reaction can be one of 90°C, 95°C, 100°C, 105°C or 110°C or any combination thereof.

[0082] To further improve the aspect ratio of platinum nanorods, in one possible embodiment, the temperature of the first heating reaction can be 105°C.

[0083] Furthermore, in one possible implementation, the heating rate of the first heating reaction can be 1-10 °C / min.

[0084] For example, the heating rate of the first heating reaction can be 5°C / min.

[0085] Furthermore, the first heating reaction can be carried out via microwave reaction.

[0086] For example, the power of the microwave reaction is 1000-1500W.

[0087] For example, the power of the microwave reaction is one or more of 1000W, 1100W, 1200W, 1300W, 1400W or 1500W or any two of them.

[0088] Furthermore, after the thermal reduction reaction, the solution can be cooled to room temperature and washed with deionized water until the conductivity of the washing solution is less than 5 μS / cm. Then, it is centrifuged to separate the metal precipitate and dried under vacuum to obtain platinum nanorods.

[0089] Platinum nanorods obtained through step S1 provided in this application can yield platinum metal rods with an aspect ratio of 6-11 and an average diameter of 5-7 nm.

[0090] For further information, please refer to [link / reference]. Figure 1The preparation method of the binary metal catalyst provided in this application further includes:

[0091] S2, Preparation of binary metal catalysts:

[0092] The first metal nanorod, the second metal precursor, and the complexing agent were mixed in a second solvent and dispersed for the second time. A pH adjuster was added to adjust the pH to alkaline, and the mixture was dispersed again. A second heating reaction was carried out to form the second metal from the second metal precursor. The mixture was then washed, filtered, and dried to obtain the binary metal catalyst.

[0093] The first metal nanorods with more exposed highly active crystal faces obtained in step S1 are combined with complexing agents and pH adjusters and participate in the thermal reduction reaction of the second metal precursor. The complexing agent can be used to restrict the grains of the second metal, the first metal nanorods can be used to adjust the surface crystal structure and surface atomic state of the second metal, and the pH adjuster can be used to make the reduced metal surface have more hydrophilic groups, thereby improving the catalytic performance of the catalyst.

[0094] For example, the structure of the second metal can be rutile. In one possible embodiment, the second metal can be iridium.

[0095] Furthermore, the second metallic precursor for forming metallic iridium through thermal reduction can be selected from at least one of chloroiridium acid or iridium acetylacetonate.

[0096] For example, the second metal precursor may be selected from chloroiridium acid.

[0097] The complexing agent may be selected from at least one of polyvinylpyrrolidone, citric acid, sodium citrate or ascorbic acid.

[0098] For example, the complexing agent may be selected from polyvinylpyrrolidone.

[0099] Furthermore, the molar ratio of the second metal precursor to the complexing agent can be 1-3:1.

[0100] For example, the molar ratio of the second metal precursor to the complexing agent can be one of 1:1, 1.5:1, 2:1, 2.5:1 or 3:1 or any range between two of them.

[0101] Furthermore, the molar ratio of the second metal element in the second metal precursor to the first metal element in the first metal nanorod can be 1:0.5-1.

[0102] For example, the molar ratio of the second metal element to the first metal element can be one of 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1 or any range between two of them.

[0103] For example, the first metallic element is platinum, and the second metallic element is iridium. The molar ratio of iridium to platinum is 1:0.6.

[0104] In one possible embodiment, the second solvent is selected from at least one of formaldehyde, ethylene glycol, or glycerol.

[0105] For example, the second solvent is selected from ethylene glycol.

[0106] Furthermore, the method of mixing the first metal nanorod, the second metal precursor, and the complexing agent in ethylene glycol may include: mixing an ethylene glycol solution of the first metal nanorod and the second metal precursor, and mixing an ethylene glycol solution of the complexing agent.

[0107] The method for dispersing a mixed solution of a first metal nanorod, a second metal precursor, and a complexing agent in a second solvent includes a second shear dispersion.

[0108] For example, the second shearing rate of the second shearing dispersion is 400-1000 rpm, and the second shearing duration is 10-60 min.

[0109] Furthermore, the second shearing speed can be 600-800 rpm, and the second shearing time can be 30-50 min.

[0110] For example, the second shearing speed can be 600 rpm and the second shearing time can be 50 min.

[0111] For example, the second shearing speed can be 800 rpm and the second shearing time can be 30 min.

[0112] After the second shear dispersion, a pH adjuster is added to the uniformly dispersed mixture to adjust the system to alkalinity.

[0113] In one possible embodiment, the pH of the system can be adjusted to 9-11 using a pH adjuster such as sodium hydroxide, ammonium bicarbonate, or potassium hydroxide.

[0114] For example, potassium hydroxide can be used to adjust the pH of the system to 10.

[0115] In one possible embodiment, the temperature for thermal reduction of the iridium precursor can be adjusted to 150-170°C.

[0116] To further reduce the particle size of iridium metal particles, in one possible embodiment, the temperature for thermal reduction of the iridium metal precursor can be adjusted to 155-165°C.

[0117] For example, the temperature at which the iridium metal precursor is thermally reduced is 165°C.

[0118] Furthermore, the iridium metal precursor can be thermally reduced using a microwave reaction.

[0119] In one possible embodiment, the microwave power for microwave reaction of the iridium precursor can be 1000-5000W.

[0120] For example, the microwave power for microwave reaction of iridium precursor can be one of 1000W, 2000W, 3000W, 4000W or 5000W or any combination thereof.

[0121] Furthermore, after the thermal reduction reaction of the iridium metal precursor, the reaction solution can be cooled to room temperature and washed with deionized water until the conductivity of the washing solution is less than 5 μS / cm. Then, the solution is centrifuged to separate the metal precipitate and dried under vacuum to obtain a binary metal catalyst.

[0122] Using the preparation method provided in this application, a binary metal catalyst in which iridium metal particles are supported on platinum nanorods can be obtained, wherein the aspect ratio of the platinum nanorods is 6-11 and the average diameter is 5-7 nm, the average particle size of the iridium metal particles is 2-4 nm, and the surface of the iridium particles has hydrophilic groups.

[0123] For example, the hydrophilic group may include oxygen-containing functional groups such as hydroxyl or carboxyl groups.

[0124] Using the preparation method provided in this application, the morphology of platinum nanorods is first controlled by a morphology modifier, and then the grain size, surface crystal structure and surface atomic state of iridium metal particles are adjusted by combining a complexing agent and a pH adjuster with the platinum nanorods. The catalytic performance of the binary metal catalyst obtained by the reaction can be improved by adding the morphology modifier, complexing agent and pH adjuster step by step.

[0125] Furthermore, this application example also provides an application of a binary metal catalyst in proton exchange membrane water electrolysis.

[0126] For example, a binary metal catalyst is used to catalyze the oxygen evolution reaction at the anode of a proton exchange membrane water electrolysis.

[0127] The binary metal catalyst of this application will be further described in detail below with reference to the embodiments.

[0128] Example 1

[0129] An example provides a binary metal catalyst, the preparation method of which is as follows:

[0130] (1): Weigh 120 mL of 0.1 mol / L chloroplatinic acid in ethylene glycol solution and 70 mL of 0.5 mol / L potassium iodide in ethylene glycol solution, mix and disperse by shearing. The first shearing speed is 600 rpm and the first shearing time is 60 min. Place the dispersed solution in a microwave reactor, set the microwave power to 1500 W, heat from room temperature to the first reaction temperature of 105 °C at a heating rate of 5 °C / min, and continue the reaction for 5 min to obtain the first solution.

[0131] (2): After the first solution obtained in step (1) is cooled to room temperature, it is washed with deionized water until the conductivity of the washing solution is less than 5 μS / cm. Then, it is centrifuged and the black precipitate is separated. The platinum nanorods are obtained by drying under vacuum.

[0132] (3): The platinum nanorods obtained in step (2), 25 mL of ethylene glycol solution of 0.8 mol / L acetylacetone iridium, and 18 mL of ethylene glycol solution of 0.5 mol / L polyvinylpyrrolidone were mixed and sheared and dispersed. The second shearing speed was 800 rpm and the second shearing time was 50 min. Then, a pH adjuster was added to adjust the pH of the system to 10 and shearing and dispersion continued. The dispersed solution was placed in a microwave reactor, the microwave power was set to 2100 W, and the solution was heated from room temperature to the second reaction temperature of 165 °C. After reacting for 10 min, the second solution was obtained.

[0133] (4): After the second solution obtained in step (3) is cooled to room temperature, it is washed with deionized water until the conductivity of the washing solution is less than 5 μS / cm. Then, it is centrifuged to separate the black precipitate and dried under vacuum to obtain the binary metal catalyst.

[0134] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 1.

[0135] Example 2

[0136] The difference between Example 2 and Example 1 is that in step (1), the first shearing speed is 400 rpm and the first shearing time is 60 min.

[0137] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 2.

[0138] Example 3

[0139] The difference between Example 3 and Example 1 is that in step (1), the first shearing speed is 600 rpm and the first shearing time is 40 min.

[0140] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 3.

[0141] Example 4

[0142] The difference between Example 4 and Example 1 is that in step (1), the first reaction temperature is 95°C.

[0143] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 4.

[0144] Example 5

[0145] The difference between Example 5 and Example 1 is that in step (3), the second shearing speed is 600 rpm and the second shearing time is 50 min.

[0146] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 5.

[0147] Example 6

[0148] The difference between Example 6 and Example 1 is that in step (3), the second shearing speed is 800 rpm and the second shearing time is 30 min.

[0149] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 6.

[0150] Example 7

[0151] The difference between Example 7 and Example 1 is that in step (3), the second reaction temperature is 155°C.

[0152] Please refer to Table 1 for the shear dispersion parameters and reaction temperature of Example 7.

[0153] Table 1

[0154]

[0155] Comparative Example 1

[0156] The difference between Comparative Example 1 and Example 1 is that no morphology control agent was added in step (1).

[0157] Comparative Example 2

[0158] The difference between Comparative Example 2 and Example 1 is that no complexing agent was added in step (3).

[0159] Comparative Example 3

[0160] The difference between Comparative Example 3 and Example 1 is that no pH adjuster was added in step (3).

[0161] Comparative Example 4

[0162] The difference between Comparative Example 4 and Example 1 lies in the preparation method: 120 mL of a 0.1 mol / L ethylene glycol solution of chloroplatinic acid, 70 mL of a 0.5 mol / L ethylene glycol solution of potassium iodide, 25 mL of a 0.8 mol / L ethylene glycol solution of iridium acetylacetonate, and 18 mL of a 0.5 mol / L ethylene glycol solution of polyvinylpyrrolidone were weighed, mixed, and sheared and dispersed at 800 rpm for 50 min. A pH adjuster was then added to adjust the pH to 10, and shearing and dispersion continued. The dispersed solution was placed in a microwave reactor, and the microwave power was set to 2100 W. The solution was heated from room temperature to 165°C and reacted for 10 min to obtain the reaction solution. After cooling the reaction solution to room temperature, it was washed with deionized water, centrifuged, and the black precipitate was separated. The precipitate was then dried under vacuum to obtain the binary metal catalyst.

[0163] Test case

[0164] The catalyst prepared in Example 1 was subjected to SEM and TEM morphology analysis. Figure 2 The image shows a SEM image of the catalyst provided in Example 1. Figure 2 and Figure 3 The image shows a TEM image of the binary metal catalyst provided in Example 1.

[0165] The grain size and aspect ratio of platinum nanorods in the catalysts provided in Examples 1-7 and Comparative Examples 1-4 were statistically analyzed, as were the grain size of iridium metal particles. The statistical results are shown in Table 2.

[0166] The catalysts provided in Examples 1-7 and Comparative Examples 1-4 were subjected to overpotential tests under the following conditions:

[0167] Half-cell electrode preparation:

[0168] (1): According to the solution volume ratio V IPA V H2O V Nafion Prepare 11 parts of ionomer dispersion with a ratio of 4:1:0.016;

[0169] (2): Take 5 mg of the catalyst from Examples 1-7 and Comparative Examples 1-4 respectively, add them to 5 mL of the ionomer dispersion obtained in step (1), sonicate for 10 min, and form 11 test solutions;

[0170] (3): 10 μL of the test solution obtained in step (2) was dropped onto the gold electrode and tested in a 0.5 M H2 SO4 solution saturated with N2 after drying.

[0171] Overpotential test:

[0172] Linear sweep voltammetry (LSV) was performed with a scan range of 1.2–1.6 V vs RHE (0.544–0.944 V vs Hg₂SO₄), a scan rate of 10 mV / s, and a rotating disk electrode speed of 2000 rpm. The comparison was 10 mA / cm. 2 Potential at the location.

[0173] Table 2

[0174]

[0175]

[0176] Results analysis:

[0177] Combination Figures 2-4 As shown in Table 2, the binary metal catalyst provided in this application example has a regular core-shell structure and exhibits superior initial oxygen evolution activity.

[0178] As can be seen from Example 1 and Comparative Example 1, without the addition of a morphology control agent, Pt nanocrystals lose their nanorod morphology and revert to a spherical morphology with an average particle size of 8.2 nm. Due to the reduced proportion of highly active crystal faces exposed, the influence on the electronic structure of the metal Ir surface during the formation of a binary metal catalyst is reduced, which in turn leads to a decrease in the initial activity of oxygen evolution.

[0179] As can be seen from Example 1 and Comparative Example 2, in the absence of a complexing agent, the particle size of Ir metal loses its confinement during the thermal reduction process, and the average particle size increases by about 39%, which will cause the overpotential to be too high and the initial activity of oxygen evolution to decrease.

[0180] As can be seen from Example 1 and Comparative Example 3, if a pH adjuster is not added during the reduction of metallic Ir, problems such as poor product dispersibility and easy sedimentation will occur during the slurry preparation process, resulting in excessively high overpotential and reduced initial activity of oxygen evolution.

[0181] As can be seen from Example 1 and Comparative Example 4, the binary metal catalyst with an ordered core-shell structure obtained by stepwise preparation of the present application, which uses a morphology control agent to regulate the morphology of platinum metal and then combines it with a complexing agent and a pH adjuster to participate in the thermal reduction formation process of iridium metal, has a lower overpotential and higher initial oxygen evolution activity compared with the catalyst obtained by mixing all raw materials together and then carrying out a thermal reduction reaction in Comparative Example 4.

[0182] Combining Examples 1 and 2, it can be seen that the binary metal catalyst obtained in Example 1, which is sheared and dispersed at a first shear rate of 600 rpm / min for 60 min, has a lower overpotential compared to the binary metal catalyst obtained in Example 2, which is sheared and dispersed at a first shear rate of 400 rpm / min for 60 min.

[0183] Combining Examples 5 and 7, it can be seen that the binary metal catalyst obtained in Example 5 by shearing and dispersing at a second shear rate of 600 rpm / min for 50 min has a lower overpotential than the binary metal catalyst obtained in Example 7 by shearing and dispersing at a second shear rate of 800 rpm / min for 50 min.

[0184] Combining Examples 1 and 4, it can be seen that the temperature of the first heating reaction affects the morphology of platinum nanocrystals. When the reduction endpoint temperature is reduced by 10°C, the diameter of the platinum nanorods increases by 26%, the aspect ratio decreases by 32%, and the corresponding electrochemical performance decreases by 16%.

[0185] Combining Examples 1 and 7, it can be seen that the temperature of the second heating reaction affects the particle size of iridium nanocrystals. When the reduction endpoint temperature is reduced by 10°C, the average particle size of Ir decreases by 16%, and the corresponding electrochemical performance decreases by 19%.

[0186] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a binary metal catalyst, characterized in that, include: Preparation of the first metal nanorod: The first metal precursor and the morphology control agent are mixed in the first solvent, dispersed for the first time, and heated for the first time to form the first metal from the first metal precursor; The first metal nanorods are obtained by washing, filtering, and drying; the metal element in the first metal precursor is platinum, and the first metal precursor is selected from at least one of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, or platinum nitrate; the morphology control agent is selected from at least one of potassium iodide or potassium bromide; the temperature of the first heating reaction is 90-110℃; the first dispersion method includes a first shear dispersion, the first shear rate is 200-600 rpm, and the first shear duration is 10-60 min; Preparation of binary metal catalyst: The first metal nanorod, the second metal precursor and the complexing agent are mixed in the second solvent, dispersed for the second time, and the pH adjuster is added to adjust to alkalinity. The mixture is then dispersed again and heated for the second time to form the second metal from the second metal precursor. The binary metal catalyst is obtained by washing, filtering, and drying. The metal element in the second metal precursor is iridium, and the second metal precursor is selected from at least one of chloroiridium acid or iridium acetylacetonate; the complexing agent is selected from polyvinylpyrrolidone; the temperature of the second heating reaction is 150-170℃; the second dispersion method includes a second shear dispersion, the second shear rate is 400-1000 rpm, and the second shear duration is 10-60 min; the molar ratio of iridium to platinum is 1:0.5-1.

2. The preparation method according to claim 1, characterized in that, Both the first solvent and the second solvent are independently selected from at least one of ethylene glycol or glycerol; The pH adjuster is selected from at least one of sodium hydroxide, ammonium bicarbonate, or potassium hydroxide.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the second metal precursor to the complexing agent is 1-3:1; and / or, in the preparation step of the binary metal catalyst, the pH adjuster is added to adjust the pH to 9-11.

4. The preparation method according to claim 2, characterized in that, The first heating reaction and / or the second heating reaction are carried out using microwave reactions, with a microwave reaction power of 1000-5000W. And / or, the temperature of the first heating reaction is 95-105°C; And / or, the temperature of the second heating reaction is 155-165°C.

5. The preparation method according to claim 4, characterized in that, The temperature of the first heating reaction is 105°C; and / or the temperature of the second heating reaction is 165°C.

6. The preparation method according to claim 2, characterized in that, The first shearing speed is 400-600 rpm, and the first shearing time is 40-60 min; And / or, the second shearing speed is 600-800 rpm, and the second shearing duration is 30-50 min.

7. A binary metal catalyst, characterized in that, The binary metal catalyst is prepared according to any one of claims 1 to 6; the binary metal catalyst comprises platinum and iridium supported on the platinum, wherein the average diameter of the platinum is 5-7 nm, the aspect ratio of the platinum is 6-11, the average particle size of the iridium is 2-4 nm, and the surface of the iridium has hydrophilic groups.

8. The binary metal catalyst according to claim 7, characterized in that, The hydrophilic group includes hydroxyl groups.

9. The binary metal catalyst according to claim 7, characterized in that, The molar ratio of iridium to platinum is 1:0.5-1; Alternatively, the molar ratio of iridium to platinum is 1:0.5-0.

6.

10. An application of the binary metal catalyst according to any one of claims 7-9 in proton exchange membrane electrolysis of water.

11. The application according to claim 10, characterized in that, The binary metal catalyst is used to catalyze the oxygen evolution reaction at the anode of the proton exchange membrane water electrolysis.

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