Preparation method of IrRu alloy catalyst

Abstract

The present invention belongs to the technical field of catalysts, and discloses a method for preparing an IrRu alloy. An iridium precursor salt, a ruthenium precursor salt and a dispersant are added to water to obtain an iridium-ruthenium mixed salt solution; a low boiling point solvent is added to the iridium-ruthenium mixed salt solution, and after uniform mixing, a quaternary ammonium salt is added as a reducing agent to obtain a mixed material; the mixed material is subjected to a reflux reaction at 80-140°C, and after the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product; the reaction product is subjected to solid-liquid separation, and the solid phase is washed and dried to obtain an IrRu alloy. In the present invention, the quaternary ammonium salt is used as a reducing agent, and is matched with a low boiling point solvent to achieve efficient reduction of iridium-ruthenium ions under relatively low temperature conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a method for preparing an IrRu alloy catalyst. Background Art

[0002] Proton exchange membrane (PEM) water electrolysis hydrogen production technology is currently generally considered to have the most promising development prospects in the field of hydrogen energy because of its advantages such as high energy conversion efficiency, small electrolyzer volume, high purity of hydrogen produced, and fast startup. However, PEM water electrolysis is generally a strongly acidic environment, which has high requirements for materials, especially the slow kinetics of the anode oxygen evolution reaction (OER), which places higher requirements on OER catalysts. To date, iridium-based catalysts with both high activity and high stability are still the most widely used OER catalysts in commercial applications in PEM water electrolysis, but their high material cost and complex preparation process have hindered the rapid development of PEM water electrolysis hydrogen production technology. Therefore, significantly reducing the iridium load and maintaining the high efficiency and stability of the catalyst are prerequisites for the rapid and large-scale industrialization of PEM water electrolysis hydrogen production technology.

[0003] In order to reduce the amount of iridium while maintaining the efficiency and stability of the catalyst during use, the most reported method is to add ruthenium metal, which is cheaper than iridium, to form a binary alloy. The methods for preparing iridium-ruthenium-based catalysts in the prior art mainly include chemical precipitation method, polyol method, and sodium borohydride reduction method. x The oxide particles are relatively large, with different morphologies and low catalytic activity. Since ruthenium ions are difficult to reduce, the polyol method uses high-boiling-point solvents and needs to be carried out at high temperatures (up to 200°C), resulting in long reaction times and low yields. In addition, polyols serve as both solvents and reducing agents, and are difficult to recover and separate during the reaction. They are also used in large quantities, which is not conducive to large-scale industrial production. The IrRu alloy particles obtained by sodium borohydride reduction grow randomly and have an extremely low yield. In addition, sodium borohydride is expensive and is an explosive reagent, which is not conducive to industrial production. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an IrRu alloy used as an anode catalyst for PEM water electrolysis to produce hydrogen, so as to achieve Ru reduction at a relatively low temperature, and the obtained catalyst has a high yield and a relatively high catalytic activity.

[0005] To achieve the above objectives, the present invention adopts the following specific technical solutions.

[0006] A method for preparing an IrRu alloy comprises the following steps:

[0007] Step S1, adding an iridium precursor salt, a ruthenium precursor salt and a dispersant into water to obtain an iridium-ruthenium mixed salt solution;

[0008] Step S2, adding a low boiling point solvent to the iridium-ruthenium mixed salt solution, mixing evenly, and then adding a quaternary ammonium salt as a reducing agent to obtain a mixed material;

[0009] Step S3, the mixed material is subjected to reflux reaction at 80-140° C., and after the reaction is completed, it is cooled to room temperature to obtain a reaction product;

[0010] Step S4, separating the reaction product into solid and liquid, washing and drying the solid phase to obtain an IrRu alloy.

[0011] Furthermore, as a preferred embodiment, the iridium precursor salt is chloroiridic acid or iridium chloride, and the ruthenium precursor salt is ruthenium chloride or ruthenium acetylacetonate.

[0012] Furthermore, as a preferred embodiment, the mass ratio of iridium to ruthenium in the iridium-ruthenium mixed salt solution is 3:(1-2).

[0013] Furthermore, as a preferred embodiment, the dispersant is at least one of sodium pyrophosphate, potassium pyrophosphate, ammonium citrate, sodium citrate and urea.

[0014] Furthermore, as a preferred embodiment, the amount of the dispersant added is 1 to 3 times the total mass of the iridium precursor salt and the ruthenium precursor salt.

[0015] Furthermore, as a preferred embodiment, the low boiling point solvent is a solvent with a boiling point lower than 100° C., and is further selected from at least one of ethanol, isopropanol, sec-butanol, and n-propanol.

[0016] Furthermore, as a preferred embodiment, the amount of the low boiling point solvent added is: 1 L of the low boiling point solvent is added for every 0.4-2 g of the iridium precursor salt and the ruthenium precursor.

[0017] Furthermore, as a preferred embodiment, the quaternary ammonium salt is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and behenyldimethylammonium bromide.

[0018] Furthermore, as a preferred embodiment, the ratio of the added mass of the reducing agent to the sum of the masses of the iridium precursor salt and the ruthenium precursor salt is 1:4 to 5:4.

[0019] Furthermore, as a preferred embodiment, the reflux reaction time is 0.2 to 5 hours.

[0020] Generally speaking, quaternary ammonium salt compounds such as hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride are used as surfactants in the synthesis reaction of catalysts to inhibit crystal growth and control particle size. In the present invention, quaternary ammonium salts are used as reducing agents and are combined with low boiling point solvents to achieve efficient reduction of iridium and ruthenium ions under relatively low temperature conditions. The present invention utilizes low boiling point (boiling point less than 100°C) solvents, which, in addition to having the function of the solvent itself, can also enhance the reducing ability of quaternary ammonium salts.

[0021] Compared with the prior art, the present invention has the following obvious beneficial technical effects:

[0022] The preparation method provided by the present invention has mild conditions, a simple process, and low requirements on equipment. The low-boiling-point solvent is only used as a solvent. The impurity content in the solvent after the reaction is low, and the solvent can be recycled and reused. The energy consumption is low, the cost is saved, and the method is suitable for large-scale batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the IrRu alloy catalyst obtained in Example 1, wherein the magnification of Figure (a) is 30k, and the magnification of Figure (b) is 100k.

[0024] Figure 2 The IrRu alloy catalysts obtained in Examples 1-4 and Comparative Examples, commercial IrO 2 Linear sweep voltammetry curves of the catalyst, where (a) is the area activity curve and (b) is the mass activity curve.

[0025] Figure 3 The IrRu alloy catalyst obtained in Example 1 and the commercial IrO 2 Chronopotentiometry curves of the catalysts. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0029] First, a method for preparing an IrRu alloy is provided, which can achieve Ru reduction at a relatively low temperature, and the obtained catalyst has a high yield, a small particle size, a uniform distribution, and a relatively high catalytic activity. The preparation method comprises the following steps:

[0030] Step S1, adding an iridium precursor salt, a ruthenium precursor salt and a dispersant into water to obtain an iridium-ruthenium mixed salt solution;

[0031] Step S2, adding a low boiling point solvent to the iridium-ruthenium mixed salt solution, mixing evenly, and then adding a quaternary ammonium salt as a reducing agent to obtain a mixed material;

[0032] Step S3, the mixed material is subjected to reflux reaction at 80-140° C., and after the reaction is completed, it is cooled to room temperature to obtain a reaction product;

[0033] Step S4, separating the reaction product into solid and liquid, washing and drying the solid phase to obtain an IrRu alloy.

[0034] In some preferred embodiments, the iridium precursor salt is chloroiridic acid or iridium chloride, and the ruthenium precursor salt is ruthenium chloride or ruthenium acetylacetonate. The mass ratio of iridium to ruthenium in the iridium-ruthenium mixed salt solution is 3:(1-2).

[0035] In some preferred embodiments, the dispersant is at least one of sodium pyrophosphate, potassium pyrophosphate, ammonium citrate, sodium citrate, and urea. Further, the amount of the dispersant added is 1 to 3 times the total mass of the iridium precursor salt and the ruthenium precursor salt.

[0036] Adding an appropriate amount of dispersant can inhibit agglomeration.

[0037] In some preferred embodiments, the low boiling point solvent is a solvent having a boiling point below 100° C., and is further selected from at least one of ethanol, isopropanol, sec-butanol, and n-propanol.

[0038] As described in the background technology, since ruthenium ions are difficult to be reduced, the use of high boiling point solvents such as polyols requires the reaction to be carried out at high temperatures, and the reaction time is long, the yield is low, and the polyol is both a solvent and a reducing agent, and it is difficult to be recycled after the reaction is completed. The use of low-boiling point monohydric alcohol as a solvent is essentially a solvent, but it can enhance the reducing ability of quaternary ammonium salts, and achieve the simultaneous reduction of iridium and ruthenium at a relatively low temperature to obtain an IrRu alloy.

[0039] Ethanol, isopropanol, sec-butanol and n-propanol are commonly used monohydric alcohol solvents with boiling points below 100°C. They are relatively cheap and suitable for industrial production.

[0040] In some preferred embodiments, the amount of the low boiling point solvent added is: 1 L of the low boiling point solvent is added for every 0.4-2 g of the iridium precursor salt and the ruthenium precursor.

[0041] In some preferred embodiments, the quaternary ammonium salt is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and behenyldimethylammonium bromide.

[0042] In some preferred embodiments, the ratio of the added mass of the reducing agent to the sum of the masses of the iridium precursor salt and the ruthenium precursor salt is 1:4 to 5:4.

[0043] In some preferred embodiments, the reflux reaction time is 0.2 to 5 hours.

[0044] The technical solution of the present invention is further described below through specific embodiments.

[0045] Example 1

[0046] (1) 30 mg IrCl 3 and 10 mg RuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0047] (2) Weigh 50 mg of sodium pyrophosphate and add it to the material obtained in step (1), and disperse it by ultrasonic at room temperature for 0.5 h;

[0048] (3) Add 50 mL of ethanol to the material obtained in step (2) and disperse by ultrasonic at room temperature for 0.5 h;

[0049] (4) Add 25 mg of hexadecyltrimethylammonium chloride to the solution obtained in step (3), and disperse by ultrasonic at room temperature for 0.5 h;

[0050] (5) The solution obtained in step (4) was transferred into a 100°C oil bath for reflux reaction for 1 h, and then cooled to room temperature;

[0051] (6) The mixture obtained in step (5) is filtered, washed with water, and dried in a vacuum oven at 60° C. to obtain the target product.

[0052] Figure 1 This is a SEM image of the target product obtained in Example 1, from which it can be seen that it is composed of uniformly dispersed nanoparticles.

[0053] Comparative Example 1

[0054] (1) 30 mg IrCl 3 and 10 mgRuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0055] (2) Weigh 50 mg of sodium pyrophosphate and add it to the material obtained in step (1), and disperse it by ultrasonic at room temperature for 0.5 h;

[0056] (3) Add 50 mL of ethylene glycol to the material obtained in step (2) and disperse by ultrasonication at room temperature for 0.5 h;

[0057] (4) Add 25 mg of hexadecyltrimethylammonium chloride to the solution obtained in step (3), and disperse by ultrasonic at room temperature for 0.5 h;

[0058] (5) The solution obtained in step (4) was transferred into a 100°C oil bath for reflux reaction for 1 h, and then cooled to room temperature;

[0059] (6) The mixture obtained in step (5) is filtered, washed with water, and dried in a vacuum oven at 60° C. to obtain the target product.

[0060] Comparative Example 2

[0061] (1) 30 mg IrCl 3 and 10 mgRuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0062] (2) Weigh 50 mg Na 4 P 2 O 7 Add to the material obtained in step (1), and disperse by ultrasonic at room temperature for 0.5 h;

[0063] (3) Add 50 mL of ethylene glycol to the material obtained in step (2) and disperse by ultrasonication at room temperature for 0.5 h;

[0064] (4) The solution obtained in step (3) was transferred into a 195°C oil bath and refluxed for 15 h, and then cooled to room temperature;

[0065] (5) The mixture obtained in step (4) was filtered, but no product was collected, and the color of the filtered solution was still the color of the metal ions.

[0066] Comparative Example 3

[0067] (1) 30 mg IrCl 3 and 10 mgRuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0068] (2) Weigh 50 mg of sodium pyrophosphate and add it to step (1), and disperse it by ultrasonic at room temperature for 0.5 h;

[0069] (3) Add 50 mL of ethanol to step (2) and disperse by ultrasonic at room temperature for 0.5 h;

[0070] (4) The solution obtained in step (3) was transferred into a 100°C oil bath for reflux reaction for 1 h, and then cooled to room temperature;

[0071] (5) The mixture obtained in step (4) was filtered, but no product was collected, and the color of the filtered solution was still the color of the metal ions.

[0072] Comparative Example 4

[0073] (1) 30 mg IrCl 3 and 10 mgRuCl 3 Dissolve in 51 mL of water and disperse by ultrasonic at room temperature for 0.5 h;

[0074] (2) Weigh 50 mg of sodium pyrophosphate and add it to the material obtained in step (1), and disperse it by ultrasonic at room temperature for 0.5 h;

[0075] (3) Add 25 mg of hexadecyltrimethylammonium chloride to the solution obtained in step (2) and disperse by ultrasonic at room temperature for 0.5 h;

[0076] (4) The solution obtained in step (3) was transferred into a 100°C oil bath for reflux reaction for 1 h, and then cooled to room temperature;

[0077] (5) The mixture obtained in step (4) was filtered, but no product was collected, and the color of the filtered solution was still the color of the metal ions.

[0078] Example 2

[0079] (1) Add 45 mg IrCl 3 and 30 mgRuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0080] (2) Weigh 100 mg of ammonium citrate and add it to step (1), and disperse it by ultrasonic at room temperature for 1.0 h;

[0081] (3) Add 50 mL of isopropanol to step (2) and disperse by ultrasonic at room temperature for 0.5 h;

[0082] (4) adding 25 mg of hexadecyltrimethylammonium bromide to the solution obtained in step (3), and dispersing by ultrasonication at room temperature for 1.0 h;

[0083] (5) The solution obtained in step (4) was transferred into an 80°C oil bath and refluxed for 1 h, and then cooled to room temperature;

[0084] (6) The mixture obtained in step (5) is filtered, washed with water, and dried in a vacuum oven at 60° C. to obtain the target product.

[0085] Example 3

[0086] (1) 30 mg IrCl 3and 15 mgRuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0087] (2) Weigh 50 mg of potassium pyrophosphate and add it to step (1), and disperse it by ultrasonic at room temperature for 0.5 h;

[0088] (3) Add 50 mL of n-propanol to step (2) and disperse by ultrasonic at room temperature for 0.5 h;

[0089] (4) Add 25 mg of dimethylbenzene ammonium bromide to the solution obtained in step (3), and disperse by ultrasonication at room temperature for 0.5 h;

[0090] (5) The solution obtained in step (4) was transferred into a 140°C oil bath for reflux reaction for 1 h, and then cooled to room temperature;

[0091] (6) The mixture obtained in step (5) is filtered, washed with water, and dried in a vacuum oven at 60° C. to obtain the target product.

[0092] Example 4

[0093] (1) 30 mg IrCl 3 and 15 mgRuCl 3 Dissolve in 1 mL of water and disperse by ultrasound at room temperature for 0.5 h;

[0094] (2) Weigh 50 mg of urea and add it to step (1), and disperse it by ultrasonic at room temperature for 0.5 h;

[0095] (3) Add 50 mL of sec-butyl alcohol to step (2) and disperse by ultrasonic at room temperature for 0.5 h;

[0096] (4) Add 25 mg of hexadecyltrimethylammonium chloride to the solution obtained in step (3), and disperse by ultrasonic at room temperature for 0.5 h;

[0097] (5) The solution obtained in step (4) was transferred into a 120°C oil bath for reflux reaction for 1 h, and then cooled to room temperature;

[0098] (6) The mixture obtained in step (5) is filtered, washed with water, and dried in a vacuum oven at 60° C. to obtain the target product.

[0099] The products obtained in Examples 1-4 and Comparative Example 1 and commercial IrO 2 Catalyst (from Suzhou Shengernuo Technology Co., Ltd.) was added at 0.5 mol·L -1 Linear sweep voltammetry was performed in sulfuric acid solution. Figure 2 As shown. Figure 2(a) It can be seen that the catalyst synthesized in the low boiling point solvent system has a high current density of 10 mA cm -2 It has a lower overpotential, much lower than that of ethylene glycol system and commercial IrO 2 catalyst; Figure 2 (b) The mass activity diagram shows that the low-boiling point solvent system has high activity at a low iridium content, which greatly enhances the utilization rate of iridium and is beneficial to cost saving.

[0100] Examples 1-4, Comparative Examples 1-4 and commercial IrO 2 The relevant parameters of the catalyst are listed below.

[0101] Table 1

[0102]

[0103] The catalyst prepared using low-boiling monohydric alcohol as solvent has a much higher yield than the system using ethylene glycol as solvent, has a higher yield, and is suitable for large-scale production; in the traditional experiment of using polyhydric alcohol to reduce IrRu ions (Comparative Example 2), no product is generated even under high energy consumption, indicating that ethylene glycol alone as a reducing agent cannot reduce IrRu ions; no product is generated in Comparative Example 3 without adding quaternary ammonium salt. Different from the catalyst synthesis system reported in the prior art, in which hexadecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride is only used as a surfactant, the present invention shows that quaternary ammonium salts such as hexadecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride, and dimethyldimethylammonium bromide have strong reducing properties, and can be used in combination with low-boiling monohydric alcohol to achieve efficient reduction of IrRu ions at lower energy consumption. In addition, the catalyst prepared by the present invention has a catalytic performance far greater than that of commercial IrO with a higher Ir loading even at a lower Ir loading. 2 catalyst.

[0104] Figure 3 The IrRu alloy catalyst prepared in Example 1 of the present invention and the commercial IrO 2 The catalyst was 0.5 mol·L -1 10 mA cm in sulfuric acid solution -2 Chronopotentiometry curves under current density. It can be seen that commercial IrO 2 The voltage of the catalyst began to jump after 90 minutes of constant current electrolysis, indicating that it had failed. However, the voltage of the IrRu alloy catalyst synthesized by the present invention was still lower than 1.6V after 600 minutes, showing better stability.

[0105] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an IrRu alloy, characterized in that: The following steps are involved: Step S1, adding an iridium precursor salt, a ruthenium precursor salt and a dispersant into water to obtain an iridium-ruthenium mixed salt solution; the iridium precursor salt is chloroiridic acid or iridium chloride, the ruthenium precursor salt is ruthenium chloride or ruthenium acetylacetonate; the dispersant is at least one of sodium pyrophosphate, potassium pyrophosphate, ammonium citrate, sodium citrate and urea; Step S2, adding a low boiling point solvent to the iridium ruthenium mixed salt solution, mixing evenly, and then adding a quaternary ammonium salt as a reducing agent to obtain a mixed material; the low boiling point solvent is selected from at least one of ethanol, isopropanol, sec-butanol, and n-propanol; the quaternary ammonium salt is at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and behenyldimethylammonium bromide; The ratio of the added mass of the reducing agent to the sum of the masses of the iridium precursor salt and the ruthenium precursor salt is 1:4 to 5:4; Step S3, the mixed material is subjected to reflux reaction at 80-140° C., and after the reaction is completed, it is cooled to room temperature to obtain a reaction product; Step S4, separating the reaction product into solid and liquid, washing and drying the solid phase to obtain an IrRu alloy.

2. The preparation method according to claim 1, characterized in that The mass ratio of iridium to ruthenium in the iridium-ruthenium mixed salt solution is 3:1-2.

3. The preparation method according to claim 1 or 2, characterized in that: The added amount of the dispersant is 1 to 3 times the total mass of the iridium precursor salt and the ruthenium precursor salt.

4. The preparation method according to claim 1, characterized in that: The amount of the low boiling point solvent added is: 1 L of the low boiling point solvent is added for every 0.4-2 g of the iridium precursor salt and the ruthenium precursor.

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