In-situ supported iridium-based catalysts, methods for their preparation and use

Abstract

The application provides an in-situ supported iridium-based catalyst, a preparation method and application thereof, and belongs to the technical field of chemical industry. The supported catalyst is obtained by in-situ loading of an iridium source and a carrier precursor promoted by a polymer cationic surfactant. The preparation method of the supported catalyst comprises the following steps: mixing alcohol, deionized water, an additive, a carrier precursor and an iridium source to obtain a first solution; adding sodium nitrate to the first solution to obtain a second solution; ultrasonic dispersing the second solution and then evaporating under stirring to obtain a solid mixture; and calcining the solid mixture in a muffle furnace to obtain the supported iridium-based catalyst. The in-situ supported iridium-based catalyst has the advantages of good iridium loading uniformity, high catalytic activity, good durability and easy adjustment of loading, and can be used in the field of water electrolysis hydrogen production. Compared with the existing PEM water electrolysis hydrogen production technology, the preparation method provided by the application has the advantages of mild conditions, simple operation and easy industrialization.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis catalyst technology, specifically to a class of in-situ supported iridium-based catalysts, their preparation methods, and applications. Background Technology

[0002] Proton exchange membrane (PEM) water electrolysis for hydrogen production is considered an important route for green hydrogen production due to its high efficiency, fast response, and high hydrogen purity. The core of this technology lies in the oxygen evolution reaction (OER) occurring at the anode. This reaction is kineticly slow and requires a highly efficient and stable electrocatalyst to drive it. Iridium and its oxides are currently the most promising anode OER catalysts due to their excellent activity and relative stability in strongly acidic environments. However, iridium resources are extremely scarce and expensive, which severely restricts the large-scale commercial application of PEM electrolyzers.

[0003] To maximize the utilization of the precious metal iridium and improve its catalytic efficiency, it is essential to load iridium nanoparticles onto a conductive support in a highly dispersed, uniform, and robust manner to form a supported catalyst. Traditional methods for preparing supported iridium catalysts (such as impregnation and deposition-precipitation methods) often face numerous challenges: iridium species are prone to migration and aggregation on the support surface, leading to a reduction in active sites and uneven particle size; the loading process has poor controllability, making it difficult to precisely control the loading amount and particle distribution; and some methods involve cumbersome steps and demanding conditions (such as high temperature and high pressure), which are not conducive to large-scale production.

[0004] Therefore, developing a novel preparation strategy that can achieve highly uniform dispersion of iridium species, strong interfacial bonding, and easily controllable loading under mild conditions is crucial for reducing catalyst costs and improving the performance and lifespan of PEM in water electrolysis. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a type of in-situ supported iridium-based catalyst, which exhibits good loading uniformity, high catalytic activity, excellent durability, and easily adjustable loading.

[0006] To achieve the above objectives, this invention introduces pyridine salt polymers as additives. Utilizing their unique cationic adsorption, steric hindrance, coordination enhancement, and in-situ promotion functions, iridium sources and carrier precursors are loaded in situ, effectively overcoming the shortcomings of traditional methods such as easy agglomeration of iridium particles, uneven loading, weak interfacial bonding, and complex and demanding processes.

[0007] Another objective of this invention is to provide a method for preparing an in-situ supported iridium-based catalyst, thereby solving the problems of complex preparation methods, low iridium atom utilization, low catalytic efficiency, and poor durability of existing PEM water electrolysis iridium-based catalysts.

[0008] The present invention provides a method for preparing an in-situ supported iridium-based catalyst, comprising the following steps: S1. Isopropanol, deionized water, additives, carrier precursor and iridium source are mixed to obtain the first solution; S2 Add sodium nitrate to the first solution to obtain the second solution; S3 After ultrasonically dispersing the second solution, it is evaporated to dryness under stirring to obtain a solid mixture; S4 The solid mixture is calcined in a muffle furnace, cooled, and then washed with deionized water to obtain the final product.

[0009] According to an embodiment of the present invention, the additive in step S1 is a polymeric cationic surfactant P3-CCR-H of pyridinium tetrafluoroborate salt, with the following structure:

[0010] Wherein, n is 30 to 50, preferably 40 to 45.

[0011] According to an embodiment of the present invention, the carrier precursor in step S1 is tetrabutyl titanate, tetrabutyl silicate, tetrabutyl stannate, or tetrabutyl germanate; preferably, the carrier precursor is tetrabutyl titanate.

[0012] According to an embodiment of the present invention, the iridium source in step S1 is chloroiridium hexahydrate, potassium chloroiridate, or sodium chloroiridate; preferably, the iridium source is chloroiridium hexahydrate.

[0013] According to an embodiment of the present invention, the volume ratio of deionized water to isopropanol in step S1 is 1:5 to 1:15.

[0014] According to an embodiment of the present invention, the molar ratio of deionized water to carrier precursor in step S1 is 40:1 to 120:1.

[0015] According to an embodiment of the present invention, the mass ratio of deionized water to additive in step S1 is 40:1 to 10:1.

[0016] According to an embodiment of the present invention, the molar ratio of the iridium source to the carrier precursor in step S1 is 1:5 to 1:1.

[0017] According to an embodiment of the present invention, the mass ratio of the additive to the iridium source in step S1 is 1:3 to 1:15.

[0018] According to an embodiment of the present invention, the molar ratio of sodium nitrate in step S2 to iridium source in step S1 is 20:1 to 60:1.

[0019] According to an embodiment of the present invention, the ultrasonic dispersion time in step S3 is 30-60 min, and the evaporation temperature is 70-100℃.

[0020] According to an embodiment of the present invention, the calcination temperature in step S4 is 300-500°C, and the calcination time is 0.5-3 hours.

[0021] Another object of the present invention is to provide the application of the above-mentioned in-situ supported iridium-based catalyst in the field of PEM water electrolysis for hydrogen production.

[0022] 1) This invention introduces a pyridine salt polymer cationic surfactant as an additive. The pyridine salt polymer cationic additive has unique structural advantages: cationic characteristics: its positively charged pyridinium groups can effectively adsorb negatively charged iridium precursor species (such as chloroiridate ions) through electrostatic interaction, guiding the uniform anchoring of iridium species on the support surface; polymer chain structure: the polymer chain provides steric hindrance effect, effectively inhibiting the migration and aggregation of iridium species in subsequent processing, ensuring the formation of small and uniformly distributed nanoparticles; multifunctional coordination sites: the nitrogen atom on the pyridine ring may serve as a coordination site, enhancing the interaction with iridium species, optimizing the interfacial electronic structure, and improving the structural stability (durability) of the catalyst under harsh OER conditions; in-situ loading promoter: this additive can play a role in the initial stage of blending the iridium source and the support precursor (such as titanium sol), promoting the uniform mixing and interaction of the two, achieving true "in-situ" loading, thereby significantly improving the atomic utilization and catalytic efficiency of iridium; 2) The supported iridium-based catalyst of the present invention has mild preparation conditions and simple operation, providing key material support for promoting high-performance and low-cost PEM water electrolysis hydrogen production technology. Attached Figure Description

[0023] Figure 1 Transmission electron microscopy (TEM) image of the in-situ supported iridium-based catalyst prepared in Example 4 of this invention.

[0024] Figure 2 The polarization curves are those of the in-situ supported iridium-based catalysts and comparative catalysts prepared in Examples 1-4 of this invention.

[0025] Figure 3 Durability test curves of the in-situ supported iridium-based catalysts and comparative catalysts prepared in Examples 1-4 of this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example 1

[0027] S1. Mix 24 mL isopropanol, 4 mL deionized water, 103 mg additive P3-CCR-H, 340 mg tetrabutyl titanate (1 mmol), and 515 mg chloroiridium hexahydrate (1 mmol) to obtain the first solution. S2 Add 2g of sodium nitrate to the first solution to obtain the second solution; S3 After ultrasonically dispersing the second solution for 40 min, it was stirred and evaporated to dryness at 90 °C to obtain a solid mixture; S4 The above solid mixture was placed in a muffle furnace and calcined at 350°C for 1 hour. After cooling, it was washed with deionized water to obtain an in-situ supported iridium-based catalyst IrO2·TiO2 with an Ir:Ti molar ratio of 1:1. Example 2

[0028] S1. Mix 26 mL isopropanol, 2 mL deionized water, 83 mg additive P3-CCR-H, 640 mg tetrabutyl silicate (2 mmol), and 515 mg chloroiridium hexahydrate (1 mmol) to obtain the first solution. S2 Add 3g of sodium nitrate to the first solution above to obtain the second solution; S3 After ultrasonically dispersing the second solution for 35 minutes, it was stirred and evaporated to dryness at 70°C to obtain a solid mixture; S4 The above solid mixture was placed in a muffle furnace and calcined at 400°C for 0.5 h. After cooling, it was washed with deionized water to obtain an in-situ supported iridium-based catalyst IrO2·SiO2 with an Ir:Si molar ratio of 1:2. Example 3

[0029] S1. Mix 25 mL isopropanol, 3 mL deionized water, 166 mg additive P3-CCR-H, 1.02 g tetrabutyl titanate (3 mmol), and 483 mg potassium chloroiridate (1 mmol) to obtain the first solution. S2 Add 4g of sodium nitrate to the first solution above to obtain the second solution; S3 After ultrasonically dispersing the above second solution for 50 min, it is stirred and evaporated to dryness at 80 °C to obtain a solid mixture; S4 The above solid mixture was placed in a muffle furnace and calcined at 300°C for 2 hours. After cooling, it was washed with deionized water to obtain an in-situ supported iridium-based catalyst IrO2·TiO2 with an Ir:Ti molar ratio of 1:3. Example 4

[0030] S1. Mix 23 mL isopropanol, 5 mL deionized water, 142 mg additive P3-CCR-H, 680 mg tetrabutyl titanate (2 mmol), and 515 mg chloroiridium hexahydrate (1 mmol) to obtain the first solution. S2 Add 2.5g of sodium nitrate to the first solution to obtain the second solution; S3 After ultrasonically dispersing the second solution for 40 min, it was stirred and evaporated to dryness at 100℃ to obtain a solid mixture; S4 The above solid mixture was placed in a muffle furnace and calcined at 450°C for 1.5 h. After cooling, it was washed with deionized water to obtain an in-situ supported iridium-based catalyst IrO2·TiO2 with an Ir:Ti molar ratio of 1:2. From Figure 1 It can be seen that the iridium-based catalyst is uniformly distributed on the surface of the support without obvious agglomeration.

[0031] The commercial iridium oxide catalyst used in this comparative example is IrO2 produced by Anhui Masu New Energy Technology Co., Ltd.

[0032] The supported iridium-based catalysts in Examples 1-4 or the commercial iridium oxide catalysts in the comparative examples were prepared into membrane electrodes, which were then assembled into a single proton exchange membrane electrolyzer, and their polarization curves and durability were tested.

[0033] Membrane electrode fabrication: Anode slurry preparation: 100 mg of the catalyst from the example or comparative example, 4 mL of deionized water, 18 mL of isopropanol, and 2 mL of 5 wt% Nafion (D520) solution are homogenized and mixed to obtain the anode slurry.

[0034] Cathode slurry preparation: 76 mg platinum / carbon catalyst (CAS Innovation), 4 mL deionized water, 18 mL isopropanol, and 2 mL 5 wt% Nafion solution were homogenized and mixed to obtain cathode slurry.

[0035] Then, using ultrasonic spraying equipment, the above-mentioned cathode slurry and anode slurry are sprayed onto both sides of the Nafion proton exchange membrane, with a catalyst layer area of ​​25 cm². 2 The catalyst loading was quantitatively controlled at 0.26 mg / cm³ at the cathode. 2 Anode 0.34 mg / cm 2 .

[0036] The membrane electrode assembly was used to form a single proton exchange membrane electrolyzer. Toray carbon paper was used as the porous diffusion layer at the cathode, and platinum-coated porous titanium was used as the anode. During the test, the pure water flow rate was 100 ml / min, the water temperature was controlled at 60℃, and the stability test was conducted using a constant current method.

[0037] from Figure 2 It can be seen that the initial performance of Example 4 is significantly better than that of the comparative example, and the voltage rise rate of the comparative example is significantly higher than that of Example 4 as the current density increases. Therefore, Example 4 exhibits superior OER activity compared to the comparative example. Furthermore, from... Figure 2 It is also known that, under the same current density, the catalyst performance of Example 2 of the present invention is the lowest, indicating that in this invention, silicon dioxide is not a preferred support for iridium-based catalysts.

[0038] from Figure 3 It can be observed that within 1200 minutes of the accelerated stability test, the voltage rise rate of the comparative example is significantly higher than that of the embodiment of the present invention, indicating that the introduction of pyridine salt polymer cationic additive in the present invention can effectively promote the in-situ loading of iridium-based catalyst on the support surface and has a significant improvement effect on catalyst stability.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a type of in-situ supported iridium-based catalyst, characterized in that, The preparation method of the in-situ supported iridium-based catalyst includes the following steps: S1. Mix isopropanol, deionized water, additives, carrier precursor and iridium source to obtain the first solution; S2. Add sodium nitrate to the first solution to obtain a second solution; S3. After ultrasonically dispersing the second solution, evaporate it to dryness under stirring to obtain a solid mixture; S4. The solid mixture is calcined in a muffle furnace, cooled, and then washed with deionized water to obtain the final product.

2. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, The additive mentioned in step S1 is a polymeric cationic surfactant P3-CCR-H of pyridinium tetrafluoroborate salt, the structure of which is shown in Formula I: ; Where n is a number between 30 and 50, preferably between 40 and 45.

3. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, In step S1, the carrier precursor is any one of tetrabutyl titanate, tetrabutyl silicate, tetrabutyl stannate, or tetrabutyl germanate. Preferably, the carrier precursor is tetrabutyl titanate.

4. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, In step S1, the iridium source is any one of chloroiridium hexahydrate, potassium chloroiridate, or sodium chloroiridate. Preferably, the iridium source is chloroiridium hexahydrate.

5. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, In step S1, the volume ratio of water to isopropanol is 1:5 to 1:15; the molar ratio of water to the carrier precursor is 40:1 to 120:1; the mass ratio of water to the additive is 40:1 to 10:1; the molar ratio of the iridium source to the carrier precursor is 1:5 to 1:1; and the mass ratio of the additive to the iridium source is 1:3 to 1:

15.

6. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, The molar ratio of sodium nitrate added in step S2 to the iridium source in step S1 is 20:1 to 60:

1.

7. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, In step S3, the ultrasonic dispersion time is 30-60 min, and the stirring and evaporation temperature is 70-100℃.

8. The method for preparing an in-situ supported iridium-based catalyst according to claim 1, characterized in that, In step S4, the calcination temperature in the muffle furnace is 300~500℃, and the calcination time is 0.5~3 hours.

9. A type of in-situ supported iridium-based catalyst, characterized in that, The in-situ supported iridium-based catalyst is prepared by the method for preparing the in-situ supported iridium-based catalyst according to any one of claims 1 to 8.

10. The application of the in-situ supported iridium-based catalyst according to claim 9, characterized in that, Application in anode catalysts for hydrogen production via water electrolysis.

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