A supported iridium oxide-based catalyst, its preparation method and use

Abstract

The application belongs to the technical field of electrocatalytic materials, and discloses a supported iridium oxide-based catalyst and a preparation method and application thereof. The application provides a preparation method for in-situ carrier production and loading of a supported iridium oxide-based catalyst. A carrier raw material which can be thermally decomposed below 400 DEG C is directly mixed with an iridium raw material in a medium such as sodium nitrate, and a nano-sized oxide carrier is generated in-situ through calcination. The supported iridium oxide-based catalyst IrO2 is uniformly distributed on the surface of a CeO2, TiO2 or ZrO2 carrier in the form of nanoparticles, and the interface is firmly combined, thereby significantly improving the utilization rate of the noble metal iridium and exhibiting excellent catalytic activity and stability in the anode oxygen evolution reaction of proton exchange membrane water electrolysis.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials technology, specifically relating to a supported iridium oxide-based catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean alternative energy source, is of great significance in solving the global energy crisis and environmental problems. Water electrolysis is the core pathway for hydrogen production. Among various water electrolysis hydrogen production systems, PEM (Proton Exchange Membrane) has significant advantages. It uses pure water as raw material, eliminating the corrosion and pollution problems associated with alkaline electrolytes in traditional water electrolysis systems. The obtained hydrogen, after dehydration and deoxygenation, achieves a purity of over 99.999%. Furthermore, the low gas permeability of the proton exchange membrane minimizes the risk of hydrogen-oxygen cross-permeation, resulting in high system safety. Its electrode structure, closely attached to both sides of the membrane, provides very low inter-electrode resistance, allowing for electrolysis voltages as low as 1.6 V or even below. It can operate stably at high current densities, achieving an energy efficiency of 65%-80%, significantly superior to alkaline water electrolysis. It consumes less electricity for the same hydrogen production, reducing electricity costs over the long term.

[0003] The anodic oxygen release reaction in PEM hydrogen production requires a highly efficient catalyst to reduce the overpotential. Since the anode catalyst layer generates a large number of hydrogen ions during operation, resulting in a surface pH value <3, a catalyst with high catalytic activity and acid resistance is often required. Among them, IrO2 or composite catalysts containing iridium oxide have become the preferred anode catalysts for PEM water electrolysis due to their excellent stability and catalytic activity. However, iridium resources are scarce and expensive. The industry hopes to load it on a carrier without catalytic activity to reduce its usage and thus lower costs.

[0004] The preparation of existing supported IrO2 catalysts requires the purchase of expensive nano-sized CeO2 / TiO2 / ZrO2 supports. However, the nano-support particles that are actually purchased often have severe agglomeration, and the secondary particles are far from meeting the actual requirements. The support and IrO2 raw materials can only be mechanically mixed, resulting in poor loading uniformity and weak bonding. This increases costs and limits the improvement of catalytic performance, making it difficult to meet the needs of large-scale commercial applications. Summary of the Invention

[0005] The purpose of this invention is to provide a supported iridium oxide-based catalyst and its preparation method. The catalyst uses oxides such as cerium oxide, titanium oxide, or zirconium oxide as supports to support iridium oxide in situ. It has the advantages of controllable iridium oxide loading, high loading uniformity, strong bonding, high utilization rate of precious metal iridium, simple preparation process, and low cost. It is suitable for the oxygen evolution reaction at the anode of proton exchange membrane water electrolysis and can exhibit excellent catalytic activity and long-term stability in acidic media.

[0006] Another objective of this invention is to provide an application of a supported iridium oxide-based catalyst.

[0007] This invention provides a method for preparing a supported iridium oxide-based catalyst, the method comprising the following steps:

[0008] 1) The carrier raw material, dispersion medium and iridium raw material are mixed to obtain a precursor mixture;

[0009] 2) The precursor mixture is calcined, and after cleaning and drying, the supported iridium oxide-based catalyst is obtained.

[0010] In step 1), the carrier raw material is one or more of cerium nitrate, cerium ammonium nitrate, titanium oxysulfate, zirconium nitrate, or zirconium oxynitrate.

[0011] In step 1), the dispersion medium is one or more of sodium nitrate or potassium nitrate.

[0012] In step 1), the iridium raw material is one or more of iridium chloride or chloroiridium acid.

[0013] In step 1), the mass ratio of the carrier raw material, dispersion medium and iridium raw material in the precursor mixture is 1:1~100:0.2~2.

[0014] In step 2), the calcination temperature is 330~550℃, the calcination time is 5~300min, and the gas atmosphere is air.

[0015] Preferably, in step 2), after cleaning and drying, a calcination process is added. After the calcination process is completed, the supported iridium oxide-based catalyst is obtained by grinding. The calcination temperature of the calcination process is 350-600 ℃, the calcination time is 10-120 min, and the gas atmosphere is air. The calcination process enhances the bonding strength between IrO2 and the support and improves the stability of the catalyst crystal structure.

[0016] This invention provides a supported iridium oxide-based catalyst prepared using the above-described preparation method.

[0017] This invention provides an application of a supported iridium oxide-based catalyst as a catalyst for the anode of a proton exchange membrane water electrolysis.

[0018] The present invention provides a membrane electrode, which is prepared using the supported iridium oxide-based catalyst described in the present invention as the active material.

[0019] The supported iridium oxide-based catalyst of the present invention is obtained by adding a support material to a dispersion medium such as sodium nitrate, so that the support material is thermally decomposed simultaneously or before the iridium material to form a nanoscale support, so that iridium oxide is loaded in situ on the surface of cerium oxide, titanium oxide or zirconium oxide. By mixing the support and the load material in the raw material, a strongly bonded and uniformly distributed supported iridium oxide-based catalyst is obtained.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. It realizes an integrated process of in-situ carrier formation and in-situ IrO2 loading, eliminating the need to purchase expensive nano-scale CeO2, TiO2 or ZrO2 carriers, thus significantly reducing raw material costs;

[0022] 2. The carrier material is mixed with iridium material and calcined at low temperature to obtain IrO2 uniformly loaded on the surface of the nanoscale carrier, with high loading uniformity and high IrO2 particle dispersion;

[0023] 3. Effectively improves the utilization rate of the precious metal iridium, and effectively reduces the amount of iridium used while achieving better performance than commercial products;

[0024] 4. The prepared supported iridium oxide-based catalyst exhibits excellent performance in the oxygen evolution reaction at the anodic end of proton exchange membrane water electrolysis, at 60℃ and 1 A / cm². 2 The initial voltage is below 1.72 V at the current density. Attached Figure Description

[0025] Figure 1 The images show the TEM, HAADF, and mapping of the CeO2@IrO2 catalyst in Example 2. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0028] Example 1

[0029] A supported iridium oxide-based catalyst, the specific steps of which are as follows:

[0030] 1) Take 10.0 g sodium nitrate, 1.0 g titanium oxysulfate and 0.85 g iridium chloride and mix them evenly. Add 5 mL of water and grind them into a slurry. Then dry them in an oven at 80 °C for 24 hours. Grind the dried product to form a precursor mixture.

[0031] 2) The precursor mixture was heated to 400 °C in an air atmosphere in a muffle furnace and held for 30 min. It was washed three times with deionized water, ground and dried to obtain the supported iridium oxide-based catalyst, labeled as TiO2@IrO2.

[0032] Example 2

[0033] A supported iridium oxide-based catalyst, the specific steps of which are as follows:

[0034] 1) Take 17.0 g sodium nitrate, 2.0 g cerium nitrate and 1.60 g chloroiridic acid, mix them evenly, add 5 mL of water and grind them into a slurry, then dry them in an oven at 80 ℃ for 24 hours. After grinding the dried product, a precursor mixture is formed.

[0035] 2) The precursor mixture was heated to 400 °C in a muffle furnace under air atmosphere and held for 40 min. After cleaning and drying, it was calcined in air atmosphere at 410 °C for 20 min and then ground to obtain the supported iridium oxide-based catalyst, labeled CeO2@IrO2.

[0036] Example 3

[0037] A supported iridium oxide-based catalyst, the specific steps of which are as follows:

[0038] The preparation method of this embodiment differs from that of Example 1 only in that in step 1), 10.0 g sodium nitrate, 1.0 g titanium oxysulfate and 0.85 g iridium chloride are replaced with 80 g sodium nitrate, 15 g zirconium nitrate and 12 g iridium chloride, and in step 2), the mixture is heated to 360°C and held for 35 min. The resulting product is labeled as ZrO2@IrO2.

[0039] Example 4

[0040] A supported iridium oxide-based catalyst, the specific steps of which are as follows:

[0041] The difference between the preparation method of this embodiment and that of Example 1 is that in step 1), 10.0 g sodium nitrate, 1.0 g titanium oxysulfate and 0.85 g iridium chloride are changed to 12 g sodium nitrate, 1 g titanium oxysulfate, 1 g cerium nitrate and 1.75 g iridium chloride, and the holding time in step 2) is changed to 25 min; the resulting product is labeled as CeO2-TiO2@IrO2.

[0042] Comparative Example 1

[0043] A supported iridium oxide-based catalyst, the specific steps of which are as follows:

[0044] The only difference between this comparative example and Example 1 is that titanium oxysulfate in step 1) is replaced with cerium dioxide; the rest of the preparation methods are the same.

[0045] Comparative Example 2

[0046] An iridium oxide-based catalyst, the specific steps of which are as follows:

[0047] The only difference between this comparative example and Example 1 is that titanium oxysulfate was not added in step 1), while the rest of the preparation methods are the same.

[0048] Application Example 1

[0049] A method for preparing a membrane electrode, the method being as follows:

[0050] 1) Weigh 20 g of the catalyst prepared in each example and comparative example, mix it with a resin solution containing 5 g Nafion, 37.5 g ethylene glycol and 62.5 g pure water, sonicate and stir for 2 hours to make a slurry;

[0051] 2) Apply the slurry evenly to a membrane area of ​​20 cm². 2 On a proton exchange membrane, the loading of the supported catalyst was controlled at 1.0 mg / cm³. 2 After coating, the membrane electrode is dried at 80 °C for 24 hours to obtain the membrane electrode.

[0052] Test Example 1

[0053] Performance testing:

[0054] The PEM water electrolysis single-cell test system was used for evaluation. The test temperature was controlled at 80 ℃ and the pressure was atmospheric pressure. The initial performance was tested by constant current step polarization curve testing, and the test current density range was 0.01–1.0 A / cm. 2 Record 1.0 A / cm 2 The slot voltage, denoted as V 初始 The durability test was conducted in constant current mode at 1.0 A / cm². 2 The system was continuously run for 1000 hours, and voltage changes were monitored. The test results were marked as V. 测试后 .

[0055] The test results of each embodiment and comparative example are shown in Table 1 below:

[0056] Table 1 Performance Test Table

[0057]

[0058] Comparative Example 1, by replacing titanium oxysulfate with cerium dioxide, maintained a value of 1.0 A / cm. 2 The voltage at which it was applied was significantly higher than in the embodiments. As a carrier material, rather than a soluble precursor, in a molten salt medium, the density after melting was approximately 1.9-2.0 g / cm³. 3 The density of CeO2 particles is approximately 7.1-7.2 g / cm³. 3 Due to significant density differences, rapid sedimentation occurs, resulting in extremely uneven distribution of the support in the reaction system. Consequently, it is difficult for the iridium feedstock to achieve uniform molecular-level contact with the support, ultimately leading to uneven loading and significantly inferior catalytic performance compared to the example.

[0059] Comparative Example 2, due to the absence of carrier material, maintained a value of 1.0 A / cm. 2 The voltage at this stage is significantly higher than in the embodiments. Because there is no support to constrain the IrO2 particles, they undergo severe sintering and agglomeration at high temperatures, resulting in a significant increase in the size of the iridium oxide particles, a sharp decrease in the specific surface area, a reduction in the exposure of active sites, and a significantly inferior catalytic performance compared to the embodiments.

[0060] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0061] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a supported iridium oxide-based catalyst, characterized in that, The preparation method includes the following steps: 1) The carrier raw material, dispersion medium and iridium raw material are mixed to obtain a precursor mixture; 2) The precursor mixture is calcined, and after cleaning and drying, the supported iridium oxide-based catalyst is obtained.

2. The method for preparing the supported iridium oxide-based catalyst according to claim 1, characterized in that, In step 1), the carrier raw material is one or more of cerium nitrate, cerium ammonium nitrate, titanium oxysulfate, zirconium nitrate, or zirconium oxynitrate.

3. The method for preparing the supported iridium oxide-based catalyst according to claim 1, characterized in that, In step 1), the dispersion medium is one or more of sodium nitrate or potassium nitrate.

4. The method for preparing the supported iridium oxide-based catalyst according to claim 1, characterized in that, In step 1), the iridium raw material is one or more of iridium chloride or chloroiridium acid.

5. The method for preparing the supported iridium oxide-based catalyst according to any one of claims 1-4, characterized in that, In step 1), the mass ratio of the carrier raw material, dispersion medium and iridium raw material in the precursor mixture is 1:1~100:0.2~2.

6. The method for preparing the supported iridium oxide-based catalyst according to claim 1, characterized in that, In step 2), the calcination temperature is 330~550 ℃, the calcination time is 5~300 min, and the gas atmosphere is air.

7. The method for preparing the supported iridium oxide-based catalyst according to claim 1 or 6, characterized in that, In step 2), after cleaning and drying, a furnace calcination treatment is added. After the furnace calcination treatment is completed, the supported iridium oxide-based catalyst is obtained by grinding. The furnace calcination treatment is carried out at a temperature of 350-600 ℃ and a calcination time of 10-120 min, with air as the gas atmosphere.

8. A supported iridium oxide-based catalyst prepared by the preparation method as described in claim 1.

9. The application of the supported iridium oxide-based catalyst as described in claim 8 as a catalyst for a proton exchange membrane water electrolysis anode.

10. A membrane electrode, characterized in that, The membrane electrode was prepared using the supported iridium oxide-based catalyst as described in claim 8 as the active material.

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