A method for preparing a high-activity and high-stability iridium oxide catalyst
By employing a segmented heat treatment method combined with slow-release alkali and sulfate solution, the contradiction between the activity and stability of iridium oxide catalysts was resolved, enabling the preparation of highly active and stable iridium oxide catalysts suitable for industrial-scale applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU LOPAL TECH CO LTD
- Filing Date
- 2026-05-13
- Publication Date
- 2026-06-26
Smart Images
Figure FT_1 
Figure FT_2 
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of PEM electrolysis water production catalyst technology, and particularly relates to a method for preparing a highly active and highly stable iridium oxide catalyst. Background Technology
[0002] Proton exchange membrane (PEM) water electrolyzers are considered one of the most critical technologies for producing "green hydrogen" due to their advantages such as high efficiency, high current density, fast response, and compatibility with the intermittent nature of renewable energy sources. The catalyst is a crucial component of the PEM electrolyzer, directly determining its efficiency, lifespan, and cost.
[0003] Iridium oxide (IrO2) has extremely high Ir-O bond energy, stable crystal structure, and extremely low dissolution rate in strong acids, making it one of the most promising types of PEM anode catalysts for industrial application.
[0004] The conventional methods for preparing iridium oxide currently include: First, the Adams melting method, which involves melting and oxidizing iridium nitrate and sodium nitrate at a certain molar ratio at high temperature, holding the reaction at 500-550℃, and obtaining pure rutile phase IrO2 after washing and desalting; Second, the high-temperature calcination method, which uses chloroiridic acid as a precursor and calcines it in an air atmosphere at 400-600℃ to directly decompose it into IrO2, which is simple and low-cost; Third, the sol-gel method, in which iridium salt and complexing agent form a uniform sol, which is dehydrated and condensed into a gel, and then calcined at 300-450℃ to obtain ultrafine nano-iridium oxide particles; Fourth, the electrochemical deposition method, which involves in-situ oxidation of the substrate to form an IrO2 coating in an acidic chloroiridic acid electrolyte through constant potential or pulse deposition.
[0005] However, existing preparation methods still have many shortcomings: high-temperature processes (Adams melting method, high-temperature calcination method) have high energy consumption, the product particle size is relatively large and easy to agglomerate, the specific surface area is small, the atom utilization rate is low, and the Adams melting method generates a large amount of sodium salt waste liquid, and the post-treatment process is cumbersome; iridium oxide has an inherent contradiction between activity and stability, and amorphous IrO x High activity but easy to dissolve; crystalline IrO2 has good stability but low activity; while the sol-gel method is complicated and has a long preparation cycle, making it difficult to achieve large-scale mass production; the loading of the electrochemical deposition method is difficult to control precisely, and the consistency is poor when preparing in large batches, making it difficult to use in industry.
[0006] Therefore, there is an urgent need for a process that can produce iridium oxide catalysts with high activity and strong stability, and that can be industrially applied. Summary of the Invention
[0007] Purpose of the invention: This invention provides a method for preparing iridium oxide catalysts with high activity and strong stability, which is suitable for industrial-scale application.
[0008] Technical solution: The preparation method of the highly active iridium oxide catalyst of the present invention includes the following steps:
[0009] (1) Add slow-release alkali to the aqueous solution of iridium source and stir the reaction at 60-90℃ for 2-4 h to obtain iridium-hydroxy colloidal solution;
[0010] (2) Add sulfate solution to iridium-hydroxy colloidal solution, continue stirring at 60-90℃ for 2-3 h, add slow-release acid, and stir until the colloid aggregates into uniform clusters and settles to obtain fine precipitate;
[0011] (3) After washing, filtering and drying the precipitate, it is subjected to segmented heat treatment: first, it is kept at an inert atmosphere and 300-350℃ for 1-2 h, and then kept at an oxygen-containing atmosphere and 450-500℃ for 1-2 h to obtain a highly active and stable iridium oxide catalyst.
[0012] Furthermore, in step (1) of the preparation method, the iridium source is selected from iridium trichloride or chloroiridium acid, and the mass ratio of iridium source to water is 1:(40-80).
[0013] Furthermore, in step (1) of the preparation method, the slow-release alkali is selected from urea, ammonium carbonate or ammonium bicarbonate, and the amount of slow-release alkali added is such that the pH value of the aqueous solution of the iridium source reaches 10-11.
[0014] Furthermore, in step (2) of the preparation method, the molar ratio of sulfate to iridium is (0.25-0.5):1.
[0015] Furthermore, in step (2) of the preparation method, the concentration of the sulfate solution is 0.1-0.5 M; the sulfate is one or both of sodium sulfate and potassium sulfate.
[0016] Furthermore, in step (2) of the preparation method, the slow-release acid is selected from dilute nitric acid or dilute hydrochloric acid, and its concentration is 0.1-0.5 M.
[0017] Furthermore, in step (2) of the preparation method, the reaction temperature for stirring until the colloid agglomerates into uniform clusters and settles is 60-90℃, and the reaction time is 1-2 h.
[0018] Furthermore, the amount of slow-release acid added in this preparation method is used to adjust the pH of the system to 7-9.
[0019] Beneficial effects: Compared with the prior art, the significant advantage of this invention is that the iridium oxide catalyst achieves a yield of 1 A / cm 2 Under these conditions, the electrolysis voltage of a single cell reaches 1.599-1.612 V; 2 A / cm2 Under these conditions, the electrolysis voltage of a single cell reaches 1.746-1.759V; 3 A / cm 2 Under these conditions, the electrolysis voltage of a single cell reaches 1.885-1.896 V, exhibiting excellent catalytic activity; moreover, stability testing showed no degradation after 500 h, demonstrating good stability. This indicates that the catalyst achieved simultaneous improvement in both activity and stability. Attached Figure Description
[0020] Figure 1 The polarization curves of the iridium oxide catalysts prepared in Examples 1-5 and the comparative examples are shown.
[0021] Figure 2 The figures show the stability test results of the iridium oxide catalysts prepared in Examples 1-5, Comparative Examples, and Comparative Examples 1-3. Detailed Implementation
[0022] The technical solution of the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.
[0023] All raw materials used in this invention are commercially available, and their composition information is shown in Table 1 below.
[0024] Table 1 Raw Material Information Table
[0025]
[0026] Comparative Example - Existing Iridium Oxide Catalysts
[0027] Existing iridium oxide catalysts are prepared by the following steps:
[0028] (1) Mix 1 g of chloroiridic acid and 60 g of water and stir for 1 h.
[0029] (2) Add 25% sodium hydroxide to the mixture, adjust the pH to 11, heat to 90°C, and stir for 4 h.
[0030] (3) Adjust the pH of the solution in step 2 to 8 with 1M nitric acid, stir for 1h, and obtain iridium oxide precipitate.
[0031] (4) Wash and filter the iridium oxide with water and dry it at 60°C.
[0032] (5) Heat treatment at 500°C in air for 1 h to obtain iridium oxide product.
[0033] Example 1
[0034] The iridium oxide catalyst of Example 1 was prepared by the following steps:
[0035] (1) Mix 1 g of chloroiridic acid (iridium content is 35%) with 60 g of water and stir for 1 h to obtain an aqueous solution of chloroiridic acid.
[0036] (2) Add 25 wt% ammonium carbonate to the aqueous solution of chloroiridium acid to adjust the pH of the initial solution to 10, heat to 60°C, and stir for 2 h to form an iridium-hydroxy colloidal solution.
[0037] (3) Add 4.6 ml of 0.1 M sodium sulfate solution to the iridium-hydroxy colloidal solution, continue stirring at 60 °C for 2 h, adjust the pH of the solution to 7 with 0.5 M nitric acid, and continue stirring for 1 h to obtain iridium oxide precipitate.
[0038] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 300°C in argon for 1 h, and then kept at 450°C in air for 1 h to obtain the iridium oxide catalyst.
[0039] Comparative Example 1
[0040] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that sodium hydroxide is used instead of slow-release alkali in step (2). The specific steps are as follows:
[0041] (1) Mix 1 g of chloroiridic acid and 60 g of water and stir for 1 h to obtain an aqueous solution of chloroiridic acid.
[0042] (2) Add 25 wt% sodium hydroxide to the aqueous solution of chloroiridium acid to adjust the pH of the initial solution to 10, heat to 60°C, and stir for 2 h to form an iridium-hydroxy colloidal solution.
[0043] (3) Add 4.6 ml of 0.1 M sodium sulfate solution to the iridium-hydroxy colloidal solution, continue stirring at 60 °C for 2 h, adjust the pH of the solution to 7 with 0.5 M nitric acid, and continue stirring for 1 h to obtain iridium oxide precipitate.
[0044] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 300°C in argon for 1 hour, and then kept at 450°C in air for 1 hour to obtain the iridium oxide catalyst.
[0045] Example 2
[0046] The preparation method of the highly active iridium oxide catalyst in Example 2 includes the following steps:
[0047] (1) Mix 1 g of chloroiridic acid and 80 g of water and stir for 1 h to obtain an aqueous solution of chloroiridic acid.
[0048] (2) Add 25 wt% ammonium carbonate to the aqueous solution of chloroiridium acid to adjust the pH of the initial solution to 11, heat to 90°C, and stir for 4 h to form an iridium-hydroxy colloidal solution.
[0049] (3) Add 9.1 ml of 0.1 M potassium sulfate solution to the iridium-hydroxy colloidal solution, continue stirring at 90 °C for 2 h, adjust the pH of the solution to 8 with 0.1 M nitric acid, and continue stirring for 1 h to obtain iridium oxide precipitate.
[0050] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 350°C in argon for 1 h, and then kept at 450°C in air for 2 h to obtain a highly active iridium oxide catalyst.
[0051] Comparative Example 2
[0052] Comparative Example 2 is basically the same as Example 2, except that sodium hydroxide is used instead of the slow-release alkali in step (2). The specific steps are as follows:
[0053] (1) Mix 1 g of chloroiridic acid and 80 g of water and stir for 1 h to obtain an aqueous solution of chloroiridic acid.
[0054] (2) Add 25 wt% sodium hydroxide to the aqueous solution of chloroiridium acid to adjust the pH of the initial solution to 11, heat to 90°C and stir for 4 h to form an iridium-hydroxy colloidal solution.
[0055] (3) Add 9.1 ml of 0.1 M potassium sulfate solution to the iridium-hydroxy colloidal solution, continue stirring at 90 °C for 2 h, adjust the pH of the solution to 8 with 0.1 M nitric acid, and continue stirring for 1 h to obtain iridium oxide precipitate.
[0056] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 350°C in argon for 1 h, and then kept at 450°C in air for 2 h to obtain a highly active iridium oxide catalyst.
[0057] Example 3
[0058] The preparation method of the highly active iridium oxide catalyst in Example 3 includes the following steps:
[0059] (1) Mix 1 g of iridium trichloride and 60 g of water and stir for 1 h to obtain an aqueous solution of iridium trichloride.
[0060] (2) Add 25wt% ammonium bicarbonate to the aqueous solution of iridium trichloride to adjust the pH of the initial solution to 11, heat to 70°C, and stir for 3 h to form an iridium-hydroxy colloidal solution.
[0061] (3) Add 9.8 ml of 0.1 M sodium sulfate solution to the iridium-hydroxy colloidal solution, continue stirring at 70 °C for 3 h, adjust the pH of the solution to 8 with 0.2 M hydrochloric acid, and continue stirring for 2 h to obtain iridium oxide precipitate.
[0062] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 350°C for 2 h in argon, and then kept at 500°C in air for 1 h to obtain a highly active iridium oxide catalyst.
[0063] Comparative Example 3
[0064] The preparation method of Comparative Example 3 is basically the same as that of Example 3, except that sodium hydroxide is used instead of slow-release alkali in step (2). The specific steps are as follows:
[0065] (1) Mix 1 g of iridium trichloride and 60 g of water and stir for 1 h to obtain an aqueous solution of iridium trichloride.
[0066] (2) Add 25wt% sodium hydroxide to the iridium trichloride aqueous solution to adjust the pH of the initial solution to 11, heat to 70℃, stir for 3h to form an iridium-hydroxy colloidal solution.
[0067] (3) Add 9.8 ml of 0.1 M sodium sulfate solution to the iridium-hydroxy colloidal solution, continue stirring at 70 °C for 3 h, adjust the pH of the solution to 8 with 0.2 M hydrochloric acid, and continue stirring for 2 h to obtain iridium oxide precipitate.
[0068] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 350°C for 2 h in argon, and then kept at 500°C in air for 1 h to obtain a highly active iridium oxide catalyst.
[0069] Example 4
[0070] The preparation method of the highly active iridium oxide catalyst in Example 4 includes the following steps:
[0071] (1) Mix 1 g of chloroiridic acid and 40 g of water and stir for 1 h to obtain an aqueous solution of chloroiridic acid.
[0072] (2) Add 25wt% of urea to the aqueous solution of chloroiridium acid to adjust the pH of the initial solution to 10, heat to 80°C, and stir for 3 h to form an iridium-hydroxy colloidal solution.
[0073] (3) Add 1.8 ml of 0.5 M sodium sulfate solution to the iridium-hydroxy colloidal solution and continue stirring at 80 °C for 2 h to carry out surface ligand exchange; adjust the pH of the solution to 7 with 0.5 M hydrochloric acid and continue stirring for 2 h to obtain iridium oxide precipitate.
[0074] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 350°C in argon for 1 h, and then kept at 500°C in air for 1 h to obtain a highly active iridium oxide catalyst.
[0075] Example 5
[0076] The preparation method of the highly active iridium oxide catalyst in Example 5 includes the following steps:
[0077] (1) Mix 1 g of iridium trichloride and 60 g of water and stir for 1 h to obtain an aqueous solution of iridium trichloride.
[0078] (2) Add 25 wt% urea to the aqueous solution of iridium trichloride to adjust the pH of the initial solution to 11, heat to 90°C and stir for 4 h to form an iridium-hydroxy colloidal solution.
[0079] (3) Add 3.9 ml of 0.25 M sodium sulfate solution to the iridium-hydroxy colloidal solution and continue stirring at 90 °C for 3 h to carry out surface ligand exchange; adjust the pH of the solution to 9 with 0.1 M nitric acid and continue stirring for 1 h to obtain iridium oxide precipitate.
[0080] (4) The iridium oxide precipitate was washed and filtered with water, dried at 60°C, and then subjected to segmented heat treatment: first, it was kept at 350°C in argon for 1 hour, and then kept at 500°C in air for 1 hour to obtain a highly active iridium oxide catalyst.
[0081] Performance Testing 1 - Electrochemical Performance
[0082] The electrochemical performance of existing iridium oxide catalysts (comparative examples), and the composite catalysts prepared in Examples 1 to 5, and Comparative Examples 1 to 3, was tested. The electrochemical performance is shown in Table 2 below. The polarization curve test results of Examples 1 to 5 and the existing iridium oxide catalyst are as follows. Figure 1 As shown. The stability tests of existing iridium oxide catalysts (comparative examples), Examples 1 to 5, and Comparative Examples 1 to 3 are as follows. Figure 2 As shown.
[0083] Table 2 Electrochemical performance
[0084]
[0085] Depend on Figure 1As shown in Table 2, the oxygen evolution overpotential of existing iridium oxide catalysts reaches 370 mV. However, the oxygen evolution overpotentials of the iridium oxide prepared in Examples 1 to 5 of this application are 300 mV, 315 mV, 310 mV, 312 mV, and 309 mV, respectively, with the lowest being 300 mV. Furthermore, at 80°C and 1 A / cm², the oxygen evolution overpotentials are significantly higher. 2 Under these conditions, the electrolysis voltage of a single cell is 1.599-1.612 V; 2 A / cm 2 Under these conditions, the electrolysis voltage of a single cell is 1.746 - 1.759 V; 3 A / cm 2 Under these conditions, the electrolysis voltage of a single cell is 1.885 - 1.896 V.
[0086] And Table 2 combined Figure 2 The stability test results show that at 80℃ and 1 A / cm 2 Under the condition of 500 hours of testing, the voltage curves of Examples 1-5 showed no obvious upward trend, and even showed a slight downward trend overall. Based on the overall slope, the attenuation rate was negative. Therefore, starting from the stable point, it was considered to have no attenuation and good stability, achieving a simultaneous improvement in activity and stability. Figure 2 In the comparison, the voltage curves of the comparative example and comparative examples 1-3 show a significant increase, with uniform attenuation to varying degrees.
[0087] In Comparative Examples 1-3, the oxygen evolution overpotentials of iridium oxide were 340 mV, 345 mV, and 343 mV, respectively, at 80 °C and 1 A / cm². 2 Under these conditions, the electrolysis voltage of a single cell is 1.671-1.682 A / cm. 2 2 A / cm 2 Under these conditions, the electrolysis voltage of a single cell is 1.819-1.831 V, and the capacitance is 3 A / cm². 2 Under these conditions, the electrolysis voltage of a single cell is 1.950-1.958 V, and the catalyst decay rate is 14-18 µV / h.
[0088] Existing iridium oxide catalysts (comparative example) operate at 80℃ and 1 A / cm². 2 The electrolytic voltage of the single battery is 1.793 V; 2A / cm 2 Under these conditions, the electrolysis voltage of a single cell is 1.955 V; 3 A / cm 2 Under these conditions, the electrolysis voltage of a single cell is 2.109 V, and the catalyst decay rate is 30 µV / h.
[0089] Furthermore, based on the electrochemical performance data of Examples 1 and 1, Examples 2 and 2, and Examples 3 and 3, it can be seen that when a strong base is used to prepare the iridium precursor, even if sodium sulfate solution is introduced and dilute acid is used for precipitation, the obtained electrochemical performance and stability are poor.
[0090] This verifies that, in the preparation of iridium oxide catalysts, adding sodium sulfate after the formation of an iridium precursor using a slow-release alkali can simultaneously enhance the activity and stability of the prepared iridium oxide catalyst. Further mechanistic analysis reveals that in this preparation method, the iridium precursor aqueous solution undergoes uniform nucleation under the action of the slow-release alkali, forming an iridium hydroxide colloid. Under the action of diluting acid, the colloid slowly ages and aggregates into uniform clusters that settle. The slow decomposition of the slow-release alkali causes a gradient increase in the pH of the system. Under controlled nucleation conditions, iridium ions form an iridium-hydroxy colloid with a high-density surface hydroxyl group and a uniform porous structure. Based on this, in the colloidal chemistry stage of the homogeneous precipitation synthesis of IrO2, a surface ligand exchange step is introduced. Utilizing the coordination ability and electronic effects of sulfate ions, specific chemical properties are formed on the material surface. This directionally endows the final IrO2 powder with excellent intrinsic activity and exceptional stability without altering the main synthesis pathway. Furthermore, the introduction of sulfate ions relies on the high-density hydroxyl groups on the colloid surface as exchange active sites to promote the uniform intercalation of sulfate ions. If rapid alkalization (such as directly adding a strong alkali) is used instead of slow-release alkali, the resulting colloid surface hydroxyl groups will be unevenly distributed and the pore structure will collapse. Sulfate ions will not be able to be uniformly inserted, resulting in a dispersed distribution of oxygen vacancies and a significant decrease in catalytic activity during subsequent heat treatment.
[0091] In addition to the above embodiments, it should be noted that the technical effects claimed by the present invention can be achieved by using the preparation process and the limited parameter range of the present invention, and therefore no further examples will be provided to support these claims.
Claims
1. A method for preparing a highly active and highly stable iridium oxide catalyst, characterized in that, Includes the following steps: (1) Add slow-release alkali to the aqueous solution of iridium source and stir the reaction at 60-90℃ for 2-4 h to obtain iridium-hydroxy colloidal solution; (2) Add sulfate solution to iridium-hydroxy colloidal solution, continue stirring at 60-90℃ for 2-3 hours, add slow-release acid, and stir until the colloid aggregates into uniform clusters and settles to obtain fine precipitate; (3) After washing, filtering and drying the precipitate, it is subjected to segmented heat treatment: first, it is kept at 300-350℃ in an inert atmosphere for 1-2 h, and then kept at 450-500℃ in an oxygen-containing atmosphere for 1-2 h to obtain a highly active and stable iridium oxide catalyst.
2. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1, characterized in that, In step (1), the iridium source is selected from iridium trichloride or chloroiridium acid, and the mass ratio of iridium source to water is 1:(40-80).
3. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1, characterized in that, In step (1), the slow-release alkali is selected from urea, ammonium carbonate or ammonium bicarbonate, and the amount of slow-release alkali added is such that the pH value of the aqueous solution of the iridium source reaches 10-11.
4. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1, characterized in that, In step (2), the molar ratio of sulfate to iridium is (0.25-0.5):
1.
5. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1 or 4, characterized in that, The concentration of the sulfate solution is 0.1-0.5 M; the sulfate is one or both of sodium sulfate and potassium sulfate.
6. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1, characterized in that... In step (2), the slow-release acid is selected from dilute nitric acid or dilute hydrochloric acid, and its concentration is 0.1-0.5 M.
7. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1, characterized in that, In step (2), the reaction temperature for stirring until the colloid agglomerates into uniform clusters and settles is 60-90 ℃, and the reaction time is 1-2 h.
8. The method for preparing a highly active and highly stable iridium oxide catalyst according to claim 1 or 6, characterized in that, The amount of slow-release acid added is used to adjust the pH of the system to 7-9.