Preparation method of manganese oxide and supported iridium-ruthenium oxide catalyst

Abstract

This invention provides a method for preparing manganese oxide and a supported iridium-ruthenium oxide catalyst, relating to the field of catalyst technology. The invention uses a mixture of inorganic manganese salt and a first nitrate promoter for a first heat treatment to obtain manganese oxide, which can be used as a support for the supported iridium-ruthenium oxide catalyst, improving its catalytic activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a method for preparing manganese oxide and a supported iridium-ruthenium oxide catalyst. Background Technology

[0002] Proton exchange membrane electrolysis (PEMWE) for hydrogen production is considered one of the most promising technologies for green hydrogen production. However, the cathode reaction (hydrogen evolution reaction, HER) and anodic reaction (oxygen evolution reaction, OER) in PEMWE require large amounts of precious metals such as platinum and iridium as catalysts to meet the activity and stability requirements of the electrolyzer in practical applications. This significantly increases the cost of PEMWE and hinders the large-scale application of this technology. Designing efficient and stable supported catalysts can help improve the utilization rate of precious metals and reduce the amount of precious metals used. Therefore, the support has a significant impact on the catalytic performance of supported catalysts.

[0003] γ-MnO2 is one of the supported catalyst supports mentioned above. Mn and Ir have a special affinity, resulting in good catalytic performance even at relatively low Ir loading. However, this catalytic activity also depends on the dispersion of Ir, such as the Ir being in an atomically dispersed state.

[0004] Therefore, further optimization of the preparation method of MnO2 supports is needed to obtain MnO2 supports with better performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing manganese oxide and a supported iridium-ruthenium oxide catalyst.

[0006] The technical solution of the present invention is as follows: A method for preparing manganese oxide, comprising subjecting a mixture of inorganic manganese salt and a first nitrate auxiliary agent to a first heat treatment.

[0007] Preferably, the inorganic manganese salt is selected from one or a combination of two or more of manganese nitrate, manganese chloride, manganese sulfate, and manganese carbonate.

[0008] Preferably, the weight ratio of the inorganic manganese salt to the first nitrate auxiliary agent is 1:3-10.

[0009] The first nitrate additive is selected from one or a combination of two or more of sodium nitrate, potassium nitrate and lithium nitrate.

[0010] Preferably, the temperature of the first heat treatment is 250-600℃, and the time of the first heat treatment is 10min-1h.

[0011] A supported iridium-ruthenium oxide catalyst, wherein manganese oxide obtained by the preparation method described in any of the above embodiments is used as a support, and iridium-ruthenium oxide is supported on the support.

[0012] Preferably, the support accounts for 15-85% of the weight of the catalyst, and the molar ratio of iridium to ruthenium in the iridium-ruthenium oxide is 5:5-9:1.

[0013] Preferably, the preparation method of the supported iridium-ruthenium oxide catalyst is as follows: the manganese oxide support, iridium source, ruthenium source, second nitrate additive and pore-forming agent are mixed evenly and then subjected to a second heat treatment to obtain the catalyst.

[0014] More preferably, the iridium source is selected from one or a combination of two or more of iridium tetrachloride, iridium acetate, iridium sulfate, chloroiridic acid, iridium trichloride and iridium acetate; The ruthenium source is selected from one or a combination of two of ruthenium chloride, ruthenium nitrate, ruthenium sulfate, and ruthenium acetate.

[0015] More preferably, the weight ratio of the manganese oxide, the pore-forming agent, and the second nitrate auxiliary agent is 1:3-10:5-15; The second nitrate additive is selected from one or a combination of two or more of sodium nitrate, potassium nitrate, and lithium nitrate; The pore-forming agent is selected from one or a combination of two or more of carbonates, bicarbonates and carbides.

[0016] More preferably, the temperature of the second heat treatment is 250-600°C, and the time of the second heat treatment is 10 min-1 h.

[0017] The beneficial effects of this invention are: (1) The manganese oxide obtained by the preparation method of the present invention has a lot of oxygen vacancies and low crystallinity manganese oxygen functional groups on its surface. When used as a support, it is beneficial to improve the binding and loading of noble metals and promote the electron transfer between the support and the metal active site, which can greatly improve the overall performance of the catalyst, including catalytic activity.

[0018] (2) The supported catalyst of the present invention is supported by bimetals (Ir and Ru). Under the action of nitrate additives and pore-forming agents, a porous Ir / Ru-O-Mn composite interface can be fully formed to achieve the full synergistic effect of Ir-Ru. This can improve the catalytic activity of Ir and the stability of Ru, thus meeting the activity and stability requirements of the catalyst in the field of water electrolysis. Attached Figure Description

[0019] Figure 1 This is a SEM image of the manganese oxide powder obtained in Example 1.

[0020] Figure 2The results are the electrochemical oxygen evolution polarization curves of the catalyst in Example 1.

[0021] Figure 3 The results show the performance test results of the catalyst of Example 1 applied to the PEM water electrolysis membrane electrode device.

[0022] Figure 4 The results are the electrochemical oxygen evolution polarization curves of the catalyst in Example 2.

[0023] Figure 5 The results are the electrochemical oxygen evolution polarization curves of the catalyst in Example 3. Detailed Implementation

[0024] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0025] On one hand, the present invention proposes a method for preparing manganese oxide, which is obtained by first heat treatment of a mixture composed of inorganic manganese salt and a first nitrate auxiliary agent.

[0026] This invention uses a first nitrate additive. At the first heat treatment temperature, the first nitrate additive undergoes a high-temperature melting reaction with inorganic manganese salt. The prepared manganese oxide has a large number of oxygen vacancies and low-crystallinity manganese oxygen functional groups on its surface, which improves the activity of manganese oxide. When manganese oxide is used as a support, it is more conducive to combining with noble metals, improving the loading performance and the catalytic activity of the catalyst.

[0027] There are no particular restrictions on the atmosphere for the first heat treatment; it can be an oxidizing atmosphere, such as a continuous flow of air.

[0028] In some embodiments, the inorganic manganese salt is selected from one or a combination of two or more of manganese nitrate, manganese chloride, manganese sulfate, and manganese carbonate.

[0029] In some embodiments, the weight ratio of the inorganic manganese salt to the first nitrate auxiliary agent is 1:3-10. For example, the weight ratio can be any value or any value between 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc., without particular limitation. Further, the weight ratio of the inorganic manganese salt to the first nitrate auxiliary agent is 1:3-8.

[0030] The first nitrate additive is selected from one or a combination of two or more of sodium nitrate, potassium nitrate, and lithium nitrate. The first nitrate additive acts as a melt oxidant, converting inorganic manganese salts into manganese oxide.

[0031] The purpose of the first heat treatment is to achieve the melting reaction of the first nitrate additive and the inorganic manganese salt. In some embodiments, the temperature of the first heat treatment is 250-600°C, and the time of the first heat treatment is 10 min-1 h. For example, the temperature of the first heat treatment can be any value or any value between 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, and 600°C, without particular limitation; the time of the first heat treatment can be any value or any value between 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min, without particular limitation.

[0032] For mixtures composed of inorganic manganese salts and first nitrate additives, there are no particular restrictions on the preparation method. The inorganic manganese salts and first nitrate additives can be directly mixed in powder form, or they can be dispersed and / or dissolved in a solvent, followed by solvent removal to obtain the mixture. Specifically, the method can be as follows: dissolve the inorganic manganese salt in a first mixed solvent composed of a first alcohol solvent (e.g., isopropanol) and water, add the first nitrate additive, stir for 15 min to 2 h, and remove the first mixed solvent (e.g., by rotary evaporation) to obtain the mixture. There are no particular restrictions on the volume ratio of the first alcohol solvent to water in the first mixed solvent. For example, the volume ratio of the first alcohol solvent to water can be 9:1 to 1:9, or further, it can be 7:3 to 2:8. There are no particular restrictions on the ratio of inorganic manganese salt to the first mixed solvent. For example, the concentration of inorganic manganese salt can be 1-100 mg / ml, or further, the concentration of inorganic manganese salt can be 5-50 mg / ml, such as 5 mg / ml, 10 mg / ml, 15 mg / ml, 20 mg / ml, 25 mg / ml, 30 mg / ml, 35 mg / ml, 40 mg / ml, 45 mg / ml, 50 mg / ml, etc.

[0033] On the other hand, the present invention also proposes a supported iridium-ruthenium oxide catalyst, wherein manganese oxide obtained by the preparation method described in any of the above embodiments is used as a support, and iridium-ruthenium oxide is supported on the support.

[0034] The supported iridium-ruthenium oxide catalyst of this invention uses manganese oxide as a support and iridium-ruthenium oxide as the main catalytically active component. The good bonding between the manganese oxide support and the iridium-ruthenium oxide promotes electron transfer between the support and the metal active sites, significantly improving the catalytic activity and stability of the catalyst. In this invention, the supported iridium-ruthenium oxide catalyst can be represented as IrRuO. x / MnO2, where x represents oxygen vacancies or high-valence peroxides in iridium-ruthenium oxides, and x can range from 1.4 to 3.

[0035] In some embodiments, the support accounts for 15-85% of the weight of the catalyst, and the molar ratio of iridium to ruthenium in the iridium-ruthenium oxide is 5:5-9:1.

[0036] For example, the weight percentage of manganese oxide support in the catalyst can be any value or any value between 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc., without any particular restriction. Besides the manganese oxide support, the main component remaining in the catalyst is the catalytically active component—iridium-ruthenium oxide. It may also contain small amounts of dopants between the iridium-ruthenium oxide and the manganese oxide support, such as iridium and / or ruthenium-doped manganese oxide, or manganese-doped iridium-ruthenium oxide. The molar ratio of iridium to ruthenium in the iridium-ruthenium oxide can be any value or any value between 5:5, 6:4, 2:1, 7:3, 3:1, 8:2, 9:1, etc., without any particular restriction.

[0037] In some embodiments, the preparation method of the supported iridium-ruthenium oxide catalyst is as follows: the above-mentioned manganese oxide support, iridium source, ruthenium source, second nitrate additive and pore-forming agent are mixed evenly and then subjected to a second heat treatment to obtain the catalyst.

[0038] In this invention, the second nitrate additive plays a role in melting oxidation, and the pore-forming agent plays a role in assisting pore formation. This is beneficial for forming a porous Ir / Ru-O-Mn composite interface in the supported iridium-ruthenium oxide catalyst, realizing the full synergistic effect of Ir-Ru. This can not only improve the catalytic activity of Ir, but also improve the stability of Ru, thus meeting the activity and stability requirements of the catalyst in the field of water electrolysis.

[0039] Specifically, the catalyst preparation method can be as follows: manganese oxide, iridium source, ruthenium source, second nitrate additive, and pore-forming agent are uniformly dispersed in a mixed solvent composed of an alcohol solvent (such as isopropanol) and water. The mixed solvent is removed, and the obtained solid undergoes a second heat treatment, followed by washing and drying to obtain the catalyst. There are no particular restrictions on the volume ratio of the alcohol solvent to water in the above mixed solvent. For example, the volume ratio of the alcohol solvent to water can be 9:1 to 1:9, or further, it can be 7:3 to 2:8. There are no particular restrictions on the ratio of manganese oxide to the mixed solvent. For example, the concentration of manganese oxide can be 1-100 mg / ml, or further, the concentration of manganese oxide can be 5-50 mg / ml, such as 5 mg / ml, 10 mg / ml, 15 mg / ml, 20 mg / ml, 25 mg / ml, 30 mg / ml, 35 mg / ml, 40 mg / ml, 45 mg / ml, 50 mg / ml, etc.

[0040] Furthermore, the iridium source is selected from one or a combination of two or more of iridium tetrachloride, iridium acetate, iridium sulfate, chloroiridic acid, iridium trichloride, and iridium acetate; The ruthenium source is selected from one or a combination of two or more of ruthenium chloride, ruthenium nitrate, ruthenium sulfate, and ruthenium acetate.

[0041] Furthermore, the weight ratio of manganese oxide, pore-forming agent, and second nitrate auxiliary agent is 1:3-10:5-15; for example, the weight ratio of manganese oxide, pore-forming agent, and second nitrate auxiliary agent can be any value or any value between 1:3:5, 1:3:10, 1:3:15, 1:5:5, 1:5:10, 1:5:15, 1:7:5, 1:7:10, 1:7:15, 1:10:5, 1:10:10, 1:10:15, etc., without any particular limitation. Furthermore, the weight ratio of manganese oxide, pore-forming agent, and second nitrate auxiliary agent can be 1:3-8:5-15.

[0042] The second nitrate auxiliary is selected from one or a combination of two or more of sodium nitrate, potassium nitrate and lithium nitrate; The pore-forming agent decomposes at high temperatures, producing gases such as carbon dioxide, which can form porous Ir / Ru-O-Mn composite interfaces in supported iridium-ruthenium oxide catalysts. The pore-forming agent can be selected from one or more combinations of carbonates, bicarbonates, and carbides. Examples of carbonates include sodium carbonate, lithium carbonate, potassium carbonate, and ammonium carbonate; examples of bicarbonates include sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate.

[0043] Furthermore, the temperature of the second heat treatment is 250-600℃, and the time of the second heat treatment is 10 min-1 h. For example, the temperature of the second heat treatment can be any value or any value in between, such as 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, etc., without any particular limitation; the time of the second heat treatment can be any value or any value in between, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc., without any particular limitation.

[0044] There are no particular restrictions on the atmosphere for the second heat treatment; it can be an oxidizing atmosphere, such as a continuous flow of air.

[0045] The supported iridium-ruthenium oxide catalyst of the present invention can be used as an anode catalyst for electrocatalytic water splitting as well as an anti-reverse electrode catalyst for fuel cells.

[0046] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0047] Example 1 Weigh 200 mg of manganese nitrate and dissolve it in a mixed solvent of isopropanol and ultrapure water at a volume ratio of 3:1, with a concentration of 10 mg / ml. Stir the mixture ultrasonically for 20 min, then add 1 g of sodium nitrate and stir for 40 min. Dry the mixture by rotary evaporation at 65 °C and collect the solid powder. Heat treat the solid powder in a muffle furnace at 300 °C for 30 min. After cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter the product and dry it at 60 °C overnight to obtain manganese oxide powder.

[0048] The SEM results of the manganese oxide powder prepared in this embodiment are attached. Figure 1 As shown, the microstructure exhibits a cross-linked nanowire cone-shaped bundle structure.

[0049] Weigh 150 mg of the above manganese oxide powder and disperse it in the above mixed solvent to a concentration of 10 mg / ml. Add 50 mg (0.15 mmol) of iridium tetrachloride and 15 mg (0.072 mmol) of ruthenium trichloride, and sonicate for 30 min. Then add 0.75 g of carbamide and 2.25 g of sodium nitrate, and stir for 40 min. Dry the product by rotary evaporation at 65 °C, collect the solid powder, and heat treat the solid powder in a muffle furnace at 350 °C for 30 min. After cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter the product and dry it at 60 °C overnight to obtain the supported iridium-ruthenium oxide catalyst.

[0050] In the supported iridium-ruthenium oxide catalyst obtained in this embodiment, the weight ratio of the support is 72%, and the molar ratio of Ir to Ru is 2:1.

[0051] The supported iridium-ruthenium oxide catalyst obtained in this embodiment was subjected to a three-electrode rotating disk (RDE) test. In a 0.5 mol / L sulfuric acid electrolyte, a carbon sheet electrode and a saturated calomel electrode were used as the counter electrode and reference electrode, respectively. The working electrode was a rotating disk glassy carbon electrode loaded with the catalyst, with a catalyst loading of 400 μg / cm³. 2 The catalyst ink consisted of a mixture of 4 mg catalyst, 300 μL isopropanol, and 190 μL ultrapure water, along with 10 μL of a 5% (w / w) Nafion solution. For ease of performance comparison, all test potentials were converted to those of a standard reversible hydrogen electrode. Experimental results are attached. Figure 2 As shown, at 10 mA / cm 2 At the given current density, the overpotential of the supported iridium-ruthenium oxide catalyst in this embodiment is only 235 mV.

[0052] The catalyst prepared in this embodiment was further used for the fabrication and testing of an anode catalytic membrane electrode (MEA). A commercial platinum-carbon catalyst was selected as the MEA cathode, and the MEA was assembled with a gas diffusion layer, bipolar plates, etc., to form a PEM water electrolysis single-cell device. The results are as follows: Figure 3 As shown, the iridium loading at the anode is 1 mg / cm³. 2 At that time, the current density using an enhanced proton exchange membrane was 3 A / cm² under test conditions at 80°C. 2 The electrolysis potential is 1.746 V, and the electrolysis voltage is 2 A / cm. 2 The electrolysis potential at the current density is 1.659V, indicating that the catalyst in this embodiment has good membrane electrode device performance.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that in Example 1, when preparing the supported iridium-ruthenium oxide catalyst, manganese oxide powder was replaced with an equal weight of γ-MnO2. The remaining steps remained unchanged.

[0054] Following the test method in Example 1, the supported iridium-ruthenium oxide catalyst obtained in this comparative example was tested at 10 mA / cm². 2 The overpotential at the current density was 278 mV. Membrane electrode preparation and testing showed that the catalyst obtained in this example, using an enhanced proton exchange membrane, achieved a current density of 2 A / cm² at 80°C. 2 The electrolysis potential is 1.726V.

[0055] The stability of the supported iridium-ruthenium oxide catalysts in Comparative Example 1 and Comparative Example 1 was tested at 10 mA / cm² after 100 hours of testing according to the test method in Example 1. 2 The overpotential at a current density of 10 mA / cm² was measured after 100 h of testing of the supported iridium-ruthenium oxide catalyst in Example 1. 2 The overpotential at the current density was 238 mV, an increase of only 3 mV compared to the initial 235 mV, indicating that the supported iridium-ruthenium oxide catalyst in this embodiment has excellent stability; the supported iridium-ruthenium oxide catalyst of Comparative Example 1, after 100 h of testing, showed an overpotential of 238 mV at 10 mA / cm². 2 The overpotential at the current density was 290mV, which is 12mV higher than the initial 278mV, indicating that the stability of the catalyst in this comparative example is not as good as that of the catalyst in Example 1.

[0056] Example 2 Weigh 400 mg of manganese sulfate and dissolve it in a mixed solvent of isopropanol and ultrapure water at a volume ratio of 3:1, with a concentration of 20 mg / ml. Stir the mixture ultrasonically for 20 min, then add 2 g of sodium nitrate and stir for 40 min. Dry the mixture by rotary evaporation at 80 °C and collect the solid powder. Heat treat the solid powder in a muffle furnace at 400 °C for 20 min. After cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter the product and dry it overnight at 60 °C to obtain manganese oxide powder.

[0057] Weigh 200 mg of the above manganese oxide nanomaterial and disperse it in the above mixed solvent at a concentration of 20 mg / ml. Add 80 mg (0.2 mmol) of chloroiridium acid and 15 mg (0.072 mmol) of ruthenium trichloride, and stir ultrasonically for 30 min. Then add 0.6 g of lithium carbonate and 1 g of potassium nitrate, and stir for 40 min. Dry by rotary evaporation at 65 °C, collect the solid powder, and heat treat the solid powder in a muffle furnace at 400 °C for 30 min. After cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter and dry at 60 °C overnight to obtain the supported iridium-ruthenium oxide catalyst.

[0058] In the supported iridium-ruthenium oxide catalyst obtained in this embodiment, the weight ratio of the support is 69%, and the molar ratio of Ir to Ru is 3:1.

[0059] Following the test method in Example 1, the supported iridium-ruthenium oxide catalyst obtained in this example achieves a test at 10 mA / cm². 2 The overpotential at the current density is 250mV, as shown in the attached figure. Figure 4 As shown. Membrane electrode preparation and testing indicate that the catalyst obtained in this embodiment, using an enhanced proton exchange membrane, achieves a current density of 2 A / cm² under testing conditions at 80°C. 2 The electrolysis potential is 1.685V.

[0060] Comparative Example 2 The difference between this comparative example and Example 2 is that in Example 2, when preparing the supported iridium-ruthenium oxide catalyst, manganese oxide powder was replaced with an equal weight of γ-MnO2. The remaining steps remained unchanged.

[0061] Following the test method in Example 1, the supported iridium-ruthenium oxide catalyst obtained in this comparative example was tested at 10 mA / cm². 2 The overpotential at the current density was 285 mV. Membrane electrode preparation and testing showed that the catalyst obtained in this example, using an enhanced proton exchange membrane, achieved a current density of 2 A / cm² at 80°C. 2 The electrolysis potential is 1.744V.

[0062] Following the comparative method for the stability of supported iridium-ruthenium oxide catalysts described above, the supported iridium-ruthenium oxide catalyst in Example 2 maintained a stability of 10 mA / cm² after 100 hours of testing. 2 The overpotential at the current density was 255 mV, an increase of only 5 mV compared to the initial 250 mV, indicating that the supported iridium-ruthenium oxide catalyst in this embodiment has excellent stability; the supported iridium-ruthenium oxide catalyst of Comparative Example 2, after 100 h of testing, showed an overpotential of 255 mV at 10 mA / cm². 2 The overpotential at the current density was 300mV, which is 15mV higher than the initial 285mV, indicating that the catalyst is less stable than the catalyst in Example 2.

[0063] Therefore, by comparing the results of Example 1 and Comparative Example 1, as well as Example 2 and Comparative Example 2, it can be seen that, compared with γ-MnO2 as a support, the manganese oxide powder prepared in this invention as a support has better catalytic activity and stability.

[0064] Example 3 Weigh 300 mg of manganese chloride and dissolve it in a mixed solvent of isopropanol and ultrapure water in a volume ratio of 1:1, with a concentration of 15 mg / ml. Stir the mixture ultrasonically for 20 min, then add 1.5 g of sodium nitrate and stir for 40 min. Dry the mixture by rotary evaporation at 80 °C and collect the solid powder. Heat treat the solid powder in a muffle furnace at 400 °C for 30 min. After cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter the product and dry it at 60 °C overnight to obtain manganese oxide powder.

[0065] Weigh 200 mg of the above manganese oxide nanomaterial and disperse it in the above mixed solvent to a concentration of 20 mg / ml. Add 50 mg (0.167 mmol) of iridium trichloride and 30 mg (0.108 mmol) of ruthenium acetate, and stir ultrasonically for 30 min. Then add 1 g of sodium carbonate and 2 g of lithium nitrate, stir for 30 min, and dry by rotary evaporation at 65 °C. Collect the solid powder, heat treat the solid powder in a muffle furnace at 500 °C for 30 min, and after cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter and dry at 60 °C overnight to obtain the supported iridium-ruthenium oxide catalyst.

[0066] In the supported iridium-ruthenium oxide catalyst obtained in this embodiment, the weight ratio of the support is 72%, and the molar ratio of Ir to Ru is 3:2.

[0067] Following the test method in Example 1, the supported iridium-ruthenium oxide catalyst obtained in this example operates at 10 mA / cm². 2 The overpotential at the current density is 302mV, as shown in the attached figure. Figure 5As shown. Membrane electrode preparation and testing indicate that the catalyst obtained in this embodiment, using an enhanced proton exchange membrane, achieves a current density of 2 A / cm² under testing conditions at 80°C. 2 The electrolysis potential is 1.763V.

[0068] Example 4 Weigh 200 mg of the manganese oxide nanomaterials described in Example 3 and disperse them in the above mixed solvent at a concentration of 20 mg / ml. Add 50 mg (0.167 mmol) of iridium trichloride and 30 mg (0.108 mmol) of ruthenium acetate, and stir ultrasonically for 30 min. Then add 1.6 g of sodium carbonate and 2 g of lithium nitrate, stir for 30 min, and dry by rotary evaporation at 65 °C. Collect the solid powder, heat treat the solid powder in a muffle furnace at 500 °C for 30 min, and after cooling, wash the heat-treated product with ultrapure water until the conductivity of the filtrate does not exceed 10 μs / cm. Filter and dry at 60 °C overnight to obtain the supported iridium-ruthenium oxide catalyst.

[0069] In the supported iridium-ruthenium oxide catalyst obtained in this embodiment, the weight ratio of the support is 72%, and the molar ratio of Ir to Ru is 3:2.

[0070] Following the test method in Example 1, the supported iridium-ruthenium oxide catalyst obtained in this example operates at 10 mA / cm². 2 The overpotential at the current density was 290 mV. Membrane electrode preparation and testing showed that the catalyst obtained in this example, using an enhanced proton exchange membrane, achieved a current density of 2 A / cm² at 80°C. 2 The electrolysis potential is 1.755V.

[0071] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing manganese oxide, characterized in that, It is obtained by first heat treatment of a mixture consisting of inorganic manganese salt and first nitrate additive.

2. The method for preparing manganese oxide according to claim 1, characterized in that, The inorganic manganese salt is selected from one or a combination of two or more of manganese nitrate, manganese chloride, manganese sulfate, and manganese carbonate.

3. The method for preparing manganese oxide according to claim 1, characterized in that, The weight ratio of the inorganic manganese salt to the first nitrate auxiliary agent is 1:3-10; The first nitrate additive is selected from one or a combination of two or more of sodium nitrate, potassium nitrate and lithium nitrate.

4. The method for preparing manganese oxide according to claim 1, characterized in that, The temperature of the first heat treatment is 250-600℃, and the time of the first heat treatment is 10min-1h.

5. A supported iridium-ruthenium oxide catalyst, characterized in that, The manganese oxide obtained by the preparation method according to any one of claims 1-4 is used as a support, and the iridium-ruthenium oxide is loaded on the support.

6. The supported iridium-ruthenium oxide catalyst according to claim 5, characterized in that, The support comprises 15-85% of the catalyst by weight, and the molar ratio of iridium to ruthenium in the iridium-ruthenium oxide is 5:5-9:

1.

7. The supported iridium-ruthenium oxide catalyst according to claim 5, characterized in that, The preparation method of the supported iridium-ruthenium oxide catalyst is as follows: the manganese oxide support, iridium source, ruthenium source, second nitrate additive and pore-forming agent are mixed evenly and then subjected to a second heat treatment to obtain the catalyst.

8. The supported iridium-ruthenium oxide catalyst according to claim 7, characterized in that, The iridium source is selected from one or a combination of two or more of iridium tetrachloride, iridium acetate, iridium sulfate, chloroiridium acid, iridium trichloride, and iridium acetate; The ruthenium source is selected from one or a combination of two of ruthenium chloride, ruthenium nitrate, ruthenium sulfate, and ruthenium acetate.

9. The supported iridium-ruthenium oxide catalyst according to claim 7, characterized in that, The weight ratio of the manganese oxide, the pore-forming agent, and the second nitrate auxiliary agent is 1:3-10:5-15; The second nitrate auxiliary agent is selected from one or a combination of two or more of sodium nitrate, potassium nitrate, and lithium nitrate; The pore-forming agent is selected from one or a combination of two or more of carbonates, bicarbonates and carbides.

10. The supported iridium-ruthenium oxide catalyst according to claim 7, characterized in that, The temperature of the second heat treatment is 250-600℃, and the time of the second heat treatment is 10min-1h.

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