Mesoporous iridium oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a mesoporous iridium oxide catalyst and a preparation method and application thereof. The preparation method comprises the following steps: dissolving an iridium-containing compound, nitrate and urea in water, and uniformly stirring and mixing to obtain a mixed solution; carrying out rotary evaporation drying on the mixed solution to obtain a uniform catalyst precursor; calcining the precursor in an air atmosphere to obtain an iridium oxide catalyst; the iridium-containing compound comprises but not limited to one or more of chloroiridic acid, potassium chloroiridate and iridium trichloride, the nitrate comprises but not limited to one or more of sodium nitrate, ammonium nitrate and potassium nitrate, the molar ratio of the urea to the iridium-containing compound in the mixed solution is (1-100): 1, and the molar ratio of the nitrate to the iridium-containing compound is (1-100): 1; the mesoporous iridium oxide prepared by the invention has an ultrahigh specific surface area, is beneficial to exposure of active sites and optimization of mass transfer in a reaction process, and effectively reduces the noble metal loading capacity of a proton exchange membrane electrolyzed water anode catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a mesoporous iridium oxide catalyst and a preparation method and application thereof. Background Art

[0002] Faced with severe climate problems, people urgently need to reduce their dependence on traditional fossil fuels and accelerate the development and utilization of clean energy technologies. Hydrogen energy, which has high energy density and zero pollution characteristics, is an important energy carrier. Green hydrogen energy produced by water electrolysis using electricity generated by renewable energy (such as wind power, solar energy, etc.) will play an important role in the future transformation of the global energy structure. Among various water electrolysis hydrogen production technologies, proton exchange membrane water electrolysis (PEMWE) technology has attracted much attention due to its good gas separation performance, high product purity, high current density, fast response speed and compact structure.

[0003] However, one of the bottlenecks in the development of PEMWE technology is the high cost of catalyst materials, especially the catalyst required for the anode oxygen evolution reaction. The precious metal iridium-based catalyst has become a common anode catalyst for PEMWE due to its high catalytic activity and stability in acidic and oxidizing environments. However, iridium is very scarce and expensive, which to some extent hinders the large-scale commercial application of PEMWE. Therefore, reducing the loading of precious metal iridium at the anode and improving the utilization rate of the catalyst are crucial to achieve large-scale application of PEMWE.

[0004] In order to reduce the loading of precious metals, the iridium-based catalysts are morphologically regulated and nanostructures are constructed, such as nanoparticles, nanoneedles, nanorods, nanosheets, etc. These types of catalysts have a large specific surface area, which is conducive to increasing the exposure of active sites, thereby improving the utilization of precious metals. For example, the team of researcher Xia Qibin synthesized nano-sized IrO by the polypyrrole soft template method. 2 Chatterjee et al. prepared porous iridium nanosheets (npIr x -NS), effectively increasing the electrochemical active area and enhancing the OER activity. However, the above preparation methods are relatively cumbersome and not suitable for mass production. It is still a technical challenge to prepare iridium-based catalysts with high specific surface area and high activity in a simple and efficient way to achieve high activity expression of low-load oxygen evolution catalysts in proton exchange membrane water electrolysis (PEMWE). Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a mesoporous iridium oxide proton exchange membrane water electrolysis anode catalyst.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for preparing a mesoporous iridium oxide proton exchange membrane water electrolysis anode catalyst is provided, comprising:

[0009] The iridium compound, nitrate and urea are dissolved in water, and stirred and mixed to obtain a mixed solution;

[0010] The mixed liquid is dried by rotary evaporation to obtain a uniform catalyst precursor;

[0011] The precursor is calcined in an air atmosphere to obtain an iridium oxide catalyst;

[0012] The iridium-containing compound includes one or more of chloroiridic acid, potassium chloroiridate, and iridium trichloride; the nitrate includes one or more of sodium nitrate, ammonium nitrate, and potassium nitrate; the molar ratio of urea to the iridium-containing compound in the mixed solution is 1 to 100:1, and the molar ratio of nitrate to the iridium-containing compound is 1 to 100:1.

[0013] As a preferred embodiment of the preparation method of the present invention, the catalyst precursor further comprises a solid mixture precursor obtained by directly grinding and mixing evenly, or a solid mixture precursor obtained by ball milling and mixing evenly.

[0014] As a preferred embodiment of the preparation method of the present invention, the ball milling time is 5 to 60 minutes and the rotation speed is 300 to 500 rpm.

[0015] As a preferred embodiment of the preparation method of the present invention, the stirring and mixing time is 1 to 3 hours, and the rotation speed is 400 to 650 rpm.

[0016] As a preferred embodiment of the preparation method of the present invention, the rotary evaporation drying time is 30 to 120 minutes, the water bath temperature is 40 to 70°C, and the condensation temperature is -18 to 0°C.

[0017] As a preferred embodiment of the preparation method of the present invention, the calcination temperature is 300-500°C, and the heating rate is 5-10°C / min.

[0018] As a preferred embodiment of the preparation method of the present invention, the heat treatment time of calcination is 30 to 120 minutes.

[0019] As a preferred embodiment of the preparation method of the present invention, it further includes: after calcination, it is washed with ultrapure water, and then placed in an oven for drying at a temperature of 50-55 °C.

[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide a mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst.

[0021] Another object of the present invention is to overcome the deficiencies in the prior art and provide the application of the catalyst in a proton exchange membrane electrolytic water device.

[0022] Advantages of the present invention:

[0023] 1. The preparation method of the iridium oxide proton exchange membrane electrolytic water anode catalyst with urea coordination-induced pore formation provided by the present invention is simple and has a short preparation process.

[0024] 2. The mesoporous iridium oxide prepared by the present invention has a super high specific surface area, which is beneficial to the exposure of active sites and optimizes the mass transfer during the reaction, effectively reducing the noble metal loading of the proton exchange membrane electrolytic water anode catalyst.

[0025] 3. The catalyst of the present invention exhibits good acidic electrochemical activity, has a simple preparation process, and can meet the basic application requirements of PEMWE. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0027] Figure 1 It is the X-ray diffraction pattern of the super high specific surface area mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst prepared in Example 1 of the present invention;

[0028] Figure 2 It is the N 2 adsorption-desorption isotherm of the super high specific surface area mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst prepared in Example 1 of the present invention;

[0029] Figure 3 It is the BJH pore volume and pore size distribution diagram of the super high specific surface area mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst prepared in Example 1 of the present invention;

[0030] Figure 4 It is the TEM image of the super high specific surface area mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst prepared in Example 1 of the present invention;

[0031] Figure 5 Linear sweep voltammetry curve of the ultra-high specific surface area mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst prepared in Example 1 of the present invention in a 0.5 mol / L sulfuric acid solution.

[0032] Figure 6 Polarization curve of the ultra-high specific surface area mesoporous iridium oxide proton exchange membrane electrolytic water anode catalyst prepared in Example 1 of the present invention in the application of the PEMWE anode. Detailed implementation manners

[0033] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in conjunction with the embodiments of the specification.

[0034] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0035] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not all refer to the same embodiment, nor is it a separate or alternative embodiment that excludes other embodiments.

[0036] The raw materials and reagents used in the present invention are all commercially available unless otherwise specified.

[0037] Example 1

[0038] Weigh 78 mg of urea and 1 g of sodium nitrate and dissolve them in 60 mL of deionized water. Add 1.43 ml of 35 mg Ir ml -1 of an aqueous solution of iridium chloride acid, and stir at 600 rpm for 2 h to obtain a mixed solution. Rotavaporize and dry the mixed solution for 60 min to obtain a precursor powder, where the water bath temperature is 55 °C and the condensation temperature is -15 °C. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere. The heating rate is 5 °C / min -1 , the heat treatment temperature is 450 °C, and the time is 120 min. Wait for it to cool naturally to room temperature, place the solid in an aqueous solution for washing, filter it by suction, and then dry it in an oven at 55 °C to obtain an iridium oxide catalyst.

[0039] Perform X-ray diffraction characterization on the iridium oxide proton exchange membrane electrolytic water anode catalyst of Example 1, and the results are as Figure 1As shown, the diffraction peaks of the prepared catalyst at 2θ of 34.2° and 60.1° correspond to the (101) and (002) crystal planes of rutile IrO 2 crystals, indicating that urea coordination does not change the crystal form of IrO 2 .

[0040] The IrO₂ proton exchange membrane electrolytic water anode catalyst of Example 1 was subjected to N 2 adsorption-desorption test analysis. The specific surface area of the prepared IrO₂ catalyst is as high as 365 m 2 ² -1 , as Figure 2 shown. Its adsorption-desorption curve conforms to the type-IV curve, and according to the BJH pore volume and pore size distribution diagram, the prepared IrO 2 is mesoporous IrO 2 .

[0041] The IrO₂ proton exchange membrane electrolytic water anode catalyst of Example 1 was characterized by TEM. The results are as Figure 3 shown. The black catalyst skeleton and the bright internal area indicate that the catalyst has formed a uniform porous structure.

[0042] The IrO₂ proton exchange membrane electrolytic water anode catalyst of Example 1 was subjected to linear sweep voltammetry test in 0.5 mol / L sulfuric acid solution. The results are as Figure 4 shown. The overpotential of the IrO₂ proton exchange membrane electrolytic water anode catalyst is 262 mV at a current density of 10 mA / cm² when the loading is 0.5 mg / cm², showing better activity than commercial IrO cata. ₂ -2 catalysts. -2 2

[0043] The IrO₂ catalyst of Example 1 was used as the anode (loading 0.32 mg / cm²), and the Pt / C catalyst (loading 0.5 mg / cm², 40 wt% Pt / C) was used as the cathode to assemble a proton exchange membrane electrolytic water device. The constant current polarization curve was obtained by testing at 80 °C. The results are as Ir shown. When the electrolytic device assembled with the IrO₂ as the anode catalyst provides a current density of 2 A / cm², the decomposition voltage only needs 1.74 V. When the decomposition voltage reaches 1.86 V, a large current density of 3 A / cm² can be provided, and the activity is better than that of commercial IrO -2 ₂ Pt / C catalysts. -2 Figure 5 -2 -2 2

[0044] Example 2

[0045] ​​​​​​​Weigh 78 mg of urea and 2 g of sodium nitrate, dissolve them in 60 mL of deionized water, add 1.43 ml of an aqueous solution of iridium chloride acid with a concentration of 35 mg Ir ml -1 , stir at 600 rpm for 2 h to obtain a mixed solution. Rotavaporize and dry the mixed solution for 60 min to obtain a precursor powder, where the water bath temperature is 55 °C and the condensation temperature is -15 °C. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere, with a heating rate of 5 °C min -1 , the heat treatment temperature is 450 °C, and the time is 120 min. Wait for it to cool naturally to room temperature, wash the solid in an aqueous solution, filter it by suction, and then dry it in an oven at 55 °C to obtain an iridium oxide catalyst.

[0046] Perform three-electrode activity and stability tests on the iridium oxide proton exchange membrane electrolytic water anode catalyst in Example 2, and the results are similar to those in Example 1.

[0047] Example 3

[0048] Weigh 78 mg of urea and 1 g of sodium nitrate, dissolve them in 60 mL of deionized water, add 1.43 ml of an aqueous solution of iridium chloride acid with a concentration of 35 mg Ir ml -1 , stir at 600 rpm for 2 h to obtain a mixed solution. Rotavaporize and dry the mixed solution for 60 min to obtain a precursor powder, where the water bath temperature is 45 °C and the condensation temperature is -15 °C. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere, with a heating rate of 5 °C min -1 , the heat treatment temperature is 450 °C, and the time is 120 min. Wait for it to cool naturally to room temperature, wash the solid in an aqueous solution, filter it by suction, and then dry it in an oven at 55 °C to obtain an iridium oxide catalyst.

[0049] Perform three-electrode activity and stability tests on the iridium oxide proton exchange membrane electrolytic water anode catalyst in Example 3, and the results are similar to those in Example 1.

[0050] Example 4

[0051] Weigh 78 mg of urea and 1 g of sodium nitrate, dissolve them in 60 mL of deionized water, add 1.43 ml of an aqueous solution of iridium chloride acid with a concentration of 35 mg Ir ml -1 , stir at 600 rpm for 2 h to obtain a mixed solution. Rotavaporize and dry the mixed solution for 60 min to obtain a precursor powder, where the water bath temperature is 65 °C and the condensation temperature is -15 °C. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere, with a heating rate of 5 °C min -1 , the heat treatment temperature is 450 °C, and the time is 120 min. Wait for it to cool naturally to room temperature, wash the solid in an aqueous solution, filter it by suction, and then dry it in an oven at 55 °C to obtain an iridium oxide catalyst.

[0052] The three-electrode activity and stability tests were carried out on the iridium oxide proton exchange membrane electrolytic water anode catalyst of Example 4, and the results were similar to those of Example 1.

[0053] Example 5

[0054] Weigh 78 mg of urea, 1 g of sodium nitrate and 125.69 mg of potassium iridium chloride into an agate mortar, mix and grind for 10 min to obtain the precursor powder. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere, with a heating rate of 5 °C / min -1 , the heat treatment temperature is 450 °C, and the time is 120 min. Wait for it to cool naturally to room temperature, wash the solid in an aqueous solution, filter it by suction, and then dry it in an oven at 55 °C to obtain the iridium oxide catalyst.

[0055] The three-electrode activity and stability tests were carried out on the iridium oxide proton exchange membrane electrolytic water anode catalyst of Example 5, and the results were similar to those of Example 1.

[0056] Example 6

[0057] Weigh 78 mg of urea, 1 g of sodium nitrate and 84.04 mg of iridium trichloride into an agate mortar, mix and grind for 10 min to obtain the precursor powder. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere, with a heating rate of 5 °C / min -1 , the heat treatment temperature is 450 °C, and the time is 120 min. Wait for it to cool naturally to room temperature, wash the solid in an aqueous solution, filter it by suction, and then dry it in an oven at 55 °C to obtain the iridium oxide catalyst.

[0058] The three-electrode activity and stability tests were carried out on the iridium oxide proton exchange membrane electrolytic water anode catalyst of Example 6, and the results were similar to those of Example 1.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that no urea was added. Specifically:

[0061] Weigh 1 g of sodium nitrate and dissolve it in 60 mL of deionized water, add 1.43 ml of 35 mg Ir ml -1 of aqueous solution of iridic acid, stir at 600 rpm for 2 h to obtain a mixed solution. Rotavaporize and dry the mixed solution for 60 min to obtain the precursor powder, where the water bath temperature is 55 °C and the condensation temperature is -15 °C. Place the precursor in a muffle furnace and perform heat treatment on it in an air atmosphere, with a heating rate of 5 °C / min -1, the heat treatment temperature was 450 °C and the time was 120 min. After natural cooling to room temperature, the solid was washed in an aqueous solution, filtered by suction, and then dried in an oven at 55 °C to obtain an iridium oxide catalyst.

[0062] The iridium oxide catalyst prepared in this comparative example had a loading of 0.5 mg cata. cm -2 and the overpotential at a current density of 10 mA cm -2 was 286 mV, 24 mV higher than that of Example 1.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 was that the calcination temperature was 350 °C. Specifically:

[0065] 78 mg of urea and 1 g of sodium nitrate were weighed and dissolved in 60 mL of deionized water. 1.43 ml of a 35 mg Ir ml -1 aqueous solution of chloroiridic acid was added, and the mixture was stirred at 600 rpm for 2 h to obtain a mixed solution. The mixed solution was rotary evaporated and dried for 60 min to obtain a precursor powder, where the water bath temperature was 55 °C and the condensation temperature was -15 °C. The precursor was placed in a muffle furnace and heat-treated in an air atmosphere at a heating rate of 5 °C min -1 , the heat treatment temperature was 350 °C and the time was 120 min. After natural cooling to room temperature, the solid was washed in an aqueous solution, filtered by suction, and then dried in an oven at 55 °C to obtain an iridium oxide catalyst.

[0066] The iridium oxide catalyst prepared in this comparative example had a loading of 0.5 mg cata. cm -2 and the overpotential at a current density of 10 mA cm -2 was 304 mV, 42 mV higher than that of Example 1.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 1 was that the calcination temperature was 550 °C. Specifically:

[0069] 78 mg of urea and 1 g of sodium nitrate were weighed and dissolved in 60 mL of deionized water. 1.43 ml of a 35 mg Ir ml -1 aqueous solution of chloroiridic acid was added, and the mixture was stirred at 600 rpm for 2 h to obtain a mixed solution. The mixed solution was rotary evaporated and dried for 60 min to obtain a precursor powder, where the water bath temperature was 55 °C and the condensation temperature was -15 °C. The precursor was placed in a muffle furnace and heat-treated in an air atmosphere at a heating rate of 5 °C min -1, the heat treatment temperature was 550 °C and the time was 120 min. After natural cooling to room temperature, the solid was washed in an aqueous solution, filtered by suction, and then dried in an oven at 55 °C to obtain an iridium oxide catalyst.

[0070] The iridium oxide catalyst prepared in this comparative example had a loading of 0.5 mg cata. cm -2 The overpotential at a current density of 10 mA cm -2 was 322 mV, which was 60 mV higher than that in Example 1.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing a mesoporous iridium oxide catalyst, characterized in that: include, The iridium compound, nitrate and urea are dissolved in water, and stirred and mixed to obtain a mixed solution; The mixed liquid is dried by rotary evaporation to obtain a uniform catalyst precursor; The precursor is calcined in an air atmosphere to obtain an iridium oxide catalyst; The iridium-containing compound includes one or more of chloroiridic acid, potassium chloroiridate, and iridium trichloride; the nitrate includes one or more of sodium nitrate, ammonium nitrate, and potassium nitrate; the molar ratio of urea to the iridium-containing compound in the mixed solution is 1 to 100:1, and the molar ratio of nitrate to the iridium-containing compound is 1 to 100:

1.

2. The preparation method according to claim 1, characterized in that: The catalyst precursor also includes a solid mixture precursor obtained by directly grinding and mixing evenly, or a solid mixture precursor obtained by ball milling and mixing evenly.

3. The preparation method according to claim 1 or 2, characterized in that: The ball milling time is 5 to 60 minutes, and the rotation speed is 300 to 500 rpm.

4. The preparation method according to claim 1, characterized in that: The stirring and mixing time is 1 to 3 hours, and the rotation speed is 400 to 650 rpm.

5. The preparation method according to claim 1, characterized in that: The rotary evaporation drying time is 30 to 120 minutes, the water bath temperature is 40 to 70° C., and the condensation temperature is -18 to 0° C.

6. The preparation method according to claim 1, characterized in that: The calcination temperature is 300-500° C., and the heating rate is 5-10° C. / min.

7. The preparation method according to claim 1, characterized in that: The heat treatment time of the calcination is 30 to 120 minutes.

8. The preparation method according to claim 1, characterized in that: The calcination step further includes washing with ultrapure water, and then drying in an oven at a temperature of 50-55°C.

9. A mesoporous iridium oxide anode catalyst for proton exchange membrane water electrolysis obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the catalyst according to claim 9 in a proton exchange membrane water electrolysis device.

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