Multi-stage self-supporting MOF (Metal Organic Framework)-based electrolyzed water catalyst and preparation method thereof
By using femtosecond laser to prepare three-dimensional micro/nanostructured base materials and grow MOF nanosheets, the preparation complexity and insufficient catalytic performance of MOF-based self-grown catalysts were solved, efficient mass transfer channels and catalytic stability were achieved, and it has potential for industrial application.
Patent Information
- Application Number
- CN202510613486.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-13
- Publication Date
- 2025-09-19
AI Technical Summary
Existing MOF-based self-growing catalysts have problems such as complex preparation process, difficulty in high-efficiency and high-precision processing, low density of catalytic active sites, and insufficient catalytic performance.
A femtosecond laser was used to vertically irradiate the surface of the substrate material to prepare a substrate material with a three-dimensional micro/nanostructure, and MOF nanosheets were grown on its surface. A multi-stage self-supporting MOF-based water electrolysis catalyst was prepared through a co-deposition reaction.
It achieves high specific surface area and efficient mass transfer channels, increases the density of catalytic active sites, and does not require a binder. It exhibits good catalytic stability and catalytic activity for water electrolysis and has prospects for industrial application.
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Figure CN120666371A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of laser application technology, and in particular to a multi-stage self-supporting MOF-based water electrolysis catalyst and a preparation method thereof. Background Art
[0002] As a crucial component of renewable clean energy systems, hydrogen energy occupies a key position in clean energy conversion due to its high energy density and environmental friendliness. Electrochemical water splitting is recognized as one of the most promising hydrogen production technologies. Its reaction process involves two key half-reactions: the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). The slow kinetics of the OER process make the development of efficient and stable OER electrocatalysts crucial for the current development of water electrolysis technology.
[0003] In recent years, metal-organic framework (MOF) materials have attracted widespread attention in the field of water electrolysis due to their unique pore structure, high specific surface area and highly dispersed metal active sites. For example, some scholars have proposed to improve the hydrogen evolution activity by growing ultrasmall metal nanoparticles on MOF nanosheets [Wang M, Xu Y, Peng CK, et al. Site-specified two-dimensional heterojunction of Ptnanoparticles / metal–organic frameworks for enhanced hydrogen evolution [J]. Journal of the American Chemical Society, 2021, 143(40): 16512-16518.].
[0004] However, existing MOF materials are mostly in powder form and have poor intrinsic conductivity. They need to be fixed on a conductive substrate with the help of an adhesive. This will lead to problems such as active site coverage, electrolyte mass transfer obstruction, and increased interfacial electron transfer impedance, thereby reducing catalytic performance. Therefore, directly growing catalysts on a stable conductive substrate without the need for an adhesive is expected to become an effective way to improve the catalytic activity and stability of MOF-based electrocatalysts, further promoting their large-scale promotion and use in industrial production. For example, some scholars designed a self-supporting hollow Janus structure NiCoP / P-MoS2 heterojunction electrode and applied it as a high-performance electrocatalyst for alkaline HER [Luo Q, Lv Y, Zhang P, et al. Interface engineering of hollow Janus-structured NiCoP / P-MoS2 heterojunction as self-supported electrode enables boosted alkaline hydrogen evolution reaction [J]. Journal of Colloid and Interface Science, 2025, 684: 668-677.].
[0005] Currently, MOF-based self-grown catalysts still face challenges such as complex preparation processes, difficulty in high-efficiency and high-precision processing, low density of catalytic active sites, and insufficient catalytic performance. Designing and manipulating the surface microstructure and chemical properties of the substrate material to further increase the active material loading and catalytic activity has become a key scientific issue in the field of water electrolysis. Summary of the Invention
[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a multi-stage self-supporting MOF-based water electrolysis catalyst and a preparation method thereof, so as to solve the problems of existing MOF-based self-growing catalysts, such as complex preparation process, difficulty in high-efficiency and high-precision processing, low density of catalytic active sites, and insufficient catalytic performance.
[0007] The technical solution of the present invention to solve the above technical problems is as follows:
[0008] The first object of the present invention is to provide a method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst, comprising the following steps:
[0009] S1: Using femtosecond laser to vertically irradiate the substrate surface, a substrate with three-dimensional micro / nanostructure is prepared;
[0010] S2: MOF nanosheets are grown on the surface of the base material with three-dimensional micro / nano structure obtained in S1.
[0011] The beneficial effects of the present invention are as follows: the preparation method of the present invention has the advantages that the raw materials do not contain precious metals, the product morphology is controllable, the production process is simple, and large-scale and efficient processing can be performed, and it has certain industrial application prospects.
[0012] Furthermore, S1 is specifically implemented by the following steps:
[0013] S11: Fix the substrate material to be processed on the translation stage, focus the femtosecond laser beam on the surface of the substrate material to be processed through the objective lens, control the translation stage to move and perform laser scanning, and complete the femtosecond laser processing;
[0014] S12: The material obtained by femtosecond laser processing in S11 is cleaned with anhydrous ethanol and dried to obtain a base material with a three-dimensional micro / nano structure.
[0015] Furthermore, the substrate material includes a metal substrate or a carbon substrate.
[0016] Furthermore, the base material area is 5×5 mm 2 ~20×50mm 2 .
[0017] Furthermore, the base material in S1 is subjected to crystal surface polishing before femtosecond laser processing, and then its surface is cleaned by ultrasound, and finally dried to complete the pre-treatment.
[0018] The beneficial effect of adopting the above-mentioned further technical solution is that the present invention effectively removes impurities such as oil stains and residues on the surface of the base material through mirror polishing and ultrasonic cleaning, so as to facilitate subsequent femtosecond laser processing.
[0019] Furthermore, the objective lens parameters of the laser scanning in S11 are 5 to 20 times, the scanning speed is 200 to 2000 μm / s, the scanning spacing is 5 to 30 μm, the laser repetition frequency is 500 Hz to 20 kHz, and the laser flux is 0.5 to 150 J / cm 2 ;
[0020] The drying temperature in S12 is 20 to 40° C. and the drying time is 8 to 24 hours.
[0021] Furthermore, high-pressure nitrogen gas is used to blow away chips during femtosecond laser processing.
[0022] Furthermore, S2 is specifically implemented by the following steps:
[0023] S21: mixing a mixed aqueous solution of a cobalt salt and a copper salt with an aqueous solution of 2-methylimidazole to prepare a co-precipitation reaction solution;
[0024] S22: immersing the substrate material having the three-dimensional micro / nano structure obtained in S1 into the co-deposition reaction solution obtained in S21 to perform a co-deposition reaction;
[0025] S23: The base material after the co-deposition reaction in S22 is washed with anhydrous ethanol and then dried to prepare a multi-stage self-supporting MOF-based water electrolysis catalyst.
[0026] Furthermore, the cobalt salt in S21 is at least one of cobalt chloride hexahydrate, cobalt nitrate hexahydrate and cobalt sulfate heptahydrate;
[0027] The copper salt is at least one of copper chloride dihydrate, copper nitrate trihydrate and copper sulfate pentahydrate;
[0028] The concentration of cobalt salt is 1-50 mmol / L, the concentration of copper salt is 1-50 mmol / L, the concentration of 2-methylimidazole is 10-500 mmol / L, and the volume ratio of the mixed aqueous solution composed of cobalt salt and copper salt to the 2-methylimidazole aqueous solution is 1:(0.5-2).
[0029] Furthermore, the molar concentration ratio of cobalt salt to copper salt in the mixed aqueous solution composed of cobalt salt and copper salt is 1:(0.1-2); the molar concentration ratio of total metal salt in the mixed aqueous solution composed of cobalt salt and copper salt to 2-methylimidazole in the 2-methylimidazole aqueous solution is 1:(5-20).
[0030] Furthermore, the temperature of the co-deposition reaction in S22 is 20 to 50° C. and the time is 2 to 10 h;
[0031] The drying temperature in S23 is 20 to 40° C. and the drying time is 8 to 24 hours.
[0032] The second object of the present invention is to provide a multi-stage self-supporting MOF-based water electrolysis catalyst prepared by the above-mentioned preparation method.
[0033] The beneficial effects of the present invention are as follows: the multi-stage self-supporting MOF-based water electrolysis catalyst prepared by the present invention has the characteristics of no need for adhesives, high specific surface area and efficient mass transfer channels, and exhibits excellent catalytic performance and stability.
[0034] The third object of the present invention is to provide the use of the above-mentioned multi-stage self-supporting MOF-based water electrolysis catalyst in the electrocatalytic oxygen evolution reaction.
[0035] The beneficial effects of the present invention are as follows: the multi-stage self-supporting MOF-based water electrolysis catalyst prepared by the present invention exhibits good water electrolysis catalytic activity and stability in alkaline electrolyte, and can be effectively applied to electrocatalytic oxygen evolution reaction.
[0036] The present invention has the following beneficial effects:
[0037] (1) The present invention uses femtosecond laser processing of high-curvature substrate materials with three-dimensional micro / nanostructures, which not only provides abundant nucleation sites for the growth of bimetallic MOF nanosheets, but also achieves precise control of the nanosheet size by reducing the nucleation energy barrier.
[0038] (2) The MOF nanosheets with rich pore structure in the multi-level self-supporting MOF-based water electrolysis catalyst prepared by the present invention significantly increase the density of catalytic active sites and promote the rapid mass transfer process of the electrolyte.
[0039] (3) The three-dimensional multi-level porous structure in the multi-level self-supporting MOF-based water electrolysis catalyst prepared by the present invention gives the catalyst a high specific surface area, provides abundant active sites for the catalytic reaction, and significantly improves the catalytic activity; promotes rapid electrolyte transmission, enhances the contact between the electrocatalyst and the electrolyte, promotes charge and ion transfer, and optimizes the mass transfer kinetics process.
[0040] (4) The multi-stage self-supporting MOF-based water electrolysis catalyst prepared by the present invention does not require a binder, can effectively suppress the problem of easy shedding of active substances during the actual catalytic process, and exhibits good catalytic stability.
[0041] (5) The preparation method of the present invention has the advantages of raw materials containing no precious metals, controllable product morphology, simple production process, and large-scale and efficient processing, and has certain industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0042] Figure 1 A process flow chart of a multi-stage self-supporting MOF-based water electrolysis catalyst prepared according to an embodiment of the present invention;
[0043] Figure 2 Figures 2 and 3 are scanning electron microscope images of the three-dimensional micro / nanostructure prepared in Comparative Example 2 of the present invention, and figures ad are scanning electron microscope images of different proportions or regions;
[0044] Figure 3 ac are scanning electron micrographs of the multi-stage self-supporting MOF-based water electrolysis catalyst prepared in Example 1 of the present invention, and ac are scanning electron micrographs of different regions or proportions;
[0045] Figure 4 Transmission electron microscopy (TEM) images and related elemental analysis of CoCu bimetallic MOF nanosheets peeled from the multi-stage self-supporting MOF-based water electrolysis catalyst prepared in accordance with the present invention, wherein a is a TEM image and b is a related elemental analysis image;
[0046] Figure 5 This is a scanning electron microscope image of the MOF-based water electrolysis catalyst prepared in Comparative Example 3;
[0047] Figure 6 This is the contact angle test result diagram in the test example;
[0048] Figure 7 is the linear voltammetric curve in the test example;
[0049] Figure 8 This is the electrochemical resistance test diagram in the test example;
[0050] Figure 9 This is a constant current stability test diagram of the self-supporting MOF-based water electrolysis catalyst prepared in the embodiment of the test example. The attached figure in the figure is its linear voltammetry curve before and after 2000 cycles of cyclic voltammetry test. DETAILED DESCRIPTION
[0051] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not intended to limit the scope of the invention. In the embodiments, if specific conditions are not specified, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.
[0052] Example 1:
[0053] A method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst (process flow chart as shown in FIG Figure 1 ), comprising the following steps:
[0054] Step 1: 10×10mm 2 The quaternary CoCrFeNi high entropy alloy is optically polished to a mirror finish, ensuring that its surface roughness is less than 5 nanometers.
[0055] Step 2: Use deionized water or anhydrous ethanol to ultrasonically clean the polished high-entropy alloy obtained in step 1. The ultrasonic frequency of the ultrasonic cleaner is 80 kHz and the cleaning time is 5 minutes to obtain a clean surface polished material.
[0056] Step 3: Femtosecond laser processing of micro / nano composite structures
[0057] (1) Set the laser parameters as follows: central wavelength 800 nm, pulse duration 35 fs, and repetition frequency 1 kHz;
[0058] (2) Adjust the aperture size so that the spot size of the femtosecond laser before focusing is 5 mm;
[0059] (3) Adjust the polarizer and half-wave plate combination to adjust the laser energy to 40.10 J / cm 2 ;
[0060] (4) Using a five-fold objective lens (NA = 0.15) to focus the femtosecond laser, the upper and lower positions of the processed sample are adjusted so that the laser is focused on the surface of the high-entropy alloy;
[0061] (5) The computer controls the platform to move in two perpendicular directions. The specific parameters of the translation stage motion are set as follows: scanning speed of 500 μm / s and scanning spacing of 30 μm. High-pressure nitrogen gas is used to blow away chips during the entire processing process.
[0062] (6) The high entropy alloy sample after femtosecond laser processing was ultrasonically cleaned with deionized water and anhydrous ethanol and dried at 30°C for 12 h to obtain a high entropy alloy with a three-dimensional micro-conical micro / nano structure. The morphology of the structure measured under a scanning electron microscope is as follows: Figure 2 shown.
[0063] Step 4: Synthesis of bimetallic MOF nanosheets by co-deposition
[0064] (1) Weigh 0.931 g of cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and 0.193 g of copper nitrate trihydrate [Cu(NO3)2·3H2O] (the molar ratio of Co / Cu is 4:1), dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 1; weigh 2.628 g of 2-methylimidazole (2-MeIm) and dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 2. Solution 1 and solution 2 are mixed and stirred for 5 min to obtain a co-precipitation reaction system solution;
[0065] (2) The high entropy alloy with three-dimensional micro-conical micro / nanostructure was immersed in the mixed solution at a 45° tilt angle to ensure that the number of deposited CoCu bimetallic MOF nanosheets was sufficient but not enough to bury each other, resulting in coverage of active sites. The co-deposition reaction was then allowed to stand in a vacuum drying oven at room temperature for 3 h.
[0066] (3) The high-entropy alloy sample after the co-deposition reaction was rinsed with anhydrous ethanol for 3 minutes to remove the physically adsorbed impurities on the surface, and then dried in a vacuum drying oven at 30°C for 12 hours to prepare a multi-stage self-supporting MOF-based water electrolysis catalyst.
[0067] The morphology of the multi-stage self-supporting MOF-based water electrolysis catalyst sample prepared in this embodiment was measured under a scanning electron microscope. Figure 3 The morphology and element distribution measured under a transmission electron microscope are shown in Figure 4 shown.
[0068] Example 2:
[0069] A method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst comprises the following steps:
[0070] Step 1: 10×10mm 2 The quaternary CoCrFeNi high entropy alloy is optically polished to a mirror finish, ensuring that its surface roughness is less than 5 nanometers.
[0071] Step 2: Use deionized water or anhydrous ethanol to ultrasonically clean the polished high-entropy alloy obtained in step 1. The ultrasonic frequency of the ultrasonic cleaner is 80 kHz and the cleaning time is 5 minutes to obtain a clean surface polished material.
[0072] Step 3: Femtosecond laser processing of micro / nano composite structures
[0073] (1) Set the laser parameters as follows: central wavelength 800 nm, pulse duration 35 fs, and repetition frequency 10 kHz;
[0074] (2) Adjust the aperture size so that the spot size of the femtosecond laser before focusing is 5 mm;
[0075] (3) Adjust the polarizer and half-wave plate combination to adjust the laser energy to 53.46 J / cm 2 ;
[0076] (4) Using a ten-fold objective lens to focus the femtosecond laser, adjust the upper and lower positions of the processed sample so that the laser is focused on the surface of the high-entropy alloy;
[0077] (5) The computer controls the platform to move in two perpendicular directions. The specific parameters of the translation stage motion are set as follows: scanning speed of 800 μm / s and scanning spacing of 20 μm. High-pressure nitrogen gas is used to blow away chips during the entire processing process.
[0078] (6) The high entropy alloy sample after femtosecond laser processing was ultrasonically cleaned with deionized water and anhydrous ethanol and dried at 30°C for 12 h to obtain a high entropy alloy with a three-dimensional micro-conical micro / nanostructure.
[0079] Step 4: Synthesis of bimetallic MOF nanosheets by co-deposition
[0080] (1) Weigh 0.931 g of cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and 0.772 g of copper nitrate trihydrate [Cu(NO3)2·3H2O] (the molar ratio of Co / Cu is 1:1), dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 1; weigh 4.205 g of 2-methylimidazole (2-MeIm) and dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 2; mix solution 1 and solution 2, and continue stirring for 5 min to obtain a co-precipitation reaction system solution;
[0081] (2) The high entropy alloy with three-dimensional micro-conical micro / nanostructure was immersed in the mixed solution at a 45° tilt angle to ensure that the number of deposited CoCu bimetallic MOF nanosheets was sufficient but not enough to bury each other, resulting in coverage of active sites. The co-deposition reaction was then allowed to stand in a vacuum drying oven at room temperature for 5 h.
[0082] (3) The high-entropy alloy sample after the co-deposition reaction was rinsed with anhydrous ethanol for 3 minutes to remove surface physically adsorbed impurities, and then dried in a vacuum drying oven at 30°C for 16 hours to prepare a multi-stage self-supporting MOF-based water electrolysis catalyst.
[0083] Example 3:
[0084] A method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst comprises the following steps:
[0085] Step 1: 10×10mm 2 The quaternary CoCrFeNi high entropy alloy is optically polished to a mirror finish, ensuring that its surface roughness is less than 5 nanometers.
[0086] Step 2: Use deionized water or anhydrous ethanol to ultrasonically clean the polished high-entropy alloy obtained in step 1. The ultrasonic frequency of the ultrasonic cleaner is 80 kHz and the cleaning time is 5 minutes to obtain a clean surface polished material.
[0087] Step 3: Femtosecond laser processing of micro / nano composite structures
[0088] (1) The laser parameters were set as follows: central wavelength 800 nm, pulse duration 35 fs, and repetition frequency 15 kHz;
[0089] (2) Adjust the aperture size so that the spot size of the femtosecond laser before focusing is 5 mm;
[0090] (3) Adjust the polarizer and half-wave plate combination to adjust the laser energy to 66.83 J / cm 2 ;
[0091] (4) Using a five-fold objective lens (NA = 0.15) to focus the femtosecond laser, the upper and lower positions of the processed sample are adjusted so that the laser is focused on the surface of the high-entropy alloy;
[0092] (5) The computer controls the platform to move in two perpendicular directions. The specific parameters of the translation stage motion are set as follows: scanning speed of 1000 μm / s and scanning spacing of 10 μm. High-pressure nitrogen gas is used to blow away chips during the entire processing process.
[0093] (6) The high entropy alloy sample after femtosecond laser processing was ultrasonically cleaned with deionized water and anhydrous ethanol and dried at 30°C for 12 h to obtain a high entropy alloy with a three-dimensional micro-conical micro / nanostructure.
[0094] Step 4: Synthesis of bimetallic MOF nanosheets by co-deposition
[0095] (1) Weigh 0.466 g of cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and 0.193 g of copper nitrate trihydrate [Cu(NO3)2·3H2O] (the molar ratio of Co / Cu is 2:1), dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 1; weigh 1.577 g of 2-methylimidazole (2-MeIm) and dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 2. Solution 1 and solution 2 are mixed and stirred for 5 min to obtain a co-precipitation reaction system solution;
[0096] (2) The high entropy alloy with three-dimensional micro-conical micro / nanostructure was immersed in the mixed solution at a 45° tilt angle to ensure that the number of deposited CoCu bimetallic MOF nanosheets was sufficient but not enough to bury each other, resulting in coverage of active sites. The co-deposition reaction was then allowed to stand in a vacuum drying oven at room temperature for 8 h.
[0097] (3) The high-entropy alloy sample after the co-deposition reaction was rinsed with anhydrous ethanol for 3 minutes to remove the physically adsorbed impurities on the surface, and then dried in a vacuum drying oven at 30°C for 24 hours to prepare a multi-stage self-supporting MOF-based water electrolysis catalyst.
[0098] Comparative Example 1:
[0099] A method for preparing a polished catalyst material comprises the following steps:
[0100] Step 1: 10×10mm 2 The quaternary CoCrFeNi high entropy alloy is optically polished to a mirror finish, ensuring that its surface roughness is less than 5 nanometers.
[0101] Step 2: Use deionized water or anhydrous ethanol to ultrasonically clean the polished high-entropy alloy obtained in step 1. The ultrasonic frequency of the ultrasonic cleaner is 80 kHz and the cleaning time is 5 minutes to obtain a clean polished base material.
[0102] Comparative Example 2:
[0103] A method for preparing a catalyst having a three-dimensional micro / nano structure comprises the following steps:
[0104] Step 1: 10×10mm 2 The quaternary CoCrFeNi high entropy alloy is optically polished to a mirror finish, ensuring that its surface roughness is less than 5 nanometers.
[0105] Step 2: Use deionized water or anhydrous ethanol to ultrasonically clean the polished high-entropy alloy obtained in step 1. The ultrasonic frequency of the ultrasonic cleaner is 80 kHz and the cleaning time is 5 minutes to obtain a clean surface polished material.
[0106] Step 3: Femtosecond laser processing of micro / nano composite structures
[0107] (1) Set the laser parameters as follows: central wavelength 800 nm, pulse duration 35 fs, and repetition frequency 1 kHz;
[0108] (2) Adjust the aperture size so that the spot size of the femtosecond laser before focusing is 5 mm;
[0109] (3) Adjust the polarizer and half-wave plate combination to adjust the laser energy to 40.10 J / cm 2 ;
[0110] (4) Using a five-fold objective lens (NA = 0.15) to focus the femtosecond laser, the upper and lower positions of the processed sample are adjusted so that the laser is focused on the surface of the high-entropy alloy;
[0111] (5) The computer controls the platform to move in two perpendicular directions. The specific parameters of the translation stage motion are set as follows: scanning speed of 500 μm / s and scanning spacing of 30 μm. High-pressure nitrogen gas is used to blow away chips during the entire processing process.
[0112] (6) The high entropy alloy sample after femtosecond laser processing was ultrasonically cleaned with deionized water and anhydrous ethanol and dried at 30°C for 12 h to obtain a high entropy alloy with a three-dimensional micro-conical micro / nanostructure.
[0113] Comparative Example 3:
[0114] A method for preparing a MOF-based water electrolysis catalyst without femtosecond laser processing comprises the following steps:
[0115] A method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst (process flow chart as shown in FIG Figure 1 ), comprising the following steps:
[0116] Step 1: 10×10mm 2 The quaternary CoCrFeNi high entropy alloy is optically polished to a mirror finish, ensuring that its surface roughness is less than 5 nanometers.
[0117] Step 2: Use deionized water or anhydrous ethanol to ultrasonically clean the polished high-entropy alloy obtained in step 1. The ultrasonic frequency of the ultrasonic cleaner is 80 kHz and the cleaning time is 5 minutes to obtain a clean surface polished material.
[0118] Step 3: Synthesis of bimetallic MOF nanosheets by co-deposition
[0119] (1) Weigh 0.931 g of cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and 0.193 g of copper nitrate trihydrate [Cu(NO3)2·3H2O] (the molar ratio of Co / Cu is 4:1), dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 1; weigh 2.628 g of 2-methylimidazole (2-MeIm) and dissolve them in 80 mL of deionized water, and stir them magnetically for 20 min until they are completely dissolved to obtain solution 2. Solution 1 and solution 2 are mixed and stirred for 5 min to obtain a co-precipitation reaction system solution;
[0120] (2) The surface polished material obtained in step 2 was immersed in the mixed solution at an inclination angle of 45° to ensure that the number of deposited CoCu bimetallic MOF nanosheets was sufficient but not enough to bury each other, resulting in coverage of active sites, and then the co-deposition reaction was allowed to stand at room temperature in a vacuum drying oven for 3 h;
[0121] (3) The high entropy alloy sample after the co-deposition reaction was rinsed with anhydrous ethanol for 3 minutes to remove the physically adsorbed impurities on the surface, and then dried in a vacuum drying oven at 30°C for 12 hours to obtain a MOF-based water electrolysis catalyst.
[0122] The morphology of the MOF-based water electrolysis catalyst obtained in this comparative example was measured under a scanning electron microscope. Figure 5 The results show that although they have similar flower-like structures, the size of the self-grown MOF nanosheets in Comparative Example 3 is much larger than the MOF nanosheets grown on the high-curvature substrate processed by femtosecond laser in Example 1 of the present invention. The results show that the substrate with a three-dimensional micro-conical micro / nanostructure processed by femtosecond laser in the present invention not only provides abundant nucleation sites for the growth of MOF nanosheets, but also achieves precise control of the nanosheet size by reducing the nucleation energy barrier.
[0123] Test example:
[0124] (1) The contact angle test was performed on the catalysts prepared in Example 1 and Comparative Examples 1-3. The experimental results are as follows: Figure 6 shown.
[0125] It can be seen that the polished substrate material prepared in Comparative Example 1 exhibits near-hydrophobic properties, the three-dimensional micro / nanostructure (53.7°±2.7°) prepared by femtosecond laser in Comparative Example 2 and the substrate self-grown MOF nanosheet (41.8°±2.0°) constructed by co-deposition method in Comparative Example 3 significantly improve the hydrophilicity of the material, and the multi-stage self-supporting MOF-based electrolytic water catalyst prepared by femtosecond laser processing and co-deposition method in Example 1 of the present invention exhibits super-hydrophilicity (10.9°±1.2°). The above results show that the multi-stage self-supporting MOF-based electrolytic water catalyst prepared in the embodiment of the present invention has good wettability, can promote rapid electrolyte transmission, enhance the contact between the electrocatalyst and the electrolyte, promote charge and ion transfer, and optimize the mass transfer kinetics process.
[0126] (2) Example 1, Comparative Examples 1-3, and IrO2 containing noble metals (deposited on a substrate with a three-dimensional micro-cone micro / nano structure, with a loading of 2 mg cm -2 , purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) as a catalyst, and a standard three-electrode system was used for electrochemical performance testing. The specific experimental parameters were designed as follows: a graphite rod was used as the counter electrode, Hg / HgO (1.0 mol / L KOH) was used as the reference electrode, the sample to be tested was used as the working electrode, and the electrolyte was a 1.0 mol / L KOH solution. Before the test, the automatic iR compensation function (compensation degree 100%) was used to eliminate the influence of solution resistance. All test potentials were calibrated to the reversible hydrogen electrode (RHE) using the Nernst equation: E RHE =E (Hg / HgO) +0.059×pH+0.098.
[0127] The experimental results are as follows Figure 7-Figure 9 shown.
[0128] like Figure 7 The linear voltammetric curve is shown. The multi-stage self-supporting MOF-based water electrolysis catalyst prepared in Example 1 of the present invention has the lowest overpotential. -2 When the overpotential of the material is only 281mV, it is better than the IrO2 catalyst containing precious metals.
[0129] like Figure 8 The results of electrochemical impedance spectroscopy (EIS) tests show that the multi-level self-supporting MOF-based water electrolysis catalyst prepared in Example 1 of the present invention has the lowest charge transfer resistance, which indicates more efficient charge transport and improved OER kinetics at the electrode / electrolyte interface.
[0130] like Figure 9 The cross-flow stability test results are shown in Figure 2. After 24 hours of stability test, the multi-stage self-supporting MOF-based electrolytic water catalyst prepared in Example 1 of the present invention has a stability of 25 mA cm -2The current density only decreased slightly by 7.2%. The attached figure shows the LSV curves before and after 2000 CV cycles. It can be seen that after 2000 CV cycles, the change in the LSV curve of the electrode is negligible. These results demonstrate that the multi-level self-supporting MOF-based water electrolysis catalyst prepared in Example 1 of the present invention has good catalytic stability.
[0131] In summary, the multi-stage self-supporting MOF-based water electrolysis catalyst provided by the present invention features the advantages of no binder, high specific surface area, and efficient mass transfer channels, demonstrating excellent catalytic performance and stability. The method described in the present invention also offers advantages such as controllable product morphology, a simple fabrication process, and the ability to efficiently process large areas, suggesting promising industrial applications.
[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst, characterized in that: The following steps are involved: S1: Using femtosecond laser to vertically irradiate the substrate surface, a substrate with three-dimensional micro / nanostructure is prepared; S2: MOF nanosheets are grown on the surface of the base material with three-dimensional micro / nano structure obtained in S1.
2. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 1, wherein: The S1 is specifically implemented by the following steps: S11: Fix the substrate material to be processed on the translation stage, focus the femtosecond laser beam on the surface of the substrate material to be processed through the objective lens, control the translation stage to move and perform laser scanning, and complete the femtosecond laser processing; S12: The material obtained by femtosecond laser processing in S11 is cleaned with anhydrous ethanol and dried to obtain a base material with a three-dimensional micro / nano structure.
3. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 1 or 2, characterized in that: The substrate material includes a metal substrate or a carbon substrate.
4. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 2, wherein: The objective lens parameters of the laser scanning in S11 are 5 to 20 times, the scanning speed is 200 to 2000 μm / s, the scanning spacing is 5 to 30 μm, the laser repetition frequency is 500 Hz to 20 kHz, and the laser flux is 0.5 to 150 J / cm 2 ; The drying temperature in S12 is 20-40° C. and the drying time is 8-24 hours.
5. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 1, characterized in that: The S2 is specifically implemented by the following steps: S21: mixing a mixed aqueous solution of a cobalt salt and a copper salt with an aqueous solution of 2-methylimidazole to prepare a co-precipitation reaction solution; S22: immersing the substrate material having the three-dimensional micro / nano structure obtained in S1 into the co-deposition reaction solution obtained in S21 to perform a co-deposition reaction; S23: The base material after the co-deposition reaction in S22 is washed with anhydrous ethanol and then dried to prepare a multi-stage self-supporting MOF-based water electrolysis catalyst.
6. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 5, characterized in that: The cobalt salt in S21 is at least one of cobalt chloride hexahydrate, cobalt nitrate hexahydrate and cobalt sulfate heptahydrate; The copper salt is at least one of copper chloride dihydrate, copper nitrate trihydrate and copper sulfate pentahydrate; The concentration of cobalt salt is 1-50 mmol / L, the concentration of copper salt is 1-50 mmol / L, the concentration of 2-methylimidazole is 10-500 mmol / L, and the volume ratio of the mixed aqueous solution composed of cobalt salt and copper salt to the 2-methylimidazole aqueous solution is 1:(0.5-2).
7. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 5 or 6, characterized in that: The molar concentration ratio of the cobalt salt to the copper salt in the mixed aqueous solution composed of the cobalt salt and the copper salt is 1:(0.1-2); the molar concentration ratio of the total metal salt in the mixed aqueous solution composed of the cobalt salt and the copper salt to the 2-methylimidazole in the 2-methylimidazole aqueous solution is 1:(5-20).
8. The method for preparing a multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 5, characterized in that: The co-deposition reaction temperature in S22 is 20 to 50° C. and the time is 2 to 10 hours; The drying temperature in S23 is 20-40° C. and the drying time is 8-24 hours.
9. A multi-stage self-supporting MOF-based water electrolysis catalyst, characterized in that: The preparation method according to any one of claims 1 to 8 is used.
10. Use of the multi-stage self-supporting MOF-based water electrolysis catalyst according to claim 9 in an electrocatalytic oxygen evolution reaction.