Mo modified nanotube self-assembled nanoflower material as well as preparation method and application thereof

Abstract

The invention discloses a Mo modified nanotube self-assembled nanoflower material and a preparation method and application thereof. The method comprises the following steps: (1) cleaning and drying foamed nickel, and placing the foamed nickel at the bottom of a reaction kettle; (2) cobalt nitrate, nickel nitrate, urea, ammonium fluoride, molybdenum salt and polyvinylpyrrolidone are mixed and dissolved, then the mixture is placed in a reaction kettle, heat preservation is carried out for 5-6 h at the temperature of 110-120 DEG C, foamed nickel obtained after reaction in the reaction kettle is taken out after the mixture is cooled to the room temperature, cleaning and drying are carried out, and an intermediate product is obtained; and (3) mixing the intermediate product with a sodium sulfide nonahydrate solution, placing the mixture in a reaction kettle, keeping the temperature at 120-130 DEG C for 4-5 hours, cooling to room temperature, taking out foamed nickel after reaction in the reaction kettle, and cleaning and drying the foamed nickel to obtain the Mo modified nanotube self-assembled nanoflower material. The preparation method can solve the problems that the material form is not uniform, the synthesis process is difficult to accurately control, the conductivity is poor, and the adhesion with a current collector is poor.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen production, and specifically relates to a Mo-modified nanotube self-assembled nanoflower material, a preparation method thereof, and an application thereof. Background Art

[0002] In the context of addressing global energy crises and environmental pollution problems, hydrogen energy, as a clean and renewable energy source, has gradually received wide attention. Hydrogen production by electrolyzing water is an important method for producing hydrogen, and it is regarded as an important future source of hydrogen energy due to its rich raw materials and relatively simple process. However, the choice of catalyst in the electrolysis of water directly affects the hydrogen production efficiency and economy. Currently, platinum and its alloy catalysts are widely used due to their excellent catalytic activity, but their high cost and scarcity limit their large-scale application.

[0003] Among many alternative catalysts, nickel-cobalt sulfide (CoNi2S4) has attracted much attention due to its excellent electrocatalytic performance and good stability. The catalytic activity of CoNi2S4 mainly stems from its unique crystal structure and good electrical conductivity. Research shows that compared with single metal sulfides (such as NiS and CoS), CoNi2S4 has more redox reaction sites, thus promoting the production of hydrogen during the electrolysis of water. In addition, the electrical conductivity of CoNi2S4 has increased by two orders of magnitude compared with the corresponding oxides (such as NiCo2O4), which enables it to conduct current more effectively during the electrolysis process and improves the efficiency of the electrocatalytic reaction.

[0004] Nickel-cobalt sulfide (CoNi2S4) and its heterostructures have shown significant application potential in the field of hydrogen production by electrolyzing water. By optimizing the microstructure of the material, improving the electrical conductivity, and constructing heterostructures, etc., its electrocatalytic performance can be effectively improved, making it an important catalyst for clean hydrogen energy. This not only helps to promote the commercialization process of hydrogen energy but also provides a new direction for achieving a more environmentally friendly energy utilization method.

[0005] The electrocatalytic characteristics of electrode materials are greatly affected by their morphological characteristics. Traditional improvement strategies for nickel-cobalt sulfide mainly involve doping techniques and the construction of heterostructures. In the traditional process of constructing heterostructures, the general steps are as follows: First, prepare a single electrode material substrate; second, use a secondary growth technique to form a heterostructure on it; finally, perform sulfidation to obtain the required sulfide heterostructure. This process includes three main reaction stages, aiming to improve the electrochemical performance by forming a synergy between the constituent materials.

[0006] However, this traditional manufacturing method has defects. The surface of the initial material layer is uneven and rough, resulting in unequal bonding forces and nucleation rates in different regions during the secondary reaction. This will lead to local property differences in the final material and a lack of overall uniformity. Summary of the Invention

[0007] The object of the present invention is to provide a Mo-modified nanotube self-assembled nanoflower material, its preparation method and application, which can solve the problem of uneven material morphology.

[0008] In one aspect of the present invention, a preparation method of a Mo-modified nanotube self-assembled nanoflower material is proposed. According to an embodiment of the present invention, the method includes the following steps:

[0009] (1) Clean and dry the nickel foam, and place it at the bottom of the reaction kettle;

[0010] (2) Mix and dissolve cobalt nitrate, nickel nitrate, urea, ammonium fluoride, molybdenum salt and polyvinylpyrrolidone, then place them in the reaction kettle, keep warm at 110-120 °C for 7-8 h, cool to room temperature, take out the nickel foam after reaction in the reaction kettle, wash and dry it to obtain an intermediate product;

[0011] (3) Mix the intermediate product with a sodium sulfide nonahydrate solution, place it in the reaction kettle, keep warm at 120-130 °C for 3-5 h, cool to room temperature, take out the nickel foam after reaction in the reaction kettle, wash and dry it to obtain the Mo-modified nanotube self-assembled nanoflower material.

[0012] In addition, according to the preparation method of a Mo-modified nanotube self-assembled nanoflower material of the above embodiment of the present invention, it may also have the following additional technical features:

[0013] In some embodiments of the present invention, in step (1), the cleaning is respectively carried out by ultrasonic treatment with deionized water and alcohol, the drying temperature is 50-70 °C, and the drying time is 11-13 h.

[0014] In some embodiments of the present invention, in step (1), the nickel foam has a length of 3-5 cm, a width of 4-6 cm, and a thickness of 10-12 μm, and the nickel foam is perpendicular to the bottom of the reaction kettle.

[0015] In some embodiments of the present invention, in step (2), the molar ratio of cobalt nitrate, nickel nitrate, molybdenum salt, urea, and ammonium fluoride is 1-3:0.5-2:1.5-3:3-5:10-12.

[0016] In some embodiments of the present invention, in step (2), the cleaning is carried out with absolute ethanol and deionized water, the drying temperature is 50-70 °C, and the drying time is 11-13 h.

[0017] In some embodiments of the present invention, in step (3), the molar ratio of the intermediate product to sodium sulfide nonahydrate is 1-2:0.5-1.

[0018] In some embodiments of the present invention, in step (3), the cleaning is carried out with absolute ethanol and deionized water, the drying temperature is 50 - 70 °C, and the drying time is 11 - 13 h.

[0019] In another aspect of the present invention, the present invention provides a Mo-modified nanotube self-assembled nanoflower material prepared by the preparation method of the Mo-modified nanotube self-assembled nanoflower material.

[0020] In another aspect of the present invention, the present invention provides an electrode material. According to the embodiments of the present invention, it is prepared by using the Mo-modified nanotube self-assembled nanoflower material.

[0021] In another aspect of the present invention, the present invention provides a method for hydrogen production by electrolyzing water. According to the embodiments of the present invention, the electrode material is used as the working electrode.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1) The present invention synthesizes a heterostructure with a unique structure through a simple hydrothermal method. The obtained Mo-modified nanotube self-assembled nanoflower material exhibits a nanoflower-like structure formed by self-assembly of nanosheets. This three-dimensional morphology not only provides abundant electrochemically active sites but also significantly increases the specific surface area, thereby endowing it with excellent mass specific capacitance. Since the nanoflower-like structure formed by self-assembly of nanosheets makes the morphology of the material uniform, it effectively optimizes the electrochemical performance of the material, further improving its capacitance performance and cycle stability. In particular, the uniform arrangement of the nanoflowers ensures the internal structural consistency of the material, avoiding fluctuations in electrochemical performance caused by uneven morphology. This uniform morphology facilitates the rapid transmission of charges and better ion diffusion, enabling the current to be more evenly distributed throughout the material, significantly enhancing the overall electrochemical activity of the material. At the same time, this uniformity also improves the stability of the material during long-term charge and discharge processes, reducing performance degradation.

[0024] 2) Due to the presence of conductive agents and binders, the mass of the entire electrode material is relatively large, and the structure of the electrode material is prone to collapse, resulting in poor cycle performance. The electrode material prepared by the integrated method of the present invention can effectively avoid the use of conductive agents and binders.

[0025] 3) The method of the present invention enables the reaction materials to react completely, and then by adding a surfactant (polyvinylpyrrolidone) and the Mo doping concentration, the reaction rate and nucleation rate can be changed to form a nanoflower structure self-assembled from nanosheets. Specifically, polyvinylpyrrolidone, as a surfactant, can adsorb on the material surface during the reaction, reducing the surface energy, thereby effectively controlling the growth of grains and avoiding premature aggregation or caking of the material. It promotes the uniform growth of nanosheets by stabilizing intermediates and regulating the interfacial tension, further controlling the formation of the nanoflower-like structure. In addition, the surfactant can also increase the viscosity of the solution, slow down the diffusion rate of reactants, help the reactants to contact more uniformly, and thus optimize the nucleation and growth processes.

[0026] As for the Mo doping concentration, its influence on the reaction rate and nucleation rate is reflected in its ability to regulate the electronic structure in the reaction system. Mo doping can change the electron distribution and chemical environment of the reaction materials, cause changes in the stability of reaction intermediates, and thus regulate the reaction rate. When the Mo concentration is appropriate, it can accelerate the activation of reactants and promote the efficient nucleation of materials. When the Mo concentration is too high, it may lead to over-activation of the reaction system due to excessive doping elements, resulting in an overly fast reaction rate, thus affecting the formation of the nanoflower structure. Therefore, an appropriate Mo doping concentration helps to control the uniformity of the reaction and the nucleation rate, and finally obtain a nanoflower-like material with a uniform structure and excellent morphology.

[0027] 4) The present invention obtains the corresponding sulfide electrode material by sulfiding the Mo-modified nanotube self-assembled nanoflower material. Based on the high conductivity of the sulfide and the high specific activity of the three-dimensional material NiCo2S4, this structure can release a large number of reactive sites and a high specific surface area.

[0028] 5) The Mo-modified nanotube self-assembled nanoflower material described in the present invention has significant advantages in terms of precise control during the synthesis process, conductivity, and adhesion to the current collector. During the synthesis process, precise control of the reaction temperature, time, and solution composition enables the uniform and stable formation of the material's morphology. Especially in steps (2) and (3), by precisely adjusting the temperature and reaction time, the structures of the intermediate and final products are controllable. Polyvinylpyrrolidone, as a surfactant, effectively regulates the diffusion rate of the reactants and the nucleation process during the reaction, further controlling the growth of the nanosheets and avoiding uneven agglomeration or overgrowth. The finally obtained nanoflower-like structure is uniform in size and morphology, and such a uniform structure can improve the conductivity of the material. In terms of conductivity, Mo plays an important role in the self-assembly process of the nanotubes. The doping of molybdenum can improve the electronic structure of the nanomaterial and enhance its conductivity. Mo doping not only improves the electronic conductivity of the material but also optimizes the charge transport efficiency of the material, enabling charges to flow more efficiently within the material, thereby significantly enhancing the conductive performance of the material. This is particularly important in the applications of energy storage devices (such as supercapacitors, batteries, etc.). In terms of adhesion to the current collector, using nickel foam as the support material can provide a larger surface area and better mechanical support, enhancing the adhesion between the nanoflower material and the current collector. After cleaning and drying treatments, the active sites on the surface of the nickel foam are enhanced, further improving the bonding strength between the material and the current collector, thereby enhancing the stability and durability of the electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 X-ray diffraction pattern of the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1;

[0030] Figure 2 Low-magnification scanning electron microscope image of the Mo-modified nanotube self-assembled nanoflower material prepared in Example 1 of the present invention;

[0031] Figure 3 High-magnification scanning electron microscope image of the Mo-modified nanotube self-assembled nanoflower material prepared in Example 1 of the present invention;

[0032] Figure 4 Low-magnification scanning electron microscope image of the Mo-modified nanotube self-assembled nanoflower material prepared in Comparative Example 1 of the present invention;

[0033] Figure 5 High-magnification scanning electron microscope image of NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1 of the present invention;

[0034] Figure 6 The hydrogen evolution LSV curve test comparison diagram of the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and the NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1;

[0035] Figure 7 The hydrogen evolution environmental Tafel slope comparison diagram of the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and the NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1;

[0036] Figure 8 The oxygen evolution LSV curve test comparison diagram of the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and the NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1;

[0037] Figure 9 The oxygen evolution environmental Tafel slope comparison diagram of the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and the NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1;

[0038] Figure 10 The comparison diagram of the electrochemical activity value related to the oxygen evolution reaction and the double-layer capacitance (C dl ) of the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and the NiCo2S4@PVP without Mo element doping prepared in Comparative Example 1. Detailed implementation manners

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Example 1

[0041] A preparation method of a Mo-modified nanotube self-assembled nanoflower material, comprising the following steps;

[0042] 1) Pretreat the nickel foam (length×width×thickness: 3.8 cm×5 cm×10 μm) by ultrasonicating it in deionized water for half an hour, then ultrasonicating it in alcohol for half an hour, repeating this three times, and finally drying the nickel foam in a vacuum drying oven. The size of the nickel foam (length×width×thickness) is 3.8 cm×5 cm×10 μm. At the same time, ensure that the nickel foam is perpendicular to the bottom of the reaction kettle during the preparation process;

[0043] 2) Dissolve 2 mmol of cobalt nitrate, 1 mmol of nickel nitrate, 6 mmol of urea, 25 mmol of ammonium fluoride, 0.2 mmol of sodium molybdate, and 0.04 g of polyvinylpyrrolidone (PVP) in 60 ml of water and stir for 60 minutes; then transfer the above solution into a reaction kettle and keep it at 120 °C for 6 h; cool it naturally to room temperature, wash it 4 times with absolute ethanol and deionized water, and dry the prepared sample by keeping it at 60 °C for 12 h.

[0044] 3) Dissolve 0.35 g of sodium sulfide nonahydrate in 60 ml of deionized water, stir magnetically for 30 min, then transfer the sample prepared in step 2) into this solution, put it into a reaction kettle, and keep it at 120 °C for 4 h. Cool it naturally to room temperature, wash it 4 times with absolute ethanol and deionized water, and dry the prepared sample by keeping it at 60 °C for 12 h to obtain the finished product, denoted as Mo-CoNi2S4@PVP.

[0045] All the chemicals used in the whole experimental process are of analytical grade with a purity of 99.99%.

[0046] The whole reaction process is as follows:

[0047]

[0048] Among them, reaction formula (1) represents the reaction of cobalt salt (Co2+) with hydroxide ions (OH-) in step (2) to form cobalt sulfide (CoS) and release electrons; reaction formula (2) represents the reaction of the intermediate product (CoSOH) with OH- to be further converted into CoSO and release more electrons; reaction formula (3) represents the reaction of nickel salt (Ni 2 +) with hydroxide ions (OH-) to form nickel sulfide (NiS) and release electrons, which can correspond to reaction formula (3).

[0049] Example 2

[0050] A preparation method of an Mo-modified nanotube self-assembled nanoflower material, the difference from Example 1 is only that: in step 2), the amount of sodium molybdate is 0.4 mmol, the amount of polyvinylpyrrolidone is 0.06 g, and the volume of water dissolved is 60 ml, and other parameters and steps are the same.

[0051] The finished products obtained in Example 1 were subjected to X-ray detection, and the results are shown in Figure 1 , and it can be found that the diffraction peaks include the diffraction peaks of both CoNi2S4 and MoS2, indicating that the Mo-CoNi2S4@PVP nanoflower heterostructure formed by Mo doping was successfully prepared.

[0052] Shown in Figure 2 is the low-magnification scanning electron microscopy image of the nanoflower-like heterostructure electrode material, presenting a nanoflower structure self-assembled by nanosheets. The prepared material shows a large number of nanowires, and each nanowire grows uniformly.

[0053] Although in the low-magnification scanning electron microscopy image, the Mo-modified nanotube self-assembled nanoflower material shows a large number of uniformly growing nanowires, however, the overall structure of the Mo-modified nanotube self-assembled nanoflower material is actually composed of nanotubes with a hollow structure, as shown in Figure 3 . Each nanotube is hollow inside, and the outer wall is composed of stacked nanosheets. This hollow property of the nanotube further enhances the conductivity and electrochemical performance of the material, making the material exhibit lower internal resistance and higher capacitance during charge and discharge, thereby improving its overall performance in electrochemical applications. This structure endows it with rich electrochemical active sites and significantly increases the specific surface area, thus conferring excellent mass specific capacitance and effectively improving the electrochemical performance of the material.

[0054] Shown in Figure 4 is the low-magnification scanning electron microscopy image of the electrode material of the comparative example without Mo doping. It can be seen that the morphology of this material is non-uniform everywhere, resulting in no rich electrochemical active sites, low charge transfer efficiency, and weak electrocatalytic performance.

[0055] Comparative Example 1

[0056] A preparation method of NiCo2S4@PVP without Mo element doping includes the following steps:

[0057] 1) First, pretreat the nickel foam. Put a clean nickel foam into deionized water, ultrasonicate for half an hour, then ultrasonicate with alcohol for half an hour, repeat three times, and finally put the nickel foam into a vacuum drying oven for drying. In this way, the organic impurities on the foam surface can be removed.

[0058] 2) Dissolve 2 mmol of cobalt nitrate, 1 mmol of nickel nitrate, 6 mmol of urea, 25 mmol of ammonium fluoride, and 0.04 g of polyvinylpyrrolidone (PVP) in 60 ml of water and stir for 60 minutes; then transfer the above solution into a reaction kettle and keep it at 120 °C for 6 h; naturally cool to room temperature, wash it 3 times with absolute ethanol and deionized water, and dry the prepared sample at 60 °C for 12 h;

[0059] 3) Dissolve 0.35 g of sodium sulfide nonahydrate in 60 mL of deionized water, stir magnetically for 30 min, then transfer the sample prepared in step 2) into this solution, transfer it into a reaction kettle, and keep it at 120 °C for 4 h. Naturally cool it to room temperature, wash it 3 times with absolute ethanol and deionized water, and dry the prepared sample at 60 °C for 12 h to obtain the finished product NiCo2S4@PVP.

[0060] The morphology of the NiCo2S4@PVP material without Mo element doping is uniform, lacking the nanoflower structure, presenting a disordered agglomerate structure, resulting in fewer reaction active sites and weak catalytic effect. The structural differences between the comparative example and the examples are attributed to the ionic synergistic effect between metal Mo and Ni, Co metal elements. During the reaction process, the incorporation of Mo effectively changes the original structural characteristics, enabling the formation of a unique nanoflower heterostructure in the electrode material during the one-step synthesis process. This synergistic effect promotes the acceleration of the charge transfer rate. At the same time, the presence of three-dimensional nanosheets significantly increases the number of reaction active sites. Therefore, the nanoflower-like heterostructure based on the assembly of nanosheets significantly improves the specific capacity and reaction activity of the material.

[0061] Application Example

[0062] A method for hydrogen production by electrolyzing water, comprising the following steps:

[0063] 1) Prepare the electrode material: Prepare the electrode material according to the method described in Example 1.

[0064] 2) Assemble the electrode device: Use the electrode material prepared in step 1) as the working electrode, and assemble it with a reference electrode (AgCl) and a platinum plate electrode into an electrolytic water device. Ensure that the surface of the electrode material is evenly distributed and effectively contacts the electrolyte.

[0065] 3) Electrolyze water reaction: Add 1 M KOH electrolyte into the electrolytic water device prepared in step 2), and carry out the electrolyze water reaction under a constant current or voltage. Apply an appropriate voltage or current. Through the electrolysis process, water molecules decompose on the electrode surface to generate hydrogen and oxygen.

[0066] 3) Gas collection: Separate and collect the hydrogen and oxygen generated during the electrolysis process. Hydrogen is introduced into the storage device as the product, while oxygen is discharged.

[0067] 4) Hydrogen purification and storage: The obtained hydrogen can be further purified and stored as clean energy. The hydrogen produced by this method can be widely used in fields such as fuel cells and industrial hydrogen production.

[0068] Electrochemical tests and SEM, XRD show (see the attached drawings) that the prepared sample has low electrocatalytic performance.

[0069] The comparative diagram of various electrocatalytic performance tests between the Mo-modified nanotube self-assembled nanoflower material (Mo-CoNi2S4@PVP) prepared in Example 1 of the present invention and the NiCo2S4@PVP electrode material without Mo element doping prepared in Comparative Example 1 is as Figures 6 - 10 shown. In terms of electrocatalysis, the electrode material prepared in Example 1 of the invention shows an overpotential of -92.4 mV and a Tafel slope of 106.37 mV·dec -2 at a current density of -10 mA·cm -1 in an electrolyte of 1 M KOH (hydrogen evolution reaction). For an electrocatalyst, the smaller the overpotential, the better. At a current density of 10 mA·cm -2 , it shows an overpotential of 354.6 mV and a Tafel slope of 100.35 mV·dec -1 . And the electrochemically active value related to the oxygen evolution reaction and the double-layer capacitance (C dl ) of this material is 0.04402 mF·cm -2 . The larger the electrochemically active value, the more active sites the electrode material has, the more reaction catalytic positions it provides for substances, and the faster the catalytic reaction rate. It shows excellent electrochemically active surface area and outstanding reaction rate kinetics. For the electrode material of Comparative Example 1 (NiCo2S4@PVP) without Mo doping, it shows a disordered agglomerate structure, resulting in fewer reactive sites and weak catalytic effect. And at a current density of -10 mA·cm -2 , it shows an overpotential of -162.4 mV and a Tafel slope of 90.98 mV·dec -1 . At a current density of 10 mA·cm -2 , it shows an overpotential of 395.6 mV and a Tafel slope of 74.18 mV·dec -1 . And the electrochemically active value related to the oxygen evolution reaction and the double-layer capacitance (C dl ) of this material is 0.00965 F·cm -2 . Compared with the electrode material of Comparative Example 1 without Mo doping, the nanoflower-like heterostructure and excellent electrocatalytic performance of Example 1 of the invention (Mo-NiCo2S4@PVP) are superior to those of Comparative Example 1.

[0070] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the structure of the present invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A preparation method of a Mo-modified nanotube self-assembled nanoflower material, characterized in that It includes the following steps: (1) Clean and dry the nickel foam, and place it at the bottom of the reaction kettle; (2) Mix and dissolve cobalt nitrate, nickel nitrate, urea, ammonium fluoride, molybdenum salt and polyvinylpyrrolidone, then place it in the reaction kettle, keep it warm at 110 - 120 °C for 7 - 8 h, after cooling to room temperature, take out the foam in the reaction kettle, wash and dry it to obtain an intermediate product; (3) Mix the intermediate product with a sodium sulfide nonahydrate solution, place it in the reaction kettle, keep it warm at 120 - 130 °C for 3 - 5 h, after cooling to room temperature, take out the nickel foam after reaction in the reaction kettle, wash and dry it, and the Mo-modified nanotube self-assembled nanoflower material is obtained.

2. The preparation method of a Mo-modified nanotube self-assembled nanoflower material according to claim 1, wherein: In step (1), the cleaning is carried out by ultrasonic treatment with deionized water and alcohol respectively, the drying temperature is 50 - 70 °C, and the drying time is 11 - 13 h.

3. The preparation method of a Mo-modified nanotube self-assembled nanoflower material according to claim 1, wherein: In step (1), the length of the nickel foam is 3 - 5 cm, the width is 4 - 6 cm, the thickness is 10 - 12 μm, and the nickel foam is perpendicular to the bottom of the reaction kettle.

4. The preparation method of a Mo-modified nanotube self-assembled nanoflower material according to claim 1, wherein: In step (2), the molar ratio of cobalt nitrate, nickel nitrate, molybdenum salt, urea, and ammonium fluoride is 1 - 3:0.5 - 2:1.5 - 3:3 - 5:10 - 12.

5. The preparation method of a Mo-modified nanotube self-assembled nanoflower material according to claim 1, wherein: In step (2), the cleaning is carried out with absolute ethanol and deionized water, the drying temperature is 50 - 70 °C, and the drying time is 11 - 13 h.

6. The preparation method of a Mo-modified nanotube self-assembled nanoflower material according to claim 1, characterized in that: In step (3), the molar ratio of the intermediate product to sodium sulfide nonahydrate is 1 - 2:0.5 - 1.

5.

7. The preparation method of a Mo-modified nanotube self-assembled nanoflower material according to claim 1, characterized in that: In step (3), the cleaning is carried out with absolute ethanol and deionized water, the drying temperature is 50 - 70 °C, and the drying time is 11 - 13 h.

8. The Mo-modified nanotube self-assembled nanoflower material prepared by the preparation method of the Mo-modified nanotube self-assembled nanoflower material according to any one of claims 1 - 7.

9. An electrode material, characterized in that: Prepare by using the Mo-modified nanotube self-assembled nanoflower material described in claim 8.

10. A method for producing hydrogen by electrolyzing water, characterized in that: Use the electrode material described in claim 9 as the working electrode.

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