Molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material and its preparation method and application

Abstract

The present invention relates to the technical field of electrochemical energy materials, and specifically discloses a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material, its preparation method and application. The method comprises S1, preparing copper hydroxide nanowires loaded on copper foam; S2, preparing copper nanowires loaded on copper foam; S3, preparing copper nanowire-loaded molybdenum-doped nickel cobalt nanosheets; S4, placing the copper nanowire-loaded molybdenum-doped nickel cobalt nanosheets in a tube furnace, and nitriding them in an ammonia nitrogen atmosphere to obtain a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material. The internal resistance of the material is reduced by electron transfer and heterostructure between molybdenum nitride and nickel cobalt nitride, and compared with precious metal platinum wire, the material has excellent high current density hydrogen evolution performance. The preparation method provided by the present invention has the advantages of simple synthesis process, short synthesis cycle and low production cost. In addition, no hydrothermal reaction is required during preparation, the material has high safety and reliable repeatability, and is very suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy materials, and specifically relates to a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material and a preparation method and application thereof. Background Art

[0002] Currently, the electrocatalytic hydrogen evolution reaction (HER) using clean electricity is considered the most promising technology for sustainable production. Alkaline water electrolysis is currently more attractive because it requires low-cost equipment and effectively avoids acid corrosion. To accelerate the sluggish kinetics caused by the additional water splitting step in alkaline electrolytes, efficient and highly stable catalysts are required, especially electrocatalytic materials that can withstand high current densities.

[0003] In the existing technology, platinum-based catalysts are still the benchmark catalysts for hydrogen evolution reactions in acidic and alkaline electrolytes. However, platinum catalysts have the following technical problems: (1) High production cost: Platinum is a scarce and expensive metal, and its price fluctuations directly affect the manufacturing cost of fuel cells. As the demand for hydrogen fuel cells increases, the market demand for platinum continues to rise, and the supply may not be able to meet the demand, resulting in rising costs; (2) Catalyst stability: In fuel cells, platinum-based catalysts are prone to degradation of cell performance due to aggregation and dissolution of catalyst particles. Especially during long-term operation, these problems may lead to degradation of cell performance; (3) Limited catalyst activity: Although platinum is an efficient catalyst, its activity may be affected by the carbon support and other alloying elements in actual applications, which limits its further performance improvement.

[0004] A wide variety of transition metals are used in hydrogen evolution catalysts, and transition metal nitrides generally exhibit high catalytic activity. However, the challenge remains to design and develop HER catalysts that maintain high stability at high current densities, using an abundant element to replace precious platinum-based catalysts. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies in the existing technology and provide a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material and its preparation method and application. Through the electron transfer and heterostructure of molybdenum nitride and nickel cobalt nitride nanosheets, the internal resistance of the material is greatly reduced while maintaining the chemical composition and structural stability. At the same time, compared with precious metal platinum wire, this composite electrocatalytic material not only greatly reduces the material cost, but also has better high current density hydrogen evolution performance.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention is to provide a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material, comprising the following steps:

[0008] S1. Immersing the cut copper foam in dilute hydrochloric acid for pretreatment, then washing and drying it, and then immersing the treated copper foam in a mixed solution of ammonium persulfate and sodium hydroxide to obtain copper hydroxide nanowires supported on the copper foam;

[0009] S2. placing the copper hydroxide nanowire sample loaded on copper foam obtained in step S1 in a muffle furnace for air calcination, and electrochemically reducing the calcined sample in a potassium bicarbonate electrolyte to obtain copper nanowires loaded on copper foam;

[0010] S3, placing the copper nanowires loaded on the copper foam obtained in step S2 in an electrolyte of nickel nitrate, cobalt nitrate and sodium molybdate, and loading the copper nanowires with molybdenum-doped nickel-cobalt nanosheets by electrochemical deposition;

[0011] S4. Placing the copper nanowire-loaded molybdenum-doped nickel-cobalt nanosheets obtained in step S3 in a tube furnace, and nitriding them in an ammonia-nitrogen atmosphere to obtain a molybdenum nitride / nickel-cobalt nitride nanosheet heterostructure electrocatalytic material.

[0012] Furthermore, in step S1, the mass fraction of the dilute hydrochloric acid is 5wt% to 15wt%, and the molar ratio of the ammonium persulfate to the sodium hydroxide is (1 to 5): (10 to 20).

[0013] Furthermore, in step S2, the temperature of the muffle furnace is set to 100° C. to 200° C., and the air calcination time is 0.5 h to 2 h.

[0014] Furthermore, in step S2, the concentration of potassium bicarbonate is 0.1 mol / L to 1.5 mol / L, and the time of electrochemical reduction is 3000 to 6000 s.

[0015] Furthermore, in step S3, the molar ratio of nickel nitrate, cobalt nitrate and sodium molybdate is (10-15):(10-15):(1-5).

[0016] Furthermore, in step S3, the electrochemical deposition time is 30 to 90 seconds.

[0017] Furthermore, in step S4, the temperature of the tube furnace is set to 100° C. to 500° C., and the calcination time is 1 h to 3 h.

[0018] The second aspect of the present invention is to provide a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material prepared by the above-mentioned preparation method.

[0019] The third aspect of the present invention is to provide the use of the above-mentioned molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material in electrolytic hydrogen production.

[0020] Furthermore, in a three-electrode system, potassium hydroxide solution and sodium chloride solution were used as electrolytes to carry out high current density electrocatalytic hydrogen evolution reaction.

[0021] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0022] (1) By growing copper nanowires on copper foam and synthesizing molybdenum nitride and nickel-cobalt nitride nanosheets on them, molybdenum-doped nickel-cobalt nanosheets are covered on the nanowires, effectively increasing the mass transfer and reaction area.

[0023] (2) Nitriding the molybdenum-doped nickel-cobalt nanosheets significantly improves their electrical conductivity. Nitrogen incorporation alters the electronic structure and energy band structure, facilitating rapid electron transport within the material while maintaining chemical composition and structural stability. Furthermore, compared to precious metal platinum wire, the composite electrocatalytic material exhibits superior high-current-density hydrogen evolution performance.

[0024] (3) The preparation method provided by the present invention has the advantages of simple synthesis process, short synthesis cycle and low production cost. In addition, no hydrothermal reaction is required during preparation, and the preparation method has high safety and reliable repeatability, making it very suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of copper nanowires grown on the copper foam prepared in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron microscope photograph of molybdenum-doped nickel-cobalt nanosheets grown on copper nanowires prepared in Example 1 of the present invention;

[0027] Figure 3 The scanning electron microscope image and transmission electron microscope image of the composite electrocatalytic material prepared in Example 1 of the present invention are shown in FIG. (a) is a scanning electron microscope image, and (b) is a transmission electron microscope image;

[0028] Figure 4 This is an X-ray diffraction pattern of the composite electrocatalytic material prepared in Example 1 of the present invention;

[0029] Figure 5 This is a hydrogen evolution stability test curve diagram of this embodiment 1;

[0030] Figure 6a This is the X-ray photoelectron spectrum of molybdenum element before and after the hydrogen evolution stability test of Example 1;

[0031] Figure 6bThis is the X-ray photoelectron spectrum of nickel element before and after the hydrogen evolution stability test of this Example 1;

[0032] Figure 6c This is the X-ray photoelectron spectrum of cobalt element before and after the hydrogen evolution stability test of Example 1;

[0033] Figure 7 This is a comparison chart of hydrogen evolution reaction activities of the composite electrocatalytic materials prepared by Comparative Example 1, Comparative Example 2, and the precious metal platinum wire and Example 1 of the present invention;

[0034] Figure 8 This is a comparison chart of the hydrogen evolution reaction activity of the composite electrocatalytic materials prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0035] To make the objects, technical solutions, and advantages of the present invention more apparent, the following describes the specific embodiments of the present invention in further detail with reference to the specific examples and accompanying drawings. Where specific test methods, instruments, or conditions are not specified in the examples, the methods or conditions described in the literature in the art or the product specifications were used. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0036] Example 1

[0037] This embodiment provides a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0038] The specific steps are as follows:

[0039] (1) Preparation of copper hydroxide nanowires loaded on copper foam: The cut copper foam was pre-treated by immersing it in 15 wt% dilute hydrochloric acid, followed by washing and drying. The treated copper foam was then immersed in a mixed solution of 0.1 mol / L ammonium persulfate and 2 mol / L sodium hydroxide to obtain copper hydroxide nanowires loaded on the copper foam;

[0040] (2) Preparation of copper nanowires loaded on copper foam: The copper hydroxide nanowire sample loaded on copper foam obtained in step (1) was placed in a muffle furnace and heated to 180° C. at a rate of 4° C. / min, and kept warm for 2 hours. The calcined sample was electrochemically reduced in a 0.5 mol / L potassium bicarbonate electrolyte for 5000 s to obtain copper nanowires loaded on copper foam;

[0041] (3) Preparation of copper nanowires loaded with molybdenum-doped nickel-cobalt nanosheets: The copper nanowires loaded on the copper foam obtained in step (2) were immersed in an electrolyte of 0.3 mol / L nickel nitrate, 0.3 mol / L cobalt nitrate and 0.05 mol / L sodium molybdate, and the copper nanowires were loaded with molybdenum-doped nickel-cobalt nanosheets by electrochemical deposition for 50 s. After washing and drying, the prepared catalyst was obtained.

[0042] (4) Preparation of molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material: The copper nanowires loaded with molybdenum-doped nickel cobalt nanosheets obtained in step (3) were placed in a tubular furnace and heated to 400°C at a rate of 5°C / min, kept warm for 2 hours, and nitrided in an ammonia nitrogen atmosphere to obtain a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0043] Example 2

[0044] This embodiment provides a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0045] The specific steps are basically the same as those in Example 1, except that the copper nanowire-loaded molybdenum-doped nickel-cobalt nanosheets obtained in step (3) are placed in a tube furnace and heated to 300°C at a rate of 5°C / min, kept warm for 2 hours, and nitrided in an ammonia nitrogen atmosphere to obtain a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0046] Example 3

[0047] This embodiment provides a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0048] The specific steps are basically the same as those in Example 1, except that the copper nanowire-loaded molybdenum-doped nickel-cobalt nanosheets obtained in step (3) are placed in a tube furnace and heated to 500°C at a rate of 5°C / min, kept warm for 2 hours, and nitrided in an ammonia nitrogen atmosphere to obtain a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0049] Example 4

[0050] This embodiment provides a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0051] The specific steps are basically the same as those in Example 1, except that the copper nanowire-loaded molybdenum-doped nickel-cobalt nanosheets obtained in step (3) are placed in a tube furnace and heated to 600°C at a rate of 5°C / min, kept warm for 2 hours, and nitrided in an ammonia nitrogen atmosphere to obtain a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0052] Example 5

[0053] This embodiment provides a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0054] The specific steps are basically the same as those in Example 1, except that the copper nanowires loaded on the copper foam obtained in step (2) are immersed in an electrolyte of 0.3 mol / L nickel nitrate, 0.3 mol / L cobalt nitrate and 0.05 mol / L sodium molybdate, and the copper nanowires are loaded with molybdenum-doped nickel-cobalt nanosheets by electrochemical deposition for 100 s. After washing and drying, the prepared catalyst is obtained.

[0055] Example 6

[0056] This embodiment provides a method for preparing a molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material.

[0057] The specific steps are basically the same as those in Example 4, except that the copper nanowires loaded on the copper foam obtained in step (2) are immersed in an electrolyte of 0.3 mol / L nickel nitrate, 0.3 mol / L cobalt nitrate and 0.05 mol / L sodium molybdate, and the copper nanowires are loaded with molybdenum-doped nickel-cobalt nanosheets by electrochemical deposition for 30 s. After washing and drying, the prepared catalyst is obtained.

[0058] Comparative Example 1

[0059] (1) Preparation of copper hydroxide nanowires loaded on copper foam: The cut copper foam was pre-treated by immersing it in 15 wt% dilute hydrochloric acid, followed by washing and drying. The treated copper foam was then immersed in a mixed solution of 0.1 mol / L ammonium persulfate and 2 mol / L sodium hydroxide to obtain copper hydroxide nanowires loaded on the copper foam;

[0060] (2) Preparation of copper nanowires loaded on copper foam: The copper hydroxide nanowire sample loaded on copper foam obtained in step (1) was placed in a muffle furnace and heated to 180° C. at a rate of 4° C. / min, and kept warm for 2 hours. The calcined sample was electrochemically reduced in a 0.5 mol / L potassium bicarbonate electrolyte for 5000 s to obtain copper nanowires loaded on copper foam;

[0061] (3) Preparation of copper nanowire-loaded molybdenum hydroxide nanosheets: The copper nanowires loaded on the copper foam obtained in step (2) were immersed in an electrolyte of 0.6 mol / L sodium molybdate, and the copper nanowires were loaded with molybdenum hydroxide nanosheets by electrochemical deposition for 50 s. After washing and drying, the prepared catalyst was obtained.

[0062] (4) Preparation of molybdenum nitride nanosheet structure electrocatalytic material: The copper nanowire-loaded molybdenum hydroxide nanosheet obtained in step (3) is placed in a tubular furnace and heated to 400°C at a rate of 5°C / min, kept warm for 2 hours, and nitrided in an ammonia nitrogen atmosphere to obtain a molybdenum nitride nanosheet structure electrocatalytic material.

[0063] Comparative Example 2

[0064] (1) Preparation of copper hydroxide nanowires loaded on copper foam: The cut copper foam was pre-treated by immersing it in 15 wt% dilute hydrochloric acid, followed by washing and drying. The treated copper foam was then immersed in a mixed solution of 0.1 mol / L ammonium persulfate and 2 mol / L sodium hydroxide to obtain copper hydroxide nanowires loaded on the copper foam;

[0065] (2) Preparation of copper nanowires loaded on copper foam: The copper hydroxide nanowire sample loaded on copper foam obtained in step (1) was placed in a muffle furnace and heated to 180° C. at a rate of 4° C. / min, and kept warm for 2 hours. The calcined sample was electrochemically reduced in a 0.5 mol / L potassium bicarbonate electrolyte for 5000 s to obtain copper nanowires loaded on copper foam;

[0066] (3) Preparation of copper nanowires loaded with nickel-cobalt nanosheets: The copper nanowires loaded on the copper foam obtained in step (2) were immersed in an electrolyte of 0.3 mol / L nickel nitrate and 0.3 mol / L cobalt nitrate, and the copper nanowires were loaded with nickel-cobalt nanosheets by electrochemical deposition for 50 s. After washing and drying, the prepared catalyst was obtained.

[0067] (4) Preparation of nickel cobalt nitride nanosheet structure electrocatalytic material: The copper nanowire-loaded molybdenum-doped nickel cobalt nanosheet obtained in step (3) is placed in a tubular furnace and heated to 400°C at a rate of 5°C / min, kept warm for 2 hours, and nitrided in an ammonia nitrogen atmosphere to obtain a nickel cobalt nitride nanosheet structure electrocatalytic material.

[0068] The molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic materials prepared in Examples 1 to 6 all have similar micromorphology, structure, and catalytic performance, and Example 1 is used as an example for illustration:

[0069] refer to Figure 1 , is a scanning electron microscope image of copper nanowires grown on the copper foam prepared in Example 1. It can be seen from the image that the copper nanowires are arranged one by one.

[0070] refer to Figure 2 , which is a scanning electron microscope photograph of molybdenum-doped nickel-cobalt nanosheets grown on the copper nanowires prepared in Example 1. It can be seen from the figure that the nanowires are covered by nanosheets, which provides a larger active area and mass transfer.

[0071] refer to Figure 3 , which are scanning electron microscope images and transmission electron microscope images of the composite electrocatalytic material prepared in Example 1, the molybdenum nitride and nickel cobalt nitride nanosheets are evenly distributed, and the surface of the nitrided nanosheets has a granular feel, further increasing the catalytic active area.

[0072] refer to Figure 4, is the X-ray diffraction pattern of Example 1. It can be seen from the figure that the composite material contains copper (111), (200), and (220) crystal planes. Due to the use of foam copper as the substrate, the loading of molybdenum nitride and nickel cobalt nitride is low, and no diffraction peaks are formed. In this catalyst, the improvement in hydrogen evolution performance is mainly due to electron transfer between molybdenum nitride and nickel cobalt nitride and mass transfer in the heterogeneous structure.

[0073] refer to Figure 5 , is a graph showing the hydrogen evolution stability test of Example 1. It can be seen from the graph that the composite electrocatalytic material is -2 The catalyst's hydrogen evolution performance remained stable for 100 hours at high current density, with no significant change in the polarization curves before and after the stability test. The catalyst's stable hydrogen evolution performance is primarily due to the fact that the introduction of nitrogen atoms strengthens the binding force between molybdenum, nickel, and cobalt atoms, making the electrode material less susceptible to atomic detachment, dissolution, or migration, maintaining a stable chemical composition and structure on the electrode surface and, consequently, maintaining stable hydrogen evolution performance.

[0074] refer to Figures 6a-6c Figure 2 shows the X-ray photoelectron spectra of Example 1 before and after the hydrogen evolution stability test. The figures show no significant changes in the X-ray photoelectron spectra of molybdenum, nickel, and cobalt before and after the stability test. The valence states of the elements in this composite electrocatalytic material remained unchanged during the stability test, primarily due to the more stable nitride structure formed by the combination of molybdenum, nickel, and cobalt with nitrogen atoms.

[0075] refer to Figure 7 , which is a comparison chart of the hydrogen evolution reaction activity of the composite electrocatalyst measured in a standard three-electrode system for Example 1, Comparative Example 1, Comparative Example 2, and precious metal platinum wire. It can be found that the molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material prepared in Example 1 is significantly superior to the single-component nitride electrocatalytic material in the high current density hydrogen evolution reaction, and shows better high current density hydrogen evolution performance than the precious metal platinum wire.

[0076] The molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic materials prepared in Examples 1-4 were tested for hydrogen evolution reaction activity. The results are as follows: Figure 8 As shown in the figure, a comparison of the hydrogen evolution reaction activity of the composite electrocatalyst measured under a standard three-electrode system is shown. It can be seen from the figure that the molybdenum nitride and nickel cobalt nitride nanosheets nitrided at different temperatures using this method can achieve relatively excellent performance. The molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material prepared in Example 1 has the best high current density hydrogen evolution catalytic performance.

[0077] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0078] 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 molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material, characterized in that: The following steps are involved: S1. Immersing the cut copper foam in dilute hydrochloric acid for pretreatment, then washing and drying it, and then immersing the treated copper foam in a mixed solution of ammonium persulfate and sodium hydroxide to obtain copper hydroxide nanowires supported on the copper foam; S2. placing the copper hydroxide nanowire sample loaded on copper foam obtained in step S1 in a muffle furnace for air calcination, and electrochemically reducing the calcined sample in a potassium bicarbonate electrolyte to obtain copper nanowires loaded on copper foam; S3, placing the copper nanowires loaded on the copper foam obtained in step S2 in an electrolyte of nickel nitrate, cobalt nitrate and sodium molybdate, and loading the copper nanowires with molybdenum-doped nickel-cobalt nanosheets by electrochemical deposition; S4. Placing the copper nanowire-loaded molybdenum-doped nickel-cobalt nanosheets obtained in step S3 in a tubular furnace and nitriding them in an ammonia-nitrogen atmosphere to obtain a molybdenum nitride / nickel-cobalt nitride nanosheet heterostructure electrocatalytic material; the temperature of the tubular furnace is set to 100° C. to 500° C., and the calcination time is 1 h to 3 h.

2. The preparation method according to claim 1, wherein In step S1, the mass fraction of the dilute hydrochloric acid is 5wt%~15wt%, and the molar ratio of the ammonium persulfate to the sodium hydroxide is (1~5):(10~20).

3. The preparation method according to claim 1, wherein In step S2, the temperature of the muffle furnace is set to 100° C. to 200° C., and the air calcination time is 0.5 h to 2 h.

4. The preparation method according to claim 1, wherein In step S2, the concentration of potassium bicarbonate is 0.1 mol / L to 1.5 mol / L, and the time of electrochemical reduction is 3000 to 6000 s.

5. The preparation method according to claim 2, wherein In step S3, the molar ratio of nickel nitrate, cobalt nitrate and sodium molybdate is (10-15):(10-15):(1-5).

6. The preparation method according to claim 2, wherein In step S3, the electrochemical deposition time is 30 to 90 seconds.

7. A molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the molybdenum nitride / nickel cobalt nitride nanosheet heterostructure electrocatalytic material according to claim 7 in hydrogen production by electrolysis of water.

9. The use according to claim 8, characterized in that In a three-electrode system, potassium hydroxide solution and sodium chloride solution are used as electrolytes to carry out high current density electrocatalytic hydrogen evolution reaction.

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