Preparation method and application of folded nano reticular iron-molybdenum nitride hydrogen evolution catalyst

Abstract

The invention discloses a preparation method and application of a wrinkled nano reticular iron-molybdenum nitride hydrogen evolution catalyst, and relates to the technical field of electrocatalysts. The preparation method comprises the following steps: firstly, performing in-situ growth of iron and molybdenum on a foamed nickel material through hydrothermal synthesis to obtain a precursor material, then mixing the precursor material with melamine, and calcining in a nitrogen atmosphere to obtain the iron-molybdenum nitride hydrogen evolution catalyst which is of a wrinkled nano reticular microstructure, and the composite material has the characteristics of low overpotential, excellent stability and low cost, and shows excellent performance and wide application prospects in the application of hydrogen production by water electrolysis and the like.

Description

Technical Field

[0001] The invention relates to the technical field of electrocatalysts, and in particular to a preparation method and application of a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst. Background Art

[0002] As a clean energy source, hydrogen has the significant advantages of zero emissions and high energy density, which can effectively reduce environmental pollution and greatly improve energy efficiency. Among the many hydrogen production methods, water electrolysis stands out for its clean and efficient characteristics and has become a popular choice. However, the slow kinetics in the hydrogen evolution reaction (HER) leads to a high overpotential, which has always been the main challenge facing this technology. Therefore, it is particularly important to develop high-performance electrocatalysts to improve the energy conversion efficiency of HER.

[0003] Although platinum group noble metals are considered to be the most advanced HER electrocatalytic materials, their high cost, scarcity and poor durability limit their large-scale application. In contrast, transition metals such as Ni, Co, Mo, and Fe have attracted widespread attention due to their low cost, wide sources and excellent catalytic activity. In particular, by making alloys of these metals, the hydrogen evolution performance of the catalyst can be significantly improved. However, the disadvantage is that the preparation process is complicated. Usually, the manufacture of high-performance transition metal alloys usually requires precise control of composition, structure and morphology, which increases the complexity and cost of the process. For example, in order to achieve the best catalytic effect, the proportion and distribution of each element in the alloy must be strictly regulated. In addition, heteroatom doping can optimize the electronic structure of the catalyst and increase the number of active sites. Among them, nitrogen doping can optimize the adsorption and dissociation process of reaction intermediates such as hydrogen ions. The high electronegativity of nitrogen atoms enables it to increase the local electron density, thereby improving the overall conductivity of the material. However, achieving uniform dispersion of nitrogen in the matrix material is a major challenge. Uneven doping will lead to reduced catalytic activity in local areas, thereby affecting the performance of the entire catalyst.

[0004] In view of this, this application is filed. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst to solve the problems existing in the above-mentioned prior art, so that the hydrogen evolution catalyst has the advantages of low overpotential, good stability, low cost, etc.

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

[0007] One of the technical solutions of the present invention is to provide a method for preparing an iron-molybdenum nitride hydrogen evolution catalyst, comprising the following steps:

[0008] (1) Using hydrothermal synthesis to in-situ grow iron and molybdenum on nickel foam material to obtain a precursor material;

[0009] (2) Mixing the precursor material with melamine and calcining the mixture under a nitrogen atmosphere to obtain the iron-molybdenum nitride hydrogen evolution catalyst.

[0010] Heteroatom doping technology is a means to improve the hydrogen evolution activity of catalysts. Nitrogen doping can increase the electronegativity of the catalyst surface, thereby optimizing the adsorption / desorption process of hydrogen atoms and improving catalytic activity. Nitrogen doping can increase the number of active sites and improve the electronic structure of metal elements inside the catalyst, thereby affecting the hydrogen evolution performance.

[0011] Furthermore, the temperature of the hydrothermal synthesis is 150-300°C, and the time is 4-12 h; more preferably, the temperature is 200°C, and the reaction time is 6 h.

[0012] Furthermore, the molar ratio of iron to molybdenum in the hydrothermal synthesis is 1:0.5-10; the more preferred molar ratio is 1:2.5.

[0013] Furthermore, the amount of melamine used per unit area of ​​the precursor is 20-200 mg·cm -2 .

[0014] Furthermore, the calcination temperature is 450-650°C, and the calcination time is 1-4 h; more preferably, the temperature is 550°C, and the reaction time is 2 h.

[0015] Furthermore, the molybdenum source used in the hydrothermal synthesis of the present invention can be selected from MoO3 or (NH4)6Mo7O 24 ·4H2O; the iron source used in the hydrothermal synthesis can be FeCl3·6H2O or Fe(NO3)3·9H2O.

[0016] More preferably, in the calcination stage, melamine and the precursor are placed upstream and downstream of the porcelain boat respectively for calcination under a nitrogen atmosphere.

[0017] In the above preferred scheme, the melamine powder in the upstream of the porcelain boat is decomposed by high temperature to generate NH3 and nitrogen-containing substances. In the relatively closed space of the porcelain boat, the generation of NH3 will bring some nitrogen-containing substances to be evenly distributed on the catalyst surface. The iron and molybdenum on the catalyst surface react with these nitrogen-containing substances to generate iron and molybdenum nitrides, and generate a special morphology, i.e., a wrinkled nano-mesh structure. The special wrinkled nano-mesh structure of the present invention has abundant active sites and ensures good conductivity of the catalyst, which can promote the rapid transfer of electrons on the catalyst surface and expose more defects to optimize the adsorption and dissociation of substances.

[0018] In the present invention, urea and ammonium fluoride components can also be added during the hydrothermal synthesis process. The ammonia generated by the decomposition of urea can gradually increase the pH value of the solution, so that the metal ions can be evenly precipitated on the nickel foam; ammonium fluoride prevents the agglomeration of nanoparticles to a certain extent, and promotes the formation of the nano-network structure of the catalyst.

[0019] Furthermore, during the hydrothermal synthesis, the molar ratio of the total amount of metal ions to urea is preferably 1:1-1:3. Excessive urea may cause the pH to rise too quickly, forming amorphous precipitates or metal hydroxide impurities. - Coordination with metal ions slows down the crystallization rate and inhibits particle agglomeration. The molar ratio of the total amount of metal ions to ammonium fluoride is preferably 1:1-1:2.5. Excessive fluoride ions may corrode the nickel foam substrate or generate metal fluoride by-products.

[0020] The second technical solution of the present invention is to provide an iron-molybdenum nitride hydrogen evolution catalyst prepared by the above preparation method.

[0021] The third technical solution of the present invention is to provide the use of the above-mentioned iron-molybdenum nitride hydrogen evolution catalyst in hydrogen evolution by electrolysis of water.

[0022] The technical solution of the present invention aims to effectively improve the catalytic performance and durability of the catalyst by simplifying the preparation process and optimizing the material structure and properties; the enhanced electrocatalytic activity is derived from the adjustable electronic structure and larger specific surface area of ​​the metal alloy, and the synergistic effect between different metals further optimizes the catalytic effect.

[0023] The present invention discloses the following technical effects:

[0024] The present invention successfully constructs a catalyst with a nanosheet structure by growing an iron-molybdenum double metal hydroxide layer on the surface of nickel foam. The nanosheet structure significantly increases the number of active sites and specific surface area, thereby enhancing the catalyst's adsorption performance for water molecules. Furthermore, nitrogen doping is achieved through high-temperature calcination, which not only further increases the number of active sites and electrochemical active area, but also optimizes the electronic structure inside the catalyst, significantly improving the efficiency of the hydrogen evolution reaction.

[0025] The preparation method of the present invention is simple and environmentally friendly, and the prepared hydrogen evolution catalyst has the following advantages:

[0026] (1) Low overpotential: reduces the starting voltage and improves the energy conversion efficiency.

[0027] (2) Excellent stability: ensuring stable performance during long-term use.

[0028] (3) Low cost: The use of economical and efficient materials and processes reduces production costs.

[0029] The above-mentioned properties enable the catalyst to exhibit excellent performance and broad application prospects in applications such as water electrolysis to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 The wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst prepared in Examples 1, 2, 3, and 4 of the present invention was subjected to a current density of 10 mA / cm 2 Overpotential comparison diagram when ;

[0032] Figure 2 is the SEM image of blank nickel foam;

[0033] Figure 3 This is a SEM image of the precursor catalyst prepared in Comparative Example 1;

[0034] Figure 4 In the figure, ad are SEM images of the wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalysts prepared in Examples 1, 2, 3, and 4, respectively;

[0035] Figure 5 TEM images and element distribution diagrams of the wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4; (a) is a transmission electron microscope (TEM) image of the nanosheet, (b) is a general spectrum of element distribution, (c) is a Fe element distribution diagram, (d) is a Mo element distribution diagram, (e) is a N element distribution diagram, and (f) is an O element distribution diagram;

[0036] Figure 6 The iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4 was heated to 10 mA / cm 2 Stability test it test curve chart;

[0037] Figure 7 Double-layer capacitance diagram of the iron-molybdenum nitride hydrogen evolution catalyst prepared in Examples 1, 2, 3, and 4 of the present invention;

[0038] Figure 8 The catalysts prepared in Example 4 and Comparative Examples 1, 2, 3 and 4 were 2 Overpotential comparison diagram when ;

[0039] Fig. 9The catalysts prepared in Example 4, Comparative Examples 5, 6 and 7 were 2 Overpotential comparison diagram when . DETAILED DESCRIPTION

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0044] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0045] Example 1

[0046] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0047] Step 2: Weigh 0.324 g (2.25 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL deionized water, and stir for 20 min.

[0048] Step 3: Place the nickel foam obtained in step 1 into the solution prepared in step 2, and then place the reaction system in a reactor for hydrothermal reaction at 150° C. for 4 hours.

[0049] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0050] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 2 hours.

[0051] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 hours to prepare a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst.

[0052] Example 2

[0053] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0054] Step 2: Weigh 0.432 g (3 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL deionized water, and stir for 20 min.

[0055] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 250° C. for 8 hours.

[0056] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0057] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 2 hours.

[0058] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 hours to prepare a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst.

[0059] Example 3

[0060] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0061] Step 2: Weigh 0.648 g (4.5 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL deionized water, and stir for 20 min.

[0062] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 300° C. for 12 hours.

[0063] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0064] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 2 hours.

[0065] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 hours to prepare a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst.

[0066] Example 4

[0067] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0068] Step 2: Weigh 0.540 g (3.75 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL deionized water, and stir for 20 min.

[0069] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0070] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0071] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 2 hours.

[0072] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 hours to prepare a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst.

[0073] Comparative Example 1

[0074] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0075] Step 2: Weigh 0.540 g (3.75 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL of deionized water, and stir for 20 min.

[0076] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0077] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h to obtain a hydrothermally formed precursor catalyst.

[0078] Comparative Example 2

[0079] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0080] Step 2: Weigh 0.540 g (3.75 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL deionized water, and stir for 20 min.

[0081] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0082] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0083] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 1 hour.

[0084] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 hours to prepare a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst.

[0085] Comparative Example 3

[0086] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0087] Step 2: Weigh 0.540 g (3.75 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL of deionized water, and stir for 20 min.

[0088] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0089] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0090] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 700°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 4 hours.

[0091] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 hours to prepare a wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst.

[0092] Comparative Example 4

[0093] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0094] Step 2: Weigh 0.540 g (3.75 mmol) MoO3, 0.406 g (1.5 mmol) FeCl3·6H2O, 0.222 g (6 mmol) NH4F and 0.48 g (8 mmol) CH4N2O, put them into the inner lining of a 100 mL reactor, add 70 mL of deionized water, and stir for 20 min.

[0095] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0096] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0097] Step 5: Place the precursor ceramic boat obtained in step 4 in a nitrogen atmosphere, heat the temperature to 550°C at a heating rate of 5°C / min, and calcine for 2 hours.

[0098] Step 6: Rinse the product obtained in step 5 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h to prepare an iron-molybdenum nitride hydrogen evolution catalyst.

[0099] Comparative Example 5

[0100] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0101] Step 2: Weigh 0.540 g (3.75 mmol) MoO3, 0.436 g (1.5 mmol) Co(NO3)2·6H2O, 0.222 g (6 mmol) NH4F, and 0.48 g (8 mmol) CH4N2O, put them into a 100 mL reactor liner, add 70 mL of deionized water, and stir for 20 min.

[0102] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0103] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0104] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 2 hours.

[0105] Step 6: The product obtained in step 5 is rinsed with ethanol, and then placed in a vacuum drying oven at 60° C. for 6 h to prepare a molybdenum-cobalt composite hydrogen evolution catalyst.

[0106] Comparative Example 6

[0107] Step 1: Place the nickel foam (2*4cm 2 ) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0108] Step 2: Weigh 0.406 g (1.5 mmol) FeCl3·6H2O , 0.436 g (1.5 mmol) Co(NO3)2·6H2O, 0.222 g (6 mmol) NH4F, and 0.48 g (8 mmol) CH4N2O were placed in a 100 mL reactor liner, and 70 mL of deionized water was added and stirred for 20 min.

[0109] Step 3: Place the nickel foam obtained in step 1 into the solution of step 2, and then place the reaction system in a reactor for hydrothermal reaction at 200° C. for 6 hours.

[0110] Step 4: Rinse the precursor obtained in step 3 with ethanol, and then place it in a vacuum drying oven at 60° C. for 6 h.

[0111] Step 5: Place 1 g of melamine and the precursor obtained in step 4 into the upstream and downstream of the porcelain boat respectively, and heat the temperature to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine for 2 hours.

[0112] Step 6: The product obtained in step 5 is rinsed with ethanol, and then placed in a vacuum drying oven at 60° C. for 6 h to prepare an iron-cobalt composite hydrogen evolution catalyst.

[0113] Comparative Example 7

[0114] Step 1: Place the nickel foam (2*4cm 2) were sequentially placed in 4M HCl, deionized water, and anhydrous ethanol solutions for ultrasonic treatment for 20 min, and then placed in a vacuum drying oven at 60 °C for 2 h.

[0115] Step 2: Disperse 40 mg of 20 wt% Pt / C powder in a mixture of Nafion / isopropanol (500 μL / 500 μL) and drop-coat it on the surface of nickel foam with a loading of 0.5 mg / cm².

[0116] The prepared wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalysts were tested for electrochemical performance using a three-electrode system on a CHI760E electrochemical workstation. The test conditions were 1 mol / L KOH as the electrolyte, the prepared catalyst as the working electrode, the graphite rod as the counter electrode, and the reference electrode as Hg / HgO.

[0117] Figure 1 The wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst prepared in Examples 1, 2, 3, and 4 of the present invention was subjected to a current density of 10 mA / cm 2 The overpotential comparison diagram when the overpotential reaches 10mA / cm 2 At a current density of , the wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst obtained in Example 4 requires the lowest hydrogen evolution overpotential of 46 mV.

[0118] Figure 2 This is a SEM image of blank nickel foam. It can be observed that its surface is smooth and has no attachments.

[0119] Figure 3 This is a SEM image of the precursor catalyst prepared in Comparative Example 1. Figure 3 It can be seen that only smooth nanosheet structures are formed on the precursor.

[0120] Figure 4 These are SEM images of the wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalysts prepared in Examples 1, 2, 3, and 4. Figure 4 In the figure, a, b, c, and d correspond to the microscopic morphologies of the catalysts prepared in Examples 1, 2, 3, and 4, respectively. By comparison, it can be seen that the catalyst in Example 4 presents a wrinkled nano-network microstructure and has a larger specific surface area.

[0121] Figure 5 TEM images and element distribution diagrams of the wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4; (a) is a transmission electron microscope (TEM) image of the nanosheet, (b) is a general element distribution spectrum, (c) is a Fe element distribution diagram, (d) is a Mo element distribution diagram, (e) is a N element distribution diagram, and (f) is an O element distribution diagram. Figure 4 It can be seen that Fe and Mo are evenly distributed on the surface of nickel foam.

[0122] Figure 6 The iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4 was heated to 10 mA / cm 2 The stability test it test curve diagram is shown. It can be seen from the figure that during the 10 h long cycle stability test, the current density remains basically unchanged, indicating that the iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4 has excellent stability.

[0123] Figure 7 The double-layer capacitance diagram of the iron-molybdenum nitride hydrogen evolution catalyst prepared in Examples 1, 2, 3, and 4 of the present invention. Figure 7 It can be qualitatively concluded that the iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4 has the highest electrochemical active area.

[0124] Figure 8 The catalysts prepared in Example 4 and Comparative Examples 1, 2, 3 and 4 were 2 As shown in the figure, Example 4 has the best effect, and the corresponding calcination temperature is 550°C; and for the nitrogen doping method, the performance of the catalyst prepared by using melamine as the nitrogen source is significantly better than that of the catalyst prepared by using nitrogen as the nitrogen source.

[0125] Fig. 9 The catalysts prepared in Example 4, Comparative Examples 5, 6 and 7 were 2 The overpotential comparison diagram at 10 mV / cm shows that under the same conditions, the combination of iron and molybdenum has a lower overpotential than iron and cobalt, and has better hydrogen evolution performance. In addition, at 10 mV / cm 2 Its overpotential (46 mV) is closer to commercial Pt / C (31 mV).

[0126] The catalyst prepared in Example 4 of the present invention has the best performance. Figure 1 Compared with the catalysts in other examples, its overpotential is the lowest (46 mV). Fig. 9 By comparing the overpotential of commercial Pt / C, it can be observed that the performance is close to that of commercial Pt / C (31 mV), which is better than other comparative examples, proving its excellent hydrogen evolution performance. Figure 6 As shown, at 10mA / cm 2 The stability test was carried out for 10 h under the current density, and the measured curve remained basically stable without obvious fluctuations, which proved that the wrinkled nano-mesh iron-molybdenum nitride hydrogen evolution catalyst prepared in Example 4 of the present invention has excellent stability and can be used for industrialization.

[0127] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing an iron-molybdenum nitride hydrogen evolution catalyst, characterized in that: The following steps are involved: (1) In-situ growth of iron and molybdenum on nickel foam material by hydrothermal synthesis to obtain a precursor material; (2) The precursor material is mixed with melamine, and calcined under a nitrogen atmosphere to obtain the iron-molybdenum nitride hydrogen evolution catalyst.

2. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal synthesis is 150-300° C. and the time is 4-12 h.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the iron element to the molybdenum element in the hydrothermal synthesis is 1:0.5-10.

4. The preparation method according to claim 1, characterized in that: The amount of melamine used per unit area of ​​the precursor is 20-200 mg cm -2 .

5. The preparation method according to claim 1, characterized in that: The calcination temperature is 300-800° C., and the calcination time is 1-4 hours.

6. The preparation method according to claim 1, characterized in that: The molybdenum source used in the hydrothermal synthesis is MoO3 or (NH4)6Mo7O 24 ·4H2O; the iron source used in the hydrothermal synthesis is FeCl3·6H2O or Fe(NO3)3·9H2O.

7. An iron-molybdenum nitride hydrogen evolution catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the iron-molybdenum nitride hydrogen evolution catalyst as claimed in claim 7 in hydrogen evolution by electrolysis of water.

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