A method for preparing and application of boron and nitrogen co-doped molybdenum carbide
By preparing boron and nitrogen co-doped molybdenum carbide materials using ammonium molybdate and SiO2@C, the problems of high cost of precious metal catalysts and complex synthesis of traditional porous structures are solved, realizing a low-cost and high-efficiency catalyst for hydrogen production by water electrolysis, which is suitable for the field of hydrogen production by electrolysis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-14
- Publication Date
- 2026-04-07
AI Technical Summary
Existing precious metal catalysts are expensive, have limited reserves, and are prone to agglomeration. Traditional porous structure synthesis processes are cumbersome and costly, which limits the application of transition metal materials in water electrolysis for hydrogen production.
Using ammonium molybdate and SiO2@C as precursors, and adding nitrogen and boron sources, boron and nitrogen co-doped molybdenum carbide materials were prepared in one step by molten salt calcination to form a porous network structure. The electronic structure was then controlled to improve catalytic activity.
A low-cost, highly stable, and highly catalytically active boron and nitrogen co-doped molybdenum carbide material was developed. When producing hydrogen by electrolysis of water, the overpotential is only 65.8 mV at a current density of 10 mA cm⁻², and the electrolysis energy consumption is low, making it suitable for industrial applications.
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Figure CN116654937B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrolytic hydrogen production catalyst preparation technology, specifically relating to a method for preparing and applying boron and nitrogen co-doped molybdenum carbide. Background Technology
[0002] The information disclosed in this background section is intended to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
[0003] With the increasing severity of environmental degradation and resource scarcity on Earth, the development of a clean and efficient renewable energy source is urgently needed. Hydrogen energy, with its abundant reserves, zero greenhouse gas emissions, and high efficiency, has become the most promising green energy source of the 21st century. Among various hydrogen production methods, water electrolysis is considered a promising and sustainable way to produce high-purity hydrogen. Although noble metal-based catalysts possess high catalytic activity, their high cost, limited reserves, and resistance to degradation restrict their large-scale application.
[0004] Transition metal materials are widely used in the energy sector due to their low cost, high abundance, and strong corrosion resistance in alkaline environments. However, their application in water electrolysis is limited by drawbacks such as easy agglomeration during sintering and performance inferior to precious metals. Currently, there are two main strategies to effectively improve catalyst performance: one is to enhance the intrinsic activity of each active site, such as composition optimization, strain engineering, and crystal facet adjustment; the other is to increase the number of effective active sites given a fixed active surface area, such as through heteroatom doping.
[0005] It has been reported that heteroatom doping can improve catalytic performance by modulating the electronic structure of materials. B, N co-doping, in particular, enhances catalytic activity by causing charge density redistribution and asymmetric spin due to the electronegativity of heteroatoms. Traditional methods for constructing porous structures typically involve top-down self-assembly. However, this method is not only cumbersome in its synthesis process but also characterized by high cost and high energy consumption, hindering its application and widespread adoption in industrial production. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a method for preparing and applying boron-nitrogen co-doped molybdenum carbide. Compared to existing methods for synthesizing porous structures, the method of this invention only requires ammonium molybdate as the molybdenum source, adding a self-made carbon source SiO2@C and stirring to form a precursor, followed by the addition of a nitrogen source and a boron source and calcination with molten salt in one step. The resulting porous boron-nitrogen co-doped molybdenum carbide material is not only structurally stable and homogeneous but also low in cost. Furthermore, this material exhibits excellent catalytic activity as a hydrogen evolution catalyst. To achieve the above objectives, this invention discloses the following technical solution:
[0007] In a first aspect of the invention, a boron-nitrogen co-doped molybdenum carbide material is provided, comprising a hierarchical porous network structure formed by stacking molybdenum carbide.
[0008] Furthermore, the boron-nitrogen co-doped molybdenum carbide exhibits a charge density redistribution and asymmetric spin due to the modulation of its electronic structure by boron and nitrogen doping. Simultaneously, the porous structure exposes more effective active sites, ensuring the high catalytic activity and high stability of the boron-nitrogen co-doped molybdenum carbide.
[0009] In a second aspect of the present invention, a method for providing a boron-nitrogen co-doped molybdenum carbide material is provided, comprising the following steps:
[0010] (1) Mix the precursor, urea, boric acid and soluble molten salt evenly to obtain a mixed powder.
[0011] The mixed powder is heated to melt in a protective atmosphere and kept at that temperature. After the process is complete, the soluble molten salt in the solid product is removed to obtain the final product.
[0012] Further, in step (1), the mass ratio of the precursor, urea, and boric acid is 3:2:1. Further, in step (1), the soluble molten salt includes at least one of NaCl, KCl, CaCl2, ZnCl2, and LiCl. In this invention, the soluble molten salt serves as a reaction medium, preventing the collapse of the condensed carbon material (sol-carbon) formed in the first stage, thereby facilitating the preparation of inorganic materials. The strong polarization force generated during the reaction in the molten salt system can reduce the stability of metals, ions, or covalent bonds.
[0013] Further, in step (1), the precursor is prepared by stirring a mixture of ammonium molybdate solution, PDA, SiO2 beads, and Tris buffer solution, followed by centrifugation with deionized water and ethanol, repeated three times. The resulting lower precipitate is then freeze-dried to obtain the product.
[0014] In this invention, the role of the PDA powder is to produce a self-polymerization effect when using SiO2 as a template to synthesize the precursor, ultimately forming a spherical precursor.
[0015] Furthermore, in step (2), it is preferable that the heating temperature is controlled between 900°C and the holding time is controlled between 4 and 6 hours. In this step, when the temperature rises to the eutectic point of the molten salt system, the molten salt changes from solid to liquid and acts as a molecular template to form the main micropores, transforming the small spherical precursor into a porous network structure.
[0016] Further, in step (2), the protective atmosphere includes any one of ammonia, nitrogen, argon, and helium, preferably nitrogen or argon. The molten salt reaction requires the heated mixture to react under an inert atmosphere to ensure that the carbonized precursor powder is immersed / dissolved in the liquid salt and is not interfered with by air oxidation.
[0017] Further, in step (2), after the heat preservation is completed, the obtained solid product is added to water to dissolve the solidified soluble molten salt, and then the solid is separated and washed with water and vacuum dried to obtain the boron and nitrogen co-doped molybdenum carbide material.
[0018] In a third aspect of the invention, the application of the boron-nitrogen co-doped molybdenum carbide in electrolytic hydrogen production is provided. Preferably, it is used as a catalyst in electrolytic hydrogen production.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] (1) The present invention adopts a simple and safe preparation process using a liquid phase system and a two-step method of molten salt calcination to realize a porous structure of boron and nitrogen co-doped molybdenum carbide. This porous structure exposes more effective active sites, ensuring that the boron and nitrogen co-doped molybdenum carbide of the present invention has excellent catalytic activity and stability.
[0021] (2) The experimental results show that at a current density of 10 mA cm⁻¹, -2 At this time, the HER overpotential is only 65.8 mV. Compared with traditional noble metal catalysts, it not only produces more hydrogen but also consumes less energy for electrolysis, which can meet the needs of large-scale industrial water electrolysis for hydrogen production. In addition, when used as an electrocatalytic electrode material, the hydrogen evolution catalyst obtained by the molten salt method exhibits good dispersibility compared to catalysts synthesized by single hydrothermal methods, which are prone to particle agglomeration. Attached Figure Description
[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein:
[0023] Figure 1 The images are XRD images of BN-Mo2C prepared in Examples 1-3 and Comparative Examples 1-3.
[0024] Figure 2 The images are SEM images of BN-Mo2C prepared in Example 1 at different magnifications.
[0025] Figure 3 The images are SEM images of BN-Mo2C prepared in Example 2 at different magnifications.
[0026] Figure 4 The images are SEM images of BN-Mo2C prepared in Example 3 at different magnifications.
[0027] Figure 5 SEM images of BN-Mo2C prepared for Comparative Example 1 at different magnifications.
[0028] Figure 6 SEM images of BN-Mo2C prepared for Comparative Example 2 at different magnifications.
[0029] Figure 7 SEM images of BN-Mo2C prepared in Comparative Example 3 at different magnifications.
[0030] Figure 8 The HER linear sweep voltammetry curves of the BN-Mo2C catalysts prepared in Examples 1-3 and Comparative Examples 1-3 in 1 mol / L KOH electrolyte are shown. Detailed Implementation
[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.
[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods or product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only. The invention will now be further described with reference to the accompanying drawings and specific embodiments.
[0033] Example 1
[0034] A method for preparing boron-nitrogen co-doped molybdenum carbide based on the molten salt method includes the following steps:
[0035] (1) 0.632g of trihydroxyaminomethane (C4H) 11 NO3 is added to 500 mL of deionized water to form solution A. 1 mL of hydrochloric acid (HCl) is added to 1 mL of deionized water to form solution B.
[0036] (2) Slowly add solution B from step (1) into A until the pH reaches 8.5 to obtain Tris buffer.
[0037] (3) Take out 100 mL of the Tris buffer from step (2), add 0.2 g SiO2 microspheres and 0.6 g dopamine hydrochloride (PDA) to 100 mL of buffer and stir for 10 h. Then add 0.3 g ammonium molybdate to the mixed solution and stir for 10 h.
[0038] (4) Centrifuge the mixture obtained in step (3) with deionized water and ethanol (6500 rpm, 5 min), discard the supernatant, and repeat three times. Freeze-dry the resulting lower precipitate, and the final black powder is the precursor.
[0039] (5) Take 0.3g of the precursor obtained in step (4) and put it into a mortar. Add 2g of a mixture of NaCl and KCl, 0.2g of urea and 0.1g of boric acid. Grind at room temperature for 30 minutes to form a uniform powder for later use.
[0040] (6) The mixed powder obtained in step (5) is placed in a tube furnace and calcined at high temperature under a nitrogen atmosphere. The calcination temperature is 900°C. After calcination at high temperature for 3 hours, it is cooled to room temperature and then washed with 3 M NaOH overnight. Finally, it is dissolved by standing with deionized water for 12 hours. The dissolved sample is filtered, washed, and finally placed in a 60° vacuum drying oven to dry, thus obtaining the boron and nitrogen co-doped molybdenum carbide material, denoted as BN-Mo2C-1.
[0041] Example 2
[0042] A method for preparing boron-nitrogen co-doped molybdenum carbide based on the molten salt method includes the following steps:
[0043] (1) 0.632g of trihydroxyaminomethane (C4H) 11 NO3 is added to 500 mL of deionized water to form solution A. 1 mL of hydrochloric acid (HCl) is added to 1 mL of deionized water to form solution B.
[0044] (2) Slowly add solution B from step (1) into A until the pH reaches 8.5 to obtain Tris buffer.
[0045] (3) Take out 100 mL of the Tris buffer from step (2). Add 0.2 g SiO2 microspheres and 0.6 g dopamine hydrochloride (PDA) to 100 mL of buffer and stir for 10 h. Then add 0.3 g ammonium molybdate to the mixed solution and stir for 10 h.
[0046] (4) Centrifuge the mixture obtained in step (3) with deionized water and ethanol (6500 rpm, 5 min), discard the supernatant, and repeat three times. Freeze-dry the resulting lower precipitate, and the final black powder is the precursor.
[0047] (5) Take 0.1g of the precursor obtained in step (4) and put it into a mortar. Add 2g of a mixture of NaCl and KCl, 0.2g of urea and 0.1g of boric acid. Grind at room temperature for 30 minutes to form a uniform powder for later use.
[0048] (6) The mixed powder obtained in step (5) is placed in a tube furnace and calcined at high temperature under a nitrogen atmosphere. The calcination temperature is 900°C. After calcination at high temperature for 3 hours, it is cooled to room temperature and then washed with 3 M NaOH overnight. Finally, it is dissolved by standing with deionized water for 12 hours. The dissolved sample is filtered, washed, and finally placed in a 60° vacuum drying oven to dry, thus obtaining the boron and nitrogen co-doped molybdenum carbide material, denoted as BN-Mo2C-2.
[0049] Example 3
[0050] (1) 0.632g of trihydroxyaminomethane (C4H) 11 NO3 is added to 500 mL of deionized water to form solution A. 1 mL of hydrochloric acid (HCl) is added to 1 mL of deionized water to form solution B.
[0051] (2) Slowly add solution B from step (1) into A until the pH reaches 8.5 to obtain Tris buffer.
[0052] (3) Take out 100 mL of the Tris buffer from step (2). Add 0.2 g SiO2 beads and 0.3 g dopamine hydrochloride (PDA) to 100 mL of buffer and stir for 10 h. Then add 0.3 g ammonium molybdate to the mixed solution and stir for 10 h.
[0053] (4) Centrifuge the mixture obtained in step (3) with deionized water and ethanol (6500 rpm, 5 min), discard the supernatant, and repeat three times. Freeze-dry the resulting lower precipitate, and the final black powder is the precursor.
[0054] (5) Take 0.3g of the precursor obtained in step (4) and put it into a mortar. Add 2g of a mixture of NaCl and KCl, 0.2g of urea and 0.1g of boric acid. Grind at room temperature for 30 minutes to form a uniform powder for later use.
[0055] (6) The mixed powder obtained in step (5) is placed in a tube furnace and calcined at high temperature under a nitrogen atmosphere. The calcination temperature is 900°C. After calcination at high temperature for 3 hours, it is cooled to room temperature and then washed with 3 M NaOH overnight. Finally, it is dissolved by standing with deionized water for 12 hours. The dissolved sample is filtered, washed, and finally placed in a 60° vacuum drying oven to dry, thus obtaining the boron and nitrogen co-doped molybdenum carbide material, denoted as BN-Mo2C-3.
[0056] Comparative Example 1
[0057] (1) 0.632g of trihydroxyaminomethane (C4H) 11 NO3 is added to 500 mL of deionized water to form solution A. 1 mL of hydrochloric acid (HCl) is added to 1 mL of deionized water to form solution B.
[0058] (2) Slowly add solution B from step (1) into A until the pH reaches 8.5 to obtain Tris buffer.
[0059] (3) Take out 100 mL of the Tris buffer from step (2). Add 0.2 g SiO2 microspheres and 0.6 g dopamine hydrochloride (PDA) to 100 mL of buffer and stir for 10 h. Then add 0.3 g ammonium molybdate to the mixed solution and stir for 10 h.
[0060] (4) Centrifuge the mixture obtained in step (3) with deionized water and ethanol (6500 rpm, 5 min), discard the supernatant, and repeat three times. Freeze-dry the resulting lower precipitate, and the final black powder is the precursor.
[0061] (5) Take 0.1g of the precursor obtained in step (4) and put it into a mortar. Add 2g of a mixture of NaCl and KCl, 0.2g of urea and 0.1g of boric acid. Grind at room temperature for 30 minutes to form a uniform powder for later use.
[0062] (6) The mixed powder obtained in step (5) is placed in a tube furnace and calcined at high temperature under a nitrogen atmosphere. The calcination temperature is 800°C. After calcination at high temperature for 3 hours, it is cooled to room temperature and then washed with 3 M NaOH overnight. Finally, it is dissolved by standing with deionized water for 12 hours. The dissolved sample is filtered, washed, and finally placed in a 60° vacuum drying oven to dry, thus obtaining the boron and nitrogen co-doped molybdenum carbide material, denoted as BN-Mo2C-4.
[0063] Comparative Example 2
[0064] (1) 0.632g of trihydroxyaminomethane (C4H) 11NO3 is added to 500 mL of deionized water to form solution A. 1 mL of hydrochloric acid (HCl) is added to 1 mL of deionized water to form solution B.
[0065] (2) Slowly add solution B from step (1) into A until the pH reaches 8.5 to obtain Tris buffer.
[0066] (3) Take out 100 mL of the Tris buffer from step (2). Add 0.2 g SiO2 beads and 0.6 g dopamine hydrochloride (PDA) to 100 mL of buffer and stir for 5 h. Then add 0.3 g ammonium molybdate to the mixture and stir for 10 h.
[0067] (4) Centrifuge the mixture obtained in step (3) with deionized water and ethanol (6500 rpm, 5 min), discard the supernatant, and repeat three times. Freeze-dry the resulting lower precipitate, and the final black powder is the precursor.
[0068] (5) Take 0.3g of the precursor obtained in step (4) and put it into a mortar. Add 2g of a mixture of NaCl and KCl, 0.2g of urea and 0.1g of boric acid. Grind at room temperature for 30 minutes to form a uniform powder for later use.
[0069] (6) The mixed powder obtained in step (5) is placed in a tube furnace and calcined at high temperature under a nitrogen atmosphere. The calcination temperature is 1000°C. After calcination at high temperature for 3 hours, it is cooled to room temperature and then washed with 3 M NaOH overnight. Finally, it is dissolved by standing with deionized water for 12 hours. The dissolved sample is filtered, washed, and finally placed in a 60° vacuum drying oven to dry, thus obtaining the boron and nitrogen co-doped molybdenum carbide material, denoted as BN-Mo2C-5.
[0070] Comparative Example 3
[0071] (1) 0.632g of trihydroxyaminomethane (C4H) 11 NO3 is added to 500 mL of deionized water to form solution A. 1 mL of hydrochloric acid (HCl) is added to 1 mL of deionized water to form solution B.
[0072] (2) Slowly add solution B from step (1) into A until the pH reaches 8.5 to obtain Tris buffer.
[0073] (3) Take 100 mL of the Tris buffer from step (2). Add 0.6 g of dopamine hydrochloride (PDA) to 100 mL of buffer and stir for 8 h. Then add 0.3 g of ammonium molybdate to the mixture and stir for 8 h.
[0074] (4) Centrifuge the mixture obtained in step (3) with deionized water and ethanol (6500 rpm, 5 min), discard the supernatant, and repeat three times. Freeze-dry the resulting lower precipitate, and the final black powder is the precursor.
[0075] (5) Take 0.3g of the precursor obtained in step (4) and put it into a mortar. Add 2g of a mixture of NaCl and KCl, 0.2g of urea and 0.1g of boric acid. Grind at room temperature for 30 minutes to form a uniform powder for later use.
[0076] (6) The mixed powder obtained in step (5) is placed in a tube furnace and calcined at high temperature under a nitrogen atmosphere. The calcination temperature is 900°C. After calcination at high temperature for 3 hours, it is cooled to room temperature and then washed with 3 M NaOH overnight. Finally, it is dissolved by standing with deionized water for 12 hours. The dissolved sample is filtered, washed, and finally placed in a 60° vacuum drying oven to dry, thus obtaining the boron and nitrogen co-doped molybdenum carbide material, denoted as BN-Mo2C-6.
[0077] Figure 1 The images show the XRD patterns of BN-Mo2C prepared in Examples 1-3 and Comparative Examples 1-3. As can be seen from the figures, this invention successfully prepared molybdenum carbide, which exhibits a porous network structure, providing more active sites and helping to improve its hydrogen evolution performance as a catalyst, thereby increasing hydrogen evolution yield.
[0078] from Figures 2-4 It can be seen that in the boron and nitrogen co-doped molybdenum carbide materials prepared in each embodiment, the molybdenum carbide maintains the spherical morphology before the transformation, and after sintering in the molten salt system, the spherical precursor has become a hollow cavity, which, after being connected, further forms a special porous network structure. This morphology provides more active sites for the catalyst.
[0079] from Figure 5 It can be seen that the boron and nitrogen co-doped molybdenum carbide material BN-Mo2C-4 prepared in Comparative Example 1 exhibits uneven distribution, which is due to insufficient sintering temperature and a small number of precursors.
[0080] from Figure 6 It can be seen that the boron and nitrogen co-doped molybdenum carbide material BN-Mo2C-5 prepared in Comparative Example 2 exhibits agglomeration, which is due to insufficient sintering temperature and insufficient stirring time.
[0081] from Figure 7 It can be seen that the boron and nitrogen co-doped molybdenum carbide material BN-Mo2C-6 prepared in Comparative Example 3 did not exhibit a porous structure. This is because SiO2 was not used as a template, resulting in the final material being a stacked particle.
[0082] Figure 8 The HER linear sweep voltammetry curves of the BN-Mo2C catalysts prepared in Examples 1-3 and Comparative Examples 1-3 in 1 mol / L KOH electrolyte are shown. Hydrogen production experiment by water electrolysis: An electrochemical workstation was used as the electrochemical generator, and a three-electrode system was employed for testing. The prepared molybdenum carbide / carbon catalyst was used as the working electrode, graphite as the counter electrode, and a mercury-mercuric chloride electrode as the reference electrode, assembling an electrolytic hydrogen generator. A 1 mol / L KOH solution was added to the electrolytic cell to carry out the water electrolysis reaction. The test voltage range was -0.8 to -1.5 V, the scan rate was 10 mV / s, and the relationship between current density and overpotential was tested. Specifically, at 10 mA / cm²... -2 The overpotential test results at the location are as follows Figure 8 As shown, it can be seen that the overpotentials of the three embodiments are all lower than those of the comparative example. In particular, the overpotential of Example 1 as the working electrode is only 128mV, indicating that it has excellent catalytic performance.
[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a boron-nitrogen co-doped molybdenum carbide material, characterized in that, The boron-nitrogen co-doped molybdenum carbide material comprises a multi-level porous network structure formed by molybdenum carbide stacking; boron and nitrogen doping induce charge density redistribution and asymmetric spin in the molybdenum carbide material. The preparation method comprises the following steps: (1) Mix the precursor, urea, boric acid and soluble molten salt evenly to obtain a mixed powder; the mass ratio of the precursor, urea and boric acid is 3:2:1; the preparation method of the precursor is as follows: stir the mixture of ammonium molybdate solution, PDA, SiO2 beads and Tris buffer, then centrifuge it with deionized water and ethanol, repeat three times, and freeze-dry the resulting lower precipitate to obtain the powder. (2) The mixed powder is heated to melt in a protective atmosphere and kept at that temperature. After the process is completed, the soluble molten salt in the solid product is removed to obtain the final product.
2. The preparation method according to claim 1, characterized in that, The soluble molten salt includes at least one of NaCl, KCl, CaCl2, ZnCl2, and LiCl.
3. The preparation method according to claim 1, characterized in that, In step (2), the heating temperature is controlled at 900℃ and the heat preservation time is controlled at 4~6 hours.
4. The preparation method according to claim 1, characterized in that, In step (2), the protective atmosphere is nitrogen or argon.
5. The preparation method according to claim 1, characterized in that, In step (2), after the heat preservation is completed, the obtained solid product is added to water to dissolve the solidified soluble molten salt. Then, the solid is separated and washed with clean water and vacuum dried to obtain the boron and nitrogen co-doped molybdenum carbide material.
6. The application of the boron-nitrogen co-doped molybdenum carbide material prepared by the method according to any one of claims 1-5, characterized in that, The boron and nitrogen co-doped molybdenum carbide is used for electrolytic hydrogen production.
7. The application according to claim 6, characterized in that, The boron and nitrogen co-doped molybdenum carbide is used as a catalyst for electrolytic hydrogen production.