Nitrogen-doped graphene-loaded ferromolybdenum monatomic electrode and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrodes, and particularly relates to a nitrogen-doped graphene loaded ferromolybdenum monatomic electrode and a preparation method and application thereof. According to the method, nitrogen-doped graphene is firstly subjected to vapor deposition on foamed nickel, iron-molybdenum single atoms are electrically deposited on the surface of the nitrogen-doped graphene, and a catalyst with the iron-molybdenum single atoms is anchored on a foamed nickel substrate and used as an anode for hydrogen production through water electrolysis for oxygen evolution (OER) reaction. According to the preparation method disclosed by the invention, not only is the use of an insulating binder avoided and the excellent electron transmission capability ensured, but also the three-dimensional porous structure greatly promotes electrolyte infiltration and rapid release of oxygen bubbles, and a synergistic electron effect of multi-element metal, the maximum atom utilization efficiency and an ideal mass transmission channel are combined, so that the preparation method has the advantages of simple process and low cost. And a solution with great application potential is provided for developing an efficient and low-cost water electrolysis hydrogen production anode.

Description

Technical Field

[0001] This invention belongs to the field of electrode technology. More specifically, it relates to a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode, its preparation method, and its application. Background Technology

[0002] In water electrolysis for hydrogen production, anion exchange membrane (AEM) electrolysis combines the advantages of traditional alkaline and proton exchange membrane electrolysis. It utilizes non-precious metal catalysts and achieves high current density operation, making it considered the most promising technology for industrialization. However, the oxygen evolution reaction (OER), a complex process involving four electron transfers, suffers from slow kinetics that severely limit the overall efficiency of water electrolysis. Developing efficient and stable non-precious metal OER catalysts has become a key breakthrough for advancing AEM water electrolysis technology. Currently, commercial catalysts mainly rely on precious metal materials (such as IrO2 and RuO2), but their high cost and scarcity severely restrict large-scale application. Therefore, developing alternative catalysts with high activity, high stability, and low cost is urgently needed.

[0003] To address this technological challenge, research has shifted towards developing high-performance catalysts based on non-precious metal materials, aiming to obtain alternative solutions with superior catalytic efficiency and stability. Single-atom catalysts achieve maximized atom utilization efficiency, with each metal atom becoming a potential active center and possessing a uniform coordination environment and electronic structure. This characteristic enables them to exhibit excellent performance in a variety of electrocatalytic reactions. However, the relatively simple structure of single-atom sites limits further enhancement of their catalytic mechanisms and activities. Therefore, research is gradually expanding towards diatomic catalysts. These catalysts construct synergistic active centers through two adjacent metal atoms, which can not only modulate the local electronic structure and enhance the adsorption and activation of reaction intermediates, but also enable the synergistic execution of multi-step reactions, providing more flexible and efficient solutions for complex electrocatalytic processes.

[0004] Nitrogen-doped graphene possesses advantages such as high electrical conductivity, excellent acid and alkali resistance, and tunable electronic structure; its unique sp... 2 The hybrid carbon framework provides an ideal channel for electron transport. The introduction of nitrogen atoms not only alters the electron distribution characteristics of carbon materials, creating more active sites, but also effectively anchors metal atoms to prevent aggregation through strong metal-support interactions. Studies have shown that single-atom dispersed metal species on nitrogen-doped graphene nanosheets exhibit impressive catalytic activity and stability for the oxygen evolution reaction, with their mass activity being more than an order of magnitude higher than that of traditional nanocatalysts. Furthermore, the nitrogen-doped graphene support possesses good mechanical strength and thermal stability, enabling it to withstand the mechanical and thermal stresses during the operation of the AEM electrolyzer, ensuring the structural integrity of the catalyst layer.

[0005] The nitrogen-doped graphene-supported molybdenum-iron single-atom electrode employs an advanced atomic interface engineering strategy. By precisely controlling the anchoring sites of molybdenum-iron single atoms on the nitrogen-doped graphene support, stable catalytic centers are formed. This design not only avoids the sintering and agglomeration of active components but also optimizes the adsorption energy of reaction intermediates through bimetallic synergistic effects, significantly reducing the reaction energy barrier.

[0006] Therefore, current research focuses on developing scalable catalyst electrodes. These electrodes should not only construct highly active sites to enhance catalytic performance but also avoid the use of precious metals to reduce material costs. Breakthroughs in this type of catalytic system are expected to drive the commercialization of AEM water electrolysis technology and provide crucial technological support for the development of a green hydrogen economy. Summary of the Invention

[0007] The technical problem this invention aims to solve is to overcome the defects and shortcomings of existing precious metal-dependent catalysts, such as high dependence on precious metals and single-atom catalyst active sites. It provides a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode, its preparation method, and its applications. The electrode prepared by the method of this invention not only avoids the use of insulating binders, ensuring excellent electron transport capabilities, but also its three-dimensional porous structure greatly promotes electrolyte wetting and rapid release of oxygen bubbles. Combining the synergistic electronic effects of multiple metals, maximum atom utilization efficiency, and ideal mass transport channels, it provides a highly promising solution for developing efficient and low-cost anodes for water electrolysis to produce hydrogen.

[0008] The purpose of this invention is to provide a method for preparing a molybdenum-iron single-atom electrode supported on nitrogen-doped graphene.

[0009] Another objective of this invention is to provide a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode.

[0010] Another objective of this invention is to provide an application of a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode in OER.

[0011] The above-mentioned objective of this invention is achieved through the following technical solution: A method for preparing a molybdenum-iron single-atom electrode supported on nitrogen-doped graphene, the method comprising the following steps: 1) Place the nickel foam in the high-temperature zone of the quartz tube in the tube CVD furnace, evacuate the system to a low vacuum, and then introduce Ar and H2 into the furnace for heat preservation. 2) A mixture of CH4 and NH3 gas was introduced into the reaction chamber as a carbon source and a nitrogen source, and growth was carried out at high temperature, while the Ar / H2 flow rate was adjusted as a carrier gas. 3) After growth is complete, quickly slide the quartz tube out of the heating zone and rapidly cool it to room temperature under the protection of Ar / H2 atmosphere; 4) Dissolve molybdate and ferrous salt in deionized water to prepare a precursor solution, and perform electrodeposition to obtain a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode.

[0012] Preferably, in step (1), the gas flow ratio of Ar to H2 is 8~12:1.

[0013] Preferably, in step (1), the nickel foam is placed in hydrochloric acid solution and sonicated for 5-15 min to remove surface oxides, and then ultrasonically cleaned with acetone, ethanol and deionized water for 10-20 min each.

[0014] Preferably, the thickness of the nickel foam is 0.4~0.6 mm and the porosity is 80~90%; the concentration of the hydrochloric acid is 1M.

[0015] Preferably, in step (2), the gas flow rate ratio of CH4 and NH3 is 2:1; and the volume fraction of H2 in Ar / H2 is 3~7%.

[0016] Preferably, in step (2), the specific process of growing at high temperature is to raise the temperature from room temperature to 900~1000℃, with a heating rate of 10~20℃ / min, and the growth time is controlled to be 8~12 min.

[0017] Preferably, in step (3), the volume fraction of H2 in the Ar / H2 is 3-7%.

[0018] Preferably, in step (4), the molybdate is one of ammonium molybdate, sodium molybdate, and potassium molybdate; the ferrous salt is one of ferrous sulfate, ferrous chloride, and ferrous acetate; the molybdate and ferrous salt are prepared with a metal ion concentration of 2~4 mg / mL according to a molybdenum to iron mass ratio of 1:2; and the electrodeposition conditions are deposition at a potential of -0.5 V to 0.5 V vs. Ag / AgCl for 10-30 min.

[0019] The nitrogen-doped graphene-supported molybdenum-iron single-atom electrode was prepared based on the above-described method for preparing a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode.

[0020] The application of nitrogen-doped graphene-supported molybdenum-iron single-atom electrodes in OER is based on the above description.

[0021] The present invention has the following beneficial effects: The method of this invention prepares a molybdenum-iron biatom electrode based on nitrogen-doped graphene, which has a simple production process and is suitable for large-scale production. The method of the present invention not only avoids the sintering and agglomeration of active components, but also adjusts the electronic structure through the bimetallic synergistic effect, optimizes the adsorption energy of reaction intermediates, and significantly reduces the reaction energy barrier. The high specific surface area and abundant pore structure of the catalyst in the method of this invention are beneficial to the mass transfer of reactants and products, while the uniformly distributed active sites ensure uniform current density distribution and avoid local overheating and concentration polarization problems. Atoms are directly anchored to the support surface by constant potential deposition (-0.5 V - 0.5 V vs. Ag / AgCl), avoiding atomic aggregation caused by high temperature treatment, while maintaining the structural integrity of the support. The method of this invention enables the large-scale preparation of nitrogen-doped graphene-supported molybdenum-iron diatomic catalyst electrodes. These electrodes have good compatibility and can be directly adapted to existing water electrolysis hydrogen production devices, serving as high-performance oxygen evolution reaction anodes for practical applications. Attached Figure Description

[0022] Figure 1 This is a comparison of the OER reaction performance of the nitrogen-doped graphene-supported molybdenum-iron diatomic catalyst electrode prepared in Example 1 with that of Comparative Examples 1, 2, and 3. Figure 2 This is a graph showing the OER reaction stability of the nitrogen-doped graphene-supported molybdenum-iron diatomic catalyst electrode prepared in Example 1. Figure 3 Using Example 1 as the anode, a commercially available Pt / C-assembled anion exchange membrane water electrolysis device achieved 1-11 A / cm at 40°C, 60°C, and 80°C. 2 The cell voltage corresponding to the current density; Figure 4 This is a stability performance diagram of the anion exchange membrane water electrolysis device assembled with Example 1 as the anode. Detailed Implementation

[0023] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0024] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0025] Example 1 A method for preparing a molybdenum-iron single-atom electrode supported on nitrogen-doped graphene, the method comprising the following steps: 1) Cut the nickel foam to the required size, and place it in 1 M hydrochloric acid solution for 10 minutes to remove surface oxides. Then, clean it with acetone, ethanol and deionized water for 15 minutes each. 2) Place the foamed nickel (thickness 0.5 mm, porosity 85%) treated in step (1) in the high temperature zone of the quartz tube of the tube CVD furnace, evacuate the system to a low vacuum, and then introduce Ar (500 sccm) and H2 (50 sccm) into the furnace. Raise the furnace temperature from room temperature to 950℃ at a rate of 15 ℃ / min and hold for 30 minutes. 3) Maintain 950℃, and introduce a mixture of CH4 (20 sccm) and NH3 (10 sccm) as the carbon and nitrogen sources into the reaction chamber. Control the growth time to 10 minutes, and adjust the flow rate of Ar / H2 (the volume fraction of H2 in the Ar / H2 is 5%) as the carrier gas. After the growth is completed, quickly slide the quartz tube out of the heating zone and rapidly cool it to room temperature under the protection of the Ar / H2 atmosphere (the volume fraction of H2 in the Ar / H2 is 5%). 4) Weigh ammonium molybdate and ferrous sulfate (prepared at a molybdenum to iron mass ratio of 1:2), dissolve them in 1 mL of deionized water, resulting in a total ion concentration of 3 mg / mL. Deposit the solution for 10 minutes at a potential of -0.5 V to 0.5 V vs. Ag / AgCl to obtain a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode. The molybdenum-iron atom loading was determined to be approximately 2.86 mg / cm³ by ICP testing. 2 .

[0026] Comparative Example 1 This embodiment is prepared according to steps 1) and 4) of Example 1, but without steps 2) and 3). The molybdenum-iron atom loading was found to be approximately 2.01 mg / cm³ by ICP testing. 2 .

[0027] Comparative Example 2 Comparative Example 2 provided a conventional RuO2 catalyst, which was ultrasonically dispersed in ethanol and then coated onto nickel foam, with a RuO2 loading of approximately 3 mg / cm³. 2 .

[0028] Comparative Example 3 Comparative Example 3 is the nickel foam (thickness 0.5 mm, porosity 85%) prepared in step 1).

[0029] Performance testing Test 1: OER performance tests were performed on Examples 1, 1, 2 and 3 respectively. The electrolytic cell was selected as the container, the test sample as the working electrode, the platinum wire as the auxiliary electrode, the Ag / AgCl electrode as the reference electrode, and the electrolyte as 1 M KOH solution. The tests were performed using an electrochemical workstation. All voltage ranges mentioned in this article are relative to the reversible hydrogen electrode (RHE).

[0030] OER performance test conditions: Temperature: room temperature; LSV scan rate: 10 mV / s; LSV test voltage range: 0 ~ 2.0V.

[0031] OER stability test conditions: Temperature: room temperature; Current density: 1 A / cm² 2 Test duration: 40 hours.

[0032] The results of the tests conducted using the methods and conditions described above are attached. Figure 1-2 As shown, from Figure 1-2 As can be seen, the nitrogen-doped graphene-supported molybdenum-iron diatomic catalyst electrode exhibits excellent OER catalytic performance and stability, achieving a current density of 1 A / cm². 2 The potential was 1.78 V, significantly better than the other comparative examples, and at a current density of 1 A / cm². 2 After undergoing an OER reaction for 40 hours, the electrode performance did not change significantly, and its stability was superior to that of commercial RuO2.

[0033] Test 2: Using Example 1 as the anode and commercial nickel felt loaded with commercial Pt / C as the cathode, an assembly was formed with an area of ​​130 cm². 2 In the AEM water electrolysis device, the current density ranges from 1 to 11 A / cm² under operating conditions of 40℃, 60℃, and 80℃. 2 It possesses excellent water electrolysis performance. At 1 A / cm 2 Even after operating at a high constant current density for more than 100 hours, the performance can still be maintained.

[0034] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a molybdenum-iron single-atom electrode supported on nitrogen-doped graphene, characterized in that: The preparation method includes the following steps: 1) Place the nickel foam in the high-temperature zone of the quartz tube in the tube CVD furnace, evacuate the system to a low vacuum, and then introduce Ar and H2 into the furnace for heat preservation. 2) A mixture of CH4 and NH3 gas was introduced into the reaction chamber as a carbon source and a nitrogen source, and growth was carried out at high temperature, while the Ar / H2 flow rate was adjusted as a carrier gas. 3) After growth is complete, quickly slide the quartz tube out of the heating zone and rapidly cool it to room temperature under the protection of Ar / H2 atmosphere; 4) Dissolve molybdate and ferrous salt in deionized water to prepare a precursor solution, and perform electrodeposition to obtain a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode.

2. The method for preparing a molybdenum-iron single-atom electrode based on nitrogen-doped graphene according to claim 1, characterized in that: In step (1), the gas flow ratio of Ar and H2 is 8~12:

1.

3. The method for preparing a molybdenum-iron single-atom electrode based on nitrogen-doped graphene according to claim 1, characterized in that: In step (1), the nickel foam is placed in hydrochloric acid solution and sonicated for 5-15 minutes to remove surface oxides, and then ultrasonically cleaned with acetone, ethanol and deionized water for 10-20 minutes each.

4. The method for preparing a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode according to claim 3, characterized in that: The nickel foam has a thickness of 0.4~0.6 mm and a porosity of 80~90%; the hydrochloric acid has a concentration of 1 M.

5. The method for preparing a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode according to claim 1, characterized in that: In step (2), the gas flow rate ratio of CH4 and NH3 is 2:1; the volume fraction of H2 in Ar / H2 is 3~7%.

6. The method for preparing a molybdenum-iron single-atom electrode based on nitrogen-doped graphene according to claim 1, characterized in that: In step (2), the specific process of growing at high temperature is to raise the temperature from room temperature to 900~1000℃, with a heating rate of 10~20℃ / min, and the growth time is controlled to be 8~12min.

7. The method for preparing a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode according to claim 1, characterized in that: In step (3), the volume fraction of H2 in the Ar / H2 is 3-7%.

8. The method for preparing a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode according to claim 1, characterized in that: In step (4), the molybdate is one of ammonium molybdate, sodium molybdate, and potassium molybdate; the ferrous salt is one of ferrous sulfate, ferrous chloride, and ferrous acetate; the molybdate and ferrous salt are prepared with a metal ion concentration of 2~4 mg / mL according to a molybdenum to iron mass ratio of 1:2; and the electrodeposition conditions are deposition at a potential of -0.5 V to 0.5 V vs. Ag / AgCl for 10-30 min.

9. The nitrogen-doped graphene-supported molybdenum-iron single-atom electrode prepared by the method for preparing a nitrogen-doped graphene-supported molybdenum-iron single-atom electrode according to any one of claims 1-8.

10. The application of the nitrogen-doped graphene-supported molybdenum-iron single-atom electrode according to claim 9 in OER.

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