Preparation method of nano-porous ni-bi alloy catalyst for nitrogen reduction
By preparing a nanoporous NiBi alloy catalyst, the problems of difficulty in breaking N2 molecules and insufficient electron supply in the electrocatalytic nitrogen reduction reaction were solved, achieving high-activity and high-selectivity NH3 production with good stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TAIYUAN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2023-03-22
- Publication Date
- 2026-04-10
AI Technical Summary
In existing electrocatalytic nitrogen reduction reactions, N2 molecules are difficult to break down, the formation of intermediate *NNH is limited, the yield of NH3 and Faraday efficiency are low, and the electron supply on the catalyst surface is insufficient, resulting in poor NRR rate and selectivity.
Nanoporous NiBi alloy catalysts were prepared by alloying Ni and Bi, combined with vacuum induction melting and chemical dealloying techniques, to form a three-dimensional continuous porous structure, providing more active sites, reducing the reaction energy barrier, and suppressing hydrogen evolution side reactions.
It improves the activity and selectivity of electrocatalytic nitrogen reduction reaction, enhances catalyst stability, and increases the yield of NH3 and Faraday efficiency.
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Figure CN116288480B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of electrocatalytic nitrogen synthesis ammonia, and particularly relates to a preparation method of a nano-porous NiBi alloy catalyst for nitrogen reduction. BACKGROUND
[0002] With the increasing depletion of fossil energy, mankind is facing more and more serious energy crisis and environmental pollution problems, and developing clean energy is an important means for mankind to realize sustainable development. Ammonia (NH3) as the second largest synthetic chemical in the world, its energy density is 4.3kWh kg -1 , and the hydrogen content is as high as 17.6%, which can be used as clean energy to replace fossil fuels. At the same time, ammonia also plays an important role in industry, agriculture and biomedicine. So far, the large-scale production of NH3 is heavily dependent on the Haber-Bosch process. However, the process requires harsh conditions, consumes a huge amount of energy, and produces a large amount of carbon dioxide, which has a serious impact on the climate and environment. Therefore, it is of great significance to explore sustainable and environmentally friendly artificial nitrogen fixation strategies.
[0003] Electrocatalytic nitrogen reduction (NRR) reaction uses nitrogen and water as raw materials and renewable electrical energy as driving force, which can stably produce NH3 at room temperature, completely getting rid of the dependence on fossil energy. However, the N≡N bond in N2 molecule is as high as 941kJ mol -1 , which is difficult to break, so the rate-determining step of NRR, i.e. the formation of intermediate *NNH, is limited. At the same time, in the reaction process, N2 adsorption is difficult, and competes fiercely with hydrogen evolution reaction (HER), resulting in low NH3 yield and faradic efficiency. Non-noble metals show a broader application prospect due to their abundant reserves, low price and good catalytic activity. The metal center of transition metal unoccupied d orbit can receive the lone pair of electrons of N2 molecule, and the electrons on the occupied d orbit can be provided to the antibonding orbital of N2 in reverse to weaken N≡N. The 6p orbit of main group metal Bi has a strong interaction with the 2p orbit of N, and the semiconductor property of Bi itself limits the supply of surface electrons, which can effectively inhibit the hydrogen evolution activity and improve the selectivity of NRR. And studies have shown that Bi can reduce the reaction energy barrier in the first protonation process of nitrogen reduction. Alloying transition metal Ni with main group metal Bi can exhibit excellent nitrogen reduction activity and selectivity. In addition, the unique three-dimensional continuous nano-porous structure can have a larger specific surface area, so that more active sites are exposed on the surface of the catalyst, and the electron transfer and mass transfer in the reaction process are promoted. Therefore, designing a new catalyst with high activity and high selectivity is an important prerequisite for application in electrocatalytic nitrogen reduction. SUMMARY
[0004] The purpose of the present application is to prepare a nanoporous NiBi alloy catalyst and apply it to the electrocatalytic nitrogen reduction reaction. The nanoporous structure has a large specific surface area to provide sufficient catalytically active sites. The Ni phase in the NiBi alloy cooperates with the NiBi phase to effectively reduce the reaction energy barrier of the rate-determining step in the NRR process and inhibit the hydrogen evolution side reaction. Therefore, the NiBi alloy catalytic material of the present application has excellent NRR catalytic activity and good stability.
[0005] To achieve the above purpose, the present application adopts the following technical solution:
[0006] A preparation method of a nanoporous NiBi alloy catalyst for nitrogen reduction, comprising the following steps:
[0007] (1) First, clean the Al particles with a purity of 99.99%, the Ni particles with a purity of 99.99%, and the Bi particles with a purity of 99.99% with dilute HCl to remove the surface oxides;
[0008] (2) Weigh the metal particles according to a certain atomic ratio, mix the weighed metal particles uniformly, and then place them in the heating coil of an induction vacuum melting furnace. Use a mechanical pump and a vacuum pump to vacuumize to 1x10 -3 ~ 4x10 -3 Pa, introduce Ar as a protective gas, and repeatedly melt 3-5 times under high temperature conditions to obtain an alloy ingot with uniform composition. After cooling, take it out;
[0009] (3) Place the alloy ingot in step (2) in an induction vacuum melting furnace, vacuumize to 1x10 -3 ~ 4x10 -3 Pa, introduce Ar as a protective gas, start the speed regulation motor, and when the copper roller reaches a speed of 2000-3500 rpm, prepare the alloy ingot into a strip under the action of the induction heating device and the vacuum rapid solidification tape casting device;
[0010] (4) Put the alloy strip in step (3) into a 3-6M NaOH solution for chemical dealloying. After 12-48 hours, take out the sample and wash away the impurities. Collect the cleaned sample and vacuum dry it at a certain temperature to obtain a nanoporous NiBi alloy catalytic material;
[0011] (5) Use an electrochemical workstation to test under a three-electrode system. Use carbon paper coated with nanoporous NiBi alloy catalyst as the working electrode, Ag / AgCl as the reference electrode, platinum sheet electrode as the counter electrode, and Na2SO4 solution as the electrolyte. Under the condition of nitrogen gas, perform the nitrogen gas synthesis ammonia reaction. The potential setting range is -0.1 to -0.9V vs. RHE.
[0012] The technical effect of the present application is:
[0013] The preparation method described in the present application combines alloy design and dealloying method to convert bulk alloy into nano-porous electrocatalytic material with high specific surface area. The alloy ingot with uniform composition is obtained by using vacuum induction melting furnace, the alloy ingot is prepared into alloy strip through single roll strip casting device, and then Al element is removed through dealloying technology to obtain NiBi alloy catalyst material. The preparation method is simple and efficient, and the prepared alloy material is nano-porous structure, which increases the active area of the catalyst.
[0014] The nano-porous NiBi alloy catalyst material for nitrogen reduction provided by the present application includes the following elements: Al element, Ni element and Bi element. The NiBi alloy electrocatalyst provided by the present application reduces the reaction energy barrier of the rate-determining step, suppresses the hydrogen evolution side reaction to improve the catalytic efficiency, has high activity, high selectivity and excellent stability, and has good development prospect. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 The digital photograph of the nano-porous NiBi alloy catalyst prepared in Example 1.
[0016] Figure 2 The SEM graph of the nano-porous NiBi alloy catalyst prepared in Example 1.
[0017] Figure 3 The XRD graph of the nano-porous NiBi alloy catalyst prepared in Example 1.
[0018] Figure 4 The nitrogen reduction performance test result graph of the nano-porous NiBi alloy catalyst prepared in Example 1 at-0.2~-0.6V vs. RHE.
[0019] Figure 5 The digital photograph of the nano-porous NiBi alloy catalyst prepared in Example 2.
[0020] Figure 6 The SEM graph of the nano-porous NiBi alloy catalyst prepared in Example 2.
[0021] Figure 7 The XRD graph of the nano-porous NiBi alloy catalyst prepared in Example 2.
[0022] Figure 8 The nitrogen reduction performance test result graph of the nano-porous NiBi alloy catalyst prepared in Example 2 at-0.2~-0.6V vs. RHE.
[0023] Figure 9A digital photo of the nano-porous NiBi alloy catalyst prepared in Example 3.
[0024] Figure 10 A SEM photo of the nano-porous NiBi alloy catalyst prepared in Example 3.
[0025] Figure 11 A XRD photo of the nano-porous NiBi alloy catalyst prepared in Example 3.
[0026] Figure 12 A graph of the nitrogen reduction performance test results of the nano-porous NiBi alloy catalyst prepared in Example 3 at -0.2 ~ -0.6 V vs. RHE. DETAILED DESCRIPTION
[0027] In order to better understand the present application, the present application is further described below by combining examples, but the embodiments of the present application are not limited thereto. Other examples obtained by those skilled in the art without making creative efforts are all within the scope of protection of the present application.
[0028] Example 1:
[0029] (1) First, the Al particles with a purity of 99.99%, the Ni particles with a purity of 99.99% and the Bi particles with a purity of 99.99% are cleaned with dilute HCl to remove the surface oxides;
[0030] (2) According to the atomic percentage of Al:Ni:Bi being 90:9.15:0.85, high-purity Al particles 7.73 g, high-purity Ni particles 1.71 g and high-purity Bi particles 0.56 g are weighed. The weighed metal particles are mixed uniformly and then placed in the heating coil of an induction vacuum melting furnace, vacuum is drawn to 2x10 -3 Pa by using a mechanical pump and a vacuum pump, Ar is introduced as a protective gas, and the alloy ingot with uniform composition is obtained by repeatedly melting 3-5 times under high temperature conditions, and the alloy ingot is taken out after cooling;
[0031] (3) The above alloy ingot is placed in the induction coil of an induction vacuum melting furnace, vacuum is drawn to 2x10 -3 Pa, Ar is introduced as a protective gas, a speed regulation motor is started, and the alloy ingot is prepared into a strip under the action of the induction heating device and the vacuum rapid solidification tape casting device after the copper roller reaches a rotating speed of 1500 rpm, the width of the strip is 2-3 mm, and the thickness is 30-50 μm;
[0032] (4) The above alloy strip is placed in a 6M NaOH solution for chemical dealloying, the sample is taken out after 24 hours, the impurities are washed away, the cleaned sample is collected and vacuum dried at a certain temperature to obtain a nano-porous NiBi alloy catalyst material, such asFigure 1 It can be seen under scanning electron microscope that the NiBi alloy catalyst of the present embodiment has a three-dimensional continuous porous structure, as shown in Figure 2 The X-ray diffraction analysis spectrum of the present embodiment is shown in Figure 3 It can be seen from the figure that the NiBi alloy is composed of Ni and NiBi phases;
[0033] (5) 5 mg of the above catalyst material is dispersed in a liquid mixed with 40 μL of Nafion film solution, 320 μL of ultrapure water and 640 μL of anhydrous ethanol, and ultrasonic treatment is performed for 1 h to obtain an ink-like liquid. 40 μL of the ink-like liquid is uniformly coated on a 1*1.5 cm carbon paper, and the coating area is 1 cm 2 The carbon paper coated with the nano-porous NiBi alloy catalyst is used as the working electrode; Ag / AgCl is used as the reference electrode; a platinum sheet electrode is used as the counter electrode; and 0.1 M Na2SO4 solution is used as the electrolyte. Under the condition of nitrogen gas being introduced, the nitrogen gas synthesis ammonia reaction is carried out, the potential is set to -0.2 to -0.6 V vs. RHE, and the ammonia production rate and Faraday efficiency are shown in Figure 4
[0034] Example 2:
[0035] (1) First, the Al particles with a purity of 99.99%, the Ni particles with a purity of 99.99% and the Bi particles with a purity of 99.99% are cleaned with dilute HCl to remove the surface oxides;
[0036] (2) According to the atomic percentage of Al:Ni:Bi being 90:9:1, 7.67 g of high-purity Al particles, 1.67 g of high-purity Ni particles and 0.66 g of high-purity Bi particles are weighed. The weighed metal particles are uniformly mixed and placed in the heating coil of an induction vacuum melting furnace. A mechanical pump and a vacuum pump are used to vacuumize to 2*10 -3 Pa, Ar is introduced as a protective gas, and the alloy ingot with uniform composition is obtained after repeated melting for 3-5 times under high temperature conditions. After cooling, the alloy ingot is taken out;
[0037] (3) The above alloy ingot is placed in the induction coil of an induction vacuum melting furnace, vacuumized to 2*10 -3 Pa, Ar is introduced as a protective gas, and the speed regulation motor is started. After the copper roller reaches a speed of 1500 rpm, the alloy ingot is prepared into a strip under the action of the induction heating device and the vacuum rapid solidification tape casting device, with a width of 2-3 mm and a thickness of 30-50 μm;
[0038] (4) The above alloy strip is placed in a 6 M NaOH solution for chemical dealloying. After 24 hours, the sample is taken out, the impurities are washed away, the cleaned sample is collected, and vacuum drying is performed at a certain temperature to obtain a nano-porous NiBi alloy catalyst material, as shown inFigure 5 It can be seen under scanning electron microscope that the NiBi alloy catalyst of the present embodiment has a three-dimensional continuous porous structure, as shown in Figure 6 The X-ray diffraction analysis spectrum of the present embodiment is shown in Figure 7 It can be seen from the figure that the NiBi alloy is composed of Ni and NiBi phases;
[0039] (5) 5 mg of the above catalyst material was dispersed in a liquid mixed with 40 μL of Nafion film solution, 320 μL of ultrapure water and 640 μL of anhydrous ethanol, and ultrasonically treated for 1 h to obtain an ink-like liquid. 40 μL of the ink-like liquid was uniformly coated on a 1*1.5 cm carbon paper, and the coating area was 1 cm 2 The carbon paper coated with the nanoporous NiBi alloy catalyst was used as the working electrode; Ag / AgCl was used as the reference electrode; a platinum sheet electrode was used as the counter electrode; and 0.1 M Na2SO4 solution was used as the electrolyte. Under the condition of nitrogen gas being introduced, the nitrogen gas synthesis ammonia reaction was carried out, and the potential was set to -0.2 to -0.6 V vs. RHE. The ammonia production rate and Faraday efficiency are shown in Figure 8
[0040] Example 3:
[0041] (1) First, the Al particles with a purity of 99.99%, the Ni particles with a purity of 99.99% and the Bi particles with a purity of 99.99% were cleaned with dilute HCl to remove the surface oxides;
[0042] (2) According to the atomic percentage of Al:Ni:Bi being 90:9.15:0.85, 7.32 g of high-purity Al particles, 1.41 g of high-purity Ni particles and 1.26 g of high-purity Bi particles were weighed. The weighed metal particles were mixed uniformly and placed in the heating coil of an induction vacuum melting furnace. A mechanical pump and a vacuum pump were used to vacuumize to 2*10 -3 Pa, Ar was introduced as a protective gas, and the alloy ingot with uniform composition was obtained after repeated melting for 3-5 times at high temperature. After cooling, the alloy ingot was taken out;
[0043] (3) The above alloy ingot was placed in the induction coil of an induction vacuum melting furnace, vacuumized to 2*10 -3 Pa, Ar was introduced as a protective gas, and the speed motor was started. After the copper roller reached a speed of 1500 rpm, the alloy ingot was prepared into a strip under the action of the induction heating device and the vacuum rapid solidification tape casting device, with a width of 2-3 mm and a thickness of 30-50 μm;
[0044] (4) The alloy strip is put into a 6M NaOH solution for chemical dealloying, and the sample is taken out after 24 hours, and the impurities are washed away, and the cleaned sample is collected and vacuum dried at a certain temperature to obtain a nano-porous NiBi alloy catalyst material, as shown in FIG. 2. Under a scanning electron microscope, it can be seen that the NiBi alloy catalyst of the embodiment has a three-dimensional continuous porous structure, as shown in FIG. 3. The X-ray diffraction analysis spectrum of the embodiment is shown in FIG. 4. It can be seen from the figure that the NiBi alloy is composed of Ni and NiBi phases. Figure 9 Figure 10 Figure 11
[0045] (5) 5mg of the above-mentioned catalyst material is dispersed in a liquid mixed with 40μL of a Nafion film solution, 320μL of ultrapure water and 640μL of anhydrous ethanol, and ultrasonic treatment is performed for 1h to obtain an ink-like liquid, and 40μL of the liquid is uniformly coated on a 1*1.5cm carbon paper, and the coating area is 1cm 2 . The carbon paper coated with the nano-porous NiBi alloy catalyst is used as the working electrode; Ag / AgCl is used as the reference electrode; a platinum sheet electrode is used as the counter electrode; and a 0.1M Na2SO4 solution is used as the electrolyte, and under the condition of nitrogen gas, the nitrogen synthesis ammonia reaction is carried out, and the potential is set to-0.2-0.6V vs. RHE, and the ammonia production rate and Faraday efficiency are shown in FIG. 5. Figure 12
[0046] The above-mentioned examples are only several specific embodiments of the present application, but are not limited thereto. It should be noted that for those skilled in the art, without departing from the technical concept of the present application, some improvements and modifications can be made to the present application, and these all belong to the protection scope of the present application.
Claims
1. A method for preparing a nanoporous NiBi alloy catalyst for nitrogen reduction, characterized by, The catalyst preparation method is as follows: (1) first, the surfaces of Al particles with a purity of 99.99%, Ni particles with a purity of 99.99%, and Bi particles with a purity of 99.99% are cleaned with dilute HCl; (2) according to the atomic percentage of Al: Ni: Bi being 90: 8: 2-90: 9.5: 0.5, the metal particles are weighed, mixed uniformly, and then placed in the heating coil of an induction vacuum melting furnace, vacuumized to a certain degree by a mechanical pump and a vacuum pump, and Ar is introduced as a protective gas, and the alloy ingot with uniform composition is obtained by repeatedly melting 3-5 times under high temperature conditions, and then taken out after cooling; (3) the alloy ingot in step (2) is placed in an induction vacuum melting furnace, vacuumized to a certain degree, Ar is introduced as a protective gas, and a speed regulation motor is started, and after the copper roller speed reaches the preset value, the alloy ingot is prepared into a strip under the action of an induction heating device and a vacuum rapid solidification tape casting device, with a width of 2-3 mm and a thickness of 30-50 μm; (4) the alloy strip in step (3) is placed in a NaOH solution with a concentration of 3-6 M for chemical dealloying, the sample is taken out after 12-48 h, and the impurities are washed away, the cleaned sample is collected and vacuum dried at a certain temperature to obtain a nano-porous NiBi alloy catalyst material.
2. The method of claim 1, wherein the method is characterized by: The vacuum pressure is 1 x 10 -3 ~ 4 x 10 -3 Pa.
3. The method of claim 1, wherein the method is characterized by: The copper roller speed preset value is 2000-3500 rpm.
4. The use of the catalyst prepared by the nano-porous NiBi alloy catalyst preparation method of any one of claims 1-3 as a cathode catalyst for the electrocatalytic nitrogen gas synthesis ammonia reaction.
5. The use of the catalyst prepared by the method of claim 4 as a cathode catalyst for the electrocatalytic synthesis of ammonia from nitrogen. The electrochemical workstation is used to test under a three-electrode system, with carbon paper coated with a nano-porous NiBi alloy catalyst as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode; 0.1M Na2SO4 solution is used as the electrolyte, and the nitrogen gas synthesis ammonia reaction is carried out under the condition of nitrogen gas being introduced, and the potential setting range is-0.1- -0.9V vs. RHE.