L10-FePt nanoparticle catalyst and magnetic field assisted preparation method and application thereof

Abstract

The invention discloses an L10-FePt nanoparticle catalyst as well as a magnetic field assisted preparation method and application thereof, and belongs to the technical field of nano catalyst preparation and nanoparticle ordered structure regulation and control. The magnetic field assisted preparation method of the catalyst comprises the following steps: step 1, dipping a Pt salt precursor, a Fe salt precursor and a doped element M salt precursor in amorphous carbon black for annealing treatment, and synthesizing fcc-FePt / C or fcc-FePtM / C nanoparticles by a one-step method, M being a doped small atomic radius element; and 2, carrying out annealing treatment on the fcc-FePt / C or fcc-FePtM / C nano particles under the assistance of a magnetic field, so as to obtain the L10-FePt nano particle catalyst. The catalyst disclosed by the invention is simple in synthesis process (assisted by a magnetic field), small in nanoparticle size, capable of being directly loaded on carbon black, high in repeatability, good in particle growth controllability and easy to realize industrialization, and the catalytic performance and the stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of nanocatalyst preparation and ordered structure regulation technology of nanoparticles, specifically relating to an L10-FePt nanoparticle catalyst and its magnetic field-assisted preparation method and application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are a novel energy conversion device that converts chemical energy into electrical energy by oxidizing fuels such as hydrogen and methanol at the anode and reducing oxygen at the cathode. Due to their advantages such as zero emissions and low operating temperatures, they hold promise as a new energy conversion device to address the depletion of fossil fuels and environmental pollution. However, the oxidation reaction at the anode and the reduction reaction at the cathode in PEMFCs are relatively slow, requiring the use of catalysts to improve their reaction rates. In the periodic table, metallic phosphorus (Pt) is widely considered the most effective elemental electrocatalyst, and Pt / C catalysts are currently the most commonly used commercial catalysts. However, Pt resources are scarce and expensive. Furthermore, the electrolyte environment in which the catalyst operates is typically harsh, involving strong acids / bases, water, oxygen, and high potentials. This can easily lead to Pt corrosion, agglomeration, and decreased adhesion to the carbon support, thus affecting the operational stability of the Pt / C catalyst and impacting the output efficiency and lifespan of the fuel cell. Therefore, reducing the amount of Pt used, improving the corrosion resistance of the catalyst, and enhancing its reactivity are key research areas.

[0003] Compared to disordered Pt alloys, chemically ordered Pt alloys (also known as Pt intermetallic compounds) possess high alloying properties, uniform elemental distribution, and specific electronic structures, exhibiting higher catalytic activity and durability in electrocatalytic reactions such as ORR, HER, and MOR. Among the ordered structures of Pt-based alloys, L10-FePt nanomaterials have unique advantages: First, FePt alloying reduces the amount of noble metal Pt required; second, L10-FePt nanomaterials possess high magnetocrystalline anisotropy constants and high coercivity, allowing for catalyst recovery through magnetic separation and enabling Pt reuse; third, the addition of the transition metal Fe causes Pt lattice contraction, shortens Pt-Pt bonds, and alters the coordination number and electronic structure of Pt atoms, facilitating the desorption of Pt from intermediate products and significantly improving catalytic activity. Furthermore, the orbital hybridization between Fe 3d and Pt 5d enhances the interaction between Fe and Pt atoms, thereby greatly improving catalyst stability. Therefore, the synthesis of L10-FePt nanomaterial catalysts is expected to obtain nanoparticle catalysts with high catalytic performance, good stability, and recyclability.

[0004] Obtaining highly ordered, well-dispersed, and small-sized L10-FePt nanoparticles is crucial. The polyol reduction method, i.e., wet chemical synthesis, is currently the most commonly used synthetic approach. However, this method typically yields fcc-FePt structures, requiring high-temperature annealing above 550℃ to achieve ordered transformation. But high-temperature annealing easily leads to particle aggregation and growth. Therefore, researchers add isolating media such as SiO2, MgO, NaCl, and carbon black before annealing fcc-FePt nanoparticles. However, removing the coating layer is complex and prone to incomplete ordered transformation. Other researchers have added large-atomic-radius elements such as Ag, Bi, Au, and Pb to improve the orderliness of FePt nanoparticles during wet chemical synthesis. However, the synthesized particles are relatively large, while doping with small-atomic-radius elements such as Mn and Cu results in lower particle orderliness. Furthermore, FePt nanoparticles synthesized directly through wet chemical synthesis often have organic matter on their surface that is difficult to separate, leading to poor catalytic performance.

[0005] How to obtain small-sized, well-dispersed, highly ordered, and catalytically effective FePt nanoparticle catalysts through simple preparation processes remains a bottleneck problem in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to propose a method for optimizing the ordered structure and catalytic performance of FePt nanoparticles. Through a simple preparation process, a FePt nanoparticle catalyst with small size, good dispersion, high order and good catalytic performance can be obtained.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts, comprising the following steps:

[0009] Step 1: Synthesize fcc-FePt / C or fcc-FePtM / C nanoparticles in one step, where M is a doped element with a small atomic radius;

[0010] Step 2: Under magnetic field assistance, the fcc-FePt / C or fcc-FePtM / C nanoparticles are annealed to obtain L10-FePt nanoparticle catalysts.

[0011] Further, in step 1, the one-step synthesis involves placing Pt salt and Fe salt precursors in a volatile solvent. The Pt salt precursor is H2PtCl6·6H2O, and the Fe salt precursor is FeCl3 or FeCl3·6H2O. The dopant element M salt precursor is selectively added, followed by the addition and uniform dispersion of amorphous carbon black. The solvent is then stirred and evaporated. Subsequently, the mixture is annealed under a reducing / inert gas mixed atmosphere and cooled to room temperature in the furnace.

[0012] Furthermore, the volatile solvent is anhydrous ethanol, water, or n-hexane solution;

[0013] The precursor of M salt is one of MnCl2, CuCl2, ZnCl2, CoCl2, and NiCl2.

[0014] Furthermore, the molar ratio of Pt salt precursor, Fe salt precursor and M salt precursor is 1:(0.82-1.86):(0-1);

[0015] The mass ratio of carbon black to the mixture of H2PtCl6 and FeCl3 is (0.8-2.0):1.

[0016] Furthermore, the temperature for stirring and evaporating is 60℃-100℃;

[0017] The mixed atmosphere for annealing is H2 / Ar, the heating rate is 5℃ / min-10℃ / min, the annealing temperature is 300℃-500℃, and the time is 2h-6h.

[0018] Preferably, in the H2 / Ar mixture, the volume percentage of H2 is 5%-8%.

[0019] Furthermore, the magnetic field strength in step 2 is 0.1T-6T.

[0020] Furthermore, in step 2, the annealing temperature is 550℃-1100℃, and the time is 1h-3h.

[0021] Secondly, the present invention provides an L10-FePt nanoparticle catalyst, which is prepared by the magnetic field-assisted preparation method of the above-mentioned L10-FePt nanoparticle catalyst.

[0022] Furthermore, the L10-FePt nanoparticle catalyst contains L10-FePt nanoparticles with a particle size of 2.9 nm-16.1 nm, uniformly loaded on the carbon black surface; the degree of order is ≥0.89, and the MOR mass activity is ≥1284 mA / mg. Pt .

[0023] Thirdly, the present invention provides an application of L10-FePt nanoparticle catalyst in proton exchange membrane fuel cells.

[0024] Advantages and effects of the present invention:

[0025] 1. The one-step synthesis method of highly ordered FePt / C nanoparticles of the present invention has a simple synthesis process, small nanoparticle size, can be directly loaded onto carbon black, and has high repeatability, good controllability of particle growth, and is easy to industrialize.

[0026] 2. The preparation method of this invention introduces magnetic field assistance, which can achieve the regulation of order by simply controlling the magnetic field strength and temperature, thereby improving the order and overall magnetic properties, and thus enhancing the catalytic performance and stability.

[0027] 3. The present invention also provides FePt / C nanoparticle catalysts with different degrees of lattice distortion by controlling the type of doping of the third element.

[0028] 4. This invention achieves uniform loading of L10-FePt nanoparticles on the surface of carbon black, saving steps for subsequent catalytic performance testing.

[0029] 5. This invention provides new research ideas for the structural regulation of magnetic nanoparticles and the preparation of nanoparticle catalysts. Attached Figure Description

[0030] Figure 1 This is a transmission electron microscope (TEM) image of the L10-FePt nanoparticles synthesized in Example 1 of the present invention.

[0031] Figure 2 This is a high-resolution transmission electron microscope (HRTEM) image of the L10-FePt nanoparticles synthesized in Example 1 of the present invention.

[0032] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the L10-FePt nanoparticles synthesized in Example 1 of this invention.

[0033] Figure 4 The image shows the room-temperature hysteresis loop of the L10-FePt nanoparticles synthesized in Example 1 of this invention.

[0034] Figure 5 This is a MOR activity curve of the L10-FePt nanoparticles synthesized in Example 1 of the present invention;

[0035] Figure 6 This is a transmission electron microscope (TEM) image of the L10-FePt nanoparticles synthesized in Example 2 of the present invention;

[0036] Figure 7 The image shows the X-ray diffraction (XRD) pattern of the L10-FePt nanoparticles synthesized in Example 2 of this invention.

[0037] Figure 8 The image shows the room-temperature hysteresis loop of the L10-FePt nanoparticles synthesized in Example 2 of this invention.

[0038] Figure 9 This is a MOR activity curve of the L10-FePt nanoparticles synthesized in Example 2 of the present invention;

[0039] Figure 10 This is a transmission electron microscope (TEM) image of the L10-FePt nanoparticles synthesized in Example 3 of the present invention;

[0040] Figure 11 The image shows the X-ray diffraction (XRD) pattern of the L10-FePt nanoparticles synthesized in Example 3 of this invention.

[0041] Figure 12 This is a MOR activity curve of the L10-FePt nanoparticles synthesized in Example 3 of the present invention;

[0042] Figure 13 The image shows the X-ray diffraction (XRD) pattern of the L10-FePt nanoparticles synthesized in Example 4 of this invention.

[0043] Figure 14 This is a transmission electron microscope (TEM) image of the L10-FePt nanoparticles synthesized in Example 5 of the present invention.

[0044] Figure 15 The image shows the X-ray diffraction (XRD) pattern of the L10-FePt nanoparticles synthesized in Example 5 of this invention.

[0045] Figure 16 This is a MOR activity curve of the L10-FePt nanoparticles synthesized in Example 5 of the present invention;

[0046] Figure 17 This is a transmission electron microscope (TEM) image of the L10-FePt nanoparticles synthesized in Example 8 of the present invention.

[0047] Figure 18 The image shows the X-ray diffraction (XRD) pattern of the L10-FePt nanoparticles synthesized in Comparative Example 1 of this invention.

[0048] Figure 19 This is a transmission electron microscope (TEM) image of the L10-FePt nanoparticles synthesized in Comparative Example 2 of this invention. Detailed Implementation

[0049] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0050] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0051] Step 1: Place the Pt salt precursor H₂PtCl₆·6H₂O and the Fe salt precursor FeCl₃ or FeCl₃·6H₂O in a volatile solvent such as anhydrous ethanol, water, or n-hexane. Selectively add the dopant element M salt precursor MnCl₂, CuCl₂, ZnCl₂, CoCl₂, or NiCl₂. Then add amorphous carbon black and ultrasonically disperse it evenly. The mass ratio of carbon black to (H₂PtCl₆+FeCl₃) is (0.8-2.0):1. The molar ratio of the bulk and the M salt precursor was 1:(0.82-1.86):(1-0). The solvent was evaporated by stirring at 60℃-100℃ in a magnetic stirrer. The mixture was then placed in a tube furnace and heated to 300℃-500℃ at a heating rate of 5℃ / min-10℃ / min in an H2 / Ar mixed atmosphere (H2: 5vol%-8vol%). The mixture was annealed for 2h-6h to obtain fcc-FePt / C or fcc-FePtM / C nanoparticles, which were then cooled to room temperature in the furnace.

[0052] Step 2: Anneal fcc-FePt / C or fcc-FePtM / C nanoparticles for 1-3 hours at 550℃-1100℃ with the assistance of a 0.1T-6T magnetic field to achieve the disorder-to-order transformation of fcc-FePt / C or fcc-FePtM / C nanoparticles and obtain L10-FePt nanoparticle catalyst.

[0053] An L10-FePt nanoparticle catalyst was prepared using the magnetic field-assisted preparation method described above. The L10-FePt nanoparticles had a particle size of 4 nm-9 nm and were uniformly loaded on the surface of carbon black. The degree of order was ≥0.89, and the MOR mass activity was ≥1284 mA / mg. Pt .

[0054] Example 1

[0055] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0056] Step 1: Take H2PtCl6·6H2O, FeCl3 and MnCl2 in a molar ratio of 1:1:0.2 and place them in anhydrous ethanol solution. Then add amorphous carbon black and ultrasonically disperse it evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1.15:1. Stir and evaporate the solvent at 80°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 300°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:5vol%). Anneal for 2 hours to obtain fcc-FePtMn / C nanoparticles. Cool to room temperature with the furnace.

[0057] Step 2: Anneal the fcc-FePtMn / C nanoparticles for 1 h at a magnetic field of 6T and a temperature of 700℃ to achieve the disorder-order transformation of the fcc-FePtMn / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0058] The L10-FePt nanoparticle catalyst prepared in Example 1 has an average particle size of 7.9 nm, is uniformly loaded on the carbon black surface, has an order degree of 0.95, and a MOR mass activity of 2292 mA / mg. Pt .

[0059] Performance testing:

[0060] TEM morphology testing: such as Figure 1 The TEM morphology of the L10-FePt nanoparticles in Example 1 is shown, where the light-colored particles are carbon black and the dark-colored small particles are FePt. The particles are well dispersed on the carbon black. TEM analysis of over 100 particles showed a minimum particle size of 4 nm, a maximum particle size of 9 nm, and an average particle size of 7.9 nm. Figure 2 As shown, the interplanar spacing of the L10-FePt nanoparticles in Example 1 was measured using a high-resolution TEM image, which corresponds to the L10-FePt-(111) plane.

[0061] Orderliness Test: The orderliness of the crystal structure of the L10-FePt nanoparticles in Example 1 was tested by XRD, such as... Figure 3 As shown, the synthesized nanoparticles are pure-phase L10-FePt, and the degree of order is calculated to be 0.95.

[0062] The degree of order in the magnetic structure of the L10-FePt nanoparticles in Example 1 was tested using hysteresis loops. Figure 4 As shown, its coercivity is as high as 12.1 kOe, which is consistent with the L10-FePt in the XRD diagram.

[0063] Activity assay: The activity of MOR is tested by cyclic voltammetry (CV), such as... Figure 5As shown, the mass activity of MOR is 2292 mA / mg. Pt .

[0064] Example 2

[0065] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0066] Step 1: Take H2PtCl6·6H2O, FeCl3 and MnCl2 in a molar ratio of 1:1:0.2 and place them in anhydrous ethanol solution. Then add amorphous carbon black and ultrasonically disperse it evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1.15:1. Stir and evaporate the solvent at 100°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 300°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:5vol%). Anneal for 2 hours to obtain fcc-FePtMn / C nanoparticles. Cool to room temperature with the furnace.

[0067] Step 2: Anneal the fcc-FePtMn / C nanoparticles for 1 h at a magnetic field of 6T and a temperature of 600℃ to achieve the disorder-order transformation of the fcc-FePtMn / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0068] The L10-FePt nanoparticle catalyst prepared in Example 2 was uniformly loaded on the carbon black surface, with an order degree of 0.89 and a MOR mass activity of 1284 mA / mg. Pt .

[0069] Performance testing:

[0070] TEM morphology testing: such as Figure 6 The TEM morphology of L10-FePt nanoparticles in Example 2 is shown. The light-colored particles are carbon black, and the dark-colored small particles are FePt. The particles are well dispersed on the carbon black. The particle size of more than 100 particles was statistically analyzed by TEM. The minimum particle size is 2.9 nm, the maximum particle size is 11.6 nm, and the average particle size is 6.9 nm.

[0071] Orderliness Test: The orderliness of the crystal structure of the L10-FePt nanoparticles in Example 2 was tested by XRD, such as... Figure 7 As shown, the synthesized nanoparticles are pure-phase L10-FePt, and the degree of order is calculated to be 0.89.

[0072] The degree of order in the magnetic structure of the L10-FePt nanoparticles in Example 2 was tested using hysteresis loops. Figure 8 As shown, its coercivity is as high as 9.55 kOe, which is consistent with the L10-FePt in the XRD diagram.

[0073] Activity assay: The activity of MOR is tested by cyclic voltammetry (CV), such as... Figure 9 As shown, the mass activity of MOR is 1284 mA / mg. Pt .

[0074] Example 3

[0075] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0076] Step 1: Take H2PtCl6·6H2O and FeCl3 in a molar ratio of 1:1, place them in anhydrous ethanol solution, and then add amorphous carbon black and ultrasonically disperse them evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1.15:1. Stir and evaporate the solvent at 80°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 300°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:5 vol%). Anneal for 2 hours to obtain fcc-FePt / C nanoparticles, and cool them to room temperature with the furnace.

[0077] Step 2: Anneal the fcc-FePt / C nanoparticles for 1 hour under a 6T magnetic field and 700℃ to achieve the disorder-order transformation of the fcc-FePt / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0078] The L10-FePt nanoparticle catalyst prepared in Example 3 was uniformly loaded on the carbon black surface, with an order degree of 0.93 and a MOR mass activity of 1476 mA / mg. Pt .

[0079] Performance testing:

[0080] TEM morphology testing: such as Figure 10 The TEM morphology of L10-FePt nanoparticles in Example 3 is shown. The light-colored particles are carbon black, and the dark-colored small particles are FePt. The particles are well dispersed on the carbon black. The particle size of more than 100 particles was statistically analyzed by TEM. The minimum particle size is 3.2 nm, the maximum particle size is 16.1 nm, and the average particle size is 7.3 nm.

[0081] Orderliness test: The orderliness of the crystal structure of the L10-FePt nanoparticles in Example 3 was tested by XRD, such as... Figure 11 As shown, the synthesized nanoparticles are pure-phase L10-FePt, and the degree of order is calculated to be 0.93.

[0082] Activity assay: The activity of MOR is tested by cyclic voltammetry (CV), such as... Figure 12As shown, the mass activity of MOR is 1476 mA / mg. Pt .

[0083] Example 4

[0084] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0085] Step 1: Take H2PtCl6·6H2O, FeCl3 and MnCl2 in a molar ratio of 1:1:0.2 and place them in anhydrous ethanol solution. Then add amorphous carbon black and ultrasonically disperse it evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1.15:1. Stir and evaporate the solvent at 100°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 300°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:5vol%). Anneal for 2 hours to obtain fcc-FePtMn / C nanoparticles. Cool to room temperature with the furnace.

[0086] Step 2: Anneal the fcc-FePtMn / C nanoparticles for 1 hour at a magnetic field of 4T and a temperature of 700℃ to achieve the disorder-order transformation of the fcc-FePtMn / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0087] The L10-FePt nanoparticle catalyst prepared in Example 4 was uniformly loaded onto the carbon black surface. The degree of order of the crystal structure of the L10-FePt nanoparticles was tested by XRD. Figure 13 As shown, the synthesized nanoparticles are pure-phase L10-FePt, and the degree of order is calculated to be 0.94.

[0088] Example 5

[0089] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0090] Step 1: Take H2PtCl6·6H2O, FeCl3 and MnCl2 in a molar ratio of 1:1:0.2 and place them in anhydrous ethanol solution. Then add amorphous carbon black and ultrasonically disperse it evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1.15:1. Stir and evaporate the solvent at 60°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 300°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:5 vol%). Anneal for 2 h to obtain fcc-FePtMn / C nanoparticles. Cool to room temperature with the furnace.

[0091] Step 2: Anneal the fcc-FePtMn / C nanoparticles for 1 h at a magnetic field of 2T and a temperature of 700℃ to achieve the disorder-order transformation of the fcc-FePtMn / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0092] The L10-FePt nanoparticle catalyst prepared in Example 5 was uniformly loaded on the carbon black surface, with an order degree of 0.93 and a MOR mass activity of 1995 mA / mg. Pt .

[0093] Performance testing:

[0094] TEM morphology testing: such as Figure 14 The TEM morphology of L10-FePt nanoparticles in Example 5 is shown. The light-colored particles are carbon black, and the dark-colored small particles are FePt. The particles are well dispersed on the carbon black. The particle size of more than 100 particles was statistically analyzed by TEM. The minimum particle size is 3.6 nm, the maximum particle size is 9.4 nm, and the average particle size is 7.5 nm.

[0095] Orderliness Test: The orderliness of the crystal structure of the L10-FePt nanoparticles in Example 1 was tested by XRD, such as... Figure 15 As shown, the synthesized nanoparticles are pure-phase L10-FePt, and the degree of order is calculated to be 0.93.

[0096] Activity assay: The activity of MOR is tested by cyclic voltammetry (CV), such as... Figure 16 As shown, the mass activity of MOR is 1995 mA / mg. Pt .

[0097] Example 6

[0098] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0099] Step 1: Take H2PtCl6·6H2O, FeCl3 and MnCl2 in a molar ratio of 1:1:0.2 and place them in a hexane solution. Then add amorphous carbon black and disperse it evenly by ultrasonication. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1.15:1. Stir and evaporate the solvent at 60°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 400°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:5 vol%). Anneal for 3 h to obtain fcc-FePtMn / C nanoparticles. Cool to room temperature with the furnace.

[0100] Step 2: Anneal the fcc-FePtMn / C nanoparticles for 3 hours under a 6T magnetic field and 700℃ to achieve the disorder-to-order transformation of the fcc-FePtMn / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0101] Example 7

[0102] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0103] Step 1: Take H2PtCl6·6H2O and FeCl3·6H2O with a molar ratio of 1:1, place them in water, and then add amorphous carbon black and ultrasonically disperse them evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 0.8:1. Stir and evaporate the solvent at 100°C in a magnetic stirrer. Then, put the mixture into a tube furnace and heat it to 500°C at a heating rate of 6°C / min under an H2 / Ar mixed atmosphere (H2:5 vol%). Anneal for 3 h to obtain fcc-FePt / C nanoparticles. Cool to room temperature with the furnace.

[0104] Step 2: Anneal the fcc-FePt / C nanoparticles for 2 hours under a 6T magnetic field and 700℃ to achieve the disorder-to-order transformation of the fcc-FePt / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0105] Example 8

[0106] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0107] Step 1: Take H2PtCl6·6H2O and FeCl3·6H2O with a molar ratio of 1:1, place them in water, and then add amorphous carbon black and ultrasonically disperse them evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 2:1. Stir and evaporate the solvent at 100°C in a magnetic stirrer. Then, put the mixture into a tube furnace and heat it to 500°C at a heating rate of 5°C / min under an H2 / Ar mixed atmosphere (H2:5 vol%). Anneal for 6 h to obtain fcc-FePt / C nanoparticles. Cool to room temperature with the furnace.

[0108] Step 2: Anneal the fcc-FePt / C nanoparticles for 2 hours under a 6T magnetic field and 700℃ to achieve the disorder-to-order transformation of the fcc-FePt / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0109] like Figure 17 As shown, the L10-FePt nanoparticle catalyst prepared in Example 8 is uniformly loaded on the carbon black surface.

[0110] Example 9

[0111] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0112] Step 1: Take H2PtCl6·6H2O, FeCl3 and M salt in a molar ratio of 1:1:1, place them in an aqueous solution, and then add amorphous carbon black and ultrasonically disperse them evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1:1. Stir and evaporate the solvent at 100°C in a magnetic stirrer. Then place the mixture in a tube furnace and heat it to 400°C at a heating rate of 10°C / min under a H2 / Ar mixed atmosphere (H2:8 vol%). Anneal for 3 h to obtain fcc-FePtM / C nanoparticles. Cool to room temperature with the furnace.

[0113] Step 2: Anneal the fcc-FePtM / C nanoparticles for 3 hours at a magnetic field of 0.1T and a temperature of 550℃ to achieve the disorder-order transformation of the fcc-FePtM / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0114] Example 10

[0115] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0116] Step 1: Take H2PtCl6·6H2O, FeCl3 and M salt in a molar ratio of 1:0.82:1, M salt is a mixture of CuCl2, ZnCl2, CoCl2 and NiCl2, place them in an aqueous solution, and then add amorphous carbon black and ultrasonically disperse them evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1:1. Stir and evaporate the solvent at 100℃ in a magnetic stirrer. Then put the mixture into a tube furnace and heat it to 400℃ at a heating rate of 10℃ / min under a H2 / Ar mixed atmosphere (H2:8vol%). Anneal for 3h to obtain fcc-FePtM / C nanoparticles. Cool to room temperature with the furnace.

[0117] Step 2: Anneal the fcc-FePtM / C nanoparticles for 1 h at a magnetic field of 1 T and a temperature of 900 °C to achieve the disorder-order transformation of the fcc-FePtM / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0118] Example 11

[0119] A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts includes the following steps:

[0120] Step 1: Take H2PtCl6·6H2O and FeCl3 in a molar ratio of 1:1.86, place them in water, and then add amorphous carbon black and ultrasonically disperse them evenly. The mass ratio of carbon black to (H2PtCl6+FeCl3) is 1:1. Stir and evaporate the solvent at 100°C in a magnetic stirrer. Then, put the mixture into a tube furnace and heat it to 300°C at a heating rate of 10°C / min under an H2 / Ar mixed atmosphere (H2:5 vol%). Anneal for 6 h to obtain fcc-FePt / C nanoparticles. Cool to room temperature with the furnace.

[0121] Step 2: Anneal the fcc-FePt / C nanoparticles for 1 hour at a magnetic field of 1T and a temperature of 1100℃ to achieve the disorder-order transformation of the fcc-FePt / C nanoparticles and obtain the L10-FePt nanoparticle catalyst.

[0122] Comparative Example 1

[0123] A method for preparing FePt nanoparticles, differing from Example 1, involves annealing under a magnetic field with a magnetic field strength of 0 T and a reaction temperature of 500℃. The degree of order in the crystal structure of the synthesized particles is tested using XRD. Figure 18 As shown, the degree of order was calculated, and the degree of order of the synthesized particles was only 0.56, which is significantly lower than that of Example 1.

[0124] Comparative Example 2

[0125] A magnetic field-assisted preparation method for FePt nanoparticles, differing from Example 1 only in that MnCl2 is replaced with BiCl3. The morphology was analyzed by TEM. Figure 19 As shown, the size of the synthesized particles is significantly larger than that of Example 1, with an average particle size of over 50 nm. This is because the atomic radius of Bi is larger than that of Fe and Pt, thus the size of the synthesized particles is also significantly increased.

Claims

1. A magnetic field-assisted preparation method for L10-FePt nanoparticle catalysts, characterized in that, Includes the following steps: Step 1: Synthesize fcc-FePt / C or fcc-FePtM / C nanoparticles in one step, where M is a doped element with a small atomic radius; Step 2: Under magnetic field assistance, the fcc-FePt / C or fcc-FePtM / C nanoparticles are annealed to obtain L10-FePt nanoparticle catalysts.

2. The magnetic field-assisted preparation method of the L10-FePt nanoparticle catalyst as described in claim 1, characterized in that, In step 1, the one-step synthesis involves placing Pt salt and Fe salt precursors in a volatile solvent. The Pt salt precursor is H2PtCl6·6H2O, and the Fe salt precursor is FeCl3 or FeCl3·6H2O. The dopant element M salt precursor is selectively added, followed by the addition and uniform dispersion of amorphous carbon black. The solvent is then evaporated by stirring, and the mixture is subsequently annealed in a reducing / inert gas mixed atmosphere and cooled to room temperature in the furnace.

3. The magnetic field-assisted preparation method of the L10-FePt nanoparticle catalyst as described in claim 2, characterized in that, The volatile solvent is anhydrous ethanol, water, or n-hexane solution; The precursor of M salt is one of MnCl2, CuCl2, ZnCl2, CoCl2, and NiCl2.

4. The magnetic field-assisted preparation method of the L10-FePt nanoparticle catalyst as described in claim 2, characterized in that, The molar ratio of Pt salt precursor, Fe salt precursor and M salt precursor is 1:(0.82-1.86):(0-1); The mass ratio of carbon black to the mixture of H2PtCl6 and FeCl3 is (0.8-2.0):

1.

5. The magnetic field-assisted preparation method of the L10-FePt nanoparticle catalyst as described in claim 2, characterized in that, The temperature for stirring and evaporating to dryness is 60℃-100℃; The mixed atmosphere for annealing is H2 / Ar, the heating rate is 5℃ / min-10℃ / min, the annealing temperature is 300℃-500℃, and the time is 2h-6h.

6. The magnetic field-assisted preparation method of the L10-FePt nanoparticle catalyst as described in claim 1, characterized in that, In step 2, the magnetic field strength is 0.1T-6T.

7. The magnetic field-assisted preparation method of the L10-FePt nanoparticle catalyst as described in claim 1, characterized in that, In step 2, the annealing temperature is 550℃-1100℃, and the time is 1h-3h.

8. An L10-FePt nanoparticle catalyst, characterized in that, The L10-FePt nanoparticle catalyst was prepared using the magnetic field-assisted preparation method according to any one of claims 1-7.

9. The L10-FePt nanoparticle catalyst as described in claim 8, characterized in that, The L10-FePt nanoparticle catalyst contains L10-FePt nanoparticles with a particle size of 2.9 nm-16.1 nm, uniformly loaded on the carbon black surface; the degree of order is ≥0.89, and the MOR mass activity is ≥1284 mA / mg. Pt .

10. The application of the L10-FePt nanoparticle catalyst according to claim 8 in a proton exchange membrane fuel cell.

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