Preparation method of intermetallic compound nano-catalyst with one-dimensional morphology

Abstract

The invention relates to a preparation method of an intermetallic compound nano catalyst with one-dimensional morphology. The method comprises the following steps: adding a noble metal salt, a non-noble metal salt, a surfactant and a reducing agent into oleylamine to obtain a colloid, and then ultrasonically dispersing the colloid together with a carbon carrier in a mixed solution of cyclohexane and ethanol to obtain a nano catalyst precursor with a one-dimensional morphology and a disordered structure; and quickly heating the precursor, and performing high-temperature annealing in an atmosphere with strong adsorbability to metal atoms to obtain the final intermetallic compound nano-catalyst with one-dimensional morphology. The method does not need processes such as coating and coating removal, and has the advantages of simple method, easiness in batch production and the like.

Description

Technical Field

[0001] The invention belongs to the field of new energy materials and relates to a preparation method and application of an intermetallic compound nanocatalyst with a one-dimensional morphology. Background Art

[0002] Fuel cells have the characteristics of high energy conversion efficiency and low environmental pollution, and are an important way to efficiently utilize hydrogen energy. They are considered to have broad development prospects in power generation and heating stations, portable mobile power supplies, automobiles, aerospace, etc. However, the high cost and low durability of fuel cells have restricted the large-scale commercial development of fuel cells.

[0003] The key reason for the high cost and low durability of fuel cells is the high cost and poor stability of fuel cell cathode catalysts. One of the most effective strategies is to transform alloys with disordered solid solution structures into intermetallic compounds through ordered phase transition. Intermetallic compounds have higher mixing enthalpy, and metal elements are connected by stronger covalent bonds, which are conducive to improving the stability of catalysts. In addition, the one-dimensional structure has more contact sites with the carbon support, so the one-dimensional structure can also improve the stability of the catalyst. At the same time, the one-dimensional structure can increase the transfer rate of electrons and mass, thereby improving the catalytic activity of the catalyst. Therefore, if the advantages of intermetallic compounds and one-dimensional structures can be combined to synthesize intermetallic compounds with one-dimensional morphology, it will provide a promising catalyst for fuel cells. The simplest and most effective preparation method for intermetallic compounds is high-temperature annealing. However, the surface energy of nanomaterials is high, and surface atoms are easily diffused in high-temperature environments. Nanocrystalline catalysts sinter and grow, and the active sites are greatly reduced, and the activity of the catalyst is sharply reduced. Therefore, it is urgent to find a simple, efficient and low-cost method to prepare intermetallic compounds with one-dimensional morphology. To this end, scientists have proposed some strategies. Zhang et al. (Zhang T, et al., Angew. Chem. Int. Ed. 2022, 61, e202113278) used a spatial confinement method to prepare an intermetallic compound nanocatalyst with a one-dimensional morphology. The specific method is to coat the oxide SiO2 on a catalyst with a one-dimensional morphology and then anneal it at high temperature. Although this method successfully prepared an intermetallic compound nanocatalyst with a one-dimensional morphology, the complicated pre- and post-processing increased the experimental difficulty and cost, and there was no good universality, which was not conducive to commercial production. Therefore, it is still a severe challenge to develop a simple, efficient, low-cost, and universal method to prepare an intermetallic compound nanocatalyst with a one-dimensional morphology. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a metal compound nanocatalyst with a one-dimensional morphology in view of the deficiencies of the prior art. The method firstly prepares a nanocatalyst precursor with a one-dimensional morphology and a disordered structure by a solvothermal method, then loads the precursor, and finally prepares the metal compound nanocatalyst with a one-dimensional morphology by a rapid heating and hydrogen-assisted method. The present invention does not require processes such as coating and de-coating, and has the advantages of being simple in method and easy to mass produce.

[0005] The technical solution of the present invention is:

[0006] A method for preparing an intermetallic compound nanocatalyst with a one-dimensional morphology, the method comprising the following steps:

[0007] (1) adding a noble metal salt, a non-noble metal salt, a surfactant and a reducing agent to oleylamine, and then reacting them in an oil bath at 160 to 250° C. for 5 to 12 hours to obtain a colloid;

[0008] The molar ratio of the noble metal salt to the non-noble metal salt is 1 to 3:1; 0.01 to 0.05 mmol of the noble metal salt and 0.003 to 0.017 mmol of the non-noble metal salt are added to every 5 mL of oleylamine, and further 0.1 to 2 mmol of a surfactant and 0.1 to 0.6 mmol of a reducing agent are added;

[0009] (2) washing the colloid, dispersing the colloid and the carbon support in a mixture of cyclohexane and ethanol for 0.5 to 2 hours by ultrasonic, centrifugally separating and drying to obtain a nanocatalyst precursor having a one-dimensional morphology and a disordered structure;

[0010] The loading amount of the noble metal on the carbon carrier is 10-40%;

[0011] (3) rapidly heating the product obtained in step (2) to 500-1000° C. in an atmosphere having strong adsorption for metal atoms for high temperature annealing to obtain a final intermetallic compound nanocatalyst having a one-dimensional morphology;

[0012] The noble metal salt is one or both of Pt salt and Pd salt; the non-noble metal salt is one or more of Fe, Co, Ni, Cu and Zn salt.

[0013] The noble metal salt is platinum acetylacetonate or palladium acetylacetonate;

[0014] The non-noble metal salt is iron acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, copper acetylacetonate or zinc acetylacetonate.

[0015] The sum of the number of precious metal and non-precious metal elements in the nanocatalyst with one-dimensional morphology and disordered structure is 2 to 5.

[0016] The surfactant is one of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide;

[0017] The reducing agent is one of glucose and ascorbic acid;

[0018] The carbon carrier is carbon black or Ketjen black.

[0019] The disordered structure refers to that various metal elements are distributed disorderly in the crystal lattice.

[0020] The atmosphere having strong adsorption capacity for metal atoms is a hydrogen atmosphere or a carbon monoxide atmosphere or a mixed atmosphere of an inert gas (nitrogen or argon) and hydrogen (or carbon monoxide), wherein the volume proportion of hydrogen (or carbon monoxide) in the mixed atmosphere is 1 to 99%.

[0021] The rapid heating refers to a heating rate in the range of 30 to 700° C. / min.

[0022] The annealing holding time is 30 to 1500 minutes.

[0023] The intermetallic compound nanocatalyst with one-dimensional morphology prepared by the method described above is used as a fuel cell electrode catalyst.

[0024] The essential features of the present invention are:

[0025] The current technology for preparing intermetallic compounds with one-dimensional morphology is to coat the oxide SiO2 on a catalyst with one-dimensional morphology and then perform high-temperature annealing; this requires complex pre-treatment and post-treatment processes before and after the heat treatment (pre-treatment refers to coating the oxide coating, and post-treatment refers to removing the oxide coating).

[0026] The present invention adopts a gas-assisted method with rapid heating and strong adsorption of metal atoms to obtain an intermetallic compound nanocatalyst with one-dimensional morphology, without these complicated pre- and post-processing steps, and the diffusion time of the surface atoms of the nanomaterial at high temperature can be reduced by the rapid heating mode, which is conducive to the maintenance of the morphology. In addition, with respect to the hydrogen in the gas with strong adsorption of metal atoms, hydrogen is adsorbed on the surface of the one-dimensional nanowire, and the surface energy of the one-dimensional nanomaterial is reduced due to the interaction between the 1S orbit of hydrogen and the 3d (or 5d) orbit of the surface metal atom, which slows down the migration of the surface atoms of the nanowire, is the key to the one-dimensional nanowire to maintain the morphology, and also alleviates the sintering of the one-dimensional nanomaterial at high temperature. The obtained catalyst material can be applied to fuel cells.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides a method for preparing an intermetallic compound nanocatalyst with a one-dimensional morphology, which inhibits deformation, sintering and growth of the one-dimensional structure at high temperature. The present invention has the advantages of simple method and easy batch production. The prepared intermetallic compound catalyst with a one-dimensional morphology exhibits excellent electrocatalytic performance in an oxygen reduction performance test, and the mass activity is about 5 times that of the current commercial platinum-carbon catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a transmission electron microscope image of the intermetallic compound Pt3Fe nanowires (NWs) with one-dimensional morphology prepared in Example 1 of the present invention.

[0030] Figure 2 A high-resolution image of the intermetallic compound Pt3Fe NWs with a one-dimensional morphology prepared in Example 1 of the present invention and a fast Fourier transform image corresponding to the high-resolution image.

[0031] Figure 3 is an X-ray powder diffraction spectrum of the intermetallic compound Pt3Fe NWs with a one-dimensional morphology prepared in Example 1 of the present invention;

[0032] Figure 4 is a transmission electron microscope image of the intermetallic compound Pt3Co NWs with one-dimensional morphology prepared in Example 2 of the present invention;

[0033] Figure 5 3 is a transmission electron microscope image of the intermetallic compound Pt3Ni3 NWs with one-dimensional morphology prepared in Example 7 of the present invention.

[0034] Figure 6 It is a graph showing the oxygen reduction performance of the intermetallic compound Pt3Fe NWs having a one-dimensional morphology prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the method, steps or conditions of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0036] Example 1

[0037] (1) According to the molar ratio of 3:1, accurately weigh the corresponding mass of Pt(acac)2 and Fe(acac)3, specifically weigh 10.0 mg (0.0254 mmol) of Pt(acac)2 (platinum acetylacetonate), 3.0 mg (0.00857 mmol) of Fe(acac)3 (ferric acetylacetonate), and also weigh 32.0 mg (0.1 mmol) of CTAC (hexadecyltrimethylammonium chloride) and 60.0 mg (0.33 mmol) of glucose. Put all the above drugs in a reaction glass bottle, add 5 mL of OAm (oleylamine), place the reaction glass bottle containing the drugs in an ultrasonic machine for 1 h to mix the solution in the bottle evenly, and place the reaction glass bottle containing the uniform mixed solution in an oil bath. The heating panel was operated to raise the temperature of the oil bath from room temperature to 200°C. The reaction glass bottle was kept in the oil bath for 8 h to obtain 5.0 mg of black colloid, which was Pt3Fe nanowires with disordered structure. Reaction residues such as CTAC and OAm were washed away with cyclohexane and ethanol, and the black colloid was then dispersed in 3 mL of cyclohexane for later use.

[0038] (2) Pt3Fe nanowires were loaded on carbon black (XC-72R). The specific operation was as follows: 5.0 mg of black colloid dispersed in 3 mL of cyclohexane was mixed with 20.0 mg of carbon black dispersed evenly in 10.0 mL of ethanol by ultrasonication, and then ultrasonicated for 1 h. The sample was then centrifuged from the dispersion using a centrifuge, and finally dried to obtain a black powder. (The loading amount of the precious metal on the carbon carrier was 20%, which is a theoretical value)

[0039] (3) The black powder in step (2) is placed in a tube furnace, and the temperature is rapidly raised to 700°C at 700°C / min in a hydrogen-argon mixed gas atmosphere (hydrogen volume ratio is 5%), and then kept warm for 1 hour. After the insulation is completed, the upper cover of the tube furnace is opened to cool the sample to room temperature, and the intermetallic compound Pt3Fe NWs with a one-dimensional morphology can be obtained.

[0040] Example 2

[0041] The type of non-precious metal salt was changed, and the molar ratio was 3:1. The corresponding mass of Pt(acac)2 and Co(acac)2 were accurately weighed, and a Pt3Co NWs precursor with a disordered structure was prepared according to the method of steps (1)-(2) in Example 1;

[0042] The difference between step (3) and Example 1 is that the volume ratio of hydrogen in the hydrogen-argon mixture is 25%, the heating rate is 30°C / min, and the rest is the same as step (3) in Example 1 to prepare intermetallic compound Pt3Co NWs with a one-dimensional morphology.

[0043] Example 3

[0044] The type of non-precious metal salt was changed, and the corresponding mass of Pt(acac)2 and Ni(acac)2 was accurately weighed according to the molar ratio of 3:1. According to the method of steps (1)-(3) in Example 1, the intermetallic compound Pt3NiNWs with a one-dimensional morphology was prepared.

[0045] Example 4

[0046] The type of non-precious metal salt was changed, and the corresponding mass of Pt(acac)2 and Zn(acac)2 was accurately weighed according to the molar ratio of 3:1. According to the method of steps (1)-(3) in Example 1, the intermetallic compound Pt3ZnNWs with a one-dimensional morphology was prepared.

[0047] Example 5

[0048] According to the molar ratio of 1:1 (the amount of fixed precious metal is 0.0254 mmol, and the non-precious metal is weighed according to the molar ratio. The following examples are treated in the same way.), the corresponding masses of Pt(acac)2 and Fe(acac)3 are accurately weighed, and the intermetallic compound Pt3Fe3 NWs with a one-dimensional morphology are prepared according to the method of steps (1)-(3) in Example 1.

[0049] Example 6

[0050] According to the molar ratio of 1:1, the corresponding masses of Pt(acac)2 and Co(acac)2 were accurately weighed, and the intermetallic compound Pt3Co3 NWs with a one-dimensional morphology were prepared according to the method of steps (1) to (3) in Example 1.

[0051] Example 7

[0052] According to the molar ratio of 1:1, accurately weigh the corresponding mass of Pt(acac)2 and Ni(acac)2, and prepare a Pt3Ni3 NWs precursor with a disordered structure according to the method of steps (1)-(2) in Example 1;

[0053] The difference between step (3) and Example 1 is that the annealing temperature is 550° C. and the holding time is 1500 min. The rest is the same as step (3) in Example 1, and intermetallic compound Pt3Ni3 NWs with one-dimensional morphology are prepared.

[0054] Example 8

[0055] According to the molar ratio of 3:2:1, the corresponding masses of Pt(acac)2, Ni(acac)2, and Fe(acac)3 were accurately weighed, and the intermetallic compound Pt3Ni2Fe NWs with a one-dimensional morphology were prepared according to the method of steps (1)-(3) in Example 1.

[0056] Example 9

[0057] According to the molar ratio of 4:1:1:1:1, the corresponding masses of Pt(acac)2, Fe(acac)3, Co(acac)2, Ni(acac)2, and Cu(acac)2 were accurately weighed and the method of steps (1) to (3) in Example 1 was used to prepare the intermetallic compound Pt4Fe1Co1N with a one-dimensional morphology. i Cu1 NWs.

[0058] The transmission electron microscopy image of the intermetallic compound Pt3Fe NWs with one-dimensional morphology prepared in Example 1 is as follows: Figure 1 As shown, it proves that the one-dimensional morphology is maintained after high temperature heat treatment. Figure 2 The high-resolution image of the intermetallic compound Pt3Fe NWs with a one-dimensional morphology prepared in Example 1 and the fast Fourier transform image corresponding to the high-resolution image can prove the ordered structure of the Pt3Fe NWs intermetallic compound (i.e., the atomic order in the crystal structure is fixed). In addition, the X-ray powder diffraction spectrum of the intermetallic compound Pt3Fe NWs with a one-dimensional morphology prepared in Example 1 is as follows: Figure 3 As shown, the appearance of superlattice diffraction peaks can also prove the ordered structure.

[0059] The intermetallic compound Pt3Fe NWs with one-dimensional morphology prepared in Example 1 exhibited excellent oxygen reduction performance. The linear sweep voltammetric curve was tested in an acidic environment of 0.1M HClO4 and a rotation speed of 1600rpm using a rotating disk electrode (RDE test). Figure 6 , demonstrating that intermetallic compound Pt3Fe NWs with one-dimensional morphology is one of the promising catalysts for proton exchange membrane fuel cell cathodes.

[0060] The catalysts prepared in other examples also maintained a one-dimensional morphology and had obvious ordered structural characteristics.

[0061] The transmission images of the intermetallic compound catalysts with one-dimensional morphology prepared in Examples 2 and 7 are as follows: Figure 4 , 5 As shown in the figure, it can be seen that the one-dimensional morphology of both catalysts is well maintained and there is no agglomeration.

[0062] In summary, the present invention obtains a one-dimensional intermetallic compound nanocatalyst by controlling the heating rate and gas composition; the present invention has a simple preparation process, abundant raw materials and high practicality, and the synthesized one-dimensional intermetallic compound nanocatalyst can improve the catalytic performance in the catalytic process. Therefore, this method has a good development prospect and is expected to be applied to mass production in the future.

[0063] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing an intermetallic compound nanocatalyst having a one-dimensional morphology, characterized in that The method comprises the following steps: (1) adding a noble metal salt, a non-noble metal salt, a surfactant and a reducing agent to oleylamine, and then reacting them in an oil bath at 160 to 250° C. for 5 to 12 hours to obtain a colloid; The molar ratio of the noble metal salt to the non-noble metal salt is 1 to 3:1; 0.01 to 0.05 mmol of the noble metal salt, 0.003 to 0.017 mmol of the non-noble metal salt, 0.1 to 2 mmol of the surfactant, and 0.1 to 0.6 mmol of the reducing agent are added to every 5 mL of oleylamine; (2) washing the colloid, dispersing the colloid and the carbon support in a mixture of cyclohexane and ethanol for 0.5 to 2 hours by ultrasonic, centrifugally separating and drying to obtain a nanocatalyst precursor having a one-dimensional morphology and a disordered structure; The loading amount of the noble metal on the carbon carrier is 10-40%; (3) rapidly heating the product obtained in step (2) to 500-1000° C. in an atmosphere having strong adsorption for metal atoms for high temperature annealing to obtain an intermetallic compound nanocatalyst having a one-dimensional morphology; The noble metal salt is one or both of Pt salt and Pd salt; the non-noble metal salt is one or more of Fe, Co, Ni, Cu and Zn salt.

2. The method for preparing a one-dimensional intermetallic compound nanocatalyst according to claim 1, wherein the noble metal salt is platinum acetylacetonate or palladium acetylacetonate; The non-noble metal salt is iron acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, copper acetylacetonate or zinc acetylacetonate.

3. The method for preparing a metal intermetallic compound nanocatalyst with a one-dimensional morphology as claimed in claim 1, characterized in that the sum of the number of precious metal and non-precious metal elements in the nanocatalyst with a one-dimensional morphology and disordered structure is 2 to 5.

4. The method for preparing a metal intermetallic compound nanocatalyst having a one-dimensional morphology according to claim 1, wherein the surfactant is one of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide or octadecyltrimethylammonium bromide; The reducing agent is one of glucose and ascorbic acid; The carbon carrier is carbon black or Ketjen black.

5. The method for preparing a metal intermetallic compound nanocatalyst with a one-dimensional morphology as claimed in claim 1, characterized in that the atmosphere having a strong adsorption capacity for metal atoms is a hydrogen atmosphere or a carbon monoxide atmosphere or a mixed atmosphere of an inert gas (nitrogen or argon) and hydrogen (or carbon monoxide), and the volume proportion of hydrogen (or carbon monoxide) in the mixed atmosphere is 1 to 99%.

6. The method for preparing the intermetallic compound nanocatalyst having a one-dimensional morphology as claimed in claim 1, characterized in that The rapid heating refers to a heating rate in the range of 30 to 700°C / min; The annealing holding time is 30 to 1500 minutes.

7. The method for preparing the intermetallic compound nanocatalyst having a one-dimensional morphology as claimed in claim 1, characterized in that In the mixed solution described in step (2), the volume ratio of cyclohexane to ethanol is 1 to 5:

10.

8. The use of the intermetallic compound nanocatalyst with one-dimensional morphology prepared by the method according to claim 1, characterized in that it is used as a fuel cell electrode catalyst.

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