Intermetallic electron compound nano-particles as well as preparation method and application thereof

Abstract

The invention discloses intermetallic compound nanoparticles as well as a preparation method and application thereof, and relates to the technical field of synthesis of nano catalytic materials. The preparation method is a molten salt method, takes a metal source as a raw material of metal in intermetallic electron compound nanoparticles and takes a first metal halide as molten salt, and specifically comprises the following steps: mixing the metal source, the first metal halide and a reducing agent to obtain a mixture; the mixture is subjected to heat treatment, so that the first metal halide is molten, after heat preservation is conducted for preset time, the temperature is reduced to the room temperature at the preset cooling rate, and the intermetallic electron compound nano-particles are obtained; wherein the metal source comprises at least one of metal oxide, metal hydroxide and metal salt; the reducing agent comprises at least one of alkali metal, alkali metal hydride, alkaline earth metal and alkaline earth metal hydride. The molten salt method is adopted, the intermetallic electron compound nano-particles with the large specific surface area are prepared, the catalytic performance is improved, and meanwhile the method is simple, low in cost and high in yield and has universality.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-catalytic material synthesis, and in particular to intermetallic electron compound nanoparticles and a preparation method and application thereof. Background Art

[0002] As the core of the chemical industry, catalysts play an increasingly important role in the energy field. Traditional catalysts are mostly based on high-surface oxides, carbon, etc. In recent years, electrides have been widely used as a new material platform, which is expected to break through the bottleneck of traditional catalysts and reduce energy consumption in the catalytic industry.

[0003] Electrons have unique anionic electrons, and have excellent properties such as low work function, reversible hydrogen storage and release ability, and high carrier density, thus showing good catalytic performance in the fields of thermal catalytic ammonia synthesis, selective hydrogenation, and electrochemical reactions. Taking thermal catalytic ammonia synthesis (N2+H2→NH3) as an example, although Ru-based catalysts show excellent catalytic potential, they also face two problems: (1) The bond energy of the nitrogen-nitrogen triple bond is relatively high, resulting in a large energy barrier for the reaction, which is the rate-determining step of the reaction, thereby reducing the catalytic efficiency; (2) Since the reaction occurs on the surface of Ru, excessive adsorption of H will block the active sites and cause "hydrogen poisoning". When Ru metal particles are loaded on the surface of electrons, the above problems can be greatly alleviated. Electrons have a low work function comparable to that of alkali metals, making it easier for electrons to pass through the Ru surface to the antibonding orbital of the nitrogen-nitrogen triple bond, and the nitrogen-nitrogen triple bond is activated, which ultimately leads to the rate-determining step of the reaction from the break of the nitrogen-nitrogen triple bond to the formation of NH n The generation of species and the activation energy are significantly reduced. In addition, the anion vacancies of the electronic compound allow the excessive H adsorbed on the Ru surface to reversibly enter and exit, achieving dynamic equilibrium, which greatly alleviates the "hydrogen poisoning" phenomenon on the Ru surface.

[0004] Intermetallic electrides not only have excellent characteristics as electrides, but also have good chemical stability and single active site properties due to being intermetallic compounds, and have been rapidly developed in the field of catalysis. However, for catalyst materials or substrates, specific surface area is one of the key parameters that affect the release of their catalytic potential. A larger specific surface area means that more active sites or active metal loading sites can be exposed, thereby significantly improving their catalytic performance. Intermetallic electrides are usually prepared by arc melting method or solid-state reactions, and then the obtained bulk samples are hand-ground into powders in a mortar, which makes their specific surface area small and limits the full release of catalytic potential. Although some people have proposed the use of metal flash evaporation, that is, gasifying the raw materials at a high temperature of up to 10,000°C and then rapidly cooling them to obtain intermetallic electride nanoparticles, it is difficult to promote and apply it because it faces problems such as high cost, low yield, and phase formation difficulties caused by different element vapors.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0006] Based on the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide an intermetallic electronic compound nanoparticle and a preparation method and application thereof, aiming to solve the problems that the specific surface area of ​​the intermetallic electronic compounds prepared by the existing method is small, the catalytic performance cannot be effectively improved, or the preparation method of the existing intermetallic compounds is high in cost and low in yield.

[0007] The technical solution of the present invention is as follows:

[0008] In a first aspect of the present invention, a method for preparing intermetallic electron nanoparticles is provided, wherein the preparation method is a molten salt method, using a metal source as a raw material of the metal in the intermetallic electron nanoparticles and a first metal halide as a molten salt, and specifically comprising the following steps:

[0009] Mixing a metal source, a first metal halide and a reducing agent to obtain a mixture;

[0010] The mixture is subjected to heat treatment to melt the first metal halide, and after being kept at the temperature for a preset time, the temperature is cooled to room temperature at a preset cooling rate to obtain the intermetallic electron compound nanoparticles;

[0011] Wherein, the metal source includes at least one of a metal oxide, a metal hydroxide and a metal salt;

[0012] The reducing agent includes at least one of an alkali metal, an alkali metal hydride, an alkaline earth metal, and an alkaline earth metal hydride.

[0013] Optionally, the first metal halide includes at least one of an alkali metal halide and an alkaline earth metal halide.

[0014] Optionally, the first metal halide includes at least one of KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, CaCl2 and SrCl2; or the first metal halide includes a eutectic salt formed by at least two of KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, CaCl2 and SrCl2.

[0015] Optionally, the reducing agent includes at least one of an alkali metal, an alkali metal hydride, an alkaline earth metal and an alkaline earth metal hydride.

[0016] Optionally, the mass ratio of the metal source to the first metal halide is 1:(1-10).

[0017] Optionally, the actual amount of the reducing agent used is 1 to 10 times the theoretical amount of the reducing agent used to reduce the metal source.

[0018] Optionally, the step of grinding is further included before heat treating the mixture;

[0019] After cooling to room temperature at a preset cooling rate, the method further includes a cleaning step before obtaining the intermetallic electron compound nanoparticles.

[0020] The second aspect of the present invention provides an intermetallic electron compound nanoparticle, wherein the intermetallic electron compound nanoparticle is prepared by the preparation method of the present invention as described above.

[0021] Optionally, the intermetallic nanoparticles include LaCu 0.67 Si 1.33 Nanoparticles, Y5Si3 nanoparticles, YB2 nanoparticles or LaNi 0.5 Si 1.5 Nanoparticles.

[0022] The third aspect of the present invention provides a use of the intermetallic compound nanoparticles as described above in the field of catalysis.

[0023] Optionally, the metal intermetallic compound nanoparticles are used as a catalyst for synthesizing ammonia.

[0024] Beneficial effects: The present invention adopts a molten salt method, uses at least one of metal oxides, metal hydroxides and metal salts as a metal source, uses a first metal halide as a molten salt, and uses at least one of alkali metals, alkali metal hydrides, alkaline earth metals and alkaline earth metal hydrides as a reducing agent to prepare metallic intermetallic compound nanoparticles with a large specific surface area, and the catalytic performance is improved. At the same time, the method is simple, low in cost, high in yield, and has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The LaCu prepared in Example 1 0.67 Si 1.33 X-ray diffraction pattern of nanoparticles.

[0026] Figure 2 (a) is the LaCu prepared in Example 1 0.67 Si 1.33 Scanning electron microscopy image of nanoparticles, (b) LaCu prepared by arc melting method 0.67 Si 1.33 Scanning electron microscope image of .

[0027] Figure 3 This is the X-ray diffraction pattern of the Y5Si3 nanoparticles prepared in Example 2.

[0028] Figure 4 (a) is a scanning electron microscope image of the Y5Si3 nanoparticles prepared in Example 2, and (b) is a scanning electron microscope image of the Y5Si3 prepared by arc melting method.

[0029] Figure 5 This is the X-ray diffraction pattern of the YB2 nanoparticles prepared in Example 3.

[0030] Figure 6 (a) is a scanning electron microscope image of the YB2 nanoparticles prepared in Example 3, and (b) is a scanning electron microscope image of the YB2 prepared by arc melting method.

[0031] Figure 7 The LaNi prepared in Example 4 0.5 Si 1.5 X-ray diffraction pattern of nanoparticles.

[0032] Figure 8 (a) is the LaNi prepared in Example 4 0.5 Si 1.5 Scanning electron microscopy image of nanoparticles, (b) LaNi prepared by arc melting method 0.5 Si 1.5 Scanning electron microscope image of . DETAILED DESCRIPTION

[0033] The present invention provides an intermetallic electron nanoparticle and a preparation method and application thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] The embodiment of the present invention provides a method for preparing intermetallic electron compound nanoparticles, wherein the preparation method is a molten salt method, using a metal source as a raw material of the metal in the intermetallic electron compound nanoparticles (that is, the metal element in the metal source eventually becomes the metal element in the intermetallic electron compound nanoparticles), using a first metal halide as a molten salt, and specifically comprising the following steps:

[0036] S1, mixing a metal source, a first metal halide and a reducing agent to obtain a mixture;

[0037] S2, heat-treating the mixture to melt the first metal halide, keeping the mixture at a preset temperature for a preset time, and then cooling the mixture to room temperature at a preset cooling rate (for example, 4° C. / min) to obtain the intermetallic electron nanoparticles;

[0038] Wherein, the metal source includes at least one of a metal oxide, a metal hydroxide and a metal salt;

[0039] The reducing agent includes at least one of an alkali metal, an alkali metal hydride, an alkaline earth metal, and an alkaline earth metal hydride.

[0040] The present invention adopts a molten salt method, using at least one of metal oxides, metal hydroxides and metal salts as a metal source, a first metal halide as a molten salt, and at least one of alkali metals, alkali metal hydrides, alkaline earth metals and alkaline earth metal hydrides as a reducing agent (specifically a strong reducing agent). The metal source, the first metal halide and the reducing agent are mixed to obtain a mixture, and then the mixture is heat-treated so that the metal halide melts to form a molten salt. The reactant (i.e., the metal source) is dissolved using the molten salt as a solvent. During the heat preservation process, the solute (reactant) is evenly distributed in the solvent (i.e., the molten salt). During the cooling process, the solute is supersaturated, and multi-point nucleation and crystal growth occur, and finally, intermetallic electronic compound nanoparticles with a large specific surface area are prepared. The specific surface area of ​​the intermetallic electronic compound prepared by the traditional method (metal smelting + grinding) is increased by several times to hundreds of times, and the catalytic performance is improved. At the same time, the method is simple, low in cost, high in yield, and has universal applicability.

[0041] Specifically, in the embodiment of the present invention, firstly, by using a low melting point first metal halide as a solvent, and at the same time, the reaction raw materials (at least one of metal oxides, metal hydroxides and metal salts) have a high solubility and a high mobility in the molten salt, the synthesis temperature can be significantly reduced and the reaction time can be shortened. Secondly, since the high temperature molten salt can provide a multi-point nucleation environment, it provides ideal conditions for the preparation of nanoparticles, and anions and cations can enter the gaps between the products to avoid the agglomeration and growth of the products, so the product obtained by the molten salt method has a uniform structure and small particles. Finally, the shape and size of the particles can be more easily controlled by the molten salt method. By adjusting the type and amount of salt, the reaction temperature and time, etc., the intermetallic electronic compound still maintains the original crystal structure and electronic compound characteristics, while the specific surface area is several to hundreds of times higher than the sample obtained by the traditional method (metal smelting + grinding).

[0042] In the embodiment of the present invention, the temperature of the heat treatment is higher than or equal to the melting point of the first metal halide, and may also be lower than the melting point of the first metal halide. The temperature lower than the melting point of the metal halide is because the metal ions provided by the reducing agent will form a eutectic mixture with the first metal halide, thereby lowering the melting point of the first metal halide, so that the first metal halide can be melted below its melting point.

[0043] In step S1, in some embodiments, the first metal halide includes at least one of an alkali metal halide and an alkaline earth metal halide. The alkali metal halide and the alkaline earth metal halide have a relatively low melting point, and the reaction raw materials have a relatively high solubility and a relatively high mobility in the molten alkali metal halide and the alkaline earth metal halide.

[0044] In some embodiments, the first metal halide includes at least one of KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, CaCl2 and SrCl2; or the first metal halide includes a eutectic salt formed by at least two of KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, CaCl2 and SrCl2.

[0045] In some embodiments, the mass ratio of the metal source to the first metal halide is 1:(1-10), and the actual amount of the reducing agent used is 1-10 times the theoretical amount of the reducing agent used to reduce the metal source.

[0046] The intermetallic compound is LaCu 0.67 Si 1.33 For example, the chemical reaction formula for its synthesis is: La(OH)3+0.67Cu(OH)2+1.33SiO2+7CaH2=LaCu 0.67 Si1 .33 +7CaO+9.17H2;

[0047] Among them, La(OH)3, Cu(OH)2 and SiO2 are metal sources, CaH2 is the reducing agent. Assuming that the amounts of La(OH)3, Cu(OH)2 and SiO2 are 1 mol, 0.67 mol and 1.33 mol respectively, the theoretical amount of CaH2 used to reduce La(OH)3, Cu(OH)2 and SiO2 is 7 mol, and the actual amount of CaH2 used is 7 to 70 mol.

[0048] In some embodiments, the step of grinding the mixture before heat treatment is also included. Specifically, the mixture is ground evenly in a mortar to obtain a mixture.

[0049] In some embodiments, after cooling to room temperature at a preset cooling rate, a washing step is further included before obtaining the intermetallic electronic compound nanoparticles. Specifically, the product cooled to room temperature is washed with deionized water, centrifuged, washed with ethanol, and then dried to obtain the intermetallic electronic compound nanoparticles.

[0050] The embodiment of the present invention further provides an intermetallic electron compound nanoparticle, wherein the intermetallic electron compound nanoparticle is prepared by the preparation method of the present invention as described above.

[0051] Optionally, the intermetallic nanoparticles include LaCu 0.67 Si 1.33 Nanoparticles, Y5Si3 nanoparticles, YB2 nanoparticles or LaNi 0.5 Si 1.5 Nanoparticles.

[0052] The embodiment of the present invention further provides an application of the intermetallic compound nanoparticles as described above in the embodiment of the present invention in the field of catalysis.

[0053] In some specific embodiments, the intermetallic electron compound nanoparticles are used as catalysts for synthesizing ammonia. In the embodiments of the present invention, the intermetallic electron compound nanoparticles have a large specific surface area and have good catalytic activity when synthesizing ammonia.

[0054] The present invention will be further described below by means of specific examples.

[0055] Example 1

[0056] This embodiment provides an intermetallic electron compound (LaCu 0.67 Si 1.33 ) a method for preparing nanoparticles,

[0057] Among them, the synthesis of LaCu 0.67 Si 1.33 The reaction formula is:

[0058] La(OH)3+0.67Cu(OH)2+1.33SiO2+7CaH2=LaCu 0.67 Si 1.33 +7CaO+9.17H2; the preparation method comprises the following steps:

[0059] Follow LaCu 0.67 Si 1.33 According to the stoichiometric ratio of each element, LaCl3 and CuCl2 are transferred to a beaker, and deionized water is added to fully dissolve them. The solution turns blue.

[0060] Under stirring conditions, add excess alkaline solution to the blue solution until precipitation is complete and the precipitate appears blue; centrifuge and dry in a vacuum drying oven to obtain a blue La(OH)3 and Cu(OH)2 co-precipitated powder.

[0061] In a glove box filled with argon, La(OH)3 and Cu(OH)2 coprecipitated powder and silicon dioxide were placed in a mortar according to the stoichiometric ratio of the substances in the above reaction formula, and then KCl with a mass of 5 times that of the reactants (the reactants are La(OH)3 and Cu(OH)2 coprecipitated powder and silicon dioxide) and CaH2 with a mass of 70 times that of La(OH)3 (that is, the actual amount of CaH2 used is 10 times that of CaH2 required to theoretically reduce all reactants) were added. After being fully ground and mixed, the mixture was transferred to a stainless steel crucible with an exhaust hole, and then placed in a tube furnace, and the temperature was set to 700°C (because CaH2 was provided during the reaction). 2+ions, forming a eutectic mixture with KCl, lowering the melting point of the molten salt, so that the reaction temperature can be carried out below the melting point of the KCl molten salt), and keeping the temperature for 2 hours. Then, the temperature was lowered to room temperature at a cooling rate of 4°C / min.

[0062] The product was washed with deionized water, centrifuged, and washed with ethanol in sequence, and finally dried in a vacuum drying oven to obtain LaCu 0.67 Si 1.33 Nanoparticles.

[0063] Example 2

[0064] This embodiment provides a method for preparing intermetallic electron (Y5Si3) nanoparticles.

[0065] Among them, the reaction formula for synthesizing Y5Si3 is:

[0066] 5Y2O3+6SiO2+12Ca=2Y5Si3+12CaO;

[0067] The preparation method comprises the following steps:

[0068] In a glove box filled with argon, according to the stoichiometric ratio of each substance in the above reaction formula, Y2O3 and SiO2 were placed in a mortar, and then KCl / LiCl eutectic salt of 5 times the total mass of the reactants (i.e., Y2O3 and SiO2) and Ca of 4.8 times the amount of Y2O3 were added (i.e., the actual amount of Ca used was 2 times the amount of Ca required to theoretically reduce all reactants) and after being fully ground and mixed, the mixture was transferred to a stainless steel crucible sealed at both ends, and then placed in a tube furnace, set the program to heat up to 900°C, and keep it warm for 2 hours. Then the temperature was cooled to room temperature at a cooling rate of 4°C / min.

[0069] The product is sequentially washed with deionized water, centrifuged, and cleaned with an organic solvent, and finally dried in a vacuum drying oven to obtain Y5Si3 nanoparticles.

[0070] The KCl / LiCl eutectic salt is obtained by mixing KCl and LiCl in a molar ratio of 41:59, the same below.

[0071] Example 3

[0072] This embodiment provides a method for preparing intermetallic electron (YB2) nanoparticles.

[0073] Among them, the reaction formula for synthesizing YB2 is:

[0074] Y2O3+4B+3Ca=2YB2+3CaO;

[0075] The preparation method comprises the following steps:

[0076] In a glove box filled with argon, in order to inhibit the growth of heterogeneous phases, yttrium oxide Y2O3 and boron powder (B) in a non-stoichiometric ratio were weighed, specifically yttrium oxide Y2O3 and boron powder (B) in a molar ratio of 3:10 were placed in a mortar, and then 5 times the total mass of the reactants (i.e., Y2O3 and B) LiCl / KCl eutectic salt and 6 times the amount of Ca in Y2O3 (i.e., the actual amount of Ca used is 2 times the amount of Ca required to theoretically reduce all Y2O3) were added, and after fully grinding and mixing, the mixture was transferred to a stainless steel crucible sealed at both ends, and then placed in a tube furnace, set the program to heat up to 900°C, and keep warm for 2h. Then the temperature was cooled to room temperature at a cooling rate of 4°C / min.

[0077] The product is sequentially washed with deionized water, centrifuged, and cleaned with an organic solvent, and finally dried in a vacuum drying oven to obtain the target sample.

[0078] Example 4

[0079] This embodiment provides an intermetallic electron compound (LaNi 0.5 Si 1.5 ) A method for preparing nanoparticles, comprising the following steps:

[0080] SiO2 nanoparticles are placed in a mixed aqueous solution of La(NO3)3 and Ni(NO3)2 to form a suspension, wherein the molar ratio of La:Ni:Si=1:0.5:1.5.

[0081] The suspension was heated and stirred at 110° C. overnight to obtain a uniformly distributed solid mixture, which was then transferred to a stainless steel crucible and calcined at 500° C. for 2 h to obtain a La / Ni / Si oxide precursor.

[0082] In a glove box filled with argon, weigh a certain amount of La / Ni / Si oxide precursor, then weigh 2 times the amount of LiCl and 4 times the amount of CaH2, grind and mix them in a mortar, transfer the mixture to a stainless steel crucible with a vent, and then place it in a tube furnace, set the program to heat to 600°C, keep it for 2 hours, and then cool it down to room temperature at a cooling rate of 4°C / min.

[0083] The product was washed with deionized water, centrifuged, and washed with ethanol in sequence, and finally dried in a vacuum drying oven to obtain LaNi 0.5 Si 1.5 Nanoparticles;

[0084] In addition, LaNi 0.5 Si 1.5 The preparation can also be carried out according to the following reaction formula:

[0085] La2O3+NiO+3SiO2+10CaH2=2LaXi 0.5 Si 1.5 +10CaO+10H2;

[0086] Among them, La2O3, NiO and SiO2 are directly added in a stoichiometric ratio, the mass of LiCl added is twice the total mass of the reactants, and the mass of CaH2 added is 4 times the sum of the masses of La2O3, NiO and SiO2 (that is, the actual amount of CaH2 used is about 5.5 times the theoretical amount of CaH2 used for the reduction reactants).

[0087] test:

[0088] (1) LaCu prepared in Example 1 0.67 Si 1.33 The X-ray diffraction pattern of nanoparticles is shown in Figure 1 As shown (i.e., nano-LaCu 0.67 Si 1.33 ), it can be seen that LaCu 0.67 Si 1.33 .

[0089] The LaCu prepared in Example 1 0.67 Si 1.33 Nanoparticles and LaCu prepared by arc melting 0.67 Si 1.33 The scanning electron microscope image of Figure 2 As shown, it can be seen that the LaCu prepared in this embodiment 0.67 Si 1.33 Has a smaller particle size (nanoscale).

[0090] (2) The X-ray diffraction pattern of the Y5Si3 nanoparticles prepared in Example 2 is as follows: Figure 3 As shown (i.e. nano-Y5Si3 therein), it can be seen that Y5Si3 was successfully prepared in this embodiment.

[0091] The scanning electron microscope images of the Y5Si3 nanoparticles prepared in Example 2 and the Y5Si3 prepared by arc melting are shown in FIG. Figure 4 As shown, it can be seen that the Y5Si3 prepared in this embodiment has a smaller particle size (nanometer level).

[0092] (3) The X-ray diffraction pattern of the YB2 nanoparticles prepared in Example 3 is as follows Figure 5 As shown (i.e. nano-YB2), it can be seen that YB2 was successfully prepared in this example, but analysis showed that there was a small amount of YB4 impurity in the product.

[0093] The scanning electron microscopy images of the YB2 nanoparticles prepared in Example 3 and the YB2 prepared by arc melting method are as follows: Figure 6 As shown, it can be seen that the YB2 prepared in this embodiment has a smaller particle size (nanometer level).

[0094] (4) LaNi prepared in Example 4 0.5 Si 1.5 The X-ray diffraction pattern of nanoparticles is shown in Figure 7 As shown (i.e., the nano-LaNi 0.5 Si 1.5 ), it can be seen that LaNi 0.5 Si 1.5 .

[0095] The LaNi prepared in Example 4 0.5 Si 1.5 Nanoparticles and LaNi prepared by arc melting 0.5 Si 1.5 The scanning electron microscope image of Figure 8 As shown, it can be seen that the LaNi prepared in this embodiment 0.5 Si 1.5 Has a smaller particle size (nanoscale).

[0096] Among them, the LaCu prepared in Example 1 (molten salt method) 0.67 Si 1.33 Nanoparticles and Y5Si3 nanoparticles prepared in Example 2 (molten salt method) and LaCu 0.67 Si 1.33 The particle size and specific surface area of ​​Y5Si3 are shown in Table 1.

[0097] Table 1. Particle size and specific surface area results

[0098]

[0099] (5) Catalytic performance test

[0100] The catalyst LaCu prepared by arc melting combined with hand grinding 0.67 Si 1.33 , Y5Si3, YB2 and LaNi 0.5 Si 1.5 After loading Ru respectively, they are used for catalytic synthesis of ammonia.

[0101] The catalyst provided by the present invention, i.e., LaCu 0.67 Si 1.33Nanoparticles, Y5Si3 nanoparticles in Example 2, YB2 nanoparticles in Example 3, and LaNi nanoparticles in Example 4 0.5 Si 1.5 The nanoparticles are loaded with Ru and used for catalytic synthesis of ammonia.

[0102] The reaction conditions are catalyst = 0.1 g, N2:H2 = 1:3 (molar ratio), WHSV = 36000 mL·g -1 ·h -1 , pressure = 0.1 MPa, the results are shown in Table 2.

[0103] Table 2. Catalytic performance of each catalyst

[0104]

[0105] Among them, Bulk refers to the catalyst prepared by arc melting combined with hand grinding, and Nano refers to the catalyst prepared by the molten salt method of the present invention. 0.67 Si 1.33 It means that LaCu is prepared by arc melting combined with hand grinding. 0.67 Si 1.33 , Nano-LaCu 0.67 Si 1.33 The LaCu prepared by the molten salt method in Example 1 of the present invention 0.67 Si 1.33 Nanoparticles. The meanings of other catalysts are similar.

[0106] It can be seen that the intermetallic electronic compound nanoparticles prepared by the preparation method provided by the present invention have a larger specific surface area and a higher catalytic reaction rate.

[0107] In summary, the present invention adopts a molten salt method, using at least one of metal oxides, metal hydroxides and metal salts as a metal source, a first metal halide as a molten salt, and at least one of alkali metals, alkali metal hydrides, alkaline earth metals and alkaline earth metal hydrides as a reducing agent (specifically a strong reducing agent). The metal source, the first metal halide and the reducing agent are mixed to obtain a mixture, and then the mixture is heat-treated so that the metal halide melts to form a molten salt, and the reactant (i.e., the metal source) is dissolved in the molten salt as a solvent. During the heat preservation process, the solute (reactant) is evenly distributed in the solvent (i.e., the molten salt). During the cooling process, the solute is supersaturated, and multi-point nucleation and crystal growth occur, and finally, intermetallic electronic compound nanoparticles with a large specific surface area are prepared. The specific surface area is increased by several to hundreds of times compared with the intermetallic electronic compound prepared by the traditional method (metal smelting + grinding), and the catalytic performance is improved. At the same time, the method is simple, low in cost, high in yield, and has universal applicability.

[0108] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing intermetallic electron nanoparticles, characterized in that: The preparation method is a molten salt method, using a metal source as a raw material of the metal in the intermetallic electron compound nanoparticles and a first metal halide as a molten salt, and specifically includes the following steps: Mixing a metal source, a first metal halide and a reducing agent to obtain a mixture; The mixture is subjected to heat treatment to melt the first metal halide, and after being kept at the temperature for a preset time, the mixture is cooled to room temperature at a preset cooling rate to obtain the intermetallic electron compound nanoparticles; Wherein, the metal source includes at least one of a metal oxide, a metal hydroxide and a metal salt; The reducing agent includes at least one of an alkali metal, an alkali metal hydride, an alkaline earth metal, and an alkaline earth metal hydride.

2. The preparation method according to claim 1, characterized in that: The first metal halide includes at least one of an alkali metal halide and an alkaline earth metal halide.

3. The preparation method according to claim 1, characterized in that: The first metal halide includes at least one of KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, CaCl2 and SrCl2; or the first metal halide includes a eutectic salt formed by at least two of KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, CaCl2 and SrCl2.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the metal source to the first metal halide is 1:(1-10).

5. The preparation method according to claim 4, characterized in that: The actual amount of the reducing agent used is 1 to 10 times the theoretical amount of the reducing agent used to reduce the metal source.

6. The preparation method according to claim 1, characterized in that: The step of grinding the mixture before heat treatment is also included; After cooling to room temperature at a preset cooling rate, the method further includes a cleaning step before obtaining the intermetallic electron compound nanoparticles.

7. An intermetallic electron nanoparticle, characterized in that: The preparation is obtained by the preparation method according to any one of claims 1 to 6.

8. The intermetallic compound nanoparticles according to claim 7, characterized in that: The intermetallic electron nanoparticles include LaCu 0.67 Si 1.33 Nanoparticles, Y5Si3 nanoparticles, YB2 nanoparticles or LaNi 0.5 Si 1.5 Nanoparticles.

9. Use of the intermetallic compound nanoparticles according to claim 7 or 8 in the field of catalysis.

10. The use according to claim 9, characterized in that: The metal intermetallic compound nanoparticles are used as a catalyst for synthesizing ammonia.

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