Preparation method of high entropy alloy catalyst based on ultra-low temperature treatment strengthening

Abstract

The present invention discloses a preparation method of a high entropy alloy catalyst based on ultra-low temperature treatment strengthening, specifically: smelting a precursor metal to form a HEAs ingot with an FCC crystal structure; HEAs ingots are made into HEAs ribbons or sheets by melt quenching or rolling method; HEAs ribbons or sheets are placed in an ultra-low temperature medium for ultra-low temperature treatment, then returned to temperature at room temperature, and ultra-low temperature and return to temperature treatment are repeated 1 5 times to obtain a HEAs catalyst with high catalytic performance. The high entropy alloy HEAs of the present invention has excellent mechanical properties, high electrical conductivity, and strong stability, and can effectively reduce the amount of precious metals used; At the same time, by virtue of the interface synergy between alkali metals and precious metals and between precious metals and precious metals, catalytic performance is significantly improved. In addition, ultra-low temperature treatment is simple and easy to operate, can refine grains, and regulate the orientation of the HEAs surface crystal planes, which will further significantly enhance the catalytic performance of the catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic material preparation, and in particular relates to a method for preparing a high-entropy alloy catalyst based on ultra-low temperature treatment strengthening. Background Art

[0002] In recent years, high-entropy alloys (HEAs) have aroused great interest in the development and application of electro- / thermo-catalytic clean energy conversion due to their unique microstructure, excellent thermal stability, outstanding structural stability and catalytic activity for various reactions (including hydrogen evolution, oxygen evolution, oxygen reduction, carbon dioxide reduction, ammonia decomposition, etc.).

[0003] HEAs, as emerging materials, contain five or more elements in nearly equal atomic percentages. High entropy enhances the formation and stability of random single-phase solid solutions with a variety of structures, such as face-centered cubic (FCC), body-centered cubic (BCC), hexagonal close-packed (HCP), and orthorhombic. However, due to the complexity of multicomponent HEAs and their interactions, they still face many problems and challenges. For example, the synthesis methods of HEAs are generally complex, and the few relatively simple synthesis methods are only applicable to HEAs with high metal reduction potentials and easy preparation. The potential catalytic performance of HEAs catalysts has not been fully explored, and their performance is not very excellent. Therefore, it is extremely necessary to more rationally design HEAs catalysts and to manufacture them on a large scale to ultimately obtain low-cost and highly active HEAs catalysts. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a high entropy alloy catalyst based on ultralow temperature treatment strengthening, which can regulate the surface crystal orientation of the HEAs catalyst through ultralow temperature treatment, thereby improving the catalytic performance of the HEAs catalyst.

[0005] The technical solution adopted by the present invention is a method for preparing a high entropy alloy catalyst based on ultra-low temperature treatment strengthening, which is specifically implemented according to the following steps:

[0006] Step 1, melting the precursor metal to form a HEAs ingot with an FCC crystal structure;

[0007] Step 2, forming the HEAs ingot into a HEAs ribbon or sheet by melt quenching or rolling;

[0008] Step 3: Place the HEAs ribbon or sheet obtained in step 2 in an ultra-low temperature medium for ultra-low temperature treatment, then warm it up at room temperature, and repeat the ultra-low temperature and warming treatment 1-5 times to obtain a HEAs catalyst with high catalytic performance.

[0009] The present invention is also characterized in that:

[0010] In step 1, specifically:

[0011] The precious metal wire and the metal wire are placed in an acetone solution, ultrasonically cleaned, and then ultrasonically cleaned with ethanol and dried. The precious metal wire and the metal wire are placed in a crucible and repeatedly arc-melted under argon atmosphere protection to form HEAs ingots.

[0012] The metal wire is any four or more of Ni wire, Fe wire, Ce wire, Cu wire, Al wire, Sn wire, Pb wire, and Ca wire; the precious metal wire is any one or more of Pt wire, Pd wire, and Ag wire.

[0013] The process parameters of arc melting are: current 90-120A, heating temperature 800-1200℃, and repeated melting times 4 times.

[0014] In step 2, the rolling method is specifically as follows: the HEAs ingot obtained in step 1 is cut or rolled into a thin sheet with a thickness of 0.1 mm to 1 mm, and then ultrasonically cleaned in acetone and ethanol solutions in sequence, and dried to obtain a HEAs sheet.

[0015] In step 2, the melt quenching method is specifically as follows: the HEAs ingot obtained in step 1 is crushed and placed in a quartz tube. After current induction heating to a molten state, the molten HEAs liquid is blown onto a rotating water-cooled copper roller with argon gas at a speed of 600-2500 rpm, and instantly cooled and solidified to form a HEAs thin strip.

[0016] In step 3, the ultra-low temperature treatment time is 2-48 hours, and the warming time is 4-24 hours; the ultra-low temperature medium is liquid nitrogen or liquid argon.

[0017] The beneficial effects of the present invention are as follows: the high-entropy alloys (HEAs) of the present invention have excellent mechanical properties, high electrical conductivity, and strong stability, which can effectively reduce the use of precious metals; at the same time, the catalytic performance is significantly improved by the synergistic effects between the interfaces of alkali metals and precious metals, and between precious metals. In addition, the ultra-low temperature treatment is simple and easy to operate, which can refine the grains and regulate the surface crystal orientation of the HEAs, which will further significantly enhance the catalytic performance of the catalyst. The high-performance HEAs catalysts prepared using the above method have the advantages of controllable composition, strong stability, simple preparation process, good catalytic effect, and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a plane scanning electron microscope photograph of the catalyst sample of the present invention;

[0019] Figure 2 CV curves of catalyst samples with different rotation speeds in methanol according to the present invention;

[0020] Figure 3 CV curves of the catalyst samples subjected to different ultra-low temperature treatment times in methanol;

[0021] Figure 4 This is the CV curve of commercial Pd / C catalyst in alkaline solution under the same test conditions;

[0022] Figure 5 This is the CV curve of commercial Pd / C catalyst in methanol under the same test conditions. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to specific embodiments and the accompanying drawings.

[0024] The preparation method of the high entropy alloy catalyst based on ultra-low temperature treatment strengthening of the present invention is specifically implemented according to the following steps:

[0025] Step 1, melting the precursor metal to form a HEAs ingot with an FCC crystal structure;

[0026] Specifically, the precious metal wire and the metal wire are placed in an acetone solution, ultrasonically cleaned to remove surface oil, and then ultrasonically cleaned with ethanol. After drying, the precious metal wire and the metal wire are placed in a crucible and repeatedly arc-melted under argon atmosphere to form HEAs ingots;

[0027] The metal wire is any four or more of Ni wire, Fe wire, Ce wire, Cu wire, Al wire, Sn wire, Pb wire, and Ca wire;

[0028] The noble metal wire is any one or more of Pt wire, Pd wire, and Ag wire;

[0029] The content of each element is 5-35at.%;

[0030] Arc melting process parameters: current 90-120A, heating temperature 800-1200℃, repeated melting times 4 times; ultrasonic cleaning time is 5-10 minutes;

[0031] In the HEAs ingot, precious metals Pd, Pt, and Ag are active components; alkali metal wires Ni wire, Fe wire, Ce wire, Cu wire, Al wire, Sn wire, Pb wire, and Ca wire are co-catalyst components;

[0032] Step 2, forming the HEAs ingot into a HEAs ribbon or sheet by melt quenching or rolling;

[0033] The calendering method specifically comprises the following steps: cutting or calendering the HEAs ingot obtained in step 1 into a sheet with a thickness of 0.1 mm to 1 mm, then ultrasonically cleaning it in acetone and ethanol solutions in sequence, and drying it to obtain a HEAs sheet;

[0034] The melt quenching method is as follows: the HEAs ingot prepared in step 1 is crushed and placed in a quartz tube. After current induction heating is performed until it is molten, the molten HEAs liquid is blown onto a rotating water-cooled copper roller using argon gas at a certain speed, where it is instantly cooled and solidified to form a HEAs thin ribbon.

[0035] The rotation speed is 600-2500 rpm; preferably the rotation speed is 2500 rpm, 1800 rpm, 1100 rpm or 600 rpm;

[0036] Step 3: placing the HEAs ribbon or sheet obtained in step 2 in a cryogenic medium for cryogenic treatment, then returning the temperature to room temperature, and repeating the cryogenic treatment and returning the temperature to room temperature 1-5 times to obtain a sheet or ribbon-type HEAs catalyst with certain strength and flexibility and high catalytic performance;

[0037] The ultra-low temperature treatment time is 2-48 hours, and the warming time is 4-24 hours; the ultra-low temperature medium is liquid nitrogen or liquid argon.

[0038] The advantages of the present invention's method for preparing a high-entropy alloy catalyst based on ultra-low temperature treatment strengthening are as follows:

[0039] 1. The HEAs catalyst obtained by the method of the present invention has uniform composition, is precisely controlled, and has a simple preparation process, making it easy to achieve batch production;

[0040] 2. The catalytic performance is directly related to the grain size of the active metal, the electrochemically active exposed area in the electrolyte solution, and the surface crystal plane orientation. The smaller the grain size, the larger the electrochemically active specific surface area, and the better the electrocatalytic performance of the catalyst. At the same time, the cost of the catalyst will be greatly reduced, and the cost-effectiveness will be significantly improved. The present invention controls the grain size, electrochemically active specific surface area, and preferred orientation of the surface crystal plane of the HEAs catalyst by regulating the rotational speed during the melt rapid quenching process, thereby improving the catalyst performance.

[0041] 3. Ultra-low temperature treatment can cause the metal or alloy to produce a volume shrinkage effect, transfer the kinetic energy between atoms, make the atoms more tightly bonded, thereby refining the grains and increasing the active exposure area. While improving the organization and performance, due to thermal expansion and contraction, a large compressive stress is generated inside. This internal compressive stress causes the grains to rotate and changes the grain orientation, thereby enhancing the preferred orientation growth trend of the crystal plane, which will further achieve the purpose of improving the catalyst performance.

[0042] 4. Because the crystal plane orientation between the precursor alloy and the nanoporous metal obtained after dealloying is hereditary, if the HEAs catalyst contains Al and the elements are 6 or more, nanoporous high entropy alloy (HEAs-NP) catalysts can be prepared exploratoryly. This is because there is a genetic effect (grain size, crystal plane orientation) between the HEAs catalyst and the HEAs-NP catalyst. After dealloying, the activity of the HEAs-NP catalyst will be further significantly improved due to the exposed surface of the active site, which will further significantly increase the electrochemical activity specific area of the catalyst, and its electrocatalytic performance will also be significantly improved.

[0043] Example 1

[0044] The preparation method of the high entropy alloy catalyst based on ultra-low temperature treatment strengthening of the present invention is specifically implemented according to the following steps:

[0045] Step 1, melting the precursor metal to form a HEAs ingot with an FCC crystal structure;

[0046] Specifically, Pt wire, Ni wire, Fe wire, Ce wire, Cu wire, and Al wire were placed in an acetone solution and ultrasonically cleaned to remove surface oil stains. The wires were then ultrasonically cleaned with ethanol and dried. The metal wires were then placed in a crucible and repeatedly arc-melted under argon atmosphere to form HEAs ingots.

[0047] The arc melting process parameters are as follows: current 90A, heating temperature 800℃, repeated melting times 4 times; ultrasonic cleaning time is 5 minutes;

[0048] Step 2, forming HEAs sheets from the HEAs ingots by a calendering method;

[0049] Specifically, the HEAs ingot obtained in step 1 is cut or rolled into a sheet with a thickness of 0.1 mm, and then ultrasonically cleaned in acetone and ethanol solutions in sequence, and dried to obtain a HEAs sheet;

[0050] Step 3: placing the HEAs sheet obtained in step 2 in a cryogenic medium for cryogenic treatment, and then returning the temperature to room temperature. Repeating the cryogenic treatment and returning the temperature to room temperature three times, a sheet or ribbon-type HEAs catalyst with a certain strength and flexibility can be obtained;

[0051] The ultra-low temperature treatment time is 10 hours, and the warming time is 10 hours; the ultra-low temperature medium is liquid nitrogen.

[0052] Example 2

[0053] The preparation method of the high entropy alloy catalyst based on ultra-low temperature treatment strengthening of the present invention is specifically implemented according to the following steps:

[0054] Step 1, melting the precursor metal to form a HEAs ingot with an FCC crystal structure;

[0055] Specifically, Pd wire, Ag wire, Cu wire, Al wire, Sn wire, and Pb wire were placed in an acetone solution and ultrasonically cleaned to remove surface oil stains. The wires were then ultrasonically cleaned with ethanol and dried. The metal wires were then placed in a crucible and repeatedly arc-melted under argon atmosphere to form HEAs ingots.

[0056] The arc melting process parameters are: current 100A, heating temperature 900℃, repeated melting times 4 times; ultrasonic cleaning time is 10min;

[0057] Step 2, forming HEAs thin ribbons from the HEAs ingots by rapid quenching the melt;

[0058] Specifically, the HEAs ingot prepared in step 1 is crushed and placed in a quartz tube. After current induction heating to a molten state, the molten HEAs liquid is blown onto a rotating water-cooled copper roller at a speed of 1800 rpm using argon gas, and instantly cooled and solidified to form a HEAs thin ribbon.

[0059] Step 3: placing the HEAs ribbon obtained in step 2 in a cryogenic medium for cryogenic treatment, and then returning the temperature to room temperature. Repeating the cryogenic treatment and returning the temperature to room temperature three times, a sheet or ribbon-type HEAs catalyst with certain strength and flexibility can be obtained;

[0060] The ultra-low temperature treatment time is 15 hours, and the warming time is 5 hours; the ultra-low temperature medium is liquid argon.

[0061] Example 3

[0062] The preparation method of the high entropy alloy catalyst based on ultra-low temperature treatment strengthening of the present invention is specifically implemented according to the following steps:

[0063] Step 1, melting the precursor metal to form a HEAs ingot with an FCC crystal structure;

[0064] Specifically, Pt wire, Pd wire, Ni wire, Fe wire, Ce wire, Cu wire, Al wire, and Sn wire were placed in an acetone solution and ultrasonically cleaned to remove surface oil stains. The wires were then ultrasonically cleaned with ethanol and dried. The metal wires were then placed in a crucible and repeatedly arc-melted under argon atmosphere to form HEAs ingots.

[0065] Arc melting process parameters: current 120A, heating temperature 1200℃, repeated melting times 4 times; ultrasonic cleaning time is 10min;

[0066] Step 2, forming HEAs sheets from the HEAs ingots by a calendering method;

[0067] Specifically, the HEAs ingot obtained in step 1 is cut or rolled into a sheet with a thickness of 1 mm, and then ultrasonically cleaned in acetone and ethanol solutions in sequence, and dried to obtain a HEAs sheet;

[0068] Step 3: placing the HEAs sheet obtained in step 2 in a cryogenic medium for cryogenic treatment, and then returning the temperature to room temperature. Repeating the cryogenic treatment and returning the temperature to room temperature for 5 times, a sheet or ribbon-type HEAs catalyst with a certain strength and flexibility can be obtained;

[0069] The ultra-low temperature treatment time is 20 hours, and the warming time is 15 hours; the ultra-low temperature medium is liquid nitrogen.

[0070] Figure 1 This is a planar scanning electron microscope photograph of a HEAs catalyst sample prepared by the method of the present invention, which shows that the ultra-low temperature treatment does not cause large cracks in the ribbon due to stress, and still maintains good mechanical properties;

[0071] Figure 2 Figure 3 is the CV curve of the catalyst samples with different rotation speeds in methanol. It can be seen from the figure that the performance of the catalyst in electrocatalytic oxidation of methanol shows a trend of first increasing and then decreasing with the increase of rotation speed. When the rotation speed is 1800 rpm, the peak current density of the sample is the largest and the electrocatalytic activity is the best, indicating that the rotation speed is an important indicator affecting the catalyst performance.

[0072] Figure 3 It is the CV curve of the catalyst samples of the present invention with different deep freezing times in methanol; it can be seen from the figure that the electrocatalytic oxidation performance of the catalyst for methanol shows a trend of first increasing and then decreasing with the increase of the number of ultra-low temperature treatments. When the ultra-low temperature treatment is carried out twice, the electrocatalytic performance of the sample is the best, indicating that the number of ultra-low temperature treatments is an important indicator affecting the performance of the catalyst. Reasonable setting of the number of ultra-low temperature treatments can further significantly improve the electrocatalytic performance of the catalyst.

[0073] Figure 4 and Figure 5 The CV curves of commercial Pd / C catalyst in alkali solution and methanol under the same test conditions are combined. Figure 2 and Figure 3 It can be seen that when the appropriate rotation speed is selected during the melt rapid quenching process, the performance of the obtained catalyst is about 4 times that of the commercial Pd / C catalyst. After further appropriate ultra-low temperature treatment, the performance of the obtained catalyst is about 15 times that of the commercial Pd / C catalyst.

Claims

1. A method for preparing a high entropy alloy catalyst based on ultra-low temperature treatment strengthening, characterized in that: Please follow the steps below to implement it: Step 1: Melt the precursor metal to form a HEAs ingot with an FCC crystal structure; specifically: The noble metal wire and the metal wire are placed in an acetone solution, ultrasonically cleaned, and then ultrasonically cleaned with ethanol, dried, and the noble metal wire and the metal wire are placed in a crucible and repeatedly arc-melted under an argon atmosphere to form a HEAs ingot; The metal wire is any four or more of Ni wire, Fe wire, Ce wire, Cu wire, Al wire, Sn wire, and Pb wire; the noble metal wire is any one or more of Pt wire, Pd wire, and Ag wire; Step 2, forming the HEAs ingot into a HEAs ribbon or sheet by melt quenching or rolling; Step 3: placing the HEAs ribbon or sheet obtained in step 2 in a cryogenic medium for cryogenic treatment, and then returning the temperature to room temperature. Repeating the cryogenic and returning temperature treatments 1-5 times, a HEAs catalyst with high catalytic performance can be obtained; The ultra-low temperature treatment time is 2-48 hours, and the warming time is 4-24 hours; the ultra-low temperature medium is liquid nitrogen or liquid argon.

2. The method for preparing a high entropy alloy catalyst based on ultralow temperature treatment strengthening according to claim 1, characterized in that: The process parameters of arc melting are: current 90-120A, heating temperature 800-1200℃, and repeated melting times 4 times.

3. The method for preparing a high entropy alloy catalyst based on ultralow temperature treatment strengthening according to claim 1, characterized in that: In the step 2, the calendering method is specifically: The HEAs ingot obtained in step 1 is cut or rolled into thin sheets with a thickness of 0.1 mm to 1 mm, and then ultrasonically cleaned in acetone and ethanol solutions in sequence, and dried to obtain HEAs thin sheets.

4. The method for preparing a high entropy alloy catalyst based on ultralow temperature treatment strengthening according to claim 1, characterized in that: In step 2, the melt quenching method specifically comprises the following steps: the HEAs ingot obtained in step 1 is crushed and placed in a quartz tube, and after current induction heating is performed until it is molten, the molten HEAs liquid is blown onto a rotating water-cooled copper roller using argon gas at a speed of 600-2500 rpm, and instantly cooled and solidified to form a HEAs thin ribbon.

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