Strip-shaped high-entropy alloy self-supporting electrocatalyst as well as preparation method and application thereof

Abstract

The invention provides a strip-shaped high-entropy alloy self-supporting electrocatalyst as well as a preparation method and application thereof, and belongs to the technical field of nano materials and catalysts. The chemical formula of the strip-shaped high-entropy alloy self-supporting electrocatalyst is FeaCobNicCrdMMn, in the formula, a, b, c, d and e represent the atomic ratio, and a: b: c: d: e = (1-3): (1-3): (1-3): 1: 1. The overpotential of the catalyst provided by the invention can reach 273.2 mV under the current density of 10mA. Cm <-2 > in electrochemical alkaline hydrogen evolution catalysis; and in electrochemical alkaline oxygen evolution catalysis, the overpotential can reach 338.9 mV under the current density of 10mA. Cm <-2 >, and excellent electro-catalysis efficiency is achieved. And after a multi-section current density stability test for 600h, the potential attenuation is only 1.26%, and the stability is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials and catalysts, and in particular to a strip-shaped high-entropy alloy self-supporting electrocatalyst and a preparation method and application thereof. Background Art

[0002] There is no clear answer to the definition of high entropy alloys. Systematic research on high entropy alloys based on performance has not been carried out yet. There are two definitions of high entropy alloys that are widely used: the first definition is: in terms of element composition and ratio, high entropy alloys are defined as alloys composed of five or more and less than thirteen main elements, the molar concentration of each main element is greater than 5% and less than 35%, and the mixing ratio of each element is close to the equimolar ratio. The second definition is to judge based on the entropy value of the alloy: if the total configuration molar entropy under ideal conditions is less than 0.69R, it is low entropy, if it is greater than 0.69R and less than 1.61R, it is medium entropy, and if it is greater than 1.61R, it is high entropy (R is the ideal gas constant).

[0003] High entropy alloys have the microstructure of a super solid solution, and have high mixing entropy effect, slow diffusion effect, lattice distortion effect, and multi-element harmonic effect. The multi-element harmonic effect is also called the cocktail effect, that is, the advantages of each element in the high entropy alloy can be uniformly reflected in the high entropy alloy, which makes the high entropy alloy have good catalyst development potential.

[0004] For a catalyst, the more effective active sites it has and the larger the exposed surface area, the better its catalytic performance. Different components are treated with different alloy processes to obtain the best porous morphology, thereby improving its catalytic performance. Summary of the invention

[0005] Based on the above content, the purpose of the present invention is to provide a strip-shaped high-entropy alloy self-supporting electrocatalyst and its preparation method and application. The catalyst provided by the present invention has excellent catalytic performance and catalytic stability.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is a strip-shaped high entropy alloy self-supporting electrocatalyst with a chemical formula of Fe a Co b Ni c Cr d Mn e , where a, b, c, d and e represent atomic ratios, a:b:c:d:e=(1-3):(1-3):(1-3):1:1.

[0008] The second technical solution of the present invention is a method for preparing the above-mentioned strip-shaped high entropy alloy self-supporting electrocatalyst, comprising the following steps:

[0009] According to the chemical formula in the above technical solution, each single substance raw material is weighed, melted, cooled and formed to obtain a high entropy alloy ingot;

[0010] After the high entropy alloy ingot is heated and melted, the molten alloy is rapidly solidified by a single-roll spinning method to obtain the strip-shaped high entropy alloy self-supporting electrocatalyst.

[0011] A third technical solution of the present invention is the use of the above-mentioned strip-shaped high entropy alloy self-supporting electrocatalyst as an electrode in electrochemical hydrogen evolution or oxygen evolution.

[0012] The present invention discloses the following technical effects:

[0013] The strip-shaped high entropy alloy self-supporting electrocatalyst provided by the present invention has uniform element distribution and forms a self-supporting structure. In electrochemical alkaline hydrogen evolution catalysis, the -2 The overpotential can reach 273.2 mV at a current density of 10 mA cm -2 The overpotential can reach 338.9 mV at a current density of , which has excellent electrocatalytic efficiency.

[0014] The strip-shaped high entropy alloy self-supporting electrocatalyst provided by the present invention has an alloy formed by selected elements, and after a 600-h multi-stage current density stability test, the potential decay of the alloy is only 1.26%, which has excellent stability.

[0015] The present invention uses a single-roll spinning method to perform mold cooling on the physically molten alloy to form a uniform face-centered cubic single-phase solid solution structure. Compared with existing catalysts, it has a more regular alloy surface, more accurate composition and size control, and excellent catalytic stability.

[0016] The preparation method provided by the invention has short process, low energy consumption and simple operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The XRD patterns of the strip-shaped high entropy alloy self-supporting electrocatalysts obtained in Examples 1-6;

[0019] Figure 2This is a SEM-EDS image of the strip-shaped high entropy alloy self-supporting electrocatalyst Fe1Co3Ni3Cr1Mn1 obtained in Example 1;

[0020] Figure 3 This is a SEM-EDS image of the strip-shaped high entropy alloy self-supporting electrocatalyst Fe3Co1Ni3Cr1Mn1 obtained in Example 2;

[0021] Figure 4 This is an XPS image of the strip-shaped high entropy alloy self-supporting electrocatalyst Fe1Co3Ni3Cr1Mn1 obtained in Example 1;

[0022] Figure 5 This is an XPS image of the strip-shaped high entropy alloy self-supporting electrocatalyst Fe3Co1Ni3Cr1Mn1 obtained in Example 2;

[0023] Figure 6 Graph showing the alkaline hydrogen evolution performance of the strip-shaped high entropy alloy self-supporting electrocatalyst obtained in Examples 1-6;

[0024] Figure 7 The alkaline oxygen evolution performance diagram of the strip-shaped high entropy alloy self-supporting electrocatalyst obtained in Examples 1-6;

[0025] Figure 8 This is a multi-stage current density stability test diagram of the strip-shaped high entropy alloy self-supporting electrocatalyst of Example 2;

[0026] Fig. 9 Schematic diagram of the preparation and testing process of the strip-shaped high entropy alloy self-supporting electrocatalyst in the present invention. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] The present invention provides a strip-shaped high entropy alloy self-supporting electrocatalyst, the chemical formula of which is Fe a Co b Ni c Cr d Mn e , where a, b, c, d and e represent atomic ratios, a:b:c:d:e=(1-3):(1-3):(1-3):1:1.

[0033] In some embodiments of the present invention, a:b:c:d:e=1:1:1:1:1, 3:1:1:1:1, 1:3:1:1:1, 1:1:3:1:1, 1:3:3:1:1 or 3:1:3:1:1, preferably 1:3:3:1:1 or 3:1:3:1:1.

[0034] Among the strip-shaped high entropy alloy self-supporting electrocatalysts provided by the present invention, the sample with the best alkaline hydrogen evolution performance is Fe1Co3Ni3Cr1Mn1, and the sample with the best alkaline oxygen evolution performance is Fe3Co1Ni3Cr1Mn1. In these two samples, Fe exists in +2 valence and +3 valence and in a metallic state, Co exists in a +2 valence form, Ni exists in two forms of Ni(OH)2 and NiO, Cr exists in a +2 valence and in a metallic state, and Mn exists in a +2 valence and +3 valence. Among them, Fe and Ni elements are both active centers of the reaction in the electrochemical hydrogen and oxygen evolution catalytic process. During the catalytic process, Cr forms protective Cr2O3 on the surface, thereby improving the corrosion resistance and stability of the overall alloy; the synergistic effect of Mn and other elements can optimize the adsorption energy of the reaction intermediates and improve the catalytic activity and selectivity. The presence of Co in a +2 valence form helps to stabilize the face-centered cubic (FCC) structure of the high entropy alloy. The FCC structure is usually associated with good plasticity and toughness. Co maintains this structure that is conducive to plastic deformation to a certain extent through interaction with other elements, thereby improving the overall toughness and ductility of the alloy.

[0035] The present invention also provides a method for preparing the strip-shaped high entropy alloy self-supporting electrocatalyst described in the above technical solution, comprising the following steps:

[0036] According to the chemical formula in the above technical solution, each single substance raw material is weighed, melted, cooled and formed to obtain a high entropy alloy ingot;

[0037] After the high entropy alloy ingot is heated and melted, the molten alloy is rapidly solidified by a single-roll spinning method to obtain the strip-shaped high entropy alloy self-supporting electrocatalyst.

[0038] In some embodiments of the present invention, before melting each single substance raw material, the steps of washing and drying each single substance raw material are also included. In the present invention, the purity of each single substance raw material is ≥ 99.9%.

[0039] In some embodiments of the present invention, the melting is performed by vacuum induction melting; the vacuum induction melting is specifically as follows: the melting is performed under an argon atmosphere of 400 hPa, the current passing through the induction coil is increased at a rate of 0.1 A per minute, the maximum current is 1.5 A, and the metal is finally melted and the temperature is raised to 1600-1700°C (preferably 1650°C), and the temperature is kept for 10 minutes, and then the current is reduced to 0 A to allow the molten metal to cool in the furnace until it solidifies; the above melting process is repeated for a total of 5-6 times.

[0040] In some embodiments of the present invention, the single-roller quenching method is specifically as follows: first, the air pressure in the single-roller quenching device is reduced to below 1Pa, then argon is introduced to 700hPa, the cooling roller in the device is started, the rotation speed is set to 10m / s, and the molten high-entropy alloy is blown out to the surface of the cooling roller. The high-speed rotating cooling roller quickly cools the alloy melt and brings it forward to obtain the strip-shaped high-entropy alloy self-supporting electrocatalyst; the cooling roller is a copper roller. The high-entropy alloy strip obtained by the present invention has an adjustable size, a thickness of about 50μm, and a width of 2 to 4mm.

[0041] The present invention uses a single-roll spinning method to quickly solidify the physically molten alloy, so that the five elements Fe, Co, Ni, Cr and Mn are evenly distributed in the sample, forming a uniform face-centered cubic single-phase solid solution structure, which effectively promotes its own catalytic ability.

[0042] The present invention uses vacuum induction melting and single-roller spinning to prepare high-entropy alloy strips, which has the following advantages:

[0043] (1) The method provided by the present invention has a short process, low energy consumption and is easy to operate.

[0044] (2) The high-entropy alloy obtained by induction melting has high purity and low oxidation degree. The high-entropy alloy strips obtained by single-roll spinning have controllable size and high mechanical strength. They have good catalytic performance when used for electrocatalysis, especially excellent stability.

[0045] The method provided by the present invention can extremely conveniently obtain various high entropy alloys by changing the type of added metals and different feed ratios. Therefore, the composition control is convenient and accurate. This method can adjust the comprehensive proportion of the required metals in the alloy according to the different functions of the required metals, and can form a supporting skeleton, improve the electrical conductivity, and accelerate electron transfer in the electrochemical hydrogen evolution / oxygen evolution link, thereby achieving better catalytic performance.

[0046] The present invention also provides the use of the above-mentioned strip-shaped high entropy alloy self-supporting electrocatalyst as an electrode in electrochemical hydrogen evolution or oxygen evolution.

[0047] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0048] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0049] Example 1

[0050] Step 1, weighing each elemental metal raw material according to the chemical formula of the atomic ratio Fe1Co3Ni3Cr1Mn1, and mixing them evenly to obtain a mixed metal raw material;

[0051] Step 2: Use a vacuum induction melting furnace to melt in an argon atmosphere of 400 hPa, increase the current passing through the induction coil to a maximum of 1.5 A at a rate of 0.1 A per minute, and finally melt the metal in the crucible, and heat it to 1600 degrees, keep it warm for 10 minutes, then reduce the current to 0 A to cool the molten metal in the furnace, cool it to solidification and then heat it again, and repeatedly melt the metal mixture 5 times in a vacuum induction melting furnace to ensure uniform high entropy alloy structure, and obtain a high entropy alloy ingot;

[0052] Step 3: Cut the obtained high-entropy alloy ingot into a small rectangular shape, put it into a quartz tube with a front end diameter of about 1 mm and a rear end connected to the induction furnace gas pipe for heating and melting, and after keeping warm for 5 seconds, the air pressure drop in the single-roller quenching equipment should be lowered to below 1Pa, and then argon gas is introduced to 700hPa, the copper roller in the equipment is started, and the speed is set to 10m / s. The molten high-entropy alloy is blown onto the surface of the copper roller by high-pressure argon gas, thereby obtaining a high-entropy alloy strip;

[0053] Step 4: Cut the obtained high entropy alloy strip into 1.5*0.5 cm, first ultrasonically clean it with anhydrous ethanol in an ultrasonic cleaning machine, and then dry it to finally obtain a strip-shaped high entropy alloy self-supporting electrocatalyst.

[0054] The high entropy alloy strip was clamped by a platinum electrode clamp and then formed into a three-electrode system with a Hg / HgO electrode and a graphite rod for the electrocatalytic water splitting performance test in a 1 M KOH environment.

[0055] The electrochemical workstation model of this embodiment is Shanghai Chenhua CHI760. During the test, the reference electrode is Hg / HgO electrode, the counter electrode is graphite electrode, and the high entropy alloy strip is clamped with platinum electrode clip, and the alloy strip is almost completely placed in the electrolyte using a rubber ring. The electrolyte is 1.0 mol / L KOH solution; at the same time, it is ensured that the platinum electrode cannot contact the electrolyte. The workstation software is turned on, and the hydrogen evolution reaction is cycled at -0.8V to -1.8V for 100 CV cycles, and the oxygen evolution reaction is cycled at 0V to 1.2V for 100 CV cycles before the performance test is performed. It is found that in 1.0 mol / L KOH solution, Fe1Co3Ni3Cr1Mn1 has excellent hydrogen evolution catalytic efficiency.

[0056] The tested high entropy alloy strip was removed from the platinum electrode clamp, and the surface area of ​​the alloy strip was calculated using the length and width of the cut during pre-treatment. The data was processed using the data exported from the electrochemical workstation and the specific surface area of ​​the alloy strip, the pH value of the electrolyte, and the standard potential of the reference electrode. The Tafel slope of Fe1Co3Ni3Cr1Mn1 with excellent hydrogen evolution catalytic efficiency was obtained to be 82.66 mV / dec.

[0057] In an alkaline environment, the hydrogen evolution catalytic curve is as follows Figure 6 As shown, the horizontal axis is the potential and the vertical axis is the current density. -2 It has the lowest overpotential of 273.2mV at a current density of .

[0058] Example 2

[0059] The chemical formula of the strip-shaped high entropy alloy self-supporting electrocatalyst provided in this embodiment is Fe3Co1Ni3Cr1Mn1. The preparation method is the same as that in Example 1.

[0060] The oxygen evolution curve of Fe3Co1Ni3Cr1Mn1 in this embodiment under alkaline environment is as follows Figure 7 As shown, the horizontal axis is the potential and the vertical axis is the current density. -2 It has the lowest overpotential of 338.9 mV and the lowest Tafel slope of 62.01 mV / dec at a current density of .

[0061] Example 3

[0062] The chemical formula of the strip-shaped high entropy alloy self-supporting electrocatalyst provided in this embodiment is Fe1Co1Ni1Cr1Mn1. The preparation method is the same as that in embodiment 1.

[0063] Example 4

[0064] The chemical formula of the strip-shaped high entropy alloy self-supporting electrocatalyst provided in this embodiment is Fe3Co1Ni1Cr1Mn1. The preparation method is the same as that in Example 1.

[0065] Example 5

[0066] The chemical formula of the strip-shaped high entropy alloy self-supporting electrocatalyst provided in this embodiment is Fe1Co3Ni1Cr1Mn1. The preparation method is the same as that in Example 1.

[0067] Example 6

[0068] The chemical formula of the strip-shaped high entropy alloy self-supporting electrocatalyst provided in this embodiment is Fe1Co1Ni3Cr1Mn1. The preparation method is the same as that in Example 1.

[0069] The strip-shaped high entropy alloy self-supporting electrocatalysts prepared in Examples 3-6 were subjected to the same electrocatalytic water splitting performance test as in Examples 1 and 2. The results showed that the strip-shaped high entropy alloy self-supporting electrocatalysts prepared in Examples 3-6 had excellent hydrogen evolution / oxygen evolution catalytic efficiency ( Figure 6 , Figure 7 ).

[0070] The strip-shaped high entropy alloy self-supporting electrocatalyst of Example 2 was tested for multi-stage current density stability. Figure 8 It can be seen that after 600h of multi-stage current density stability test, the potential decay is only 1.26%, indicating that it has excellent stability.

[0071] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A strip-shaped high entropy alloy self-supporting electrocatalyst, characterized in that: The chemical formula is Fe a Co b Ni c Cr d Mn e , where a, b, c, d and e represent atomic ratios, a:b:c:d:e=(1-3):(1-3):(1-3):1:

1.

2. The strip-shaped high entropy alloy self-supporting electrocatalyst according to claim 1, characterized in that: The a:b:c:d:e=1:1:1:1:1, 3:1:1:1:1, 1:3:1:1:1, 1:1:3:1:1, 1:3:3:1:1 or 3:1:3:1:

1.

3. A method for preparing the strip-shaped high entropy alloy self-supporting electrocatalyst according to claim 1, characterized in that: The following steps are involved: Weigh each elemental raw material according to the chemical formula in claim 1, melt it, cool it and shape it to obtain a high entropy alloy ingot; After the high entropy alloy ingot is heated and melted, the molten alloy is rapidly solidified by a single-roll spinning method to obtain the strip-shaped high entropy alloy self-supporting electrocatalyst.

4. The method for preparing a strip-shaped high entropy alloy self-supporting electrocatalyst according to claim 3, characterized in that: Before melting each single substance raw material, the process also includes the steps of washing and drying each single substance raw material.

5. The method for preparing a strip-shaped high entropy alloy self-supporting electrocatalyst according to claim 3, characterized in that: The melting is carried out by vacuum induction melting method; the vacuum induction melting method is specifically as follows: the melting is carried out in an argon atmosphere of 400hPa, the current passing through the induction coil is increased at a rate of 0.1A per minute, the maximum current is 1.5A, the metal is finally melted, and the temperature is raised to 1600-1700°C, kept warm for 10 minutes, and then the current is reduced to 0A to cool the metal melt in the furnace until it solidifies; the above melting process is repeated for a total of 5-6 times.

6. The method for preparing a strip-shaped high entropy alloy self-supporting electrocatalyst according to claim 3, characterized in that: The single-roller quenching method is specifically as follows: first, the air pressure in the single-roller quenching equipment is reduced to below 1Pa, then argon gas is introduced to 700hPa, the cooling roller in the equipment is started, the rotation speed is set to 10m / s, and the molten high-entropy alloy is blown out to the surface of the cooling roller. The high-speed rotating cooling roller quickly cools the alloy melt and brings it forward to obtain the strip-shaped high-entropy alloy self-supporting electrocatalyst.

7. Use of the strip-shaped high entropy alloy self-supporting electrocatalyst according to claim 1 or 2 as an electrode in electrochemical hydrogen evolution or oxygen evolution.

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