Preparation Method and Application of a Nanoalloy Catalyst

Abstract

The invention discloses a nano high-entropy alloy electrocatalyst and a preparation method thereof. The material is composed of a three-dimensional porous copper foam substrate and FeCoNiCuMn high-entropy alloy nanoparticles supported on the three-dimensional copper foam substrate. The preparation method comprises the following steps: (a) weighing various sulfates, adding a certain amount of deionized water to prepare a solution, and successively adding a small amount of citric acid and boric acid, stirring until a clear solution is prepared for standby use; (b) soaking the copper foam in a hydrochloric acid solution and then washing it with ethanol and deionized water in sequence; (c) preparing high-entropy alloy particles by electrodeposition; and (d) using the prepared high-entropy alloy catalyst as a working electrode to perform an electrochemical performance test. The nano high-entropy alloy particles of the invention have a diameter of 5-20 nm and catalyze oxygen evolution at a flow rate of 100 mA cm ‑2 The overpotential at a current density of 270-300 mV (vs RHE) is achieved.

Description

Technical Field

[0001] The present invention relates to the preparation of high entropy alloy nanoparticles and their application in the field of electrocatalysts. Background Art

[0002] The overuse of fossil fuels has led to severe environmental pollution, prompting a desire to find green energy sources that can address the energy crisis while also reducing environmental pollution. To address this issue, researchers worldwide have invested significant effort in developing renewable, pollution-free energy sources. Among these, hydrogen evolution through water electrolysis is considered one of the most promising technologies for replacing fossil fuels. Water electrolysis involves two half-reactions: oxygen evolution at the anode and hydrogen evolution at the cathode. The oxygen evolution reaction at the anode is a four-electron reaction, and its slow reaction rate significantly impacts the rate of hydrogen evolution at the cathode. To address this issue, catalysts must be added to accelerate the reaction. Precious metal catalysts such as RuO2, IrO2, and Pt can significantly improve the catalytic rate. However, these precious metal catalysts are expensive and their limited Earth reserves preclude their large-scale use, severely limiting their industrial applications. Consequently, the development of catalysts with low costs and high catalytic efficiency has become a hot topic.

[0003] Among the numerous elements, transition metals have attracted the attention of researchers due to their abundance and low cost. While synthetic transition metal alloy catalysts have demonstrated promising catalytic performance, they remain insufficient for industrial water electrolysis. To better adapt to industrial development, the synthesis of transition metal high-entropy alloy electrocatalysts is anticipated to yield superior performance sufficient for industrial applications. The advantages of transition metal high-entropy alloys include low cost, a wide variety of elements, and the resulting lattice distortion that creates abundant active sites.

[0004] However, recent reports on high-entropy alloy catalysts have found that size is a key factor in regulating catalyst performance; at the same time, most of the high-entropy alloy catalysts reported at this stage cannot exhibit excellent performance at high current density.

[0005] In order to solve the above problems, the present invention is proposed. Summary of the Invention

[0006] The present invention aims to provide a method for preparing a nano-high entropy alloy electrocatalyst FeCoNiCuMn for improving the oxygen evolution reaction rate. The nano-high entropy alloy nanoparticles have a diameter of 5-20nm, are face-centered cubic, and are formed by electrodeposition and supported on foamed copper.

[0007] The three-dimensional porous copper foam substrate increases the catalyst loading area, providing abundant active sites and surface area. It also effectively prevents the degradation of high-entropy alloy performance due to agglomeration, thereby improving catalyst stability. Furthermore, the porous copper foam material enhances the catalyst's conductivity. The porous structure facilitates the transport of reactants and products, enhancing the catalytic activity of the high-entropy alloy electrocatalyst.

[0008] The present invention mainly focuses on the preparation and application of high entropy alloys. To achieve this purpose, the present invention provides a technical solution, including the following steps:

[0009] Step 1, cleaning of the foam copper substrate:

[0010] Cut the foam copper into 1×1cm pieces 2 The blocks were soaked in 1M hydrochloric acid solution for 10 min, then ultrasonically cleaned with ethanol solution and deionized water, and then dried in a 60°C oven for later use.

[0011] Step 2, prepare the electrolyte:

[0012] A 0.1 M mixed solution of ferrous sulfate, cobalt sulfate, nickel sulfate, copper sulfate, and manganese sulfate was added with 0.02 M citric acid, 0.65 M boric acid, and 0.085 M L-ascorbic acid and dissolved in deionized water to prepare a FeCoNiCuMn electrodeposition solution;

[0013] Step 3: Preparation of high entropy alloy nanoparticles by electrodeposition:

[0014] High-entropy alloy nanoparticles were synthesized by electrodeposition, with electrochemical reduction deposition performed in the voltage range of 4-8 V, using a graphite electrode as the anode and copper foam as the cathode. After deposition, the nanoparticles were rinsed three times with ethanol.

[0015] Step 4, drying:

[0016] The rinsed sample was dried in an oven at 50° C. to obtain a high entropy alloy nanoparticle electrocatalyst.

[0017] The FeCoNiCuMn nano-high entropy alloy electrocatalyst prepared in the above steps is used for efficient water electrolysis and oxygen evolution in an alkaline environment. The application method is to use the copper foam loaded with high entropy alloy nanoparticles using the above method as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire as the counter electrode to establish a three-electrode system for efficient water decomposition and oxygen evolution.

[0018] According to the above scheme, the electrolyte in the electrochemical system is 1M KOH solution, and the test voltage range is 0.2-1.3V.

[0019] The high-entropy alloys prepared in this patent differ from conventional alloys in that they modulate their electronic structure, thereby enhancing intrinsic catalytic activity. Lattice distortion caused by the varying atomic radii of the metals in the alloy stimulates the creation of active sites. Furthermore, high-entropy alloys offer a certain degree of improved electrical conductivity.

[0020] The prepared high-entropy alloy nanoparticles are loaded on copper foam. Due to the three-dimensional network structure of the copper foam itself, a large active area can be obtained. Its special network structure allows the electrolyte to fully contact with the catalyst, accelerating the transmission of electrons, thereby significantly improving the catalytic effect of the catalyst.

[0021] The high entropy alloy catalyst prepared in this patent is used as the working electrode in a three-electrode system with a voltage window of 0.2-1.3 V. Electrochemical tests are performed in 1 M KOH solution. The high entropy alloy electrocatalyst exhibits a high electrochemical performance at 100 mA cm -2 The overpotential at the current density is 270-300mV. Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The high-entropy alloy of FeCoNiCuMn prepared by direct current electrodeposition has low cost and easy composition control.

[0023] 2. Loading on copper foam can obtain a larger active area. Nano-sized high-entropy alloys were prepared by electrodeposition, with diameters of high-entropy alloy nanoparticles ranging from 5-20nm. Loading on porous copper foam provides the catalyst with better conditions for electron transmission, ensuring its high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the preparation process of the FeCoNiCuMn high entropy alloy catalyst in Examples 1-5 of the present invention.

[0025] Figure 2 These are TEM morphology images of the FeCoNiCuMn high entropy alloys under different conditions in Examples 1-5 of the present invention.

[0026] Figure 3 This is the XRD image of the FeCoNiCuMn high entropy alloy in Example 1 of the present invention.

[0027] Figure 4 These are polarization curves of the electrochemical tests of the FeCoNiCuMn high entropy alloys in Examples 1-5 of the present invention.

[0028] Figure 5 This is the electrochemical impedance curve of the FeCoNiCuMn high entropy alloy in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples. The three-dimensional porous copper foam substrate used in the present invention has a thickness of 1.0 mm, a pore diameter of 0.1 mm, a porosity of 98%, and a bulk density of 0.1-0.8 g cm -3 .

[0030] Example 1

[0031] A method for preparing a FeCoNiCuMn nano-high entropy alloy electrocatalyst comprises the following steps:

[0032] 1) Preliminary preparation for high entropy alloy preparation:

[0033] Cut the three-dimensional porous copper foam into 1x1cm 2 Wash the surface impurities and oxide layer of the copper foam in 1M dilute hydrochloric acid solution. Then remove the copper foam and rinse it with deionized water to remove the residual dilute hydrochloric acid solution to avoid affecting the subsequent deposition process. Then soak it in anhydrous ethanol for a while to prevent the cleaned copper foam from being oxidized again.

[0034] A 0.1 M mixed solution of ferrous sulfate, cobalt sulfate, nickel sulfate, copper sulfate, and manganese sulfate was added with 0.02 M citric acid, 0.65 M boric acid, and 0.085 M L-ascorbic acid and dissolved in deionized water to prepare a FeCoNiCuMn electrodeposition solution.

[0035] 2) Preparation of high entropy alloys:

[0036] The cleaned copper foam was placed as a cathode in the electrolyte for deposition, and high entropy alloy was prepared by electrodeposition at a voltage of 4 V and a temperature of 25°C for 10 minutes.

[0037] Application of catalytic water-to-oxygen desorption: The deposited catalyst was tested for its performance in catalytic water-to-oxygen desorption in a three-electrode system, with a platinum wire as the counter electrode, a high-entropy alloy as the working electrode, and a saturated calomel electrode as the reference electrode. The polarization curve was tested in a 1M KOH solution at a scan rate of 5 mV s. -1 , where all potentials are relative to the reversible hydrogen electrode.

[0038] from Figure 2(a) As can be seen from the TEM image, the prepared high entropy alloy particles are evenly loaded on the three-dimensional skeleton of the copper foam, and the diameter of the particles is about 10nm. The three-dimensional structure of the copper foam is interconnected, and the porous structure is conducive to improving the transmission rate of ions and oxygen during the catalytic process. Due to its own characteristics, the high entropy alloy has a relatively stable phase structure, which is conducive to improving the stability of the catalyst. The nano-sized high entropy alloy maximizes the contact area between the catalyst and the electrolyte, thereby providing abundant active sites. The polarization curve of the FeCoNiCuMn high entropy alloy is shown in Figure 2. Figure 4 From the figure we can see that at 100mA cm -2 The overpotential of the catalyst is 270 mV at a current density of 1.5 GHz, and it has good catalytic activity for oxygen evolution reaction.

[0039] Example 2

[0040] 1) The method for pretreatment of the copper foam is the same as that in Example 1.

[0041] 2) Preparation of high entropy alloys:

[0042] The cleaned copper foam was placed as a cathode in the electrolyte for deposition, and high entropy alloy was prepared by electrodeposition at a voltage of 6 V and a temperature of 25°C for 10 minutes.

[0043] Application of catalytic water-to-oxygen desorption: The deposited catalyst was tested for its performance in catalytic water-to-oxygen desorption in a three-electrode system, with a platinum wire as the counter electrode, a high-entropy alloy as the working electrode, and a saturated calomel electrode as the reference electrode. The polarization curve was tested in a 1M KOH solution at a scan rate of 5 mV s. -1 , where all potentials are relative to the reversible hydrogen electrode. Figure 2 (b) As can be seen from the TEM image, the prepared high entropy alloy particles are evenly loaded on the three-dimensional skeleton of the copper foam, and the diameter of the particles is about 10nm. The three-dimensional structure of the copper foam is interconnected, and the porous structure is conducive to improving the transmission rate of ions and oxygen during the catalytic process. Due to its own characteristics, the phase structure of the high entropy alloy is relatively stable, which is conducive to improving the stability of the catalyst. The nano-sized high entropy alloy maximizes the contact area between the catalyst and the electrolyte, thereby providing abundant active sites. As the voltage increases, the deposition rate accelerates, increasing the loading amount. At 100mA cm -2 An overpotential of 280 mV was achieved at a current density of 1.5 %.

[0044] Example 3

[0045] 1) The method for pretreatment of the copper foam is the same as that in Example 1.

[0046] 2) Preparation of high entropy alloys:

[0047] The cleaned copper foam was placed as a cathode in the electrolyte for deposition, and high entropy alloy was prepared by electrodeposition at a voltage of 8 V and a temperature of 25°C for 10 minutes.

[0048] Application of catalytic water-to-oxygen desorption: The deposited catalyst was tested for its performance in catalytic water-to-oxygen desorption in a three-electrode system, with a platinum wire as the counter electrode, a high-entropy alloy as the working electrode, and a saturated calomel electrode as the reference electrode. The polarization curve was tested in a 1M KOH solution at a scan rate of 5 mV s. -1 , where all potentials are relative to the reversible hydrogen electrode. Figure 2 (c) TEM image shows that the prepared high entropy alloy particles are evenly loaded on the three-dimensional skeleton of copper foam, with a particle diameter of 10nm. The three-dimensional structure of copper foam is interconnected, and the porous structure is conducive to improving the transmission rate of ions and oxygen during the catalytic process. Due to its own characteristics, the phase structure of high entropy alloy is relatively stable, which is conducive to improving the stability of the catalyst. The nano-sized high entropy alloy maximizes the contact area between the catalyst and the electrolyte, thereby providing abundant active sites. As the voltage increases, the overpotential increases. At 100mA cm -2 The current density reached 290mV.

[0049] Example 4

[0050] 1) The method for pretreatment of the copper foam is the same as that in Example 1.

[0051] 2) Preparation of high entropy alloys:

[0052] The cleaned copper foam was used as the cathode and placed in the electrolyte for deposition. High entropy alloy was deposited for 10 minutes at a voltage of 4 V and a temperature of -2°C.

[0053] Application of catalytic water decomposition to produce oxygen: The deposited catalyst was tested for its performance in catalytic water decomposition to produce oxygen in a three-electrode system, with a platinum wire as the counter electrode, a high-entropy alloy as the working electrode, and a saturated calomel electrode as the reference electrode. The polarization curve was tested in a 1M KOH solution at a scan rate of 5mV s. -1 , where all potentials are relative to the reversible hydrogen electrode.

[0054] from Figure 2(d) TEM images show that the prepared high-entropy alloy particles are uniformly loaded on the three-dimensional skeleton of the copper foam, with a particle diameter of 10 nm. The three-dimensional structure of the copper foam is interconnected, and the porous structure is conducive to improving the transmission rate of ions and oxygen during the catalytic process. Due to its inherent characteristics, the phase structure of the high-entropy alloy is relatively stable, which is conducive to improving the stability of the catalyst. The nano-sized high-entropy alloy maximizes the contact area between the catalyst and the electrolyte, thereby providing abundant active sites. An overpotential of 290 mV is required to achieve 100 mA cm -2 current density.

[0055] Example 5

[0056] 1) The method for pretreatment of the copper foam is the same as that in Example 1.

[0057] 2) Preparation of high entropy alloys:

[0058] The cleaned copper foam was used as the cathode to dilute the deposition solution to half of the original concentration and deposited at a voltage of 4 V and a temperature of 25°C for 10 minutes to prepare a high entropy alloy.

[0059] Application of catalytic water-to-oxygen desorption: The deposited catalyst was tested for its performance in catalytic water-to-oxygen desorption in a three-electrode system, with a platinum wire as the counter electrode, a high-entropy alloy as the working electrode, and a saturated calomel electrode as the reference electrode. The polarization curve was tested in a 1M KOH solution at a scan rate of 5 mV s. -1 , where all potentials are relative to the reversible hydrogen electrode. The prepared high-entropy alloy particles are uniformly loaded on the three-dimensional skeleton of copper foam, and the particle diameter is 10nm. The three-dimensional structure of copper foam is interconnected, and the porous structure is conducive to improving the transmission rate of ions and oxygen during the catalytic process. Due to its own characteristics, the phase structure of high-entropy alloy is relatively stable, which is conducive to improving the stability of the catalyst. The nano-sized high-entropy alloy maximizes the contact area between the catalyst and the electrolyte, thereby providing abundant active sites. As the solution concentration decreases, the overpotential increases to 300mV.

[0060] The various processing methods listed in the present invention can realize the present invention, and the upper and lower limit values and interval values of each technical parameter can realize the present invention, which will not be listed one by one here.

Claims

1. A method for preparing a nano alloy catalyst, wherein the catalyst is an electrocatalyst, characterized in that The electrocatalyst includes a three-dimensional porous copper foam substrate and FeCoNiCuMn high-entropy alloy nanoparticles supported on the three-dimensional porous copper foam substrate; the FeCoNiCuMn high-entropy alloy nanoparticles have a face-centered cubic crystal structure; wherein the atomic ratio of Fe:Co:Ni:Cu:Mn is 1:1:1:1:1; the electrocatalyst preparation method includes the following steps: (1) Preliminary preparation for high entropy alloy preparation: Cut the three-dimensional porous copper foam into 1x1cm 2 Wash the surface impurities and oxide layer of the copper foam in a 1M dilute hydrochloric acid solution, then take out the copper foam and rinse it with deionized water to remove the residual dilute hydrochloric acid solution to avoid affecting the subsequent deposition process, and then soak it in anhydrous ethanol for a while to prevent the cleaned copper foam from being oxidized again; A 0.1 M mixed solution of ferrous sulfate, cobalt sulfate, nickel sulfate, copper sulfate, and manganese sulfate was added with 0.02 M citric acid, 0.65 M boric acid, and 0.085 M L-ascorbic acid and dissolved in deionized water to prepare a FeCoNiCuMn electrodeposition solution; (2) Preparation of high entropy alloys: The cleaned copper foam was used as a cathode and deposited in an electrolyte. The electroplating was carried out at a voltage of 4 V and a temperature of -2°C for 10 minutes to obtain a high entropy alloy electrocatalyst.

2. The method for preparing a nano alloy catalyst according to claim 1, characterized in that The three-dimensional porous copper foam substrate has a thickness of 1.0 mm, a pore size of 0.1 mm, a porosity of 98%, and a bulk density of 0.1–0.8 g cm -3 .

3. The method for preparing a nano alloy catalyst according to claim 1, characterized in that The diameter of the FeCoNiCuMn high entropy alloy nanoparticles is 10 nm.

4. The method for preparing a nano alloy catalyst according to claim 1, wherein The electrocatalyst drives the oxygen evolution reaction in water electrolysis with an onset potential of 1.2 V vs RHE and a current density of 100 mA cm -2 The overpotential is 290mV.

5. Use of the electrocatalyst obtained by the preparation method according to any one of claims 1 to 4 in oxygen evolution by electrolysis of water.

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