A method for preparing a nano-high-entropy alloy bifunctional electrocatalyst and its application.

Abstract

This application discloses a method for preparing a bifunctional nano-high-entropy alloy electrocatalyst and its application. The preparation method includes: (a) dissolving a Ru-containing precursor and a transition metal salt precursor A in a solvent to form a mixed solution I, and then adding an organic ligand to obtain a co-mixed solution; (b) adding a binder to the co-mixed solution obtained in step (a) to undergo a solvothermal reaction to obtain the catalyst, wherein the transition metal salt precursor A includes at least four transition metal elements A, wherein the transition metal elements A do not include Ru. The catalyst prepared by this method has a diameter of 30-100 nm, can provide abundant catalytic reaction active sites, and exhibits excellent electrocatalytic performance for hydrogen evolution reaction and oxygen evolution reaction. Furthermore, this preparation method is not only simple in process and equipment, but also has good reproducibility and is highly promising for application.

Description

Technical Field

[0001] This application relates to a method for preparing a bifunctional electrocatalyst made of dual nano-high entropy alloy and its application as a bifunctional catalyst material in hydrogen evolution reaction and oxygen evolution reaction, belonging to the fields of inorganic catalyst synthesis and water electrolysis. Background Technology

[0002] Electrocatalytic water splitting is a highly efficient and feasible hydrogen fuel production technology for renewable energy and carbon neutrality. Especially under acidic conditions, the produced hydrogen can achieve an ultra-high purity of 99.995% due to the rapid kinetics and excellent energy efficiency. To date, numerous reports have explored advanced electrocatalysts for the hydrogen evolution reaction (HER). While these reported catalysts appear promising, they still do not meet the necessary requirements for practical use in acidic media. Furthermore, the water electrolysis process requires catalysts to possess excellent HER and OER activities simultaneously. Therefore, finding other types of high-performance, sufficiently advanced HER and OER catalysts remains a major challenge in scientific research.

[0003] High entropy alloys (HEAs) are solid solutions formed by mixing five or more metallic elements in equimolar or near-equimolar ratios. Due to their unique and superior physicochemical properties, they have shown great application potential in many fields, becoming one of the most sought-after materials. HEAs possess tunable composition, electronic structure, inherent synergistic effects, severe lattice distortion, and abundant catalytic active sites, fully meeting the requirements for becoming advanced electrocatalysts. Currently, although there are many methods for preparing high entropy alloys, such as vacuum melting, powder metallurgy, mechanical alloying, molten salt electrodeposition, and carbothermal shock, they all require expensive specialized equipment and complex processes. Therefore, developing novel synthesis processes that are low-cost and simple is particularly important. Summary of the Invention

[0004] The purpose of this invention is to propose a method for preparing a nano-high entropy alloy bifunctional electrocatalyst. This method uses a simple one-step solvothermal method to prepare the nano-high entropy alloy bifunctional electrocatalyst, thereby solving the problems of existing high entropy alloy preparation methods, such as high equipment requirements, high energy consumption, complex and lengthy process flow, and large particle size.

[0005] According to one aspect of this application, a method for preparing a nano-high-entropy alloy electrocatalyst is provided, comprising the following steps:

[0006] (a) Dissolve the Ru-containing precursor and the transition metal salt precursor A in a solvent to form a mixed solution I, and then add an organic ligand to obtain a co-mixed solution;

[0007] (b) Add a binder to the co-mixed solution described in step (a) and allow a solvothermal reaction to occur to obtain the catalyst;

[0008] The transition metal salt precursor A includes at least four transition metal elements A, wherein the transition metal elements A do not include Ru.

[0009] Optionally, step (b) further includes:

[0010] The substrate is immersed in the co-mixed solution of step (a), and then a binder is added to undergo a solvothermal reaction to obtain the catalyst.

[0011] Optionally, the Ru-containing precursor is RuCl3.

[0012] The transition metal salt precursor A is selected from any one of transition metal chlorides and transition metal nitrates;

[0013] Preferably, the transition metal element A is selected from at least four of Fe, Co, Ni, Cu, Mn, Mo, W, and Bi.

[0014] Optionally, the solvent includes organic solvent A and organic solvent B, wherein the volume ratio of organic solvent A to organic solvent B is 30-35:2-6.

[0015] Optionally, the volume ratio of organic solvent A to organic solvent B is selected from any ratio of 30:2, 31:3, 33:4, 34:5, 35:6 or a range between any two ratios.

[0016] Optionally, the volume ratio of the organic solvent A to the molar ratio of the organic ligand is 30–35 ml: 2.5–3.5 mmol.

[0017] Optionally, the volume ratio of the organic solvent A to the molar ratio of the organic ligand is selected from any ratio or a range between any two of the following: 30 ml: 2.5 mmol, 32 ml: 2.75 mmol, 33 ml: 3 mmol, 34 ml: 3.25 mmol, and 35 ml: 3.5 mmol.

[0018] Optionally, the volume ratio of the organic solvent A to the adhesive is 30-35:2-3.

[0019] Optionally, the volume ratio of the organic solvent A to the adhesive is any ratio or a range between any two ratios from 30:2, 32:2.25, 33:2.5, 34:2.75, and 35:3.

[0020] Optionally, in the mixture I, the concentration of the Ru-containing precursor is 5–15 mmol / L, where the concentration is expressed as the molar number of Ru.

[0021] Optionally, in the mixture I, the concentration of the Ru-containing precursor is any value among 5 mmol / L, 8 mmol / L, 10 mmol / L, 13 mmol / L, and 15 mmol / L, or a range between any two values.

[0022] Optionally, in the mixture I, the molar ratio of the Ru-containing precursor to the transition metal salt precursor A is 0.2-0.6:0.2-0.8, wherein the Ru-containing precursor is calculated in molar amounts of Ru, and the transition metal salt precursor A is calculated in molar amounts of transition metal A.

[0023] Optionally, in the mixture I, the molar ratio of the Ru-containing precursor to the transition metal salt precursor A is any ratio or a range between two ratios, which is 0.2:0.8, 0.3:0.5, 0.5:0.5, or 0.6:0.2.

[0024] Optionally, the metal element components in the co-mixed solution are approximately in equimolar ratio.

[0025] Optionally, the organic solvent A is selected from at least one of N,N-dimethylformamide, ethylene glycol, and dimethylacetamide; and the organic solvent B is ethanol.

[0026] Optionally, the organic ligand is selected from at least one of pyromellitic acid, sodium gluconate, sodium citrate, and 1,4-terephthalic acid; wherein the function of the organic ligand is to use its multifunctional group to complex different metal ions with different physicochemical properties together.

[0027] The adhesive is triethylamine.

[0028] Optionally, the reaction temperature of the solvothermal reaction is 130–160°C; the reaction time of the solvothermal reaction is 30–48 h.

[0029] Optionally, the reaction temperature of the solvothermal reaction is selected from any value or a range between any two of 130°C, 140°C, 145°C, 150°C, and 160°C.

[0030] Optionally, the reaction time of the solvothermal reaction is selected from any value of 30h, 35h, 40h, 43h, and 48h, or a range between any two values.

[0031] Optionally, the substrate is selected from one of porous foamed titanium, titanium mesh, titanium sheet, porous foamed nickel, and carbon cloth.

[0032] The pretreatment process of the porous foam titanium, titanium mesh, titanium sheet, porous foam nickel and other substrates requires ultrasonic treatment with acetone and anhydrous ethanol for 5 minutes, ultrasonic treatment with dilute hydrochloric acid with a mass fraction of 1 mol / L for 15 minutes, and finally rinsing with deionized water for 5 minutes and drying.

[0033] The carbon cloth needs to be treated in a 70°C oil bath in 0.5M H2SO4 for 1 hour, then in a 80°C oil bath in 30% H2O2 for 1 hour, and finally washed with deionized water and dried.

[0034] The substrate serves two purposes: firstly, it provides a reaction site for the nucleation of high-entropy alloy particles while preventing their aggregation; secondly, a conductive substrate facilitates efficient mass transfer, good electronic conductivity, and good physical contact between the high-entropy alloy nanoparticles and the electrodes.

[0035] In another aspect of this application, a nano-high-entropy alloy bifunctional electrocatalyst was prepared according to the above preparation method, comprising a substrate and high-entropy alloy particles grown in situ on the surface of the substrate; the nano-high-entropy alloy particles have a diameter of 30-100 nm, a face-centered cubic (fcc) crystal structure, and a space group of Pm6; the metal elements in the high-entropy alloy particles are selected from at least four of Fe, Co, Ni, Cu, Mn, Mo, W, and Bi, and Ru.

[0036] In another aspect of this application, a bifunctional hydrogen evolution and oxygen evolution material is provided, comprising the catalyst described above.

[0037] The application of the bifunctional hydrogen and oxygen evolution material in the hydrogen evolution reaction, wherein the bifunctional hydrogen and oxygen evolution material achieves 10 mA cm⁻¹ in a solution containing 0.5 M H₂SO₄. -2 The required overpotential at the current density is 40–100 mV, and the Tafel slope is 30–120 mV dec. -1 .

[0038] The bifunctional hydrogen and oxygen evolution material is used in the oxygen evolution reaction. The bifunctional hydrogen and oxygen evolution material achieves a velocity of 10 mA cm⁻¹ in a solution containing 1M KOH. -2 The required overpotential at the current density is 250–400 mV, and the Tafel slope is 40–120 mV dec. -1 .

[0039] The beneficial effects that this application can produce include:

[0040] 1) This application employs a one-step solvothermal method to directly prepare electrocatalysts containing high-entropy alloy nanoparticles. The method is simple, easy to implement, has good reproducibility, and is low in cost. Although there are many reported methods for preparing high-entropy alloys, such as vacuum melting, powder metallurgy, mechanical alloying, molten salt electrodeposition, and carbon thermal shock, few of them have simple processes, are easy to operate, have low cost, and require relatively low equipment requirements. Developing new high-entropy alloy synthesis processes is particularly important, and this invention provides a new approach for the synthesis of high-entropy materials.

[0041] 2) The high-entropy alloy nanoparticles in this application mainly select low-cost non-precious metal elements such as Fe, Co, Ni, Cu, Mn, Mo, W, and Bi, and contain only a small amount of precious metal Ru. Compared with commercial materials such as platinum carbon, ruthenium oxide, and yttrium oxide, they have a price advantage.

[0042] 3) The high-entropy alloy of this application exhibits lattice distortion, diffusion and hysteresis effects, and high-entropy effects. The composition of each metal element tends to be randomly and uniformly distributed. Furthermore, the high-entropy alloy nanoparticles prepared in this experiment can be uniformly loaded and dispersed on numerous types of conductive substrates, thereby enabling the formation and exposure of a large number of catalytically active sites. Therefore, by adjusting the composition and content of each metal element, the high-entropy alloy catalyst can exhibit excellent catalytic performance in electrocatalytic reactions such as hydrogen evolution reaction, oxygen evolution reaction, carbon dioxide reduction reaction, oxygen reduction reaction, small molecule oxidation reaction, and nitrogen reduction reaction.

[0043] 4) The FeNiCuWRu-based catalyst prepared in this application undergoes a hydrogen evolution reaction in a solution containing 0.5 M H2SO4, reaching 10 mA cm⁻¹. -2 At current density, only an overpotential of 49 mV is required; in a solution containing 1 M KOH, the oxygen evolution reaction reaches 10 mA cm⁻¹. -2 The required overpotential at the current density is only 267mV. Attached Figure Description

[0044] Figure 1 The X-ray powder diffraction (XRD) patterns of the catalyst materials prepared in Examples 1 and 2 of this application are shown.

[0045] Figure 2 This is a scanning electron microscope (SEM) image of the catalyst material prepared in Example 1 of this application.

[0046] Figure 3 This is a scanning electron microscope (SEM) image of the catalyst material prepared in Example 2 of this application.

[0047] Figure 4 This is a transmission electron microscopy (TEM) scan of the elemental distribution of the catalyst material prepared in Example 2 of this application.

[0048] Figure 5 This is a scanning electron microscope (SEM) image of porous nickel foam loaded with FeNiCuWRu nanoparticles in Example 3 of this application.

[0049] Figure 6 This is a scanning electron microscope (SEM) image of foam titanium loaded with FeNiCuWRu nanoparticles in Example 3 of this application.

[0050] Figure 7 The linear sweep voltammetry (LSV) curve of the FeNiCuWRu high-entropy alloy catalyst loaded on a foamed titanium substrate obtained in Example 3 of this application during the hydrogen evolution reaction.

[0051] Figure 8 The linear sweep voltammetry (LSV) curve of the FeNiCuWRu high-entropy alloy catalyst loaded on a porous nickel foam substrate obtained in Example 3 of this application during the oxygen evolution reaction.

[0052] Figure 9 The image shows the X-ray powder diffraction (XRD) pattern of the FeNiCuMoRu catalyst material prepared in Example 4 of this application. Detailed Implementation

[0053] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0054] Unless otherwise specified, the raw materials and reagents used in the embodiments of this application were purchased commercially and used directly without processing.

[0055] In this embodiment, the electrochemical performance of the samples was tested using a CHI660E electrochemical workstation from Shanghai Chenhua Company.

[0056] X-ray powder diffraction (XRD) of the sample was performed on an X-ray powder diffractometer (Miniflex 600) using Cu Kα radiation. (15mA, 40kV) test.

[0057] The morphology and structure of the samples were characterized using scanning electron microscopy (SEM, Hitachi SU-8010) and transmission electron microscopy (TEM, TECNAIG2 F20).

[0058] Example 1: Preparation of FeNiCuWRu nano-high-entropy alloy bifunctional electrocatalyst

[0059] (1) Weigh 0.5 mmol FeCl3·6H2O, 0.5 mmol NiCl2·6H2O, 0.5 mmol CuCl2·2H2O, 0.5 mmol WCl6, and 0.5 mmol RuCl3 and dissolve them in a mixture of 32 ml DMF and 4 ml anhydrous ethanol.

[0060] (2) After completely dissolving the mixed solution obtained in step (1), add 2.5 mmol of pyromellitic acid, stir electromagnetically for 12 h to obtain a co-mixed solution, then add 3 ml of triethylamine and disperse by ultrasonication.

[0061] (3) Transfer the mixed solution obtained in step (2) into a 50ml polytetrafluoroethylene reactor liner, put it into a stainless steel reactor sleeve, place it in an oven, and keep it at 130℃ for 40h.

[0062] (4) Collect the solution after the reaction in step (3), centrifuge it with anhydrous ethanol at 10300 rpm 3 to 4 times, and dry it under vacuum at 60°C to finally obtain the nano high entropy alloy bifunctional electrocatalyst.

[0063] The X-ray powder diffraction pattern of the prepared high-entropy alloy is as follows: Figure 1 As shown by curve a, the morphology and structure of the high-entropy alloy are as follows: Figure 2 As shown.

[0064] Figure 1 XRD results from the a-curve show that the alloy in the catalyst has a face-centered cubic (fcc) crystal structure, with space group Pm(6), indicating a monoclinic crystal system. The high-entropy alloy exists as a single-phase solid solution, exhibiting a relatively stable phase structure, which is beneficial for improving the catalyst's stability. Figure 2 SEM results show that the synthesized catalyst is nearly spherical with a diameter of about 60 nm. The number of catalytic active sites in the nanoscale catalyst is greatly increased, which is beneficial to improving the catalyst's performance.

[0065] Example 2: Preparation of FeNiCuWRu nano-high-entropy alloy bifunctional catalyst

[0066] (1) Weigh 0.5 mmol FeCl3·6H2O, 0.5 mmol NiCl2·6H2O, 0.25 mmol CuCl2·2H2O, 0.75 mmol WCl6, and 0.5 mmol RuCl3 and dissolve them in a mixture of 32 ml DMF and 4 ml anhydrous ethanol.

[0067] (2) After completely dissolving the mixed solution obtained in step (1), add 2.5 mmol of pyromellitic acid, stir electromagnetically for 12 h to obtain a co-mixed solution, then add 3 ml of triethylamine and disperse by ultrasonication.

[0068] (3) Transfer the mixed solution obtained in step (2) into a 50ml polytetrafluoroethylene reactor liner, put it into a stainless steel reactor sleeve, place it in an oven, and keep it at 130℃ for 40h.

[0069] (4) Collect the solution after the reaction in step (3), centrifuge it with anhydrous ethanol at 10300 rpm 3 to 4 times, and dry it under vacuum at 60°C to finally collect the high entropy alloy powder.

[0070] The X-ray powder diffraction pattern of the prepared high-entropy alloy is as follows: Figure 1 As shown in the b-curve, the morphology and structure of the high-entropy alloy are as follows: Figure 3 As shown, the elemental distribution of the high-entropy alloy is as follows: Figure 4 As shown.

[0071] Figure 1 The XRD results from the b-curve show that appropriately changing the content of each metal element does not significantly alter the alloy's crystal structure, and the single-phase solid solution structure is well preserved. Figure 3 Spherical nanoparticles, approximately 50 nm in size, can be seen cross-linked together. From... Figure 4 Elemental surface scans show that Fe, Ni, Cu, W, and Ru are uniformly distributed within the high-entropy alloy nanoparticles. These results confirm the successful preparation of the FeNiCuWRu nano-high-entropy alloy catalyst.

[0072] Example 3: Preparation of FeNiCuWRu high-entropy alloy nanoparticle catalysts grown in situ on porous nickel foam and titanium foam

[0073] (1) Cut porous nickel foam and titanium foam into 2cm*2cm size, then sonicate them with acetone and anhydrous ethanol for 5 minutes, sonicate them with dilute hydrochloric acid with a mass fraction of 1mol / L for 15 minutes, and finally wash them with deionized water for 5 minutes and dry them for use.

[0074] (2) The FeNiCuWRu high-entropy alloy is prepared using the same method as in Example 2, but the treated porous nickel foam or titanium foam needs to be added in step (3) of Example 2.

[0075] Scanning electron microscope (SEM) images of porous nickel foam and titanium foam loaded with FeNiCuWRu nanoparticles are shown below. Figure 5 , 6 As shown.

[0076] from Figure 5 , 6As can be seen, the catalyst is uniformly dispersed on the porous nickel foam and titanium foam conductive substrate, and the nanoparticles are cross-linked together. The good physical contact between the catalyst and the electrode, as well as the efficient mass transfer and good electronic conductivity, greatly enhance the catalytic performance.

[0077] Example 4: Preparation of FeNiCuMoRu High-Entropy Alloy Nanoparticle Catalyst

[0078] (1) Weigh 0.5 mmol FeCl3·6H2O, 0.5 mmol NiCl2·6H2O, 0.5 mmol CuCl2·2H2O, 0.5 mmol MoCl5, and 0.5 mmol RuCl3 and dissolve them in a mixture of 32 ml DMF and 4 ml anhydrous ethanol.

[0079] (2) After completely dissolving the mixed solution obtained in step (1), add 2.5 mmol of 1,4-terephthalic acid, stir electromagnetically for 12 h to obtain a co-mixed solution, then add 3 ml of triethylamine and disperse by ultrasonication.

[0080] (3) Transfer the mixed solution obtained in step (2) into a 50ml polytetrafluoroethylene reactor liner, put it into a stainless steel reactor sleeve, place it in an oven, and keep it at 140℃ for 48h.

[0081] (4) Collect the solution after the reaction in step (3), centrifuge it with anhydrous ethanol at 10,000 rpm 3 to 4 times, and dry it under vacuum at 60°C to finally collect the high entropy alloy powder.

[0082] The X-ray powder diffraction pattern of the prepared high-entropy alloy is as follows: Figure 9 As shown. From Figure 9 It can be seen that the crystal structure of the FeNiCuMoRu nano high-entropy alloy catalyst is face-centered cubic (fcc) structure, indicating that a single-phase solid solution has been formed.

[0083] Application example: FeNiCuWRu nano-high-entropy alloy catalysts are used in hydrogen evolution and oxygen evolution electrode reactions.

[0084] A foam titanium electrode with in-situ grown FeNiCuWRu nano-high-entropy alloy was cut to a size of 1cm*2cm. A three-electrode system was constructed using this electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 0.5M H₂SO₄. The linear sweep voltammetry curve for hydrogen evolution testing of this electrode in the above electrolyte is shown below. Figure 7 As shown in the figure. It can be seen from the figure that when the current density reaches 10 mA cm⁻¹... -2The overpotential required for hydrogen evolution is 49 mV, comparable to that of commercial platinum-carbon alloys. A porous nickel foam electrode with in-situ grown FeNiCuWRu nano-high entropy alloy was cut to a size of 1 cm * 2 cm. A three-electrode system was constructed using this electrode as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 1 M KOH. The linear sweep voltammetry curve for oxygen evolution testing of this electrode in the above electrolyte is shown below. Figure 8 As shown in the figure. It can be seen from the figure that when the current density reaches 10 mA cm⁻¹... -2 The overpotential required for hydrogen evolution is 267mV, and its catalytic performance is superior to that of commercial ruthenium oxide.

[0085] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a nano-high-entropy alloy bifunctional electrocatalyst, characterized in that, Includes the following steps: (a) A Ru-containing precursor and a transition metal salt precursor A are dissolved in a solvent to form a mixture I, and then an organic ligand is added to obtain a co-mixed solution; wherein the solvent includes organic solvent A and ethanol, and the volume ratio of organic solvent A to ethanol is 30~35:2~6; the organic solvent A is selected from at least one of N,N-dimethylformamide, ethylene glycol, and dimethylacetamide; the organic ligand is selected from at least one of trimellitic acid, sodium gluconate, sodium citrate, and 1,4-terephthalic acid; (b) Triethylamine is added to the co-mixed solution described in step (a) to undergo a solvothermal reaction, thereby obtaining the catalyst; The transition metal salt precursor A includes at least four transition metal elements A, wherein the transition metal elements A do not include Ru.

2. The preparation method according to claim 1, characterized in that, Step (b) further includes: immersing the substrate in the co-mixed solution of step (a), then adding triethylamine to undergo a solvothermal reaction to obtain the catalyst.

3. The preparation method according to claim 1, characterized in that, The Ru-containing precursor is RuCl3; The transition metal salt precursor A is selected from any one of transition metal chlorides and transition metal nitrates; The transition metal element A is selected from at least four of the following: Fe, Co, Ni, Cu, Mn, Mo, W, and Bi.

4. The preparation method according to claim 1, characterized in that, The volume ratio of organic solvent A to organic ligand is 30-35 ml: 2.5-3.5 mmol; The volume ratio of the organic solvent A to triethylamine is 30~35:2~3; In the mixture I, the concentration of the Ru-containing precursor is 5~15 mmol / L, where the concentration is expressed as the molar number of Ru. In the mixture I, the molar ratio of the Ru-containing precursor to the transition metal salt precursor A is 0.2~0.6:0.2~0.8, wherein the Ru-containing precursor is calculated in molar amounts of Ru, and the transition metal salt precursor A is calculated in molar amounts of transition metal A.

5. The preparation method according to claim 1, characterized in that, The reaction temperature of the solvothermal reaction is 130~160℃; the reaction time of the solvothermal reaction is 30~48h.

6. The preparation method according to claim 2, characterized in that, The substrate is selected from one of porous foamed titanium, titanium mesh, titanium sheet, porous foamed nickel, and carbon cloth.

7. A bifunctional hydrogen and oxygen evolution material, characterized in that, The bifunctional hydrogen evolution and oxygen evolution materials include catalysts prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the bifunctional hydrogen evolution and oxygen evolution material according to claim 7, characterized in that, It is applied to the hydrogen evolution reaction or oxygen evolution reaction. In the hydrogen evolution reaction, the bifunctional hydrogen and oxygen evolution material reaches 10 mA·cm⁻¹ in a solution containing 0.5 M H₂SO₄. -2 The required overpotential at current density is 40–100 mV, and the Tafel slope is 30–120 mV·dec. -1 ; In the oxygen evolution reaction, the bifunctional hydrogen and oxygen evolution material reaches 10 mA·cm⁻¹ in a solution containing 1 M KOH. -2 The required overpotential at the current density is 250~400 mV, and the Tafel slope is 40~120 mV·dec. -1 .

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