High-entropy intermetallic compound bifunctional catalyst and preparation method and application thereof

Abstract

The application provides a high-entropy intermetallic compound bifunctional catalyst and a preparation method and application thereof, and belongs to the technical field of energy materials. The high-entropy intermetallic compound bifunctional catalyst is prepared by combining a wet chemical synthesis method with a controllable annealing process. The catalyst has carbon-supported platinum-cobalt-copper-tungsten-molybdenum quinary high-entropy alloy nanoparticles. The alloy nanoparticles have high-entropy effect and ordered structure at the same time. The particle size is 4-7 nm, and the molar ratio of metal atoms is platinum: cobalt: copper: tungsten: molybdenum = 4: (1.75-2.5): (1.75-2.5): (0.01-0.5): (0.01-0.5). The platinum loading in the catalyst is 20-70 wt%, and the catalyst is used for catalyzing oxygen reduction reaction in a cathode of a hydrogen fuel cell and / or catalyzing methanol oxidation reaction in an anode of a direct methanol fuel cell. The half-wave potential of the catalyst in an acidic medium is more than 30 mV higher than that of a commercial Pt / C catalyst, and the methanol oxidation peak current density is 1.4-2.5 times that of a commercial Pt / C catalyst or a commercial PtRu / C catalyst.

Description

High-entropy intermetallic compound bifunctional catalysts, their preparation methods and applications Technical Field

[0001] This invention relates to the field of energy materials technology, specifically to a high-entropy intermetallic compound bifunctional catalyst, its preparation method, and its application. Background Technology

[0002] With the rapid development of proton exchange membrane fuel cells, traditional platinum-based catalysts have revealed the following defects: The adsorption of oxygen-containing intermediates (*O / *OH) by a single platinum (Pt) active site is too strong, leading to sluggish ORR kinetics and requiring further improvement in ORR catalytic performance; metal dissolution easily occurs under acidic conditions, causing nanoparticle aggregation and affecting catalyst stability and lifespan; CO intermediate poisoning during methanol oxidation severely impacts catalyst stability, preventing traditional platinum-based catalysts from simultaneously achieving high ORR selectivity and methanol poisoning resistance. Improving traditional platinum-based catalysts to overcome these defects is the core challenge in enhancing energy conversion efficiency.

[0003] In existing technologies, some researchers utilize binary / ternary Pt-M (M = Fe, Co, Ni, etc.) alloys to regulate the electronic structure to address the aforementioned problems. However, this approach offers limited improvement in catalyst activity because the regulatory dimensions of the binary / ternary element combination are relatively singular (e.g., only electronic or strain effects). Chinese Patent CN119481112A discloses a defect-rich nitrogen-doped carbon-supported platinum-cobalt intermetallic compound, its preparation method, and its application. First, a two-dimensional leaf-like ZIF is used as a precursor. After high-temperature calcination in the presence of a mixed molten salt of KCl and NH4Cl, a nitrogen-doped carbon material is obtained. Then, NH3 heat treatment is used to remove pyrrole nitrogen and pyridine nitrogen from the nitrogen-doped carbon material, forming topological defect active sites. Finally, a defect-rich nitrogen-doped carbon-supported PtCo intermetallic compound catalyst is formed through gas-phase reduction. The topological defects of the carbon support can anchor the platinum-cobalt alloy, thereby inhibiting the aggregation of nanoparticles during high-temperature synthesis to improve activity. It can also inhibit the aggregation and dissolution of nanoparticles during electrochemical reactions, improving durability. However, its preparation process requires high-temperature and long-term annealing, the synthesis conditions are quite harsh, and it is easy to cause element volatilization and particle coarsening, making it difficult to prepare on a large scale for the time being.

[0004] Chinese Patent CN119524874A discloses a hydrophilic carbon-based modified high-entropy alloy electrolytic hydrogen production catalyst for water electrolysis, its preparation method, and its application. The method involves adding a hydrophilic carbon-based material and a mixed metal salt (platinum, palladium, cobalt, nickel, and copper) to an ethylene glycol solution and mixing them thoroughly to obtain a reaction solution. This reaction solution is then slowly added to an ethylene glycol solution at 200-240°C and heated for 0.5-2 hours to obtain the hydrophilic carbon-based modified high-entropy alloy electrolytic hydrogen production catalyst. This hydrogen production catalyst exhibits high activity, producing smaller hydrogen bubbles that detach more easily from the electrode surface. However, its internal alloy is a disordered solid solution structure with randomly arranged surface atoms, resulting in uneven distribution of active sites. Furthermore, HEAs prepared by traditional mechanical alloying or sputtering methods suffer from compositional segregation and low specific surface area, making it difficult to meet the performance requirements of nanoscale electrocatalysts.

[0005] In view of this, it is necessary to design a high-entropy intermetallic compound bifunctional catalyst, its preparation method and application, in order to solve the above problems. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a high-entropy intermetallic compound bifunctional catalyst, its preparation method and application, aiming to solve the technical problems of excessive adsorption of oxygen-containing intermediates (*O / *OH) by the single platinum (Pt) active site of traditional platinum-based catalysts, easy metal dissolution under acidic conditions, and inability to simultaneously achieve high ORR selectivity and anti-methanol poisoning characteristics.

[0007] This application yields a carbon-supported pentagonal (Pt-Co-Cu-W-Mo) high-entropy intermetallic bifunctional catalyst. The unique high-entropy alloy combination of platinum (Pt), cobalt (Co), copper (Cu), tungsten (W), and molybdenum (Mo) enhances the catalyst's activity and durability. By combining wet chemical synthesis with controlled annealing, the catalyst simultaneously possesses both high-entropy effects and an ordered structure. The lattice distortion and dynamic reconstruction of multiple active sites induced by the high-entropy effect endow the material with both the stability of the alloy structure and the wide-range catalytic adaptability of a multi-element alloy, thus achieving a balance between the catalyst's activity and durability in oxygen reduction and methanol oxidation.

[0008] In a first aspect, embodiments of this application provide a high-entropy intermetallic compound bifunctional catalyst, wherein the high-entropy intermetallic compound bifunctional catalyst comprises carbon-supported platinum-cobalt-copper-tungsten-molybdenum pentagonal high-entropy alloy nanoparticles; the pentagonal high-entropy alloy nanoparticles simultaneously possess high-entropy effect and ordered structure, with a particle size of 4-7 nm, and the molar ratio of metal atoms contained in the pentagonal high-entropy alloy nanoparticles being platinum:cobalt:copper:tungsten:molybdenum = 4:(1.75-2.5):(1.75-2.5):(0.01-0.5):(0.01-0.5); the platinum loading in the high-entropy intermetallic compound bifunctional catalyst is 20-70 wt%; the high-entropy intermetallic compound bifunctional catalyst is used for oxygen reduction reaction catalysis at the cathode in a hydrogen fuel cell and / or methanol oxidation reaction catalysis at the anode in a direct methanol fuel cell.

[0009] Furthermore, the high-entropy intermetallic compound bifunctional catalyst exhibits a half-wave potential in acidic media that exceeds that of commercial Pt / C catalysts by 30 mV or more, and its peak current density for methanol oxidation is 1.4-2.5 times that of commercial Pt / C or PtRu / C catalysts.

[0010] Furthermore, the high-entropy intermetallic compound bifunctional catalyst is prepared by first uniformly dispersing chloroplatinic acid, cobalt chloride, copper chloride, hexacarbonyltungsten, and hexacarbonylmolybdenum in a mixed solution on a nano-carbon support, then placing it in a reaction vessel, reacting it under alkaline conditions, and finally annealing it in a reducing atmosphere.

[0011] Secondly, embodiments of this application provide a method for preparing a high-entropy intermetallic compound bifunctional catalyst, comprising the following steps:

[0012] S1. The nano-carbon support is ultrasonically dispersed evenly in a solvent to obtain a mixed solution. Then, chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl are added to the mixed solution. The pH is adjusted to 10-12 by adding an alkaline solution. The mixture is ultrasonically dispersed again and stirred to obtain a suspension.

[0013] S2, the suspension obtained in step S1 is placed in a reaction vessel to react, and a black colloidal solution is obtained. After filtration, washing, and drying, a black powder is obtained.

[0014] S3. The black powder obtained in step S2 is ground and placed in a tube furnace for annealing under a reducing atmosphere to obtain a high-entropy intermetallic compound bifunctional catalyst.

[0015] Furthermore, the solvent used in step S1 is glycerol, isopropanol, ethylene glycol, or DMF. Chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl, and molybdenum hexacarbonyl are all dissolved in the solvent separately before being added to the mixed solution. Specifically, tungsten hexacarbonyl and molybdenum hexacarbonyl are dissolved in DMF, with the concentration of tungsten hexacarbonyl being 0.2-1.2 mg / mL and the concentration of molybdenum hexacarbonyl being 0.5-1.5 mg / mL. Chloroplatinic acid, cobalt chloride, and copper chloride are dissolved in glycerol, isopropanol, or ethylene glycol, wherein the concentration of chloroplatinic acid is 0.05-0.2 mol / L, the concentration of cobalt chloride is 0.05-0.3 mol / L, and the concentration of copper chloride is 0.05-0.3 mol / L.

[0016] Furthermore, in step S1, the molar ratio of metal atoms contained in chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl is Pt:Co:Cu:W:Mo=4:(1.75-2.5):(1.75-2.5):(0.01-0.5):(0.01-0.5).

[0017] Furthermore, in step S1, the nano-carbon support is acidified graphitized carbon black, KJ600, KJ300, or BP2000; the concentration of the nano-carbon support in the mixed solution is 0.5-1 mg / mL, and the alkaline solution refers to a 1 mol / L sodium hydroxide aqueous solution; in step S1, the ultrasonic time is greater than or equal to 15 min, and the stirring time is greater than or equal to 10 min.

[0018] Furthermore, in step S2, the suspension is placed in a reaction vessel and reacted at 130-220°C for 0.5-5 hours to obtain the black colloidal solution; the filtration method is vacuum filtration or pressure filtration; the drying temperature is 60-85°C and the drying time is 2-12 hours.

[0019] Furthermore, in step S3, the heating rate of the annealing treatment is 2-10℃ / min, the annealing temperature is 800-1000℃, and the annealing time is 0.5-3h; the reducing atmosphere is hydrogen or a hydrogen-argon mixture.

[0020] Thirdly, embodiments of this application provide an application of a high-entropy intermetallic compound bifunctional catalyst, which is used for catalysis of oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalysis of methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0021] The beneficial effects of this application are as follows:

[0022] This application combines wet chemical synthesis with controlled annealing to prepare a carbon-supported pentagonal high-entropy intermetallic compound bifunctional catalyst.

[0023] (1) This application utilizes the high-entropy effect generated by the platinum (Pt)-cobalt (Co)-copper (Cu)-tungsten (W)-molybdenum (Mo) pentagonal system to suppress elemental segregation, grain coarsening, and phase separation by maximizing configurational entropy, thereby inhibiting elemental segregation and grain boundary migration, delaying catalyst corrosion or agglomeration in acidic environments, and improving structural stability. The unique high-entropy alloy combination of Pt-Co-Cu-W-Mo also enhances the activity and durability of the catalyst. Among them, platinum provides the basic catalytic active sites, cobalt optimizes the electronic structure to weaken the adsorption of oxygen intermediates (such as CO, CH3O), and copper works together with platinum and cobalt to form more effective active sites, improving the activity and selectivity of ORR. The introduction of copper also induces strain in the platinum lattice, thereby changing the distance and arrangement between platinum atoms and promoting charge transport. Tungsten and molybdenum jointly construct a corrosion-resistant oxide layer (such as WO3, MoO3), which can adsorb OH in MOR. - This process accelerates the oxidation of CO to CO2, providing resistance to poisoning. It also enhances the hydrophilicity of the catalyst surface, promoting the contact between methanol and water, increasing mass transfer efficiency, and thus improving catalyst stability and resistance to CO poisoning. In this way, the multi-element system forms a gradient electronic coupling effect in the ordered lattice. Specifically, the Pt-Co-Cu ternary synergy on the lattice surface significantly enhances the methanol oxidation resistance to poisoning, while the W / Mo subsurface oxide network effectively inhibits acidic medium corrosion, improves resistance to poisoning, and enhances mass transfer efficiency, resulting in simultaneous improvements in catalyst performance in both ORR and MOR.

[0024] (2) This application combines wet chemical synthesis with controlled annealing, enabling the catalyst to possess both high entropy effect and ordered structure. The high entropy effect induces lattice distortion and dynamic reconstruction of multiple active sites, allowing the material to combine the stability of an alloy structure with the broad-range catalytic adaptability of a multi-element alloy, thus achieving a balance between the catalyst's activity and durability in oxygen reduction and methanol oxidation. This application utilizes the high entropy effect to form a single solid solution structure, enabling the dynamic reconstruction of surface / near-surface elements in the five-element high entropy alloy nanoparticles to form gradient active sites. Simultaneously, the lattice distortion within the nanoparticles generates a strain-electronic synergistic effect. The gradient active sites, strain-electronic synergistic effect, and multi-element redox interaction collectively broaden the catalyst's potential response window, which is beneficial for increasing energy density or adapting to different reaction requirements in electrocatalysis.

[0025] (3) The preparation method provided in this application has a short operation process, can be mass-produced, and is suitable for industrial production. The catalyst provided in this application is used for the oxygen reduction reaction catalysis at the cathode in hydrogen fuel cells and / or the methanol oxidation reaction catalysis at the anode in direct methanol fuel cells. It has high electrocatalytic activity and good durability. The half-wave potential in acidic media exceeds that of commercial Pt / C catalysts by 30mV and above, and the peak current density of methanol oxidation is 1.4-2.5 times that of commercial Pt / C catalysts or commercial PtRu / C catalysts.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0028] Figure 1 is the XRD pattern of the high-entropy intermetallic compound bifunctional catalyst provided in Example 1 of this application;

[0029] Figure 2 shows the SEM image and EDS mapping test image of the high-entropy intermetallic compound bifunctional catalyst provided in Example 1 of this application;

[0030] Figure 3 is a TEM image of the high-entropy intermetallic compound bifunctional catalyst provided in Example 1 of this application;

[0031] Figure 4 is a comparison of the rotating disk polarization curves (after iR compensation) of the commercial Pt / C catalyst, the catalysts provided in Examples 1-2 and Comparative Examples 1-2 in acidic media in this application.

[0032] Figure 5 is a comparison of the MOR cyclic voltammetry curves of the commercial Pt / C catalyst, the commercial PtRu / C catalyst, and the catalysts provided in Examples 1-2 in this application. Detailed Implementation

[0033] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0035] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0036] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0037] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0038] To address the technical challenges of traditional platinum-based catalysts, such as excessive adsorption of oxygen-containing intermediates (*O / *OH) by single platinum (Pt) active sites, easy metal dissolution under acidic conditions, and the inability to simultaneously achieve high ORR selectivity and methanol poisoning resistance, this application provides a high-entropy intermetallic compound bifunctional catalyst, its preparation method, and its application. Utilizing a unique high-entropy alloy combination of platinum (Pt), cobalt (Co), copper (Cu), tungsten (W), and molybdenum (Mo), the catalyst's activity and durability are enhanced. By combining wet chemical synthesis with controlled annealing, the catalyst simultaneously possesses both high-entropy effects and an ordered structure. The lattice distortion and dynamic reconstruction of multiple active sites induced by the high-entropy effect endow the material with both the stability of the alloy structure and the wide-range catalytic adaptability of a multi-element alloy, thereby achieving a balance between the catalyst's activity and durability in oxygen reduction and methanol oxidation.

[0039] In a first aspect, embodiments of this application provide a high-entropy intermetallic compound bifunctional catalyst. This catalyst comprises carbon-supported platinum-cobalt-copper-tungsten-molybdenum (Pt-Co-Cu-W-Mo) pentagonal high-entropy alloy nanoparticles, wherein the platinum loading is 20-70 wt%. The pentagonal high-entropy alloy nanoparticles possess both high-entropy effect and ordered structure, and have a particle size of 4-7 nm. The molar ratio of the metal atoms they contain is Pt:Co:Cu:W:Mo = 4:(1.75-2.5):(1.75-2.5):(0.01-0.5):(0.01-0.5). This catalyst is used for oxygen reduction reaction catalysis at the cathode in hydrogen fuel cells and / or methanol oxidation reaction catalysis at the anode in direct methanol fuel cells.

[0040] In the embodiments of this application, the half-wave potential of the high-entropy intermetallic compound bifunctional catalyst in acidic medium exceeds that of commercial Pt / C catalyst by 30 mV or more, and the peak current density of methanol oxidation is 1.4-2.5 times that of commercial Pt / C catalyst or commercial PtRu / C catalyst.

[0041] In this embodiment, the high-entropy intermetallic compound bifunctional catalyst is prepared by first uniformly dispersing chloroplatinic acid, cobalt chloride, copper chloride, hexacarbonyltungsten, and hexacarbonylmolybdenum in a mixed solution on a nano-carbon support, then placing it in a reaction vessel, reacting it under alkaline conditions, and then annealing it in a reducing atmosphere.

[0042] This application utilizes the high-entropy effect generated by the platinum (Pt)-cobalt (Co)-copper (Cu)-tungsten (W)-molybdenum (Mo) pentagonal system to suppress elemental segregation, grain coarsening, and phase separation by maximizing configurational entropy. It also inhibits elemental segregation and grain boundary migration, delays catalyst corrosion or agglomeration in acidic environments, and enhances structural stability. The unique high-entropy alloy combination of Pt-Co-Cu-W-Mo further improves the catalyst's activity and durability. Specifically, platinum provides the basic catalytic active sites, cobalt optimizes the electronic structure to weaken the adsorption of oxygen intermediates (such as CO and CH3O), and copper works synergistically with platinum and cobalt to form more effective active sites, improving the activity and selectivity of the ORR (Organic Ratio). The introduction of copper also induces strain in the platinum lattice, thereby changing the distance and arrangement between platinum atoms and promoting charge transport. Tungsten and molybdenum jointly construct a corrosion-resistant oxide layer (such as WO3 or MoO3), which can adsorb OH in the MOR (Metal-Oxide-Resistant) catalyst. -This process accelerates the oxidation of CO to CO2, providing resistance to poisoning. It also enhances the hydrophilicity of the catalyst surface, promoting the contact between methanol and water, increasing mass transfer efficiency, and thus improving catalyst stability and resistance to CO poisoning. In this way, the multi-element system forms a gradient electronic coupling effect in the ordered lattice. Specifically, the Pt-Co-Cu ternary synergy on the lattice surface significantly enhances the methanol oxidation resistance to poisoning, while the W / Mo subsurface oxide network effectively inhibits acidic medium corrosion, improves resistance to poisoning, and enhances mass transfer efficiency, resulting in simultaneous improvements in catalyst performance in both ORR and MOR.

[0043] Secondly, embodiments of this application provide a method for preparing a high-entropy intermetallic compound bifunctional catalyst, comprising the following steps:

[0044] S1. The nano-carbon support is ultrasonically dispersed evenly in a solvent to obtain a mixed solution. Then, chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl are added to the mixed solution. The pH is adjusted to 10-12 by adding an alkaline solution. The mixture is ultrasonically dispersed again and stirred to obtain a suspension.

[0045] In this embodiment, the solvent used in step S1 is glycerol, isopropanol, ethylene glycol, or DMF. Chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl, and molybdenum hexacarbonyl are each dissolved in a solvent before being added to the mixed solution. Specifically, tungsten hexacarbonyl and molybdenum hexacarbonyl are dissolved in DMF, wherein the concentration of tungsten hexacarbonyl is 0.2-1.2 mg / mL, and the concentration of molybdenum hexacarbonyl is 0.5-1.5 mg / mL. Chloroplatinic acid, cobalt chloride, and copper chloride are dissolved in glycerol, isopropanol, or ethylene glycol, wherein the concentration of chloroplatinic acid is 0.05-0.2 mol / L, the concentration of cobalt chloride is 0.05-0.3 mol / L, and the concentration of copper chloride is 0.05-0.3 mol / L.

[0046] In this embodiment of the application, in step S1, the molar ratio of metal atoms contained in chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl is Pt:Co:Cu:W:Mo=4:(1.75-2.5):(1.75-2.5):(0.01-0.5):(0.01-0.5).

[0047] In this embodiment, in step S1, the nano-carbon support is acidified graphitized carbon black, KJ600, KJ300, or BP2000. The concentration of the nano-carbon support in the mixed solution is 0.5-1 mg / mL.

[0048] In the embodiments of this application, the platinum loading is 20-70 wt%.

[0049] In this embodiment of the application, in step S1, the ultrasonication time is greater than or equal to 15 minutes, preferably 15-30 minutes. The stirring speed is 100-400 rpm, and the stirring time is greater than or equal to 10 minutes, preferably 10-30 minutes.

[0050] In this embodiment of the application, in step S1, the alkaline solution refers to an aqueous solution of sodium hydroxide with a concentration of 1 mol / L.

[0051] S2, the suspension obtained in step S1 is placed in a reaction vessel to react, resulting in a black colloidal solution. After filtration, washing, and drying, a black powder is obtained.

[0052] In this embodiment of the application, in step S2, the suspension is placed in a reaction vessel and reacted at 130-220°C for 0.5-5 hours to obtain a black colloidal solution.

[0053] In this embodiment of the application, in step S2, the filtration method is vacuum filtration or pressure filtration.

[0054] In this embodiment of the application, in step S2, the drying temperature is 60-85℃ and the drying time is 2-12h.

[0055] S3. The black powder obtained in step S2 is ground and placed in a tube furnace for annealing under a reducing atmosphere to obtain a high-entropy intermetallic compound bifunctional catalyst.

[0056] In this embodiment, the heating rate of the annealing treatment is 2-10℃ / min, the annealing temperature is 800-1000℃, and the annealing time is 0.5-3h.

[0057] In this embodiment, the reducing atmosphere is hydrogen or a hydrogen-argon mixture, preferably a hydrogen-argon mixture containing 5% hydrogen.

[0058] Thirdly, embodiments of this application provide an application of a high-entropy intermetallic compound bifunctional catalyst, which is used for catalysis of oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalysis of methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0059] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0060] Example 1

[0061] Example 1 provides a method for preparing a high-entropy intermetallic compound bifunctional catalyst, comprising the following steps:

[0062] S1, 25.8 mg of acidified graphitized carbon black was added to 40 mL of ethylene glycol and sonicated for 20 minutes. Then, using ethylene glycol as a solvent, 0.01 mol / L chloroplatinic acid solution, 0.1 mol / L cobalt chloride solution, and 0.1 mol / L copper chloride solution were prepared. Using DMF as a solvent, hexacarbonyltungsten solution and hexacarbonylmolybdenum solution were prepared. 8.1 mL of chloroplatinic acid solution, 0.405 mL of cobalt chloride solution, 0.405 mL of copper chloride solution, 2 mL of hexacarbonyltungsten solution, and 2 mL of hexacarbonylmolybdenum solution were added to the mixed solution. 1.2 mL of 1 mol / L sodium hydroxide aqueous solution was added, and the mixture was sonicated again and stirred to obtain a suspension.

[0063] S2. The suspension obtained in step S1 is placed in a 150 mL reaction vessel, heated to 190 °C, and kept at this temperature for 3 h to obtain a black colloidal solution. The solution is then vacuum filtered, washed with deionized water, and dried at 60 °C for 10 h to obtain a black powder.

[0064] S3. The black powder obtained in step S3 is ground and placed in a tube furnace. Under a reducing atmosphere, the temperature is raised to 800°C at a heating rate of 5°C / min and held for 0.5h. Then it is cooled to room temperature to obtain a high-entropy intermetallic compound bifunctional catalyst.

[0065] The X-ray diffraction (XRD) pattern of the high-entropy intermetallic compound bifunctional catalyst prepared in Example 1 is shown in Figure 1. It can be seen that the alloy-specific (110) and (001) superlattice characteristic peaks appear near the diffraction angles of 23° and 33°, indicating that a long-range ordered atomic arrangement structure has been formed in the catalyst.

[0066] The scanning electron microscope (SEM) image and EDS mapping image of the high-entropy intermetallic compound bifunctional catalyst prepared in Example 1 are shown in Figure 2. No aggregated metal particles were observed in the SEM image. Further EDS mapping test revealed signals of five metal elements: platinum, cobalt, copper, tungsten, and molybdenum. The five elements were evenly distributed in space, indicating that the five elements had formed a high-entropy structure.

[0067] The transmission electron microscope (TEM) image of the high-entropy intermetallic compound bifunctional catalyst prepared in Example 1 is shown in Figure 3. It can be seen that the dark-colored intermetallic compound nanoparticles are uniformly distributed on the carbon support without aggregation. The particle size of the nanoparticles is statistically analyzed to be 4-7 nm.

[0068] Example 2

[0069] The difference between Example 2 and Example 1 is that the amounts of cobalt chloride and copper chloride are changed. Specifically, in step S1, 0.608 mL of cobalt chloride solution and 0.203 mL of copper chloride solution are added to the mixed solution. The rest is the same as in Example 1, and will not be repeated here.

[0070] Comparative Example 1

[0071] The difference between Comparative Example 1 and Example 1 is that only a quaternary system of platinum, copper, tungsten and molybdenum is used, that is, cobalt chloride is not added in step S1. The rest is the same as Example 1, and will not be repeated here.

[0072] Comparative Example 2

[0073] The difference between Comparative Example 2 and Example 1 is that only a ternary system of platinum, cobalt, and copper is used, that is, tungsten hexacarbonyl and molybdenum hexacarbonyl are not added in step S1. The rest is the same as Example 1, and will not be repeated here.

[0074] Rotating disk polarization curves of commercial Pt / C catalysts, catalysts provided in Examples 1-2, and Comparative Examples 1-2 were tested in acidic media. The electrolyte solution was 0.1 mol / L HClO4 saturated with O2, the scan rate was 10 mV / s, the scan voltage range was -0.25 to 0.8 V, and the rotation speed was 1600 rpm. The comparison of the rotating disk polarization curves after iR compensation is shown in Figure 4, and the half-wave potentials are shown in Table 1.

[0075] Table 1. Half-wave potential of catalysts

[0076]

[0077] As can be seen, the initial half-wave potential of the catalyst provided in Example 1 exceeds that of the commercial Pt / C catalyst by 45 mV, and decreases by only 0.64% after 30,000 cycles. The initial half-wave potential of the catalyst provided in Example 2 exceeds that of the commercial Pt / C catalyst by 32 mV, and decreases by only 0.43% after 30,000 cycles (compared to a 6.93% decrease in half-wave potential after 30,000 cycles for the commercial Pt / C catalyst). In contrast, the initial half-wave potential and the half-wave potential after 30,000 cycles of Comparative Examples 1-2 are significantly lower than those of Examples 1-2, and the half-wave potential decreases significantly after 30,000 cycles (7.45% and 6.55%, respectively). This demonstrates that this application utilizes a unique high-entropy alloy combination of platinum (Pt), cobalt (Co), copper (Cu), tungsten (W), and molybdenum (Mo) to enhance the ORR activity and stability of the catalyst.

[0078] In Comparative Example 1, the absence of cobalt weakens the high-entropy effect, reducing the entropy value and leading to uneven element distribution, grain coarsening, or phase separation, thus accelerating catalyst performance degradation. Simultaneously, lattice stress imbalance causes structural collapse, eliminating the synergistic active sites formed by the five-element metals, altering the reaction pathway and mass transfer efficiency, ultimately resulting in lower ORR activity and stability of the catalyst. In Comparative Example 2, the absence of W and Mo significantly reduces the entropy value, making the material more susceptible to element diffusion or phase separation in acidic environments, accelerating catalyst corrosion or agglomeration. Furthermore, W and Mo readily form stable oxide layers on the alloy surface in acidic environments, inhibiting the dissolution of Pt and Co. Catalysts without W and Mo are more susceptible to electrolyte corrosion during long-term operation, leading to a rapid decline in active surface area. Finally, the absence of W and Mo also results in less lattice distortion, weakening the catalyst's ability to regulate the adsorption and desorption of reaction intermediates.

[0079] Cyclic voltammetry (CV) was used to test the methanol electrocatalytic oxidation (MOR) cyclic voltammetry of commercial Pt / C catalysts, commercial PtRu / C catalysts, and catalysts provided in Examples 1-2 and Comparative Examples 1-2. Before the test, N2 was bubbled through the electrolyte for half an hour to saturate the electrolyte and eliminate interference from soluble oxygen. Then, at 25°C, a scan rate of 50 mV / s, an initial potential of 0.1 V, and a scan voltage range of 0.1 V–1.0 V (vs. RHE) were performed for 20 cycles. The CV curves obtained after stabilization were used as the basis for evaluating the MOR activity of the catalysts. The electrolyte consisted of 1.0 mol / L KOH + 1.0 mol / L CH3OH. The comparison of the methanol electrocatalytic oxidation (MOR) cyclic voltammetry curves of the catalysts is shown in Figure 5, and the peak current densities are shown in Table 2.

[0080] Table 2. Peak current density of methanol oxidation catalyst

[0081]

[0082] As can be seen, the peak current density of methanol oxidation provided by the catalyst in Example 1 is significantly higher than that of Comparative Examples 1-2, being 2.3 times that of the commercial Pt / C catalyst and 1.48 times that of the commercial PtRu / C catalyst. In Comparative Example 1, the removal of Co reduced the entropy of the alloy system, making it more prone to local enrichment or phase separation of Cu and W / Mo, resulting in uneven distribution of active sites and slower methanol oxidation kinetics. Furthermore, the electronic synergistic effect between Co and elements such as W and Mo disappeared, leading to excessive adsorption of oxygen intermediates (CO, CH3O, etc.) by the catalyst, hindering further methanol oxidation, and reducing the number of multi-metallic interfacial active sites in the catalyst (the Pt-Co-Cu or Pt-Co-W / Mo multi-metal interfaces disappeared). In Comparative Example 2, the removal of W and Mo significantly reduced the entropy of the alloy system, similarly disrupting the uniform distribution of active sites. Simultaneously, the disappearance of the multi-metallic synergistic effect between W and Mo and Pt / Co led to excessive CO adsorption, exacerbating catalyst poisoning. Moreover, due to the lack of coating effect from W and Mo oxides, the catalyst is more susceptible to electrolyte corrosion during long-term operation. Finally, W / Mo oxides (such as WO3 and MoO3) can adsorb OH in MOR. - The W / Mo oxides accelerate the oxidation of CO to CO2, thus acting as an anti-poisoning agent. At the same time, the W / Mo oxides can enhance the hydrophilicity of the catalyst surface, promote the contact between methanol and water, and increase the mass transfer efficiency. After removing W and Mo, the aforementioned effects disappear.

[0083] In summary, this application combines wet chemical synthesis with controlled annealing to prepare a carbon-supported pentagonal (Pt-Co-Cu-W-Mo) high-entropy intermetallic compound bifunctional catalyst. This catalyst exhibits high electrocatalytic activity and good durability in the oxygen reduction reaction at the cathode of hydrogen fuel cells and / or the methanol oxidation reaction at the anode of direct methanol fuel cells. Its half-wave potential in acidic media exceeds that of commercial Pt / C catalysts by 30 mV or more, and its peak current density for methanol oxidation is 2.33 times that of commercial Pt / C catalysts and 1.48 times that of commercial PtRu / C catalysts.

[0084] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A high-entropy intermetallic compound bifunctional catalyst, characterized in that, The high-entropy intermetallic compound bifunctional catalyst comprises carbon-supported platinum-cobalt-copper-tungsten-molybdenum pentagonal high-entropy alloy nanoparticles. These pentagonal high-entropy alloy nanoparticles possess both high-entropy effect and ordered structure, with a particle size of 4-7 nm. The molar ratio of metal atoms in the pentagonal high-entropy alloy nanoparticles is platinum:cobalt:copper:tungsten:molybdenum = 4:(1.75-2.5):(1.75-2.5):(0.01-0.5):(0.01-0.5). The high-entropy intermetallic compound bifunctional catalyst comprises carbon-supported platinum-cobalt-copper-tungsten-molybdenum pentagonal high-entropy alloy nanoparticles. The platinum loading in the catalyst is 20-70 wt%; the high-entropy intermetallic compound bifunctional catalyst is used for oxygen reduction reaction catalysis at the cathode in hydrogen fuel cells and / or methanol oxidation reaction catalysis at the anode in direct methanol fuel cells; the high-entropy intermetallic compound bifunctional catalyst is prepared by first uniformly dispersing chloroplatinic acid, cobalt chloride, copper chloride, hexacarbonyltungsten, and hexacarbonylmolybdenum in a mixed solution on a nano-carbon support, then placing it in a reaction vessel, reacting it under alkaline conditions, and then annealing it in a reducing atmosphere.

2. The high-entropy intermetallic compound bifunctional catalyst according to claim 1, characterized in that, The high-entropy intermetallic compound bifunctional catalyst exhibits a half-wave potential in acidic media that exceeds that of commercial Pt / C catalysts by 30 mV or more, and its peak current density for methanol oxidation is 1.4-2.5 times that of commercial Pt / C or PtRu / C catalysts.

3. A method for preparing a high-entropy intermetallic compound bifunctional catalyst according to any one of claims 1-2, characterized in that, The process includes the following steps: S1, the nano-carbon support is ultrasonically dispersed evenly in a solvent to obtain a mixed solution, then chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl are added to the mixed solution, an alkaline solution is added to adjust the pH to 10-12, ultrasonically dispersed again, stirred, and a suspension is obtained. S2, the suspension obtained in step S1 is placed in a reaction vessel to react, and a black colloidal solution is obtained. After filtration, washing, and drying, a black powder is obtained. S3, the black powder obtained in step S2 is ground and placed in a tube furnace for annealing under a reducing atmosphere to obtain a high-entropy intermetallic compound bifunctional catalyst.

4. The method for preparing the high-entropy intermetallic compound bifunctional catalyst according to claim 3, characterized in that, The solvent used in step S1 is glycerol, isopropanol, ethylene glycol, or DMF. Chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl, and molybdenum hexacarbonyl are dissolved separately in the solvent before being added to the mixed solution. Specifically, tungsten hexacarbonyl and molybdenum hexacarbonyl are dissolved in DMF, with a concentration of 0.2-1.2 mg / mL for tungsten hexacarbonyl and 0.5-1.5 mg / mL for molybdenum hexacarbonyl. Chloroplatinic acid, cobalt chloride, and copper chloride are dissolved in glycerol, isopropanol, or ethylene glycol, with a concentration of 0.05-0.2 mol / L for chloroplatinic acid, 0.05-0.3 mol / L for cobalt chloride, and 0.05-0.3 mol / L for copper chloride.

5. The method for preparing the high-entropy intermetallic compound bifunctional catalyst according to claim 3, characterized in that, In step S1, the molar ratio of metal atoms contained in chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl is Pt:Co:Cu:W:Mo=4:(1.75-2.5):(1.75-2.5):(0.01-0.5):(0.01-0.5).

6. The method for preparing the high-entropy intermetallic compound bifunctional catalyst according to claim 3, characterized in that, In step S1, the nano-carbon support is acidified graphitized carbon black, KJ600, KJ300, or BP2000; the concentration of the nano-carbon support in the mixed solution is 0.5-1 mg / mL, and the alkaline solution refers to a 1 mol / L sodium hydroxide aqueous solution; in step S1, the ultrasonic time is greater than or equal to 15 min, and the stirring time is greater than or equal to 10 min.

7. The method for preparing the high-entropy intermetallic compound bifunctional catalyst according to claim 3, characterized in that, In step S2, the suspension is placed in a reaction vessel and reacted at 130-220℃ for 0.5-5 hours to obtain the black colloidal solution; the filtration method is vacuum filtration or pressure filtration; the drying temperature is 60-85℃ and the drying time is 2-12 hours.

8. The method for preparing the high-entropy intermetallic compound bifunctional catalyst according to claim 3, characterized in that, In step S3, the heating rate of the annealing treatment is 2-10℃ / min, the annealing temperature is 800-1000℃, and the annealing time is 0.5-3h; the reducing atmosphere is hydrogen or a hydrogen-argon mixture.

9. The application of a high-entropy intermetallic compound bifunctional catalyst according to any one of claims 1-2, characterized in that, The high-entropy intermetallic compound bifunctional catalyst is used for oxygen reduction reaction catalysis at the cathode in hydrogen fuel cells and / or methanol oxidation reaction catalysis at the anode in direct methanol fuel cells.

Images