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

Abstract

The invention provides a high-entropy intermetallic compound bifunctional catalyst as well as a preparation method and application thereof, and belongs to the technical field of energy materials. A wet chemical synthesis method and a controllable annealing process are combined to prepare the high-entropy intermetallic compound bifunctional catalyst, the catalyst comprises carbon-loaded platinum-cobalt-copper-tungsten-molybdenum five-element high-entropy alloy nanoparticles, the alloy nanoparticles have a high-entropy effect and an ordered structure at the same time, the particle size is 4-7 nm, and the particle size of the alloy nanoparticles is 4-7 nm. The molar ratio of metal atoms, namely platinum to cobalt to copper to tungsten to molybdenum, is 4: (1.75 to 2.5): (1.75 to 2.5): (0.01 to 0.5): (0.01 to 0.5). The platinum loading capacity in the catalyst is 20-70 wt%, the catalyst is used for oxygen reduction reaction catalysis of a cathode in a hydrogen fuel cell and / or methanol oxidation reaction catalysis of an anode in a direct methanol fuel cell, the half-wave potential in an acid medium exceeds a commercial Pt / C catalyst by 30 mV or above, and the methanol oxidation peak current density is 1.4-2.5 times that of the commercial Pt / C catalyst or a commercial PtRu / C catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and particularly to a high-entropy intermetallic compound bifunctional catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of proton exchange membrane fuel cells, the following defects are exposed by traditional platinum-based catalysts: the adsorption of oxygen-containing intermediates (*O / *OH) by a single platinum (Pt) active site is too strong, resulting in sluggish ORR kinetics, and the ORR catalytic performance of the catalyst still needs to be improved; metal dissolution is likely to occur under acidic conditions, leading to agglomeration of nanoparticles and affecting the stability and service life of the catalyst; the poisoning phenomenon of CO intermediates during the methanol oxidation process seriously affects the stability of the catalyst, making it impossible for traditional platinum-based catalysts to simultaneously achieve high ORR selectivity and anti-methanol poisoning characteristics. How to improve traditional platinum-based catalysts to make up for the above defects is the core challenge in improving energy conversion efficiency.

[0003] In the prior art, some researchers have used binary / ternary Pt-M (M = Fe, Co, Ni, etc.) alloys to regulate the electronic structure to solve the above problems. However, the improvement of the activity of the catalyst by this scheme is limited because the regulation dimension of the binary / ternary element combination is relatively single (such as only electronic effect or strain effect). Chinese Patent with Publication No. CN119481112A provides a platinum-cobalt intermetallic compound supported on nitrogen-doped carbon with rich defects, a preparation method thereof, and an application thereof. First, a two-dimensional leaf-shaped ZIF is used as a precursor, and under the action of a mixed molten salt of KCl and NH4Cl, after high-temperature calcination, a nitrogen-doped carbon material is obtained. Then, it is heat-treated with NH3 to remove pyrrole nitrogen and pyridine nitrogen in the nitrogen-doped carbon material to form topological defect active sites. Finally, a PtCo metal intermetallic compound catalyst supported on nitrogen-doped carbon with rich defects is formed by a gas-phase reduction method. The topological defects of the carbon carrier can anchor the platinum-cobalt alloy, thereby inhibiting the agglomeration of nanoparticles during the high-temperature synthesis process to improve the activity, and can also inhibit the agglomeration and dissolution of nanoparticles during the electrochemical reaction process to improve the durability. However, its preparation process requires high-temperature and long-time annealing treatment, the synthesis conditions are relatively harsh, and it is easy to cause element volatilization and particle coarsening, and it is temporarily difficult to be prepared on a large scale.

[0004] The Chinese patent with the publication number CN119524874A provides a hydrophilic carbon-based material modified high-entropy alloy electrocatalyst for hydrogen production by electrolyzing water, its preparation method and application. A hydrophilic carbon-based material and mixed metal salts (platinum, palladium, cobalt, nickel, copper) are added to an ethylene glycol solution and mixed evenly to obtain a reaction solution. Then the reaction solution is slowly added to an ethylene glycol solution at 200 - 240 °C and heat-treated for 0.5 - 2 h to obtain a hydrophilic carbon-based material modified high-entropy alloy electrocatalyst for hydrogen production by electrolyzing water. This hydrogen production catalyst has high activity, and the generated hydrogen bubbles are smaller and easier to detach from the electrode surface. However, the internal alloy has a disordered solid solution structure with randomly arranged surface atoms, and the active sites are unevenly distributed. Moreover, the HEAs prepared by traditional mechanical alloying or sputtering methods have problems such as composition 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 to solve the above problems. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the present application provides a high-entropy intermetallic compound bifunctional catalyst, its preparation method and application, aiming to solve the technical problems that the single platinum (Pt) active site of the traditional platinum-based catalyst has too strong adsorption of oxygen-containing intermediates (*O / *OH), is prone to metal dissolution under acidic conditions, and cannot simultaneously achieve high ORR selectivity and anti-methanol poisoning characteristics.

[0007] The present application has prepared a carbon-supported quinary (Pt-Co-Cu-W-Mo) high-entropy intermetallic compound bifunctional catalyst. The unique high-entropy alloy combination of platinum (Pt), cobalt (Co), copper (Cu), tungsten (W), and molybdenum (Mo) is used to improve the activity and durability of the catalyst. By combining the wet chemical synthesis method with a controllable annealing process, the catalyst simultaneously has a high-entropy effect 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 the multi-component alloy, thereby achieving the balance of the activity and durability of the catalyst in oxygen reduction and methanol oxidation.

[0008] First aspect, an embodiment of the present application provides a high-entropy intermetallic compound bifunctional catalyst, which has carbon-supported platinum-cobalt-copper-tungsten-molybdenum quinary high-entropy alloy nanoparticles; the quinary high-entropy alloy nanoparticles have both high-entropy effect and ordered structure, with a particle size of 4-7 nm, and the molar ratio of metal atoms contained in the quinary 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 platinum loading in the high-entropy intermetallic compound bifunctional catalyst is 20-70 wt%; the high-entropy intermetallic compound bifunctional catalyst is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0009] Furthermore, 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.

[0010] Furthermore, the high-entropy intermetallic compound bifunctional catalyst is prepared by first dispersing chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl uniformly in a mixed solution of a nanocarbon support, then placing it in a reaction kettle, reacting under alkaline conditions, and then annealing it in a reducing atmosphere.

[0011] Second aspect, an embodiment of the present application provides a preparation method of a high-entropy intermetallic compound bifunctional catalyst, including the following steps: S1, ultrasonically disperse the nanocarbon support uniformly in a solvent to obtain a mixed solution, then add chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl to the mixed solution, add an alkali solution to adjust the pH to 10-12, ultrasonically disperse again, and stir to obtain a suspension; S2, place the suspension obtained in step S1 in a reaction kettle to react to obtain a black colloidal solution, filter, wash, and dry to obtain a black powder; S3, grind the black powder obtained in step S2 and place it in a tube furnace for annealing treatment in a reducing atmosphere to obtain a high-entropy intermetallic compound bifunctional catalyst.

[0012] Further, 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 respectively dissolved in the solvent and then added to the mixed solution. Specifically, tungsten hexacarbonyl and molybdenum hexacarbonyl are dissolved in DMF, 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. Among them, 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.

[0013] Further, 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).

[0014] Further, in step S1, the nano-carbon carrier is acidified graphitized carbon black, KJ600, KJ300 or BP2000. The concentration of the nano-carbon carrier in the mixed solution is 0.5 - 1 mg / mL. The alkali solution refers to an aqueous sodium hydroxide solution with a concentration of 1 mol / L. 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.

[0015] Further, in step S2, the suspension is placed in a reaction kettle and reacted at 130 - 220 °C for 0.5 - 5 h 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 h.

[0016] Further, in step S3, the heating rate of the annealing treatment is 2 - 10 °C / min, the annealing treatment temperature is 800 - 1000 °C, and the annealing treatment time is 0.5 - 3 h. The reducing atmosphere is hydrogen or a hydrogen-argon mixed gas.

[0017] In the third aspect, the embodiments of the present application provide an application of a high-entropy intermetallic compound bifunctional catalyst, and the high-entropy intermetallic compound bifunctional catalyst is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0018] The beneficial effects of the present application are as follows: The present application combines a wet chemical synthesis method with a controllable annealing process to prepare a carbon-supported quinary high-entropy intermetallic compound bifunctional catalyst.

[0019] (1) This application utilizes the high-entropy effect generated by the platinum (Pt)-cobalt (Co)-copper (Cu)-tungsten (W)-molybdenum (Mo) quinary system to suppress element segregation, grain coarsening, and phase separation by maximizing configurational entropy, inhibit element segregation and grain boundary migration, delay the corrosion or agglomeration of the catalyst in an acidic environment, and enhance structural stability. The unique high-entropy alloy combination of Pt-Co-Cu-W-Mo also improves the activity and durability of the catalyst. Among them, the basic catalytic active sites are provided by platinum, and cobalt optimizes the electronic structure to weaken the adsorption of oxygen intermediates (such as CO, CH3O). Copper acts together with platinum and cobalt to form more effective active sites, enhancing the activity and selectivity of ORR. The introduction of copper also induces strain in the platinum lattice, thereby changing the distance and arrangement of platinum atoms and promoting charge transfer. Tungsten and molybdenum jointly construct a corrosion-resistant oxide layer (such as WO3, MoO3), which can adsorb OH in MOR - , accelerate the oxidation of CO to CO2, play an anti-poisoning role, and can also enhance the hydrophilicity of the catalyst surface, promote the contact between methanol and water, increase the mass transfer efficiency, and improve the catalyst stability and anti-CO poisoning performance. In this way, the multi-element system forms a gradient electron coupling effect in the ordered lattice, that is, the ternary synergy of Pt-Co-Cu on the lattice surface significantly improves the anti-poisoning ability of methanol oxidation, while the W / Mo subsurface oxide network effectively inhibits corrosion in acidic media, improves the anti-poisoning performance and mass transfer efficiency, synchronously enhancing the performance of the catalyst in ORR and MOR.

[0020] (2) This application combines the wet chemical synthesis method with a controllable annealing process, enabling the catalyst to simultaneously possess the high-entropy effect and an ordered structure. By utilizing the lattice distortion and dynamic reconstruction of multiple active sites induced by the high-entropy effect, the material combines the stability of the alloy structure and the broad catalytic adaptability of the multi-component alloy, thereby achieving a balance between the activity and durability of the catalyst in oxygen reduction and methanol oxidation. This application uses the high-entropy effect to form a single solid solution structure, enabling the dynamic reconstruction of surface / near-surface elements of the quinary high-entropy alloy nanoparticles to form gradient active sites. At the same time, lattice distortion occurs inside the nanoparticles, generating a strain-electron synergy effect. The gradient active sites, strain-electron synergy effect, and multi-element redox reactions jointly broaden the potential response window of the catalyst, which is beneficial for increasing the energy density or meeting different reaction requirements in electrocatalysis.

[0021] (3) The preparation method provided by this application has a short operation process, can be prepared in batches, and is suitable for industrial production. The catalyst provided by this application is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell, and has high electrocatalytic activity and good durability. The half-wave potential in acidic media 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.

[0022] The above description is only an overview of the technical solution of the present application. In order to better understand the technical means of the present application, it can be implemented according to the content of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and understandable, specific embodiments of the present application are given below. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solution of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 XRD pattern of the high-entropy intermetallic compound bifunctional catalyst provided in Example 1 of the present application; Figure 2 SEM image and EDS mapping test image of the high-entropy intermetallic compound bifunctional catalyst provided in Example 1 of the present application; Figure 3 TEM image of the high-entropy intermetallic compound bifunctional catalyst provided in Example 1 of the present application; Figure 4 Comparison diagram of rotating disk polarization curves (after i-R compensation) of commercial Pt / C catalyst, catalysts provided in Examples 1-2 and Comparative Examples 1-2 in acidic medium in the present application; Figure 5 Comparison diagram of MOR cyclic voltammograms of commercial Pt / C catalyst, commercial PtRu / C catalyst and catalysts provided in Examples 1-2 in the present application. Detailed Description of the Embodiments

[0025] The embodiments of the technical solution of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0027] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0028] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after. For those of ordinary skill in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0030] In order to solve the technical problems that the single platinum (Pt) active site of the traditional platinum-based catalyst has too strong adsorption of oxygen-containing intermediates (*O / *OH), metal dissolution is likely to occur under acidic conditions, and it is impossible to simultaneously achieve high ORR selectivity and anti-methanol poisoning characteristics, the present application provides a high-entropy intermetallic compound bifunctional catalyst, its preparation method and application. The unique high-entropy alloy combination of platinum (Pt), cobalt (Co), copper (Cu), tungsten (W), and molybdenum (Mo) is used to improve the activity and durability of the catalyst. By combining the wet chemical synthesis method with a controllable annealing process, the catalyst simultaneously has a high-entropy effect 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 broad catalytic adaptability of the multi-component alloy, thereby achieving the balance of the activity and durability of the catalyst in oxygen reduction and methanol oxidation.

[0031] In a first aspect, an embodiment of the present application provides a high-entropy intermetallic compound bifunctional catalyst, which has carbon-supported platinum-cobalt-copper-tungsten-molybdenum (Pt-Co-Cu-W-Mo) quinary high-entropy alloy nanoparticles. Among them, the loading amount of platinum is 20-70 wt%. The quinary high-entropy alloy nanoparticles simultaneously have a high-entropy effect and an ordered structure, and the particle size is 4-7 nm. The molar ratio of the metal atoms contained therein 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 catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0032] In an embodiment of the present application, the half-wave potential of the high-entropy intermetallic compound bifunctional catalyst in an acidic medium exceeds that of a 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 a commercial Pt / C catalyst or a commercial PtRu / C catalyst.

[0033] In an embodiment of the present application, the high-entropy intermetallic compound bifunctional catalyst is prepared by first dispersing chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl, and molybdenum hexacarbonyl uniformly in a mixed solution of a nano-carbon carrier, then placing it in a reaction kettle, reacting under alkaline conditions, and then annealing in a reducing atmosphere.

[0034] The present application utilizes the high-entropy effect generated by the platinum (Pt)-cobalt (Co)-copper (Cu)-tungsten (W)-molybdenum (Mo) quinary system to suppress element segregation, grain coarsening, and phase separation by maximizing configurational entropy, inhibit element segregation and grain boundary migration, delay the corrosion or agglomeration of the catalyst in an acidic environment, and improve the structural stability. The unique high-entropy alloy combination of Pt-Co-Cu-W-Mo also improves the activity and durability of the catalyst. Among them, the basic catalytic active sites are provided by platinum, cobalt optimizes the electronic structure to weaken the adsorption of oxygen intermediates (such as CO, CH3O), copper acts together with platinum and cobalt to form more effective active sites, and improves the activity and selectivity of ORR. The introduction of copper also induces strain in the platinum lattice, thereby changing the distance and arrangement of platinum atoms and promoting charge transport. Tungsten and molybdenum jointly construct a corrosion-resistant oxide layer (such as WO3, MoO3), and this oxide layer can adsorb OH in MOR -, accelerating the oxidation of CO to CO₂, playing an anti-poisoning role, enhancing the hydrophilicity of the catalyst surface, promoting the contact between methanol and water, and increasing the mass transfer efficiency to improve the catalyst stability and anti-CO poisoning performance. In this way, a gradient electron coupling effect is formed in the ordered lattice of the multi-element system, that is, the ternary synergy of Pt-Co-Cu on the lattice surface significantly improves the anti-poisoning ability of methanol oxidation, while the W / Mo subsurface oxide network effectively inhibits the corrosion in acidic media, improves the anti-poisoning performance and mass transfer efficiency, synchronously enhancing the performance of the catalyst in ORR and MOR.

[0035] In a second aspect, an embodiment of the present application provides a method for preparing a high-entropy intermetallic compound bifunctional catalyst, including the following steps: S1, ultrasonically dispersing a nano-carbon carrier uniformly in a solvent to obtain a mixed solution, and then adding chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl, and molybdenum hexacarbonyl to the mixed solution, adding an alkali solution to adjust the pH to 10-12, and ultrasonically dispersing and stirring again to obtain a suspension.

[0036] In the embodiment of the present application, 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 respectively dissolved in the solvent and then 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.

[0037] In the embodiment of the present 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).

[0038] In the embodiment of the present application, in step S1, the nano-carbon carrier is acidified graphitized carbon black, KJ600, KJ300, or BP2000. In the mixed solution, the concentration of the nano-carbon carrier is 0.5-1 mg / mL.

[0039] In the embodiment of the present application, the platinum loading is 20-70 wt%.

[0040] In the embodiment of the present application, in step S1, the time of ultrasonic treatment is greater than or equal to 15 min, preferably 15 - 30 min. The rotation speed of stirring is 100 - 400 rpm, and the time of stirring is greater than or equal to 10 min, preferably 10 - 30 min.

[0041] In the embodiment of the present application, in step S1, the alkaline solution refers to an aqueous sodium hydroxide solution with a concentration of 1 mol / L.

[0042] S2. Place the suspension obtained in step S1 in a reaction kettle for reaction to obtain a black colloidal solution. After filtration, washing, and drying, a black powder is obtained.

[0043] In the embodiment of the present application, in step S2, the suspension is placed in a reaction kettle and reacted at 130 - 220 °C for 0.5 - 5 h to obtain a black colloidal solution.

[0044] In the embodiment of the present application, in step S2, the filtration method is vacuum filtration or pressure filtration.

[0045] In the embodiment of the present application, in step S2, the drying temperature is 60 - 85 °C, and the drying time is 2 - 12 h.

[0046] S3. Grind the black powder obtained in step S2 and place it in a tubular furnace for annealing treatment in a reducing atmosphere to obtain a high-entropy intermetallic compound bifunctional catalyst.

[0047] In the embodiment of the present application, the heating rate of the annealing treatment is 2 - 10 °C / min, the annealing treatment temperature is 800 - 1000 °C, and the annealing treatment time is 0.5 - 3 h.

[0048] In the embodiment of the present application, the reducing atmosphere is hydrogen or a hydrogen-argon mixed gas, preferably a hydrogen-argon mixed gas containing 5% hydrogen.

[0049] In a third aspect, the embodiment of the present application provides an application of a high-entropy intermetallic compound bifunctional catalyst, and this catalyst is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0050] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specific technologies or conditions indicated in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0051] Example 1 Example 1 provides a preparation method of a high-entropy intermetallic compound bifunctional catalyst, including the following steps: S1. Add 25.8 mg of acidified graphitized carbon black into 40 mL of ethylene glycol, and ultrasonicate for 20 minutes. Then, using ethylene glycol as the solvent, prepare 0.01 mol / L chloroplatinic acid solution, 0.1 mol / L cobalt chloride solution, and 0.1 mol / L copper chloride solution. Using DMF as the solvent, prepare tungsten hexacarbonyl solution and molybdenum hexacarbonyl solution. Add 8.1 mL of chloroplatinic acid solution, 0.405 mL of cobalt chloride solution, 0.405 mL of copper chloride solution, 2 mL of tungsten hexacarbonyl solution, and 2 mL of molybdenum hexacarbonyl solution into the mixed solution, add 1.2 mL of 1 mol / L sodium hydroxide aqueous solution, ultrasonically disperse again, and stir to obtain a suspension.

[0052] S2. Place the suspension obtained in step S1 into a reaction kettle with a volume of 150 mL, heat to 190 °C, and hold the reaction for 3 h to obtain a black colloidal solution. Filter it under vacuum, wash it with deionized water, and then dry it at 60 °C for 10 h to obtain a black powder.

[0053] S3. Grind the black powder obtained in step S3 and place it in a tubular furnace. Under a reducing atmosphere, heat it to 800 °C at a heating rate of 5 °C / min and hold for 0.5 h, and then cool it to room temperature to obtain a high-entropy intermetallic compound bifunctional catalyst.

[0054] The X-ray diffraction (XRD) pattern of the high-entropy intermetallic compound bifunctional catalyst prepared in Example 1 is shown in Figure 1 As can be seen, characteristic peaks of (110) and (001) superlattices unique to the alloy appear near diffraction angles of 23° and 33°, indicating that a long-range ordered atomic arrangement structure is formed in the catalyst.

[0055] The scanning electron microscope image (SEM) and EDS mapping image of the high-entropy intermetallic compound bifunctional catalyst prepared in Example 1 are shown in Figure 2 As shown, no agglomerated metal particles are observed in the SEM image. Further, EDS mapping test is carried out, and signals of five metal elements, namely platinum, cobalt, copper, tungsten, and molybdenum, are observed, and the five elements are evenly distributed in space, indicating that the five elements have formed a high-entropy structure.

[0056] The transmission electron microscope image (TEM) of the high-entropy intermetallic compound bifunctional catalyst prepared in Example 1 is shown in Figure 3 As can be seen, dark-colored intermetallic compound nanoparticles are evenly distributed on the carbon support without agglomeration. After statistics, the particle size of the nanoparticles is 4 - 7 nm.

[0057] Example 2 Example 2 is different from Example 1 in that the dosages 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, and the others are the same as in Example 1, which will not be elaborated here.

[0058] Comparative Example 1 Comparative Example 1 is different from Example 1 in that only a quaternary system of platinum, copper, tungsten, and molybdenum is used, that is, cobalt chloride is not added in step S1, and the others are the same as in Example 1, which will not be elaborated here.

[0059] Comparative Example 2 Comparative Example 2 is different from Example 1 in 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, and the others are the same as in Example 1, which will not be elaborated here.

[0060] The rotating disk polarization curves of the commercial Pt / C catalyst, the catalysts provided in Examples 1-2, and Comparative Examples 1-2 in an acidic medium were tested. Among them, the electrolyte solution was 0.1 mol / L HClO4 saturated with O2, the scanning rate was 10 mV / s, the scanning voltage range was -0.25 to 0.8 V, and the rotation speed was 1600 rpm. For the comparison graph of the rotating disk polarization curves after i-R compensation obtained by the test, see Figure 4 as shown, and the half-wave potential is shown in Table 1.

[0061] Table 1. Half-wave potential of the catalysts It can be seen that the initial half-wave potential of the catalyst provided in Example 1 exceeds that of the commercial Pt / C catalyst by 45 mV, and only decreases by 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 only decreases by 0.43% after 30,000 cycles (the half-wave potential of the commercial Pt / C catalyst decreases by 6.93% after 30,000 cycles). However, 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 (decreasing by 7.45% and 6.55% respectively). It shows that the unique high-entropy alloy combination of platinum (Pt), cobalt (Co), copper (Cu), tungsten (W), and molybdenum (Mo) in this application improves the ORR activity and stability of the catalyst.

[0062] In Comparative Example 1, cobalt metal is not added, the high-entropy effect is weakened, and the entropy value is reduced, resulting in uneven element distribution, grain coarsening or phase separation, and accelerating the performance decay of the catalyst. At the same time, the imbalance of lattice stress leads to the collapse of the structure, the disappearance of the synergistic active sites formed by the five-element metal, the change of the reaction path and mass transfer efficiency, and finally the low ORR activity and stability of the catalyst. In Comparative Example 2, W and Mo are not added, and the entropy value is greatly reduced, resulting in easier element diffusion or phase separation of the material in an acidic working environment, and accelerating catalyst corrosion or agglomeration. Secondly, W and Mo are prone to form a stable oxide layer on the alloy surface in an acidic environment, which can inhibit the dissolution of Pt and Co. The catalyst without W and Mo is more easily corroded by the electrolyte during long-term operation, and the active specific surface area decays rapidly. Finally, the absence of W and Mo also results in relatively less lattice distortion, leading to a weakened ability of the catalyst to regulate the adsorption and desorption of reaction intermediates.

[0063] Cyclic voltammetry (CV) was used to perform cyclic voltammetry tests on methanol electrocatalytic oxidation (MOR) of commercial Pt / C catalyst, commercial PtRu / C catalyst, Examples 1-2 and Comparative Examples 1-2. Before the test, N2 was introduced for half an hour to saturate the N2 in the electrolyte to exclude the interference of soluble oxygen on the test results. Then, at 25 °C, the scan rate was set to 50 mV / s, the initial potential was set to 0.1 V, and the scanning voltage range was 0.1 V - 1.0 V (vs. RHE). Twenty cycles of cyclic voltammetry tests were carried out, and the CV curve obtained after stabilization was used as the basis for evaluating the MOR activity of the catalyst, where the electrolyte was 1.0 mol / L KOH + 1.0 mol / L CH3OH. The comparison diagram of the cyclic voltammetry curves of methanol electrocatalytic oxidation (MOR) of the catalysts obtained from the test is shown in Figure 5 as shown, and the peak current density is shown in Table 2.

[0064] Table 2. Peak current density of methanol oxidation of the catalyst It can be seen that the peak current density of methanol oxidation of the catalyst provided 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. After removing Co in Comparative Example 1, the entropy value of the alloy system decreases, resulting in easier local enrichment or phase separation of Cu and W / Mo in the system, uneven distribution of active sites, and slower methanol oxidation kinetics. Secondly, the electronic synergistic effect between Co and elements such as W and Mo disappears, leading to too strong adsorption of the catalyst on oxygen intermediates (such as CO and CH3O), hindering the further oxidation of methanol, and reducing the multi-element interface active sites in the catalyst (the disappearance of multi-metal interfaces such as Pt-Co-Cu or Pt-Co-W / Mo). After removing W and Mo in Comparative Example 2, the entropy value of the alloy system decreases significantly, also destroying the uniform distribution of active sites. At the same time, the multi-metal synergistic effect between W, Mo and Pt / Co disappears, resulting in too strong CO adsorption and exacerbating catalyst poisoning. Secondly, due to the lack of the coating effect of W and Mo oxides, the catalyst is more easily corroded by the electrolyte during long-term operation. Finally, oxides of W / Mo (such as WO3 and MoO3) can adsorb OH - , accelerating the oxidation of CO to CO2 and playing an anti-poisoning role. At the same time, the oxides of W / Mo can also enhance the hydrophilicity of the catalyst surface, promote the contact between methanol and water, increase the mass transfer efficiency. After removing W and Mo, the above-mentioned effects disappear.

[0065] In summary, the present application combines a wet chemical synthesis method with a controllable annealing process to prepare a carbon-supported quinary (Pt-Co-Cu-W-Mo) high-entropy intermetallic compound bifunctional catalyst, which has high electrocatalytic activity and good durability in the catalysis of oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or the catalysis of methanol oxidation reaction at the anode in a direct methanol fuel cell. The half-wave potential in acidic medium exceeds that of the commercial Pt / C catalyst by 30 mV or more, and the peak current density of methanol oxidation is 2.33 times that of the commercial Pt / C catalyst and 1.48 times that of the commercial PtRu / C catalyst.

[0066] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope of not departing from the gist of the present application, various deformations that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A high-entropy intermetallic compound bifunctional catalyst, characterized in that, The high-entropy intermetallic compound bifunctional catalyst has carbon-supported platinum-cobalt-copper-tungsten-molybdenum quinary high-entropy alloy nanoparticles; the quinary high-entropy alloy nanoparticles have both high-entropy effect and ordered structure, with a particle size of 4-7 nm, and the molar ratio of metal atoms contained in the quinary 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 platinum loading in the high-entropy intermetallic compound bifunctional catalyst is 20-70 wt%; the high-entropy intermetallic compound bifunctional catalyst is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

2. The high-entropy intermetallic compound bifunctional catalyst according to claim 1, wherein 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.

3. The high-entropy intermetallic compound bifunctional catalyst according to claim 1, characterized in that, The high-entropy intermetallic compound bifunctional catalyst is prepared by first dispersing chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl uniformly in a mixed solution of a nano-carbon carrier, then placing it in a reaction kettle, reacting under alkaline conditions, and then annealing in a reducing atmosphere.

4. A method for preparing the high-entropy intermetallic compound bifunctional catalyst according to any one of claims 1-3, characterized in that, It includes the following steps: S1, ultrasonically disperse the nano-carbon carrier uniformly in a solvent to obtain a mixed solution, then add chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl to the mixed solution, add an alkali solution to adjust the pH to 10-12, ultrasonically disperse again, and stir to obtain a suspension; S2, place the suspension obtained in step S1 in a reaction kettle to react to obtain a black colloidal solution, filter, wash, and dry to obtain a black powder; S3, grind the black powder obtained in step S2 and place it in a tubular furnace, and perform annealing treatment under a reducing atmosphere to obtain a high-entropy intermetallic compound bifunctional catalyst.

5. The preparation method of the high-entropy intermetallic compound bifunctional catalyst according to claim 4, wherein, The solvent used in step S1 is glycerol, isopropyl alcohol, ethylene glycol or DMF. Chloroplatinic acid, cobalt chloride, copper chloride, tungsten hexacarbonyl and molybdenum hexacarbonyl are respectively dissolved in the solvent and then added to the mixed solution; specifically, tungsten hexacarbonyl and molybdenum hexacarbonyl are dissolved in DMF, 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, isopropyl alcohol 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.

6. The preparation method of the high-entropy intermetallic compound bifunctional catalyst according to claim 4, wherein, 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).

7. The preparation method of the high-entropy intermetallic compound bifunctional catalyst according to claim 4, wherein, 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 alkali solution refers to an aqueous sodium hydroxide solution with a concentration of 1 mol / L; 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.

8. The preparation method of the high-entropy intermetallic compound bifunctional catalyst according to claim 4, wherein, In step S2, the suspension is placed in a reaction kettle and reacted at 130 - 220 °C for 0.5 - 5 h 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 h.

9. The preparation method of the high-entropy intermetallic compound bifunctional catalyst according to claim 4, wherein, In step S3, the heating rate of the annealing treatment is 2 - 10 °C / min, the annealing treatment temperature is 800 - 1000 °C, and the annealing treatment time is 0.5 - 3 h; the reducing atmosphere is hydrogen or a hydrogen-argon mixture.

10. Use of the high-entropy intermetallic compound bifunctional catalyst according to any one of claims 1-3, characterized in that, The high-entropy intermetallic compound bifunctional catalyst is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

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