Carbon-supported platinum-cobalt-copper multifunctional alloy catalyst as well as preparation method and application thereof

Abstract

The invention provides a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst and a preparation method and application thereof, and belongs to the technical field of energy materials. Wherein the nanocarbon carrier solution is mixed with a chloroplatinic acid solution, a cobalt chloride solution and a copper chloride solution, a sodium hydroxide aqueous solution is added to adjust the pH value, ultrasonic dispersion and stirring are performed to obtain turbid liquid, and the molar ratio of platinum ions to cobalt ions to copper ions is 2: (0.5-1): (0.5-1); then, putting the turbid liquid into a reaction kettle, and reacting at 120-250 DEG C for 1-6 hours to obtain a black colloidal solution; then filtering, washing and drying the black colloidal solution to obtain black powder; and finally, carrying out acid treatment on the black powder, and grinding to obtain the carbon-loaded platinum-cobalt-copper multifunctional alloy catalyst. The catalyst is used for catalyzing an oxygen reduction reaction of a cathode in a hydrogen fuel cell and / or a methanol fuel cell, and / or catalyzing a methanol oxidation reaction of an anode in a direct methanol fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and particularly relates to a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As an important part of energy conversion technology, fuel cells have broad application prospects in many fields such as transportation, distributed power supply, and power grid peak shaving. Hydrogen fuel cells (PEMFCs) and methanol fuel cells (MFCs) are both common fuel cells, which can directly convert the chemical energy of fuels (hydrogen or methanol) into electrical energy through electrochemical reactions, and have the characteristics of high efficiency and low emissions. Carbon-supported platinum-based catalysts have excellent catalytic activity, stability, and electrical conductivity, and are widely used in these two types of fuel cells. For example, the commercially available Pt / C catalyst and PtRu / C catalyst have been realized. However, the existing commercial catalysts cannot solve the problem of the slow kinetic process of the cathode oxygen reduction reaction (ORR) in PEMFCs and MFCs, and the problem of the slow kinetic process of the anodic methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), which hinders the commercialization process of PEMFCs and MFCs.

[0003] In the prior art, the Chinese patent application with the publication number CN119170817A proposed a multi-functional catalyst for direct methanol fuel cells and a preparation method thereof. A carbon cloth loaded with a nitrogen-doped tungsten carbide nanoarray was used as a conductive substrate, and platinum-nickel alloy nanochains were wound on the highly conductive tungsten carbide substrate. This preparation method carried out surface treatment by PECVD, synthesized Pt-Ni alloy polyhedron nanochains through a hydrothermal reaction, and the Pt-Ni alloy polyhedron nanochains were self-adsorbed and loaded on the carbon cloth of the nitrogen-doped tungsten carbide nanoarray, and then calcined and annealed in air, nitrogen, and argon-hydrogen in sequence, and a second PECVD treatment was carried out to obtain a multi-functional catalyst for direct methanol fuel cells. This technical solution improved the performance of the catalyst to a certain extent, but the process was complex and the requirements for equipment were high.

[0004] In the prior art, a Chinese patent application with the publication number CN110010914A proposed a one-dimensional PtCuCo alloy nanochain catalyst applicable to a methanol fuel cell at high temperature and a synthesis method thereof. (1) Metal precursors, namely platinum salt, copper salt and cobalt salt, and sodium dodecyl sulfonate were added to an organic solvent DMAC, and stirred at room temperature until the mixed solution was stirred evenly; (2) After adding formamide solvent as an auxiliary solvent and a reducing agent to step (1), stirring was continued at room temperature until the solution was mixed evenly; (3) The mixed solution obtained in step (2) was transferred to a high-pressure reaction kettle and reacted for 4-16 hours, and the temperature was maintained at 110°C-180°C; (4) The product obtained by the reaction in step (3) was naturally cooled and then washed, and a one-dimensional PtCuCo alloy nanochain catalyst was separated by centrifugation. This catalyst improves the catalytic activity through a one-dimensional chain-like morphology and has outstanding performance in a high-temperature acidic environment, but has a single application scenario and does not have multifunctionality.

[0005] In view of this, it is necessary to design a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, a preparation method and an application thereof to solve the above technical problems. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the present application provides a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, a preparation method and an application thereof. First, a nano-carbon carrier solution is uniformly mixed with three metal ions of platinum, cobalt and copper. By using a solvothermal chemistry method, through thermal decomposition, redox and coordination reactions under alkaline conditions, the three metal ions form alloy nanoparticles, and then filtration, washing and drying are carried out to obtain black powder. Finally, the black powder is acid-treated to obtain a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst. The ORR half-wave potential of the carbon-supported platinum-cobalt-copper multifunctional alloy catalyst provided by the present application exceeds that of a commercial Pt / C catalyst by 76 mV, and the initial mass-specific activity reaches 1.51 A mgPt -1 , which is more than 12 times that of commercial Pt / C (0.12 A mgPt-1). After 30,000 potential cycles, the mass-specific activity only decreases by 1.2%, and the methanol oxidation peak current density is 59.32 mA / cm 2 , which is significantly higher than that of a commercial Pt / C catalyst (33.47 mA / cm 2 ) and a commercial PtRu / C catalyst (51.96 mA / cm 2 ). This catalyst can be used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the oxygen reduction reaction at the cathode in a methanol fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell, and has multifunctionality.

[0007] In the first aspect, an embodiment of the present application provides a preparation method of a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, including the following steps: S1. Add the nano-carbon carrier to a solvent and disperse it evenly by ultrasonic treatment. Then, add chloroplatinic acid solution, cobalt chloride solution, and copper chloride solution. Next, add an aqueous sodium hydroxide solution to adjust the pH value to 10 - 12, and perform ultrasonic dispersion and stirring to obtain a suspension. S2. Place the suspension obtained in step S1 into a reaction kettle and react at 120 - 250 °C for 1 - 6 h to obtain a black colloidal solution. S3. Filter, wash, and dry the black colloidal solution obtained in step S2 to obtain a black powder. S4. Perform acid treatment on the black powder obtained in step S3, and then grind it to obtain a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst.

[0008] Further, in step S1, the solvent is deionized water, absolute ethanol, or ethylene glycol; in step S1, the chloroplatinic acid solution, cobalt chloride solution, and copper chloride solution are all prepared by dissolving the corresponding metal salts in ethylene glycol.

[0009] Further, the concentration of the chloroplatinic acid solution is 0.01 - 0.5 mol / L, the concentration of the cobalt chloride is 0.05 - 0.5 mol / L, and the concentration of the copper chloride is 0.05 - 0.5 mol / L.

[0010] Further, in the suspension of step S1, the molar ratio of platinum ions to cobalt ions and copper ions is 2:(0.5 - 1):(0.5 - 1).

[0011] Further, in step S1, after adding the nano-carbon carrier to the solvent, perform ultrasonic treatment for 30 - 60 min; in step S1, after adding the aqueous sodium hydroxide solution, perform ultrasonic treatment for 10 - 15 min; in step S1, the stirring time is 0.5 - 6 h, and the rotation speed is 200 - 2000 rpm.

[0012] Further, the nano-carbon carrier is graphitized carbon black (GCB), nano-carbon black, carbon nanotubes, or graphene.

[0013] Further, in step S3, the drying temperature is 50 - 80 °C, and the drying time is 5 - 10 h.

[0014] Further, the acid treatment in step S4 specifically means placing the black powder in an acidic solution with a concentration of 0.1 - 1 mol / L, treating it at 60 °C for 2 - 10 h, then performing suction filtration, washing, and drying at 50 - 80 °C; wherein, the acidic solution is one or a mixture of sulfuric acid solution, hydrochloric acid solution, perchloric acid solution, and nitric acid solution.

[0015] Second aspect, an embodiment of the present application provides a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, which is prepared by using any one of the preparation methods in the foregoing technical solutions; the loading amount of the alloy nanoparticles in the carbon-supported platinum-cobalt-copper multifunctional alloy catalyst is 20-70 wt%, and the particle size of the alloy nanoparticles is 2-5 nm.

[0016] Third aspect, an embodiment of the present application provides an application of a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, and the carbon-supported platinum-cobalt-copper multifunctional alloy catalyst described in the foregoing technical solutions is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the oxygen reduction reaction at the cathode in a methanol fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0017] The beneficial effects of the present application are as follows: The present application provides a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, a preparation method thereof, and an application. First, a nano-carbon carrier solution is uniformly mixed with platinum, cobalt, and copper metal ions. Using the solvothermal chemical method, through thermal decomposition, redox, and coordination reactions under alkaline conditions, the three metal ions form alloy nanoparticles, and then filtration, washing, and drying are carried out to obtain a black powder. Finally, the black powder is acid-treated to obtain a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst.

[0018] (1) In the present application, the electronic structure of platinum is changed by simultaneously introducing cobalt and copper. Through the redistribution of electrons, the position of the d-band center of platinum is adjusted, thereby affecting the adsorption and activation of oxygen molecules. Appropriately reducing the position of the d-band center of platinum is beneficial to weakening the binding strength between platinum and oxygen adsorption species (such as OH, OOH), thereby reducing the energy barrier of the oxygen reduction reaction and improving the catalytic activity. Copper acts together with platinum and cobalt to form more effective active sites, thereby further enhancing the activity and selectivity of the methanol oxidation reaction.

[0019] (2) The introduction of copper will cause a certain strain in the platinum lattice, thereby changing the distance and arrangement mode between platinum atoms, that is, changing the geometric structure of the alloy nanoparticles. On the one hand, the change in the geometric structure helps to optimize the distribution of active sites, enabling more platinum atoms to participate in the oxygen reduction reaction and improving the activity and stability of the catalyst. On the other hand, CO intermediates are generated during the methanol oxidation process. These intermediates are easily adsorbed and accumulated on platinum atoms, resulting in catalyst poisoning. The change in the geometric structure caused by the introduction of copper will reduce the binding strength between CO and platinum, thereby reducing the adsorption amount of CO on the platinum surface and improving the anti-poisoning ability of the catalyst. This is because the introduction of copper helps the dissociation of water molecules on the catalyst surface to generate more hydroxyl groups. These hydroxyl groups can combine with CO intermediates to form intermediate species such as COOH, thereby promoting the oxidation and removal of CO and improving the efficiency of the methanol oxidation reaction.

[0020] (3) The present application rationally designs the ratios of platinum, cobalt, and copper, and uses the solvothermal chemical method to treat at a temperature of 120 - 250 °C for 1 - 6 h. Through thermal decomposition, redox, and coordination reactions under alkaline conditions, platinum-cobalt-copper alloy nanoparticles with a particle size of 2 - 5 nm are formed. Then, the catalyst is surface-activated and its structure is optimized through acid treatment, that is, the surface morphology of the catalyst is adjusted, the specific surface area is increased, and more Pt active sites are exposed to enhance the activities of the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Finally, a multifunctional catalyst that can be used for the oxygen reduction reaction catalysis at the cathode in a hydrogen fuel cell and / or the oxygen reduction reaction catalysis at the cathode in a methanol fuel cell and / or the methanol oxidation reaction catalysis at the anode in a direct methanol fuel cell is obtained. The preparation method provided by the present application has a short operation process and can be prepared in batches, which is suitable for industrial production.

[0021] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present application more obvious and understandable, the following specific embodiments of the present application are specifically given. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 XRD pattern of the carbon-supported platinum-cobalt-copper multifunctional alloy catalyst prepared in Example 1 of the present application; Figure 2 TEM image of the carbon-supported platinum-cobalt-copper multifunctional alloy catalyst prepared in Example 1 of the present application; Figure 3 Comparison diagram of the rotating disk polarization curves of the commercial Pt / C catalyst and the catalyst prepared in Example 1 of the present application in an acidic medium; Figure 4 Comparison diagram of the polarization curves and cyclic voltammograms of the commercial Pt / C catalyst and the catalyst prepared in Example 1 of the present application before and after 30,000 potential cycles, where (A) is the comparison diagram of the polarization curves and (B) is the comparison diagram of the cyclic voltammograms; Figure 5 Comparison diagram of the MOR cyclic voltammograms of the commercial Pt / C catalyst, commercial PtRu / C catalyst, and the catalyst prepared in Example 1 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying 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.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this 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 indicating the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0027] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of this application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0028] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: 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 this application can be understood according to specific circumstances.

[0029] Commercial catalysts cannot simultaneously solve the problem of the slow kinetic process of the cathode oxygen reduction reaction (ORR) in PEMFC and MFC, as well as the problem of the slow kinetic process of the anodic methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFC). The existing preparation processes of multifunctional catalysts are complex and require high equipment requirements.

[0030] To solve the above technical problems, the present application provides a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, a preparation method thereof, and an application thereof. First, a nano-carbon carrier solution is uniformly mixed with platinum, cobalt, and copper metal ions, and then through a solvothermal chemical method, through thermal decomposition, redox, and coordination reactions under alkaline conditions, the three metal ions form alloy nanoparticles, and then filtration, washing, and drying are performed to obtain a black powder. Finally, the black powder is acid-treated to obtain a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst. By using copper and cobalt to change the electronic structure and geometric structure of the alloy nanoparticles, the activity and stability of the catalyst are improved, and at the same time, the anti-poisoning ability of the catalyst is enhanced.

[0031] In a first aspect, an embodiment of the present application provides a preparation method of a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, including the following steps: S1, adding a nano-carbon carrier into a solvent and ultrasonically dispersing it uniformly, then adding a chloroplatinic acid solution, a cobalt chloride solution, and a copper chloride solution, and then adding an aqueous sodium hydroxide solution to adjust the pH value to 10-12, ultrasonically dispersing, and stirring to obtain a suspension.

[0032] In the embodiment of the present application, the solvent is deionized water, absolute ethanol, or ethylene glycol. The chloroplatinic acid solution, the cobalt chloride solution, and the copper chloride solution are all prepared by dissolving the corresponding metal salts (i.e., chloroplatinic acid, cobalt chloride, and copper chloride) in ethylene glycol. Among them, the concentration of the chloroplatinic acid solution is 0.01-0.5 mol / L, the concentration of cobalt chloride is 0.05-0.5 mol / L, and the concentration of copper chloride is 0.05-0.5 mol / L.

[0033] In the embodiment of the present application, in the suspension of step S1, the atomic mass ratio of platinum ions to cobalt ions and copper ions is 2:(0.5-1):(0.5-1).

[0034] In the embodiment of the present application, after adding the nano-carbon carrier into the solvent, ultrasonication is performed for 30-60 min, and the nano-carbon carrier is graphitized carbon black (GCB), nano-carbon black, carbon nanotubes, or graphene.

[0035] In the embodiment of the present application, after adding the aqueous sodium hydroxide solution, ultrasonication is performed for 10-15 min.

[0036] In the embodiment of the present application, the stirring time is 0.5-6 h, and the stirring speed is 200-2000 rpm.

[0037] S2, placing the suspension obtained in step S1 in a reaction kettle and reacting at 120-250 °C for 1-6 h to obtain a black colloidal solution.

[0038] S3, filtering, washing, and drying the black colloidal solution obtained in step S2 to obtain a black powder.

[0039] In the embodiment of the present application, the drying temperature is 50 - 80 °C, and the drying time is 5 - 10 h.

[0040] S4. Acid-treat the black powder obtained in step S3, and then grind it for 0.5 - 2 h to obtain a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst.

[0041] Specifically, the acid treatment means placing the black powder in an acidic solution with a concentration of 0.1 - 1 mol / L, treating it at 60 °C for 2 - 10 h, then performing suction filtration, washing, and drying at 50 - 80 °C. Among them, the acidic solution is one or a mixture of sulfuric acid solution, hydrochloric acid solution, perchloric acid solution, and nitric acid solution.

[0042] In a second aspect, the embodiment of the present application provides a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst, which is prepared by using the preparation method of any one of the foregoing technical solutions. The loading amount of the alloy nanoparticles in the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst is 20 - 70 wt%, and the particle size of the alloy nanoparticles is 2 - 5 nm.

[0043] In a third aspect, the embodiment of the present application provides an application of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst, and uses the foregoing carbon-supported platinum-cobalt-copper multi-functional alloy catalyst for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the oxygen reduction reaction at the cathode in a methanol fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

[0044] In the embodiment of the present application, the half-wave potential of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst is 76 mV higher than that of the commercial Pt / C catalyst, the mass-specific activity is more than 12 times that of the commercial Pt / C catalyst, and the peak current density in the electrocatalytic oxidation of methanol is higher than that of the commercial Pt / C catalyst and the commercial PtRu / C catalyst.

[0045] The following lists some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation to the present application. For those where specific technologies or conditions are not indicated in the embodiments, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0046] Example 1 Example 1 provides a preparation method of a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst, including the following steps: S1. Add 720 mg of acidified graphitized carbon black to 1100 mL of ethylene glycol, and ultrasonicate for 30 min to disperse evenly. Then, add 240 mL of 0.01 mol / L chloroplatinic acid solution, 12 mL of 0.1 mol / L cobalt chloride solution, and 12 mL of 0.1 mol / L copper chloride solution (ethylene glycol is used as the solvent for all three solutions). After adding 30 mL of 0.1 mol / L sodium hydroxide aqueous solution, ultrasonicate for 10 min and stir for 30 min to obtain a suspension; S2. Place the suspension obtained in step S1 into a 2000 mL reactor and react at 190 °C for 5 h to obtain a black colloidal solution; S3. Vacuum filter the black colloidal solution obtained in step S2, wash it with deionized water, dry it overnight (8 h) at 65 °C, and then repeat the washing-drying step three times to obtain a black powder.

[0047] S4. Place the black powder obtained in step S3 into 0.1 mol / L perchloric acid (acid solution), stir at 60 °C for 5 h, filter, wash with deionized water, dry at 65 °C, and then grind in a mortar for 30 min to obtain a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst.

[0048] The carbon-supported platinum-cobalt-copper multi-functional alloy catalyst prepared in Example 1 was characterized by X-ray diffraction (XRD). The obtained XRD pattern is shown in Figure 1 It can be seen that characteristic diffraction peaks of Pt, namely (111), (200), (220), (311), and (222), appear near 39.763°, 46.243°, 67.454°, 81.286°, and 85.712°. By comparing with the standard card, it can be seen that the main peak of platinum shifts to the right, indicating that platinum has been successfully alloyed with copper and cobalt elements with smaller atomic radii.

[0049] The carbon-supported platinum-cobalt-copper multi-functional alloy catalyst prepared in Example 1 was characterized by transmission electron microscopy (TEM). The obtained TEM image is shown in Figure 2 It can be seen that dark alloy nanoparticles are evenly distributed on the carbon support without agglomeration. After measurement, the average particle size of the alloy nanoparticles is 3.28 nm.

[0050] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in Example 1, the atomic mass ratio of platinum, cobalt, and copper is 2:1:1, while in Comparative Example 1, the atomic mass ratio of platinum, cobalt, and copper is 1:1:1.

[0051] Specifically, in step S1, 720 mg of acidified graphitized carbon black was added to 1100 mL of ethylene glycol, and ultrasonicated for 30 min to disperse evenly. Then, 120 mL of 0.01 mol / L chloroplatinic acid solution, 12 mL of 0.1 mol / L cobalt chloride solution, and 12 mL of 0.1 mol / L copper chloride solution (ethylene glycol was used as the solvent for chloroplatinic acid solution, cobalt chloride solution, and copper chloride solution) were added. After adding 30 mL of 0.1 mol / L sodium hydroxide aqueous solution, it was ultrasonicated for 10 min and stirred for 30 min to obtain a suspension. The others were the same as in Example 1 and will not be elaborated here.

[0052] Comparative Example 2 The difference between Comparative Example 2 and Example 1 was that a preparation method of a carbon-supported platinum-cobalt-tungsten alloy catalyst was provided, that is, copper chloride in Example 1 was replaced with tungsten hexacarbonyl. The others were the same as in Example 1 and will not be elaborated here.

[0053] The rotating disk polarization curves of commercial Pt / C catalyst and the catalyst prepared in Example 1 in 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. Please refer to Figure 3 As shown, it was the comparison diagram of the rotating disk polarization curves after i-R compensation. It could be seen that the half-wave potential of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst prepared in Example 1 exceeded that of the commercial Pt / C catalyst by 76 mV.

[0054] The polarization curves and cyclic voltammograms of commercial Pt / C catalyst, the catalysts prepared in Example 1 and Comparative Examples 1-2 before and after 30,000 potential cycles at a scan rate of 100 mA / s in the range of 0.6 V - 0.95 V (vs. RHE) were tested, and the mass-specific activity and electrochemically active surface area were calculated at a fixed polarization potential of 0.9 V. Details were shown in Table 1.

[0055] Table 1. Mass-specific activity and electrochemically active surface area calculated at a fixed polarization potential of 0.9 V Please refer to Figure 4 As shown, (A) was the comparison diagram of polarization curves, and (B) was the comparison diagram of cyclic voltammograms. It could be seen that the mass-specific activity of the catalyst prepared in Example 1 reached 1.51 A mg Pt -1 , which was 12.6 times that of the commercial Pt / C catalyst (0.12 A mg Pt -1After 30,000 cycles of potential cycling, the mass specific activity decreased by only 1.2%, which is significantly better than that of commercial Pt / C catalyst (a decrease of 58%), indicating that the catalyst prepared in Example 1 has excellent stability. From Table 1, it can be seen that the activity and stability of the catalysts prepared in Comparative Examples 1-2 are significantly lower than those in Example 1. This is because in Comparative Example 1, the amounts of cobalt and copper were increased, resulting in a decrease in the relative content of platinum in the catalyst, thereby reducing the electrochemical performance of the catalyst. In Comparative Example 2, copper was replaced by tungsten. The alloying difficulty between tungsten and platinum is higher than that between copper and platinum, and the melting point of tungsten (3422 °C) is much higher than that of platinum (1768 °C), which easily leads to incomplete alloying or phase separation, forming a non-uniform structure, and thus reducing the number of exposed active sites. In addition, the catalytic activity of platinum is closely related to the position of its d-band center. When copper is alloyed with platinum, its small atomic radius and high electronegativity difference can optimize the d-band center position of Pt, weaken the too strong adsorption of platinum to oxygen intermediates (such as OOH, OH), thereby enhancing the kinetics of the oxygen reduction reaction (ORR). However, tungsten has a larger atomic radius and a significant difference in electronic structure from platinum, which may cause the d-band center of platinum to shift excessively downward or upward, breaking the balance of the adsorption strength of oxygen species and reducing the reaction activity.

[0056] Cyclic voltammetry (CV) was used to perform cyclic voltammetry tests on the electrocatalytic oxidation of methanol (MOR) of commercial Pt / C catalyst, commercial PtRu / C catalyst, the catalysts prepared in Example 1 and Comparative Examples 1-2. Among them, the scanning voltage range was 0.3 V - 0.9 V (vs. RHE), the scanning rate was 50 mV / s, and the electrolyte was 1.0 mol / L KOH + 1.0 mol / L CH3OH. The comparison graph of the cyclic voltammetry curves of the electrocatalytic oxidation of methanol (MOR) is shown in Figure 5 as shown, and the specific oxidation peak current density is shown in Table 2.

[0057] Table 2. Oxidation peak current density obtained from cyclic voltammetry tests of electrocatalytic oxidation of methanol (MOR) It can be seen that two oxidation peaks appeared in all the catalysts. The oxidation peak current densities of commercial Pt / C catalyst, commercial PtRu / C catalyst, and the catalysts obtained in Example 1 and Comparative Examples 1-2 are 33.47 mA / cm 2 , 51.96 mA / cm 2 , 59.32 mA / cm 2 , 48.73 mA / cm 2 , 35.81 mA / cm 2 respectively. The peak current density of the catalyst obtained in Example 1 for catalyzing methanol is significantly higher, indicating that the interaction between platinum and cobalt and copper improves the electrooxidation performance of the catalyst for methanol.

[0058] For the platinum-cobalt-tungsten catalyst prepared in Comparative Example 2, tungsten is prone to form stable tungsten oxide (such as WO3) under acidic conditions. However, WO3 has poor conductivity and weak hydroxyl generation ability, making it difficult to effectively remove CO, and the catalyst surface will still be gradually poisoned. And Cu is prone to form surface oxides (such as CuO x , 0 < x < 1) in an acidic environment. These species can promote the dissociation of water at low potentials, and then provide hydroxyl groups (OH) to oxidize the adsorbed CO intermediate (CO + OH → CO 2 + H + + e - ), significantly alleviating Pt poisoning. In addition, the electronic effect of Pt-Co-Cu makes the adsorption strength of CO moderate, which not only ensures the adsorption and activation of methanol molecules but also allows CO to be oxidized and desorbed at a lower potential. While for Pt-Co-W, the strong electronic effect of W may lead to too strong or too weak CO adsorption: too strong adsorption will exacerbate poisoning, and too weak adsorption will not be able to effectively activate methanol molecules.

[0059] In summary, the present application provides a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, its preparation method and application. A multifunctional catalyst that can be used for the oxygen reduction reaction catalysis at the cathode in a hydrogen fuel cell and / or the oxygen reduction reaction catalysis at the cathode in a methanol fuel cell and / or the methanol oxidation reaction catalysis at the anode in a direct methanol fuel cell is prepared by a solvothermal chemical method. This catalyst has excellent electrocatalytic activity and stability. Its ORR half-wave potential exceeds that of commercial Pt / C catalyst by 76 mV, and the initial mass-specific activity reaches 1.51 A mgPt -1 , which is more than 12 times that of commercial Pt / C (0.12 A mgPt -1 ). After 30,000 potential cycles, the mass-specific activity only decreases by 1.2%, and the methanol oxidation peak current density is 59.32 mA / cm 2 , which is higher than that of commercial Pt / C catalyst (33.47 mA / cm 2 ) and commercial PtRu / C catalyst (51.96 mA / cm 2 ).

[0060] 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 function and effect as the technical idea within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A preparation method of a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, characterized in that, It includes the following steps: S1. Add the nano-carbon carrier into a solvent and ultrasonically disperse it evenly. Then, add chloroplatinic acid solution, cobalt chloride solution and copper chloride solution. Next, add an aqueous sodium hydroxide solution to adjust the pH value to 10 - 12, ultrasonically disperse and stir to obtain a suspension; S2. Place the suspension obtained in step S1 into a reaction kettle and react at 120 - 250 °C for 1 - 6 h to obtain a black colloidal solution; S3. Filter, wash and dry the black colloidal solution obtained in step S2 to obtain a black powder; S4. Perform acid treatment on the black powder obtained in step S3, and then grind it to obtain a carbon-supported platinum-cobalt-copper multi-functional alloy catalyst.

2. The preparation method of the carbon-supported platinum-cobalt-copper multifunctional alloy catalyst according to claim 1, wherein, In step S1, the solvent is deionized water, absolute ethanol or ethylene glycol; in step S1, the chloroplatinic acid solution, cobalt chloride solution and copper chloride solution are all prepared by dissolving the corresponding metal salts in ethylene glycol.

3. The preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst according to claim 2, wherein The concentration of the chloroplatinic acid solution is 0.01 - 0.5 mol / L, the concentration of the cobalt chloride is 0.05 - 0.5 mol / L, and the concentration of the copper chloride is 0.05 - 0.5 mol / L.

4. The preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst according to claim 1, characterized in that, In the suspension of step S1, the molar ratio of platinum ions to cobalt ions and copper ions is 2:(0.5 - 1):(0.5 - 1).

5. The preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst according to claim 2, characterized in that, In step S1, ultrasonically disperse for 30 - 60 min after adding the nano-carbon carrier into the solvent; ultrasonically disperse for 10 - 15 min after adding the aqueous sodium hydroxide solution; in step S1, the stirring time is 0.5 - 6 h and the rotation speed is 200 - 2000 rpm.

6. The preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst according to claim 5, characterized in that The nano-carbon carrier is graphitized carbon black (GCB), nano-carbon black, carbon nanotube or graphene.

7. The preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst according to claim 1, characterized in that, In step S3, the drying temperature is 50 - 80 °C and the drying time is 5 - 10 h.

8. The preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst according to claim 1, characterized in that, The acid treatment in step S4 specifically means placing the black powder in an acidic solution with a concentration of 0.1 - 1 mol / L, treating it at 60 °C for 2 - 10 h, then performing suction filtration, washing, and drying at 50 - 80 °C; wherein, the acidic solution is one or a mixture of sulfuric acid solution, hydrochloric acid solution, perchloric acid solution, nitric acid solution.

9. A carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, characterized in that, It is prepared by using the preparation method of the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst described in any one of claims 1 - 8; the loading amount of the alloy nanoparticles in the carbon-supported platinum-cobalt-copper multi-functional alloy catalyst is 20 - 70 wt%, and the particle size of the alloy nanoparticles is 2 - 5 nm.

10. Application of a carbon-supported platinum-cobalt-copper multifunctional alloy catalyst, characterized in that, The carbon-supported platinum-cobalt-copper multi-functional alloy catalyst described in claim 9 is used for catalyzing the oxygen reduction reaction at the cathode in a hydrogen fuel cell and / or catalyzing the oxygen reduction reaction at the cathode in a methanol fuel cell and / or catalyzing the methanol oxidation reaction at the anode in a direct methanol fuel cell.

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