Preparation method of high-entropy alloy nanowire catalyst for degradation of waste plastic polylactic acid

Abstract

The invention belongs to the technical field of catalyst preparation, focuses on a high-entropy alloy nanowire catalyst, and mainly relates to a preparation method and application of an AuCuAgPtNi catalyst. A one-pot wet chemical method is innovatively adopted, a 4-aminopyridine solvent and metal precursors of gold, copper, silver, platinum and nickel are fully and evenly mixed and placed in an oil bath pot at the temperature of 90 DEG C, then a reducing agent ascorbic acid is rapidly added, after specific reaction time, washing, drying and other operations are sequentially carried out, and the high-entropy alloy nanowire AuCuAgPtNi catalyst can be successfully prepared. The preparation method disclosed by the invention has the remarkable advantages of simple process, simple steps, convenience in operation and the like. In an alkaline environment, the prepared nanowire-shaped high-entropy alloy AuCuAgPtNi catalyst shows extremely excellent catalytic activity and selectivity for catalytic degradation of waste plastic polylactic acid, the waste plastic can be efficiently upgraded and converted into pyruvic acid, a new way is opened up for resource utilization of the waste plastic, and the application prospect is wide. The method has a wide application prospect in the fields of environmental protection and resource recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, focusing on high-entropy alloy nanowire catalysts, and mainly relates to a preparation method and application of an AuCuAgPtNi catalyst.

Background Art

[0002] Due to the extremely strong durability of plastics, fossil-based plastic waste that cannot be decomposed by biological or abiotic means accumulates continuously in landfills or the environment. Among these plastics, polylactic acid accounts for 24% of the global biodegradable polymer market and can decompose into water, carbon dioxide (CO2), and biomass when disposed of in soil. This property makes it a promising environmentally friendly alternative to traditional plastics such as polyethylene and polypropylene. However, the excessive treatment of waste polylactic acid in landfills not only wastes resources but also generates greenhouse gas emissions. To address this challenge, effective methods must be adopted to manage waste plastics. In this context, converting waste plastics into valuable compounds through an electrochemical process can reduce environmental pollution. Previous studies have shown that cobalt selenide supported on nickel foam can oxidize lactic acid, the only hydrolysis product of polylactic acid, to acetate with a Faraday efficiency of 87%. However, the selectivity and activity of the catalyst still need to be further optimized to achieve the upgraded recycling of polylactic acid.

[0003] High-entropy alloys are new multi-metal alloys containing five or more elements, with superior physical and chemical properties compared to traditional alloys. High-entropy alloy catalysts possess unique characteristics such as the thermodynamic high-entropy effect, sluggish diffusion effect, and cocktail effect, and have great potential in electrocatalytic oxidation. The random distribution of multiple elements in the high-entropy alloy phase leads to lattice distortion, and the adjustable electronic structure generated by the element synergy can also improve the electrochemical performance. In addition, precisely regulating the structure of nanoscale materials can effectively improve the electrocatalytic activity. Nanowires can promote electron transfer, improve utilization efficiency, reduce the loss of electrocatalytic surface area, and provide more active sites, showing broad prospects in the field of electrocatalysis. In short, due to the synergistic benefits of morphology, structure, and composition, high-entropy alloy nanowires are expected to become ideal electrocatalysts. Unfortunately, this method has not been effectively applied.

[0004] The present invention uses a green and friendly one-step wet chemical method strategy to prepare a high-performance catalyst, simplifies the synthesis steps, and reduces the introduction of impurities. The prepared high-entropy alloy nanowire AuCuAgPtNi catalyst exhibits excellent electrocatalytic activity and selectivity in the process of generating pyruvic acid.

Summary of the Invention

[0005] [Technical Problems to be Solved]

[0006] Aiming at the deficiencies in the prior art, the present invention provides a preparation method for a high-entropy alloy nanowire metal catalyst.

[0007] One object of the present invention is to uniformly mix metal precursors of gold, copper, silver, platinum and nickel with a 4-aminopyridine solution, and under the action of a reducing agent ascorbic acid, perform an oil bath reaction for a period of time to obtain a high-entropy alloy nanowire AuCuAgPtNi catalyst

[0008] Technical solution:

[0009] A method for synthesizing a high-entropy alloy nanowire AuCuAgPtNi catalyst, comprising the following steps:

[0010] 1. Weigh 0.0475 g of 4-aminopyridine and dissolve it in 7 ml of ultrapure water. Add 1 ml of each of the five precursors, namely chloroauric acid, copper chloride, silver nitrate, platinum acetylacetonate and nickel chloride, to the oil bath at 90 °C in sequence. After shaking well, quickly add 1 ml of 1 M reducing agent ascorbic acid and react for 10 minutes. The molar concentration of the precursors is 20 mM.

[0011] 2. After the reaction is completed, take it out, wash it by centrifugation with ethanol and water, collect the precipitate and dry it for later use.

[0012] Another object of the present invention is to use the prepared high-entropy alloy nanowire AuCuAgPtNi catalyst to upgrade waste plastic polylactic acid into pyruvic acid.

[0013] Experimental method for electrocatalytic oxidation of lactic acid in an alkaline environment:

[0014] Accurately weigh an appropriate amount of the prepared catalyst, place it in a Nafion mixed solution and perform ultrasonic treatment to uniformly disperse the catalyst. Subsequently, use the drop coating method to drop the dispersion onto the surface of the carbon cloth. After the solvent evaporates, a working electrode is successfully prepared. Among them, the Nafion mixed solution is prepared from ultrapure water, ethanol and 5 wt% Nafion solution. In terms of constructing an electrochemical test system, a platinum sheet electrode is selected as the counter electrode, and a Hg / HgO electrode is selected as the reference electrode, and a three-electrode electrochemical test system is jointly constructed with the above-prepared working electrode. Test the linear sweep voltammograms of the catalyst in an alkaline solution and a solution containing lactic acid. The experimental results clearly show that the nanowire-structured high-entropy alloy AuCuAgPtNi catalyst prepared by the present invention exhibits more excellent electrocatalytic activity compared with other control catalysts, and has significant application potential in related electrochemical processes such as lactic acid oxidation reaction.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention:

[0016] The high-entropy alloy nanowire AuCuAgPtNi catalyst prepared by this method exhibits excellent electrocatalytic oxidation activity towards waste plastics in an alkaline environment. This catalyst can efficiently convert PLA into high-value-added chemicals by means of electrochemical oxidation. This not only provides an efficient and environmentally friendly solution for the treatment of waste plastics, but also realizes the effective recycling and reuse of resources, creating new economic value while solving the plastic pollution problem.

Description of the Drawings

[0017] Figure 1 It is the TEM image of the high-entropy alloy nanowire AuCuAgPtNi catalyst.

[0018] Figure 2 It is the XRD pattern of the high-entropy alloy nanowire AuCuAgPtNi catalyst.

[0019] Figure 3 It is the linear sweep voltammogram of the prepared high-entropy alloy nanowire AuCuAgPtNi catalyst in 1 mol / L KOH solution with and without 0.1 M lactic acid.

[0020] Figure 4 It is the NMR spectrum of the product analysis before and after electrolysis of the high-entropy alloy nanowire AuCuAgPtNi catalyst under the conditions of 1 mol / L KOH and 0.1 M lactic acid.

Specific Embodiments

[0021] Combined with the attached Figures 1-4 drawings and the following examples, the present invention will be further described.

[0022] Example 1

[0023] 1. Preparation of the nanowire-structured high-entropy alloy AuCuAgPtNi catalyst

[0024] When synthesizing the high-entropy alloy AuCuAgPtNi nanowires, 1 mL of solutions of chloroauric acid (HAuCl4), copper chloride (CuCl2), silver nitrate (AgNO3), and platinum acetylacetonate (C 10 H 14 O4Pt) with a concentration of 20 mM each, and 1 mL of a nickel chloride (NiCl2) solution with a concentration of 20 mM were added to 7 mL of an aqueous solution containing 0.0475 g of p-aminophenol (4-AP). The mixed solution was heated in an oil bath at 90 °C. Subsequently, 1 mL of an ascorbic acid (AA) solution with a concentration of 0.1 M was added to the reaction mixture and allowed to react for 10 minutes. After the reaction, it was centrifugally washed with water and ethanol, the precipitate was collected and dried. After the sample was dispersed with the mixed solution, it was dropped on a carbon cloth electrode and dried to make an electrode.

[0025] 2. Electrochemical Catalytic Oxidation of Lactic Acid in Alkaline Environment

[0026] Using the high-entropy alloy nanowire AuCuAgPtNi catalyst dropped on a glassy carbon electrode with a cut area of 1 cm 2 as the working electrode, a platinum sheet as the counter electrode, and a saturated Hg / HgO electrode as the reference electrode, a three-electrode electrochemical test system was constructed. The linear sweep voltammograms of the catalyst in 1 mol / L KOH solution with and without 0.1 M lactic acid solution were tested, and the potential window was 1.1 - 2.0 V.

[0027] Figure 1 This is the transmission electron microscope image of the high-entropy alloy nanowire AuCuAgPtNi catalyst in Example 1 of the present invention, showing a nanowire structure.

[0028] Figure 2 This is the XRD pattern of the high-entropy alloy nanowire AuCuAgPtNi catalyst described in Example 1 of the present invention. It can be seen that the diffraction peaks of the high-entropy alloy nanowire AuCuAgPtNi catalyst correspond to the (111), (200), (220), and (311) crystal planes of pure Au (JCPDS-04-0784) respectively.

[0029] Figure 3 This is the linear sweep voltammogram of the high-entropy alloy nanowire AuCuAgPtNi catalyst described in Example 1 of the present invention in 1 mol / L KOH solution with and without 0.1 M lactic acid solution. It can be seen that the prepared high-entropy alloy nanowire AuCuAgPtNi catalyst is thermodynamically more advantageous and has higher activity in catalyzing lactic acid oxidation compared to the oxygen evolution reaction.

[0030] Figure 4 This is the nuclear magnetic resonance hydrogen spectrum of the high-entropy alloy nanowire AuCuAgPtNi catalyst after electrolysis for 10 h in 1 mol / L KOH solution containing 0.1 M lactic acid. It can be seen that the prepared high-entropy alloy nanowire AuCuAgPtNi catalyst has high selectivity for the product pyruvic acid.

Claims

1. A method for preparing a high entropy alloy nanowire metal catalyst, characterized in that The method comprises the steps of upgrading and recycling waste plastic polylactic acid to obtain pyruvic acid: (1) adding tetrachloroauric acid, copper chloride, silver nitrate, platinum acetylacetonate and nickel chloride precursor solutions to a 4-aminopyridine solution in sequence; (2) then quickly adding the reducing agent ascorbic acid; (3) placing the reaction mixture in an oil bath; (4) After the solution obtained in step (3) is allowed to stand, the precipitate is separated and washed and dried in sequence to obtain the nanowire AuCuAgPtNi high entropy alloy metal catalyst.

2. The method for preparing the nanowire AuCuAgPtNi high entropy alloy metal catalyst according to claim 1, characterized in that: The 4-aminopyridine solution in step (1) is prepared by dissolving 0.0475 g of 4-aminopyridine in 7 ml of ultrapure water.

3. The method for preparing the nanowire AuCuAgPtNi high entropy alloy metal catalyst according to claim 1, characterized in that: The molar concentration of each metal precursor in step (1) is 20 mM, and the added volume is 1 ml.

4. The method for preparing the nanowire AuCuAgPtNi high entropy alloy metal catalyst according to claim 2, characterized in that: The ascorbic acid molar concentration in step (2) is 1 M, and the added volume is 1 ml.

5. The method for preparing the nanowire AuCuAgPtNi high entropy alloy metal catalyst according to claim 3, characterized in that: The oil bath temperature in step (3) is 90°C.

6. The method for preparing the nanowire AuCuAgPtNi high entropy alloy metal catalyst according to claim 3, characterized in that: The reaction time of step (3) is 10 minutes.

7. The nanowire AuCuAgPtNi high entropy alloy metal catalyst prepared according to the method of claims 1-6.

8. The use of the nanowire AuCuAgPtNi high entropy alloy metal catalyst according to claim 7, characterized in that: The nanowire AuCuAgPtNi high entropy alloy metal catalyst is used for degrading waste plastic polylactic acid to generate pyruvic acid.

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