A multimetallic heterostructure electrocatalyst, preparation method and application thereof in plastic recycling

Abstract

The application discloses a kind of multi-metal heterostructure electrocatalyst, preparation method and its application in plastic recycling, belong to electrochemical catalysis field, the catalyst includes grown on foam metal matrix hydroxide and metal heterostructure, the method uses soluble metal salt as raw material, and multi-metal heterostructure electrocatalyst is prepared using two-step electrodeposition method.The catalyst can be applied to the process of electrocatalytic upgrading and recycling PET derived EG in alkaline solution, it has very low overpotential and higher faradic efficiency for PET hydrolysate electrooxidation, and has good catalytic stability.Multi-metal heterostructure electrocatalyst prepared using the method can also be applied to the upgrading and recycling of other plastic derivatives, and has good application prospect in the field of plastic derivative upgrading and recycling.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis technology, and relates to a multi-metal heterostructure electrocatalyst, its preparation method, and its application in plastic recycling. Background Technology

[0002] Polyethylene terephthalate (PET) is a widely used polyester plastic with an annual production capacity exceeding 70 million tons. This versatile material is used in many industries, including packaging and textiles. However, more than four-fifths of PET plastic is not recycled but is directly discarded into the environment, resulting in less than one-fifth of PET being recovered through mechanical or chemical methods. Due to the significant decline in the quality and low utilization rate of recycled materials, mechanical recycling methods are often preferred. Among various chemical methods such as pyrolysis, hydrolysis, and alcoholysis, alkaline hydrolysis is particularly effective in breaking down PET into ethylene glycol (EG) monomers and terephthalate monomers under mild conditions. In particular, terephthalates can be converted to terephthalic acid through a simple pH adjustment method, which is then easily separated. Due to the high boiling point, high viscosity, and high water solubility of EG, subsequent separation often becomes complex and laborious. In recent years, scientists have been actively researching suitable methods to separate and enhance ethylene glycol.

[0003] In recent years, electrochemical methods have attracted much attention due to their inherent advantages such as reliable power supply, mild operating conditions, high reaction efficiency, and high yield. This process revolves around the catalytic hydrolysis of PET, with EG considered a key platform molecule for conversion into commercial chemicals. This method electro-oxidizes EG in water to generate high-value products such as glycolic acid and formate, and produces green hydrogen. Due to its unique chemical properties, glycolic acid shows great potential in various fields, including adhesives, metal cleaning, textiles, leather processing, and health products. Notably, glycolic acid has been widely used in the synthesis of biodegradable polymers and plastics. Therefore, the electro-oxidation method for converting ethylene glycol to glycolic acid offers advantages such as high efficiency and good selectivity. The success of this electrochemical strategy is crucial for achieving high efficiency and selectivity in electrocatalysts. Noble metal catalysts such as palladium exhibit excellent catalytic activity in the ethylene glycol oxidation reaction (EGOR) and have been shown to favor the formation of the C2 product glycolic acid. Furthermore, constructing heterojunction interface structures composed of noble metals (Pd, Au, etc.) and non-noble metals can reduce the use of noble metals, lower costs, and improve catalyst performance. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-metal heterostructure electrocatalyst, its preparation method, and its application in plastic recycling.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a multi-metal heterostructure electrocatalyst, comprising the following steps;

[0007] Step 1: Prepare a nickel nitrate solution with a concentration of 0.01-0.2 mol / L as the first electrolyte;

[0008] Step 2: Place the cleaned nickel foam in the first electrolyte and deposit it using a constant potential deposition method;

[0009] Step 3: Prepare a mixed solution of sodium chloride and chloropalladium acid with concentrations of 0.1 mol / L and 1-5 mmol / L, respectively, as the second electrolyte;

[0010] Step 4: Immerse the material obtained in Step 2 into the second electrolyte in Step 3 and perform electrodeposition using the constant potential transition method to obtain a multi-metal heterostructure electrocatalyst.

[0011] Preferably, in step one, the concentration of the nickel nitrate solution is 0.1 mol / L.

[0012] Preferably, in step two, the potential for constant potential deposition is -1.0V vs. SCE, and the deposition time is 5 minutes.

[0013] Preferably, in step four, electrodeposition is performed using a constant potential transition method, with the potential and time being -0.6V vs. SCE for 10s, and -0.2V vs. SCE for 10s, repeated three times.

[0014] In a second aspect, the present invention provides a multi-metal heterostructure electrocatalyst prepared by the method described in the first aspect.

[0015] Thirdly, the present invention provides an application of the multi-metal heterostructure electrocatalyst prepared by the method described in the first aspect in the recycling of plastics.

[0016] Compared with existing technologies, this invention prepares a multi-metal heterostructure electrocatalyst through a two-step electrodeposition method, which greatly improves its catalytic activity and stability in alkaline solutions, and together promotes the electrooxidation of ethylene glycol to glycolic acid. Attached Figure Description

[0017] Figure 1 These are SEM images of Pd / Ni(OH)2 / NF(a) prepared in Example 2 and Ni(OH)2 / NF(b) prepared in Example 1 of this invention.

[0018] Figure 2 These are TEM images of Pd / Ni(OH)2 / NF(a) prepared in Example 2 and Ni(OH)2 / NF(b) prepared in Example 1 of this invention.

[0019] Figure 3These are the XRD patterns of Pd / Ni(OH)2 / NF(a) prepared in Example 2 and Ni(OH)2 / NF(b) prepared in Example 1 of this invention.

[0020] Figure 4 These are the fine XPS spectra of Pd / Ni(OH)2 / NF(a) prepared in Example 2 and Ni(OH)2 / NF(b) prepared in Example 1 of this invention.

[0021] Figure 5 The LSV polarization curves of Pd / Ni(OH)2 / NF prepared in Example 2 of this invention, Ni(OH)2 / NF prepared in Example 1, and Pd / NF prepared in Example 3 are compared with those of commercial Pd / C in KOH solution containing EG.

[0022] Figure 6 This is a stability test diagram of the Pd / Ni(OH)2 / NF containing EG in KOH solution prepared in Example 2 of this invention.

[0023] Figure 7 This is a comparison chart of the Faraday efficiency of Pd / Ni(OH)2 / NF prepared in Example 2 of the present invention for recovering PET-derived EG at different potentials in KOH solution containing EG. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0025] The remarkable performance of the catalyst prepared in the oxidation of PET hydrolysate can be attributed to its unique structural advantages, particularly the interfacial heterostructure integrated within the Pd particles and the strong interfacial electronic interactions between Pd and Ni(OH)₂. This catalyst exhibits extremely low overpotential and high Faradaic efficiency, at 10 mA / cm². 2 and 100mA / cm 2 At current densities of 0.53 V and 0.79 V, ethylene glycol oxidation requires only 0.53 V and 0.79 V. Compared to RHE, it achieves a Faraday efficiency as high as 94.2% at 1.2 V. Notably, this heterostructured metal electrocatalyst can maintain stable electrolysis for more than 20 hours.

[0026] Example 1

[0027] (1) Take 5 mmol of Ni(NO3)2·6H2O and add it to 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a homogeneous aqueous solution.

[0028] (2) Using a 1×2cm cut nickel foam as the working electrode, a constant potential deposition of -1.0V vs. SCE was performed in the solution prepared in step (1) for 5 minutes.

[0029] (3) The NF obtained in step (2) was washed several times with deionized water and ethanol, and then dried in a vacuum at 60°C for 8 hours; the product obtained was Ni(OH)2 / NF.

[0030] Figure 1 SEM testing determined the loading mode of Ni(OH)2. Figure 2 TEM testing and Figure 3 XRD tests confirmed the successful loading of Ni(OH)2. Figure 4 XPS testing determined the chemical state of Ni on the catalyst surface. Figure 5 The LSV test determined its electrochemical performance.

[0031] Example 2

[0032] (1) Take 5 mmol of Ni(NO3)2·6H2O and add it to 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a homogeneous aqueous solution.

[0033] (2) Using a 1×2cm cut nickel foam as the working electrode, a potentiostatic deposition of -1.0V vs. SCE was performed in the solution prepared in step (1) for 5 minutes.

[0034] (3) Take 5 mmol of NaCl and 0.25 mmol of H2PdCl4 and add them to 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a homogeneous aqueous solution.

[0035] (4) Using the NF obtained in step (2) as the working electrode, a constant potential transition is used in the solution prepared in step (3). The potential and time are -0.6V vs. SCE for 10s, -0.2V vs. SCE for 10s, and repeated three times.

[0036] (5) The NF obtained in step (4) was washed several times with deionized water and ethanol, and then dried in a vacuum at 60°C for 8 hours; the product obtained was Pd / Ni(OH)2 / NF.

[0037] Figure 1 SEM tests determined the loading mode of Pd / Ni(OH)2. Figure 2TEM testing and Figure 3 XRD tests confirmed the successful loading of Pd / Ni(OH)2. Figure 4 XPS testing determined the chemical states of Ni and Pd elements on the Pd / Ni(OH)2 / NF surface.

[0038] Figure 5 Electrochemical measurements were performed using a standard three-electrode electrolytic cell connected to an electrochemical workstation. The Pd / Ni(OH)₂ / NF electrode synthesized in Example 2 was used as the working electrode. A graphite rod was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. The measurements were obtained using formula E. RHE＝ E Hg / HgO The potential was converted to a standard hydrogen electrode at +0.059pH+E0(0.098). The EG oxidation performance of the prepared Pd / Ni(OH)2 / NF was tested by linear sweep voltammetry, with commercial Pd / C used as a control sample at 10 mA / cm². 2 and 100mA / cm 2 At the given current density, the voltage required for ethylene glycol oxidation is only 0.53V and 0.79vs.RHE. Figure 6 The stability of the catalyst was tested, and it was found to maintain stable electrolysis for more than 20 hours. Figure 7 The Faradaic efficiency of Pd / Ni(OH)2 / NF catalyzing EG was determined, achieving a high Faradaic efficiency of 94.2% at 1.2V. This demonstrates extremely low overpotential and high Faradaic efficiency.

[0039] Example 3

[0040] (1) Take 5 mmol of NaCl and 0.15 mmol of H2PdCl4 and add them to 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a homogeneous aqueous solution.

[0041] (2) Using a piece of nickel foam cut to 1×2cm as the working electrode, a constant potential transition was used in the solution prepared in step (1). The potential and time were -0.6V vs. SCE for 10s, -0.2V vs. SCE for 10s, and repeated three times.

[0042] (3) The NF obtained in step (2) was washed several times with deionized water and ethanol, and then dried in a vacuum at 60°C for 8 hours; the product obtained was Pd / NF. Figure 5 The LSV test determined the electrochemical performance of Pd / NF.

[0043] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the present invention, and all of these should be considered to fall within the scope of patent protection determined by the submitted claims.

Claims

1. A method for preparing a multi-metal heterostructure electrocatalyst, characterized in that, Includes the following steps; Step 1: Prepare a nickel nitrate solution with a concentration of 0.01~0.2 mol / L as the first electrolyte; Step 2: Place the cleaned nickel foam in the first electrolyte and deposit it using a constant potential deposition method; Step 3: Prepare mixed solutions of sodium chloride and chloropalladium acid with concentrations of 0.1 mol / L and 1~5 mmol / L, respectively, as the second electrolyte; Step 4: Immerse the material obtained in Step 2 into the second electrolyte in Step 3 and perform electrodeposition using the constant potential transition method. The potential and time are -0.6 V vs. SCE for 10 s and -0.2 V vs. SCE for 10 s, and repeat three times to obtain a multi-metal heterostructure electrocatalyst.

2. The method as described in claim 1, characterized in that, In step one, the concentration of the nickel nitrate solution is 0.1 mol / L.

3. The method as described in claim 1, characterized in that, In step two, the potential for constant potential deposition is -1.0 V vs. SCE, and the deposition time is 5 min.

4. A multi-metal heterostructure electrocatalyst prepared by the method according to any one of claims 1-3.

5. The application of a multi-metal heterostructure electrocatalyst prepared by the method according to any one of claims 1-3 in the recycling of plastics.

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