Multi-metal heterostructure electrocatalyst, preparation method and application of multi-metal heterostructure electrocatalyst in plastic recovery

Abstract

The invention discloses a multi-metal heterostructure electrocatalyst, a preparation method and application of the multi-metal heterostructure electrocatalyst in plastic recovery, and belongs to the field of electrochemical catalyst.The catalyst comprises hydroxide and a metal heterostructure which grow on a foam metal matrix, and according to the method, soluble metal salt is used as a raw material; the multi-metal heterostructure electrocatalyst is prepared by adopting a two-step electrodeposition method. The catalyst can be applied to the process of recycling PET-derived EG in an alkaline solution through electro-catalysis upgrading, has extremely low overpotential and relatively high Faraday efficiency when being used for electro-oxidation of PET hydrolysate, and has very good catalytic stability. The multi-metal heterostructure electrocatalyst prepared by the method can also be applied to upgrading and recycling of other plastic derivatives, and has a good application prospect in the field of upgrading and recycling of the plastic derivatives.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical catalysis and relates to a multi-metal heterostructure electrocatalyst, a preparation method and application thereof in plastic recycling. Background Art

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

[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. The process revolves around the catalytic hydrolysis of PET, considering EG as 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, formate, and produces green hydrogen. Due to its unique chemical properties, glycolic acid shows great potential in different 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 has the advantages of high efficiency and good selectivity. The success of this electrochemical strategy is crucial to achieve high efficiency and selectivity of electrocatalysts. Precious metal catalysts such as palladium show excellent catalytic activity in ethylene glycol oxidation reaction (EGOR) and have been shown to be favorable for the generation of C2 product glycolic acid. In addition, the construction of heterojunction interface structures composed of precious metals (Pd, Au, etc.) and non-precious metals can reduce the use of precious metals, reduce costs and improve catalyst performance. Summary of the invention

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

[0005] The purpose of the present invention is achieved through the following technical solutions:

[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: placing the cleaned nickel foam in a first electrolyte and depositing it using a constant potential deposition method;

[0009] Step 3: preparing a mixed solution of sodium chloride and chloropalladic 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 in the second electrolyte of step 3 and perform electrodeposition using a constant potential transition method to obtain a multi-metal heterostructure electrocatalyst.

[0011] Preferably, in step 1, the concentration of the nickel nitrate solution is 0.1 mol / L.

[0012] Preferably, in step 2, the potential of the constant potential deposition is -1.0 V vs. SCE, and the deposition time is 5 min.

[0013] Preferably, in step 4, the electrodeposition is performed by a constant potential transition method, and the potential and time are -0.6 V vs. SCE for 10 s, and -0.2 V vs. SCE for 10 s, which are 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] In a third aspect, the present invention provides an application of a multi-metal heterostructure electrocatalyst prepared by the method described in the first aspect in recycling plastics.

[0016] Compared with the prior art, the present invention prepares a multi-metal heterostructure electrocatalyst by a two-step electrodeposition method, which greatly improves its catalytic activity and stability in alkaline solution, and jointly promotes the electro-oxidation of ethylene glycol to glycolic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the SEM picture of Pd / Ni(OH)2 / NF(a) prepared in Example 2 of the present invention and Ni(OH)2 / NF(b) prepared in Example 1.

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

[0019] Figure 3It is the XRD diagram of Pd / Ni(OH)2 / NF(a) prepared in Example 2 of the present invention and Ni(OH)2 / NF(b) prepared in Example 1.

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

[0021] Figure 5 It is a comparative LSV polarization curve diagram of Pd / Ni(OH)2 / NF prepared in Example 2 of the present invention, Ni(OH)2 / NF prepared in Example 1 and Pd / NF prepared in Example 3 with commercial Pd / C in KOH solution containing EG.

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

[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 a KOH solution containing EG. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0025] The remarkable performance of the catalyst prepared in the present invention in the oxidation of PET hydrolysate can be attributed to its unique structural advantages, especially the interfacial heterogeneous structure integrated in the Pd particles and the strong interfacial electronic interaction between Pd and Ni(OH)2. The catalyst exhibits extremely low overpotential and high Faradaic efficiency at 10 mA / cm 2 and 100mA / cm 2 At a current density of 1.5 V and 0.79 V, ethylene glycol oxidation only requires 0.53 V and 0.79 V. It achieves a Faradaic efficiency of up to 94.2% at 1.2 V versus RHE. It is worth noting that the metal heterostructure 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 into 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a uniform aqueous solution.

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

[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 h; the obtained product was Ni(OH)2 / NF.

[0030] Figure 1 The SEM test confirmed the loading mode of Ni(OH)2. Figure 2 TEM test and Figure 3 The XRD test confirmed the successful loading of Ni(OH)2. Figure 4 XPS test determined the chemical state of Ni element 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 into 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a uniform aqueous solution.

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

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

[0035] (4) Using the NF obtained in step (2) as the working electrode, a constant potential transition was performed in the solution prepared in step (3) at a potential and time of -0.6 V vs. SCE for 10 s and -0.2 V vs. SCE for 10 s, which was 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 h; the obtained product was Pd / Ni(OH)2 / NF.

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

[0038] Figure 5 The electrochemical measurement was carried out in a standard three-electrode electrolytic cell and 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 a Hg / HgO electrode was used as the reference electrode. The formula E RHE＝ E Hg / HgO +0.059pH+E0(0.098) to convert the potential to standard hydrogen electrode. The EG oxidation performance of the prepared Pd / Ni(OH)2 / NF was tested by linear sweep voltammetry. At the same time, commercial Pd / C was used as a comparative sample for testing. 2 and 100mA / cm 2 At a current density of , the voltage for ethylene glycol oxidation only requires 0.53 V and 0.79 vs. RHE. Figure 6 It tested the stability of the catalyst, which could maintain stable electrolysis for more than 20 hours. Figure 7 The Faradaic efficiency of EG catalyzed by Pd / Ni(OH)2 / NF was determined, and it achieved a Faradaic efficiency as high as 94.2% at 1.2 V. It exhibits 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 into 50 mL of deionized water. Stir magnetically at 300 r / min for 20 min to obtain a uniform aqueous solution.

[0041] (2) Using nickel foam cut into 1×2 cm pieces as the working electrode, a constant potential transition was performed in the solution prepared in step (1) at a potential and time of -0.6 V vs. SCE for 10 s and -0.2 V vs. SCE for 10 s, which was 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 h; the obtained product was Pd / NF. Figure 5 The LSV test determined the electrochemical performance of Pd / NF.

[0043] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A method for preparing a multi-metal heterostructure electrocatalyst, characterized in that: The following steps are included; Step 1: preparing a nickel nitrate solution with a concentration of 0.01-0.2 mol / L as the first electrolyte; Step 2: placing the cleaned nickel foam in a first electrolyte and depositing it using a constant potential deposition method; Step 3: preparing a mixed solution of sodium chloride and chloropalladic 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 in the second electrolyte of step 3 and perform electrodeposition using a constant potential transition method to obtain a multi-metal heterostructure electrocatalyst.

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

3. The method according to claim 1, characterized in that In step 2, the potential of constant potential deposition was −1.0 V vs. SCE, and the deposition time was 5 min.

4. The method according to claim 1, characterized in that In step 4, the electrodeposition was carried out by constant potential jump method, and the potential and time were −0.6 V vs. SCE for 10 s and −0.2 V vs. SCE for 10 s, which were repeated three times.

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

6. Use of a multi-metal heterostructure electrocatalyst prepared by the method according to any one of claims 1 to 4 in recycling plastics.

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