PdCuCo trimetal alkene material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemistry, and particularly discloses a novel PdCuCo trimetal alkene material as well as a preparation method and application thereof. The novel PdCuCo trimetal alkene material is a PdCuCo trimetal alloy nanosheet, has ultra-thin (1nm) thickness and rich lattice defects, and is prepared by the following steps: adding polyvinylpyrrolidone, bis (acetylacetone) palladium, copper acetylacetonate and cobalt acetylacetonate into a mixed solution of ethylenediamine and N, N-dimethylformamide, carrying out solvothermal reaction and freeze drying treatment, and preparing the novel PdCuCo trimetal alkene material. And the PdCuCo trimetal alkene is obtained. The preparation method disclosed by the invention is a simple one-pot solvothermal method, high-temperature reaction is not involved, the obtained product has ultra-thin thickness, the utilization rate of Pd is effectively improved, the catalytic activity is obviously improved and the high selectivity of a glycollic acid product is high in the process of electrically reforming the PET plastic, and a solution can be provided for value-added utilization of the PET plastic.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry technology, and particularly to a novel PdCuCo trimetallicene material, a preparation method thereof and an application thereof. Background Art

[0002] The significant increase in plastic consumption has gradually highlighted the problem of waste disposal, becoming one of the major environmental challenges faced globally. In recent years, due to the release of a large amount of carbon dioxide, toxic additives and microplastics (including nanoplastics) during the degradation process of waste plastics in the natural environment, public concerns have been exacerbated. Polyethylene terephthalate (PET) plastic is the main source of the annual polyester production, with a production volume of approximately 70 million tons, and it is the most common waste plastic in daily packaging and textile applications. Therefore, a large amount of research work has been directed towards recycling PET plastic waste into valuable chemicals. Under alkaline conditions, PET can depolymerize into terephthalic acid (TPA) and ethylene glycol (EG). However, considering the high boiling point (197.6 °C) and high water solubility of ethylene glycol, electro-oxidizing ethylene glycol into value-added chemicals is considered a more economically feasible and effective method compared to direct ethylene glycol separation.

[0003] The electro-reforming PET recycling technology has opened up a promising approach for the production of valuable chemicals from PET waste plastics under mild conditions, meeting the goals of sustainable development. Through this technology, the EG molecules in the PET hydrolysis products can be partially electrocatalytically oxidized to produce formic acid (FA) and glycolic acid (GA). Compared with EG ($1400 per ton) and FA ($400 per ton), the high price of GA ($3000 per ton) and its key role in the production of various chemicals and degradable polymers make the synthesis of GA from PET waste plastics (EG molecules in PET hydrolysis products) have considerable prospects. This method not only provides a sustainable solution for waste PET plastic management but also offers significant economic benefits. In addition, under mild conditions, electro-reforming PET to GA has high Faradaic efficiency and fast reaction kinetics, thus providing a competitive candidate technology to avoid the existing GA synthesis methods involving high energy consumption and toxic chemicals.

[0004] In recent years, although noble metal (Pt, Pd, Au)-based materials have become effective catalysts for electrocatalytic EG conversion, their large-scale commercialization still faces many challenges: First, although the alloying method can reduce the noble metal content and lower the cost, the existing alloy preparation process involves complex programmed temperature rising steps and requires high-temperature reactions above 200 °C, which increases energy consumption and severely restricts low-cost industrial production; Second, the noble metal alloys obtained by the existing processes are usually zero-dimensional alloy particles with large sizes, poor dispersibility, and easy agglomeration, resulting in a reduced specific surface area of the catalyst and insufficient exposure of active sites, ultimately leading to low utilization rate of noble metal atoms and poor catalytic activity; Third, even if some researchers synthesize two-dimensional noble metal alloy nanosheets by relying on complex preparation processes, the thickness is large or uneven, resulting in a still small specific surface area. Fourth, it is difficult to precisely control the Pd content or atomic ratio in the preparation process of existing noble metals, especially Pd alloys. For example, when the Pd and Cu feeding ratio is 5:1, the Pd and Cu in the obtained product are 1:1, resulting in low Pd utilization rate. Therefore, there is an urgent need to develop a two-dimensional ultrathin Pd-based nanosheet catalyst with low cost and high activity to achieve the goal of efficiently and stably electro-reforming PET plastics into high-value chemicals. Summary of the Invention

[0005] In order to overcome the problems of large particle size, small specific surface area, and poor catalytic reaction effect of existing alloy catalysts. The purpose of the present invention is to propose a novel PdCuCo three-metalene material, its preparation method and application. The novel PdCuCo three-metalene material is a PdCuCo three-metal alloy nanosheet with an ultrathin atomic layer (1 nm) thickness and abundant lattice defects. The lattice defects include five types: lattice distortion, grain boundary, stacking fault, point defect, and low-coordination atom step. The preparation steps are as follows:

[0006] (1) Mix polyvinylpyrrolidone with palladium bis(acetylacetonate), copper acetylacetonate, and cobalt acetylacetonate, add them to a mixed solution of ethylenediamine and N,N-dimethylformamide (DMF), stir for 15 minutes to form a homogeneous solution, and transfer the mixture to a 100 mL high-pressure-resistant polytetrafluoroethylene reaction kettle for reaction;

[0007] (2) Centrifuge the obtained product, wash it 6 times with acetone / water, and put it into a freeze dryer for freeze drying for 24 hours to collect the powdery product, namely PdCuCo three-metalene (metalene refers to an ultrathin nanosheet with an atomic layer thickness);

[0008] It should be noted that: as used hereinafter, the term "palladium bis(acetylacetonate)" has the molecular formula Pd(acac)2, the term "copper acetylacetonate" has the molecular formula Cu(acac)2, and the term "cobalt acetylacetonate" has the molecular formula Co(acac)2.

[0009] In the most preferred embodiment of the present invention, the feed atomic ratio of palladium bis(acetylacetonate), copper acetylacetonate and cobalt acetylacetonate is Pd:Cu:Co = 52.8:41.0:6.2.

[0010] In the most preferred embodiment of the present invention, the concentration of ethylenediamine is 98% and the dosage is 0.5 mL; the concentration of N,N-dimethylformamide is 99.5% and the dosage is 10 mL 。

[0011] In the most preferred embodiment of the present invention, the reaction temperature is 145 °C.

[0012] In the most preferred embodiment of the present invention, the reaction time is 24 hours.

[0013] In the most preferred embodiment of the present invention, the number of centrifugation times is 6 times and the centrifugation speed is 8000 r / min.

[0014] In the most preferred embodiment of the present invention, the thickness of the synthesized PdCuCo trimetallicene is about 1 nm.

[0015] In the most preferred embodiment of the present invention, the atomic ratio of Pd, Cu and Co in the synthesized PdCuCo trimetallicene (PdCuCo-0.9) is 55.0:44.1:0.9.

[0016] The PdCuCo trimetallicene obtained by the preparation method of the present invention is used as an electrocatalyst for electro-reforming PET.

[0017] The product of electro-reforming PET with the PdCuCo trimetallicene obtained by the preparation method of the present invention is a high-value C2 product (glycolic acid).

[0018] Advantages of the present invention: (1) The PdCuCo trimetallicene obtained by the preparation method provided by the present invention is a two-dimensional ultrathin nanosheet with an atomic layer thickness (about 1 nm), which has abundant lattice defects and fully exposed metal active sites; (2) The preparation method of PdCuCo trimetallicene is a one-pot solvothermal method, the synthesis process is simple, and the precise control of the content of precious metal Pd can be achieved without high-temperature reaction, and the Pd utilization rate is high; (3) The activity of electro-reforming PET with the PdCuCo trimetallicene provided by the present invention is significantly improved; (4) The product of electro-reforming PET with the PdCuCo trimetallicene provided by the present invention is a high-value C2 product (glycolic acid), rather than low-value C1 products such as formic acid, and the Faraday efficiency of GA synthesis is as high as 94.8%, and the return on investment of electro-reforming PET is significantly improved. Description of the Drawings

[0019] Figure 1 It is a transmission electron microscope (TEM) image of the material obtained in Example 1;

[0020] Figure 2 TEM image of the material obtained in Example 2;

[0021] Figure 3 Atomic force microscope (AFM) image and thickness measurement results of the material obtained in Example 2;

[0022] Figure 4 TEM image of the material obtained in Example 3;

[0023] Figure 5 TEM image of the material obtained in Comparative Example 1;

[0024] Figure 6 TEM image of the material obtained in Comparative Example 2;

[0025] Figure 7 X-ray powder diffraction (XRD) pattern of the material obtained in Example 2

[0026] Figure 8 X-ray photoelectron spectroscopy (XPS) patterns of the materials obtained in Example 2, Comparative Example 1, and Comparative Example 2;

[0027] Figure 9 Electrochemically active surface area diagrams of the materials obtained in Example 2, Comparative Example 1, Comparative Example 2, and commercial palladium black for electro-reforming PET;

[0028] Figure 10 Specific surface area activity diagrams of the materials obtained in Example 2, Comparative Example 1, Comparative Example 2, and commercial palladium black for electro-reforming PET;

[0029] Figure 11 Mass activity diagrams of the materials obtained in Examples 1-4, Comparative Example 1, Comparative Example 2, and commercial palladium black for electro-reforming PET;

[0030] Figure 12 Product analysis of the material obtained in Example 2 for electro-reforming PET. Detailed implementation mode

[0031] The present invention will be further described below in conjunction with the accompanying drawings and examples.

[0032] Example 1

[0033] A PdCuCo trimetallicene material, and its preparation method includes the following steps:

[0034] (1) Preparation of precursor solution: Polyvinylpyrrolidone, 30 mg of palladium bis(acetylacetonate), 20 mg of copper acetylacetonate, and 1 mg of cobalt acetylacetonate (i.e., the feeding atomic ratio Pd:Cu:Co = 55.1:42.7:2.2) were dissolved in a mixed solvent of 0.5 mL of ethylenediamine (98%) and 10 mL of N,N-dimethylformamide (DMF, 99.5%). After stirring for 15 min, a uniform precursor solution was formed;

[0035] (2) Solvothermal synthesis of PdCuCo: The precursor solution obtained in step (1) was transferred to a 100 mL high-pressure-resistant polytetrafluoroethylene reaction kettle and reacted in an oven at 145 °C for 24 h. After the reaction was completed, the black product was centrifuged and washed, and finally a PdCuCo trimetallicene material (PdCuCo-0.3) was obtained after freeze-drying.

[0036] The test results of inductively coupled plasma mass spectrometry showed that the atomic ratio of Pd, Cu, and Co in the obtained PdCuCo-0.3 was 54.5:45.2:0.3, which was basically consistent with the actual feeding ratio. From the TEM image ( Figure 1 ), it can be seen that the obtained PdCuCo-0.3 was a two-dimensional nanosheet structure, and its surface had three types of lattice defects: lattice distortion, grain boundary, and stacking fault.

[0037] Example 2

[0038] A PdCuCo trimetallicene material, and its preparation method includes the following steps:

[0039] (1) Preparation of precursor solution: Polyvinylpyrrolidone, 30 mg of palladium bis(acetylacetonate), 20 mg of copper acetylacetonate, and 3 mg of cobalt acetylacetonate (i.e., the feeding atomic ratio Pd:Cu:Co = 52.8:41.0:6.2) were dissolved in 0.5 mL of ethylenediamine (98%) and 10 mL of N,N-dimethylformamide (DMF, 99.5%). After stirring for 15 min, a uniform precursor solution was formed;

[0040] (2) Solvothermal synthesis of PdCuCo: The precursor solution obtained in step (1) was transferred to a 100 mL high-pressure-resistant polytetrafluoroethylene reaction kettle and reacted in an oven at 145 °C for 24 h. After the reaction was completed, the black product was centrifuged and washed, and finally a PdCuCo trimetallicene material (PdCuCo-0.9) was obtained after freeze-drying.

[0041] Inductively coupled plasma mass spectrometry (ICP-MS) test results show that the atomic ratio of Pd, Cu, and Co in the obtained PdCuCo-0.9 is 54.5:45.2:0.9, indicating that it is basically consistent with the actual feeding ratio. PdCuCo-0.9 has a two-dimensional nanosheet structure with a lateral size of ~13 nm and a large number of lattice defects on its surface, including five types: lattice distortion, grain boundary, stacking fault, point defect, and low-coordination atom step ( Figure 2 ). In addition, atomic force microscopy (AFM) analysis results show that the thickness of the PdCuCo-0.9 nanosheet is only 1 nm, confirming that the PdCuCo-0.9 sample has a metalene structure with atomic layer thickness ( Figure 3 ).

[0042] Example 3

[0043] A PdCuCo trimetallicene material, and its preparation method includes the following steps:

[0044] (1) Preparation of the precursor solution: Dissolve polyvinylpyrrolidone, 30 mg of palladium bis(acetylacetonate), 20 mg of copper acetylacetonate, and 5 mg of cobalt acetylacetonate (i.e., the feeding atomic ratio Pd:Cu:Co = 50.7:39.3:10.0) into 0.5 mL of ethylenediamine (98%) and 10 mL of N,N-dimethylformamide (DMF, 99.5%), and stir for 15 min to form a uniform precursor solution;

[0045] (2) Solvothermal synthesis of PdCuCo: Transfer the precursor solution obtained in step (1) to a 100 mL high-pressure-resistant polytetrafluoroethylene reaction kettle, react in an oven at 145 °C for 24 h, after the reaction is completed, centrifuge and wash the black product, and finally obtain a PdCuCo trimetallicene material (PdCuCo-1.7) after freeze-drying.

[0046] Inductively coupled plasma mass spectrometry (ICP-MS) test results show that the atomic ratio of Pd, Cu, and Co in the obtained PdCuCo-1.7 is 55.2:43.1:1.7, indicating that it is basically consistent with the actual feeding ratio. Transmission electron microscopy (TEM) test results show ( Figure 4 ) that the lateral size of the PdCuCo-1.7 nanosheet is ~20 nm, and the nanosheet surface has four types of lattice defects: lattice distortion, grain boundary, stacking fault, and point defect.

[0047] Example 4

[0048] A PdCuCo trimetallicene material, and its preparation method includes the following steps:

[0049] (1) Preparation of precursor solution: Polyvinylpyrrolidone, 30 mg of palladium bis(acetylacetonate), 20 mg of copper acetylacetonate, and 10 mg of cobalt acetylacetonate (i.e., the feeding atomic ratio of Pd:Cu:Co = 46.1:35.7:18.2) were dissolved in 0.5 mL of ethylenediamine (98%) and 10 mL of N,N-dimethylformamide (DMF, 99.5%), and stirred for 15 min to form a uniform precursor solution;

[0050] (2) Solvothermal synthesis of PdCuCo: The precursor solution obtained in step (1) was transferred to a 100 mL high-pressure-resistant polytetrafluoroethylene reaction kettle, and reacted in an oven at 145 °C for 24 h. After the reaction was completed, the black product was centrifuged and washed, and finally a PdCuCo trimetallicene material (PdCuCo-4.9) was obtained after freeze-drying.

[0051] The test results of inductively coupled plasma mass spectrometry showed that the atomic ratio of Pd, Cu, and Co in the obtained PdCuCo-4.9 was 54.3:40.8:4.9. The content of Co decreased because Co was difficult to be reduced, but the content of Pd did not decrease.

[0052] Comparative Example 1

[0053] A palladium (Pd) metal nanosheet

[0054] A monometallic Pd metal catalyst was prepared by a method similar to that of Example 1, except that copper acetylacetonate and cobalt acetylacetonate were not added when preparing the precursor solution. The transmission electron microscopy test results showed that ( Figure 5 ), the lateral size of the obtained Pd nanosheets was ~37 nm, the surface of the nanosheets had a regular lattice arrangement, and only a small amount of lattice defects were observed. The test results of inductively coupled plasma mass spectrometry showed that the Pd atomic content in the obtained Pd sample was 99%. It can be seen that there was basically no loss compared with the feeding.

[0055] Comparative Example 2

[0056] A binary palladium-copper (PdCu) alloy nanosheet

[0057] A binary palladium-copper (PdCu) alloy nanosheet was prepared by a method similar to that of Example 1, except that cobalt(II) acetylacetonate was not added when preparing the precursor solution, and the Pd:Cu feeding ratio was 56.3:43.7. The transmission electron microscopy test results showed that ( Figure 6 ), the lateral size of the obtained PdCu alloy nanosheets was ~20 nm, and the surface of the nanosheets had two types of lattice defects: lattice distortion and grain boundaries. The test results of inductively coupled plasma mass spectrometry showed that the atomic ratio of Pd and Cu in the obtained PdCu alloy nanosheets was 57.4:42.6, and it can be seen that it was basically consistent with the actual feeding ratio.

[0058] The morphologies of the materials obtained in Examples 1-3 and Comparative Examples 1-2 were observed by transmission electron microscopy. Through comparison, it was found that among all the tested samples, PdCuCo-0.9 obtained in Example 2 had the smallest lateral size (∼13 nm), the most types and the highest density of lattice defects, and the thickness of the nanosheets was ∼1 nm, indicating the largest specific surface area; the XRD pattern of the PdCuCo-0.9 sample obtained in Example 2 confirmed that it was a face-centered cubic ternary alloy structure ( Figure 7 ); the XPS spectrum of the PdCuCo-0.9 sample obtained in Example 2 confirmed the coexistence of three elements, Pd, Cu, and Co, in the sample ( Figure 8 ). In addition, the inductively coupled plasma mass spectrometry test results of the materials obtained in Examples 1-4 and Comparative Examples 1-2 confirmed that the metal atom ratios of the obtained samples were basically consistent with the feeding ratios, proving that the preparation method of the present invention can be precisely regulated by controlling the reactants and reaction conditions and changing the feeding ratio of metal salts, and has a high metal atom utilization rate.

[0059] Test Example

[0060] Electrochemical active area analysis: Under the condition of 1.0 M KOH + 1.0 M EG, cyclic voltammetry (CV) curves at different scanning rates were collected, and the double-layer capacitance (C dl ) values of the materials obtained in Example 2, Comparative Example 1, Comparative Example 2, and commercial palladium black catalyst were calculated, and then the electrochemical active area values of the samples were calculated. From Figure 9 the comparison data, it can be seen that the PdCuCo-0.9 trimetallicene obtained in Example 2 had the largest electrochemical active area, which was 2 times that of the Pd sample obtained in Comparative Example 1 and 1.5 times that of commercial palladium black, indicating that the PdCuCo-0.9 sample had good dispersion and many exposed active sites, which was helpful for enhancing catalysis.

[0061] Application Example

[0062] In a mixed solution of PET hydrolyzate and 4.0 M potassium hydroxide, the specific area activities of the materials obtained in Example 2, Comparative Example 1, Comparative Example 2, and commercial palladium black catalyst for electro-reforming PET were tested. The results showed that the PdCuCo-0.9 trimetallicene obtained in Example 2 had the highest specific area activity (9.7 mA cm -2 ), which was 1.8 times that of commercial palladium black ( Figure 10 ).

[0063] In addition, the mass activities of the materials obtained in Example 2, Comparative Example 1, Comparative Example 2, and commercial palladium black catalyst for electro-reforming PET were also tested. The results showed that the PdCuCo-0.9 trimetallicene obtained in Example 2 had the highest mass activity (16.6 A mg -1 Pd) It is 4.3 times that of commercial palladium black, indicating that the activity of the catalyst prepared by the preparation method provided by the present invention is significantly improved. Figure 11 )

[0064] The product of electro-reforming PET of PdCuCo-0.9 obtained in Example 2 was identified by nuclear magnetic resonance hydrogen spectrum. The results showed that the main product of this electro-reforming process was high-value glycolic acid. Further quantitative analysis showed that the yield of glycolic acid synthesized by electro-reforming PET of PdCuCo-0.9 obtained in Example 2 was 0.32 mmol h -1 cm -2 , and the Faraday efficiency was 94.8%. The high Faraday efficiency close to 100% indicates that PdCuCo-0.9 obtained in Example 2 has great application potential in the electro-synthesis of glycolic acid from electro-reforming PET plastic waste. Figure 12 )

[0065] The PdCuCo trimetallic ene catalyst obtained in the embodiment of the present invention is a two-dimensional ultrathin alloy nanosheet with a thickness of only 1 nm; the preparation method provided by the present invention has a simple process, does not require high-temperature reaction, has low energy consumption and strong safety; from the structures of transmission electron microscopy, XRD and XPS, it can be seen that the PdCuCo catalyst prepared by this method is a ternary alloy nanosheet with an extremely thin thickness and good dispersibility, and is not easy to agglomerate; from the results of inductively coupled plasma mass spectrometry, it can be known that the composition of the catalyst prepared by the present invention is basically consistent with the feeding ratio of each element, indicating that this method can achieve precise control of the catalyst ratio; from the performance of electro-reforming PET plastic, compared with commercial palladium black, the activity of the obtained PdCuCo trimetallic ene catalyst is significantly improved.

[0066] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge scope of those skilled in the art.

Claims

1. A novel PdCuCo tri - metalene material, characterized in that: The PdCuCo trimetalene has an ultrathin atomic layer thickness (1 nm) and abundant lattice defects.

2. The novel PdCuCo three-metalene material according to claim 1, characterized in that, The PdCuCo trimetalene is composed of an alloy of three elements, Pd, Cu, and Co.

3. A method for preparing the novel PdCuCo three-metalene material according to any one of claims 1-2, characterized in that, Specifically, it includes the following steps: Step (1): Mix polyvinylpyrrolidone with palladium salt, copper salt, and cobalt salt, add them to two organic solvents, form a homogeneous solution by stirring, and transfer the mixture to a high-pressure resistant reaction kettle for solvothermal reaction; Step (2): Centrifuge the reaction solution in Step (1), and obtain PdCuCo trimetalene after freeze-drying. The trimetalene is an ultrathin nanosheet with an atomic layer thickness.

4. The preparation method of the novel PdCuCo three-metalene material according to claim 3, wherein: The palladium salt is palladium bis(acetylacetonate), the copper salt is copper(II) acetylacetonate, the cobalt salt is cobalt(II) acetylacetonate, and the feeding atomic ratio is Pd:Cu:Co = 55.1:42.7:2.2 - 18.

2.

5. The preparation method of the novel PdCuCo three-metalene material according to claim 3, characterized in that: The two organic solvents are ethylenediamine and N,N-dimethylformamide.

6. The preparation method of the novel PdCuCo three-metalene material according to claim 3, wherein: The solvothermal reaction temperature is 100 - 180 °C.

7. The preparation method of the novel PdCuCo three-metalene material according to claim 3, wherein: The solvothermal reaction time is 3 - 48 hours.

8. The novel PdCuCo three-metalene material according to any one of claims 1-2, characterized in that, It is applied to the field of electro-reforming PET plastics or the field of electro-oxidizing ethylene glycol derived from PET plastics.

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