Preparation method of amorphous-nanocrystalline biphase PdCuFe material and application of amorphous-nanocrystalline biphase PdCuFe material in ethylene glycol electrooxidation
Amorphous-nanocrystalline PdCuFe catalysts were prepared by pulse electrodeposition, which solved the problems of narrow potential adaptability and insufficient stability of Pd-based catalysts in the ethylene glycol oxidation reaction. This enabled highly selective glycolic acid conversion within a wide potential window, promoting the industrialization of PET resource utilization.
Patent Information
- Application Number
- CN202511252083.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-03
- Publication Date
- 2025-12-05
AI Technical Summary
Existing Pd-based catalysts exhibit narrow potential adaptation windows, poor selectivity, and insufficient stability in ethylene glycol oxidation reactions, and are prone to inducing byproduct formation, making it difficult to achieve efficient and stable glycolic acid conversion.
Amorphous-nanocrystalline biphase PdCuFe electrocatalysts were prepared by pulse electrodeposition. By controlling the crystal phase structure, a PdCuFe alloy catalyst in which amorphous and nanocrystalline phases coexist was formed, which is suitable for the electro-oxidation reaction of ethylene glycol.
It maintains high selectivity and stability over a wide potential window, achieving efficient conversion of glycolic acid, making it suitable for large-scale applications, and solving the problems of narrow potential range and insufficient stability of traditional Pd-based catalysts.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of electrocatalytic materials, and in particular to a preparation method of amorphous-nanocrystalline dual-phase PdCuFe catalyst and application thereof in glycol electro-oxidation reaction for preparing glycolic acid. TECHNICAL BACKGROUND
[0002] Plastic pollution is becoming increasingly serious. As of now, more than 63 billion tons of plastic waste has been generated globally, and it is estimated that the number will exceed 120 billion tons by 2050. Among the numerous plastics, polyethylene terephthalate (PET) is widely used in packaging and textile fields due to its excellent mechanical properties and transparency, with an annual production of more than 700 million tons. Traditional PET recycling methods, such as mechanical recycling and pyrolysis, generally have low recycling efficiency, material performance degradation, high energy consumption, and large greenhouse gas emissions, making it difficult to meet the requirements of green and sustainable development. In recent years, electrocatalytic upgrading recycling, as a new green transformation path, has attracted widespread attention. This technology uses renewable electric energy to achieve selective electrocatalytic conversion of plastic hydrolysis products under mild conditions, combining controllable reaction and environmental friendliness. Ethylene glycol is one of the main products of PET hydrolysis, which can be converted into carbon dioxide, formic acid, glycolic acid, oxalic acid, and other oxidation products through ethylene glycol oxidation reaction. Among them, glycolic acid is the core monomer for synthesizing degradable polyglycolic acid, and has important applications in medical materials, fine chemicals, and personal care fields, with a growing market demand. Therefore, constructing an efficient electrocatalytic system to achieve high-selectivity conversion of ethylene glycol to glycolic acid is a key link to promote the high-value utilization of PET.
[0003] However, the reaction pathway of ethylene glycol oxidation is complex, the intermediates are diverse, and the reaction selectivity is highly sensitive to the potential, which puts high requirements on the composition, structure and performance of the electrocatalyst. Compared with other transition metal (such as Fe, Co, Ni, Cu) based materials, Pd based catalysts can effectively promote the three-step dehydrogenation process of ethylene glycol due to their rich electron surface and s-d orbital hybridization characteristics, and show high selectivity for ethylene glycol. However, Pd-based catalysts still face the following key problems in the oxidation of ethylene glycol: first, the potential adaptation window is narrow, and it is difficult to achieve stable high selectivity in a wide potential range (Adv. Mater. 2024, 36 (27): 2402767; Proc. Natl. Acad. Sci., 2024, 121 (17): e2318853121); second, C-C bond cleavage and over-oxidation are easily induced at high potential, leading to the generation of by-products (J. Mater. Chem. A, 2024, 12 (26): 15984-15995); third, the active sites are easily occupied by reaction intermediates or toxic species, causing rapid current decay (Chem. Sci., 2025, 16 (10): 4303-4310). Therefore, it is urgent to develop an electrocatalyst system with synergistic structure regulation capability, which can maintain high glycolic acid selectivity and Faraday efficiency in a wide potential window, to realize efficient and stable electrocatalytic conversion of ethylene glycol and promote the industrialization process of PET resource utilization. SUMMARY
[0004] The present application aims to solve the problems of poor selectivity, narrow potential adaptation range and insufficient stability of existing ethylene glycol electrocatalytic oxidation reaction, and proposes a PdCuFe electrocatalyst with amorphous-nanocrystalline dual-phase structure and a preparation method thereof. The method is simple, easy to control the crystal phase structure, and the raw materials are widely available, suitable for large-scale preparation and application. The catalyst of the present application can realize high selective conversion of ethylene glycol to glycolic acid in a wide potential window, providing a new technical approach for the high-value utilization of polyethylene terephthalate (PET) plastic depolymerization products.
[0005] The technical solutions adopted by the present application are as follows:
[0006] A preparation method of an amorphous-nanocrystalline dual-phase PdCuFe electrocatalyst, comprising the following steps: preparing a metal salt solution; mixing the metal salt solution with appropriate proportion and concentration and using it as an electrolyte, and performing pulse electrodeposition on a conductive substrate using a three-electrode system; washing and drying the catalyst to obtain a PdCuFe metal alloy catalyst with amorphous and nanocrystalline phases coexisting; and using the obtained catalyst for the electrocatalytic oxidation reaction of ethylene glycol to glycolic acid and other hydroxyl small molecules (such as glycerol, methanol, ethanol).
[0007] Further, the metal salt is one or more of palladium chloride, palladium nitrate, copper chloride, copper nitrate, copper sulfate, iron chloride, iron nitrate, iron sulfate, and complexes thereof, at a concentration of 5-20 mmol·L 1 .
[0008] Further, the molar ratio of Pd, Cu, and Fe metal salts in the composite electrolyte is Pd:Cu:Fe = 10-18:1-5:1-5.
[0009] Further, the electrodeposition method is pulse electrodeposition, with a deposition current density of 1-10 mA·cm -2 , an on-time (t on ) of 1-10 s, an off-time (t off ) of 5-20 s, a pulse cycle repetition of 50-300 times, and a deposition process at 15-35°C.
[0010] Further, the conductive substrate is selected from any one of nickel foam, copper foam, iron foam, carbon paper, carbon cloth, titanium mesh, carbon nanotube film, and conductive graphite sheet.
[0011] Further, the washing step uses deionized water or ethanol for repeated cleaning until the electrolyte is completely removed.
[0012] Further, the drying step is performed in an oven at 40-60°C until the sample reaches a constant weight.
[0013] Further, the PdCuFe material obtained by the above preparation method has a structure characterized by the coexistence of amorphous and nanocrystalline phases.
[0014] Further, the application of the amorphous-nanocrystalline dual-phase PdCuFe electrocatalyst in ethylene glycol oxidation reactions includes the following steps:
[0015] (1) Using a standard three-electrode system, the electrochemical workstation is used to test the catalyst performance at room temperature, with a platinum sheet as the working electrode, a Hg / HgO reference electrode, and the test conducted in a double-chamber battery separated by a pretreated Nafion 117 membrane;
[0016] (2) The ethylene glycol oxidation reaction test electrolyte contains 1M potassium hydroxide and 1M ethylene glycol, and the electrochemical reaction is carried out at room temperature;
[0017] (3) The product is quantitatively analyzed by high-performance liquid chromatography.
[0018] (4) After the reaction is completed, the catalyst is washed and dried for repeated use.
[0019] Further, the PdCuFe electrocatalyst with amorphous-nanocrystalline dual-phase structure is also suitable for electrochemical oxidation reactions of glycerol, methanol, ethanol and other small organic molecules containing hydroxyl groups.
[0020] Compared with the prior art, the advantages of the present application are as follows:
[0021] (1) Material preparation and structural innovation
[0022] The amorphous-nanocrystalline dual-phase PdCuFe alloy catalyst is prepared by pulse electrodeposition method, which is simple and easy to control the crystal phase ratio. The amorphous and nanocrystalline synergistic structure formed can provide stable sites with rich defects and ordered crystal faces, and can provide high activity and high selectivity for ethylene glycol oxidation reaction, and is suitable for large-scale preparation.
[0023] (2) Wide potential window and high selectivity
[0024] In view of the narrow potential adaptation range of the traditional Pd-based catalyst, the catalyst developed in the present application can maintain more than 90% of the glycolic acid Faraday efficiency in a wide potential range (0.5-1.6V vs. RHE), and can achieve a high yield of 8.736mmol·h-1·cm-2 at 1.6V vs. RHE, which shows stable and high conversion performance. 1 ·cm -2
[0025] (3) Structural advantage promotes synergistic catalysis
[0026] The catalyst in the present application can efficiently adsorb reactants and promote the dehydrogenation of hydroxyl groups at low potential, and can moderately stabilize the intermediates at high potential, thereby realizing stable and efficient catalytic performance.
[0027] (4) Sustainable plastic upgrading route
[0028] The present application provides a new way of using electrocatalytic technology to efficiently convert PET plastic hydrolysis product ethylene glycol into high-value-added chemicals (glycolic acid), which has environmental friendliness and economic benefit, and provides an innovative solution for the resource utilization of plastic waste. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 X-ray diffraction patterns of PdCuFe / NF and nickel foam (NF) in Example 1;
[0030] Figure 2 Transmission electron microscopy image of PdCuFe / NF in Example 1;
[0031] Figure 3 Linear sweep voltammetry curve of PdCuFe / NF for electrocatalytic oxidation of ethylene glycol in Application Example 1;
[0032] Figure 4 Linear sweep voltammetry curves for electrocatalytic glycerol oxidation of PdCuFe / NF in Example 3. DETAILED DESCRIPTION
[0033] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below in combination with specific examples and application examples.
[0034] Example 1: Preparation of PdCuFe catalyst (PdCuFe / NF) with nickel foam as conductive substrate
[0035] Firstly, a nickel foam (NF) substrate with a size of about 1 cm x 2 cm was placed in acetone for ultrasonic treatment for 10 min and washed clean with deionized water; then, the nickel foam was immersed in a 3M hydrochloric acid solution for ultrasonic treatment for 10 min, and then washed thoroughly with deionized water and dried for use.
[0036] A 14 mL solution of chloroplatinic acid (H2PdCl4) with a concentration of 10 mM, 3 mL of a solution of iron chloride hexahydrate (FeCl3·6H2O) with a concentration of 10 mM, and 3 mL of a solution of cuprous chloride dihydrate (CuCl2·2H2O) with a concentration of 10 mM were mixed to prepare a composite electrolyte with a total volume of 20 mL.
[0037] In a single-tank three-electrode electrochemical system, the pretreated nickel foam was used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl electrode as the reference electrode, and pulse electrodeposition was carried out at a current density of 3 mA·cm -2 ; the pulse parameters were set as 5 s for the on-time (t on ), 10 s for the off-time (t off ), and the cycle was repeated 120 times, and the PdCuFe / NF catalyst was obtained after deposition.
[0038] X-ray diffraction (XRD) analysis showed that the characteristic diffraction peak of Pd in the PdCuFe / NF sample exhibited obvious broadening and peak weakening characteristics, indicating that the crystallinity of the obtained material was significantly reduced, accompanied by a decrease in grain size. This result shows that the preparation strategy of pulse electrodeposition combined with multi-metallic synergistic doping can effectively regulate the crystallization behavior of Pd, and construct a PdCuFe / NF catalyst with refined grain size and more disordered structure. Figure 1
[0039] Transmission electron microscopy (TEM) analysis showed that the PdCuFe / NF was formed by agglomeration of nanoparticles Figure 2 a) High-resolution transmission electron microscopy (HRTEM) images show that there are large areas of disordered regions on the surface of the material, coexisting with nanocrystalline regions, confirming that it is an amorphous-nanocrystalline composite structure Figure 2 b、2c) Selected area electron diffraction (SAED) patterns further verify the coexistence of amorphous and nanocrystalline phases Figure 2 d) Element distribution map (TEM-EDS) results show that Pd, Cu and Fe are uniformly distributed in the material Figure 3 e).
[0040] Example 2: Preparation of PdCuFe / NF catalysts with different metal salts
[0041] A 14 mL solution of chloroplatinic acid (H2PdCl4) with a concentration of 10 mM, 3 mL of a solution of iron nitrate nonahydrate (Fe(NO3)3·9H2O) with a concentration of 10 mM, and 3 mL of a solution of copper nitrate trihydrate (Cu(NO3)2·3H2O) with a concentration of 10 mM were mixed to prepare a composite electrolyte with a total volume of 20 mL.
[0042] Deposition was carried out under the same pulse electrodeposition conditions as in Example 1 (current density 3 mA·cm -2 , power-on time 5 s, power-off time 10 s, cycle 120 times) to obtain a PdCuFe / NF catalyst. Characterization showed that the material still maintained an amorphous-nanocrystalline composite structure, and the Pd, Cu and Fe elements were uniformly distributed.
[0043] Example 3: Preparation of PdCuFe / NF catalysts with high CuFe content
[0044] A 10 mL solution of chloroplatinic acid (H2PdCl4) with a concentration of 10 mM, 5 mL of a solution of iron chloride hexahydrate (FeCl3·6H2O) with a concentration of 10 mM, and 5 mL of a solution of cuprous chloride dihydrate (CuCl2·2H2O) with a concentration of 10 mM were mixed to prepare a composite electrolyte with a total volume of 20 mL.
[0045] Deposition was carried out under the same pulse electrodeposition conditions as in Example 1 (current density 3 mA·cm -2 , power-on time 5 s, power-off time 10 s, cycle 120 times) to obtain a PdCuFe / NF catalyst with high CuFe content. Characterization showed that the material still maintained an amorphous-nanocrystalline composite structure, and the Pd, Cu and Fe elements were uniformly distributed.
[0046] Example 4: Preparation of PdCuFe / NF catalysts by high current density pulse deposition
[0047] Take 14 mL of 10 mM chloroplatinic acid (H2PdCl4) solution, 3 mL of 10 mM ferric chloride hexahydrate (FeCl3·6H2O) solution, and 3 mL of 10 mM cuprous chloride dihydrate (CuCl2·2H2O) solution, and mix them to prepare 20 mL of composite electrolyte.
[0048] Using a current density of 5 mA·cm 2 Pulse electrodeposition, energizing time (t) on 5s, power outage time (t) off After 10s and 120 cycles, a PdCuFe / NF catalyst prepared under high current density conditions was obtained. Characterization showed that the material still maintains an amorphous-nanocrystalline composite structure, and the Pd, Cu, and Fe elements are evenly distributed.
[0049] Example 5: Preparation of PdCuFe catalyst (PdCuFe / CP) using carbon paper as a conductive substrate
[0050] Mix 14 mL of 10 mM chloroplatinic acid (H2PdCl4) solution, 3 mL of 10 mM ferric chloride hexahydrate (FeCl3·6H2O) solution, and 3 mL of 10 mM cuprous chloride dihydrate (CuCl2·2H2O) solution to prepare a composite electrolyte with a total volume of 20 mL.
[0051] Using carbon paper (CP) as the conductive substrate, the same pulse electrodeposition conditions as in Example 1 were employed (current density 3 mA·cm⁻¹). -2 PdCuFe / CP catalyst was obtained by deposition (power-on time 5s, power-off time 10s, 120 cycles). Characterization showed that the material still maintains an amorphous-nanocrystalline composite structure and the Pd, Cu and Fe elements are evenly distributed.
[0052] Application Example 1: Electrocatalytic application of PdCuFe / NF catalyst in the electrooxidation of ethylene glycol
[0053] The PdCuFe / NF composite material prepared in Example 1 was used as the working electrode to assemble a standard three-electrode system. Electrocatalytic performance was evaluated in 1.0 M KOH solution with and without 1.0 M ethylene glycol (EG). Platinum foil was used as the counter electrode, and Hg / HgO was used as the reference electrode. All potentials were converted to reversible hydrogen electrode (RHE) potentials. Results obtained by linear sweep voltammetry (LSV) showed... Reaction potential (V vs. RHE)), after the addition of ethylene glycol, the overpotential of the reaction is significantly reduced, and the current density is rapidly increased, indicating that PdCuFe / NF has excellent activity in the electro-oxidation of ethylene glycol. Chronoamperometric (CA) tests combined with high-performance liquid chromatography (HPLC) analysis show (Table 1) that glycolic acid is the main oxidation product, and the yield increases with increasing potential. The Faraday efficiency remains above 90% in a wide potential range of 0.5-1.6 V vs. RHE, and the maximum FE can reach 97%, showing that the catalyst has high selectivity at a wide potential.
[0054] Table 1. Performance list.
[0055] Faradaic efficiency (%) GA yield (mmol h-1 1 ·cm -2 )]]> Figure 4 0.5 0.173 96.7 0.6 0.514 97.0 0.7 1.032 95.3 0.8 1.637 93.8 0.9 2.256 93.6 1.0 2.976 93.1 1.1 3.773 94.1 1.2 4.901 93.8 1.3 5.976 93.3 1.4 6.970 92.7 1.5 7.632 91.0 1.6 8.736 90.2 1.7 8.938 82.6
[0056] Application Example 2: Performance of PdCuFe / NF catalyst at different ethylene glycol concentrations
[0057] In 1.0 M KOH electrolyte, 0.5 M, 1.0 M and 2.0 M ethylene glycol were added respectively, and the catalytic performance of PdCuFe / NF was tested by using a standard three-electrode system. CA tests were performed, and the products were analyzed by HPLC. The results show (Table 2) that as the concentration of ethylene glycol increases, the current density increases significantly, and the yield of glycolic acid increases with increasing concentration, and the Faraday efficiency remains at a high level, indicating that PdCuFe / NF still has good catalytic activity and selectivity at different substrate concentrations.
[0058] Table 2. Performance list (test potential is 0.8 V vs. RHE).
[0059]
[0060] Application Example 3: Electro-catalytic application of PdCuFe / NF catalyst in glycerol electro-oxidation reaction
[0061] In 1.0 M KOH solution containing 1.0 M glycerol (GLY), LSV tests were performed with PdCuFe / NF as the working electrode. The results show (Table 3) ), the overpotential of the reaction is significantly reduced after the addition of glycerol, and the current density is rapidly increased, indicating that PdCuFe / NF exhibits excellent electro-catalytic activity in the electro-oxidation of glycerol.
[0062] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing an amorphous-nanocrystalline biphase PdCuFe electrocatalyst and its application in the electro-oxidation reaction of ethylene glycol, characterized in that: A Pd, Cu, Fe metal salt solution is mixed in a set ratio to obtain a composite electrolyte; the composite electrolyte is used in a three-electrode system to uniformly deposit metal ions on the surface of a substrate by pulse electrodeposition; the obtained deposit is washed and dried to form a PdCuFe metal alloy catalyst with coexisting amorphous phase and nanocrystalline phase; and the electrocatalyst is used as a working electrode for electrocatalytic oxidation of ethylene glycol and other small hydroxyl molecules.
2. The method of claim 1, wherein: The metal salt is one or more of palladium chloride, palladium nitrate, copper chloride, copper nitrate, copper sulfate, iron chloride, iron nitrate, iron sulfate, and complexes thereof, and the solution concentration is 5-20 mmol·L- 1 .
3. The method of claim 1, wherein: The molar ratio of Pd, Cu, Fe metal salts in the composite electrolyte is Pd:Cu:Fe = 10-18:1-5:1-5.
4. The method of claim 1, wherein: The deposition method is pulse electrodeposition, the deposition current density is 1-10 mA·cm -2 , the power-on time (t on ) is 1-10 s, the intermittent time (t off ) is 5-20 s, the pulse cycle repeats 50-300 times, and the temperature is 15-35℃.
5. The method of claim 1, wherein: The conductive substrate is any one of nickel foam, copper foam, iron foam, carbon paper, carbon cloth, titanium mesh, carbon nanotube film, and conductive graphite sheet.
6. The method of claim 1, wherein: The washing step uses deionized water or ethanol for repeated cleaning until the electrolyte is completely removed.
7. The method of claim 1, wherein: The drying step is performed in an oven at 40-60°C until the sample reaches a constant weight.
8. The method of claim 1, wherein: The catalyst has a dual-phase structure of disordered amorphous phase and ordered nanocrystalline phase.
9. The method of claim 1, wherein: The catalyst is used for electrocatalytic oxidation of ethylene glycol and other small hydroxyl molecules (such as glycerol, methanol, ethanol) to generate glycolic acid and corresponding oxidation products.