Pt-pb / nf bimetallic catalyst for electrocatalytic oxidation of ethylene glycol to glycolic acid, and preparation method and application thereof

Abstract

This invention belongs to the technical field of catalysts for the electrocatalytic oxidation of ethylene glycol to glycolic acid, specifically a Pt-Pb / NF bimetallic catalyst for this process, its preparation method, and its applications. The catalyst is prepared in an alkaline three-electrode system using nickel foam as the working electrode in an alkaline co-deposition solution containing platinum and lead ions. Cyclic voltammetry is performed within a specific potential window, allowing platinum and lead to co-deposit on a nickel foam substrate. This catalyst exhibits excellent activity and high selectivity for glycolic acid in the electrocatalytic oxidation of ethylene glycol, while simultaneously enabling hydrogen production at the cathode. The catalyst preparation method is simple and controllable, with relatively low cost and good stability, providing a highly efficient electrocatalytic solution for the high-value conversion of ethylene glycol and the co-production of clean energy.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology for the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid, and relates to a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid, its preparation method and application, specifically a Pt-Pb / NF bimetallic catalyst prepared on a nickel foam substrate by cyclic voltammetric co-deposition, and the catalyst can be applied to the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid coupled with hydrogen production. Background Technology

[0002] Ethylene glycol is a crucial chemical raw material in fields such as polyester fibers and antifreeze, with enormous annual consumption. Efficiently converting it into higher value-added products is significant for extending the industrial chain and enhancing economic value. Glycolic acid, as an environmentally friendly α-hydroxy acid, is in increasing demand in areas such as biodegradable materials, personal care products, and pharmaceutical intermediates. Traditional glycolic acid synthesis processes (such as chloroacetic acid hydrolysis and high-pressure carbonylation) generally suffer from harsh conditions, high energy consumption, or environmental pollution. In contrast, the route for directly oxidizing ethylene glycol to prepare glycolic acid offers high atom economy; however, existing thermocatalytic methods typically require both high temperature and high pressure, as well as noble metal catalysts, and face challenges such as difficulty in controlling the selectivity of the target product and easy catalyst deactivation.

[0003] Electrocatalytic conversion technology utilizes electrical energy to drive reactions, can be carried out at ambient temperature and pressure, is clean and controllable, and can be coupled with renewable energy sources, providing a new pathway for the green upgrading of ethylene glycol. In this process, the ethylene glycol oxidation reaction at the anode can be coupled with the water reduction to hydrogen production reaction at the cathode, thereby simultaneously producing two valuable products and improving the energy efficiency and economy of the entire process. However, the electrochemical oxidation pathway of ethylene glycol is complex, easily generating various products such as glycolic acid, glyoxylic acid, oxalic acid, and even carbon dioxide. Therefore, developing anode catalysts with high activity and high selectivity is the core of realizing the application of this technology.

[0004] Currently, platinum (Pt)-based catalysts exhibit certain intrinsic activity in this reaction, but their surfaces are easily poisoned by reaction intermediates, and their selectivity for glycolic acid is often insufficient. Therefore, developing an electrocatalyst with high selectivity for glycolic acid, excellent performance, and stability for the electrocatalytic oxidation of ethylene glycol to glycolic acid has significant research value and application potential. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, along with its preparation method and applications. The catalyst is prepared in an alkaline three-electrode system using nickel foam as the working electrode in an alkaline co-deposition solution containing platinum and lead ions. Cyclic voltammetry is performed within a specific potential window, allowing platinum and lead to co-deposit on a nickel foam substrate. This catalyst exhibits excellent activity and high selectivity for glycolic acid in the electrocatalytic oxidation of ethylene glycol, while also enabling hydrogen production via the counter electrode. The catalyst preparation method of this invention is simple and controllable, with relatively low cost and good stability, providing an efficient electrocatalytic solution for the high-value conversion of ethylene glycol and the co-production of clean energy.

[0006] To achieve the above objectives, the present invention employs a technical solution consisting of the following technical measures.

[0007] In one aspect, the present invention provides a method for preparing a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, mainly comprising the following steps:

[0008] (1) Dissolve soluble platinum salt and soluble lead salt in deionized water and adjust the pH to 13.5~14 to prepare an alkaline co-precipitation solution containing platinum ions and lead ions; the mass ratio of platinum to lead in the alkaline co-precipitation solution containing platinum ions and lead ions is 1:(0.04~0.4).

[0009] (2) Using the alkaline co-deposition solution containing platinum ions and lead ions obtained in step (1) as the electrolyte, a Pt-Pb / NF bimetallic catalyst was prepared by cyclic voltammetric co-deposition method.

[0010] The cyclic voltammetric co-deposition method is performed in an alkaline three-electrode system, using nickel foam as the working electrode, a reference electrode suitable for alkaline electrolytes, and an inert electrode. Cyclic voltammetry is performed with the selected reference electrode as a reference, within a potential difference range of 0.5–0.55 V and a scan rate of 10–50 mV / s, for 20–60 cycles, to co-deposit platinum and lead onto the nickel foam with a platinum loading of 0.1–1.0 mg / cm³. 2 A Pt-Pb / NF bimetallic catalyst was prepared.

[0011] In this article, the soluble platinum salt and soluble lead salt mentioned in step (1) are both conventional platinum salts and lead salts that are soluble in deionized water and are known in common knowledge. Those skilled in the art can directly refer to the selection of platinum salts and lead salts that are suitable for coprecipitation method and whose solvent is deionized water in the prior art.

[0012] To better illustrate the present invention and provide a technical solution for reference, the soluble platinum salt in step (1) is selected from at least one of chloroplatinic acid, chloroplatinate, and platinum nitrate; the soluble lead salt is selected from at least one of lead nitrate, lead chloride, and lead acetate.

[0013] In this article, the adjustment of pH to 13.5-14 in step (1) follows the conventional principle in chemical processes, that is, the pH value of the solution is adjusted by adding alkali or alkaline solution, such as adding sodium hydroxide or potassium hydroxide to adjust the pH to 13.5-14.

[0014] Typically, in step (1), to prepare an alkaline co-precipitation solution containing platinum and lead ions, soluble platinum salts and soluble lead salts are mixed and dissolved in deionized water, and the pH is adjusted to 13.5-14. The order of mixing and dissolving and adjusting the pH can be selected according to actual needs, aiming to obtain a clear and transparent alkaline co-precipitation solution. For example, the soluble platinum and lead salts can be mixed and dissolved in deionized water first, and then the pH can be adjusted to 13.5-14; or an alkaline aqueous solution with a pH of 13.5-14 can be prepared first, and then the soluble platinum and lead salts can be mixed and dissolved in that alkaline aqueous solution. To improve dissolution efficiency, it is preferable to first prepare an alkaline aqueous solution with a pH of 13.5-14 and then mix and dissolve the soluble platinum and lead salts in that alkaline aqueous solution.

[0015] It should be noted that the molar concentrations of platinum and lead ions in the alkaline co-deposition solution containing platinum and lead ions obtained in step (1) will affect the loading of platinum and lead on the nickel foam substrate in the Pt-Pb / NF bimetallic catalyst prepared by cyclic voltammetric co-deposition in step (2). However, the platinum loading has been clearly given in step (2), and the mass ratio of platinum to lead has been given in step (1). Those skilled in the art can select the molar concentrations of platinum and lead ions according to actual needs. For example, to reduce costs and maximize the deposition of platinum in the alkaline co-deposition solution on the nickel foam, the molar concentration of platinum ions can be selected as 0.5~2.0 mM.

[0016] In this document, the size and specifications of the nickel foam described in step (2) follow the conventional selection of nickel foam as an electrode material. For example, in the following embodiments, commercially available nickel foam with a thickness of 1.7 mm was used under laboratory conditions. However, those skilled in the art should know that the specifications of nickel foam usually do not have a significant impact on the technical contribution of this invention. Therefore, the nickel foam used in the following embodiments should not be regarded as a limitation on the selection of nickel foam in this invention.

[0017] In one of the technical solutions, before performing the cyclic voltammetric co-deposition method described in step (2), the nickel foam is further subjected to pretreatment to remove its surface oxide layer and organic impurities. The pretreatment involves ultrasonically treating the nickel foam in a hydrochloric acid solution with a molar concentration of 2 mol / L for 20 min, then ultrasonically treating it in anhydrous ethanol for 20 min, then washing it with deionized water until the washing solution is neutral, and finally drying it at a temperature of 40 °C.

[0018] In this paper, the reference electrode mentioned in step (2) is a reference electrode suitable for alkaline electrolyte. Those skilled in the art can refer to the selection of reference electrode in conventional three-electrode systems under alkaline electrolyte conditions, such as mercury oxide electrode (Hg / HgO).

[0019] In this paper, the counter electrode in step (2) is an inert electrode. Those skilled in the art can refer to the selection of the counter electrode in conventional three-electrode systems under alkaline electrolyte conditions, such as conventional platinum-based electrodes (e.g., platinum sheets), carbon-based electrodes (e.g., graphite rods / carbon rods), or nickel-based electrodes (e.g., nickel sheets).

[0020] Typically, in step (2), a cyclic voltammetric scan is performed with the selected reference electrode as a reference, within a potential difference range of 0.5 to 0.55 V and a scan rate of 10 to 50 mV / s. Those skilled in the art should know from common knowledge that when different reference electrodes are selected, the scan potential range based on the potential difference needs to be adjusted accordingly according to the reduction potential window of the target ion in the selected reference system. For example, when the reference electrode is a mercury oxide electrode (Hg / HgO), the scan potential range is preferably -0.95 V to -0.40 V.

[0021] Typically, during the cyclic voltammetry scan in step (2), stirring is performed to keep the concentration of metal ions in the electrolyte uniform.

[0022] In this paper, the Pt-Pb / NF bimetallic catalyst prepared by cyclic voltammetric co-deposition in step (2) also includes conventional post-treatment, such as taking out the working electrode after loading platinum and lead by cyclic voltammetric co-deposition, washing it with deionized water until the washing solution is neutral, and finally drying it at a temperature of 40 °C.

[0023] In this document, the mixing, ultrasonic treatment, washing, and drying processes all follow conventional principles in chemical processes, and those skilled in the art can perform the specific operations based on common knowledge.

[0024] On the other hand, the present invention also provides the application of the above-mentioned Pt-Pb / NF bimetallic catalyst in the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid.

[0025] In one technical solution, the application of the Pt-Pb / NF bimetallic catalyst in the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid specifically involves using the Pt-Pb / NF bimetallic catalyst as the working electrode in an alkaline three-electrode system, employing an alkaline electrolyte-compatible reference electrode, and using an inert electrode as the counter electrode. An alkaline ethylene glycol solution with a molar concentration of 0.1–2 mol / L and a pH of 13.5–14 is used as the electrolyte. A potential of 0.4–1.2 V relative to the reversible hydrogen electrode (vs. RHE) is applied to the working electrode, resulting in the oxidation of glycolic acid at the working electrode and the simultaneous coupling of a hydrogen evolution reaction to generate hydrogen gas at the counter electrode.

[0026] The present invention has the following beneficial effects:

[0027] 1. This invention provides a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, its preparation method, and its application. The catalyst significantly improves the ethylene glycol oxidation activity and glycolic acid selectivity by loading the Pt-Pb bimetallic active component onto a three-dimensional porous nickel foam substrate and utilizing the synergistic effect of platinum (Pt) and lead (Pb) to regulate the electronic structure, while suppressing side reactions. The nickel foam support enhances mass transfer and electron conduction, thereby improving reaction efficiency.

[0028] 2. The catalyst prepared by the specific cyclic voltammetric co-deposition method described in this invention significantly improves the intrinsic activity of the catalyst without significantly increasing the number of active sites. Compared with traditional preparation methods (such as constant potential electrodeposition and chemical impregnation), it exhibits significantly better electrocatalytic performance under similar platinum and lead ratios and loading conditions, resulting in unexpected technical effects.

[0029] 3. The cyclic voltammetric co-deposition method provided by this invention has clear process parameters and simple operation, which can accurately control the co-deposition process of platinum and lead, ensuring the uniformity and reproducibility of catalyst composition and structure, which is conducive to large-scale preparation. The preparation process is carried out at room temperature and pressure, using water as the medium and hydrogen source, without the need for high temperature and high pressure or external oxidants, making it safe, environmentally friendly and energy-efficient.

[0030] 4. In the Pt-Pb / NF bimetallic catalyst provided by the present invention, the nickel foam support has low cost and high mechanical strength, and the Pt-Pb nanostructure formed by the cyclic voltammetric co-deposition method is firmly bonded to the substrate and has good stability; the introduction of lead, which is less expensive, to partially replace the precious metal platinum further reduces the cost of the catalyst while maintaining high performance.

[0031] 5. The Pt-Pb / NF bimetallic catalyst provided by this invention is applied to the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid. The working electrode converts ethylene glycol into glycolic acid at a high value, while the counter electrode simultaneously produces hydrogen, avoiding the high-energy-consuming oxygen evolution reaction, reducing the cell pressure, and obtaining two high-value-added products at the same time, thereby improving the overall economic benefits. Attached Figure Description

[0032] Figure 1 The figures show a comparison of the ethylene glycol oxidation performance of the Pt-Pb / NF bimetallic catalysts prepared in Examples 1-9 of this invention under different platinum to lead mass ratios. From left to right, the figures correspond to Examples 2, 3, 4, 5, 1, 6, 7, 8, and 9.

[0033] Figure 2 This is a comparison of the linear sweep voltammetry (LSV) test results of the catalyst samples prepared in Example 1 and Comparative Examples 1-5 of this invention. In the figure, NF corresponds to directly using nickel foam as the working electrode.

[0034] Figure 3 The graph shows the Faraday efficiency and yield of the Pt-Pb / NF bimetallic catalyst prepared in Example 1 of this invention for the electrocatalytic oxidation of ethylene glycol to glycolic acid under different potential conditions.

[0035] Figure 4 This is a comparison chart of the electrochemical impedance (EIS) test results of the catalyst samples prepared in Example 1 and Comparative Example 1 of this invention.

[0036] Figure 5 This is a schematic flowchart of a method for preparing a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, according to Example 1 of the present invention.

[0037] Figure 6 This is a scanning electron microscope (SEM) image of the Pt-Pb / NF bimetallic catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0038] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. Those skilled in the art can refer to the content of this document to appropriately improve the process parameters. In particular, it should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate changes and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention. Although it is believed that those skilled in the art will fully understand the following terms, the following definitions are set forth to help illustrate the subject matter disclosed in the present invention.

[0039] In one aspect, the present invention provides a method for preparing a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, mainly comprising the following steps:

[0040] (1) Dissolve soluble platinum salt and soluble lead salt in deionized water and adjust the pH to 13.5~14 to prepare an alkaline co-precipitation solution containing platinum ions and lead ions; the mass ratio of platinum to lead in the alkaline co-precipitation solution containing platinum ions and lead ions is 1:(0.04~0.4).

[0041] (2) Using the alkaline co-deposition solution containing platinum ions and lead ions obtained in step (1) as the electrolyte, a Pt-Pb / NF bimetallic catalyst was prepared by cyclic voltammetric co-deposition method.

[0042] The cyclic voltammetric co-deposition method is performed in an alkaline three-electrode system, using nickel foam as the working electrode, a reference electrode suitable for alkaline electrolytes, and an inert electrode. Cyclic voltammetry is performed with the selected reference electrode as a reference, within a potential difference range of 0.5–0.55 V and a scan rate of 10–50 mV / s, for 20–60 cycles, to co-deposit platinum and lead onto the nickel foam with a platinum loading of 0.1–1.0 mg / cm³. 2 A Pt-Pb / NF bimetallic catalyst was prepared.

[0043] In this article, the soluble platinum salt and soluble lead salt mentioned in step (1) are both conventional platinum salts and lead salts that are soluble in deionized water and are known in common knowledge. Those skilled in the art can directly refer to the selection of platinum salts and lead salts that are suitable for coprecipitation method and whose solvent is deionized water in the prior art.

[0044] To better illustrate the present invention and to provide a possible embodiment for reference, the soluble platinum salt in step (1) is selected from at least one of chloroplatinic acid, chloroplatinate, and platinum nitrate; the soluble lead salt is selected from at least one of lead nitrate, lead chloride, and lead acetate.

[0045] In this article, the adjustment of pH to 13.5-14 in step (1) follows the conventional principle in chemical processes, that is, adjusting the pH of the solution by adding alkali or alkaline solution. In one embodiment, for example, sodium hydroxide or potassium hydroxide is added to adjust the pH to 13.5-14.

[0046] Typically, in step (1), to prepare an alkaline co-precipitation solution containing platinum and lead ions, soluble platinum salts and soluble lead salts are mixed and dissolved in deionized water, and the pH is adjusted to 13.5-14. The order of mixing and dissolving and adjusting the pH can be selected according to actual needs, aiming to obtain a clear and transparent alkaline co-precipitation solution. For example, the soluble platinum and lead salts can be mixed and dissolved in deionized water first, and then the pH can be adjusted to 13.5-14; or an alkaline aqueous solution with a pH of 13.5-14 can be prepared first, and then the soluble platinum and lead salts can be mixed and dissolved in that alkaline aqueous solution. To improve dissolution efficiency, it is preferable to first prepare an alkaline aqueous solution with a pH of 13.5-14 and then mix and dissolve the soluble platinum and lead salts in that alkaline aqueous solution.

[0047] It should be noted that in the alkaline co-deposition solution containing platinum and lead ions obtained in step (1), the molar concentration of platinum and lead ions will affect the loading of platinum and lead on the nickel foam substrate in the Pt-Pb / NF bimetallic catalyst prepared by cyclic voltammetric co-deposition in step (2). However, the platinum loading has been clearly given in step (2), and the mass ratio of platinum to lead has been given in step (1). Those skilled in the art can select the molar concentration of platinum and lead ions according to actual needs. In one embodiment, to reduce costs, platinum is deposited onto the nickel foam in the alkaline co-deposition solution as much as possible. The molar concentration of platinum ions can be selected from 0.5 to 2.0 mM, for example, 0.5 mM, 0.6 mM, 0.7 mM, 0.8 mM, 0.9 mM, 1 mM, 1.1 mM, 1.2 mM, 1.3 mM, 1.4 mM, 1.5 mM, 1.6 mM, 1.7 mM, 1.8 mM, 1.9 mM, 2 mM or any range or point value between them.

[0048] In this document, the size and specifications of the nickel foam described in step (2) follow the conventional selection of nickel foam as an electrode material. For example, in the following embodiments, commercially available nickel foam with a thickness of 1.7 mm was used under laboratory conditions. However, those skilled in the art should know that the specifications of nickel foam usually do not have a significant impact on the technical contribution of this invention. Therefore, the nickel foam used in the following embodiments should not be regarded as a limitation on the selection of nickel foam in this invention.

[0049] In one embodiment, before performing the cyclic voltammetric co-deposition method described in step (2), the nickel foam is further subjected to pretreatment to remove its surface oxide layer and organic impurities. The pretreatment involves ultrasonically treating the nickel foam in a hydrochloric acid solution with a molar concentration of 2 mol / L for 20 min, then ultrasonically treating it in anhydrous ethanol for 20 min, then washing it with deionized water until the washing solution is neutral, and finally drying it at a temperature of 40 °C.

[0050] In this paper, the reference electrode mentioned in step (2) is a reference electrode suitable for alkaline electrolyte. Those skilled in the art can refer to the selection of reference electrode in conventional three-electrode systems under alkaline electrolyte conditions in the prior art. In one embodiment, for example, a mercury oxide electrode (Hg / HgO) is used.

[0051] In this document, the counter electrode described in step (2) is an inert electrode. Those skilled in the art can refer to the selection of the counter electrode in a conventional three-electrode system under alkaline electrolyte conditions in the prior art. In one embodiment, for example, a conventional platinum-based electrode (such as a platinum sheet), a carbon-based electrode (such as a graphite rod / carbon rod), or a nickel-based electrode (such as a nickel sheet) is used.

[0052] Typically, in step (2), a cyclic voltammetric scan is performed with the selected reference electrode as a reference, within a potential difference range of 0.5 to 0.55 V and a scan rate of 10 to 50 mV / s. Those skilled in the art should know from common knowledge that when different reference electrodes are selected, the scan potential range based on the potential difference needs to be adjusted accordingly according to the reduction potential window of the target ion in the selected reference system. In one embodiment, for example, when the reference electrode is a mercury oxide electrode (Hg / HgO), the scan potential range is preferably -0.95 V to -0.40 V.

[0053] Typically, during the cyclic voltammetry scan in step (2), stirring is performed to keep the concentration of metal ions in the electrolyte uniform.

[0054] In one embodiment, the platinum loading in the Pt-Pb / NF bimetallic catalyst in step (2) is 0.1~1.0 mg / cm³. 2For example, 0.1 mg / cm 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 2 0.9 mg / cm 2 1 mg / cm 2 Or any range or point value between them.

[0055] In this paper, the Pt-Pb / NF bimetallic catalyst prepared by cyclic voltammetric co-deposition in step (2) also includes conventional post-treatment. In one embodiment, for example, the working electrode loaded with platinum and lead by cyclic voltammetric co-deposition is taken out, washed with deionized water until the washing solution is neutral, and finally dried at a temperature of 40 °C.

[0056] In this document, the mixing, ultrasonic treatment, washing, and drying processes all follow conventional principles in chemical processes, and those skilled in the art can perform the specific operations based on common knowledge.

[0057] On the other hand, the present invention also provides the application of the above-mentioned Pt-Pb / NF bimetallic catalyst in the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid.

[0058] In one embodiment, the application of the Pt-Pb / NF bimetallic catalyst in the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid specifically involves using the Pt-Pb / NF bimetallic catalyst as the working electrode in an alkaline three-electrode system. A reference electrode suitable for alkaline electrolytes is used, and an inert electrode is used as the counter electrode. An alkaline ethylene glycol solution with a molar concentration of 0.1–2 mol / L and a pH of 13.5–14 is used as the electrolyte. A potential of 0.4–1.2 V relative to the reversible hydrogen electrode (vs. RHE) is applied to the working electrode, resulting in the oxidation of glycolic acid at the working electrode and the simultaneous coupling of a hydrogen evolution reaction to generate hydrogen gas at the counter electrode.

[0059] The present application will be further explained in detail below with reference to embodiments. However, those skilled in the art should understand that these embodiments are provided for illustrative purposes only and are not intended to limit the present application.

[0060] Example

[0061] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the scope of this application. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all commercially available conventional products. This application should not be construed as being limited to the specific embodiments described.

[0062] 1. Raw materials

[0063] Commercial nickel foam (1.7 mm thick, purchased from CyberElectrochemical Materials Network) was cut into 2 cm × 4 cm sheets. These sheets were then ultrasonically cleaned sequentially in 2 M hydrochloric acid solution and anhydrous ethanol for 20 minutes each to thoroughly remove the surface oxide layer and organic impurities. Subsequently, they were repeatedly rinsed with ultrapure water until the washing solution was neutral, and then dried completely in an oven at 40 °C. This dried nickel foam was then prepared for use in the following examples and comparative examples.

[0064] 2. Testing Methods

[0065] A three-electrode system was assembled using the catalyst sample as the working electrode, a platinum sheet as the counter electrode, and a mercuric oxide electrode (Hg / HgO) as the reference electrode; the electrolyte was a 1 M KOH solution containing 0.5 M ethylene glycol.

[0066] Linear sweep voltammetry (LSV) testing: LSV testing was performed at a scan rate of 20 mV / s over a potential range of 0 V to 1.5 V (relative to the reversible hydrogen electrode, vs. RHE), and the current-potential curves were recorded.

[0067] Electrochemical impedance spectroscopy (EIS) test: The AC impedance method was used, with the initial frequency set at 100 kHz, the termination frequency at 0.01 Hz, and the AC disturbance signal amplitude at 10 mV. The measurement was performed at a potential of -0.324 V (vs. Hg / HgO) after the open circuit stabilized.

[0068] The platinum loading was determined by inductively coupled plasma (ICP) testing of the catalyst sample, as provided by the Sichuan Provincial Institute of Energy Geology Survey.

[0069] Example 1

[0070] Example 1: A method for preparing a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, mainly including the following steps:

[0071] (1) Weigh out chloroplatinic acid hexahydrate (H2PtCl6·6H2O) and lead chloride (PbCl2), dissolve them together in 1 M KOH solution, and prepare an alkaline co-precipitation solution with a platinum ion concentration of 0.615 mM and a platinum to lead mass ratio of 0.6:0.13;

[0072] (2) Using the alkaline co-deposition solution obtained in step (1) as the electrolyte, a Pt-Pb / NF bimetallic catalyst was prepared by cyclic voltammetric co-deposition method;

[0073] The cyclic voltammetric co-deposition method was performed in an alkaline three-electrode system, using nickel foam as the working electrode, a mercury oxide electrode (Hg / HgO) as the reference electrode, and a platinum sheet as the counter electrode. Cyclic voltammetry was performed with the selected reference electrode as a reference, at a scan potential range of -0.924 V to -0.424 V (i.e., minimum potential of -0.924 V and maximum potential of -0.424 V) and a scan rate of 20 mV / s, for 40 cycles, to co-deposit platinum and lead onto the nickel foam. The working electrode was then removed, washed with deionized water until the washing solution was neutral, and finally dried at 40 °C, yielding a platinum loading of approximately 0.6 mg / cm³. 2 The Pt-Pb / NF bimetallic catalyst was used as a sample for testing.

[0074] Comparative Example 1

[0075] Comparative Example 1 used the same cyclic voltammetric co-deposition method as Example 1, but without the addition of lead as a control. The main steps included were as follows:

[0076] (1) Weigh out chloroplatinic acid hexahydrate (H2PtCl6·6H2O), dissolve it in 1 M KOH solution, and prepare an alkaline precipitation solution with a platinum ion concentration of 0.615 mM;

[0077] (2) Using the alkaline deposition solution obtained in step (1) as the electrolyte, a Pt / NF catalyst was prepared by cyclic voltammetric co-deposition method;

[0078] The cyclic voltammetric co-deposition method was performed in an alkaline three-electrode system, using nickel foam as the working electrode, a mercury oxide electrode (Hg / HgO) as the reference electrode, and a platinum sheet as the counter electrode. Cyclic voltammetry was conducted with the selected reference electrode as a reference, at a scan potential range of -0.924 V to -0.424 V (i.e., minimum potential -0.924 V, maximum potential -0.424 V) and a scan rate of 20 mV / s, accompanied by mechanical stirring (500 rad / min), for 40 cycles to deposit platinum onto the nickel foam. The working electrode was then removed, washed with deionized water until the washing solution was neutral, and finally dried at 40 °C to obtain a platinum loading of approximately 0.6 mg / cm³. 2 The Pt / NF catalyst was used as a sample for testing.

[0079] The LSV curves show that, at a potential of 0.9 V (vs. RHE), the mass-activity current density of the Pt-Pb / NF bimetallic catalyst obtained in Example 1 for the oxidation of ethylene glycol is approximately 1.25 A mg. -1 Pt, compared to the Pt / NF catalyst in Comparative Example 1 (0.27 A mg) -1 Pt), the activity was increased by about 4.6 times.

[0080] Example 2

[0081] Example 2 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.026. Finally, the Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0082] Example 3

[0083] Example 3 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.052. Finally, the Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0084] Example 4

[0085] Example 4 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.078. Finally, the Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0086] Example 5

[0087] Example 5 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.104. Finally, the Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0088] Example 6

[0089] Example 6 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.156. Finally, a Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0090] Example 7

[0091] Example 7 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.182. Finally, the Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0092] Example 8

[0093] Example 8 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.208. Finally, the Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0094] Example 9

[0095] Example 9 is prepared according to the method of Example 1, but the amount of lead chloride added in step (1) is adjusted so that the mass ratio of platinum to lead in the alkaline co-precipitation solution obtained in step (1) is 0.6:0.234. Finally, a Pt-Pb / NF bimetallic catalyst is prepared as a sample for testing.

[0096] Comparative Example 2

[0097] Comparative Example 2 uses the same platinum to lead ratio and loading as Example 1, but is prepared using a constant potential electrodeposition method as a comparison. The main steps include:

[0098] (1) Weigh out chloroplatinic acid hexahydrate (H2PtCl6·6H2O) and lead chloride (PbCl2), dissolve them together in 1 M KOH solution, and prepare an alkaline co-precipitation solution with a platinum ion concentration of 0.615 mM and a platinum to lead mass ratio of 0.6:0.13;

[0099] (2) Using the alkaline co-deposition solution obtained in step (1) as the electrolyte, a Pt-Pb / NF bimetallic catalyst was prepared by constant potential deposition method;

[0100] The potentiostatic deposition method was performed in an alkaline three-electrode system, using nickel foam as the working electrode, a mercury oxide electrode (Hg / HgO) as the reference electrode, and a platinum sheet as the counter electrode. A constant potential of -0.6V was applied with mechanical stirring (500 rad / min) based on the selected reference electrode, and the deposition time was 33 minutes (the same as the total time of 40 cycles of cyclic voltammetry in Example 1), allowing platinum and lead to co-deposit on the nickel foam. The working electrode was then removed, washed with deionized water until the washing solution was neutral, and finally dried at 40 °C to obtain a platinum loading of approximately 0.6 mg / cm³. 2 The Pt-Pb / NF bimetallic catalyst was used as a sample for testing.

[0101] Comparative Example 3

[0102] Comparative Example 3 uses the same potentiostatic electrodeposition method as Comparative Example 2, but without the addition of lead as a control. The main steps include:

[0103] (1) Weigh out chloroplatinic acid hexahydrate (H2PtCl6·6H2O), dissolve it in 1 M KOH solution, and prepare an alkaline precipitation solution with a platinum ion concentration of 0.615 mM;

[0104] (2) Using the alkaline deposition solution obtained in step (1) as the electrolyte, Pt / NF catalyst was prepared by constant potential deposition method;

[0105] The potentiostatic deposition method was performed in an alkaline three-electrode system, using nickel foam as the working electrode, a mercury oxide electrode (Hg / HgO) as the reference electrode, and a platinum sheet as the counter electrode. A constant potential of -0.6V was applied with mechanical stirring (500 rad / min) based on the selected reference electrode, and the deposition time was 33 minutes (the same as the total time of 40 cycles of cyclic voltammetry in Example 1), allowing platinum to be deposited on the nickel foam. The working electrode was then removed, washed with deionized water until the washing solution was neutral, and finally dried at 40 °C to obtain a platinum loading of approximately 0.6 mg / cm³. 2 The Pt / NF catalyst was used as a sample for testing.

[0106] Comparative Example 4

[0107] Comparative Example 4 uses the same platinum to lead ratio as Example 1, but is prepared using a chemical impregnation method as a comparison, mainly including the following steps:

[0108] (1) Weigh out chloroplatinic acid hexahydrate (H2PtCl6·6H2O) and lead chloride (PbCl2), dissolve them together in 1 M KOH solution, and prepare an alkaline co-precipitation solution with a platinum ion concentration of 0.615 mM and a platinum to lead mass ratio of 0.6:0.13;

[0109] (2) Nickel foam (2 cm × 4 cm) was directly impregnated in the alkaline co-deposition solution obtained in step (1) to prepare a Pt-Pb / NF bimetallic catalyst by chemical impregnation.

[0110] The chemical impregnation method specifically involves: completely immersing nickel foam in an alkaline co-deposition solution and impregnating it for 33 minutes at room temperature (25±2℃) with mechanical stirring (500 rad / min) (the same total time as the 40 cycles of cyclic voltammetry scanning in Example 1), so that platinum and lead are co-deposited on the nickel foam; then the deposited product is removed, repeatedly washed with deionized water until the washing solution is neutral, and finally dried at 40℃ to prepare a Pt-Pb / NF bimetallic catalyst as a sample for testing.

[0111] During the above preparation process, the alkaline co-deposition solution remained visibly pale yellow throughout. In contrast, the alkaline co-deposition solution gradually changed from pale yellow to transparent and colorless during cyclic voltammetric co-deposition and potentiostatic electrodeposition methods. This indicates that metal ions are difficult to effectively deposit on the nickel foam surface without an electric field, and its platinum loading is estimated to be approximately 0.1 mg / cm³. 2 .

[0112] Comparative Example 5

[0113] Comparative Example 5 used the same chemical impregnation method as Comparative Example 4, but without adding lead as a control. The main steps included were:

[0114] (1) Weigh out chloroplatinic acid hexahydrate (H2PtCl6·6H2O), dissolve it in 1 M KOH solution, and prepare an alkaline precipitation solution with a platinum ion concentration of 0.615 mM;

[0115] (2) Nickel foam (2 cm × 4 cm) was directly impregnated in the alkaline deposition solution obtained in step (1) to prepare Pt / NF catalyst by chemical impregnation method;

[0116] The chemical impregnation method specifically involves: completely immersing nickel foam in an alkaline deposition solution and impregnating it for 33 minutes at room temperature (25±2 ℃) with mechanical stirring (500 rad / min) (the same total time as the 40 cycles of cyclic voltammetry scanning in Example 1) to deposit platinum onto the nickel foam; then removing the deposited product and repeatedly washing it with deionized water until the washing solution is neutral; finally, drying it at 40 ℃ to prepare the Pt / NF catalyst as a sample for testing.

[0117] During the above preparation process, the alkaline deposition solution remained visibly pale yellow throughout. In contrast, the alkaline co-deposition solution gradually changed from pale yellow to transparent and colorless during the cyclic voltammetric co-deposition and constant potential electrodeposition methods. This indicates that metal ions are difficult to effectively deposit on the nickel foam surface without an electric field, and its platinum loading is estimated to be approximately 0.1 mg / cm³. 2 .

[0118] Test results are as follows Figures 1-6 As shown:

[0119] from Figure 1 It is evident that under specific conditions, the prepared Pt-Pb / NF bimetallic catalyst exhibits significantly better catalytic activity when the mass ratio of platinum to lead in the alkaline co-deposition solution is 0.6:(0.078~0.156), with the most preferred ratio being 0.6:0.13.

[0120] from Figure 2 It is evident that only under the conditions of platinum and lead co-deposition and preparation by cyclic voltammetric co-deposition, the catalyst sample obtained in Example 1 exhibits significantly better catalytic activity, with a marked improvement compared to Comparative Examples 1-5, resulting in unexpected technical effects.

[0121] based on Figure 3 The Faraday efficiency and yield diagrams of the catalyst sample in Example 1 for the electrocatalytic oxidation of ethylene glycol to glycolic acid under different potential conditions demonstrate its high selectivity for glycolic acid; and the Faraday efficiency and yield are optimal when a potential of 0.9 V relative to the reversible hydrogen electrode (vs. RHE) is applied to the working electrode.

[0122] like Figure 4 As shown, the electrochemical impedance spectroscopy (EIS) results indicate that the charge transfer resistance (Ro) of the Pt-Pb / NF bimetallic catalyst obtained in Example 1 is [missing information]. ct The Ω is approximately 0.455 Ω, which is significantly lower than the 2.803 Ω of the Pt / NF catalyst obtained in Comparative Example 1.

[0123] Figure 5 ,6 A schematic diagram of the preparation process in Example 1 and a scanning electron microscope (SEM) image of the prepared Pt-Pb / NF bimetallic catalyst are shown.

[0124] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a Pt-Pb / NF bimetallic catalyst for the electrocatalytic oxidation of ethylene glycol to glycolic acid, characterized in that... The main steps include: (1) Dissolve soluble platinum salt and soluble lead salt in deionized water and adjust the pH to 13.5~14 to prepare an alkaline co-precipitation solution containing platinum ions and lead ions; the mass ratio of platinum to lead in the alkaline co-precipitation solution containing platinum ions and lead ions is 1:(0.04~0.4). (2) Using the alkaline co-deposition solution containing platinum ions and lead ions obtained in step (1) as the electrolyte, a Pt-Pb / NF bimetallic catalyst was prepared by cyclic voltammetric co-deposition method. The cyclic voltammetric co-deposition method is performed in an alkaline three-electrode system, using nickel foam as the working electrode, a reference electrode suitable for alkaline electrolytes, and an inert electrode. Cyclic voltammetry is performed with the selected reference electrode as a reference, within a potential difference range of 0.5–0.55 V and a scan rate of 10–50 mV / s, for 20–60 cycles, to co-deposit platinum and lead onto the nickel foam with a platinum loading of 0.1–1.0 mg / cm³. 2 A Pt-Pb / NF bimetallic catalyst was prepared.

2. The preparation method according to claim 1, characterized in that: The soluble platinum salt mentioned in step (1) includes at least one of chloroplatinic acid, chloroplatinate, and platinum nitrate; the soluble lead salt includes at least one of lead nitrate, lead chloride, and lead acetate.

3. The preparation method according to claim 1, characterized in that: The molar concentration of platinum ions in the alkaline co-precipitation solution in step (1) is 0.5~2.0 mM.

4. The preparation method according to claim 1, characterized in that: The reference electrode mentioned in step (2) includes a mercury oxide electrode.

5. The preparation method according to claim 1, characterized in that: The counter electrode mentioned in step (2) includes a platinum-based electrode, a carbon-based electrode, or a nickel-based electrode.

6. The preparation method according to claim 1, characterized in that: In step (2), when the reference electrode is a mercury oxide electrode, the scanning potential range is -0.95 V to -0.40 V.

7. The Pt-Pb / NF bimetallic catalyst prepared by the method described in claim 1 for the electrocatalytic oxidation of ethylene glycol to glycolic acid.

8. The Pt-Pb / NF bimetallic catalyst as described in claim 7 is applied to the electrocatalytic oxidation of ethylene glycol to prepare glycolic acid coupled with hydrogen production.

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