Preparation of a NiCo2O4@Ni(OH)2 electrocatalytic material and its application in electrocatalytic oxidation of cyclopentanone to glutaric acid

Abstract

This application belongs to the field of electrocatalysis technology, specifically the preparation of a NiCo2O4@Ni(OH)2 electrocatalytic material and its application in the electrocatalytic oxidation of cyclopentanone to glutaric acid. The preparation method steps are as follows: (1) Dissolve nickel salt, cobalt salt and urea in deionized water, stir to obtain a homogeneous solution, place the conductive substrate in the homogeneous solution, carry out hydrothermal reaction, and naturally cool to obtain a conductive substrate for growing NiCo-OH precursor; (2) Calcine the conductive substrate for growing NiCo-OH precursor to obtain a conductive substrate for growing NiCo2O4 nanowire array; (3) Place the conductive substrate for growing NiCo2O4 nanowire array in a nickel salt solution for hydrothermal treatment to obtain a NiCo2O4@Ni(OH)2 electrocatalytic material with core-shell structure. NiCo2O4 nanoarrays were obtained by hydrothermal and calcination methods; nickel hydroxide was further grown by hydrothermal treatment to construct a NiCo2O4@Ni(OH)2 core-shell structure in situ; thanks to the electron rearrangement at the PN junction interface and the core-shell structure, the NiCo2O4@Ni(OH)2 electrocatalytic material exhibits excellent performance in the electrooxidation of cyclopentanone to glutaric acid.

Description

Technical Field

[0001] This application belongs to the field of electrocatalysis technology, specifically the preparation of a NiCo2O4@Ni(OH)2 electrocatalytic material and its application in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid. Background Technology

[0002] Glutaric acid is an important dicarboxylic acid widely used in bio-based materials (such as polyamides), pharmaceuticals (such as antiepileptic drugs), food additives (such as monosodium glutamate), and organic synthesis. Its synthesis methods are of great significance to industrial production. Industrially, glutaric acid is mainly produced through the oxidation of cyclopentanone. However, the oxidation of cyclopentanone usually relies on strong oxidizing agents (such as potassium permanganate, nitric acid, etc.), which leads to high energy consumption and environmental pollution.

[0003] Electrocatalytic oxidation of cyclopentanone to glutaric acid is an emerging green synthetic technology. On the one hand, the electricity can be sourced from renewable energy sources; on the other hand, the reaction conditions are mild (room temperature and pressure) and require no external oxidant, reducing pollution. However, currently reported electrocatalytic materials still suffer from poor activity and selectivity, making efficient synthesis of glutaric acid at high current densities a significant challenge. Therefore, developing inexpensive and efficient electrocatalysts is key to achieving low-cost conversion of cyclopentanone to glutaric acid. Summary of the Invention

[0004] To address the problems of the prior art, this application provides a method for preparing NiCo2O4@Ni(OH)2 electrocatalytic material and its application in the electrocatalytic oxidation of cyclopentanone to glutaric acid. This method is achieved through the following approach:

[0005] A method for preparing NiCo2O4@Ni(OH)2 electrocatalytic material, the preparation steps are as follows: (1) Dissolve nickel salt, cobalt salt and urea in deionized water, stir evenly to obtain a homogeneous solution, place the conductive substrate in the homogeneous solution, carry out hydrothermal reaction, and naturally cool to obtain a conductive substrate for growing NiCo-OH precursor; (2) Calcine the conductive substrate for growing NiCo-OH precursor to obtain a conductive substrate for growing NiCo2O4 nanowire array; (3) Place the conductive substrate for growing NiCo2O4 nanowire array in nickel salt solution for hydrothermal treatment to obtain NiCo2O4@Ni(OH)2 electrocatalytic material with core-shell structure.

[0006] Furthermore, the conductive substrate is one or more of nickel foam, cobalt foam, carbon paper, and carbon cloth; the conductive substrate is cleaned sequentially with hydrochloric acid, acetone, ethanol, or ultrasonically before being added to the homogeneous solution.

[0007] Furthermore, the molar ratio of the cobalt salt, nickel salt, and urea is 2:1-3:4-6.

[0008] Furthermore, the hydrothermal reaction is carried out at a temperature of 115-125°C for 5-12 hours; the calcination is carried out at a temperature of 200-600°C for 11-13 hours; and the hydrothermal treatment is carried out at a temperature of 60-180°C for 1.5-8.5 hours.

[0009] Furthermore, the hydrothermal reaction is carried out at a temperature of 120°C for a duration of 6 hours.

[0010] Furthermore, the nickel salt solution is an aqueous solution containing nickel salt and dimethylimidazole, wherein the concentration of nickel salt is 3-4 mol / L and the concentration of dimethylimidazole is 2-3 mol / L.

[0011] This application also provides a NiCo2O4@Ni(OH)2 electrocatalytic material prepared according to the above method. The NiCo2O4@Ni(OH)2 electrocatalytic material is supported by a conductive substrate. The core-shell structure has NiCo2O4 nanowires inside and Ni(OH)2 ultrathin nanosheets outside.

[0012] Preferably, the NiCo2O4@Ni(OH)2 electrocatalytic material is used in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid.

[0013] More preferably, the application of the NiCo2O4@Ni(OH)2 electrocatalytic material in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid is as follows: the NiCo2O4@Ni(OH)2 electrocatalytic material is used as the working electrode, the carbon rod is used as the counter electrode, and the mercuric oxide electrode is used as the reference electrode. Electrocatalytic oxidation is carried out at room temperature, and the electrolyte solution is 1M KOH solution.

[0014] Finally, the electrolyte solution also contains cyclopentanone at a concentration of 0.1 M.

[0015] Beneficial effects: First, NiCo2O4 nanoarrays were obtained by hydrothermal and calcination methods; then, nickel hydroxide was grown by hydrothermal treatment to construct a NiCo2O4@Ni(OH)2 core-shell structure in situ; thanks to the electron rearrangement at the PN junction interface and the core-shell structure, the NiCo2O4@Ni(OH)2 electrocatalytic material has excellent performance in the electro-oxidation of cyclopentanone to glutaric acid.

[0016] The NiCo2O4@Ni(OH)2 heterojunction, composed of a core-shell structure, with NiCo2O4 nanowires inside and Ni(OH)2 ultrathin nanosheets outside, provides more active sites and better mass transport capabilities. Furthermore, the unique PN junction built-in electric field formed between the NiCo2O4 nanowires and Ni(OH)2 nanosheets reduces the thermodynamic energy barrier generated by the high-valence NiOOH active material, and significantly improves the activity of cyclopentanone oxidation to glutaric acid.

[0017] Benefiting from the strong electronic interactions between the core-shell structure and the heterogeneous interface, the NiCo2O4@Ni(OH)2 electrocatalyst exhibits excellent cyclopentanone oxidation performance under industrial current, and the overpotential is significantly reduced compared to single-component Ni(OH)2. NMR and IR spectra indicate that cyclopentanone is efficiently oxidized to glutaric acid. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some preferred embodiments of this application, and not all embodiments. For those skilled in the art, other embodiments and drawings can be obtained based on these preferred embodiments and drawings without creative effort, and all of these fall within the protection scope of this application.

[0019] Figure 1 This is a SEM image of the nickel foam with Ni(OH)2 nanosheets grown in the embodiments of this application;

[0020] Figure 2 This is a SEM image of nickel foam with NiCo2O4 nanowires grown in the embodiments of this application;

[0021] Figure 3 The image shows a SEM image of the NiCo2O4@Ni(OH)2 electrocatalytic material in the embodiments of this application.

[0022] Figure 4 The images show the XRD patterns of Ni(OH)2 nanosheets, NiCo2O4 nanowires, and NiCo2O4@Ni(OH)2 core-shell structures in the embodiments of this application.

[0023] Figure 5 Polarization curves of Ni(OH)2, NiCo2O4 and NiCo2O4@Ni(OH)2 electrocatalytic materials prepared for the embodiments of this application during the electrocatalytic oxygen evolution and cyclopentanone oxidation processes;

[0024] Figure 6 The It (a) curve, NMR spectrum (b), and IR spectrum (c) of the NiCo2O4@Ni(OH)2 electrocatalytic material prepared for the embodiments of this application during the electrocatalytic oxidation of cyclopentanone. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below. It should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. The foregoing definitions are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the structure referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0026] Example 1

[0027] A method for preparing NiCo2O4@Ni(OH)2 electrocatalytic material, the preparation steps are as follows:

[0028] (1) Cut a 2cm×4cm foam nickel conductive substrate, then clean it with hydrochloric acid, acetone and ethanol for 10 minutes each, and finally store it in ethanol solvent for later use.

[0029] 0.29 g (1 mmol) of nickel nitrate hexahydrate, 0.581 g (2 mmol) of cobalt nitrate hexahydrate, and 0.6 g (10 mmol) of urea were dissolved in 40 mL of deionized water and stirred for 20 minutes to obtain a homogeneous solution. The homogeneous solution was transferred to a 50 mL polytetrafluoroethylene-lined reactor, and the cleaned nickel foam was placed in the reactor. The reactor was subjected to a hydrothermal reaction at 120 °C for 6 hours and then allowed to cool naturally to obtain a NiCo-OH precursor that was uniformly grown on the nickel foam.

[0030] (2) The nickel foam with NiCo-OH precursor was placed in a magnetic boat and heat-treated at 450°C for 2 hours in air atmosphere to obtain nickel foam with NiCo2O4 nanowires grown.

[0031] (3) Prepare a 35 mL aqueous solution of nickel salt containing 0.125 mmol nickel nitrate and 0.1 mmol dimethylimidazole. Place the nickel foam on which the NiCo2O4 nanowire array is grown into the aqueous solution of nickel salt, and then place it in a 50 mL polytetrafluoroethylene-lined reactor. Perform a hydrothermal reaction at 180 °C for 6 hours and allow it to cool naturally to obtain the NiCo2O4@Ni(OH)2 core-shell structure electrocatalytic material.

[0032] like Figure 2 As shown, nanoneedle-shaped NiCo2O4 is uniformly grown on nickel foam;

[0033] like Figure 3 As shown, a NiCo2O4@Ni(OH)2 core-shell structure was formed after secondary hydrothermal treatment;

[0034] like Figure 4As shown, the XRD patterns demonstrate the successful preparation of Ni(OH)2, NiCo2O4, and NiCo2O4@Ni(OH)2 nanostructures.

[0035] Comparative Example 1

[0036] Cut a 2cm×4cm foam nickel conductive substrate, then ultrasonically clean it for 10 minutes each with hydrochloric acid, acetone and ethanol, and finally store it in ethanol solvent for later use.

[0037] Prepare a 35 mL aqueous solution of nickel salt containing 0.125 mmol nickel nitrate and 0.1 mmol dimethylimidazole. Place the nickel foam into the nickel salt aqueous solution, then place it in a 50 mL polytetrafluoroethylene-lined reactor. Incubate the reactor hydrothermally at 180°C for 6 hours, followed by natural cooling to obtain the desired product. Figure 1 The Ni(OH)2 nanosheets shown are uniformly distributed on the nickel foam.

[0038] Comparative Example 2

[0039] Using a three-electrode electrolytic cell, electrocatalytic oxidation was tested at room temperature with Ni(OH)₂, NiCo₂O₄, and the NiCo₂O₄@Ni(OH)₂ electrocatalytic material prepared in Example 1 as the working electrode, a carbon rod as the counter electrode, a mercury oxide electrode as the reference electrode, and 1 M KOH solution as the electrolyte solution. The results are as follows: Figure 5 As shown in (a), compared with the single-component Ni(OH)2 and NiCo2O4, the core-shell structure of NiCo2O4@Ni(OH)2 has a larger oxidation peak, indicating that it is easier to form high-valence NiOOH active substances on its surface.

[0040] Example 2

[0041] Based on Comparative Example 2, the concentration of KOH in the electrolyte solution was 1M, the concentration of cyclopentanone was 0.1M, and everything else was the same as in Comparative Example 2. The resulting structure is as follows. Figure 5 As shown in (b), the oxidation current density increased significantly after the addition of cyclopentanone, indicating that the cyclopentanone oxidation reaction proceeded. It is noteworthy that NiCo2O4@Ni(OH)2 still exhibits superior cyclopentanone oxidation performance compared to the monocomponent, driving approximately 450 mA / cm² at 1.6 V. -2 Industrial-grade current density.

[0042] Example 3

[0043] A three-electrode electrolytic cell was used, with the NiCo2O4@Ni(OH)2 electrocatalyst material prepared in Example 1 as the working electrode, a carbon rod as the counter electrode, and a mercuric oxide electrode as the reference electrode. The concentration of KOH in the electrolyte solution was 1M, and the concentration of cyclopentanone was 0.1M. It was tested at room temperature, and the results are as follows: Figure 6 (a) and the products after electrolysis were analyzed using nuclear magnetic resonance and infrared spectroscopy, and the results are as follows: Figure 6 (b) and Figure 6 (c); The results show that the NiCo2O4@Ni(OH)2 core-shell structure can stably oxidize cyclopentanone to glutaric acid.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications or substitutions should be covered within the scope of the claims of this application.

Claims

1. A method for preparing a NiCo2O4@Ni(OH)2 electrocatalytic material, characterized in that, The preparation steps are as follows: (1) Dissolve nickel salt, cobalt salt and urea in deionized water, stir until homogeneous to obtain a homogeneous solution, place the conductive substrate in the homogeneous solution, perform hydrothermal reaction, and naturally cool to obtain a conductive substrate for growing NiCo-OH precursor; (2) Calcine the conductive substrate for growing NiCo-OH precursor to obtain a conductive substrate for growing NiCo2O4 nanowire array; (3) Place the conductive substrate for growing NiCo2O4 nanowire array in a nickel salt solution for hydrothermal treatment to obtain The material is a NiCo2O4@Ni(OH)2 electrocatalytic material with a core-shell structure; the hydrothermal reaction is carried out at a temperature of 115~125℃ for 5~12h; the calcination is carried out at a temperature of 200~600℃ for 11~13h; the hydrothermal treatment is carried out at a temperature of 60~180℃ for 1.5~8.5h; the nickel salt solution is an aqueous solution containing nickel salt and dimethylimidazole, with the concentration of nickel salt being 3-4mol / L and the concentration of dimethylimidazole being 2-3mol / L.

2. The preparation method of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 1, characterized in that, The conductive substrate is one or more of nickel foam, cobalt foam, carbon paper, and carbon cloth; the conductive substrate is cleaned sequentially with hydrochloric acid, acetone, ethanol, or ultrasonically before being added to the homogeneous solution.

3. The preparation method of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 1, characterized in that, The molar ratio of the cobalt salt, nickel salt, and urea is 2:1-3:4-6.

4. The preparation method of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 1, characterized in that, The hydrothermal reaction was carried out at a temperature of 120°C for 6 hours.

5. The NiCo2O4@Ni(OH)2 electrocatalytic material prepared by the method according to any one of claims 1-4, characterized in that, The NiCo2O4@Ni(OH)2 electrocatalytic material is supported by a conductive substrate. The core-shell structure consists of NiCo2O4 nanowires inside and Ni(OH)2 ultrathin nanosheets outside.

6. The application of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 5 in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid.

7. The application of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 6 in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid, characterized in that, Specifically, the NiCo2O4@Ni(OH)2 electrocatalytic material is used as the working electrode, the carbon rod is used as the counter electrode, and the mercury oxide electrode is used as the reference electrode. Electrocatalytic oxidation is carried out at room temperature, and the electrolyte solution is 1 M KOH solution.

8. The application of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 7 in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid, characterized in that, The electrolyte solution also contains cyclopentanone, and the concentration of cyclopentanone is 0.1M.

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