Preparation of NiCo2O4-Ni (OH) 2 electro-catalysis material and application of NiCo2O4-Ni (OH) 2 electro-catalysis material in preparation of glutaric acid through electro-catalysis of cyclopentanone oxidation

Abstract

The invention belongs to the technical field of electro-catalysis, and particularly relates to preparation of a NiCo2O4-Ni (OH) 2 electro-catalysis material and application of the NiCo2O4-Ni (OH) 2 electro-catalysis material in preparation of glutaric acid through electro-catalysis cyclopentanone oxidation.The preparation method comprises the following steps that 1, nickel salt, cobalt salt and urea are dissolved in deionized water and stirred to be uniform, a uniform solution is obtained, a conductive substrate is placed in the uniform solution, a hydrothermal reaction is conducted, and a NiCo2O4-Ni (OH) 2 electro-catalysis material is obtained; naturally cooling to obtain a conductive substrate on which a NiCo-OH precursor grows; (2) calcining the conductive substrate on which the NiCo-OH precursor is grown to obtain a conductive substrate on which the NiCo2O4 nanowire array is grown; and (3) putting the conductive substrate on which the NiCo2O4 nanowire array grows into a nickel salt solution for hydrothermal treatment to obtain the NiCo2O4-coated Ni (OH) 2 electro-catalytic material with the core-shell structure. A NiCo2O4 nano array is obtained through a hydrothermal method and a calcination method; growing nickel hydroxide by further adopting hydrothermal treatment, and constructing a NiCo2O4-coated Ni (OH) 2 core-shell structure in situ; benefited from PN junction interface electron rearrangement and a core-shell structure, the NiCo2O4-Ni (OH) 2 electrocatalytic material has excellent performance of preparing glutaric acid through cyclopentanone electrooxidation.

Description

Technical Field

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

[0002] Glutaric acid is an important dicarboxylic acid, which is 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 method is of great significance to industrial production. Industrially, glutaric acid is mainly produced through the oxidation reaction of cyclopentanone, and the oxidation of cyclopentanone usually relies on strong oxidants (such as potassium permanganate, nitric acid, etc.), which have problems such as high energy consumption and environmental pollution.

[0003] The electrocatalytic oxidation of cyclopentanone to prepare glutaric acid is a new green synthesis technology. On the one hand, the source of electric energy can come from renewable energy. On the other hand, the reaction conditions are mild (room temperature and normal pressure) without the need for an external oxidant, reducing pollution. However, the electrocatalytic materials reported currently still have problems of poor activity and selectivity, resulting in great challenges in the efficient synthesis of glutaric acid at high current densities. Therefore, developing inexpensive and efficient electrocatalysts is the key to realizing the low-cost conversion of cyclopentanone to glutaric acid. Summary of the Invention

[0004] In order to solve the problems of the prior art, this application provides the preparation of a NiCo2O4@Ni(OH)2 electrocatalytic material and its application in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid. This application is achieved through the following scheme: A preparation method of a 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 uniform solution, place the conductive substrate in the uniform solution, carry out a hydrothermal reaction, and naturally cool to obtain a conductive substrate with a NiCo-OH precursor grown on it; (2) Carry out a calcination treatment on the conductive substrate with the NiCo-OH precursor grown on it to obtain a conductive substrate with a NiCo2O4 nanowire array grown on it; (3) Place the conductive substrate with the NiCo2O4 nanowire array grown on it in a nickel salt solution for hydrothermal treatment to obtain a NiCo2O4@Ni(OH)2 electrocatalytic material with a core-shell structure.

[0005] Further, the conductive substrate is one or more of nickel foam, cobalt foam, carbon paper, and carbon cloth; the conductive substrate is successively cleaned or ultrasonically washed with hydrochloric acid, acetone, and ethanol before being added to the uniform solution.

[0006] Furthermore, the molar ratio of the cobalt salt, nickel salt, and urea is 2:1 - 3:4 - 6.

[0007] Furthermore, the temperature of the hydrothermal reaction is 115 - 125 °C, and the time is 5 - 12 h; the temperature of the calcination is 200 - 600 °C, and the time is 11 - 13 h; the temperature of the hydrothermal treatment is 60 - 180 °C, and the time is 1.5 - 8.5 h.

[0008] Furthermore, the temperature of the hydrothermal reaction is 120 °C, and the time is 6 h.

[0009] Furthermore, the nickel salt solution is an aqueous solution containing nickel salt and dimethylimidazole, the concentration of the nickel salt is 3 - 4 mol / L, and the concentration of the dimethylimidazole is 2 - 3 mol / L.

[0010] This application also provides a NiCo2O4@Ni(OH)2 electrocatalytic material prepared by the above method. The NiCo2O4@Ni(OH)2 electrocatalytic material is supported by a conductive substrate. The inside of the core - shell structure is NiCo2O4 nanowires, and the outside is Ni(OH)2 ultrathin nanosheets.

[0011] Preferably, the NiCo2O4@Ni(OH)2 electrocatalytic material is applied to the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid.

[0012] More preferably, the application of the NiCo2O4@Ni(OH)2 electrocatalytic material to the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid is specifically as follows: The NiCo2O4@Ni(OH)2 electrocatalytic material is used as the working electrode, a carbon rod is used as the counter electrode, and a 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.

[0013] Finally, the electrolyte solution also contains cyclopentanone, and the concentration of the cyclopentanone is 0.1 M.

[0014] Beneficial effects: First, NiCo2O4 nanowire arrays are obtained by the hydrothermal method and the calcination method; further, nickel hydroxide is grown by hydrothermal treatment to in - situ construct a NiCo2O4@Ni(OH)2 core - shell structure; due to the PN - junction interface electron rearrangement and the core - shell structure, the NiCo2O4@Ni(OH)2 electrocatalytic material has excellent performance in the electro - oxidation of cyclopentanone to prepare glutaric acid; The NiCo2O4@Ni(OH)2 heterojunction composed of the core - shell structure, with NiCo2O4 nanowires inside and Ni(OH)2 ultrathin nanosheets outside, provides more active sites and better mass transfer ability. Moreover, a unique PN - junction built - in electric field is formed between the NiCo2O4 nanowires and the Ni(OH)2 nanosheets, reducing the thermodynamic energy barrier for the generation of the high - valence NiOOH active substance and greatly improving the activity of the oxidation of cyclopentanone to glutaric acid.

[0015] Benefiting from the strong electronic interaction between the core-shell structure and the heterointerfaces, the NiCo2O4@Ni(OH)2 electrocatalytic material exhibits excellent cyclopentanone oxidation performance at industrial currents, and the overpotential is significantly reduced compared to the single-component Ni(OH)2. The results of nuclear magnetic resonance spectra and infrared spectra indicate that cyclopentanone is efficiently oxidized to glutaric acid. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some preferred embodiments of the present application, rather than all embodiments. For the preferred embodiments of the present application, those of ordinary skill in the art can obtain other embodiments and drawings based on these embodiments and drawings without creative efforts, all of which fall within the protection scope of the present application.

[0017] Figure 1 SEM image of nickel foam for growing Ni(OH)2 nanosheets in the embodiments of the present application; Figure 2 SEM image of nickel foam for growing NiCo2O4 nanowires in the embodiments of the present application; Figure 3 SEM image of the NiCo2O4@Ni(OH)2 electrocatalytic material in the embodiments of the present application; Figure 4 XRD patterns of Ni(OH)2 nanosheets, NiCo2O4 nanowires and NiCo2O4@Ni(OH)2 core-shell structure in the embodiments of the present application; Figure 5 Polarization curves of Ni(OH)2, NiCo2O4 and NiCo2O4@Ni(OH)2 electrocatalytic materials prepared in the embodiments of the present application during electrocatalytic oxygen evolution and cyclopentanone oxidation processes; Figure 6 I-t (a) curve, nuclear magnetic resonance spectrum (b), and infrared spectrum (c) of the NiCo2O4@Ni(OH)2 electrocatalytic material prepared in the embodiments of the present application during the electrocatalytic cyclopentanone oxidation process. Detailed Embodiments

[0018] To make the objectives, technical solutions and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail. It should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. The above definitions are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the structures referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0019] Example 1 A preparation method of NiCo2O4@Ni(OH)2 electrocatalytic material, the preparation steps are as follows: (1) Cut a 2 cm × 4 cm nickel foam conductive substrate, and then ultrasonically clean it with hydrochloric acid, acetone, and ethanol for 10 minutes each, and finally store it in ethanol solvent for later use; Dissolve 0.29 g (1 mmol) nickel nitrate hexahydrate, 0.581 g (2 mmol) cobalt nitrate hexahydrate, and 0.6 g (10 mmol) urea in 40 mL of deionized water, stir for 20 minutes to obtain a homogeneous solution; transfer the homogeneous solution to a 50 mL reaction kettle with a polytetrafluoroethylene liner, and place the cleaned nickel foam in the reaction kettle, and carry out a hydrothermal reaction at 120 °C for 6 hours, and naturally cool to obtain a NiCo-OH precursor uniformly grown on the nickel foam; (2) Place the nickel foam growing the NiCo-OH precursor in a magnetic boat, and heat-treat it at 450 °C for 2 h in an air atmosphere to obtain nickel foam growing NiCo2O4 nanowires; (3) Prepare 35 mL of a nickel salt aqueous solution containing 0.125 mmol nickel nitrate and 0.1 mmol dimethylimidazole, put the nickel foam growing the NiCo2O4 nanowire array into the nickel salt aqueous solution, then place it in a 50 mL reaction kettle with a polytetrafluoroethylene liner, and carry out a hydrothermal reaction at 180 °C for 6 hours, and naturally cool to obtain the NiCo2O4@Ni(OH)2 core-shell structure electrocatalytic material.

[0020] As Figure 2 shown, nanoneedle-shaped NiCo2O4 grows uniformly on the nickel foam; As Figure 3 shown, a NiCo2O4@Ni(OH)2 core-shell structure is formed after secondary hydrothermal treatment; As Figure 4 shown, the XRD pattern shows the successful preparation of Ni(OH)2, NiCo2O4 and NiCo@Ni(OH)2 nanostructures.

[0021] Comparative Example 1 Cut a 2 cm × 4 cm nickel foam conductive substrate, and then ultrasonically clean it with hydrochloric acid, acetone, and ethanol for 10 minutes each, and finally store it in ethanol solvent for later use; Prepare 35 mL of a nickel salt aqueous solution containing 0.125 mmol nickel nitrate and 0.1 mmol dimethylimidazole, put the nickel foam into the nickel salt aqueous solution, then place it in a 50 mL reaction kettle with a polytetrafluoroethylene liner, and carry out a hydrothermal reaction at 180 °C for 6 hours, and naturally cool to obtain Ni(OH)2 nanosheets as shown in Figure 1 shown, uniformly distributed on the nickel foam.

[0022] Comparative Example 2 Using a three - electrode electrolytic cell device, 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 1M KOH solution as the electrolyte solution, electrocatalytic oxidation tests were carried out at room temperature. The obtained results are as Figure 5 shown in (a). Compared with the single - component Ni(OH)2 and NiCo2O4, the NiCo2O4@Ni(OH)2 core - shell structure has a larger oxidation peak, indicating that it is easier to form high - valence NiOOH active substances on its surface.

[0023] Example 2 On the basis of Comparative Example 2, the concentration of KOH in the electrolyte solution is 1M, the concentration of cyclopentanone is 0.1M, and the others are the same as in Comparative Example 2. The obtained results are as Figure 5 shown in (b). It can be seen that after adding cyclopentanone, the oxidation current density increased significantly, indicating the progress of the cyclopentanone oxidation reaction. It is worth noting that NiCo2O@Ni(OH)2 still shows better cyclopentanone oxidation performance than the single - component, and can drive an industrial - grade current density of about 450 mA / cm² at a voltage of 1.6V. -2

[0024] Example 3 Using a three - electrode electrolytic cell device, with 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, the concentration of KOH in the electrolyte solution is 1M, and the concentration of cyclopentanone is 0.1M. I - t tests were carried out at room temperature, and the results are as Figure 6 shown in (a), and nuclear magnetic resonance and infrared spectroscopy were used to analyze the products after electrolysis. The results are as Figure 6 shown in (b) and Figure 6 shown in (c). The results show that the NiCo2O4@Ni(OH)2 core - shell structure can stably oxidize cyclopentanone to glutaric acid.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limitations. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present application, and they should all be covered within the scope of the claims of the present application.​

Claims

1. A preparation method of 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 evenly to obtain a homogeneous solution, place the conductive substrate in the homogeneous solution, carry out hydrothermal reaction, and naturally cool to obtain the conductive substrate with NiCo-OH precursor grown; (2) Carry out calcination treatment on the conductive substrate with NiCo-OH precursor grown to obtain the conductive substrate with NiCo2O4 nanowire array grown; (3) Place the conductive substrate with NiCo2O4 nanowire array grown in nickel salt solution for hydrothermal treatment to obtain the NiCo2O4@Ni(OH)2 electrocatalytic material with core-shell structure.

2. The preparation method of a 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; before adding the conductive substrate into the homogeneous solution, it is successively cleaned or ultrasonically cleaned with hydrochloric acid, acetone and ethanol.

3. The preparation method of a NiCo2O4@Ni(OH)2 electrocatalytic material according to 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 a NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 1, characterized in that, The temperature of the hydrothermal reaction is 115~125°C, and the time is 5~12h; the temperature of the calcination is 200~600°C, and the time is 11~13h; the temperature of the hydrothermal treatment is 60~180°C, and the time is 1.5~8.5h.

5. The preparation method of a NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 1, characterized in that, The temperature of the hydrothermal reaction is 120°C, and the time is 6h.

6. The preparation method of a NiCo2O4@Ni(OH)2 electrocatalytic material according to claim 1, characterized in that, The nickel salt solution is an aqueous solution containing nickel salt and dimethylimidazole, the concentration of the nickel salt is 3 - 4mol / L, and the concentration of the dimethylimidazole is 2 - 3mol / L.

7. The NiCo2O4@Ni(OH)2 electrocatalytic material prepared by the method according to any one of claims 1-6, characterized in that, The NiCo2O4@Ni(OH)2 electrocatalytic material is supported by the conductive substrate, the inside of the core-shell structure is NiCo2O4 nanowires, and the outside is Ni(OH)2 ultrathin nanosheets.

8. Application of the NiCo2O4@Ni(OH)2 electrocatalytic material according to claim 7 in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid.

9. Use of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 8 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. The electrocatalytic oxidation is carried out at room temperature, and the electrolyte solution is 1M KOH solution.

10. The application of the NiCo2O4@Ni(OH)2 electrocatalytic material as described in claim 9 in the electrocatalytic oxidation of cyclopentanone to prepare glutaric acid, characterized in that, The electrolyte solution also contains cyclopentanone, and the concentration of the cyclopentanone is 0.1M.

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