Preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates

Abstract

The present invention discloses a preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates, belonging to the technical field of electrocatalytic biomass conversion. The preparation method includes: S1: Mix nitrate and urea evenly in an ethanol aqueous solution, and gradually decompose urea during the hydrothermal reaction process to form isocyanic acid and ammonia; the nitrate reacts with the CO2 released by isocyanic acid to form basic carbonate M(OH)2CO3 nanoplates; S2: Calcinate the basic carbonate M(OH)2CO3 nanoplates in air to form high-entropy oxide (CoMnNiZnCu)3O4 nanoplates; wherein, at high temperature, small molecules of CO2 and H2O overflow from the basic carbonate M(OH)2CO3 nanoplates to form mesopores, so as to achieve the purpose that this catalyst shows good activity and stability in the three-electrode system for electrocatalytic oxidation of HMF to FDCA.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic biomass conversion, and more particularly, relates to a method for preparing mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates. Background Art

[0002] The extensive consumption of fossil fuels and the increasingly severe environmental problems have forced people to seek more sustainable energy resources. The growing concerns about the rapid depletion of fossil fuels and carbon emissions are the main motivations for exploring renewable resources and pursuing sustainable technologies. Lignocellulosic biomass is an inedible carbon resource widely existing in the world, which can be converted into renewable energy and high-value chemicals, and biomass-based chemicals can replace most petrochemical products.

[0003] Biomass is an abundant and sustainable resource formed by photosynthesis, which makes it a unique raw material and clean energy source, and can achieve the grand goal of a fossil-fuel-free future. Developing high-value-added products from biomass has great economic potential and social benefits. 5-Hydroxymethylfurfural (HMF), as one of the most important renewable platform chemicals, is formed by the dehydration of hexose-based biomass such as fructose and glucose. Its functional groups, such as aldehyde group (–CHO), hydroxyl group (–OH) and furan ring endow HMF with multifunctionality, so it is considered as a key bridge connecting biomass resources and future energy. Specifically, it can be converted into commercial chemicals for industry, agriculture and medicine through a series of reactions such as hydrolysis, polymerization, hydrogenation and redox. In addition, high-quality bio-based platform chemicals, such as: 5-hydroxymethyl-2-furoic acid (HMFCA), 2,5-diformylfuran (DFF), 5-formyl-2-furoic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA), used as precursors or intermediates in chemical synthesis, polymer production and drug production, can be prepared by catalytic oxidation of different positions and degrees of aldehyde groups and hydroxyl groups of HMF. It is worth noting that one of the most promising derivatives is FDCA, which is an important aromatic monomer with a planar and rigid ring structure, and is used to produce bio-based polymers such as polyamides, polyesters and polyclones.

[0004] In view of the broad prospects and significant impact of FDCA in the production of bio-based polymers, how to obtain high-value-added FDCA through HMF has attracted much attention in recent years. However, HMF has multiple functional groups, and multiple side reactions are prone to occur during the conversion process, thus affecting the quality of the chemical products. Therefore, the key to achieving the high value of HMF is to design and prepare efficient and green catalytic systems by selectively breaking / functionalizing specific functional groups of HMF to convert HMF into a variety of high-value-added chemicals, liquid fuels and additives. Related work on the production of FDCA using thermochemical catalysis has long been reported. However, this method requires high temperature (>100℃) and high O2 pressure (0.3–2.0MPa), and the yield of the final product FDCA is insufficient. Compared with traditional thermal catalytic oxidation, the preparation of FDCA by electrocatalytic HMF oxidation reaction (HMFOR) has been proposed due to its inherent high efficiency and clean characteristics, and has been developed as a new organic synthesis technology to date. Specifically, first, electrocatalytic oxidation can achieve efficient conversion of HMF under ambient conditions (normal temperature and pressure) by electric drive; second, HMF electrooxidation can be carried out with water as the oxygen source, without the need to add oxidants or organic solvents to initiate the reaction. Most importantly, the yield, conversion rate and Faradaic efficiency of FDCA can be easily achieved by adjusting the pH value of the electrolyte, the design and construction of the catalyst, and the adjustment of the solution parameters. Finally, the scientifically favorable HMF oxidation can also be coupled with different reduction reactions, which not only enriches the value-added products, but also greatly improves the energy efficiency.

[0005] Based on this, constructing a stable and efficient catalyst for the continuous and efficient oxidation of HMF to FDCA is crucial for the transformation of the energy structure and is also a scientific problem that needs to be solved urgently. Summary of the invention

[0006] In view of this, in order to solve the above-mentioned problems existing in the prior art, the object of the present invention is to provide a method for preparing mesoporous high entropy oxide (CoMnNiZnCu)3O4 nanoplates so as to achieve the purpose of exhibiting good activity and stability for the electrocatalytic oxidation of HMF to FDCA in a three-electrode system.

[0007] The technical solution adopted by the present invention is: a method for preparing a mesoporous high entropy oxide (CoMnNiZnCu)3O4 nanoplate, the preparation method comprising:

[0008] S1: Evenly mix nitrate and urea in an ethanol aqueous solution, and gradually decompose urea to form isocyanic acid and ammonia during the hydrothermal reaction; CO2 released by nitrate and isocyanic acid reacts to form basic carbonate M(OH)2CO3 nanoplates;

[0009] S2: Calcinate the basic carbonate M(OH)2CO3 nanoplates in air to form high-entropy oxide (CoMnNiZnCu)3O4 nanoplates;

[0010] Among them, at high temperature, the basic carbonate M(OH)2CO3 nanoplates form mesopores through the overflow of small molecules of CO2 and H2O.

[0011] Furthermore, the nitrate includes cobalt nitrate, copper nitrate, manganese nitrate, zinc nitrate and nickel nitrate. Among them, the molar fractions of cobalt nitrate, copper nitrate, manganese nitrate, zinc nitrate and nickel nitrate are respectively: 0.65 - 0.75 parts, 0.2 - 0.25 parts, 0.4 - 0.45 parts, 0.2 - 0.25 parts and 0.3 - 0.35 parts.

[0012] Furthermore, the molar ratio of cobalt nitrate, copper nitrate, manganese nitrate, zinc nitrate and nickel nitrate in the nitrate is:

[0013] Cobalt nitrate: Copper nitrate: Manganese nitrate: Zinc nitrate: Nickel nitrate = 1:0.30:0.58:0.35:0.5.

[0014] Furthermore, in the above S1, the method for preparing the basic carbonate M(OH)2CO3 nanoplates is as follows:

[0015] S101: Dissolve urea in an ethanol aqueous solution, and add oleic acid and stir evenly to obtain a first mixed solution; among them, dissolve urea in the aqueous solution according to the ratio that the volume of water added for 1 mmol of urea is 1 - 2 ml, and then add ethanol and stir evenly.

[0016] S102: Dissolve nitrate in water according to a ratio, add the above first mixed solution and stir evenly to obtain a second mixed solution; among them, dissolve nitrate in water according to the ratio that the volume of water added for 1 mmol of nitrate is 2 - 5 ml.

[0017] S103: Subject the second mixed solution to a hydrothermal reaction;

[0018] S104: After the hydrothermal reaction, cool to room temperature, wash successively with n-hexane, ethanol and water, and dry to form basic carbonate M(OH)2CO3 nanoplates.

[0019] Furthermore, in S101, the volume fractions of the oleic acid, ethanol and water are: 4 - 5 parts, 12 - 15 parts and 8 - 10 parts.

[0020] Furthermore, the volumes of the oleic acid, ethanol and water are respectively 5 mL, 15 mL and 10 mL.

[0021] Furthermore, the hydrothermal reaction is carried out at a temperature of 160 - 170 °C for 8 - 12 h.

[0022] Furthermore, in the above S2, the method for preparing mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is as follows:

[0023] S201: Place the basic carbonate M(OH)2CO3 nanoplates in a tubular furnace;

[0024] S202: Prepare mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates by programmed temperature calcination in an air stream.

[0025] Furthermore, the programmed temperature process is as follows: Calcinate at 300 - 400 °C for 2 - 4 h, with a heating rate of 1 - 3 °C / min, and cool the temperature to room temperature to obtain mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates.

[0026] Furthermore, the programmed temperature process is as follows: Calcinate at 300 °C for 3 h, with a heating rate of 2 °C / min.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention uses highly crystalline basic carbonate (i.e., M(OH)2CO3 nanoplates) as a precursor, which is converted into high-entropy metal oxide through calcination in an air atmosphere. During the heating process, small molecules will generate mesoporous pores with a size range of 3 - 8 nm in the metal oxide. At the same time, due to the relatively low thermal decomposition temperature of most basic carbonates, removing non-metallic components effectively avoids excessive grain growth and pore collapse, while maintaining the high crystallinity of the oxide.

[0029] 2. The preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention shows excellent electrocatalytic activity and selectivity. The mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates prepared can achieve 95% FDCA selectivity at different voltages, and the Faraday efficiency can be maintained above 98%. After 6 cyclic tests, the selectivity and Faraday efficiency hardly change, confirming the good stability of the high-entropy oxide material. At the same time, this preparation method is simple, fast, environmentally friendly, and suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the XRD pattern of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates prepared by the preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention in Example 1;

[0031] Figure 2SEM image of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates prepared by the preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention in Example 1;

[0032] Figure 3 TEM image of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates prepared by the preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention in Example 1;

[0033] Figure 4 Conversion rate and selectivity of HMF oxidation to FDCA at different voltages in 1M KOH aqueous solution with basic carbonate M(OH)2CO3 nanoplates as catalysts by the preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention in Example 1;

[0034] Figure 5 Conversion rate and Faraday efficiency after 6 cyclic tests at 1.485V (vs RHE) by the preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates provided by the present invention in Example 1. Detailed implementation mode

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Example 1

[0037] A preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is provided in this example. The preparation method includes:

[0038] S1: Prepare basic carbonate M(OH)2CO3 nanoplates, and the method is as follows:

[0039] S101: Dissolve 8.6 mmol of urea in 10 ml of aqueous solution, then add 15 ml of ethanol and stir for 10 minutes; add 5 mL of oleic acid and stir again for 30 minutes to obtain a primary mixed solution;

[0040] S102: Prepare nitrates in the ratio of 0.7 mmol of cobalt nitrate, 0.21 mmol of copper nitrate, 0.40 mmol of manganese nitrate, 0.20 mmol of zinc nitrate, and 0.35 mmol of nickel nitrate, dissolve them in 8 mL of water, add the above-mentioned primary mixed solution, and stir for 1 hour until evenly mixed to obtain a secondary mixed solution;

[0041] S103: Transfer the secondary mixed solution to a high-pressure hydrothermal reactor for hydrothermal reaction. The reaction temperature condition is 170 °C and the reaction time is 9 hours;

[0042] S104: After the hydrothermal reaction, cool to room temperature, wash three times successively with n-hexane, ethanol, and water, and dry in a vacuum drying oven to form basic carbonate M(OH)2CO3 nanoplates.

[0043] S2: Calcinate the basic carbonate M(OH)2CO3 nanoplates in air to form high-entropy oxide (CoMnNiZnCu)3O4; The method for preparing mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is as follows:

[0044] S201: Place the powdered basic carbonate M(OH)2CO3 nanoplates in a tube furnace;

[0045] S202: Since mesopores will be formed when small molecules of CO2 and H2O overflow from the basic carbonate M(OH)2CO3 nanoplates at high temperature, therefore, mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates can be obtained by programmed temperature calcination in an air stream. Among them, the process of programmed temperature rise is: calcine at 300 °C for 3 h, and the heating rate is 2 °C / min. After the temperature drops to room temperature, mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates are obtained. The proportion of metal elements in the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is as follows:

[0046]

[0047]

[0048] It can be confirmed from the above table that it is a high-entropy oxide.

[0049] From Figure 1 The X-ray diffraction pattern (XRD) shows that the crystal structure of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates exists in the crystal form of spinel Co3O4 and no phase separation occurs;

[0050] From Figure 2As can be seen from the scanning electron microscope image (SEM), the prepared mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates have a uniform morphology, with a length of about 3 μm and a width of about 500 nm;

[0051] From Figure 3 As can be seen from the transmission electron microscope image (TEM), a large number of mesoporous channels are distributed on the surface of the prepared mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates, confirming its mesoporous structure.

[0052] Example 2

[0053] In this example, a method for preparing mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is provided, and the preparation method includes:

[0054] S1: Prepare basic carbonate M(OH)2CO3 nanoplates, and the method is as follows:

[0055] S101: Dissolve 6 mmol of urea in 8 ml of aqueous solution, then add 12 ml of ethanol and stir for 8 minutes; add 4 mL of oleic acid and stir again for 20 minutes to obtain a primary mixed solution;

[0056] S102: Prepare nitrates according to the ratio of 0.65 mmol of cobalt nitrate, 0.2 mmol of copper nitrate, 0.4 mmol of manganese nitrate, 0.20 mmol of zinc nitrate: 0.3 mmol of nickel nitrate and dissolve them in 6 mL of water. After adding the above primary mixed solution, stir for 50 minutes until evenly mixed to obtain a secondary mixed solution;

[0057] S103: Transfer the secondary mixed solution to a high-pressure hydrothermal reaction kettle for hydrothermal reaction, with the reaction temperature condition of 160 °C and the reaction time of 8 hours;

[0058] S104: After the hydrothermal reaction, cool to room temperature, wash three times with n-hexane, ethanol and water in sequence, and dry in a vacuum drying oven to form basic carbonate M(OH)2CO3 nanoplates.

[0059] S2: Calcinate the basic carbonate M(OH)2CO3 nanoplates in air to form high-entropy oxide (CoMnNiZnCu)3O4; the method for preparing mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is:

[0060] S201: Place the powdered basic carbonate M(OH)2CO3 nanoplates in a tube furnace;

[0061] S202: Since the mesopores will be formed when the basic carbonate M(OH)2CO3 nanoplates release small molecules of CO2 and H2O at high temperature, the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates can be obtained by programmed temperature calcination in an air stream. Among them, the process of programmed temperature rise is as follows: calcine at 300 °C for 2 h, and the heating rate is 1.5 °C / min. After the temperature drops to room temperature, the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates are obtained.

[0062] Example 3

[0063] In this example, a preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is provided. The preparation method includes:

[0064] S1: Prepare basic carbonate M(OH)2CO3 nanoplates, and the method is as follows:

[0065] S101: Dissolve 7.5 mmol of urea in 9 ml of aqueous solution, then add 13.5 ml of ethanol and stir for 9 minutes; after adding 4.5 mL of oleic acid, stir for another 25 minutes to obtain a primary mixed solution;

[0066] S102: Prepare nitrates according to the ratio of 0.7 mmol of cobalt nitrate, 0.23 mmol of copper nitrate, 0.42 mmol of manganese nitrate, 0.23 mmol of zinc nitrate: 0.32 mmol of nickel nitrate and dissolve them in 7 mL of water. After adding the above primary mixed solution, stir for 55 minutes until evenly stirred to obtain a secondary mixed solution;

[0067] S103: Transfer the secondary mixed solution to a high-pressure hydrothermal reaction kettle for hydrothermal reaction. The reaction temperature condition is 165 °C and the reaction time is 10 hours;

[0068] S104: After the hydrothermal reaction, cool to room temperature, wash three times with n-hexane, ethanol and water in sequence, and dry in a vacuum drying oven to form basic carbonate M(OH)2CO3 nanoplates.

[0069] S2: Calcinate the basic carbonate M(OH)2CO3 nanoplates in air to form high-entropy oxide (CoMnNiZnCu)3O4; the method for preparing mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates is:

[0070] S201: Place the powdered basic carbonate M(OH)2CO3 nanoplates in a tubular furnace;

[0071] S202: Since the mesopores will be formed by the spillage of small molecules of CO2 and H2O from the basic carbonate M(OH)2CO3 nanoplates at high temperatures, mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates can be obtained by programmed temperature calcination in an air stream. Among them, the process of programmed temperature increase is as follows: calcine at 350 °C for 3 h, and the heating rate is 2 °C / min. After the temperature drops to room temperature, mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates are obtained.

[0072] For the beneficial effects of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates prepared in the above-mentioned various embodiments, the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates prepared in Example 1 were used as a catalyst and drop-coated on a working electrode (a carbon paper with an area of 1 cm -2 ), a reference electrode Hg / HgO, and a counter electrode Pt sheet to form a three-electrode system. The oxidation performance of HMF was tested by I-T test in a solution with a pH of 14 containing 10 mM HMF. The results are shown in Figure 4 .

[0073] It can be seen from Figure 4 that after collecting a charge of 59 C (the charge required for the complete conversion of 10 mL of 10 mM HMF to FDCA) at voltages of 1.385 V, 1.435 V, and 1.485 V (vs RHE), a conversion rate of more than 98% can be achieved, and the selectivity of the product to FDCA is as high as 95%. As the voltage increases, the side reaction of oxygen evolution reaction occurs, resulting in a decrease in the conversion rate.

[0074] Six cyclic tests were carried out at a voltage of 1.485 V through the above three-electrode system. The results are shown in Figure 5 . As shown in Figure 5 , after 6 cycles, the conversion rate and selectivity did not change, confirming its excellent catalytic stability. The above confirms that the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates have great potential commercial value in the electrocatalytic oxidation of HMF to synthesize FDCA.

[0075] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A preparation method of mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanoplates, characterized in that, The preparation method includes: S1: Mix nitrate and urea evenly in an ethanol aqueous solution, and gradually decompose urea during the hydrothermal reaction process to form isocyanic acid and ammonia; the nitrate reacts with the CO2 released by isocyanic acid to form basic carbonate M(OH)2CO3 nanoplates; the method for preparing basic carbonate M(OH)2CO3 nanoplates is as follows: S101: Dissolve urea in an ethanol aqueous solution, add oleic acid and stir evenly to obtain a primary mixed solution; the volume fractions of oleic acid, ethanol and water are: 4 - 5 parts, 12 - 15 parts and 8 - 10 parts; S102: Dissolve nitrate in water according to a ratio, add the above primary mixed solution and stir evenly to obtain a secondary mixed solution; S103: Carry out hydrothermal reaction on the secondary mixed solution; S104: After the hydrothermal reaction, cool to room temperature, wash successively with n - hexane, ethanol and water, and form basic carbonate M(OH)2CO3 nanoplates after drying; S2: Calcinate the basic carbonate M(OH)2CO3 nanoplates in air to form high - entropy oxide (CoMnNiZnCu)3O4 nanoplates; Among them, at high temperature, small molecules of CO2 and H2O overflow from the basic carbonate M(OH)2CO3 nanoplates to form mesopores.

2. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 1, characterized in that, The nitrate includes cobalt nitrate, copper nitrate, manganese nitrate, zinc nitrate and nickel nitrate, and the molar fractions of cobalt nitrate, copper nitrate, manganese nitrate, zinc nitrate and nickel nitrate are respectively: 0.65 - 0.75 parts, 0.2 - 0.25 parts, 0.4 - 0.45 parts, 0.2 - 0.25 parts and 0.3 - 0.35 parts.

3. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 2, characterized in that, The molar ratio of cobalt nitrate, copper nitrate, manganese nitrate, zinc nitrate and nickel nitrate in the nitrate is: Cobalt nitrate: Copper nitrate: Manganese nitrate: Zinc nitrate: Nickel nitrate = 1:0.30:0.58:0.35:0.

5.

4. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 1, wherein, The volumes of oleic acid, ethanol and water are 5 mL, 15 mL and 10 mL respectively.

5. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 160 - 170 °C for 8 - 12 h.

6. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 1, characterized in that, In the above S2, the method for preparing mesoporous high - entropy oxide (CoMnNiZnCu)3O4 nanoplates is: S201: Place the basic carbonate M(OH)2CO3 nanoplates in a tubular furnace; S202: Prepare and obtain mesoporous high - entropy oxide (CoMnNiZnCu)3O4 nanoplates by programmed - temperature calcination in an air stream.

7. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 6, characterized in that, The programmed - temperature process is: Calcinate at 300 - 400 °C for 2 - 4 h, and the heating rate is 1 - 3 °C / min. After the temperature drops to room temperature, mesoporous high - entropy oxide (CoMnNiZnCu)3O4 nanoplates are obtained.

8. The preparation method of the mesoporous high-entropy oxide (CoMnNiZnCu)3O4 nanosheets according to claim 7, characterized in that, The programmed - temperature process is: Calcinate at 300 °C for 3 h, and the heating rate is 2 °C / min.

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