Manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material, preparation method and application thereof

Abstract

The application provides a manganese-doped cobalt iron oxide nanoparticle@carbon-nitrogen cube composite material and a preparation method and application thereof. The preparation method is as follows: firstly, ferrous sulfate and manganese chloride are doped into ZIF-8; secondly, the doped ZIF-8 is mixed with cobalt nitrate and 2-methyl imidazole in methanol; thirdly, the product is obtained through centrifugal separation; finally, carbon-nitrogen of the composite material is realized through one-step calcination, manganese doping, cobalt iron oxide nanoparticle generation, and finally, the manganese-doped cobalt iron oxide nanoparticle@carbon-nitrogen cube composite material is obtained. Compared with a traditional preparation method, the method is simple, the reaction condition is mild, the yield is high, and the prepared composite material has a uniform morphology and excellent electrocatalytic performance for an electrolytic water oxygen evolution reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of carbon-coated nanoparticle composites, in particular to a manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material and a preparation method and application thereof. BACKGROUND

[0002] Currently, water electrolysis hydrogen production technology is considered as a hot path for green hydrogen production due to its environmental friendliness, high product purity and other characteristics. Among them, the anode oxygen evolution reaction (OER) as the rate-determining step of the water electrolysis process, its slow kinetics and high overpotential lead to a significant reduction in energy conversion efficiency. Although noble metal-based catalysts (such as IrO2, RuO2) exhibit excellent OER activity, their scarcity and high cost make it difficult to meet the demand of large-scale application. In recent years, transition metal-based catalysts (such as Fe, Co, Mn-based materials) have attracted widespread attention due to their abundant resources, low cost and other advantages, but their catalytic activity and stability still have a significant gap with noble metal materials.

[0003] Carbon nanomaterials (such as graphene, carbon nanotubes, porous carbon, etc.) are often used as carriers for transition metal-based electrocatalysts due to their excellent electrical conductivity, high specific surface area and adjustable electronic structure, and show good application prospects in water electrolysis hydrogen production. Studies have shown that by combining transition metals (such as Co, Fe, Mn, etc.) with carbon materials, the hydrogen evolution (HER) and oxygen evolution (OER) activities of the catalysts can be significantly improved. Li shunli et al. successfully synthesized a hollow nanostructured Mo / Fe / Co@NC catalyst based on ZIFs by using phosphomolybdic acid and potassium ferricyanide as strong and weak chelating agents and high-temperature calcination, which exhibited excellent oxygen evolution and oxygen reduction performance. Li zhongxian et al. synthesized CoFe, NiFe, and CuFe Prussian blue analogues (PBAs) by a co-precipitation method, and prepared CoP-FeP / NC, Ni2P-FeP / NC, and Cu3P-FeP / NC electrocatalysts with hollow nanocubic structures by template-assisted and phosphidation annealing strategies, among which CoP-FeP / NC exhibited excellent oxygen evolution reaction (OER) performance. These carbon-transition metal materials have excellent water electrolysis oxygen evolution performance, but the preparation method is complicated and the cost is high, which is not convenient for popularization and application. SUMMARY

[0004] The purpose of the present application is to provide a manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material and a preparation method and application thereof, in order to solve the problem of complicated preparation method and high preparation cost of the existing transition metal-carbon composite material for oxygen evolution reaction.

[0005] The present application is implemented as follows:

[0006] A preparation method of a manganese-doped cobalt iron oxide nanoparticle@carbon-nitrogen cube composite material, comprising the following steps:

[0007] (1) Dissolve iron salt, manganese salt and zinc salt in methanol to obtain a methanol solution containing iron, manganese and zinc; dissolve 2-methyl imidazole in methanol to obtain a methanol solution of 2-methyl imidazole;

[0008] (2) Mix the two methanol solutions in step (1), and fully stir to obtain a product, which is subjected to centrifugal separation, washing and drying to obtain a FeMn-ZIF-8@ZIF-67 composite precursor;

[0009] (3) Dissolve the FeMn-ZIF-8@ZIF-67 composite precursor obtained in step (2) and cobalt salt in methanol to obtain a methanol solution containing cobalt; dissolve 2-methyl imidazole in methanol to obtain a methanol solution of 2-methyl imidazole;

[0010] (4) Mix the two methanol solutions in step (3), and fully stir to obtain a product, which is subjected to centrifugal separation, washing and drying to obtain a precursor powder;

[0011] (5) Calcine the precursor powder obtained in step (4) under an inert atmosphere at 900-930 DEG C for 2-5 h to obtain a manganese-doped cobalt iron oxide nanoparticle@carbon-nitrogen cube composite material.

[0012] The present application realizes the structure construction of the Mn-precise doped CoFe oxide nanoparticle uniformly anchored in the conductive carbon-nitrogen cube skeleton through the double-MOF epitaxial growth + one-step calcination multi-effect synthesis, not only simplifies the preparation process and reduces the cost, but also significantly improves the OER activity and stability.

[0013] Preferably, the iron salt in step (1) is ferrous sulfate heptahydrate, the manganese salt is manganese chloride tetrahydrate, and the zinc salt is zinc nitrate hexahydrate.

[0014] Preferably, the methanol used in step (1) and step (3) is anhydrous methanol.

[0015] Preferably, the stirring speed in step (2) and step (4) is 350 rpm.

[0016] Preferably, in step (5), the inert atmosphere is a nitrogen atmosphere, and the temperature is raised to 900-930 DEG C at a heating rate of 5 DEG C / min under the nitrogen atmosphere from room temperature.

[0017] The application also provides a method for applying the manganese-doped cobalt iron oxide nanoparticle@carbon nitride cubic composite material prepared according to the above method, dispersing the manganese-doped cobalt iron oxide nanoparticle@carbon nitride cubic composite material into a dispersant to obtain a dispersion liquid, and dropping the dispersion liquid on the surface of a glassy carbon electrode and drying to obtain a catalyst for an oxygen evolution reaction, wherein the dispersant is a naphthol solution.

[0018] The application first encapsulates manganese and iron in a ZIF-8 precursor, then introduces cobalt by epitaxial growth of ZIF-67 to obtain a FeMn-ZIF-8@ZIF-67 composite precursor, and finally removes zinc ions, dopes manganese and generates CoFe oxide nanoparticles by one-step calcination, and the outward volatilization of zinc promotes the adhesion of nanoparticles on the surface of the material, enhances the structural stability, and finally obtains the manganese-doped cobalt iron oxide nanoparticle@carbon nitride cubic composite material.

[0019] The Mn in the composite material is not simply mixed, but is co-embedded with Fe in the synthesis of ZIF-8, and then Co is introduced by epitaxy, realizing uniform doping at the atomic level and not aggregating, effectively regulating the electronic structure of Co / Fe, optimizing the adsorption energy of active sites and reducing the OER reaction energy barrier. At the same time, the volatilization characteristics of Zn in ZIF-8 at high temperature are utilized to make metal oxide nanoparticles naturally migrate and adhere to the surface of the carbon nitride skeleton, improving the exposure degree and stability of the catalytic site. One-step calcination makes four effects of Zn volatilization to remove the template, Mn doping in-situ into the CoFe oxide lattice, CoFe oxide nanoparticle generation and organic ligand carbonitridation to form a conductive carbon nitride skeleton.

[0020] The synthesis method of the composite material of the application is simple, low in cost, high in yield and mild in reaction. The manganese-doped cobalt iron oxide nanoparticle@carbon nitride cubic composite material prepared by the method of the application has a uniform morphology, realizes the coexistence of manganese doping and nanoparticles in the carbon nitride cubic skeleton with high conductivity, and this structure not only ensures the high activity of metal oxides, but also utilizes the carbon nitride skeleton to provide an electronic fast transmission channel, significantly improving the OER kinetics.

[0021] The composite material of the application has excellent electrocatalytic performance for the water electrolysis oxygen evolution reaction, has a lower initial potential, a higher current density and a smaller Tafel slope, and as a catalyst, provides a new choice for the research in the fields of energy storage, conversion, fuel cells and the like. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a preparation method flow chart of the manganese-doped cobalt iron oxide nanoparticle@carbon nitride cubic composite material of the application.

[0023] Figure 2are scanning electron microscope images of the material prepared in Example 1 of the present application; wherein A is a scanning electron microscope image of the FeMn-ZIF-8@ZIF-67 composite precursor, and B is a scanning electron microscope image of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material.

[0024] Figure 3 are transmission electron microscope images of the material prepared in Example 1 of the present application; wherein A is a transmission electron microscope image of the FeMn-ZIF-8@ZIF-67 composite precursor, and B is a transmission electron microscope image of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material.

[0025] Figure 4 are element mapping images of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material prepared in Example 1 of the present application.

[0026] Figure 5 are X-ray powder diffraction spectra of the material prepared in Example 1 of the present application, wherein a represents the FeMn-ZIF-8@ZIF-67 composite precursor, and b represents the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material.

[0027] Figure 6 are infrared spectra of the material prepared in Example 1 of the present application, wherein a represents the FeMn-ZIF-8@ZIF-67 composite precursor, and b represents the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material.

[0028] Figure 7 are linear sweep voltammetry polarization curve graphs and corresponding Tafel curve graphs of the material prepared in the present application and a commercial IrO2 material, wherein A is a linear sweep voltammetry polarization curve graph, B is a Tafel curve graph, a represents the FeMn-ZIF-8@ZIF-67 composite precursor in Example 1, b represents the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material in Example 1, c represents the commercial IrO2 material, d represents the Fe-ZIF-8@ZIF-67 composite precursor in Example 2, and e represents the cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material without manganese doping in Example 2.

[0029] Figure 8 are cyclic voltammograms of the material prepared in Example 1 at a scan rate of 20-200 mV·s -1 , and a linear fitting graph of the current density difference and the scan rate at a given potential, wherein A is a cyclic voltammogram of the FeMn-ZIF-8@ZIF-67 composite precursor at a scan rate of 20-200 mV·s -1 , and B is a cyclic voltammogram of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material at a scan rate of 20-200 mV·s-1 Cyclic voltammograms at different scan rates, different colors of lines in A, B represent different scan rates, along the direction of the arrow, the scan rate corresponding to each line is 20, 40, 60, 80, 100, 120, 140, 160, 180, 200 mV / s; C is the current density difference Δj (Δj = j a -j c , j a is the anode current, j c is the cathode current) and the linear fitting diagram of the scan rate at a given potential (+1.023 V vs. RHE).

[0030] Figure 9 are the electrochemical impedance spectrograms of the materials prepared in the embodiments of the present application and commercial IrO2 materials, wherein a represents FeMn-ZIF-8@ZIF-67 composite precursor, b represents manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material, c represents commercial IrO2 material, d represents Fe-ZIF-8@ZIF-67 composite precursor, and e represents cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material without manganese doping.

[0031] Figure 10 is the 1000-time CV cycle curve diagram of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material prepared in Embodiment 1 for oxygen evolution reaction. DETAILED DESCRIPTION

[0032] The present application will be further described in conjunction with the embodiments. The processes and methods not described in detail in the following embodiments are conventional methods known in the art, and the raw materials or reagents used in the embodiments are commercially available unless otherwise specified, which can be purchased through commercial channels.

[0033] Embodiment 1, preparation of manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material.

[0034] In combination with Figure 1 , the preparation of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material in the present embodiment is as follows:

[0035] (1) Preparation of FeMn-ZIF-8@ZIF-67 composite precursor.

[0036] FeMn-ZIF-8@ZIF-67 composite precursor was obtained by dissolving 622.76 mg FeS04·7H20, 443.31 mg MnCl2·4H20 and 5.33 g Zn(N03)2·6H20 in 40 mL of methanol (the methanol used is anhydrous methanol, the same below), dissolving 4 g of 2-methylimidazole in 120 mL of methanol, mixing the two methanol solutions and stirring (stirring speed is 350 rpm) for 12 h, centrifuging the obtained product (centrifugal speed is 9000 r / min), washing with methanol for 3 times, and vacuum drying at 50 ℃.

[0037] (2) Preparation of manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material.

[0038] FeMn-ZIF-8@ZIF-67 composite precursor obtained in step (1) was dissolved in 40 mL of methanol together with 1.16 g of Co(N03)2·6H20, 1.23 g of 2-methylimidazole was dissolved in 20 mL of methanol, the two methanol solutions were mixed and stirred (stirring speed is 350 rpm) for 24 h, the obtained product was centrifuged (centrifugal speed is 9000 r / min), washed with methanol for 3 times, vacuum dried at 50 ℃, and then the powder was heated to 920 ℃ at a heating rate of 5 ℃ / min under nitrogen atmosphere, calcined at 920 ℃ for 3 h, to obtain manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material.

[0039] The material prepared in this example was subjected to structural characterization, and the results are shown in Figures 2-6 .

[0040] Figure 2 Fig. 1 and Fig. 2 are scanning electron microscope images of FeMn-ZIF-8@ZIF-67 composite precursor and manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material prepared in this example. As can be seen from the figures, the two materials have good morphology, and the manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material has uniform morphology with nanoparticles attached to the surface.

[0041] Figure 3 Fig. 3 and Fig. 4 are transmission electron microscope images of FeMn-ZIF-8@ZIF-67 composite precursor and manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material prepared in this example. As can be seen from the figures, the FeMn-ZIF-8@ZIF-67 composite precursor is a polyhedron with solid interior and uniform dispersion; the manganese-doped cobalt ferrite nanoparticle@carbon nitride cube composite material has a cubic morphology, uniform dispersion, and a large number of nanoparticles in the interior.

[0042] Figure 4is the elemental mapping of the manganese-doped cobalt ferrite nanoparticle@carbon-nitrogen cubic composite material prepared in the embodiment. As shown in the figure, C, N, Co, Fe and Mn are distributed therein, Co and Fe exist in the form of agglomerated nanoparticles, and Mn is uniformly distributed in the material.

[0043] Figure 5 and Figure 6 are the X-ray powder diffraction pattern and infrared spectrum of the material prepared in the embodiment, respectively, proving the successful synthesis of the manganese-doped cobalt ferrite nanoparticle@carbon-nitrogen cubic composite material.

[0044] Figure 4 Nitrogen exists in the elemental mapping, Figure 5 The X-ray powder diffraction pattern of does not show nitrogen, mainly because: the nitrogen-containing substances released by pyrolysis of 2-methylimidazole as a ligand exist in an amorphous form, and as shown in the elemental mapping, the N content is very low, and the mapping color is very light.

[0045] For the oxygen in the oxide shown in Figure 5 may be derived from the 2-methylimidazole ligand itself, surface adsorption, and oxidation of the material after contacting air, Figure 4 No single nanomaterial containing oxygen was found in the elemental mapping, mainly because: the outer layer of the synthesized material is wrapped by a carbon-nitrogen layer, which produces a very strong signal, seriously interfering with the detection of oxygen.

[0046] Example 2, preparation of cobalt ferrite nanoparticle@carbon-nitrogen cubic composite material.

[0047] (1) Preparation of Fe-ZIF-8@ZIF-67 composite precursor.

[0048] 622.76 mg of FeSO4·7H2O and 5.33 g of Zn(NO3)2·6H2O were dissolved in 40 mL of methanol, 4 g of 2-methylimidazole was dissolved in 120 mL of methanol, and the two methanol solutions were mixed and stirred (stirring speed was 350 r / min) for 12 h. The obtained product was centrifuged (centrifugal speed was 9000 r / min), washed with methanol for 3 times, and vacuum dried at 50 ℃ to obtain the Fe-ZIF-8@ZIF-67 composite precursor.

[0049] (2) Preparation of cobalt ferrite nanoparticle@carbon-nitrogen cubic composite material.

[0050] The 0.1 g Fe-ZIF-8@ZIF-67 composite precursor obtained in step (1) and 1.16 g Co(NO3)2·6H2O were dissolved in 40 mL of methanol, 1.23 g of 2-methylimidazole was dissolved in 20 mL of methanol, the two methanol solutions were thoroughly mixed and stirred (stirring speed was 350 r / min) for 24 h, the obtained product was centrifuged (centrifugal speed was 9000 r / min), washed with methanol for 3 times, vacuum dried at 50 ℃, then the powder was heated to 920 ℃ at a heating rate of 5 ℃ / min under nitrogen atmosphere, calcined at 920 ℃ for 3 h, to obtain cobalt iron oxide nanoparticle@carbon nitride cube composite material.

[0051] Compared with Example 1, the cobalt iron oxide nanoparticle@carbon nitride cube composite material prepared in the embodiment is not doped with manganese.

[0052] Electrocatalytic performance test of water electrolysis oxygen evolution reaction

[0053] The manganese-doped cobalt iron oxide nanoparticle@carbon nitride cube composite material prepared in Example 1 was applied to the electrocatalysis of oxygen evolution reaction, and the electrocatalytic performance was compared with the FeMn-ZIF-8@ZIF-67 composite precursor in Example 1, the Fe-ZIF-8@ZIF-67 composite precursor in Example 2, the cobalt iron oxide nanoparticle@carbon nitride cube composite material not doped with manganese in Example 2, and the commercial IrO2 material, and the specific steps were as follows:

[0054] 1) A three-electrode test system (CHI760 electrochemical workstation) was used, silver / silver chloride was used as the reference electrode, platinum wire was used as the counter electrode, glassy carbon electrode modified with the material to be tested was used as the working electrode, and 1 mol / L potassium hydroxide solution was used as the electrolyte solution.

[0055] 2) 2 mg of the test material was dispersed in 1 mL of naphthol solution to obtain a concentration of 2 mg / mL, 5 μL of the dispersion was dropped on the surface of the glassy carbon electrode, and the working electrode was obtained by drying (150 W) under an infrared lamp.

[0056] 3) The three electrodes were placed in the electrolysis cell and immersed in the potassium hydroxide solution, the electrochemical method was selected, the parameters were set, and the water electrolysis oxygen evolution reaction electrochemical test was carried out.

[0057] The test results are shown in Figures 7-9 , from Figure 7 and Figure 9It can be seen that, compared with the Fe-ZIF-8@ZIF-67 composite precursor, the cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material without manganese doping, the FeMn-ZIF-8@ZIF-67 composite precursor and the commercial IrO2 material, the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material has higher electrocatalytic performance for the oxygen evolution reaction, which is manifested as lower overpotential (334 mV) and lower charge transfer resistance (149.6 W). It can be seen from the LSV curve of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material for the oxygen evolution reaction that the overpotential is 334 mV, which is lower than that of the Fe-ZIF-8@ZIF-67 composite precursor, the cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material without manganese doping, the FeMn-ZIF-8@ZIF-67 composite precursor and the commercial IrO2 material. The charge transfer resistance is 149.6 W, which is lower than that of the Fe-ZIF-8@ZIF-67 composite precursor, the cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material without manganese doping, the FeMn-ZIF-8@ZIF-67 composite precursor and the commercial IrO2 material. Figure 8 It can be seen that, compared with the FeMn-ZIF-8@ZIF-67 composite precursor, the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material has higher electrochemical active surface area (22.01 cm 2 ).

[0058] Figure 10 It can be seen that, compared with the FeMn-ZIF-8@ZIF-67 composite precursor, the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material has higher electrochemical active surface area (22.01 cm 2 ).

[0058] Figure 10 is the 1000 times CV cycle curve of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cube composite material prepared in Example 1 for the oxygen evolution reaction. It can be seen from the figure that, after 1000 times CV cycle of the oxygen evolution reaction, the LSV curve is basically coincided with that before the cycle, indicating that the composite material has good stability.

Claims

1. Use of manganese-doped cobalt ferrite nanoparticles@carbon nitride cubic composite material, characterized in that, The application of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material as a catalyst in an oxygen evolution reaction of water electrolysis; The preparation method of the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material comprises the following steps: (1) dissolving iron salt, manganese salt and zinc salt in methanol to obtain a methanol solution containing iron, manganese and zinc; dissolving 2-methyl imidazole in methanol to obtain a methanol solution of 2-methyl imidazole; (2) mixing the two methanol solutions in step (1), fully stirring, and centrifuging, washing and drying the obtained product to obtain a FeMn-ZIF-8@ZIF-67 composite precursor; (3) dissolving the FeMn-ZIF-8@ZIF-67 composite precursor obtained in step (2) and cobalt salt in methanol to obtain a methanol solution containing cobalt; dissolving 2-methyl imidazole in methanol to obtain a methanol solution of 2-methyl imidazole; (4) mixing the two methanol solutions in step (3), fully stirring, and centrifuging, washing and drying the obtained product to obtain a precursor powder; (5) calcining the precursor powder obtained in step (4) under an inert atmosphere at 900-930 ℃ for 2-5 h, so that zinc is volatilized to remove the template, manganese is doped in situ into the cobalt-iron oxide crystal lattice, cobalt-iron oxide nanoparticles are generated, and 2-methyl imidazole organic ligand carbon-nitrogen is formed into a conductive carbon-nitrogen skeleton, and finally the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material is obtained.

2. Use of the manganese-doped cobalt ferrite nanoparticle@carbon nitride cubic composite material according to claim 1, characterized in that, The iron salt in step (1) is ferrous sulfate heptahydrate, the manganese salt is manganese chloride tetrahydrate, and the zinc salt is zinc nitrate hexahydrate.

3. Use of the manganese-doped cobalt ferrite nanoparticle@carbon nitride cubic composite material according to claim 1, characterized in that, The methanol used in step (1) and step (3) is anhydrous methanol.

4. Use of the manganese-doped cobalt ferrite nanoparticle@carbon nitride cubic composite material according to claim 1, characterized in that, The stirring speed in step (2) and step (4) is 350 rpm.

5. Use of the manganese-doped cobalt ferrite nanoparticle@carbon nitride cubic composite material according to claim 1, characterized in that, In step (5), the inert atmosphere is a nitrogen atmosphere, and the temperature is raised from room temperature to 900-930 ℃ at a heating rate of 5 ℃ / min under the nitrogen atmosphere.

6. Use of the manganese-doped cobalt ferrite nanoparticle@carbon nitride cubic composite material according to claim 1, characterized in that, The application method is as follows: dispersing the manganese-doped cobalt-iron oxide nanoparticle@carbon-nitrogen cubic composite material into a dispersant to obtain a dispersion liquid, dropping the dispersion liquid on the surface of a glassy carbon electrode, and drying to obtain a working electrode.

7. Use of the manganese-doped cobalt ferrite nanoparticle@carbon nitride cubic composite material according to claim 6, characterized in that The dispersant is a naphthol solution.

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