Fe3N-coated MnO2-coated C nanocube supercapacitor positive electrode material and preparation method thereof

Abstract

The invention discloses a preparation method of a Fe3N (at) MnO2 (at) C nanocube supercapacitor positive electrode material, and the method comprises the steps: carrying out the partial etching of a Fe3O4 (at) C nanocube template, and obtaining the partially-etched Fe3O4 (at) C nanocube powder; sintering in the atmosphere of ammonia gas, and adding into deionized water to obtain a solution A; adding KMnO4 and H2SO4 into deionized water, and stirring to obtain a solution B; dropwise adding the solution B into the solution A, and stirring to obtain a Fe3N-coated MnO2-coated C nanocube mother solution; and carrying out centrifugal treatment on the mother liquor to obtain the Fe3N-coated MnO2-coated C nanocube supercapacitor positive electrode material. Part of FeN3 is reserved in the carbon shell through partial etching, and MnO2 can grow on the surfaces of Fe3N nano-particles in the carbon shell instead of growing on the outer surface of the carbon shell by adopting the process sequence of'heating first and then mixing solution 'under the condition of H2SO4. If H2SO4 is not added and a process sequence of'mixing the solution first and then heating 'is adopted, MnO2 grows outside the carbon shell instead of growing on the surface of FeN3 nanoparticles in the carbon shell.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a Fe3N@MnO2@C nanocubic supercapacitor cathode material and its preparation method. Background Technology

[0002] Supercapacitors are considered one of the most promising energy storage devices due to their fast charging and discharging speeds, long-term cycle stability, and excellent safety performance. However, before their practical application, the problem of low energy density must be solved without sacrificing high power density. Capacity and power density can be improved by enhancing the electrochemical kinetics of the electrodes, which can be achieved through the development of novel composite electrode materials. However, the preparation of supercapacitor cathode materials with specific composite structures still faces many challenges. One key challenge lies in how to precisely control the growth position and spatial distribution of manganese dioxide (MnO2) on the core-shell structure, specifically how to control the selective growth of MnO2 inside the carbon shell (i.e., in contact with the iron nitride core) or outside the carbon shell. If grown inside the carbon shell, it is beneficial to utilize the high conductivity of iron nitride, enhance interfacial charge transport, improve capacity and rate performance, and suppress the volume expansion of MnO2 during cycling through the internal confinement effect. Conversely, if grown outside the carbon shell, MnO2 easily detaches from the carbon shell, causing rapid capacity decay during cycling. Summary of the Invention

[0003] Purpose of the invention: To solve the above-mentioned technical problems, the present invention provides a Fe3N@MnO2@C nanocubic supercapacitor cathode material and its preparation method.

[0004] Technical solution: A method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material, characterized by comprising the following steps: Step S01: Add Fe3O4@C nanocube template of mass a to hydrochloric acid solution of concentration b, and perform partial etching using an ultrasonic ice bath to obtain a partially etched substrate; Step S02: Centrifuge the partially etched substrate with deionized water to obtain partially etched Fe3O4@C nanocube powder; Step S03: The partially etched Fe3O4@C nanocube powder is sintered at temperature c for d hours in an ammonia atmosphere to obtain Fe3N@C nanocube powder; Step S04: Add the Fe3N@C nanocube powder to deionized water of volume e, and heat it to temperature f under water bath conditions to obtain solution A; Step S05: Add g of KMnO4 and h of H2SO4 (volume i) to j of deionized water and stir for k minutes to obtain solution B; Step S06: Add solution B dropwise to solution A and stir for m minutes to obtain Fe3N@MnO2@C nanocube mother liquor; Step S07: The Fe3N@MnO2@C nanocube mother liquor is centrifuged with deionized water to obtain Fe3N@MnO2@C nanocube supercapacitor cathode material, wherein MnO2 nanosheets are grown on the surface of Fe3N nanoparticles inside a carbon shell.

[0005] Preferably, in step S01, the mass a of the Fe3O4@C nanocube template added is 0.4g, the concentration b of the hydrochloric acid solution is 4mol / L, and the volume of the hydrochloric acid solution is 51ml.

[0006] Preferably, in step S01, the ultrasonic machine power of the ultrasonic ice bath is 40-50W, and the ice bath time is 40-50min.

[0007] Preferably, in step S03, the sintering temperature c is 600℃ and the sintering time d is 2h.

[0008] Preferably, in step S04, the volume e of the deionized water is 30 ml, and the water bath temperature f is 65-70℃.

[0009] Preferably, in step S05, the mass g of KMnO4 is 0.1-0.2g, the volume i of H2SO4 is 0.05-0.15ml, the concentration h is 98%, and the volume j of deionized water is 20ml.

[0010] Preferably, in step S05, the stirring time k is 5 min.

[0011] Preferably, in step S06, the stirring time m is 30-40 min.

[0012] The present invention also provides a Fe3N@MnO2@C nanocube supercapacitor cathode material, which is prepared by the preparation method of Fe3N@MnO2@C nanocube supercapacitor cathode material in any of the above-described embodiments of the present invention.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: This invention partially etches FeN3 within a carbon shell, allowing MnO2 to grow on the surface of Fe3N nanoparticles within the carbon shell under H2SO4 conditions, rather than on the outer surface of the carbon shell. This results in superior electrochemical performance based on the composite structure. Specifically, by partially etching FeN3 within the carbon shell and employing a 'heating first, then mixing solution' process sequence under H2SO4 conditions, MnO2 can grow on the surface of FeN3 nanoparticles within the carbon shell, rather than on the outer surface. If H2SO4 is not added and the 'mix solution first, then heat' process sequence is used, MnO2 grows on the outside of the carbon shell, rather than on the surface of the FeN3 nanoparticles within the carbon shell. The Fe3N@MnO2@C nanocube supercapacitor cathode material prepared by this invention achieves high power density and energy density while maintaining excellent stability. The preparation method can provide a way to control the composite structure of hollow carbon materials to improve their electrochemical performance.

[0014] The preparation method of the present invention is simple, easy to operate, and low in cost. Attached Figure Description

[0015] Figure 1 ab is a TEM image of Fe3N@C, showing Fe3N nanoparticles growing inside the C shell; cd is a TEM image of Fe3N@C@MnO2, showing MnO2 nanosheets growing outside the C shell; eg is a TEM image of Fe3N@MnO2@C, showing MnO2 nanosheets growing on the surface of Fe3N nanoparticles inside the C shell; h is the elemental distribution map corresponding to g.

[0016] Figure 2 XRD images of Fe3N@MnO2@C; Figure 3 Rate performance of supercapacitors when Fe3N@C, Fe3N@C@MnO2 and Fe3N@MnO2@C are used as cathode materials; Figure 4 When used as cathode materials for Fe3N@C, Fe3N@C@MnO2, and Fe3N@MnO2@C, at 20 A . g -1 Cyclic performance graph at charge / discharge rates. Detailed Implementation

[0017] To facilitate understanding of the technical problems, technical solutions, and beneficial effects of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] An embodiment of the present invention provides a method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material, comprising the following steps: A method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material, characterized by comprising the following steps: Step S01: Add Fe3O4@C nanocube template of mass a to hydrochloric acid solution of concentration b, and perform partial etching using an ultrasonic ice bath to obtain a partially etched substrate; Step S02: Centrifuge the partially etched substrate with deionized water to obtain partially etched Fe3O4@C nanocube powder; Step S03: The partially etched Fe3O4@C nanocube powder is sintered at temperature c for d hours in an ammonia atmosphere to obtain Fe3N@C nanocube powder; Step S04: Add the Fe3N@C nanocube powder to deionized water of volume e, and heat it to temperature f under water bath conditions to obtain solution A; Step S05: Add g of KMnO4 and h of H2SO4 (volume i) to j of deionized water and stir for k minutes to obtain solution B; Step S06: Add solution B dropwise to solution A and stir for m minutes to obtain Fe3N@MnO2@C nanocube mother liquor; Step S07: The Fe3N@MnO2@C nanocube mother liquor is centrifuged with deionized water to obtain Fe3N@MnO2@C nanocube supercapacitor cathode material, wherein MnO2 nanosheets are grown on the surface of Fe3N nanoparticles inside a carbon shell.

[0019] like Figure 1 E, F, and G show TEM images of Fe3N@MnO2@C, which show MnO2 nanosheets growing on the surface of Fe3N nanoparticles inside a C shell. Figure 1 h is Figure 1 The element distribution diagram corresponding to g. Figure 2 The image shows the XRD pattern of Fe3N@MnO2@C, which confirms the material composition. Because Fe3N has undergone high-temperature annealing, its crystallinity is much higher than that of MnO2, so the diffraction peaks shown are those of Fe3N. Figure 3 and Figure 4 The comparisons are of rate performance and cycle performance for different materials. Example 1

[0020] This embodiment provides a method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material, including the following steps: Step S01: Add 0.4g of Fe3O4@C nanocube template to 51ml of 4mol / L hydrochloric acid solution, and perform partial etching using a 40W ultrasonic machine in an ice bath for 50min to obtain a partially etched substrate; Step S02: Centrifuge the partially etched substrate with deionized water to obtain partially etched Fe3O4@C nanocube powder; Step S03: The partially etched Fe3O4@C nanocube powder is sintered at 600°C for 2 hours in an ammonia atmosphere to obtain Fe3N@C nanocube powder. Step S04: Add the Fe3N@C nanocube powder to 30 ml of deionized water, and heat it to 65°C in a water bath to obtain solution A; Step S05: Add 0.1g of KMnO4 and 0.05ml of 98% H2SO4 to 20ml of deionized water and stir for 5 minutes at room temperature to obtain solution B; Step S06: Add solution B dropwise to solution A and stir at room temperature for 30 minutes to obtain Fe3N@MnO2@C nanocube mother liquor; Step S07: The Fe3N@MnO2@C nanocube mother liquor is centrifuged with deionized water to obtain Fe3N@MnO2@C nanocube supercapacitor cathode material, wherein MnO2 nanosheets are grown on the surface of Fe3N nanoparticles inside a carbon shell. Example 2

[0021] This embodiment provides a method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material, including the following steps: Step S01: Add 0.4g of Fe3O4@C nanocube template to 51ml of 4mol / L hydrochloric acid solution, and perform partial etching using a 50W ultrasonic machine in an ice bath for 40min to obtain a partially etched substrate; Step S02: Centrifuge the partially etched substrate with deionized water to obtain partially etched Fe3O4@C nanocube powder; Step S03: The partially etched Fe3O4@C nanocube powder is sintered at 600°C for 2 hours in an ammonia atmosphere to obtain Fe3N@C nanocube powder. Step S04: Add the Fe3N@C nanocube powder to 30 ml of deionized water, and heat it to 70°C in a water bath to obtain solution A; Step S05: Add 0.2g of KMnO4 and 0.15ml of 98% H2SO4 to 20ml of deionized water and stir for 5 minutes at room temperature to obtain solution B; Step S06: Add solution B dropwise to solution A and stir at room temperature for 40 minutes to obtain Fe3N@MnO2@C nanocube mother liquor; Step S07: The Fe3N@MnO2@C nanocube mother liquor is centrifuged with deionized water to obtain Fe3N@MnO2@C nanocube supercapacitor cathode material, wherein MnO2 nanosheets are grown on the surface of Fe3N nanoparticles inside a carbon shell. Example 3

[0022] This embodiment provides a method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material, including the following steps: Step S01: Add 0.4g of Fe3O4@C nanocube template to 51ml of 4mol / L hydrochloric acid solution, and perform partial etching using a 45W ultrasonic machine in an ice bath for 45min to obtain a partially etched substrate; Step S02: Centrifuge the partially etched substrate with deionized water to obtain partially etched Fe3O4@C nanocube powder; Step S03: The partially etched Fe3O4@C nanocube powder is sintered at 600°C for 2 hours in an ammonia atmosphere to obtain Fe3N@C nanocube powder. Step S04: Add the Fe3N@C nanocube powder to 30 ml of deionized water, and heat it to 67°C in a water bath to obtain solution A; Step S05: Add 0.15g of KMnO4 and 0.1ml of 98% H2SO4 to 20ml of deionized water and stir for 5 minutes at room temperature to obtain solution B; Step S06: Add solution B dropwise to solution A and stir at room temperature for 35 minutes to obtain Fe3N@MnO2@C nanocube mother liquor; Step S07: The Fe3N@MnO2@C nanocube mother liquor is centrifuged with deionized water to obtain Fe3N@MnO2@C nanocube supercapacitor cathode material, wherein MnO2 nanosheets are grown on the surface of Fe3N nanoparticles inside a carbon shell. Example 4

[0023] This embodiment describes a Fe3N@MnO2@C nanocubic supercapacitor cathode material prepared using the preparation method of the present invention. Comparative Example 1

[0024] In this embodiment, Fe3N@C nanocubes are used as the positive electrode material for a supercapacitor. The preparation method is as follows: 0.4 g of Fe3O4@C nanocube template is added to 51 ml of a 4 M hydrochloric acid solution. Partial etching is performed by ultrasonication in an ice bath for 40-50 min using an ultrasonic machine with a power of 40-50 W. Afterwards, the partially etched Fe3O4@C nanocube powder is obtained by centrifugation with deionized water. The partially etched Fe3O4@C nanocube powder is then sintered at 600 ℃ for 2 h under an ammonia atmosphere to obtain the Fe3N@C nanocube supercapacitor positive electrode material. Figure 1 Figures a and b show TEM images of Fe3N@C. As can be seen from the figures, some Fe3N nanoparticles are retained inside the carbon shell. Comparative Example 2

[0025] In this embodiment, Fe3N@C@MnO2 nanocubes are used as the positive electrode material for a supercapacitor. The preparation method is as follows: Fe3N@C nanocubes are dispersed in 30 ml of deionized water using the method described in Example 1, and labeled as A. 0.1-0.2 g of KMnO4 is dissolved in 20 ml of deionized water and labeled as B. Solution B is added to solution A, then heated to 65-70 °C and stirred for 1 h. After filtration and drying at 80 °C for 10 h, the Fe3N@C@MnO2 nanocube supercapacitor positive electrode material is obtained. Figure 1 As shown in c and d, these are TEM images of Fe3N@C@MnO2, which show that MnO2 nanosheets grow on the outer surface of the carbon shell.

[0026] This invention discloses a method for preparing a Fe3N@MnO2@C nanocube supercapacitor cathode material. Compared with comparative examples and existing technologies, this method involves partially etching a Fe3O4@C nanocube template to retain a portion of Fe3O4 within the carbon shell. After sintering in an ammonia atmosphere and undergoing further treatment, partially etched Fe3O4@C nanocube powder is obtained. Then, under acidic conditions, MnO2 is grown on the surface of the Fe3N nanoparticles within the carbon shell, meaning the MnO2 grows inside the carbon shell rather than on its exterior. The resulting Fe3N@MnO2@C nanocube supercapacitor cathode material exhibits high power density and energy density while maintaining excellent stability. The preparation method of this invention also has advantages such as simplicity, ease of operation, and low cost.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a Fe3N@MnO2@C nanocubic supercapacitor cathode material, characterized in that, Includes the following steps: step S01: Add Fe3O4@C nanocube template of mass a to hydrochloric acid solution of concentration b, and perform partial etching using an ultrasonic ice bath to obtain a partially etched substrate; Step S02: Centrifuge the partially etched substrate with deionized water to obtain partially etched Fe3O4@C nanocube powder; Step S03: The partially etched Fe3O4@C nanocube powder is sintered at temperature c for d hours in an ammonia atmosphere to obtain Fe3N@C nanocube powder; Step S04: Add the Fe3N@C nanocube powder to deionized water of volume e, and heat it to temperature f under water bath conditions to obtain solution A; Step S05: Add g of KMnO4 and h of H2SO4 (volume i) to j of deionized water and stir for k minutes to obtain solution B; Step S06: Add solution B dropwise to solution A and stir for m minutes to obtain Fe3N@MnO2@C nanocube mother liquor; Step S07: The Fe3N@MnO2@C nanocube mother liquor is centrifuged with deionized water to obtain Fe3N@MnO2@C nanocube supercapacitor cathode material, wherein MnO2 nanosheets are grown on the surface of Fe3N nanoparticles inside a carbon shell.

2. The method for preparing the Fe3N@MnO2@C nanocubic supercapacitor cathode material according to claim 1, characterized in that: In step S01, the mass a of the Fe3O4@C nanocube template added is 0.4g, the concentration b of the hydrochloric acid solution is 4mol / L, and the volume of the hydrochloric acid solution is 51ml.

3. The method for preparing the Fe3N@MnO2@C nanocubic supercapacitor cathode material according to claim 1, characterized in that: In step S01, the ultrasonic machine power for the ultrasonic ice bath is 40-50W, and the ice bath time is 40-50min.

4. The method for preparing the positive electrode material of a Fe3N@MnO2@C nanocubic supercapacitor according to claim 1, characterized in that: In step S03, the sintering temperature c is 600℃ and the sintering time d is 2h.

5. The method for preparing the positive electrode material of a Fe3N@MnO2@C nanocubic supercapacitor according to claim 1, characterized in that: In step S04, the volume e of the deionized water is 30 ml, and the water bath temperature f is 65-70℃.

6. The method for preparing the Fe3N@MnO2@C nanocubic supercapacitor cathode material according to claim 1, characterized in that: In step S05, the mass g of KMnO4 is 0.1-0.2g, the volume i of H2SO4 is 0.05-0.15ml, the concentration h is 98%, and the volume j of deionized water is 20ml.

7. The method for preparing the Fe3N@MnO2@C nanocubic supercapacitor cathode material according to claim 1, characterized in that: In step S05, the stirring time k is 5 minutes.

8. The method for preparing the positive electrode material of a Fe3N@MnO2@C nanocubic supercapacitor according to claim 1, characterized in that: In step S06, the stirring time m is 30-40 min.

9. A Fe3N@MnO2@C nanocubic supercapacitor cathode material, characterized in that: It is prepared by the method for preparing Fe3N@MnO2@C nanocubic supercapacitor cathode material according to any one of claims 1-8.

Images