NiCo2S4-coated NiCoC2O4 composite material with three-dimensional petal-shaped structure and application of NiCo2S4-coated NiCoC2O4 composite material

Abstract

The invention discloses a NiCo2S4-coated NiCoC2O4 composite material with a three-dimensional petal-shaped structure and application thereof, the NiCo2S4-coated NiCoC2O4 composite material is a three-dimensional petal-shaped sheet-shaped structure composite material formed by mutual crosslinking of a plurality of NiCo2S4-coated NiCoC2O4 heterojunctions, and the NiCo2S4-coated NiCoC2O4 heterojunctions are sheet-shaped core-shell structure heterojunctions formed by dispersing array form NiCo2S4 nanowires in NiCoC2O4 nanosheets. According to the design of the adhesive-free electrode material with the layered nano structure, the specific capacitance of the electrode material serving as a supercapacitor electrode material under the current density of 1A g <-1 > reaches up to 3317F g <-1 >, the specific capacitance of 1748F g <-1 > is still kept under the current density of 20A g <-1 >, 87.7% of capacity is still kept after 5000 times of rapid charge-discharge cycles, and the electrode material shows excellent specific capacitance, good rate capability and cycling stability. Meanwhile, NiCo2S4-coated NiCoC2O4 has relatively good electro-catalytic oxygen evolution (OER) performance, has low overpotential of 235mV under the current density of 100mA cm <-2 >, and can be stably circulated for 130 hours under the current density of 10mA cm <-2 >.

Description

Technical Field

[0001] The invention belongs to the field of nanocomposite materials, and in particular relates to a NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-shaped structure and applications thereof. Background Art

[0002] Among various energy storage systems, supercapacitors play an important role in many advanced energy storage systems with their excellent power density, long life, and good safety. However, due to its relatively low energy density, the further application of supercapacitors is hindered. Developing a new type of electrode material with high specific capacitance is an effective way to improve energy density. At present, various transition metal oxalates are mostly used as precursors to generate oxides, and some researchers directly use transition metal oxalates as active materials for supercapacitor electrodes. At the same time, transition metal oxalates are considered to be electrode materials with higher specific capacitance and better cycle performance than the corresponding oxides and hydroxides. The oxalic acid molecules in transition metal oxalates help to form an open structure, promote ion diffusion, increase the ion diffusion rate, and increase the ionic conductivity of the material. For example, Wang et al. prepared Ni 0.55 Co 0.45 C2O4, at 1A g -1 The specific capacitance is 562C g -1 , 5A g -1 The capacitance retention rate after 4000 cycles was 87.4% (Nanoscale, 29 (11), 13894-13902). Hussain et al. prepared NiInC2O4 at 1A g -1 The specific capacitance is 835F g -1 , the capacitance retention rate after 3000 cycles was 87.81% (Ceramics International, 50(23), 50884-50889). However, most of the metal oxalate electrode materials reported in the literature are in the form of large particles with small specific surface area, which cannot be fully infiltrated by the electrolyte, resulting in that their electrochemical active sites are difficult to fully utilize. In addition, due to the poor conductivity of transition metal oxalates, their rate performance and cycle stability are poor. A suitable method is to combine them with materials with good conductivity to achieve the electrochemical performance of transition metal-based oxalate electrode materials. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure and its application.

[0004] The first aspect of the present invention provides a NiCo2S4@NiCoC2O4 composite material having a three-dimensional petal shape, which is a three-dimensional petal-shaped sheet structure composite material formed by cross-linking of multiple NiCo2S4@NiCoC2O4 heterojunctions, wherein the NiCo2S4@NiCoC2O4 heterojunction is a sheet-like core-shell structure heterojunction formed by array-shaped NiCo2S4 nanowires dispersed in NiCoC2O4 nanosheets.

[0005] Preferably, the method for preparing the NiCo2S4@NiCoC2O4 heterojunction comprises the following steps:

[0006] (A) The array-shaped NiCo2S4 nanowires were placed in a mixed aqueous solution of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and ammonium oxalate, and then transferred to a hydrothermal kettle for hydrothermal reaction. After washing and drying, a NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal shape was obtained.

[0007] Preferably, in step (A), the molar ratio of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and ammonium oxalate in the aqueous solution is 0.9:(0.4-0.8):(1.2-1.8).

[0008] Preferably, in step (A), the hydrothermal reaction is specifically: hydrothermal reaction at 100-150° C. for 0.5-15 h.

[0009] Preferably, the method for preparing the array-shaped NiCo2S4 nanowires comprises the following steps:

[0010] S1: pre-treating the nickel foam to remove stains and an oxide layer on the surface of the nickel foam, and then drying; the specific removal method is to sequentially add hydrochloric acid, acetone and deionized water to the nickel foam for ultrasonic treatment to remove stains and an oxide layer on the surface, wherein the concentration of the hydrochloric acid solution in step S1 is 1-4 mol L -1 ; For example, it can be 1 mol L -1 , 2 mol L -1 , 3 mol L -1 and 4 mol L -1 , wherein the preferred hydrochloric acid concentration is 3 mol L -1 ;

[0011] S2: preparing a Ni-Co precursor, placing the nickel foam in a mixed aqueous solution of Ni(NO3)2·6H2O, Co(NO3)2·6H2O, NH4F and urea, carrying out a hydrothermal reaction, and then washing and drying to obtain a Ni-Co precursor loaded with nickel foam; the washing and drying can be specifically carried out by washing with deionized water and anhydrous ethanol for 3 times each, and vacuum drying at 60°C;

[0012] S3: placing the Ni-Co precursor loaded on nickel foam into a Na2S solution for sulfidation hydrothermal reaction to obtain NiCo2S4 nanowires loaded on nickel foam.

[0013] Preferably, in step S1, the molar ratio of Ni(NO3)2·6H2O, Co(NO3)2·6H2O, NH4F and urea in the aqueous solution 1 is 0.5:(0.8-1.2):(0.8-1.2):(2-3.5).

[0014] Preferably, in step S2, the conditions of the hydrothermal reaction are: the hydrothermal temperature is 100-150° C., and the hydrothermal time is 8-16 h.

[0015] Preferably, in step S3, the concentration of the Na2S solution is 0.05 mM to 0.2 mM, and the specific conditions of the sulfidation hydrothermal reaction are: hydrothermal reaction at 100 to 160°C for 4 to 10 hours.

[0016] The second aspect of the present invention provides a use of the NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure as a supercapacitor electrode material. As a layered nanostructured binder-free electrode material, at 1A g -1 The specific capacitance at current density is as high as 3317F g -1 , at 20Ag -1 Still 1748F g -1 The specific capacitance of the battery can reach 87.7% after 5000 rapid charge and discharge cycles, showing excellent specific capacitance, good rate performance and cycle stability.

[0017] The third aspect of the present invention provides a use of the NiCo2S4@NiCoC2O4 composite material having a three-dimensional petal-like structure as an OER material. -2 At a current density of 10 mA cm, it has a low overpotential of 235 mV. -2 At a current density of 1.5 Å, it can be stably cycled for 130 h, showing good OER performance.

[0018] The innovative mechanism of the present invention is:

[0019] After in-depth research, the inventors of this application found that since metal sulfides have rich electrochemical activity, they can improve specific capacitance, ion diffusion kinetics and cyclicity. Combining them with transition metal oxalate materials not only makes up for the defect of poor conductivity of oxalate, but also greatly enhances the overall electrochemical performance of transition metal oxalate materials. Therefore, the present invention intends to design a heterojunction structure of NiCo2S4@NiCoC2O4 on a three-dimensional substrate nickel foam. The electrode material design of NiCo2S4 core and NiCoC2O4 shell shows many advantages. NiCo2S4 and transition metal oxalate are themselves promising high-capacitance materials. The three-dimensional petal-like structure makes it easy for the electrolyte to diffuse into the material, improves the utilization rate of the electrode material, has rich diffusion channels and good structural stability, and due to the synergistic effect, shows more extraordinary electrochemical performance. In addition, the binder-free design can also overcome the problems of particle agglomeration, reduced active area, deteriorated conductivity and cumbersome process caused by the conventional coating method, thereby improving the specific capacitance, rate performance and cycle stability of the NiCo2S4@NiCoC2O4 heterojunction, so that it shows good application prospects in supercapacitors. At the same time, it exhibits excellent performance in OER, and the NiCo2S4@NiCoC2O4 heterojunction has dual functional applications.

[0020] The implementation of the present invention has the following beneficial effects:

[0021] (1) NiCo2S4@NiCoC2O4 at 1A g -1 The specific capacitance at current density is as high as 3317F g -1 , at 20A g -1 Still 1748F g -1 The specific capacitance of the battery is 87.7%, and after 5000 rapid charge and discharge cycles, the capacity is still maintained at 87.7%, showing excellent specific capacitance, good rate performance and cycle stability. -2 At a current density of 10 mA cm, it has a low overpotential of 235 mV. -2 At a current density of 1.5 Å, it can stably cycle for 130 h, thus demonstrating its dual functionality that can be effectively utilized in supercapacitors and OER materials.

[0022] (2) NiCo2S4 nanowires are dispersed in NiCoC2O4 nanosheets to form a three-dimensional petal-shaped sheet structure, which produces a synergistic effect and provides sufficient electrode / electrolyte contact area and efficient ion transport path.

[0023] (3) In the NiCo2S4@NiCoC2O4 core-shell structure, highly conductive NiCo2S4 nanowires are dispersed in NiCoC2O4 nanosheets. Transition metal oxalates themselves have the characteristics of high capacitance. Combining with NiCo2S4 can greatly improve the conductivity of NiCoC2O4, so that NiCo2S4@NiCoC2O4 exhibits excellent electrochemical properties.

[0024] (4) The NiCo2S4@NiCoC2O4 heterojunction forms a three-dimensional spatial network structure, which not only provides abundant electrochemical active sites and sufficient contact area between the electrode and the electrolyte, but also promotes the transmission and infiltration of electrolyte ions. In addition, the binder-free electrode material design solves the problem of easy agglomeration of particles, thereby further improving the rate performance and cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0026] Figure 1 (a)-(c) are scanning electron microscope (SEM) images of NiCo2S4 nanowires in comparative example 1 at different magnifications; (d)-(f) are scanning electron microscope (SEM) images of NiCoC2O4 in comparative example 2 at different magnifications; (g)-(i) are SEM images of NiCo2S4@NiCoC2O4 in example 1 at different magnifications;

[0027] Figure 2 (a)-(b) are scanning electron microscope (SEM) images of NiCo2S4@NiCoC2O4 at different magnifications after reaction for 0.5 h in comparative example 3; (c)-(d) are scanning electron microscope (SEM) images of NiCo2S4@NiCoC2O4 at different magnifications after reaction for 2.5 h in comparative example 4; (e)-(f) are scanning electron microscope (SEM) images of NiCo2S4@NiCoC2O4 at different magnifications after reaction for 5 h in comparative example 5; (g)-(h) are scanning electron microscope (SEM) images of NiCo2S4@NiCoC2O4 at different magnifications after reaction for 15 h in comparative example 6;

[0028] Figure 3(a) Transmission electron microscopy (TEM) image of NiCo2S4@NiCoC2O4 in Example 1; (b)-(d) High resolution transmission (HR-TEM) images and selected area electron diffraction (SAED) images of NiCo2S4@NiCoC2O4; (e)-(j) Energy dispersive X-ray spectroscopy (EDS) images of NiCo2S4@NiCoC2O4;

[0029] Figure 4 (a) X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) of NiCo2S4@NiCoC2O4 in Example 1; (b) Ni 2 p Spectrum; (c) Co 2 p Spectrum; (d) S2 p Spectrum; (e) C 1 s Spectrum; (f) O 1 s Spectrum;

[0030] Figure 5 The electrochemical properties of the supercapacitor materials of NiCo2S4@NiCoC2O4 in Example 1 and NiCo2S4 in Comparative Example 1 and NiCoC2O4 in Comparative Example 2 are shown in Figure 2: (a) Cyclic voltammograms of the supercapacitor material of NiCo2S4@NiCoC2O4 in Example 1 at different scan rates; (b) Cyclic voltammograms of the supercapacitor materials of NiCo2S4@NiCoC2O4 in Example 1 and NiCo2S4 in Comparative Example 1 and NiCoC2O4 in Comparative Example 2 at 20 m V s -1 Cyclic voltammograms at different scan rates; (c) Constant current charge and discharge diagrams of the NiCo2S4@NiCoC2O4 supercapacitor material in Example 1 at different current densities; (d) Cyclic voltammograms of the NiCo2S4@NiCoC2O4 supercapacitor material in Example 1 and the NiCo2S4 in Comparative Example 1 and the NiCoC2O4 supercapacitor material in Comparative Example 2 at 5A g -1 Constant current charge and discharge diagram under current density; (e) Rate performance diagram of NiCo2S4@NiCoC2O4 in Example 1 and NiCo2S4 in Comparative Example 1 and NiCoC2O4 in Comparative Example 2 supercapacitor materials; (f) NiCo2S4@NiCoC2O4 in Example 1 and NiCo2S4 in Comparative Example 1 supercapacitor materials at 5Ag -1 Cycling stability under current density;

[0031] Figure 6 Electrochemical properties of the NiCo2S4@NiCoC2O4 supercapacitor materials in Example 1 and Comparative Example 3: (a) The NiCo2S4@NiCoC2O4 supercapacitor materials in Example 1 and Comparative Example 3 at 20 mV s -1Cyclic voltammograms at scan rates; (b) NiCo2S4@NiCoC2O4 supercapacitor materials in Example 1 and Comparative Example 3 at 2A g -1 Constant current charge and discharge diagram under current density; (c) rate performance diagram of NiCo2S4@NiCoC2O4 supercapacitor materials in Example 1 and Comparative Example 3;

[0032] Figure 7 OER performance of NiCo2S4@NiCoC2O4 in Example 1, NiCo2S4 in Comparative Example 1, and NiCoC2O4 in Comparative Example 2: (a) LSV polarization curve; (b) 100 mA cm -2 Overpotential under current density; (c) EIS curve; (d) 10 mA cm -2 Stability curves at different current densities. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] Example 1

[0035] (1) Commercial nickel foam (20 mm × 20 mm × 1.6 mm) was pretreated with ultrasonic vibration in 3 M HCl, acetone, and deionized water several times to remove the oxide layer and residual impurities, and then dried in vacuum at 60 °C for 12 h.

[0036] (2) 0.5 mmol Ni(NO3)2·6H2O, 1 mmol Co(NO3)2·6H2O, 1 mmol NH4F and 2.5 mmol urea were dissolved in 25 mL deionized water and magnetically stirred for 30 min to obtain a uniform mixed solution.

[0037] (3) Then, the uniformly mixed solution and a piece of pretreated nickel foam were transferred into a 50 mL Teflon stainless steel autoclave and then hydrothermally treated at 120 °C for 12 h, followed by washing and drying to generate a Ni-Co precursor.

[0038] (4) Place the nickel foam loaded with Ni-Co precursor into a 30 mL 0.1 mol L -1 The solution was placed in a 50 mL autoclave at 120 °C for 8 h and then cooled to room temperature. Finally, the nickel foam loaded with NiCo2S4 was thoroughly washed and dried overnight.

[0039] (5) Then, 0.9 mmol Ni(NO3)2·6H2O, 0.6 mmol Co(NO3)2·6H2O and 1.5 mmol ammonium oxalate were dissolved in 30 mL of deionized water to obtain a light green turbid solution.

[0040] (6) The light green turbid solution and the nickel foam loaded with NiCo2S4 were transferred to a 50 mL Teflon stainless steel autoclave and hydrothermally treated at 110 °C for 10 h. Finally, it was rinsed with deionized water and anhydrous ethanol several times and dried at 60 °C to obtain the NiCo2S4@NiCoC2O4 core-shell structure.

[0041] Comparative Example 1 :Synthesis of NiCo2S4 Nanowire Arrays

[0042] Dissolve 0.5mmol Ni(NO3)2.6H2O, 1mmol Co(NO3)2.6H2O, 1mmol NH4F and 2.5mmol urea in 25mL deionized water, stir magnetically for 30min to obtain a uniform mixed solution, transfer the mixed solution and a piece of pretreated nickel foam to a Teflon stainless steel autoclave. Then perform hydrothermal treatment at 120℃ for 12h, and then wash and dry to generate a Ni-Co precursor. Place 30mL 0.1mol L -1 The Na2S solution was placed in a 50 mL autoclave. The solution was hydrothermally treated at 120 °C for 8 h and then cooled to room temperature naturally. Finally, the solution was washed with deionized water and anhydrous ethanol for several times and dried overnight to obtain the NiCo2S4 nanowire array.

[0043] Comparative Example 2 :Preparation of NiCoC2O4 materials

[0044] 0.9mmol Ni(NO3)2·6H2O, 0.6mmol Co(NO3)2·6H2O and 1.5mmol ammonium oxalate were dissolved in 30mL deionized water and magnetically stirred for 30 minutes to obtain a uniform mixed solution. The mixed solution and a piece of pretreated nickel foam were transferred to a Teflon stainless steel autoclave and then hydrothermally treated at 110°C for 10h. The material was then washed and dried to obtain NiCoC2O4 material.

[0045] Comparative Example 3

[0046] The difference between this comparative example and Example 1 is that in step S6, the light green turbid solution and the nickel foam loaded with NiCo2S4 were transferred to a 50 mL Teflon stainless steel autoclave and subjected to hydrothermal reaction at 110°C for 0.5 h, 2.5 h, 5 h, and 15 h, respectively. Finally, the solution was rinsed with deionized water and anhydrous ethanol several times and dried at 60°C.

[0047] Comparative Example 4

[0048] The difference between this comparative example and Example 1 is that in step S6, the light green turbid solution and the nickel foam loaded with NiCo2S4 were transferred to a 50 mL Teflon stainless steel autoclave and subjected to a hydrothermal reaction at 110° C. for 2.5 h. Finally, they were rinsed several times with deionized water and anhydrous ethanol and dried at 60° C.

[0049] Comparative Example 5

[0050] The difference between this comparative example and Example 1 is that in step S6, the light green turbid solution and the nickel foam loaded with NiCo2S4 are transferred to a 50 mL Teflon stainless steel autoclave and subjected to a hydrothermal reaction at 110° C. for 5 h. Finally, the solution is rinsed several times with deionized water and anhydrous ethanol and dried at 60° C.

[0051] Comparative Example 6

[0052] The difference between this comparative example and Example 1 is that in step S6, the light green turbid solution and the nickel foam loaded with NiCo2S4 are transferred to a 50 mL Teflon stainless steel autoclave and subjected to a hydrothermal reaction at 110° C. for 15 h. Finally, the solution is rinsed several times with deionized water and anhydrous ethanol and dried at 60° C.

[0053] Microscopic characterization

[0054] The NiCo2S4@NiCoC2O4 materials of Example 1 and Comparative Examples 1-6 were subjected to microscopic characterization by multiple means, and the results are as follows:

[0055] (1) By Figure 1 It can be seen that the NiCo2S4 in Comparative Example 1 is in the morphology of nanowires, and the morphology of NiCoC2O4 in Comparative Example 2 is in the morphology of nanosheets. After secondary loading, the NiCo2S4 nanowires are gradually wrapped by NiCoC2O4 and dispersed in the nanosheets to form a NiCo2S4@NiCoC2O4 petal-shaped lamellar core-shell structure, thereby improving the conductivity of NiCoC2O4 and producing a synergistic effect. At the same time, it provides sufficient electrode / electrolyte contact area and efficient ion transmission path, and the material exhibits excellent electrochemical properties.

[0056] (2) By Figure 2 It can be seen that when the reaction time is 0.5h, 2.5h, and 5h, due to the short reaction time, NiCoC2O4 is not formed on the nanowires, and NiCo2S4 is not completely wrapped by NiCoC2O4. When the reaction time is 15h, due to the long reaction time, the nanosheets are accumulated, which hinders the ion transmission pathway.

[0057] (3) By Figure 3 It can be seen that the NiCo2S4@NiCoC2O4 structure in Example 1 is a petal-shaped core-shell structure formed by NiCoC2O4 nanosheets connecting NiCo2S4 nanowires, and the Ni, Co, S, C and O elements are evenly distributed in the material.

[0058] (4) By Figure 4 It can be seen that the NiCo2S4@NiCoC2O4 core-shell structure of Example 1 has been successfully produced. The material contains Ni, Co, C, O and S elements.

[0059] Electrochemical performance test

[0060] (1) The supercapacitor performance of NiCo2S4@NiCoC2O4 bicarbonate in Example 1 was tested using an electrochemical workstation: the cyclic voltammetry curves at different scan rates are shown in FIG. Figure 5 As shown in a, a pair of strong redox peaks can be clearly seen, indicating that the electrode material has typical battery-type capacitance behavior; the constant current charge and discharge curves show good symmetry ( Figure 5 c); Cyclic voltammetry comparison of NiCo2S4@NiCoC2O4 in Example 1 and NiCo2S4 nanowires in Comparative Example 1 ( Figure 5 b), constant current charge and discharge curve comparison chart ( Figure 5 d), rate performance comparison chart ( Figure 5 e), Cyclic stability performance comparison chart ( Figure 5 f), it can be seen that the NiCo2S4@NiCoC2O4 in Example 1 has a higher specific capacity, better charge storage capacity, better rate performance, and a higher cycle life.

[0061] (2) Cyclic voltammetry comparison of NiCo2S4@NiCoC2O4 with a reaction time of 10 h in Example 1 and different reaction times in Comparative Example 3 ( Figure 6 a), constant current charge and discharge curve comparison chart ( Figure 6 b), rate performance comparison chart ( Figure 6 c) at 2A g -1 At a current density of 1.37 W, the specific capacitances of the reaction for 10 h, 0.5 h, 2.5 h, 5 h, and 15 h were 3317 F g -1, 1766.8F g -1 , 1578.7F g -1 , 1969.5F g -1 、2343.5Fg -1 It can be seen that the specific capacity of NiCo2S4@NiCoC2O4 in Example 1 is higher, the charge storage capacity is better, and the rate performance is better after the reaction for 10 h.

[0062] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure, characterized in that: It is a three-dimensional petal-shaped sheet structure composite material formed by multiple NiCo2S4@NiCoC2O4 heterojunctions cross-linked with each other, wherein the NiCo2S4@NiCoC2O4 heterojunction is a sheet-like core-shell structure heterojunction formed by array-shaped NiCo2S4 nanowires dispersed in NiCoC2O4 nanosheets.

2. The NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure according to claim 1, characterized in that: The preparation method of the NiCo2S4@NiCoC2O4 heterojunction comprises the following steps: (A) The array-shaped NiCo2S4 nanowires were placed in a mixed aqueous solution of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and ammonium oxalate, and then transferred to a hydrothermal kettle for hydrothermal reaction. After washing and drying, a NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal shape was obtained.

3. The NiCo2S4@NiCoC2O4 composite material having a three-dimensional petal-like structure according to claim 2, characterized in that: In step (A), the molar ratio of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and ammonium oxalate in the aqueous solution is 0.9:(0.4-0.8):(1.2-1.8).

4. The NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure according to claim 2, characterized in that: In step (A), the hydrothermal reaction is specifically: hydrothermal reaction at 100-150° C. for 0.5-15 h.

5. The NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure according to claim 1, characterized in that: The method for preparing the array-shaped NiCo2S4 nanowires comprises the following steps: S1: pre-treating the nickel foam to remove stains and an oxide layer on the surface of the nickel foam, and then drying; S2: preparing a Ni-Co precursor, placing nickel foam in a mixed aqueous solution of Ni(NO3)2·6H2O, Co(NO3)2·6H2O, NH4F and urea, performing a hydrothermal reaction, and then washing and drying to obtain a Ni-Co precursor loaded with nickel foam; S3: placing the Ni-Co precursor loaded on nickel foam into a Na2S solution for sulfidation hydrothermal reaction to obtain NiCo2S4 nanowires loaded on nickel foam.

6. The NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure according to claim 5, characterized in that: In step S1, the molar ratio of Ni(NO3)2·6H2O, Co(NO3)2·6H2O, NH4F and urea in the aqueous solution 1 is 0.5:(0.8-1.2):(0.8-1.2):(2-3.5).

7. The NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure according to claim 5, characterized in that: In step S2, the conditions of the hydrothermal reaction are: the hydrothermal temperature is 100-150° C., and the hydrothermal time is 8-16 hours.

8. The NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure according to claim 5, characterized in that: In step S3, the concentration of the Na2S solution is 0.05 mM to 0.2 mM, and the specific conditions of the sulfidation hydrothermal reaction are: hydrothermal reaction at 100 to 160°C for 4 to 10 hours.

9. Use of the NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure as claimed in any one of claims 1 to 8 as a supercapacitor electrode material.

10. Use of the NiCo2S4@NiCoC2O4 composite material with a three-dimensional petal-like structure as claimed in any one of claims 1 to 8 as an OER material.

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