Nitrogen-doped nickel-cobalt bimetallic porous carbon composite material, preparation and application thereof

Abstract

This invention relates to the field of supercapacitor electrode materials, particularly bimetallic materials, and more specifically to nitrogen-doped nickel-cobalt bimetallic porous carbon composite materials, their preparation, and applications. The nitrogen-doped nickel-cobalt bimetallic porous carbon composite material is obtained by synthesizing a precursor via a hydrothermal method using 1,2,4-triazole-3-carboxylic acid as a ligand, followed by calcination at 600℃. This composite material contains abundant redox active sites and excellent conductivity, especially exhibiting excellent electrochemical performance under a 1:1 nickel-cobalt molar ratio. Experiments show that when the nickel-cobalt molar ratio is 1:1 during MOF synthesis, the obtained NC / NiCo1 / 1 exhibits excellent electrochemical performance at a mass ratio of 1.0 A g. ‑1 Below this, the specific capacitance can reach 595.76 F g. ‑1 It also exhibits excellent cycling performance, retaining 92.30% of its specific capacitance after 3000 cycles, and its specific surface area can reach 68.87 m². 2 g ‑1 .

Description

TECHNICAL FIELD

[0001] The present application relates to the field of supercapacitor electrode material research, in particular to the field of bimetallic material research, more specifically to a nitrogen-doped nickel-cobalt bimetallic porous carbon composite material and preparation and application thereof. BACKGROUND

[0002] Supercapacitors are ideal energy storage devices. Pseudocapacitive capacitors have higher specific capacitance than conventional double-layer capacitors due to their fast and reversible Faradaic redox reactions, so how to further improve the electrochemical performance of pseudocapacitive capacitors is the direction and field that the skilled in the art strives to develop.

[0003] Bimetallic electrode materials can provide more theoretical active sites for the generation of pseudocapacitance, so the research and development of bimetallic materials has also become a hot topic for the skilled in the art. SUMMARY

[0004] The present application aims to provide a nitrogen-doped nickel-cobalt bimetallic porous carbon composite material, which improves the electrode material and has higher electrochemical activity, better conductivity, more stable cycle stability and excellent specific capacitance.

[0005] In order to achieve the above-mentioned application purpose, the present application discloses a nitrogen-doped nickel-cobalt bimetallic porous carbon composite material, which is synthesized by using 1,2,4-triazole-3-carboxylic acid as a ligand, through a hydrothermal method to synthesize a precursor, and then calcining at 600 DEG C.

[0006] Further preferably, the molar ratio of nickel to cobalt in the nitrogen-doped nickel-cobalt bimetallic porous carbon composite material is 1:1.

[0007] Meanwhile, the present application also discloses a preparation method of the nitrogen-doped nickel-cobalt bimetallic porous carbon composite material, comprising the following steps:

[0008] S1: adding nickel acetate tetrahydrate, cobalt acetate tetrahydrate and 1,2,4-triazole-3-carboxylic acid into a mixed solution composed of pure water, anhydrous ethanol and N,N-dimethylformamide (DMF), stirring, transferring into a polytetrafluoroethylene-lined reaction kettle, placing into a forced air drying oven, and reacting at 130 DEG C for 36 hours;

[0009] S2: after the reaction is completed, cooling to room temperature, separating, taking the solid, washing, and freeze-drying to obtain the product NiCo-TCA;

[0010] S3: placing the NiCo-TCA obtained in step S2 into a tube furnace, heating to 600 DEG C under a nitrogen atmosphere, and calcining for 2 hours to obtain black powder NC / NiCo.

[0011] Preferably, the molar ratio of the nickel acetate tetrahydrate and the cobalt acetate tetrahydrate is 3:1, 2:1, 1:1, 1:2, 1:3, and most preferably, 1:1.

[0012] Preferably, the volume ratio of pure water, anhydrous ethanol and N,N-dimethylformamide (DMF) in the mixed solution is 2:1:1.

[0013] Further preferably, in step S3, the heating rate is 4℃·min -1 .

[0014] Meanwhile, the application also provides the use of the aforementioned nitrogen-doped nickel-cobalt bimetallic porous carbon composite material in the preparation of a supercapacitor electrode.

[0015] In addition, the application also provides the use of the aforementioned nitrogen-doped nickel-cobalt bimetallic porous carbon composite material in the preparation of an asymmetric supercapacitor.

[0016] The nitrogen-doped nickel-cobalt bimetallic porous carbon composite material prepared by the application has a unique structure, contains abundant redox active sites and excellent electrical conductivity, and has excellent electrochemical performance, especially when the molar ratio of nickel to cobalt is 1:1. According to tests, when the molar ratio of nickel to cobalt in the MOFs synthesis process is 1:1, the specific capacitance of the obtained NC / NiCo1 / 1 can reach 595.76 F g -1 at 1.0 A g -1 -1, and it has good cycle performance, with a specific capacitance retention rate of 92.30% after 3000 cycles, and a specific surface area of 68.87 m 2 g -1 -2. When used as a positive electrode material of a supercapacitor, the asymmetric supercapacitor formed by assembling the NC / NiCo1 / 1 with an AC has an energy density of 24.80 Wh kg -1 when the power density is 825.0 W kg -1 -1, and the capacitance retention rate remains at a high level after 3500 cycles. Moreover, the button cell device assembled from the NC / NiCo1 / 1 / / AC can successfully light up a red light-emitting diode (LED), proving its potential application prospect and practicability. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 are N2 adsorption-desorption isotherms and pore size distribution graphs of different products

[0018] Figure 2 are XRD test result graphs of different products.

[0019] Figure 3 is a TEM test result graph of NC / NiCo1 / 1.

[0020] Figure 4 The graph shows the EDS test results for NC / NiCo1 / 1.

[0021] Figure 5 XPS full spectra of different products.

[0022] Figure 6 The CP curves are for different products at different current densities.

[0023] Figure 7 The CV curves are shown for different products at different scan rates.

[0024] Figure 8 Electrochemical impedance spectroscopy for different products.

[0025] Figure 9 This is a comparison graph of specific capacitance under different current densities. Detailed Implementation

[0026] To better understand this invention, we will further elaborate on it below with reference to specific embodiments.

[0027] Unless otherwise specified, all experimental reagents and instruments used in the following examples are commercially available products.

[0028] Example 1

[0029] Add 0.746 g nickel acetate tetrahydrate (3 mmol), 0.747 g cobalt acetate tetrahydrate (3 mmol), and 0.678 g 1,2,4-triazole-3-carboxylic acid (6 mmol) to a mixed solvent of 20 mL pure water, 10 mL anhydrous ethanol, and 10 mL N,N-dimethylformamide (DMF). Stir for 15 min, transfer to a 100 mL polytetrafluoroethylene-lined reactor, place in a forced-air drying oven, and react at 130 °C for 36 h.

[0030] After the reaction was completed, the mixture was cooled to room temperature and centrifuged to obtain a light purple solid. The solid was washed twice with anhydrous ethanol and twice with pure water, and then freeze-dried for 12 hours to obtain a light purple powder product.

[0031] A certain mass of the purple powder product was weighed into a porcelain boat, then placed in a tube furnace, and heated at a rate of 4°C / min under a nitrogen atmosphere. -1 The temperature was raised to 600℃ and calcined for 2 hours. After cooling to room temperature, black powder NC / NiCo1 / 1 was obtained.

[0032] Example 2

[0033] According to the method disclosed in Example 1, only the molar ratio of Co to Ni is changed, different products are obtained respectively, and the corresponding relationship of the products obtained under different molar ratios is shown in Table 1.

[0034] Table 1:

[0035]

[0036]

[0037] Example 3

[0038] The specific surface and porosity analyzer of Micromeritics ASAP2460 type was used to analyze the specific surface and porosity of the series of products obtained in Example 1-Example 2 (N2 adsorption-desorption test, the sample was placed in a vacuum condition at 120℃ for 5h for degassing activation).

[0039] The results are shown in Table 2 and Figure 1 .

[0040] Table 2:

[0041] NC / NiCo1 / 3 NC / NiCo1 / 2 NC / NiCo1 / 1 NC / NiCo2 / 1 NC / NiCo3 / 1 BET specific surface area (m 2 g -1 )]]> 3.88 3.50 68.87 3.04 34.92 Average pore diameter (nm) 32.02 27.73 16.63 43.48 22.46

[0042] As can be seen from Table 2, the specific surface area of NC / NiCo1 / 1 is the largest, which is 68.87m 2 ·g -1 . At the same time, it can be seen from Figure 1 that the N2 adsorption-desorption isotherm of NC / NiCo is a type IV isotherm, which indicates that there are mesopores in the material, and at the same time, a small H3 type hysteresis loop can be observed in the range of P / P0=0.6-1.0, which indicates that mesopores and macropores coexist, and the pore size distribution diagram also indicates that the pore size of NC / NiCo material is basically distributed in the range of mesopores and macropores.

[0043] The porous structure of the material can improve the transmission of ions in the electrolyte solution, and at the same time increase the reaction area of NiCo / electrolyte, thereby improving the electrochemical performance of the material.

[0044] Example 4

[0045] The series of products obtained in Example 1-Example 2 were tested by using the XRD powder diffractometer of RIGAKU Science Company MiniFlex600 type (Cu, λ=0.15406nm) ; the results are shown in Figure 2 .

[0046] From Figure 2As can be seen from the figure, the five different samples all have obvious characteristic peaks at 44.75°, 52.03° and 76.36°, which correspond to the (111), (200) and (220) planes of Ni (Ni PDF#70-0989, Co PDF#15-0806) respectively. Moreover, as can be seen from the figure, with the increase of the proportion of Co ions in the synthesis of the MOF precursor, the diffraction peak intensity of Co and Ni changes, and the diffraction peak intensity in NC / NiCo1 / 1 is the lowest, the content of Ni is higher than that of Co in NC / NiCo3 / 1 and NC / NiCo2 / 1, and the diffraction peak intensity of these two materials is the highest, indicating that the crystallinity of Co and Ni in these two materials is higher after calcination.

[0047] Example 5

[0048] The NC / NiCo1 / 1 obtained in Example 1 was subjected to TEM test on a Tecnai G2 F30 type transmission electron microscope; the test results are shown in Figure 3 .

[0049] In combination Figure 3 , it can be observed that obvious lattice fringes are present in part a, which correspond to the (200) plane of Ni (0.172 nm), the (111) plane of Co (0.201 nm) and the (200) plane of C (0.277 nm) (Co PDF#15-0816, Ni PDF#70-0989, C PDF#18-0311) respectively, which is consistent with the XRD test results. Meanwhile, the lattice fringes present at 0.234 nm correspond to the (301) plane of Co (Co PDF#70-2633). Figure 3 As can be seen from parts b and c of the figure, the metal nanoparticles are uniformly wrapped in the porous carbon.

[0050] The porous carbon matrix in the material can effectively diffuse the active nano Ni and Co metal particles. These metal nanoparticles store charges through Faraday redox reaction, while the porous carbon as a support material plays an important role in increasing the conductivity and stability of the electrode. The incorporation of heteroatoms can significantly improve the conductivity of the porous carbon, and the successful doping of different types of N into the composite material can provide more free electrons, making the material have higher electron affinity.

[0051] Meanwhile, in combination Figure 4 , it can be seen that 5.69% of N is successfully doped in the obtained composite material NC / NiCo1 / 1, and at the same time, it can be seen that the mass ratio of Co and Ni is 18.98% and 26.19% respectively.

[0052] Example 6

[0053] The product was tested by XPS using a Thermo Fisher Nexsa X-ray photoelectron spectrometer, and the results are shown in Figure 5 .

[0054] Example 7

[0055] The electrochemical performance of the five NC / NiCo materials in the positive voltage range was tested in a three-electrode system, and the test results are shown in Figure 6 It can be seen that a long charge and discharge platform appears in each result, indicating that the specific capacitance of the material is high, and it has obvious Faraday electrochemical behavior. Due to the redox reaction of nano Co, Ni particles in alkaline electrolyte, obvious redox peaks appear in the CV curves shown in Figure 7 , at the same time, the peak current response increases with the increase of the scanning rate, and the CV image shape remains good, indicating that the electrode has ideal rate capability. And from the straight line tilting to the virtual axis in the low frequency region of the EIS image shown in Figure 8 , it can be known that the diffusion resistance of the electrode is low in the redox process. And the equivalent series resistance (R s ) value of all electrodes is very low, which is 0.47-0.50Ω, indicating that the electrode conductivity is good.

[0056] It can be seen from Figure 9 that the bimetallic / mesoporous carbon composite material has very high specific capacitance, especially when the molar ratio of nickel and cobalt is 1:1 during the synthesis of NiCo-TCA, the obtained NC / NiCo1 / 1 composite material has a specific capacitance of 601.05 F g -1 when the current density is 0.5 A g -1 , the specific capacitance is 595.76 F g -1 when the current density is 1.0 A g -1 , and the specific capacitance can still be maintained at 512 F g -1 when the current density rises to 10 A g -1 , which shows that it has good rate performance.

[0057] Further, the cycle performance of NC / NiCo1 / 1 was tested, and the results showed that after 3000 cycles at 3.0 A g -1 , the capacitance retention rate of NC / NiCo1 / 1 could reach 92.30%, indicating that NC / NiCo1 / 1 has excellent cycle stability.

[0058] Example 8

[0059] 6 mol L -1KOH as electrolyte, NC / NiCo1 / 1 as positive material, AC as negative material, and NC / NiCo1 / 1 / / AC was assembled. The specific capacitance, energy density and power density were calculated according to CP curve, and the results were shown in Table 3.

[0060] Table 3:

[0061]

[0062] It can be seen that, as the positive material of asymmetric supercapacitor, the electrochemical performance of asymmetric supercapacitor was obviously improved when NC / NiCo1 / 1 was used as the positive material.

[0063] The above is the specific embodiment of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which are also considered to be within the scope of protection of the present application.

Claims

1. A nitrogen-doped nickel-cobalt bimetallic porous carbon composite material, characterized in that: The nitrogen-doped nickel-cobalt bimetallic porous carbon composite material is obtained by calcining a precursor synthesized by a hydrothermal method with 1,2,4-triazole-3-carboxylic acid as a ligand at 600 DEG C; The molar ratio of nickel to cobalt in the nitrogen-doped nickel-cobalt bimetallic porous carbon composite material is 1:

1. The composite material is 1.0 A g -1 The specific capacitance reaches 595.76 F g -1 After 3000 cycles, the specific capacitance retention rate is 92.30%, and the specific surface area reaches 68.87 m 2 g -1 .

2. The method for preparing the nitrogen-doped nickel-cobalt bimetallic porous carbon composite material of claim 1, characterized in that, The method comprises the following steps: S1: adding nickel acetate tetrahydrate, cobalt acetate tetrahydrate and 1,2,4-triazole-3-carboxylic acid into a mixed solution composed of pure water, anhydrous ethanol and N,N-dimethylformamide (DMF), stirring, transferring into a polytetrafluoroethylene-lined reaction kettle, placing into a forced air drying oven, and reacting at 130 DEG C for 36 hours; S2: after the reaction is completed, cooling to room temperature, separating, taking the solid, washing, and freeze-drying to obtain the product NiCo-TCA; S3: placing the NiCo-TCA obtained in step S2 into a tube furnace, heating to 600 DEG C under a nitrogen atmosphere, and calcining for 2 hours to obtain black powder NC / NiCo.

3. The method of claim 2, wherein: The molar ratio of nickel acetate tetrahydrate to cobalt acetate tetrahydrate is 3:1, 2:1, 1:1, 1:2 or 1:

3.

4. The method of claim 2, wherein: The molar ratio of nickel acetate tetrahydrate to cobalt acetate tetrahydrate is 1:

1.

5. The method of claim 2, wherein: The volume ratio of pure water, anhydrous ethanol and N,N-dimethylformamide (DMF) in the mixed solution is 2:1:

1.

6. The method of claim 2, wherein: In the mixing step S3, the temperature increase rate was 4°C / min -1 .

7. Use of the nitrogen-doped nickel-cobalt bimetallic porous carbon composite material of claim 1 in the preparation of a supercapacitor electrode.

8. Use of the nitrogen-doped nickel-cobalt bimetallic porous carbon composite material of claim 1 in the preparation of an asymmetric supercapacitor.

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