CN112002561A

CN112002561A - Carbon-containing iron oxide/iron nitride mixture and preparation method and application thereof

Info

Publication number: CN112002561A
Application number: CN202010826662.XA
Authority: CN
Inventors: 王赛尔; 吴华; 苏良湖; 张卫东; 张龙江; 纪荣婷; 陈苏娟; 刘臣炜; 陈梅; 刘茹
Original assignee: Nanjing Agricultural University; Nanjing Institute of Environmental Sciences MEE
Current assignee: Nanjing Agricultural University; Nanjing Institute of Environmental Sciences MEE
Priority date: 2020-08-17
Filing date: 2020-08-17
Publication date: 2020-11-27
Anticipated expiration: 2040-08-17
Also published as: CN112002561B

Abstract

The invention discloses a carbon-containing iron oxide/iron nitride mixture and a preparation method and application thereof. The preparation method is characterized by insulating an imidazole derivative polybasic aromatic carboxylate iron complex for 1.5-3 h at 800-900 ℃ in an inert gas atmosphere to obtain black powder. The carbon-containing iron oxide/iron nitride mixture can be used as a cathode material of a super capacitor and has application prospects in the field of electrochemical energy storage. The material and the imidazole derivative polybasic aromatic carboxylate iron complex can be respectively used as a cathode electrode material and an anode electrode material of a super capacitor, and the assembled asymmetric super capacitor has the characteristics of high capacitance, repeated recycling and low resistance.

Description

Carbon-containing iron oxide/iron nitride mixture and preparation method and application thereof

Technical Field

The invention relates to the field of electrode materials of supercapacitors, in particular to a carbon-containing iron oxide/iron nitride mixture and a preparation method and application thereof.

Background

In view of the rapid increase of energy consumption in the modern world and the huge pressure of greenhouse gas emission reduction, the traditional energy sources cannot meet the ever-increasing demands of human beings more and more. Compared with fossil fuels, electrochemical energy is receiving attention due to its characteristics of high power density, environmental friendliness, high economic efficiency, and the like. As a rapidly growing electrochemical energy storage device, a supercapacitor can be charged and discharged at an ultra-fast speed and has an extremely high efficiency, thereby making it widely used in many fields (smart grid, urban rail transit, military equipment, etc.). Supercapacitors can be classified into Electric Double Layer Capacitors (EDLCs) and Pseudocapacitors (PCs) according to the energy storage mechanism of the electrode material. In comparison with EDLCs, the capacitance of PC generally comes from a redox reaction at or near the surface of an electrode material, and PC generally has a high capacitance, but has disadvantages such as low power density and poor stability. The performance of PC depends to a large extent on the electrode material, so developing new electrode materials and controlling the structure and interface characteristics of the materials are key to increasing the specific capacitance, rate capability and cycling stability of supercapacitors.

In the research of novel electrode materials, many electrode materials having excellent electrochemical properties, such as Metal Organic Framework (MOF), MXenes, Metal Nitride (MN), and Covalent Organic Framework (COF), have appeared. Since Yaghi reported MOFs for the first time in 1995, it was discovered that MOFs have diverse structures, high porosity and adjustable chemical composition, and have been one of the hot spots in many fields. MOFs can provide a single atomic active center, which can not only reduce metal loss, but can also increase the electrode/electrolyte interface. Since MOFs were first used as electrode materials for supercapacitors, MOFs based on transition metals Co, Ni and Mn were widely studied as electrode materials. However, these metals have the disadvantages of high price, limited natural reserves and toxic waste streams.

Disclosure of Invention

In order to solve the problems, the invention provides a carbon-containing iron oxide/iron nitride mixture which can be used as a negative electrode material of a super capacitor and has potential application value. Wherein, the metal center iron has the characteristics of abundant reserves, low cost, environmental protection and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

a carbon-containing iron oxide/nitride mixture prepared by the following method:

keeping the imidazole derivative polybasic aromatic carboxylate iron complex at 800-900 ℃ for 1.5-3 h in an inert gas atmosphere to obtain black powder, namely a carbon-containing ferric oxide/ferric nitride mixture;

the imidazole derivative polybasic aromatic carboxylate iron complex has the following structural formula:

preferably, the inert gas is nitrogen.

The chemical name of the imidazole derivative polybasic aromatic carboxylate iron complex is 1, 2-tri (4-imidazolyl phenyl) amine-4, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid iron monohydrate.

Said imidazole derivative is a polyThe iron complex of the aromatic carboxylate has a two-dimensional layered structure, the crystal of the complex belongs to a monoclinic system, the space group is C2/C, and the unit cell parameters are as follows:

α＝90°β＝90.39°γ＝90°，

3. has a one-dimensional chain structure in the crystal and can be expanded to have a three-dimensional topological interpenetrating network structure.

The preparation method of the imidazole derivative polybasic aromatic carboxylate iron complex comprises the following steps:

in a mixed solvent of water and an organic solvent, uniformly mixing tris (4-imidazolyl phenyl) amine, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid and an Fe (II) source, then filling the mixture into a reaction kettle for hydrothermal reaction, and then cooling and crystallizing to obtain the compound. The crystals obtained were red in color.

Preferably, the preparation method further comprises the steps of filtering, washing and drying the crystals.

Preferably, the hydrothermal reaction is carried out at 100-130 ℃ for 72-96 h.

Preferably, the source of fe (ii) is iron sulphate.

Preferably, the organic solvent is N, N-dimethylformamide.

Preferably, the molar ratio of 2-tris (4-imidazolylphenyl) amine to 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris-trimellitic acid to Fe (II) in the source is 0.5-2.5: 0.5-2: 1-4.

Preferably, the volume ratio of the water to the organic solvent is 1: 2-5.

Preferably, the crystallization time is 3-4 days.

Preferably, the temperature reduction is carried out at 10 ℃ h^-1Cooling to 100 deg.C, and cooling to room temperature.

Preferably, the tris (4-imidazolyl phenyl) amine is prepared by the following method:

reacting 4-bromotriphenylamine, sodium hydroxide, imidazole, potassium carbonate, copper oxide and dimethyl sulfoxide at 170 ℃ for 24-48 hours.

Preferably, the method for producing tris (4-imidazolylphenyl) amine further comprises the steps of adding methanol after the reaction, dissolving with stirring, filtering, and slowly adding the filtrate until hot water is precipitated. The tris (4-imidazolylphenyl) amine is obtained as a yellow solid.

Preferably, in the method for producing a tris (4-imidazolylphenyl) amine: the molar ratio of the sodium hydroxide to the 4-nitroimidazole to the 1, 2-dibromoethane is 1-2.5: 1.5-3: 0.8-1.5.

The invention also provides application of the imidazole derivative polybasic aromatic carboxylate iron complex in preparation of a positive electrode material of a super capacitor.

Further, the cathode material for preparing the supercapacitor comprises: uniformly coating the imidazole derivative polybasic aromatic carboxylate iron complex powder on the surface of foamed nickel.

The imidazole derivative polybasic aromatic carboxylate iron complex is subjected to crystal X-ray diffraction, infrared spectrum characterization and electrochemical test. The imidazole derivative polybasic aromatic carboxylate iron complex is used as an active material to prepare a foamed nickel electrode, and the foamed nickel electrode is tested in a three-electrode system to observe whether the foamed nickel electrode has potential for preparing a supercapacitor electrode material. The results are as follows: the material presents the characteristics of pseudo capacitance in cyclic voltammetry test and constant current charge and discharge test, and shows that the essence of the electrochemical characteristics of the material is derived from the redox reaction of Fe ions.

The current density of the material is 1.0, 2.0, 4.0, 6.0, 8.0 and 10.0 A.g^-1The specific capacitances are 818.40, 682.44, 571.21, 502.79, 456, 422F g^-1The specific capacitance is higher.

The carbon-containing iron oxide/nitride mixture was subjected to powder X-ray diffraction, infrared spectroscopy characterization, and electrochemical testing. The nickel oxide is used as an active material to prepare a foamed nickel electrode, and is measured under a three-electrode system, and whether the nickel oxide has the potential of being prepared into a supercapacitor electrode material is observed. The results are as follows: the material presents the characteristics of pseudo capacitance in cyclic voltammetry test and constant current charge and discharge test, and shows that the essence of the electrochemical characteristics of the material is derived from the redox reaction of Fe ions.

The current density of the material is 1.0, 2.0, 4.0, 6.0, 8.0 and 10.0 A.g^-1When the specific capacitance is 377.48, 341.11, 307.64, 285.81, 267.62, 255.45 and F.g^-1The specific capacitance is higher.

The imidazole derivative polybasic aromatic carboxylate iron complex and the carbon-containing iron oxide/iron nitride mixture are respectively used as positive and negative active materials to assemble an asymmetric supercapacitor, the working voltage range of the asymmetric supercapacitor is 0-1.6V, the mass ratio of the positive and negative active materials is 1:3.3, and electrochemical tests are carried out on the asymmetric supercapacitor. The results are as follows: the super capacitor shows the characteristics of pseudo capacitance in cyclic voltammetry test and constant current charge and discharge test, and shows that the capacitance is from the oxidation-reduction reaction of positive and negative electrode materials.

The energy transmission efficiency of the super capacitor is higher than 80% under each current density, and is 4 A.g^-1The maximum energy transmission efficiency can reach 93% under the current density, and the excellent energy transmission capability is shown.

The equivalent series resistance of the super capacitor is 0.7 omega, which shows that the equivalent series resistance of the device is very small and has good ion response.

After 5000 GCD tests, the capacity retention rate of the super capacitor is 90.6%, and the device has excellent cycle stability.

The invention has the beneficial effects that:

the imidazole derivative polybasic aromatic carboxylate iron complex and the carbon-containing iron oxide/iron nitride mixture derived from the imidazole derivative polybasic aromatic carboxylate iron complex have good oxidation-reduction property and potential capability of becoming a super capacitor electrode material. With the continuous progress and rapid development of chemical material technology, the method not only provides development opportunities for novel material engineering and novel material synthesis, but also has great significance in the aspects of improving energy efficiency, reducing manufacturing cost, advocating energy conservation and emission reduction, creating an environment-friendly society and the like. The method obtains the complex through a simple synthesis route, the complex has high yield and purity, and can be directly used as the anode electrode material of the super capacitor, the carbon-containing ferric oxide/ferric nitride mixture derived from the complex can be directly used as the cathode material of the super capacitor, and the super capacitor assembled by the complex and the carbon-containing ferric oxide/ferric nitride mixture has the characteristics of high capacitance, repeated recycling and low resistance in the aspect of electrochemical energy storage.

Most of the super capacitors on the market are electric double layer capacitors, and under the condition of the same electrode area, the pseudocapacitance can reach 10-100 times of the electric double layer capacitance. The complex material is used as a positive electrode material and is 1 A.g^-1When the specific capacitance reaches 824.6F g^-1And the theoretical capacitance of the graphite material on the market is only 372F g^-1. When the carbon-containing iron oxide/iron nitride mixture material is used as a negative electrode material, the concentration is 2 A.g^-1When the specific capacitance reaches 341.1F g^-1The current relatively new porous iron oxycarbide material is 2A g^-1When the specific capacitance is 114.5 F.g^-1. The two materials both get a breakthrough in specific capacitance, and after the asymmetric super capacitor is assembled, the capacitor has the advantages of large capacitance, low internal resistance, repeated recycling and the like, and the maximum energy density can reach 45.5 Wh.kg^-1The energy density of the super capacitor which is relatively good in the market at present is only 30 Wh/kg^-1。

Drawings

FIG. 1 is a unit cell structure diagram of an imidazole derivative polybasic aromatic carboxylic acid salt iron complex.

FIG. 2 is a 1D linear structural diagram of an iron complex of imidazole derivative polyaromatic carboxylate according to the present invention.

FIG. 3 is a 3D network structure of the imidazole derivative poly aromatic carboxylate iron complex of the present invention.

FIG. 4 shows the topological structure of the iron complex of imidazole derivative poly aromatic carboxylate.

FIG. 5 shows a double-insertion structure of an imidazole derivative iron complex of a polybasic aromatic carboxylate according to the present invention.

FIG. 6 is an infrared spectrum of an imidazole derivative iron (III) salt of a polybasic aromatic carboxylic acid of the present invention and a carbon-containing iron oxide/iron nitride mixture of the present invention.

FIG. 7 is a PXRD pattern of the imidazole derivative polybasic aromatic carboxylic acid salt iron complex of the present invention and the carbon-containing iron oxide/iron nitride mixture of the present invention.

FIG. 8 is a cyclic voltammogram of the imidazole derivative polyaromatic carboxylate iron complex of the present invention at different sweep rates in a three-electrode system.

FIG. 9 is a constant current charge-discharge curve of the imidazole derivative poly aromatic carboxylate iron complex under different current densities of a three-electrode system.

FIG. 10 is a plot of cyclic voltammetry curves for carbon-containing iron oxide/nitride mixtures of the present invention at different scan rates in a three-electrode system.

FIG. 11 is a graph showing the charge and discharge curves of the carbonaceous iron oxide/iron nitride mixture of the present invention for different current densities in a three-electrode system.

FIG. 12 is a graph showing the relationship between the specific capacitance of the imidazole derivative poly aromatic carboxylate iron complex and the carbon-containing iron oxide/iron nitride mixture according to the present invention and the current density of a three-electrode system.

FIG. 13 is a schematic diagram of the operating voltage range of an asymmetric supercapacitor assembled by the imidazole derivative poly aromatic carboxylate iron complex and the carbon-containing iron oxide/iron nitride mixture according to the present invention.

FIG. 14 is a cyclic voltammogram of an asymmetric supercapacitor of the invention at different scan rates.

FIG. 15 is a graph showing the charging and discharging curves of the asymmetric supercapacitor according to the present invention at different current densities.

FIG. 16 is a graph showing the specific capacitance of an asymmetric supercapacitor according to the present invention as a function of current density at different current densities.

FIG. 17 is a graph of the energy transfer efficiency variation for different current densities for an asymmetric ultracapacitor according to the present invention.

FIG. 18 is a graph of the AC impedance of the asymmetric ultracapacitor of the present invention.

FIG. 19 is a graph of capacitance retention for 5000 cycles of testing of an asymmetric supercapacitor according to the invention.

FIG. 20 is a PXRD spectrum of a carbon-containing iron oxide/iron nitride mixture according to the present invention.

FIG. 21 EDXmapping scheme of iron complex of imidazole derivative polyaromatic carboxylate according to the present invention.

FIG. 22 is an EDXmapping chart for a carbon-containing iron oxide/nitride mixture according to the present invention.

FIG. 23 is a scanning electron microscope image of the imidazole derivative polybasic aromatic carboxylic acid salt iron complex.

FIG. 24 is a scanning electron micrograph of a carbon-containing iron oxide/iron nitride mixture according to the present invention.

Fig. 25 is a ramon diagram of an asymmetric ultracapacitor of the present invention.

FIG. 26 is an XPS spectrum of an iron complex of an imidazole derivative polyaromatic carboxylate according to the present invention.

FIG. 27 is an XPS spectrum of a carbon-containing iron oxide/nitride mixture according to the invention.

Detailed Description

Example 1

(1) Preparation of tris (4-imidazolylphenyl) amine:

firstly reacting 4-bromotriphenylamine, sodium hydroxide, imidazole, potassium carbonate, copper oxide and dimethyl sulfoxide at 170 ℃ for 30 hours, adding 125mL of methanol, stirring for dissolving, filtering, collecting filtrate, slowly adding the filtrate into 1L of hot water, and filtering and drying precipitated yellow solid to obtain the tri (4-imidazolyl phenyl) amine.

Wherein the molar ratio of the sodium hydroxide to the 4-nitroimidazole to the potassium carbonate to the copper oxide to the dimethyl sulfoxide is 2:1: 1.

(2) Preparation of imidazole derivative iron complex of aromatic polycarboxylic acid salt: in a mixed solvent of water and N, N-dimethylformamide (volume ratio is 1:3), tris (4-imidazolyl phenyl) amine, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid and FeSO₄Uniformly mixing the sources according to the molar ratio of 1:1:2, putting the mixture into a reaction kettle, carrying out hydrothermal reaction at 120 ℃ for 72 hours, and then carrying out hydrothermal reaction at 10 ℃ for h^-1And cooling to 100 ℃, then cooling to room temperature for crystallization for 3d, and then sequentially filtering, washing and drying crystals obtained by cooling crystallization to obtain red crystals of the imidazole derivative-poly aromatic carboxylate iron complex.

(3) Preparing a working electrode: firstly, a whole block of foamed nickel is cut into 5cm multiplied by 1cmSize, put into 3 mol. L^-1Taking out, washing with water to remove residual acid, ultrasonic treating for 30min, ultrasonic treating with ethanol for 30min, and air drying.

75mg of the crystal material obtained in the step (2) is mixed with 15mg of acetylene black and ground for 20min to be fine, 10mg of PTFE is added for grinding for 10min, and then the mixture is transferred to a small glass bottle filled with 4mL of isopropanol solution for magnetic stirring for 24 h. Accurately weighing the foam nickel electrode cut before and weighing the foam nickel electrode, and recording the obtained mass as m₁The stirred sample slurry is dipped by a brush and evenly smeared on the foamed nickel to form a square area of 1cm multiplied by 1cm, and the square area is dried for 3 hours at the temperature of 60 ℃. The dried electrode is pressed into a tablet by 10.0Mpa, then accurately weighed, and the mass is recorded as m₂. The effective mass of the active material of the obtained working electrode is (m)₂-m₁) X 75% g, active substance ratio is about 2-4mg cm^-2. Then placing the foamed nickel in 6 mol.L^-1And soaking in KOH solution for 24h to obtain the working electrode.

The chemical name of the prepared imidazole derivative polybasic aromatic carboxylate iron complex is 1, 2-tri (4-imidazolyl phenyl) amine-4, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid iron monohydrate.

The imidazole derivative polybasic aromatic carboxylate iron complex has a two-dimensional layered structure, the complex crystal belongs to a monoclinic system, the space group is C2/C, and the unit cell parameters are as follows:

α＝90°β＝90.39°γ＝90°，

3. has a one-dimensional chain structure in the crystal and can be expanded to have a three-dimensional topological interpenetrating network structure. The crystallographic parameters are shown in table 1:

TABLE 1 crystallographic parameters of iron complexes of imidazole derivatives polyaromatic carboxylates

The bond length and bond angle data of the imidazole derivative poly aromatic carboxylate iron complex are shown in Table 2:

TABLE 2 bond Length and Angle Table of iron Complex of imidazole derivative polyaromatic carboxylates

Fe(1)-O(6)^#1	2.0371(16)	O(1)-Fe(1)-N(10)^#2	88.79(7)
				Fe(1)-O(1)	2.0651(14)	O(6)^#1-Fe(1)-N(4)	94.94(8)
Fe(1)-N(10)^#2	2.1371(19)	O(1)-Fe(1)-N(4)	87.27(7)
				Fe(1)-N(4)	2.154(2)	N(10)^#2-Fe(1)-N(4)	175.53(8)
Fe(1)-O(1W)	2.1914(17)	O(6)^#1-Fe(1)-O(1W)	89.65(7)
				Fe(1)-N(8)^#3	2.208(2)	O(1)-Fe(1)-O(1W)	91.69(7)
O(6)^#1-Fe(1)-O(1)	177.36(7)	N(10)^#2-Fe(1)-O(1W)	89.16(8)
				O(6)^#1-Fe(1)-N(10)^#2	88.96(8)	N(4)-Fe(1)-O(1W)	93.05(8)
O(6)^#1-Fe(1)-N(8)^#3	84.29(8)	O(1)-Fe(1)-N(8)^#3	94.45(7)
				N(10)^#2-Fe(1)-N(8)^#3	93.04(8)	N(4)-Fe(1)-N(8)^#3	85.18(8)
O(1W)-Fe(1)-N(8)^#3	173.51(7)

Symmetric transform codes for generating equivalent atoms:^#1x+1/2,-y+1/2,z+1/2；^#2x-1/2,-y+1/2,z+1/2；^#3x-1/2,y+1/2,z；^#4x+1/2,-y+1/2,z-1/2；^#5x+1/2,y-1/2,z；^#6x-1/2,-y+1/2,z-1/2.

the complex of the invention belongs to a monoclinic system C2/C space group according to the single crystal X-ray diffraction structure determination. Each asymmetric unit comprises a TATB^3-Ligand, a TIPA ligand, a crystallographically independent Fe^IIIA center (as in fig. 1). Each Fe^IIIThe centers are all hexa-coordinated and respectively derived from two TATBs^3-Two oxygens of the anion, coordinated to three nitrogen atoms from three TIPA ligands and to the oxygen in one water molecule, represent distorted octahedral FeO₃N₃Coordination geometry. Wherein Fe1 is in contact with O1 and O6^#1、O1W、N10^#5、N8^#3Coordinated with N4, the Fe-O distance is in the range

And the Fe-N distance is

In the meantime. Each Fe center passing through TATB^3-The ligands are connected to form a long Fe-TATB-Fe chain, and the 1D linear structure of the compound is formed (shown in figure 2). TIPA ligands in different directions are connected with adjacent Fe centers to form a 3D structure, and Fe-TATB-Fe long chains are inserted into the structure to finally form a 3D network structure of the compound (as shown in figure 3). By topological analysis, considering the Fe center as the 5 connection point, the N in the middle of the TIPA as the 3 connection point, and simplifying the TIPA connection line, the complex of the invention can be regarded as a 3, 5-connected topological structure (as shown in FIG. 4), which

The symbol is 5 for

N

²6, 5 for Fe center³·6³·7³9. The two equivalent topologies interdigitate to form a dual interpenetrating 3D network of the complex of the present invention (see fig. 5).

FIG. 21 is an EDXmapping chart of the prepared complex, and four elements are uniformly distributed.

FIG. 23 is an SEM image of the resulting complex, containing particles ranging in size from 200nm to 2 μm, some of which are spherical and 2 μm in the form of bulk particles.

FIG. 26 is an XPS spectrum of the complex obtained in the present invention.

In the spectrum of Fe2p, two main peaks respectively located at 711.1eV (Fe2 p)_3/2) And 724.8eV (Fe2 p)_1/2) Of Iron (III) atom Fe³⁺Coordination bonds to N or O. Meanwhile, the presence of a coordinate bond was confirmed by the O1s peak appearing at 529.55eV and the N1s peak appearing at 400.69 eV. The other two O1s peaks in the complex of the invention are respectively positioned at 531.37 and 533.07eV, and are in contact with ligand TATB^3-The carboxyl moiety of (a) has a C ═ O bond and a C-O bond. The N1s peak at 398.67eV is associated with the nitrogen-containing ligand in the complexes of the present invention. In the C1s spectrum, four peaks appear at binding energies of 283.99eV (C-C), 285.64eV (C-N), 287.48eV (C-O) and 291.87eV (π - π transition).

Adopting a three-electrode system, taking Pt wires as a counter electrode and Hg/HgO as a reference electrode, adopting the working electrode prepared in the step (3), and adopting 6 mol.L of electrolyte^-1KOH, electrochemical performance tests were performed using Cyclic Voltammetry (CV), constant current charging and discharging (GCD), alternating current impedance (EIS), and cyclic performance tests.

FIG. 8 shows that the complex of the invention has 2-50 mV.s under a three-electrode system^-1Cyclic Voltammograms (CVs) at different sweep rates. A pair of obvious redox peaks exist in CV curves, which are the marks of pseudo capacitance, and indicate that the capacitance is derived from the pseudo capacitance generated by the Faraday redox reaction of the electrodes and is mainly attributed to the metal center Fe^II-Fe^IIIChange in valence state therebetween. With the increase of the sweeping speed, the oxidation reduction peaks respectively shift to the anode and the cathode, which shows the irreversibility of dynamics in the reaction process.

FIG. 9 shows a three-electrode system of the complex of the present inventionThe following 1-10 A.g^-1The constant current charge-discharge curve (GCD) under different current densities is not a standard triangle, but an obvious discharge platform appears between 0.3 and 0.4V, and the consistency with the CV curve indicates that the capacitance behavior of the complex is pseudo capacitance, and the capacitance comes from the oxidation-reduction reaction of the electrode.

Example 2

(1) Preparation of tris (4-imidazolylphenyl) amine:

firstly reacting 4-bromotriphenylamine, sodium hydroxide, imidazole, potassium carbonate, copper oxide and dimethyl sulfoxide at 170 ℃ for 48 hours, adding 125mL of methanol, stirring for dissolving, filtering, collecting filtrate, slowly adding the filtrate into 1L of hot water, and filtering and drying precipitated yellow solid to obtain the tri (4-imidazolyl phenyl) amine.

Wherein the molar ratio of the sodium hydroxide to the 4-nitroimidazole to the potassium carbonate to the copper oxide to the dimethyl sulfoxide is 1:1.5: 0.8.

(2) Preparation of imidazole derivative iron complex of aromatic polycarboxylic acid salt: in a mixed solvent of water and N, N-dimethylformamide (volume ratio is 1:5), tris (4-imidazolyl phenyl) amine, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid and FeSO₄Uniformly mixing the sources according to the molar ratio of 0.5:2:1, putting the mixture into a reaction kettle, carrying out hydrothermal reaction at 100 ℃ for 96 hours, and then carrying out hydrothermal reaction at 10 ℃ for h^-1And cooling to 100 ℃, then cooling to room temperature for crystallization for 4d, and then sequentially filtering, washing and drying crystals obtained by cooling crystallization to obtain red crystals of the imidazole derivative-poly aromatic carboxylate iron complex.

(3) And (3) preserving the red crystal obtained in the step (2) for 3 hours at 800 ℃ in a nitrogen atmosphere to obtain black powder, namely the carbon-containing ferric oxide/ferric nitride mixture.

(4) Preparing a working electrode: firstly, a whole block of foamed nickel is cut into the size of 5cm multiplied by 1cm, and then the foamed nickel is put into a container with the volume of 3 mol.L^-1Taking out, washing with water to remove residual acid, ultrasonic treating for 30min, ultrasonic treating with ethanol for 30min, and air drying.

Mixing 75mg of the material obtained in the step (3) with 15mg of acetylene black, grinding for 20min to be fine, adding 10mg of PTFE, grinding for 10min, and transferring to a containerA small glass vial of 4mL isopropanol solution was magnetically stirred for 24 h. Accurately weighing the foam nickel electrode cut before and weighing the foam nickel electrode, and recording the obtained mass as m₁The stirred sample slurry is dipped by a brush and evenly smeared on the foamed nickel to form a square area of 1cm multiplied by 1cm, and the square area is dried for 3 hours at the temperature of 60 ℃. The dried electrode is pressed into a tablet by 10.0Mpa, then accurately weighed, and the mass is recorded as m₂. The effective mass of the active material of the obtained working electrode is (m)₂-m₁) X 75% g, active substance ratio is about 2-4mg cm^-2. Then placing the foamed nickel in 6 mol.L^-1And soaking in KOH solution for 24h to obtain the working electrode.

And (4) performing infrared spectrum characterization on the materials obtained in the steps (2) and (3). FIG. 6 is an infrared spectrum of a complex of the present invention and a carbon-containing iron oxide/iron nitride mixture of the present invention. At 3438cm^-1The peak at (b) corresponds to the stretching vibration of O-H in the carboxyl group. 3114cm^-1The absorption peak at (A) is attributed to C-H stretching vibration of the aromatic ring. 2920 and 2846cm^-1The double peak at (a) corresponds to the stretching vibration of the methylene group. 1818cm^-1The peak at (b) corresponds to stretching vibration of C ═ O in the carboxyl group. 1689 to 1282cm^-1The peaks in between pertain to the backbone vibration of the aromatic rings as well as the triazine rings. At 930 to 856cm^-1The absorption peak in between belongs to out-of-plane deformation vibration of the aromatic ring. Infrared characterization shows that the complex of the invention has an organic ligand characteristic peak, which proves the successful synthesis of the material. As for the carbon-containing iron oxide/iron nitride mixture, no organic framework peak was observed in the infrared image, indicating that the ligand was removed by calcination.

FIG. 7 is a PXRD pattern for a complex of the present invention and a carbon-containing iron oxide/iron nitride mixture of the present invention. Compared with the PXRD pattern obtained by actual test, the PXRD pattern of the complex obtained by simulating single crystal X-ray data by using the Mercury program is high in coincidence degree with the test diffraction pattern based on the single crystal structure, and the purity is high. The PXRD pattern of the carbon-containing iron oxide/iron nitride mixture is greatly changed compared with that of the complex of the invention.

FIG. 20 shows a carbon-containing iron oxide/nitride mixture according to the present inventionPXRD spectrum of (1) and diffraction peaks can be assigned to Fe₂O₃And Fe₃Different phases of N indicate that not only incomplete carbonization processes but also oxidation and nitridation processes to different degrees are present during calcination.

FIG. 22 is an EDXmapping chart of a carbonaceous iron oxide/iron nitride mixture of the present invention with a significant increase in Fe element content and a significant decrease in C, N and O elements after calcination.

FIG. 24 is an SEM image of a carbonaceous iron oxide/iron nitride mixture of the present invention having bulk particle sizes varying from 100nm to 1 μm. Compared with the complex, the surface of the carbon-containing iron oxide/iron nitride mixture is rougher, and a plurality of 50nm pores appear after calcination, so that the specific surface area is successfully increased, the rapid transmission of electrons is facilitated, and the conductivity of the material is enhanced.

In comparison with the XPS spectrum of the complex of the invention (FIG. 26), Fe2p is clearly evident in the XPS spectrum of the iron oxide/nitride mixture of the invention₃The characteristic peak in N appeared at 706.8eV, demonstrating that Fe was produced after calcination₃N, which is also consistent with the structure of XRD. Meanwhile, in the N1s spectrum, the pyridine-N peak has been shifted to a lower binding energy of 397.57eV at 398.67eV, which is also in contrast to Fe₃The presence of N is relevant. The 399.98eV peak associated with the Fe-N bond is still observed in the spectrum of N1s, which indicates that the Fe-N bond is retained after high temperature calcination, which helps to improve the stability of the structure. The other two N1s peaks were assigned to graphitized-N (402.17eV) and oxidized-N (404.68 eV). From the O1s spectrum, it was found that the intensity of the Fe — O peak increased, while the intensity of the C ═ O peak and the intensity of C — O decreased, indicating that the content of Fe element increased and the content of O element decreased after high-temperature calcination, which is also consistent with the EDX results. The shift of the O1s peak overall to lower binding energy corresponds to the oxidation to Fe occurring during calcination₂O₃. Combining the N1s spectrum and the C1s spectrum, it was found that the nitrogen-doped carbon skeleton remained after calcination, which was beneficial to enrichment of conjugated electrons and further improvement of conductivity.

The prepared electrode was subjected to electrochemical performance tests using the three-electrode system of example 1, namely Cyclic Voltammetry (CV), constant current charging and discharging (GCD), alternating current impedance (EIS) and cyclic performance tests.

FIG. 10 shows the carbon-containing iron oxide/iron nitride mixture of the present invention at 2-50 mV. s in a three-electrode system^-1The CV curves with different sweep rates have a pair of obvious redox peaks in the CV curves with the voltage windows of-1.2-0V, which are the marks of pseudo capacitance and indicate that the capacitance is derived from the pseudo capacitance generated by the Faraday redox reaction of the electrode and is mainly due to metallic Fe^II-Fe^IIIChange in valence state therebetween. With the increase of the sweeping speed, the redox peaks respectively shift to the anode and the cathode, and obvious polarization phenomenon appears at-1.1V, which indicates the irreversibility of dynamics in the reaction process.

FIG. 11 shows that the carbon-containing iron oxide/iron nitride mixture of the present invention is in the range of 1-10A g in a three-electrode system^-1The GCD curve is not a standard triangle but a long discharge platform between-0.8 and-0.6V under the constant current charge-discharge curves of different current densities, which is probably related to organic functional groups remained on the surface after pyrolysis, and the correspondence with the CV curve indicates the pseudocapacitance performance of the electrode, and the capacitance is derived from the oxidation-reduction reaction of the electrode.

And (3) preparing the complex material obtained in the step (2) into an electrode by adopting the same method as the step (4), and testing by adopting the three-electrode system in the example 1. The complex and the carbon-containing iron oxide/iron nitride mixture were analyzed in comparison.

FIG. 12 is a graph of the specific capacitance of the complex of the present invention and the carbon-containing iron oxide/iron nitride mixture of the present invention calculated according to the GCD curve as a function of current density, with the gradual increase in current density and the interaction of the electrolyte and the active material, the gradual decrease in capacitance between the two, where 1A g^-1The specific capacitances of the inventive complexes and the inventive carbon-containing iron oxide/iron nitride mixtures are 824.6, 376.1 Fg, respectively, at current densities^-1。

Example 3

(1) Preparation of tris (4-imidazolylphenyl) amine:

firstly reacting 4-bromotriphenylamine, sodium hydroxide, imidazole, potassium carbonate, copper oxide and dimethyl sulfoxide at 170 ℃ for 24 hours, adding 125mL of methanol, stirring for dissolving, filtering, collecting filtrate, slowly adding the filtrate into 1L of hot water, and filtering and drying precipitated yellow solid to obtain the tri (4-imidazolyl phenyl) amine.

Wherein the molar ratio of the sodium hydroxide to the 4-nitroimidazole to the potassium carbonate to the copper oxide to the dimethyl sulfoxide is 2.5:3: 1.5.

(2) Preparation of imidazole derivative iron complex of aromatic polycarboxylic acid salt: in a mixed solvent of water and N, N-dimethylformamide (volume ratio is 1:2), tris (4-imidazolyl phenyl) amine, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid and FeSO₄Uniformly mixing the sources according to the molar ratio of 2.5:0.5:4, putting the mixture into a reaction kettle, carrying out hydrothermal reaction at 130 ℃ for 72h, and then carrying out hydrothermal reaction at 10 ℃ for h^-1And cooling to 100 ℃, then cooling to room temperature for crystallization for 4d, and then sequentially filtering, washing and drying crystals obtained by cooling crystallization to obtain red crystals of the imidazole derivative-poly aromatic carboxylate iron complex.

(3) And (3) preserving the heat of the red crystal obtained in the step (2) for 1.5h at 900 ℃ in a nitrogen atmosphere to obtain black powder, namely the carbon-containing iron oxide/iron nitride mixture.

And (3) respectively mixing 75mg of the complex material obtained in the step (2) and 75mg of the carbon-containing iron oxide/iron nitride mixture material obtained in the step (3) with 15mg of acetylene black, grinding for 20min to be fine, adding 10mg of PTFE, grinding for 10min, and transferring to a small glass bottle filled with 4mL of isopropanol solution to carry out magnetic stirring for 24 h. Accurately weighing the foam nickel electrode cut before and weighing the foam nickel electrode, and recording the obtained mass as m₁The stirred sample slurry is dipped by a brush and evenly smeared on the foamed nickel to form a square area of 1cm multiplied by 1cm, and the square area is dried for 3 hours at the temperature of 60 ℃. The dried electrode was pressed under 10.0MPa and accurately weighed, and the mass was recorded asm₂. The effective mass of the active material of the obtained working electrode is (m)₂-m₁) X 75% g, active substance ratio is about 2-4mg cm^-2. Then placing the foamed nickel in 6 mol.L^-1And soaking in KOH solution for 24h to obtain the working electrode. The working electrode made of the complex material is a positive electrode, and the working electrode made of the carbon-containing iron oxide/iron nitride mixture is a negative electrode.

The positive and negative electrodes were assembled into an asymmetric supercapacitor and tested.

FIG. 13 is a schematic representation of the operating voltage range of an asymmetric supercapacitor assembled from a complex of the present invention and a carbon-containing iron oxide/iron nitride mixture of the present invention. And determining that the working voltage range of the super capacitor is 0-1.6V by combining the CV curve and the GCD curve of the two under the three-electrode system, and the mass ratio of the positive active substance to the negative active substance is 1:3.3 respectively.

FIG. 14 is a CV curve of a supercapacitor of the present invention showing a pair of distinct redox peaks indicating that the device is a pseudocapacitive capacitor, the capacitance resulting from the redox reaction at the electrodes when swept from 2 mV. s^-1Increase to 50mV · s^-1The CV curve is not deformed, which shows that the rate capability of the device is good.

Figure 15 is a GCD curve for a supercapacitor of the invention, neither the charge nor discharge curve of the device is a standard triangle, indicating its pseudocapacitive behavior.

FIG. 16 is the relation between the specific capacitance of the super capacitor according to the present invention calculated from the GCD curve and the current density, the electrolyte and the active material interact with each other with the increasing current density, the capacitance gradually decreases at 1,2, 4,6, 8, 10 A.g^-1At a current density, the capacitance was 128.1, 115.13, 101.9975, 93.5, 80, 73.1F g^-1。

FIG. 17 shows the energy transfer efficiency η% (η ═ T) of the ultracapacitor of the present invention_d/T_cX 100% where T_dIs the discharge time, T_cIs charging time). The energy transmission efficiency of the device is higher than 80% at each current density, and is 4 A.g^-1The highest energy transmission efficiency can reach 93 percent under the current density, and the performance is shownExcellent energy transfer capability.

FIG. 18 is an AC impedance spectrum of a supercapacitor according to the present invention. The intercept of the curve and the horizontal axis represents that the equivalent series resistance of the asymmetric super capacitor is 0.7 omega, which shows that the equivalent series resistance of the device is very small and has good ion response.

FIG. 19 shows the voltage at 4 A.g of the supercapacitor of the present invention^-1And the capacity retention rate chart of 5000 times of cyclic charge and discharge under current density is that after 5000 times of GCD test, the capacity retention rate is 90.6%, and the device has excellent cyclic stability.

FIG. 25 is a Ragong diagram of the super capacitor of the present invention, which reflects the relationship between energy density and power density when the current density is 1 A.g^-1When the energy density of the device is 45.5 Wh/kg at most^-1At this time, the power density was 800 W.kg^-1And when the current density is increased to 10A g^-1When the energy density is 26 Wh/kg^-1The power density is 8000W/kg^-1. When the power density is from 800 W.kg^-1Increased to 8000W/kg^-1And the energy density is small in rising amplitude, so that the super capacitor can be rapidly charged and discharged under high power.

Claims

1. A carbon-containing iron oxide/nitride mixture, characterized by being prepared by the following method:

2. the carbon-containing iron oxide/nitride mixture of claim 1, wherein the imidazole derivative polyaromatic carboxylate iron complex is prepared by:

in a mixed solvent of water and an organic solvent, uniformly mixing tris (4-imidazolyl phenyl) amine, 4' - (1,3, 5-triazine-2, 4, 6-triyl) tri-trimellitic acid and an Fe (II) source, then filling the mixture into a reaction kettle for hydrothermal reaction, and then cooling and crystallizing to obtain the compound.

3. The carbon-containing iron oxide/nitride mixture according to claim 2, wherein the hydrothermal reaction is carried out at 100 to 130 ℃ for 72 to 96 hours.

4. The carbon-containing iron oxide/nitride mixture of claim 2, wherein the source of Fe (II) is ferrous sulfate.

5. The carbon-containing iron oxide/nitride mixture of claim 2, wherein the organic solvent is N, N-dimethylformamide.

6. The carbon-containing iron oxide/nitride mixture of claim 2, wherein the molar ratio of 2-tris (4-imidazolylphenyl) amine, 4',4 "- (1,3, 5-triazine-2, 4, 6-triyl) tris-trimellitic acid, and Fe in the Fe (ii) source is 0.5-2.5: 0.5-2: 1-4.

7. The carbonaceous iron oxide/nitride mixture of claim 2 wherein the temperature reduction is at 10 ° h^-1Cooling to 100 deg.C, and cooling to room temperature.

8. The carbon-containing iron oxide/nitride mixture of claim 2, wherein the tris (4-imidazolylphenyl) amine is prepared by:

9. The carbon-containing iron oxide/nitride mixture of claim 8, wherein in the process for preparing tris (4-imidazolylphenyl) amine: the molar ratio of the sodium hydroxide to the 4-nitroimidazole to the 1, 2-dibromoethane is 1-2.5: 1.5-3: 0.8-1.5.

10. Use of the carbonaceous iron oxide/iron nitride mixture of claim 1 in the preparation of a negative electrode material for a supercapacitor.