CN114360923A - A kind of preparation method of nickel oxide composite electrode material - Google Patents

Abstract

In order to solve the problem of low capacity of nickel oxide in the prior art, the present invention provides a preparation method of nickel oxide composite electrode material, the preparation method comprises the following steps: preparation of graphite oxide, reduction of graphite oxide to prepare graphene, nickel oxide Preparation of composite materials, post-processing of nickel oxide composite materials. The present invention proposes for the first time that high-reduction and high-defective graphene is used to modify nickel oxide, and the nickel oxide composite material can be rapidly heat-treated under microwave conditions by utilizing the high-reduction and high-defective graphene's ability to absorb and convert into heat by strong microwaves. The electrical conductivity of the nickel oxide is improved, and the low-consumption and high-efficiency heat treatment of the nickel oxide composite material is realized, and the nickel oxide composite electrode material with high electrochemical activity is prepared.

Description

A kind of preparation method of nickel oxide composite electrode material

technical field

The invention relates to the field of electrode materials, in particular to a preparation method of a nickel oxide composite electrode material.

Background technique

With the rapid growth of the world's demand for new energy technologies, the demand for new energy devices with large capacity, high power, high energy density and long service life, such as supercapacitors and lithium batteries, is also growing. The key to realizing these new energies of new energy devices lies in the energy storage capacity of electrode materials. Therefore, designing and obtaining high-capacity electrode materials has become the focus of current new energy device development.

Among them, nickel oxide has been widely developed for supercapacitors and batteries due to its high theoretical energy storage capacity. However, although nickel oxide possesses high theoretical capacity, it is difficult to obtain high capacity in practical application, thus limiting its further application in practice.

In order to obtain nickel oxide, after decades of development, a variety of effective methods have been developed for the preparation of nickel oxide, such as hydrothermal method, solvothermal method, high temperature pyrolysis method, etc. Through these methods, nickel oxide materials with different morphologies, different scales and different dimensions have been successfully obtained. At the same time, a variety of post-processing technologies have also been developed for the performance optimization and improvement of nickel oxide materials. Therefore, nickel oxide-based materials with different energy storage properties were obtained.

Patent CN103943379A A kind of preparation method of graphene-loaded flower-shaped porous nickel oxide composite material, its typical feature is that the nickel oxide sheet is assembled into the composite of flower-shaped structure and graphene sheet, and as the matrix skeleton graphene has good conductivity, The nickel oxide microspheres can be loaded on graphene sheets to achieve their good electrical conductivity and improve the apparent electrical conductivity of the composites. The capacitance obtained for this composite at a current density of 200 mA/g was a maximum of 413 F/g.

Patent CN103632857A The preparation method of nickel oxide/reduced graphene oxide nanosheet composite material, the invention takes multi-walled carbon nanotubes (WMCNTs) as raw material, adopts Hummer method to oxidize to obtain graphite oxide nanosheets with lamellar structure and easily dispersed ( CNGO); then the graphite oxide nanosheets (CNGO) and Ni(NO3)2·6H2O were ultrasonically dispersed in ethanol solvent, and solvothermally reacted at 140～180℃ for 10～12h; after cooling to room temperature, filtered, water, anhydrous Ethanol washing and vacuum drying to obtain a precursor composite material; then, the precursor composite material is heat-treated at 200-250° C. for 3-5 hours in an air atmosphere to obtain a nickel oxide/reduced graphene oxide nanocomposite material. The charge-discharge test was carried out with a specific current of 1A/g, and the test result: the specific capacitance value was 714-1010F/g.

It can be seen that the specific capacity of the nickel oxide composite electrodes prepared by the prior art is far lower than the theoretical value (<1500F/g), and some methods have complicated operations and high equipment requirements. Therefore, how to obtain nickel oxide materials with high specific capacity is still a key technical problem that needs to be solved urgently.

SUMMARY OF THE INVENTION

In order to solve the problem of low capacity of the nickel oxide composite electrode in the prior art, the present invention provides a preparation method of the nickel oxide composite electrode material, so as to obtain the nickel oxide composite electrode with high capacity.

The object of the present invention is achieved through such technical scheme, a kind of preparation method of nickel oxide composite electrode material, comprises the following steps:

S1, the preparation of graphite oxide: using flake graphite as precursor, through chemical exfoliation method, prepare graphite oxide, standby;

S2. Graphene is prepared by reduction of graphite oxide: take graphite oxide, carry out reduction treatment to it, obtain graphene, and reserve;

S3, the preparation of nickel oxide composite material: get graphene, urea, nickel chloride (NiCl ₂ ·6H ₂ O) and disperse in water, and prepare nickel oxide/graphene composite material by hydrothermal reaction, and it is standby;

S4, post-processing of the nickel oxide composite material: take the nickel oxide/graphene composite material and carry out microwave treatment to prepare the nickel oxide composite electrode material.

Wherein, the chemical exfoliation method in the step S1 includes Hummers method, Standenmaier method, and Brodie method, and graphite oxide or graphene oxide is prepared by oxidizing flake graphite.

Wherein, the oxygen atom content of the graphite oxide prepared in the step S1 is 25-30 at.%.

Wherein, the reduction treatment in the step S2 includes flame method, flame method+microwave method, and graphite oxide or graphene oxide is reduced to obtain graphene with high degree of reduction and high degree of defect.

Wherein, in the flame method + microwave method in the step S2, the microwave treatment time is 3-9 s.

Wherein, the oxygen atom content of the graphene prepared in the step S2 is 3.1-12 at.%.

Wherein, in the step S3, the mass ratio of graphene, urea and NiCl ₂ ·6H ₂ O is 1:4:4.

Wherein, the time of the hydrothermal reaction in the step S3 is 4-12h; the temperature of the hydrothermal reaction is 140-180°C.

Wherein, in the step S4, the time of the microwave treatment is 3-15s; the power of the microwave treatment is 600-1200W.

The invention proposes for the first time that high reduction degree and high defect degree graphene is used to modify nickel oxide, and the nickel oxide composite material can be uniformly and rapidly heat treated under microwave conditions by utilizing the high reduction degree and high defect degree graphene's ability to absorb and convert into heat by strong microwave. A large number of defects formed in graphene significantly change the electronic structure of graphene, which can enhance the interaction between graphene and nickel oxide on the one hand, and on the other hand, it can change the ability of graphene to absorb microwaves and convert it into heat, and at the same time, it can also be used as electricity. The active site of a chemical reaction. On the one hand, the high reduction of graphene is conducive to enabling graphene to obtain a strong ability to absorb microwaves and convert it into heat, and on the other hand, it is conducive to enabling graphene to obtain strong thermal conductivity, so that the heat converted into microwave absorption can be transferred to oxidation in time. Nickel, realizes the rapid heat treatment of nickel oxide, and at the same time, the high reduction of graphene makes it have high conductivity, which can effectively improve the conductivity of nickel oxide. In addition, the high reduction of graphene also prevents the weakening of the interaction between nickel oxide and graphene due to the gas released by the decomposition of oxygen-containing functional groups on the graphene surface during microwave treatment. Therefore, this strategy not only greatly improves the conductivity of nickel oxide, but also realizes the low-cost and high-efficiency heat treatment of the nickel oxide composite material, so as to obtain a highly active nickel oxide composite electrode material. This method is simple, low-consumption, and high-efficiency, and can be used for large-scale processing and optimization of nickel oxide materials, and can also be used for conductivity enhancement and heat treatment of other materials. The preparation process of graphite oxide, the reduction process of graphite oxide, the hydrothermal reaction process, and the microwave treatment process are all simple and easy to operate.

The invention greatly improves the capacity of the nickel oxide electrode material, solves the problems existing in the existing method for constructing the nickel oxide electrode material, the prepared product has good conductivity and high activity, and is used for supercapacitors with high specific capacitance, and the highest yield is close to theoretical The obtained material has the following advantages: ①The specific capacitance is super high, 1500～2500F/g; ②The conductivity is good, and the charge transfer resistance is 0.5～1.5Ω.

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) figure of the graphene of high reduction degree and high defect degree prepared by embodiment 1;

Fig. 2 is the X-ray photoelectron spectroscopy (XPS) figure of the graphene with high degree of reduction and high defectivity prepared in Example 1;

Fig. 3 is the SEM image of the nickel oxide composite electrode material after microwave treatment prepared in Example 1;

Fig. 4 is the SEM image of graphene oxide prepared by Comparative Example 1;

Fig. 5 is the XPS figure of the graphite oxide prepared by comparative example 1;

Fig. 6 is the SEM image of the nickel oxide composite electrode material after microwave treatment prepared in Comparative Example 1;

Fig. 7 is the SEM image of the nickel oxide composite electrode material after microwave treatment prepared in Comparative Example 2;

FIG. 8 is a constant current charge-discharge curve (GCD) diagram of the nickel oxide composite electrode material before microwave treatment prepared in Example 1 at a current density of 1 A/g;

9 is a GCD diagram of the microwave-treated nickel oxide composite electrode material prepared in Example 1 at a current density of 1A/g;

10 is the GCD diagram of the nickel oxide composite electrode material before microwave treatment prepared in Comparative Example 1 at a current density of 1 A/g;

11 is a GCD diagram of the microwave-treated nickel oxide composite electrode material prepared in Comparative Example 1 at a current density of 1 A/g;

12 is a GCD diagram of the nickel oxide composite electrode material before microwave treatment prepared in Comparative Example 2 at a current density of 1 A/g;

13 is a GCD diagram of the microwave-treated nickel oxide composite electrode material prepared in Comparative Example 2 at a current density of 1 A/g;

Figure 14 is a comparison chart of the specific capacitance of the nickel oxide composite electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

15 is an electrochemical impedance spectroscopy (EIS) diagram of the nickel oxide composite electrode material after microwave treatment prepared in Example 1;

16 is the EIS diagram of the nickel oxide composite electrode material after microwave treatment prepared in Comparative Example 1;

17 is an EIS diagram of the nickel oxide composite electrode material after microwave treatment prepared in Comparative Example 2.

Detailed ways

The following examples are used to further illustrate the present invention, but the present invention is not limited thereto, and the raw materials, reagents and equipment used are all obtained through commercial purchase. The experimental methods that do not specify specific conditions in the following examples are selected according to conventional methods and conditions, or according to the product description.

Example 1

In the first step, graphite oxide is prepared by the Hummers method in the chemical exfoliation method:

Weigh 1g of flake graphite and 0.5g of sodium nitrate and place it in the round-bottomed flask of 250mL, measure 23mL of vitriol oil with a concentration of 98% by weight and add it to this round-bottomed flask, add a magnet, and place this round-bottomed flask in the round-bottomed flask. In an ice-water bath, stir for 30min, weigh 3g potassium permanganate and add it to the reactor, continue stirring for 1h, after the reaction is completed, transfer the reactor to a water bath at 35°C, continue stirring for 30min, measure 50mL of Distilled water was added to the round-bottomed flask, then the round-bottomed flask was transferred to an oil bath at 98°C, stirring was continued for 15 min, 140 mL of distilled water and 10 mL of H ₂ O ₂ with a mass fraction of 30% were added in sequence, and the reaction system was finally formed. After bright yellow, centrifuge, and then wash with 500 mL of hydrochloric acid with a mass fraction of 5% HCl and distilled water successively until the solution becomes neutral to obtain graphite oxide (oxygen atom content is 25～30 at.%), standby;

In the second step, graphene oxide is reduced to prepare graphene:

The above-mentioned graphite oxide is loaded on the surface of the watch glass, and dried to form a graphite oxide film with a thickness of 0.05mm. Weigh 0.05g of the above-mentioned graphite oxide film, use tweezers to pick up the graphite oxide film, and quickly approach the outer flame of an alcohol lamp for 1s. The film is rapidly reduced to black pre-reduced graphene oxide (oxygen atom content is 8-12 at. %), which is ready for use.

Weigh 0.05g of above-mentioned pre-reduced graphene oxide and place it in a 100mL beaker, place the beaker in a 1000W constant power household microwave oven and microwave for 3s to obtain graphene (oxygen atom content is 3.1～4at.%), for subsequent use;

The third step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphene and place it in a 100 mL beaker, add 40 mL of deionized water, after ultrasonic treatment for 30 min, add 40 mg of urea, 40 mg of NiCl ₂ 6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor , and reacted at 140°C for 8h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The fourth step, post-processing of the nickel oxide composite material:

0.05 g of the nickel oxide composite material prepared in the third step was weighed and placed in a 100 mL beaker, and the beaker was microwaved for 6 s in a 1000 W household microwave oven with constant power to obtain the final nickel oxide composite material.

Example 2

In the first step, graphite oxide is prepared by the Standenmaier method in the chemical exfoliation method:

Measure 17.5mL of concentrated sulfuric acid and 9mL of concentrated nitric acid in a 250mL flask, stir for 15min; weigh 1g of graphite and slowly add it to the flask; after stirring, add 11g of potassium chlorate, react for 96h; wash with 800mL of distilled water, and then use Washing with 5% dilute hydrochloric acid, and finally washing with distilled water to neutrality to obtain graphite oxide (oxygen atom content is 25-30 at.%), for subsequent use;

In the second step, graphene oxide is reduced to prepare graphene:

The above-mentioned graphite oxide is loaded on the surface of the watch glass, and dried to form a graphite oxide film with a thickness of 0.05mm. Weigh 0.05g of the above-mentioned graphite oxide film, use tweezers to pick up the graphite oxide film, and quickly approach the outer flame of an alcohol lamp for 1s. The film is rapidly reduced to black pre-reduced graphene oxide (oxygen atom content is 8-12 at. %), which is ready for use.

Weigh 0.05g of above-mentioned pre-reduced graphene oxide and place it in a 100mL beaker, place the beaker in a 1000W constant power household microwave oven and microwave for 9s to obtain graphene (oxygen atom content is 3.5～4.5at.%), for subsequent use;

The third step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphene and place it in a 100 mL beaker, add 40 mL of deionized water, after ultrasonic treatment for 30 min, add 40 mg of urea, 40 mg of NiCl ₂ 6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor , and reacted at 180°C for 4h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The fourth step, post-processing of the nickel oxide composite material:

0.05 g of the nickel oxide composite material prepared in the third step was weighed and placed in a 100 mL beaker, and the beaker was placed in a 1200W constant power household microwave oven for microwave treatment for 3 s to obtain the final nickel oxide composite material.

Example 3

In the first step, graphite oxide is prepared by the Hummers method in the chemical exfoliation method:

Weigh 1g of flake graphite and 0.5g of sodium nitrate and place it in the round-bottomed flask of 250mL, measure 23mL of vitriol oil with a concentration of 98% by weight and add it to this round-bottomed flask, add a magnet, and place this round-bottomed flask in the round-bottomed flask. In an ice-water bath, stir for 30min, weigh 3g potassium permanganate and add it to the reactor, continue stirring for 1h, after the reaction is completed, transfer the reactor to a water bath at 35°C, continue stirring for 30min, measure 50mL of Distilled water was added to the round-bottomed flask, then the round-bottomed flask was transferred to an oil bath at 98°C, stirring was continued for 15 min, 140 mL of distilled water and 10 mL of H ₂ O ₂ with a mass fraction of 30% were added in sequence, and the reaction system was finally formed. After bright yellow, centrifuge, and then wash with 500 mL of hydrochloric acid with a mass fraction of 5% HCl and distilled water successively until the solution becomes neutral to obtain graphite oxide (oxygen atom content is 25～30 at.%), standby;

In the second step, graphene oxide is reduced to prepare graphene:

The above-mentioned graphite oxide is loaded on the surface of the watch glass, and dried to form a graphite oxide film with a thickness of 0.05mm. Weigh 0.05g of the above-mentioned graphite oxide film, use tweezers to pick up the graphite oxide film, and quickly approach the outer flame of an alcohol lamp for 1s. The film is rapidly reduced to black graphene (oxygen atom content is 8-12 at.%), ready for use;

The third step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphene and place it in a 100 mL beaker, add 40 mL of deionized water, after ultrasonic treatment for 30 min, add 40 mg of urea, 40 mg of NiCl ₂ 6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor , and reacted at 160°C for 12h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The fourth step, post-processing of the nickel oxide composite material:

0.05 g of the nickel oxide composite material prepared in the third step was weighed and placed in a 100 mL beaker, and the beaker was placed in a 600W constant-power household microwave oven for microwave treatment for 15 s to obtain the final nickel oxide composite material.

Example 4

In the first step, graphite oxide is prepared by the Brodie method in the chemical exfoliation method:

Weigh 2 g of graphite powder and add it to 3 mL of concentrated sulfuric acid containing 3 g of K ₂ S ₂ O ₈ and 3 g of P ₂ O ₅ , heat at 80 °C for 6 h, then cool to room temperature, dilute with distilled water, wash until neutral, and dry to obtain For the pre-oxidized graphite oxide, 1 g of the obtained pre-oxidized graphite was weighed and added to 46 mL of concentrated sulfuric acid. Under ice-water bath conditions, 3 g of potassium permanganate was added, and the reaction was carried out at 35 °C for 2 h. After the reaction, add 46mL distilled water, then slowly add 280mL distilled water and 5mL30% hydrogen peroxide, centrifuge while hot, and wash to neutrality with 500mL 5% dilute hydrochloric acid and a large amount of distilled water at last, and the obtained graphite oxide (oxygen atom content is 25～30at.%), spare;

In the second step, graphene oxide is reduced to prepare graphene:

The above-mentioned graphite oxide is loaded on the surface of the watch glass, and dried to form a graphite oxide film with a thickness of 0.05mm. Weigh 0.05g of the above-mentioned graphite oxide film, use tweezers to pick up the graphite oxide film, and quickly approach the outer flame of an alcohol lamp for 1s. The film is rapidly reduced to black pre-reduced graphene oxide (oxygen atom content is 8-12 at. %), which is ready for use.

Weigh 0.05g of the above-mentioned pre-reduced graphene oxide and place it in a 100mL beaker, place the beaker in a 1000W constant power household microwave oven and microwave for 6s to obtain graphene (oxygen atom content is 4.5～5.5at.%), for subsequent use;

The third step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphene and place it in a 100 mL beaker, add 40 mL of deionized water, after ultrasonic treatment for 30 min, add 40 mg of urea, 40 mg of NiCl ₂ 6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor , and reacted at 150°C for 10h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The fourth step, post-processing of the nickel oxide composite material:

Weigh 0.05 g of the nickel oxide composite material prepared in the third step into a 100 mL beaker, and place the beaker in a 900 W constant-power household microwave oven for microwave treatment for 8 s to obtain the final nickel oxide composite material.

Example 5

In the first step, graphite oxide is prepared by the Hummers method in the chemical exfoliation method:

Weigh 1g of flake graphite and 0.5g of sodium nitrate and place it in the round-bottomed flask of 250mL, measure 23mL of vitriol oil with a concentration of 98% by weight and add it to this round-bottomed flask, add a magnet, and place this round-bottomed flask in the round-bottomed flask. In an ice-water bath, stir for 30min, weigh 3g potassium permanganate and add it to the reactor, continue stirring for 1h, after the reaction is completed, transfer the reactor to a water bath at 35°C, continue stirring for 30min, measure 50mL of Distilled water was added to the round-bottomed flask, then the round-bottomed flask was transferred to an oil bath at 98°C, stirring was continued for 15 min, 140 mL of distilled water and 10 mL of H ₂ O ₂ with a mass fraction of 30% were added in sequence, and the reaction system was finally formed. After bright yellow, centrifuge, and then wash with 500 mL of hydrochloric acid with a mass fraction of 5% HCl and distilled water successively until the solution becomes neutral to obtain graphite oxide (oxygen atom content is 25～30 at.%), standby;

In the second step, graphene oxide is reduced to prepare graphene:

The above-mentioned graphite oxide is loaded on the surface of the watch glass, and dried to form a graphite oxide film with a thickness of 0.05mm. Weigh 0.05g of the above-mentioned graphite oxide film, use tweezers to pick up the graphite oxide film, and quickly approach the outer flame of an alcohol lamp for 1s. The film is rapidly reduced to black pre-reduced graphene oxide (oxygen atom content is 8-12 at. %), which is ready for use.

Weigh 0.05g of above-mentioned pre-reduced graphene oxide and place it in a 100mL beaker, place the beaker in a 1000W constant power household microwave oven and microwave for 4s to obtain graphene (oxygen atom content is 3.2～4.1 at.%), for subsequent use;

The third step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphene and place it in a 100 mL beaker, add 40 mL of deionized water, after ultrasonic treatment for 30 min, add 40 mg of urea, 40 mg of NiCl ₂ 6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor , and reacted at 170°C for 6h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The fourth step, post-processing of the nickel oxide composite material:

0.05 g of the nickel oxide composite material prepared in the third step was weighed and placed in a 100 mL beaker, and the beaker was microwaved for 12 s in an 800 W constant-power household microwave oven to obtain the final nickel oxide composite material.

Comparative Example 1

In the first step, graphite oxide is prepared by the Hummers method in the chemical exfoliation method:

Weigh 1g of flake graphite and 0.5g of sodium nitrate and place it in the round-bottomed flask of 250mL, measure 23mL of vitriol oil with a concentration of 98% by weight and add it to the round-bottomed flask, add a magnet, and place the round-bottomed flask in the round-bottomed flask. In an ice-water bath, stir for 30 min, weigh 3 g of potassium permanganate into the reactor, and continue to stir for 1 h. After the reaction is completed, transfer the reactor to a water bath at 35 °C, continue stirring for 30 min, and measure 50 mL of Distilled water was added to the round-bottomed flask, then the round-bottomed flask was transferred to an oil bath at 98°C, stirring was continued for 15 min, and 140 mL of distilled water and 10 mL of H ₂ O ₂ with a mass fraction of 30% were added in sequence, and the reaction system was finally formed. After bright yellow, centrifuge, and then wash with 500 mL of hydrochloric acid with a mass fraction of 5% HCl and distilled water successively until the solution becomes neutral to obtain graphite oxide (oxygen atom content is 25～30 at.%), for subsequent use;

The second step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphite oxide and place it in a 100 mL beaker, add 40 mL of deionized water, and after ultrasonic treatment for 30 min, add 40 mg of urea and 40 mg of NiCl ₂ ·6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor. , and reacted at 140°C for 8h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The third step, post-processing of the nickel oxide composite material:

0.05 g of the nickel oxide composite material prepared in the third step was weighed and placed in a 100 mL beaker, and the beaker was microwaved for 6 s in a 1000 W household microwave oven with constant power to obtain the final nickel oxide composite material.

Comparative Example 2

In the first step, graphite oxide is prepared by the Hummers method in the chemical exfoliation method:

Weigh 1g of flake graphite and 0.5g of sodium nitrate and place it in the round-bottomed flask of 250mL, measure 23mL of vitriol oil with a concentration of 98% by weight and add it to this round-bottomed flask, add a magnet, and place this round-bottomed flask in the round-bottomed flask. In an ice-water bath, stir for 30min, weigh 3g potassium permanganate and add it to the reactor, continue stirring for 1h, after the reaction is completed, transfer the reactor to a water bath at 35°C, continue stirring for 30min, measure 50mL of Distilled water was added to the round-bottomed flask, then the round-bottomed flask was transferred to an oil bath at 98°C, stirring was continued for 15 min, 140 mL of distilled water and 10 mL of H ₂ O ₂ with a mass fraction of 30% were added in sequence, and the reaction system was finally formed. After bright yellow, centrifuge, and then wash with 500 mL of hydrochloric acid with a mass fraction of 5% HCl and distilled water successively until the solution becomes neutral to obtain graphite oxide (oxygen atom content is 25～30 at.%), standby;

The second step, the preparation of nickel oxide composite material:

Weigh 10 mg of graphite oxide and place it in a 100 mL beaker, add 40 mL of deionized water, and after ultrasonic treatment for 30 min, add 40 mg of urea and 40 mg of NiCl ₂ ·6H ₂ O, continue to ultrasonicate for 15 min, and then transfer the mixed solution to a 50 mL hydrothermal reactor. , and reacted at 220°C for 8h. The obtained product was washed with deionized water and ethanol for 5 times, and then dried in an oven at 50° C. for 24 hours to obtain a nickel oxide composite material, which was used for later use;

The third step, post-processing of the nickel oxide composite material:

0.05 g of the nickel oxide composite material prepared in the third step was weighed and placed in a 100 mL beaker, and the beaker was placed in a 1000W constant power household microwave oven for microwave treatment for 6s to obtain the final nickel oxide composite material.

Embodiment effect

(1) The nickel oxide composite electrode materials prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were respectively tested for specific capacitance and charge transfer impedance, and the results are listed in Table 1.

(2) The assembly method of the working electrode in the three-electrode system is as follows: 2 mg of the nickel oxide composite electrode materials prepared in Examples 1 to 5 and Comparative Examples 1 and 2 are evenly loaded in the middle of two pieces of foamed nickel, and at 8 Mpa The working electrode was made by pressing for 10 min under the same pressure.

(3) The counter electrode used in the three-electrode system is a platinum sheet electrode, the reference electrode used is a saturated calomel electrode, the electrolyte solution used is a 2mol/L KOH aqueous solution, and the test equipment is Shanghai Chenhua 660E electrochemical workstation. The charge transfer impedance was obtained by the electrochemical impedance spectroscopy module (ACImpedance) in Shanghai Chenhua 660E electrochemical workstation. The specific capacitance (C _s ) is tested by the constant current charge-discharge module (Chronopotentiometry) in Shanghai Chenhua 660E electrochemical workstation, and calculated by the formula C _s =It/mΔv, where I, t, m, and v represent the discharge current respectively (A), discharge time (s), active material mass (g), potential difference (V).

Table 1

sample Charge transfer resistance (Ω) Specific capacitance (F/g) Example 1 0.5～1 2300～2500 Example 2 0.5～1 2100～2300 Example 3 1～1.5 1500～1700 Example 4 0.5～1 2200～2400 Example 5 0.5～1 1900～2100 Comparative Example 1 9.5～11.5 750～850 Comparative Example 2 7～8.5 400～500

Now in conjunction with accompanying drawing, embodiment and comparative example are further described:

Fig. 1 is the SEM image of the graphene with high reduction degree and high defect degree prepared in Example 1; Fig. 2 is the XPS image of graphene with high reduction degree and high defect degree prepared in Example 1; Fig. 3 is the microwave treatment prepared in Example 1 SEM image of the nickel oxide composite electrode material after. It can be seen from FIG. 1 that the graphene with high reduction degree and high defectivity prepared in Example 1 exhibits a wrinkled film-like structure, indicating that graphene has been successfully prepared. It can be seen from Figure 2 that the oxygen content of the graphene with high degree of reduction and high defectivity prepared in Example 1 is very low, and it is found by quantitative analysis that the oxygen content is only 3.5 at.%, indicating that a high degree of reduction is obtained after reduction treatment. of graphene. It can be seen from FIG. 3 that the nickel oxide composite electrode material prepared in Example 1 exhibits a sheet-like structure.

Fig. 4 is the SEM image of graphene oxide prepared by Comparative Example 1; Fig. 5 is the XPS image of the graphite oxide prepared by Comparative Example 1; Fig. 6 is the microwave-treated nickel oxide composite electrode material prepared by Comparative Example 1. SEM image. It can be seen from FIG. 4 that the graphene oxide prepared by Comparative Example 1 has a wrinkled film-like structure, and an obvious discharge phenomenon occurs due to poor electrical conductivity. It can be seen from FIG. 5 that the graphene oxide prepared by Comparative Example 1 contains a large amount of oxygen, and it is found by quantitative analysis that the oxygen content is 28.3 at.%. It can be seen from FIG. 6 that the nickel oxide composite electrode material prepared by Comparative Example 1 also exhibits a sheet-like structure.

7 is a SEM image of the nickel oxide composite electrode material prepared in Comparative Example 2 after microwave treatment. It can be seen from FIG. 7 that the nickel oxide composite electrode material prepared in Comparative Example 2 also exhibits a sheet-like structure.

Fig. 8 is the constant current charge-discharge curve (GCD) diagram of the nickel oxide composite electrode material before microwave treatment prepared in Example 1; Fig. 9 is the GCD diagram of the nickel oxide composite electrode material after microwave treatment prepared in Example 1 . Comparing Figure 8 and Figure 9, it can be seen that the charge and discharge time of the nickel oxide composite electrode material prepared after microwave treatment is significantly longer than that of the nickel oxide composite electrode material before microwave treatment, indicating that after microwave treatment, the electrochemical activity of the nickel oxide composite electrode material It is significantly improved, and a nickel oxide composite electrode material with high specific capacitance is obtained, which indicates that the use of graphene modified with high reduction degree and high defect degree to modify nickel oxide and then microwave treatment can effectively improve the electrochemical activity of nickel oxide composite material.

10 is the GCD diagram of the nickel oxide composite electrode material prepared in Comparative Example 1 before microwave treatment; FIG. 11 is the GCD diagram of the nickel oxide composite electrode material prepared in Comparative Example 1 after microwave treatment. Comparing Figure 10 and Figure 11, it can be seen that the discharge time of the nickel oxide composite electrode material prepared after microwave treatment is shorter than that of the nickel oxide composite electrode material before microwave treatment, indicating that after microwave treatment, the electrochemical activity of the nickel oxide composite electrode material is weakened. The specific capacitance of the prepared nickel oxide composite electrode material is small, which indicates that the use of graphene oxide to modify nickel oxide by hydrothermal reaction and then microwave treatment is not conducive to obtaining highly active nickel oxide composite material

FIG. 12 is the GCD diagram of the nickel oxide composite electrode material prepared in Comparative Example 2 before microwave treatment; FIG. 13 is the GCD diagram of the nickel oxide composite electrode material prepared in Comparative Example 2 after microwave treatment. Comparing Figure 12 and Figure 13, it can be seen that the discharge time of the nickel oxide composite electrode material prepared after microwave treatment is significantly longer than that of the nickel oxide composite electrode material before microwave treatment, indicating that after microwave treatment, the electrochemical activity of the nickel oxide composite electrode material is obtained. Significantly improved, and a nickel oxide composite electrode material with high specific capacitance was obtained.

It can be seen from Example 1, Comparative Example 1, and Comparative Example 2 that since Example 1 and Comparative Example 2 can make graphene oxide achieve a higher degree of reduction, it is not only conducive to the conversion of microwave absorption into heat, but also can be avoided. Due to the side effect of gas generated by the decomposition of oxygen-containing functional groups in graphene, a higher active nickel oxide composite electrode material is obtained after microwave treatment. At the same time, since Example 1 obtained graphene with high reduction degree and high defectivity, it can absorb microwaves more effectively and improve the activity of nickel oxide, so that the nickel oxide composite electrode material obtains the highest electrochemical activity.

Figure 14 is a comparison chart of the specific capacitance of the nickel oxide composite electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2, A is the specific capacitance of the nickel oxide composite electrode material prepared in Comparative Example 1 after microwave treatment, B is the specific capacitance of the microwave-treated nickel oxide composite electrode material prepared in Example 2, and C is the specific capacitance of the microwave-treated nickel oxide composite electrode material prepared in Example 1. It can be seen from FIG. 14 that the specific capacitance of the nickel oxide composite electrode material prepared in Example 1 is significantly higher than that of the nickel oxide composite electrode materials prepared in Comparative Example 1 and Comparative Example 2.

FIG. 15 is the EIS diagram of the nickel oxide composite electrode material after microwave treatment prepared in Example 1; FIG. 16 is the EIS diagram of the microwave-treated nickel oxide composite electrode material prepared in Comparative Example 1; FIG. 17 is a comparative example EIS diagram of the nickel oxide composite electrode material after microwave treatment prepared in Example 2. It can be seen from Figure 15 that the EIS diagram of the microwave-treated nickel oxide composite electrode material prepared in Example 1 presents a negligible semicircle in the high-frequency region, indicating that its charge transfer resistance is small and the charge transfer ability is strong, which is beneficial to Nickel oxide undergoes charge exchange, resulting in high electrochemical activity. It can be seen from Figure 16 and Figure 17 that the EIS diagrams of the microwave-treated nickel oxide composite electrode materials prepared in Comparative Example 1 and Comparative Example 2 show a very obvious semicircle in the high frequency region, indicating that the nickel oxide composite electrode material is obtained. The electrode material has large charge transfer resistance and weak charge transfer ability, which is not conducive to the charge exchange of nickel oxide, so that high electrochemical activity cannot be obtained.

It can be seen from the above detection results and the accompanying drawings that the nickel oxide composite electrode material prepared by the present invention has high activity, high specific capacitance and good electrical conductivity, and has great promotion value.

It should be understood that the examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the teaching content of the present invention, those skilled in the art can make any various changes and modifications to the present invention, and these equivalent forms are also limited by the appended claims of the present application.

Claims (9)

1. a preparation method of nickel oxide composite electrode material, is characterized in that, comprises the following steps: S1, the preparation of graphite oxide: using flake graphite as precursor, through chemical exfoliation method, prepare graphite oxide, standby; S2, graphene oxide is reduced to prepare graphene: take graphite oxide, carry out reduction treatment to it, obtain graphene, and reserve; S3, the preparation of nickel oxide composite material: get graphene, urea, nickel chloride (NiCl ₂ ·6H ₂ O) and disperse in water, and prepare nickel oxide/graphene composite material by hydrothermal reaction, and it is standby; S4, post-processing of the nickel oxide composite material: take the nickel oxide/graphene composite material and carry out microwave treatment to prepare the nickel oxide composite electrode material. 2. the preparation method of nickel oxide composite electrode material according to claim 1, is characterized in that, in described step S1, chemical peeling method comprises Hummers method, Standenmaier method, Brodie method, prepares graphite oxide or graphite oxide by flake graphite oxidation ene. 3 . The method for preparing a nickel oxide composite electrode material according to claim 2 , wherein the oxygen atom content of the graphite oxide prepared in the step S1 is 25-30 at. %. 4 . 4. the preparation method of nickel oxide composite electrode material according to claim 1, is characterized in that, in described step S2, reduction treatment comprises flame method, flame method+microwave method, and graphite oxide or graphene oxide is reduced to obtain high reduction Highly defective graphene. 5 . The method for preparing a nickel oxide composite electrode material according to claim 4 , wherein, in the flame method+microwave method in the step S2 , the microwave treatment time is 3-9 s. 6 . 6 . The method for preparing a nickel oxide composite electrode material according to claim 4 , wherein the graphene prepared in the step S2 has an oxygen atom content of 3.1-12 at. %. 7 . 7 . The method for preparing a nickel hydroxide composite electrode material according to claim 1 , wherein the mass ratio of graphene, urea and NiCl ₂ ·6H ₂ O in the step S3 is 1:4:4. 8 . 8 . The method for preparing a nickel oxide composite electrode material according to claim 7 , wherein the time of the hydrothermal reaction in the step S3 is 4-12 hours; the temperature of the hydrothermal reaction is 140-180° C. 9 . 9 . The method for preparing a nickel oxide composite electrode material according to claim 1 , wherein in the step S4 , the time of the microwave treatment is 3 to 15s; the power of the microwave treatment is 600 to 1200W. 10 . .

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