阅读说明：本技术 一种电化学氧化改性碳材料的方法 (Method for modifying carbon material through electrochemical oxidation ) 是由 黄富强 王远 常郑 于 2018-07-10 设计创作，主要内容包括：本发明涉及一种电化学氧化改性碳材料的方法,将参比电极、对电极和作为工作电极的碳材料电极放入电解液中,采用循环伏安法、恒电压法或恒电流法进行电化学处理,得到改性碳材料；所述碳材料电极为活性炭、碳纳米管、碳纤维、石墨、石墨烯中的至少一种,优选为活性炭。(The invention relates to a method for modifying a carbon material through electrochemical oxidation, which comprises the steps of putting a reference electrode, a counter electrode and a carbon material electrode serving as a working electrode into electrolyte, and carrying out electrochemical treatment by adopting a cyclic voltammetry method, a constant voltage method or a constant current method to obtain a modified carbon material; the carbon material electrode is at least one of activated carbon, carbon nanotubes, carbon fibers, graphite and graphene, and is preferably activated carbon.)

1. A method for modifying a carbon material through electrochemical oxidation is characterized in that a reference electrode, a counter electrode and a carbon material electrode serving as a working electrode are placed in electrolyte, and electrochemical treatment is carried out by adopting a cyclic voltammetry method, a constant voltage method or a constant current method to obtain a modified carbon material; the carbon material electrode is at least one of activated carbon, carbon nanotubes, carbon fibers, graphite and graphene, and is preferably activated carbon.

2. The method according to claim 1, further comprising 0.5 to 2wt% of a binder and 90 to 98wt% of a solvent, wherein the binder is at least one of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Styrene Butadiene Rubber (SBR), and perfluorosulfonic acid type polymer (Nafion), and the solvent is at least one of N-methylpyrrolidone (NMP), ethanol, and water.

3. The method according to claim 1 or 2, wherein the carbon material electrode is attached to a surface of a carbon cloth substrate.

4. A method according to any one of claims 1 to 3, wherein the electrolyte in the electrolyte is H₂SO₄、Li₂SO₄、K₂SO₄、Na₂SO₄、KNO₃At least one of KOH and KCl with the concentration of 0.5M to 5M.

5. The method according to any of claims 1-4, wherein the reference electrode is Ag/AgCl (saturated potassium chloride) and the counter electrode is platinum metal.

6. The method according to any one of claims 1-5, wherein the parameters of cyclic voltammetry comprise: the potential interval is-2V, the scanning speed is 1 mV/s-50 mV/s, and the cycle number is 4-206 circles; preferably, the parameters of cyclic voltammetry include: the potential interval is-1.5V, the scanning speed is 5-20 mV/s, and the cycle number is 4-28 circles; more preferably, the parameters of cyclic voltammetry include: the potential interval is-1.5V, the scanning rate is 10mV/s, and the cycle number is 8 circles.

7. The method according to any one of claims 1-5, wherein the parameters of the constant voltage method include: the potential is 0.5V-3V, and the time is 200-3000 seconds; preferably, the parameters of the constant voltage method include: the potential is 1V-2V, and the time is 500-2000 seconds; more preferably, the parameters of the constant voltage method include: the potential was 1.5V and the time was 1500 seconds.

8. The method according to any one of claims 1-5, wherein the parameters of the galvanostatic method comprise: the current is 1 mA-10 mA, and the time is 200-3000 seconds; preferably, the parameters of the galvanostatic method include: the current is 2 mA-6 mA, and the time is 500-1500 seconds; more preferably, the parameters of the galvanostatic method include: current 3mA, time 1200 seconds.

9. A modified carbon material prepared according to the method of any one of claims 1-8.

10. A supercapacitor comprising the modified carbon material of claim 9.

Technical Field

The invention relates to a method for modifying a carbon material through electrochemical oxidation, in particular to a method for improving the energy density of the carbon material by increasing the specific capacity of the carbon material through electrochemical oxidation, and belongs to the field of optimization modification of carbon materials.

Background

With the development of economy, energy and environmental problems are becoming more severe, and the development of portable electronic devices and hybrid vehicles, people have increasingly strong demands for environment-friendly high-power energy storage devices. Super capacitors, also called electrochemical capacitors, mainly consist of electrodes, electrolyte, current collectors, diaphragms, tabs, etc., and have drawn extensive attention for their high power density, excellent cycle performance (greater than 10000 times) and rapid charge and discharge performance. However, the low energy density of supercapacitors has been limiting its development and application. At present, the main research direction is to further improve the energy density of the electrode material by improving the performance of the electrode material and expanding the electrochemical working window of the electrolyte, for example, N, B, O and the like are doped into the carbon material to further improve the specific capacity of the carbon material; developing an electrode material with a Faraday process pseudo capacitor to improve the specific capacity of the electrode material; the electrochemical working window is expanded by using the organic electrolyte.

Many reports of surface oxidation of activated carbon to increase its specific capacity have also appeared in recent years. Activated carbon is generally oxidized by strong oxidants (concentrated nitric acid, hydrogen peroxide and the like), and oxygen-containing functional groups are increased, so that the specific capacity of the activated carbon is improved. But the chemical oxidation method has serious environmental pollution, high price and difficult control of the oxidation degree.

Disclosure of Invention

In order to solve the problems, the invention provides a method for electrochemically oxidizing and modifying a carbon material, which comprises the steps of putting a reference electrode, a counter electrode and a carbon material electrode serving as a working electrode into an electrolyte, and carrying out electrochemical treatment by adopting a cyclic voltammetry method, a constant voltage method or a constant current method to obtain a modified carbon material; the carbon material electrode is at least one of activated carbon, carbon nanotubes, carbon fibers, graphite and graphene, and is preferably activated carbon.

According to the invention, the carbon material is oxidized by a simple electrochemical method (cyclic voltammetry, constant voltage method, constant current method and the like), so that the oxygen-containing functional group reaches an optimal value, as shown in fig. 9, in the positive potential range of 0V-1.5V, the working electrode (the carbon material to be modified) loses electrons and is oxidized; in the negative potential range of-1.5V to 0V, the working electrode (the carbon material to be modified) obtains electrons and is reduced. In the oxidation-reduction process, the functional group of the carbon material is optimized to obtain the optimal oxygen-containing functional group. In the process of treatment, the potential is higher than that of the common test (-0.2V-0.8V), so that the electrolyte can enter the inside of the electrode material, and the utilization efficiency of the electrode is greatly improved. In the positive potential range of 0V-1.5V, due to electrochemical oxidation stripping, pore channels of the electrode material are enlarged and communicated, so that the movement diffusion of electrolyte is facilitated, and the electrochemical energy storage is facilitated.

Preferably, the carbon material electrode further comprises 0.5-2 wt% of a binder and 90-98 wt% of a solvent, wherein the binder is at least one of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Styrene Butadiene Rubber (SBR) and perfluorosulfonic acid type polymer (Nafion), and the solvent is at least one of N-methylpyrrolidone (NMP), ethanol and water.

Preferably, the carbon material electrode is attached to the surface of the carbon cloth substrate.

Preferably, the electrolyte in the electrolyte is H₂SO₄、Li₂SO₄、K₂SO₄、Na₂SO₄、KNO₃At least one of KOH and KCl with the concentration of 0.5M to 5M.

Preferably, the reference electrode is Ag/AgCl (saturated potassium chloride) and the counter electrode is platinum (e.g., platinum wire).

Preferably, the parameters of cyclic voltammetry include: the potential interval is-2V, the scanning speed is 1-50 mV/s, and the number of cycle turns is 4-206 turns; preferably, the parameters of cyclic voltammetry include: the potential interval is-1.5V, the scanning speed is 5-20 mV/s, and the cycle number is 4-28 circles; more preferably, the parameters of cyclic voltammetry include: the potential interval is-1.5V, the scanning rate is 10mV/s, and the cycle number is 8 circles.

Preferably, the parameters of the constant voltage method include: the potential is 0.5V-3V, and the time is 200-3000 seconds; preferably, the parameters of the constant voltage method include: the potential is 1V-2V, and the time is 500-2000 seconds; more preferably, the parameters of the constant voltage method include: the potential was 1.5V and the time was 1500 seconds.

Preferably, the parameters of the galvanostatic method include: the current is 1-10 mA, and the time is 200-3000 seconds; preferably, the parameters of the galvanostatic method include: the current is 2 mA-6 mA, and the time is 500-1500 seconds; more preferably, the parameters of the galvanostatic method include: current 3mA, time 1200 seconds.

In another aspect, the present invention also provides a modified carbon material prepared according to the above method.

In yet another aspect, the present invention also provides a supercapacitor comprising the modified carbon material as described above.

In the invention, the carbon material is oxidized by a simple electrochemical method, so that the method is safe, controllable and environment-friendly. Specifically, in neutral or acidic electrolyte, a cyclic voltammetry method, a constant voltage method, a constant current method and the like are adopted to oxidize the carbon material, so that the oxygen-containing functional group of the carbon material reaches an optimal value, and the specific capacity of the carbon material (such as activated carbon and the like) is improved from 172.3F/g to 319.7F/g and is improved by 85.5%. Compared with methods such as chemical oxidation and the like for processing carbon materials, the modification method provided by the invention is simple and feasible, safe and environment-friendly, low in price, more excellent in energy storage performance and has the potential of commercial application. The electrochemical energy storage property of the modified activated carbon is improved (mainly used for super capacitors) mainly by electrochemical oxidation modification of the activated carbon (optimizing oxygen-containing functional groups, adjusting pore channel structures and the like).

Drawings

FIG. 1 shows that the concentration of Na is 0.5M₂SO₄Or 1M H₂SO₄The electrochemical data chart of the activated carbon is processed by adopting a cyclic voltammetry method, a constant voltage method and a constant current method, wherein (a) is in a neutral electrolyte (0.5M Na)₂SO₄) In which cyclic voltammetry is used to treat activated carbon, corresponding to example 1, (b) is in acid electrolyte (1M H)₂SO₄) In which cyclic voltammetry is used to treat activated carbon, corresponding to example 1, (c) in acid electrolyte (1M H)₂SO₄) In which activated carbon was treated by the constant voltage method, corresponding to example 7, (d) was in an acid electrolyte (1M H)₂SO₄) The activated carbon is treated by a constant current method, which corresponds to example 8; FIG. 2 shows untreated (blank set), cyclic voltammetry (corresponding to example 1: electrolyte 1M H₂SO₄Potential interval-1.5V, sweep rate 10mV/s, cycle number 8 cycles), constant current method (corresponding to example 5: electrolyte is 1M H₂SO₄Potential was selected to be 1.5V, treatment time was 1200s), and a constant current method (corresponding to example 8: electrolyte is 1M H₂SO₄Current is selected to be 3mA, treatment time is 1200s) after the treatment, the activated carbon is treated at 1MH₂SO₄Cyclic voltammogram (5mV/s) of test (III);

fig. 3 shows the processing conditions after cyclic voltammetry treatment of activated carbon in different electrolytes (corresponding to example 1), which are the corresponding optimal processing conditions: the potential interval is-1.5V, the scanning rate is 10mV/s, the cycle number is 8 circles, and then the voltage is measured at 1MH₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 4 shows the treatment of example 1 under optimum conditions (electrolyte 1M H)₂SO₄Activated carbon (YP80) with potential interval of-1.5V, scanning rate of 10mV/s and cycle number of 8 circles in electrolyte 1M H₂SO₄The cyclic voltammetry curve chart and the front and back change charts of specific capacities with different multiplying powers in the test are shown in the cyclic voltammetry curve chart, the specific capacity is greatly improved by benefiting from the oxidation reduction peak about 0.4V, and the specific capacity under each multiplying power after treatment is greatly improved by changing the specific capacity with different multiplying powers (the>80％)；

FIG. 5 shows the treatment of example 1 under optimum conditions (electrolyte 1M H)₂SO₄Activated carbon (YEC8A) with potential interval of-1.5V, scanning speed of 10mV/s and cycle number of 8 circles) in electrolyte 1M H₂SO₄The cyclic voltammetry curve chart and the front and back change charts of different multiplying power specific capacities are tested in the test, and the specific capacity is improved after treatment as can be seen from the cyclic voltammetry curve chart and the change of different multiplying power specific capacities;

FIG. 6 shows the treatment of example 1 under optimum conditions (electrolyte 1M H)₂SO₄Activated carbon (YEC8B) with potential interval of-1.5V, scanning speed of 10mV/s and cycle number of 8 circles) in electrolyte 1M H₂SO₄The cyclic voltammetry curve chart and the front and back change charts of different multiplying power specific capacities are tested in the test, and the specific capacity is greatly improved after treatment as can be seen from the cyclic voltammetry curve chart and the change of different multiplying power specific capacities;

FIG. 7 shows the treatment of example 1 under optimum conditions (electrolyte 1M H)₂SO₄Activated carbon (YEC200D) with potential interval of-1.5V, scanning speed of 10mV/s and cycle number of 8 circles) in electrolyte 1M H₂SO₄Cyclic voltammetry curve chart of medium test and different multiplying power specific capacity front and back change chartThe safety curve chart and the specific capacity change with different multiplying powers show that the specific capacity is greatly improved after treatment;

FIG. 8 shows the treatment of example 1 under optimum conditions (electrolyte 1M H)₂SO₄A potential interval of-1.5V to 1.5V, a scanning rate of 10mV/s and 8 cycles of circulation) in an electrolyte solution 1M H₂SO₄The cyclic voltammetry curve chart and the front and back change charts of different multiplying power specific capacities are tested in the test, and the specific capacity is greatly improved after treatment as can be seen from the cyclic voltammetry curve chart and the change of different multiplying power specific capacities;

fig. 9 is a schematic diagram showing a change of the carbon material electrode in the electrochemical oxidation treatment. After the electrochemical process treatment, the electrolyte enters the interior of the electrode material (the white circle represents the part which the original electrolyte cannot enter, and the orange circle represents the part which the electrolyte can enter), so that the utilization rate of the electrode material is improved; the pore canal is enlarged, the macropores and the mesopores are slightly increased, and the micropores are reduced; after electrochemical treatment, the pore passages are communicated, which is beneficial to the transmission of electrolyte; oxygen-containing functional group conversion, increase of oxygen-containing functional group with electrochemical activity;

FIG. 10 is a graph of the specific capacity change of the modified activated carbon obtained for different treatment cycles in example 1 and example 2: wherein (a) and (b) indicate that the sample (activated carbon YP50) is 1M H₂SO₄After treating different turns, then at 1M H₂SO₄The tested cyclic voltammetry curve (5mV/s) shows that when the number of treatment turns is less than 28, the oxidation-reduction peak is obvious, the specific capacity is greatly improved, when the number of treatment turns is more than 78, the CV curve is deformed, the oxidation-reduction peak disappears, and the specific capacity is even reduced; (c) the relation between the number of treatment turns and the specific capacity is shown, and the specific capacity is firstly increased and then reduced along with the increase of the number of treatment turns, and reaches the maximum value when the treatment is carried out for 8 turns; (d) the values of (e) and (f) are indicated for the sample (activated carbon YP50) at 1M H₂SO₄After treating different turns, then at 1M H₂SO₄The tested AC impedance curve shows that as the number of treatment turns increases, the contact resistance (intersection point with the x axis) does not change obviously, and the charges are transferredThe resistance (the diameter of the arc) is continuously increased, which is also the reason that the specific capacity is reduced on the contrary when the number of treatment turns is too large;

FIG. 11 shows the treatment of activated carbon (YP50) in example 1 under optimum conditions (electrolyte 1M H)₂SO₄Fourier infrared, Raman and XPS test results after a potential interval of-1.5V to 1.5V, a scanning rate of 10mV/s and a cycle number of 8 circles): it can be seen from the IR spectrum of (a) that the IR peak is significantly enhanced, especially 1570cm^-1The peak of the corresponding benzoquinone bond is increased significantly; from the Raman spectrum of (b), it can be seen that I was after treatment_D/I_GReduction (from 1.13 to 1), mainly during electrochemical treatment, by the effect of oxidative exfoliation, causing exfoliation of the carbon material, which is not stable at the carbon material edges, and thus I_D/I_GDecrease; from the XPS spectra of FIGS. (c), (d), (e) and (f), it can be seen that the conversion of the oxygen-containing functional group from the electrochemically inactive carboxyl group to the electrochemically active benzoquinone group and the hydroxyl group;

FIG. 12 shows untreated activated carbon (YP50) and activated carbon treated for 8 cycles (electrolyte 1 MH) in examples 1 and 2₂SO₄Potential interval of-1.5V, scanning rate of 10mV/s), treatment of 206 rings (electrolyte is 1 MH)₂SO₄And the potential interval is-1.5V, and the scanning speed is 10 mV/s). It can be seen that the specific surface area is slightly reduced and the pore diameter is enlarged when the treatment is carried out for 8 circles, and the structure is collapsed and the specific surface area is sharply reduced when the treatment is carried out for 206 circles;

FIG. 13 shows the sample of activated carbon (YP50) in example 1 at 1M H₂SO₄After the treatment under the medium and optimal conditions (potential interval of-1.5V, scanning rate of 10mV/s and cycle number of 8 circles), the Li is added at 0.5M₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 14 shows the results of example 1 in which the sample of activated carbon (YP50) was 1M H₂SO₄After the treatment under the medium optimal conditions (potential interval of-1.5V, scanning rate of 10mV/s and cycle number of 8 circles), the treatment is carried out at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 15 shows the sample of activated carbon (YP50) in example 1 at 1M H₂SO₄After the treatment under the medium optimal condition (potential interval of-1.5V, scanning rate of 10mV/s and cycle number of 8 circles), testing a cyclic voltammetry curve (5mV/s) in 1M KOH;

FIG. 16 shows the sample of activated carbon (YP50) in example 1 at 1M H₂SO₄After the treatment under the optimal conditions (potential interval of-1.5V, scanning rate of 10mV/s and cycle number of 8 circles), the kinetic analysis is carried out according to peak current and scanning rate, and the reduction of the b value (from the increase of oxidation-reduction control capacitance) and the increase of diffusion coefficient (from the enlargement of pore channels and the communication between pore channels) can be seen;

FIG. 17 shows the results of example 1 with the activated carbon sample (YP50) at 1M H₂SO₄After the treatment under the medium optimal conditions (potential interval of-1.5V, scanning rate of 10mV/s and cycle number of 8 circles), the treatment is carried out at 1M H₂SO₄The medium cyclic stability test result (a) still can keep 96% of the capacity after ten thousand cycles of test, and the pseudocapacitance contributed by the redox peak still stably exists, and the corresponding cyclic voltammetry curve (10mV/s) (b);

FIG. 18 shows the sample of activated carbon (YP50) in example 1 at 1M H₂SO₄The medium optimal conditions (potential interval-1.5V, scanning rate 10mV/s, cycle number 8 circles) and the activated carbon sample (YP50) in example 3 are 1M H₂SO₄Middle treatment (potential interval-1.5V, scanning rate 50mV/s, cycle number 8 circles), then at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III); (ii) a

FIG. 19 shows the results of example 1 with the activated carbon sample (YP50) at 1M H₂SO₄Middle treatment (potential interval-1.5V, scanning rate 10mV/s, cycle number 8 circles) and activated carbon sample (YP50) of example 4 at 1M H₂SO₄Middle treatment (potential interval-1V, scanning rate 10mV/s, cycle number 8 circles), then at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 20 shows that the activated carbon sample (YP50) in example 5 is 1M H₂SO₄Middle treatment (1.5)V, 1200s) and the activated carbon sample (YP50) in example 6 at 1M H₂SO₄Medium treatment (0.6V, 0.8V, 1.2V, 3V; time 1200s) and then at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 21 shows that the activated carbon sample (YP50) in example 5 is 1M H₂SO₄Middle treatment (1.5V, 1200s) and activated carbon sample (YP50) in example 7 at 1M H₂SO₄Medium treatment (1.5V; time 300s, 500s, 3000s respectively) and then at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 22 shows that the activated carbon sample (YP50) in example 8 is 1M H₂SO₄Middle treatment (3mA, 1200s) and activated carbon sample (YP50) of example 9 at 1M H₂SO₄Medium treatment (1mA and 5 mA; time 1200s) then at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 23 shows the results of example 8 in which the sample of activated carbon (YP50) was 1M H₂SO₄Middle treatment (3mA, 1200s) and activated carbon sample (YP50) of example 10 at 1M H₂SO₄Medium treatment (3 mA; time 300s and 2000s, respectively) then at 1M H₂SO₄Cyclic voltammogram (5mV/s) of test (III);

FIG. 24 shows a graphite sheet at 1M H of example 11₂SO₄After medium treatment (potential interval of-2.5V, sweep speed of 10mV/s, cycle number of 8 circles) compared with the untreated graphite plate sample, a is a cyclic voltammetry curve (5mV/s) and b is a charge-discharge curve comparison (4 mA/cm)²)；

FIG. 25 shows aminated carbon nanotubes of 1M H in example 12₂SO₄After the treatment (potential interval of-1.5V, sweep speed of 10mV/s, cycle number of 8 circles) with the untreated graphite plate sample, a is a cyclic voltammetry curve (5mV/s) for comparison, and b is a charge-discharge curve for comparison (1A/g).

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

In the present disclosure, the activated carbon is oxidized by an electrochemical method, and specifically, the electrolyte that can be used is an acidic electrolyte and a neutral electrolyte, such as sulfuric acid, sodium sulfate, potassium nitrate, and the like. Further, carbon materials that can be specifically processed include carbon nanotubes, graphite, carbon fibers, graphene, and the like. By the method, the oxygen-containing functional groups of the carbon material can be obviously improved, and further, the supercapacitor shows higher specific capacity, so that the energy density of the capacitor is improved. It should be noted that the electrochemical oxidation method of the present invention is also applicable to other materials (oxides, organics, etc.) and other fields (electrocatalysis, thermocatalysis, solar cells, fuel cells, etc.).

In one embodiment of the present invention, a cyclic voltammetry method, a constant voltage method, a constant current method, or the like is used to modify a carbon material electrode (e.g., an activated carbon material electrode) to increase its specific capacity and optimize its energy storage properties. The following is an exemplary description of the method of electrochemically oxidizing the modified carbon material.

And (3) preparing a carbon material electrode. Wherein the carbon material electrode is at least one of activated carbon, carbon nanotubes, graphite, carbon fibers and graphene. In addition, the carbon material electrode also comprises 0.5-2 wt% of a binder and 90-98 wt% of a solvent, wherein the binder is at least one of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Styrene Butadiene Rubber (SBR) and Nafion, and the solvent is at least one of N-methylpyrrolidone (NMP), ethanol and water. Preferably, the carbon material electrode is attached to the surface of the carbon cloth substrate.

And preparing an electrolyte. In an alternative embodiment, the electrolyte in the electrolyte is H₂SO₄、Li₂SO₄、K₂SO₄、Na₂SO₄、KNO₃At least one of KOH and KCl with the concentration of 0.5M to 5M. For example, configuration 1M H₂SO₄；0.5M Li₂SO₄；0.5MK₂SO₄；0.5M Na₂SO₄；1M KNO₃(ii) a 1M KOH, and the like. Sulfuric acid, sodium sulfate, potassium sulfate and potassium nitrate.

A three-electrode system is adopted, a carbon material electrode is used as a working electrode, Ag/AgCl (saturated potassium chloride) is used as a reference electrode, a platinum wire is used as a counter electrode, and a constant voltage method, a constant current method, a cyclic voltammetry method and the like are respectively adopted to process carbon materials (activated carbon, carbon nano tubes, graphite, carbon fibers, graphene and the like).

In an alternative embodiment, the parameters of the cyclic voltammetry include: the potential interval is-2V, the scanning speed is 1-50 mV/s, and the number of cycle turns is 4-206 turns; preferably, the parameters of cyclic voltammetry include: the potential interval is-1.5V-1, 5V, the scanning speed is 5-20 mV/s, and the cycle number is 4-28 circles; more preferably, the parameters of cyclic voltammetry include: the potential interval is-1.5V, the scanning rate is 10mV/s, and the cycle number is 8 circles.

In an alternative embodiment, the parameters of the constant voltage method include: the potential is 0.5V-3V, and the time is 200-3000 seconds; preferably, the parameters of the constant voltage method include: the potential is 1V-2V, and the time is 500-2000 seconds; more preferably, the parameters of the constant voltage method include: the potential was 1.5V and the time was 1500 seconds.

In alternative embodiments, the parameters of the galvanostatic method include: the current is 1-10 mA, and the time is 200-3000 seconds; preferably, the parameters of the galvanostatic method include: the current is 2-6 mA, and the time is 500-1500 seconds; more preferably, the parameters of the galvanostatic method include: current 3mA, time 1200 seconds.

Sample characterization

The change in functional groups was observed by Fourier Infrared (FTIR, IFS66V/S & HYPERION 3000, Bruker Optiks), the change in carbon material structure was observed by Raman (Thermal Dispersive Spectrometer), the valence state of the sample surface was measured by XPS (hv 1253.6eV) (XPS, PHI 5000C ESCA System, PerkinElmer), and the pore structure was measured by BET (Micromeritics Tristar 3000). An electrochemical workstation (CHI760E, shanghai chenhua) was used to test the electrochemical energy storage properties of the samples.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

In the following examples, unless otherwise specified, the carbon material electrode is an activated carbon electrode. Preparing an activated carbon electrode: mixing activated carbon (YP50, Coly; or YEC8A, Fuzhou Yihuan carbon, etc.): PVDF: NMP 8:1:1 is prepared into slurry, the slurry is fully stirred and dropped on carbon cloth, and the carbon cloth is put into a vacuum drying oven at 120 ℃ and dried for 10 hours. The electrolyte includes 1M of H provided unless otherwise specified₂SO₄0.5M of Na₂SO₄0.5M Li₂SO₄1M KCl, 1M KNO₃And (3) solution. Finally, the prepared electrode is clamped on a platinum sheet electrode clamp, an Ag/AgCl electrode (saturated potassium chloride) is used as a reference electrode, a platinum wire is used as a counter electrode, and the three-electrode system is put into electrolyte. Electrochemical treatment and testing was performed using electrochemical workstation of Shanghai Chenghua (CHI 760E).