CN109110744B

CN109110744B - Preparation method of hollow tubular polyaniline-based carbon material

Info

Publication number: CN109110744B
Application number: CN201811002560.5A
Authority: CN
Inventors: 高云芳; 张晏; 徐新
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2018-08-30
Filing date: 2018-08-30
Publication date: 2020-04-24
Anticipated expiration: 2038-08-30
Also published as: CN109110744A

Abstract

The invention discloses a preparation method of a hollow tubular polyaniline-based carbon material, which comprises the following steps: taking two parts of acid solution, adding aniline into one part of acid solution, stirring for dissolving, adding hydrogen peroxide, standing for reaction for 1-5h, adding ammonium persulfate into the other part of acid solution, stirring uniformly, rapidly mixing the two parts of solution, standing for reaction for 1-48h, carrying out solid-liquid separation, and drying the solid to obtain a precursor material; and (3) carrying out heat treatment on the precursor material for 0.5-24h at the temperature of 400-1000 ℃ in an inert atmosphere to obtain the polyaniline-based carbon material. The method has the advantages of simple operation, low cost, easy control of product purity, less pollutants, hollow tubular structure of the prepared material, large amount of micropores and good electrochemical performance.

Description

Preparation method of hollow tubular polyaniline-based carbon material

Technical Field

The invention relates to the technical field of carbon materials, and particularly relates to a preparation method of a hollow tubular polyaniline-based carbon material.

Background

Energy is an indispensable material basis for human participation in social activities, and the energy is extremely important along with the rapid consumption of global energy and the continuous deterioration of the environment. The super capacitor is used as one of energy storage devices, has the advantages of strong charging and discharging capacity, environmental friendliness, long cycle life and the like, and has market potential and application value. The super capacitor can be classified into a carbon material, a metal oxide, and a conductive polymer super capacitor according to the difference of active materials. The carbon aerogel belongs to a typical amorphous carbon material, and has a high specific surface area (600-1000 m)²·g^-1) The pores are nano-scale, the pore size distribution is uniform, but the preparation cost is high, and the large-scale production is difficult to realize. The carbon nano tube has active application research, but the specific surface area is low, the electrolyte is difficult to enter the tube, the agglomeration is easy, the dispersion is difficult, and the cost is high. To meet higher commercial requirements, it is necessary to improve the capacitance properties of carbon materials. Two methods for improving the specific capacitance are provided, wherein the electrode material structure is optimized, and pseudo capacitance is introduced into the double-electric-layer capacitance. Nitrogen doping has attracted considerable attention from researchers. In the periodic table of elements, nitrogen elements and carbon elements are adjacent, the atomic diameters are similar, and when nitrogen replaces carbon, obvious malformation change of the material structure can not be caused.

There are two main methods for introducing nitrogen atoms: direct carbonization and post-treatment of nitrogen-rich precursor. Polyaniline is an excellent nitrogen-rich carbonized precursor, containing about 15% nitrogen and 79% carbon. The preparation cost is low, the generation process is mature, the synthesis process is simple, the environmental stability is high, the chemical structure is controllable, the carbonization yield is high, the pores are rich, the impurity content is low, and the method is an ideal precursor material for preparing the nitrogen-doped carbon material by pyrolysis.

The synthesis history of polyaniline is long, the preparation process is simple, and the morphology of polyaniline can be controlled by adjusting the synthesis conditions. Then, polyaniline is used as a nitrogen-rich carbonization precursor, so that the nitrogen-doped carbon material with adjustable and controllable appearance can be obtained. Firstly synthesizing polyaniline, then carrying out pyrolysis treatment, and removing unstable components in the carbon skeleton to obtain the nitrogen-doped carbon material.

Poplar seedling et al, published in Electrochimica Acta, uses polyaniline nanotube as precursor, KOH as activator, and through carbonization treatment, prepares a nitrogen-doped carbon material, which is used as electrode material of super capacitor at current density of 0.1 A.g^-1Specific time capacitance of 163F g^-1(ii) a However, it was found that high temperature may destroy the original morphology of polyaniline.

Yuanfeng et al reported in Electrochemistry Communications that sulfuric acid was used as the doping acid, and synthesized polyaniline nanowires were used as carbon precursors at different temperatures, and nitrogen-rich carbon nanowires were prepared by direct carbonization. The carbonized product at 700 ℃ has the best electrochemical performance corresponding to the higher mesopore ratio and proper nitrogen doping, and the material is used as the electrode material of a super capacitor and has the current density of 0.1 A.g^-1The specific capacitance is 329F g^-1. However, in the process of synthesizing polyaniline, CTAB is required to be used as a structural control agent, the requirements on the uniformity of mixing and the like are high, and particularly in large-scale production, the requirements on the operation level of an operator are high, the product purity is difficult to control, and side reactions are more. In addition, CTAB does not participate in the reaction, and finally generates a large amount of pollutants, so the method is not environment-friendly and has high cost.

Disclosure of Invention

One objective of the present invention is to provide a method for preparing a hollow tubular polyaniline-based carbon material, which is simple in operation, low in cost, easy in product purity control, less in pollutants, and good in electrochemical performance, and the prepared material has a hollow tubular structure and a large number of micropores.

The technical scheme adopted by the invention for solving the technical problems is to provide a preparation method of a hollow tubular polyaniline-based carbon material, which is characterized by comprising the following steps:

the method comprises the following steps: taking two parts of acid solution, adding aniline into one part of acid solution, stirring for dissolving, adding hydrogen peroxide, standing for reaction for 1-5h, adding ammonium persulfate into the other part of acid solution, stirring uniformly, rapidly mixing the two parts of solution, standing for reaction for 1-48h, carrying out solid-liquid separation, and drying the solid to obtain a precursor material; the acid solution is one or a mixture of a plurality of phosphoric acid, oxalic acid, citric acid, tartaric acid, sulfuric acid and p-toluenesulfonic acid in any ratio;

step two: and (3) carrying out heat treatment on the precursor material for 0.5-24h at the temperature of 400-1000 ℃ in an inert atmosphere to obtain the polyaniline-based carbon material.

The polyaniline-based carbon material is prepared by taking polyaniline as a precursor and performing high-temperature pyrolysis.

Preferably, in the first step, the concentration of the acid solution is 0.01-0.1 mol/L in terms of the concentration of hydrogen ions. The concentration of the hydrogen ion is a concentration of hydrogen ions generated when an acid is considered as a strong acid and completely ionized in an aqueous solution.

Preferably, in the first step, the adding amount of the hydrogen peroxide is (2-5) mL/100mL based on the volume of the acid solution.

Preferably, in the step one, the aniline is added in an amount of (1-4) mL/100mL based on the volume of the acid solution.

Preferably, in the first step, the adding amount of the ammonium persulfate is (2.35-9.4) g/100 mL based on the volume of the acid solution.

Preferably, in the step one, the solvent used for the acid solution is an aqueous solution of ethanol; in the ethanol water solution, the volume ratio of ethanol to water is (0.1-1) to 1.

Preferably, in the step one, the two acid solutions are both p-toluenesulfonic acid solutions.

Preferably, in the first step, the time of the first standing reaction is 2-4 h.

Preferably, in the first step, the time of the second standing reaction is 12-24 h.

Preferably, in the first step, the solid-liquid separation method is filtration or centrifugation.

Preferably, in the first step, the drying is carried out for 12-24h at 50-60 ℃ in an air atmosphere.

Preferably, in the second step, the heat treatment is carried out for 2h under the nitrogen atmosphere at 600-800 ℃.

The preparation method of the hollow tubular polyaniline-based carbon material provided by the invention has the following beneficial effects:

1. the polyaniline fiber precursor is prepared by in-situ polymerization by adopting a direct mixing method and taking various acids as dopants, and the polyaniline-based carbon material is obtained by one-step carbonization, so that the method is simple and safe to operate, low in cost and high in product purity; different acids can be selected as doping agents to control and synthesize precursor materials with different appearances; structural control agents such as CTAB and the like are not needed, and pollutants are few; the in-situ polymerization reaction is carried out under the standing condition without stirring, thereby greatly reducing the energy consumption.

2. The oxidant is added by adopting a two-stage method, a small amount of hydrogen peroxide is added in the first stage, the oxidation capacity is low, the polyaniline intermediate oxidation state is generated in the early stage to form an oligomer, the active center of a reaction system is increased, and the ammonium persulfate initiates long-chain polymerization in the second stage to generate a uniform long tubular structure.

3. The precursor material prepared by the method has good thermal stability, and the original tubular structure is still maintained after the high-temperature treatment at 800 ℃.

4. The prepared polyaniline-based carbon material is in a hollow tubular structure, and is beneficial to the transmission and permeation of electrolyte; moreover, the pipe wall is provided with a large number of micropores and mesopore structures, the pore size distribution is wide, and the specific surface area is up to 1025 m²·g^-1The number of reactive active sites is large; when the material is applied to a super capacitor as an electrode material, the material shows high specific capacitance and is 5 mV s^-1The specific capacitance reaches 180 F.g at the potential sweeping speed^-1(ii) a The capacitor has good capacity retention rate and long cycle life, and the specific capacity retention rate exceeds 97% after 1000 charge-discharge cycles; in addition, the method can be used for producing a composite materialLow electrochemical impedance, good rate capability and current density from 0.5A g^-1Increased to 5A g^-1The reduction amplitude of the specific capacitance is smaller.

5. The solvent adopted by the acid solution is an ethanol aqueous solution, the volume ratio of ethanol to water is (0.1-1) to 1, and the solution contains a proper amount of ethanol, so that on one hand, the solution is favorable for dissolving organic acid and takes part in the reaction as doping acid, and on the other hand, the in-situ polymerization rate can be changed, and further the morphology of the synthesized precursor material is changed.

Drawings

FIG. 1 is an XRD pattern of PANI, PANI-C600, PANI-C700, and PANI-C800 in example 1 of the present invention.

FIG. 2 is an SEM photograph of PANI-C800 in example 1 of the present invention.

FIG. 3 is a TEM image of PANI-C800 in example 1 of the present invention.

FIG. 4 (a) is the isothermal nitrogen sorption and desorption curves for PANI, PANI-C600, PANI-C700, and PANI-C800; FIG. 4 (b) is a graph of the aperture distribution of PANI-C600, PANI-C700, and PANI-C800.

FIG. 5a is a cyclic voltammogram of PANI-C700 in example 1 of the present invention, and FIG. 5b is a cyclic voltammogram of PANI-C800 in example 1 of the present invention.

Fig. 6 is an SEM image of

materials

3, 4, 5, 6, and 11 in comparative example 2 of the present invention.

FIG. 7 is a plot of cyclic voltammograms of comparative example 2 of the present invention at different scan rates for Material 3.

FIG. 8 is a plot of cyclic voltammograms of comparative example 2 of the present invention at different scan rates for Material 4.

FIG. 9 is a plot of cyclic voltammograms of comparative example 2 of the present invention at different scan rates for material 5.

FIG. 10 is a plot of cyclic voltammograms of comparative example 2 of the present invention at different scan rates for material 6.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

Example 1

Preparing two parts of 500 mL p-toluenesulfonic acid solution with the concentration of 0.05mol/L (by concentration of hydrogen ions); adding 10 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 3h, adding 23.9 g of ammonium persulfate into the other part, and magnetically stirring for 10min until complete dissolution. The two solutions are quickly mixed and kept stand for reaction for 24 hours at room temperature. And (3) carrying out reduced pressure suction filtration on the fully reacted sample, washing the fully reacted sample for multiple times by using deionized water until the filtrate is colorless, and drying the obtained solid product at 60 ℃ for later use to obtain a dark green precursor material marked as PANI. Dividing the obtained precursor material into three parts, respectively placing into a graphite crucible, introducing nitrogen for protection, and controlling the heating rate at 7 ℃ for min^-1Heating to 600 deg.C, 700 deg.C, 800 deg.C, and maintaining for 2h to obtain three black polyaniline-based carbon materials, respectively labeled as PANI-C600, PANI-C700, and PANI-C800.

Mixing the polyaniline-based carbon material, the acetylene black and the PVDF prepared in the above steps according to a ratio of 8: 1: 1, mixing and grinding, adding a plurality of drops of N-methyl pyrrolidone reagent, and carrying out magnetic stirring treatment for 8 hours to obtain active substance slurry. Uniformly coating a certain amount of slurry on a cleaned titanium sheet with a coating area of 1 × 1 cm². The prepared electrode was dried in a forced air oven at 80 ℃ for 12 h.

The PANI, PANI-C600, PANI-C700, PANI-C800 materials prepared by the above method were subjected to X-ray diffraction analysis (abbreviated as XRD, the same shall apply hereinafter), and the results of the experiment using an X' Pert PRO type X-ray diffraction spectrometer manufactured by PANalytical corporation, the netherlands, are shown in fig. 1. As can be seen from fig. 1: PANI shows characteristic peaks of polyaniline fiber at 2 θ = 18 °, 20 °, and 25 °, corresponding to three crystal planes of polyaniline, namely (011), (020), and (200), respectively, and the characteristic peak at 2 θ = 18 ° is due to the distance between crystal planes of the polyaniline molecule pi-pi stacking. The characteristic peak at 2 θ = 20 ° is due to the periodic parallel structure of the polymer main chain, and the characteristic peak at 2 θ =25 ° is due to the periodic perpendicular structure of the polymer main chain, indicating that the crystallinity of the p-toluenesulfonic acid-doped polyaniline is better. The PANI-C600, PANI-C700 and PANI-C800 materials carbonized at different temperatures have the characteristic peaks of polyaniline disappeared, and polyaniline fiber carbonized products have two wider diffraction peaks at 24 degrees and 43 degrees, and the two peaks respectively represent (002) and (101) crystal faces of graphite materials, so that the polyaniline-based carbon material prepared is mainly amorphous carbon and has low graphitization degree.

The PANI-C800 prepared by the above method is subjected to morphology characterization by using a scanning electron microscope (SEM for short, the same applies below), the microscopic morphology of the PANI-C is studied, and a Hitachi S4700 type scanning electron microscope of Hitachi corporation in japan is used in the experiment, and the result is shown in fig. 2. From the SEM representation results of PANI-C800 material under different magnifications in FIG. 2, it can be clearly seen that the tubular structure is maintained after the high temperature treatment at 800 ℃, the surface is smooth, and the average diameter is between 100 and 200 nm. The polyaniline fiber still keeps the original shape after carbonization and does not generate fusion phenomenon.

In order to better understand the internal structure of the carbonized product of the polyaniline-based carbon material, the PANI-C800 prepared by the method is characterized by a transmission electron microscope (TEM for short, the same below) and the micro-morphology characteristics of the PANI-C800 are researched. The results of the experiment using a Tecnai G2F 30S-Twin high resolution Transmission Electron Microscope (TEM) from Philips-FEI, the Netherlands are shown in FIG. 3. In FIG. 3, a and b are TEM representation results of PANI-C800 under different magnifications, respectively, and it can be clearly seen that PANI-C800 is a hollow tubular structure; moreover, the surface of the pipe wall has developed pores and is rich in a microporous structure.

The PANI, PANI-C600, PANI-C700 and PANI-C800 prepared by the method are subjected to isothermal N₂Adsorption and desorption (BET) tests were carried out by using a full-automatic physical chemical adsorption apparatus model ASAP2020 manufactured by Micromeritics to analyze BET and pore size distribution, and the results are shown in FIG. 4. FIG. 4 (a) is the isothermal nitrogen sorption and desorption curves for PANI, PANI-C600, PANI-C700, and PANI-C800. The adsorption isotherms for all samples were between the type I and type IV isotherms, with higher adsorption capacity at lower relative pressures, typical of microporous features, indicating a large number of micropores in the sample. In the higher pressure range (P/P)₀>0.8) all adsorption curves were strongly enhanced due to N₂Capillary condensation and multilayer absorption in mesopores and macropores, but a hysteresis loop is very tiny, which shows that the mesoporous content of the material is low. FIG. 4 (b) is a graph showing the pore size distribution of PANI-C600, PANI-C700, and PANI-C800, and it is apparent that PANI-C600, PANI-C700, and PANI-C800 all have distinct mesoporous structures. Furthermore, the higher the heat treatment temperature is, the specific surface area of the polyaniline-based carbon material tends to increase, namely three materials PANI-C600, PANI-C700 and PANI-C800 with specific surface areas of 451 m respectively²·g^-1、915 m²·g^-1、1025 m²·g^-1. When the carbonization temperature is higher, the more carbon is lost by pyrolysis gasification, the more pores are present on the surface of the carbon. Although the specific surface area of PANI-C800 is high, the average pore diameter (2 nm) is smaller than that of PANI-C700 (2.67 nm). This is due to the fact that as the temperature increases, the PANI precursor material melts, and while pyrolysis continues to occur to produce more micropores, which become increasingly porous, the coalescence phenomenon shrinks the pores of the large mesopores, resulting in a gradual decrease in the average pore diameter. The specific surface area data of PANI-C600, PANI-C700 and PANI-C800 prepared by the method is far higher than that of carbon nanotubes (BET = 100-400 m) reported in the literature²·g^-1) And the nitrogen element contained plays a greater positive role in the capacity.

FIG. 5 is a graph showing the results of cyclic voltammetry tests of PANI-C700 and PANI-C800. The experiments were tested using a three-electrode system and an electrochemical workstation model CHI 660D. The specific capacitance of the active substance (three-electrode system) can be calculated from the cyclic voltammogram according to the following formula:

C_m= ∫i(t) dt / (2 × v × m × ΔV)

wherein: c_mIs specific capacitance (F.g)^-1) And v is the potential scan rate (mV. s)^-1) Δ V is a potential scanning range (V), i (t) is a current value (a), and m is a single-electrode active material mass (g). From which specific capacitance values at different scan rates are calculated. The specific capacitance values of PANI-C800 are higher than those of PANI-C700 because the specific surface area of PANI-C800 is higher than that of PANI-C700. But is largeScanning rate 50 mV s^-1The degree of deviation of the CV curve of PANI-C800 is obviously worse than that of PANI-C700, because the sample PANI-C800 has small average pore size and small content of large and medium pores, and when the heat treatment temperature is too high, the surface is fused, so that the pore channels are blocked, and the transmission of electrolyte is not facilitated.

Electrochemical performance tests on PANI-C600, PANI-C700 and PANI-C800 prove that the test electrode has higher specific capacitance and excellent rate capability due to the hollow tubular structure and a large number of micro-porous and mesoporous structures of the polyaniline-based carbon material.

PANI-C800 at 5 mV s^-1The specific capacitance reaches 180 F.g at the potential sweeping speed^-1. The multiplying power performance is good, and the current density is from 0.5A g^-1Increased to 5A g^-1The reduction amplitude of the specific capacitance is smaller; the cycle performance is good, and the specific capacitance retention rate exceeds 97% after 1000 charge-discharge cycles.

PANI-C700 at 5 mV s^-1At the potential sweeping speed, the specific capacitance reaches 167 F.g^-1. The multiplying power performance is good, and the current density is from 0.5A g^-1Increased to 5A g^-1The specific capacitance is reduced to a certain extent compared with PANI-C800, the specific capacitance retention rate exceeds 87% after 1000 charge-discharge cycles, and the specific capacitance is also reduced to a certain extent compared with PANI-C800.

PANI-C600 at 5 mV s^-1The specific capacitance reaches 149 F.g at the potential sweeping speed^-1. The multiplying power performance is good, and the current density is from 0.5A g^-1Increased to 5A g^-1The specific capacitance is reduced to a certain extent compared with PANI-C800, the specific capacitance retention rate exceeds 67% after 1000 charge-discharge cycles, and the specific capacitance is also reduced to a certain extent compared with PANI-C800.

Example 2

Preparing two parts of 500 mL p-toluenesulfonic acid solution with the concentration of 0.05mol/L (by concentration of hydrogen ions), wherein the solvent is an aqueous solution of ethanol, and the volume ratio of the ethanol to the water is 0.2: 1; adding 10 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 3h, adding 23.9 g of ammonium persulfate into the other part, and magnetically stirring for 10min until complete dissolution. Mixing the aboveThe two solutions were mixed rapidly and allowed to stand at room temperature for 24 h. And (3) carrying out reduced pressure suction filtration on the fully reacted sample, washing the fully reacted sample for multiple times by using deionized water until the filtrate is colorless, and drying the obtained solid product at 60 ℃ for later use to obtain the precursor material. Putting the obtained precursor material into a graphite crucible, introducing nitrogen for protection, and controlling the heating rate to be 5 ℃ per minute^-1Heating to 800 ℃, and keeping the temperature for 2h to obtain the polyaniline-based carbon material.

Example 3

Preparing two parts of 500 mL p-toluenesulfonic acid solution with the concentration of 0.05mol/L (by concentration of hydrogen ions), wherein the solvent is an aqueous solution of ethanol, and the volume ratio of the ethanol to the water is 0.2: 1; adding 10 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 4h, adding 23.9 g of ammonium persulfate into the other part, and magnetically stirring for 10 min. The two solutions are quickly mixed and kept stand for reaction for 24 hours at room temperature. And (3) carrying out reduced pressure suction filtration on the fully reacted sample, washing the fully reacted sample for multiple times by using deionized water until the filtrate is colorless, and drying the obtained solid product at 60 ℃ for later use to obtain the precursor material. Putting the obtained precursor material into a graphite crucible, introducing argon for protection, and controlling the heating rate to be 5 ℃ per minute^-1Heating to 1000 deg.C, and maintaining for 2h to obtain polyaniline-based carbon material.

Example 4

Preparing two parts of p-toluenesulfonic acid solution with concentration of 0.05mol/L (by concentration of hydrogen ions) of 200 mL, wherein the solvent is an aqueous solution of ethanol, and the volume ratio of the ethanol to the water is 0.2: 1; adding 10 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 3 hours, adding 9.56 g of ammonium persulfate into the other part, and magnetically stirring for 10 min. The two solutions are quickly mixed and kept stand for reaction for 24 hours at room temperature. And (3) carrying out reduced pressure suction filtration on the fully reacted sample, washing the fully reacted sample for multiple times by using deionized water until the filtrate is colorless, and drying the obtained solid product at 60 ℃ for later use to obtain the precursor material. Putting the obtained precursor material into a graphite crucible, introducing nitrogen for protection, and controlling the heating rate to be 5 ℃ per minute^-1Heating to 800 ℃, and keeping the temperature for 2h to obtain the polyaniline-based carbon material. Wherein the ammonium persulfateThe ratio of the amount of (c) to the volume of the acid solution was the same as in example 2.

Example 5

Preparing two parts of p-toluenesulfonic acid solution with concentration of 0.05mol/L (by concentration of hydrogen ions) of 200 mL, wherein the solvent is an aqueous solution of ethanol, and the volume ratio of the ethanol to the water is 0.2: 1; adding 10 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 3 hours, adding 9.56 g of ammonium persulfate into the other part, and magnetically stirring for 10 min. The two clear solutions were mixed quickly and allowed to stand at room temperature for 24 h. And (3) carrying out reduced pressure suction filtration on the fully reacted sample, washing the fully reacted sample for multiple times by using deionized water until the filtrate is colorless, and drying the obtained solid product at 60 ℃ for later use to obtain the precursor material. Putting the obtained precursor material into a graphite crucible, introducing nitrogen for protection, and controlling the heating rate to be 5 ℃ per minute^-1Heating to 600 ℃, and keeping the temperature for 4h to obtain the polyaniline-based carbon material. The volume ratio of the amount of ammonia persulfate to the acid solution was the same as in example 2.

Example 6

Preparing two parts of 500 mL p-toluenesulfonic acid solution with the concentration of 0.02mol/L (by concentration of hydrogen ions), wherein the solvent is an aqueous solution of ethanol, and the volume ratio of the ethanol to the water is 0.5: 1; adding 20 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 3 hours, adding 23.9 g of ammonium persulfate into the other part, and magnetically stirring for 10 min. The rest of the procedure was the same as in example 2. The obtained carbon material has a hollow tubular structure through TEM test.

Example 7

Preparing two parts of 200 mL p-toluenesulfonic acid and phosphoric acid mixed solution with the concentration of 0.05mol/L (by hydrogen ion concentration), adding 10 mL aniline monomer into one part, stirring to dissolve, adding 4 mL hydrogen peroxide, standing for reaction for 4 hours, adding 9.56 g ammonium persulfate into the other part, and magnetically stirring for 10 minutes. The rest of the procedure was the same as in example 2. The obtained carbon material has a hollow tubular structure through TEM test.

Example 8

Preparing 500 mL of mixed solution of methylbenzenesulfonic acid and oxalic acid with the concentration of 0.02mol/L (by hydrogen ion concentration), adding 10 mL of aniline monomer into one part, stirring to dissolve, adding 10 mL of hydrogen peroxide, standing for reaction for 3 hours, adding 23.9 g of ammonium persulfate into the other part, and magnetically stirring for 10 minutes. The rest of the procedure and procedure were the same as in example 1. The obtained carbon material has a hollow tubular structure through TEM test.

Example 9

Preparing 500 mL of mixed solution of methylbenzenesulfonic acid and citric acid with the concentration of 0.02mol/L (by hydrogen ion concentration), adding 10 mL of aniline monomer into one part of the mixed solution, stirring and dissolving the aniline monomer by using an ethanol aqueous solution, adding 10 mL of hydrogen peroxide into the other part of the mixed solution, standing and reacting for 3 hours, adding 23.9 g of ammonium persulfate into the other part of the mixed solution, and magnetically stirring for 10 minutes. The rest of the procedure and procedure were the same as in example 1. The obtained carbon material has a hollow tubular structure through TEM test.

Example 10

Preparing two parts of a mixed solution of p-toluenesulfonic acid and sulfuric acid with the concentration of 0.02mol/L (calculated by the concentration of hydrogen ions), wherein the solvent is an aqueous solution of ethanol, the volume ratio of the ethanol to the water is 0.2: 1, adding 10 mL of aniline monomer into one part, stirring and dissolving, adding 4 mL of hydrogen peroxide, standing for reaction for 3 hours, adding 9.56 g of ammonium persulfate into the other part, and magnetically stirring for 10 minutes. The rest of the procedure and procedure were the same as in example 1. The volume ratio of the amount of ammonia persulfate to the acid solution was the same as in example 2. The obtained carbon material has a hollow tubular structure through TEM test.

Example 11

Preparing two parts of solution of 200 mL of p-toluenesulfonic acid with the concentration of 0.02mol/L (by the concentration of hydrogen ions), wherein the solvent is an aqueous solution of ethanol, the volume ratio of the ethanol to the water is 0.5: 1, adding 10 mL of aniline monomer into one part, stirring and dissolving, adding 4 mL of hydrogen peroxide, standing for reaction for 2 hours, adding 9.56 g of ammonium persulfate into the other part, and magnetically stirring for 10 minutes. The rest of the procedure and procedure were the same as in example 1. The volume ratio of the amount of ammonia persulfate to the acid solution was the same as in example 2. The obtained carbon material has a hollow tubular structure through TEM test.

Example 12

Preparing two solutions of 0.02mol/L (based on the concentration of hydrogen ions) of 200 mL p-toluenesulfonic acid, and using ethanol as a solventIn the aqueous solution of (1), the volume ratio of ethanol to water is 1: 1, 10 mL of aniline monomer is added into one part, 4 mL of hydrogen peroxide is added after stirring and dissolving, standing and reacting are carried out for 3 hours, 9.56 g of ammonium persulfate is added into the other part, and magnetic stirring is carried out for 10 min. The two clear solutions were mixed quickly and allowed to stand at room temperature for 24 h. And (3) carrying out reduced pressure suction filtration on the fully reacted sample, washing the fully reacted sample for multiple times by using deionized water until the filtrate is colorless, and drying the obtained solid product at 60 ℃ for later use to obtain the precursor material. Putting the obtained precursor material into a graphite crucible, introducing nitrogen for protection, and controlling the heating rate to be 5 ℃ per minute^-1Heating to 800 ℃, and keeping the temperature for 8h to obtain the polyaniline-based carbon material. The volume ratio of the amount of ammonia persulfate to the acid solution was the same as in example 2. The obtained carbon material has a hollow tubular structure through TEM test.

Example 13

Preparing two parts of 500 mL p-toluenesulfonic acid solution with the concentration of 0.02mol/L (by hydrogen ion concentration), using an ethanol water solution as a solvent, adding 10 mL aniline monomer into one part of the solution, stirring to dissolve the aniline monomer, adding 10 mL hydrogen peroxide, standing for reaction for 3 hours, adding 9.56 g ammonium persulfate into the other part of the solution, and magnetically stirring for 10 minutes. The rest of the procedure and procedure were the same as in example 1. The volume ratio of the amount of ammonia persulfate to the acid solution was the same as in example 2. The obtained carbon material has a hollow tubular structure through TEM test.

Comparative example 1

Comparison experiments are carried out on PANI-C800 (material 1 for short) prepared in example 1, a polyaniline-based carbon material (material 2 for short) prepared by a method of using polyaniline-based carbon nanotubes as supercapacitor electrode materials and electrochemical properties thereof published on page 7021 and 7027 of the international journal electrochemical journal, the report of Yang seedling and the like, on page 55, on page 7021, on the international journal, the study of electrochemical properties thereof, a polyaniline-based carbon nanowire material (material 3 for short) prepared by a method of using direct carbonization polyaniline nitrogen-rich nanowire carbon nanowires and electrochemical properties thereof, which are published on page 242 and 246 of the international journal, the report of Yuancheng and the like, on 2011, on page 13, on the international journal, the study of electrochemical properties thereof, and 4 materials of commercial activated carbon (XSRC-048, on the basis) to compare specific capacitance, cycle performance and rate performance of the four materials.

TABLE 1 comparison of the parameters of the different materials

And (3) testing conditions are as follows: mixing the polyaniline, the acetylene black and the PVDF obtained by the preparation method according to the weight ratio of 8: 1: 1, mixing and grinding, adding a plurality of drops of N-methyl pyrrolidone reagent, and carrying out magnetic stirring treatment for 8 hours to obtain active substance slurry. Uniformly coating a certain amount of slurry on a cleaned titanium sheet with a coating area of 1 × 1 cm². The prepared electrode was dried in a forced air oven at 80 ℃ for 12 h. Using cyclic voltammetry at 2 mV s^-1And testing the specific capacitance and the cycle performance of the material at the potential sweeping speed.

The result shows that the PANI-C800 prepared in the example 1 has high specific capacitance and good cycle and rate performance.

Comparative example 2

Tubular polyaniline-based carbon materials as shown in Table 2 were prepared by controlled variable method using the experimental conditions for PANI-C800 in example 1 as basic experimental conditions (i.e., the experimental conditions for PANI-C800 in example 1 were the same except for the variables unless otherwise specified), and adjusting the kind of doping acid. Through comparison experiments, the specific capacitance, the cycle performance and the rate capability of the tubular polyaniline-based carbon material prepared under different conditions are compared, and the results are shown in table 2, and the test method and the calculation method of the specific capacitance, the cycle performance and the rate capability are the same as those in example 1.

The results show that different doping acids have obvious influence on the appearance and the performance of the polyaniline-based carbon material. As shown in FIGS. 6 (a), (b), (c), (d), (e), SEM images of

materials

3, 4, 5, 6, and 11, respectively. As shown in FIG. 6 (e), when no doping acid is added to the reaction system, the polyaniline-based carbon material has a micro-scale non-uniform sheet structure. The polyaniline-based carbon material doped with acid is mostly an aggregate with a micro-nano size, which shows that the doped acid is a key factor for synthesizing the polyaniline-based carbon material with the micro-nano structure. All the polyaniline-based carbon materials prepared by acid doping have rich pore channels. FIG. 6 (a) the polyaniline-based carbon material prepared by oxalic acid doping has both nanoparticles and nanorods, and the sizes are different. FIG. 6 (b) shows that most of polyaniline-based carbon materials prepared by citric acid doping are granular and have serious agglomeration. Figure 6 (c) polyaniline-based carbon material prepared by tartaric acid doping has morphology similar to that of polyaniline doped with citric acid, and also has serious agglomeration phenomenon, and small nanoparticles are attached to the surface of large particles. FIG. 6 (d) shows that most of polyaniline-based carbon materials prepared by sulfuric acid doping have a nano-rod shape and uniform diameter.

Analyzing the mechanism of the influence of doping acid on the morphology of the polyaniline-based carbon material: in the acid solution, aniline monomer is protonated to form aniline positive ions, and when the concentration of acid is lower than that of aniline monomer, the aniline positive ions are subjected to proton transfer to form an aggregation state of aniline and aniline ions, and the aggregation state is converted to spherical micelles with lower surface energy in order to achieve stable thermodynamic equilibrium. The acidity of tartaric acid and citric acid is not as strong as that of oxalic acid and sulfuric acid, and the number of proton transfer of aniline positive ions is large, so that spherical polymers are generated in a biased manner, and nano spherical particles are generated.

Fig. 7-10 are cyclic voltammetry graphs of material 3, material 4, material 5, and material 6 at different scanning rates, respectively, the cyclic voltammetry curves of the micro-nano structure polyaniline-based carbon material are all in a rectangle-like shape, have no obvious redox peak, and the curves are well maintained at a large scanning speed, which indicates that the storage mechanism of the micro-nano structure polyaniline-based carbon material is mainly based on double electric layer capacitance. The material 6 has a smaller redox peak, and the polyaniline-based carbon material prepared by doping sulfuric acid possibly contains more heteroatoms, and the heteroatom functional group has a reversible redox peak. From the specific capacitance values of the electrodes calculated from the cyclic voltammograms, it was found that the specific capacitance values of the

materials

3, 4, 5, and 6 were not greatly different from each other, and that the current density was 0.5A g^-1Increased to 5 Ag^-1The specific capacitance of the four materials is reducedThe amplitude is large, and the capacitance retention rate is not high. This is because at large scan rates, the electrolyte ions do not have time to enter the microporous pores of the material, resulting in a reduction in the effective specific surface area and a reduction in the electric double layer interface. Relatively speaking, under the same scanning speed, the specific capacitance value of the polyaniline-based carbon material with the micro-nano structure is higher than that of the polyaniline-based carbon material prepared without acid doping, which shows that the microstructure of the precursor material has obvious influence on the carbonization product.

The specific capacitance of the hollow tubular polyaniline-based carbon material prepared in the embodiment 1 is obviously higher than that of the material prepared under other conditions, and the hollow tubular polyaniline-based carbon material has good cycle and rate performance. This is due to:

(1) when the aniline solution and the ammonium persulfate solution are quickly and directly mixed, the contact chance of reactants and an oxidant is equal, heterogeneous nucleation is not easy to occur, and the chain reaction of polyaniline is continuously carried out.

(2) Macromolecules can directly influence the structure of PANI chains and the connection between chains, and anions of p-toluenesulfonic acid can limit the distortion of the PANI chains, expand the conformation of the chains and increase the conjugation length. When the methylbenzene sulfonic acid is doped with polyaniline, the benzene ring structure in the anion increases the steric hindrance effect.

(3) The organic sulfonic acid can improve the solubility of polyaniline in aqueous solution, the direct mixing method does not need mechanical stirring, the whole reaction system is in a standing state, the p-toluenesulfonic acid improves the solubility of polyaniline products, and the uniformity of the reaction system is ensured.

Comparative example 3

By adopting a variable control method, taking the experimental conditions for preparing the PANI-C800 in the example 1 as basic experimental conditions (namely, if no special description exists, the experimental conditions except the variables are the same as the experimental conditions for preparing the PANI-C800 in the example 1), and comparing the two materials by changing the addition amount of the oxidant hydrogen peroxide in the step I, so as to compare the specific capacitance, the cycle performance and the rate capability of the two materials. The results are shown in Table 3, the test methods and procedures are the same as in example 1.

The results show that the specific surface area of the polyaniline carbon-based material obtained in example 1 is significantly different from that obtained without adding hydrogen peroxide, the polyaniline carbon-based material obtained with adding hydrogen peroxide is smaller than that obtained without adding hydrogen peroxide, and the specific surface area of the prepared carbon-based material is gradually reduced with the increase of the addition amount of hydrogen peroxide. When the aniline is prepared at room temperature, the activity of the aniline is high, the system is easy to synthesize low molecular weight polymers such as dimer trimer by directly adding ammonium persulfate in one step, and the small molecular weight polymers are easy to crack and gasify during high-temperature carbonization. The specific surface area of the polyaniline fiber is only 154 m²·g^-1The specific surface area is greatly changed after carbonization.

The oxidant is added by adopting a two-stage method, a small amount of hydrogen peroxide is added in the first stage, and the oxidation of the hydrogen peroxide is weak, so that the products mainly generated in the early stage of the reaction are intermediate oxidation states of polyaniline, the intermediate oxidation states are mainly oligomers of the polyaniline, and the oligomers can be used as the reaction active center in the second stage. In the second stage, ammonium persulfate is used as an oxidant, firstly ammonium persulfate is used as an initiator, so that the polyaniline chain rapidly grows and polymerizes, and further grows into a uniform long tubular structure on the basis of the first stage. . In the initial stage of the reaction, aniline monomer is consumed, so that the secondary growth of polyaniline is inhibited, and the polyaniline reacts along the chain structure. When polyaniline is carbonized at high temperature, the oligomer and the like are subjected to pyrolysis reaction and gasification loss, and pores are formed on the surface of carbon. The result shows that the PANI-C800 prepared in example 1 has a hollow tubular structure, has higher specific capacitance when being used as an electrode material in a super capacitor, and has good cycle and rate performance.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

1. A preparation method of a hollow tubular polyaniline-based carbon material is characterized by comprising the following steps:

the method comprises the following steps: taking two parts of acid solution, adding aniline into one part of the acid solution, stirring and dissolving, adding hydrogen peroxide, standing and reacting for 1-5 hours, wherein the adding amount of the hydrogen peroxide is (2-5) mL/100mL based on the volume of the acid solution, the adding amount of the ammonium persulfate is (2.35-9.4) g/100 mL based on the volume of the acid solution, stirring uniformly, rapidly mixing the two parts of solution, standing and reacting for 1-48 hours, carrying out solid-liquid separation, and drying the solid to obtain a precursor material; the acid solution is one or a mixture of a plurality of phosphoric acid, oxalic acid, citric acid, tartaric acid, sulfuric acid and p-toluenesulfonic acid in any ratio, and the concentration of the acid solution is 0.01-0.1 mol/L in terms of the concentration of hydrogen ions;

2. The method for preparing a hollow tubular polyaniline-based carbon material as claimed in claim 1, wherein:

in the first step, the adding amount of the aniline is (1-4) mL/100mL based on the volume of the acid solution.

3. The method for preparing a hollow tubular polyaniline-based carbon material as claimed in claim 1, wherein:

in the first step, the solvent adopted by the acid solution is an aqueous solution of ethanol; in the ethanol water solution, the volume ratio of ethanol to water is (0.1-1) to 1.

4. The method for preparing a hollow tubular polyaniline-based carbon material as claimed in claim 3, wherein:

in the first step, the two acid solutions are both p-toluenesulfonic acid solutions.

5. The method for preparing a hollow tubular polyaniline-based carbon material as described in any one of claims 1 to 4, wherein:

in the first step, the standing reaction time is 12-24 h.

6. The method for preparing a hollow tubular polyaniline-based carbon material as described in any one of claims 1 to 4, wherein:

in the first step, the solid-liquid separation method is filtration or centrifugation; the drying is carried out for 12-24h at 50-60 ℃ in air atmosphere.

7. The method for preparing a hollow tubular polyaniline-based carbon material as described in any one of claims 1 to 4, wherein:

in the second step, the heat treatment condition is that the heat treatment is carried out for 2 hours at the temperature of 600-.