CN115483037B - A polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material and its preparation method and application - Google Patents

Abstract

The invention is a polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material and its preparation method and application, which belongs to the technical field of material synthesis. The invention adopts a one-pot method to prepare the polypyrrole/two-dimensional titanium carbide/sodium alginate/calcium carbonate hydrogel composite material. After freeze-drying, the polypyrrole/two-dimensional titanium carbide/sodium alginate/calcium carbonate water is mixed with hydrochloric acid. The surface calcium carbonate particles of the gel composite material are completely etched, and a polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material with a three-dimensional porous structure is obtained. The preparation method of the polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material proposed by the present invention is simple and easy to implement. When the composite material is used as a supercapacitor electrode, it has higher specific capacitance and better cycle stability. .

Description

A polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material and its preparation Methods and applications

Technical field

The invention belongs to the technical field of material synthesis, and specifically relates to a polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material and its preparation method and application.

Background technique

Supercapacitors are considered to be promising products in the field of energy storage because of their advantages such as high energy density, fast charge and discharge rates, and high rate performance. However, their limited power density and cycle life are still not enough to meet the growing demand for energy storage. demand for new energy storage equipment. According to different charge storage principles, supercapacitors are mainly divided into two categories: electrochemical double layer capacitors and pseudocapacitors. The former stores charges electrostatically through ion adsorption on the electrode surface, and usually uses carbon materials with larger surface areas as electrode materials; while the capacitance of pseudocapacitors comes from the rapid and reversible redox reaction process at the interface, usually using transition metal oxides, Sulfides, hydroxides and conductive polymers are used as electrode materials. The key to obtaining high and stable specific capacitance is to design electroactive materials. Existing technologies often improve the electrochemical properties of electrode materials by controlling their microstructure, such as specific surface area and pores.

Therefore, many researchers have adopted pseudocapacitive materials such as conductive polymers and polypyrrole, among which conductive polymers have attracted the attention of researchers due to their convenient synthesis and high conductivity. Polypyrrole is widely used in the research of supercapacitor electrode materials because of its advantages such as large pseudocapacitance, simple synthesis, and low cost. However, polypyrrole undergoes volume changes due to repeated doping/dedoping of ions during high-speed cycling, resulting in poor cycling stability. Therefore, we can compound polypyrrole with other materials with strong mechanical properties to improve its specific capacitance and stability.

In recent years, two-dimensional transition metal carbides and nitrides (also known as MXenes) have attracted widespread attention due to their excellent electrochemical properties. Its general molecular formula is M _n+1 X _n T _x (n=1, 2, 3), where M represents a transition metal, ; MXenes have electrochemically active centers, which originate from the rapid conversion of transition metals with different valence states and the rapid redox reaction of surface terminated functional groups, and their conductivity is as high as 10000S cm ^-1 . Among them, two-dimensional titanium carbide has attracted great attention as a supercapacitor electrode material. In addition, it also has excellent characteristics of electrode materials such as high rate performance, high power density, excellent cycle stability and high energy density. However, like graphene, self-aggregation occurs due to the strong van der Waals interaction between adjacent nanosheets of two-dimensional titanium carbide, which seriously hinders the penetration of electrolyte ions and limits the electrochemistry of two-dimensional titanium carbide electrode materials. performance and practical applications. To solve these problems, heterostructure electrode materials of two-dimensional titanium carbide and other high specific capacitance compounds have been produced to increase the interlayer spacing of two-dimensional titanium carbide and thereby improve its electrochemical performance.

Contents of the invention

In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to design and provide a polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material and its preparation method and application. The present invention has three-dimensional porous polypyrrole /Two-dimensional titanium carbide/sodium alginate airgel composite material can not only promote the transfer of electrons and electrolyte ions, but also combines the excellent characteristics of polypyrrole and two-dimensional titanium carbide such as high specific capacitance. Therefore, polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composites have great potential as supercapacitor electrode materials.

In order to achieve the above objects, the present invention adopts the following technical solutions:

On the one hand, the present invention provides a method for preparing polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material, using a one-pot method to prepare polypyrrole/two-dimensional titanium carbide/sodium alginate/calcium carbonate hydrogel. After freeze-drying, the surface calcium carbonate particles of the polypyrrole/two-dimensional titanium carbide/sodium alginate/calcium carbonate hydrogel composite were completely etched with hydrochloric acid to obtain polypyrrole/two-dimensional porous structure. Dimensional titanium carbide/sodium alginate airgel composite.

A method for preparing polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material, which is characterized in that it specifically includes the following steps:

(1) Weigh the sodium alginate, add it to ultrapure water and stir magnetically, add pyrrole, stir evenly to form a sol, add a single layer of two-dimensional titanium carbide and calcium carbonate particles, stir magnetically, slowly add ammonium persulfate solution dropwise, and stir magnetically A black gel forms and is placed in a 4°C refrigerator until pyrrole polymerization is complete;

(2) Freeze-dry, soak in hydrochloric acid solution to completely etch the calcium carbonate particles, wash repeatedly with ultrapure water, and freeze-dry to obtain a three-dimensional porous polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material .

According to the preparation method, the mass ratio of the sodium alginate, pyrrole, single-layer two-dimensional titanium carbide and calcium carbonate particles is: 0.1~0.5g:0.2~0.3g:20~30mg:1~120mg, and the seaweed The mass and volume ratio of sodium acid, ultrapure water and ammonium persulfate solution is 0.1~0.5g:5~15mL:0.1~1.5mL, and the concentration of ammonium persulfate solution is 1.5~2.5mol L ^-1 .

According to the preparation method, the magnetic stirring time is 2 to 5 hours, the concentration of hydrochloric acid is 0.1 to 1 mol L ^-1 , and the etching time is 1 to 3 hours.

According to the preparation method, the preparation process of the single-layer two-dimensional titanium carbide is specifically: weigh lithium fluoride, dissolve it in a hydrochloric acid solution, slowly add titanium aluminum carbide under magnetic stirring, etching at room temperature, and using ultrasonic Centrifuge and wash with pure water several times until the pH of the centrifugation supernatant is 6.8-7.2. Collect the multi-layer two-dimensional titanium carbide supernatant, bubble it with nitrogen and then sonicate it. After centrifugation, collect the single-layer two-dimensional titanium carbide colloidal supernatant. liquid, continuously flowing nitrogen gas to obtain a single layer of two-dimensional titanium carbide, and store it in a 4°C refrigerator. Calculation method for the concentration of two-dimensional titanium carbide colloid: measure a certain volume of supernatant in a petri dish, freeze-dry and weigh the mass to calculate the concentration.

According to the preparation method, the mass and volume ratio of lithium fluoride, hydrochloric acid solution and titanium aluminum carbide is: 0.1~2g:15~25mL:0.1~2g, preferably the mass of lithium fluoride, hydrochloric acid solution and titanium aluminum carbide. The volume ratio is 1g:20mL:1g, the concentration of the hydrochloric acid solution is 5~10mol L ^-1 ; the etching time is 20~30h, and the nitrogen gas introduction time is 15~30min.

According to the preparation method, the preparation process of the calcium carbonate particles is specifically: weigh equal volumes of calcium chloride solution and sodium carbonate solution of equal concentration, mix them, place them in a mixed solution of water and ethylene glycol, and magnetically stir. Continuous centrifugal washing with ethanol, methanol, and acetone in order to remove unreacted ions and ethylene glycol, collect the precipitated calcium carbonate particles, and dry them.

According to the preparation method, the concentrations of the calcium chloride solution and the sodium carbonate solution are both 0.05 to 0.2 mol L ^-1 , preferably 0.1 mol L ^-1 , and the volumes of the calcium chloride solution and the sodium carbonate solution are both 30~60mL; the volume ratio of water and ethylene glycol is 1:2~15, the magnetic stirring time is 20~40min, and the drying temperature is 50~100°C.

In a second aspect, the present invention provides a polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material, which is prepared by any of the preparation methods described above.

In a third aspect, the present invention provides the use of the polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material as a supercapacitor electrode material.

Principle of the invention: polypyrrole has a high specific capacitance, and polypyrrole and sodium alginate can form a three-dimensional network structure aerogel. The two-dimensional titanium carbide nanosheets are prone to agglomeration between the sheets, resulting in a decrease in electrochemical performance. Dispersing 2D titanium carbide nanosheets in an aerogel network can increase the spacing between sheets and therefore improve electrochemical performance. Finally, calcium carbonate particles are used as sacrificial templates to form a three-dimensional porous aerogel. The three-dimensional porous aerogel network can promote the transfer of electrolyte ions and improve the electrochemical performance of the composite material.

Compared with the prior art, the present invention has the following beneficial effects:

The preparation method of the invention is simple and easy to implement. When the polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material is used as a supercapacitor electrode, it has higher specific capacitance and better cycle stability.

Description of the drawings

Figure 1 is a scanning electron microscope image of titanium aluminum carbide (A), two-dimensional titanium carbide (B), and calcium carbonate particles (C) prepared in Example 1, and a particle size distribution chart (D) of the calcium carbonate particles;

Figure 2 is a scanning electron microscope image of polypyrrole/two-dimensional titanium carbide/sodium alginate-n prepared in Example 1, where n=0 (A), 1 (B), 2 (C), 3 (D);

Figure 3 is an X-ray powder diffraction pattern of the polypyrrole prepared in Comparative Example 1 and the two-dimensional titanium carbide, sodium alginate, polypyrrole/two-dimensional titanium carbide/sodium alginate-2, and titanium aluminum carbide prepared in Example 1;

Figure 4 is the X-ray photoelectron spectrum of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1;

Figure 5 shows the polypyrrole prepared in Comparative Example 1 and the two-dimensional titanium carbide prepared in Example 1, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) at 100 mV s ^- Cyclic voltammetry curve at ¹ scan rate;

Figure 6 is the cyclic voltammogram curve of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1 at different scan speeds;

Figure 7 shows the relative contribution rate of capacitance control and diffusion control to current of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1 at different scan rates;

Figure 8 shows the polypyrrole prepared in Comparative Example 1 and the two-dimensional titanium carbide prepared in Example 1, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) in 1Ag ^-1 Galvanostatic charge and discharge curve at the current density;

Figure 9 is the galvanostatic charge and discharge curves of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1 under different current densities;

Figure 10 is the electrochemical exchange of polypyrrole prepared in Comparative Example 1 and two-dimensional titanium carbide prepared in Example 1, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) Impedance diagram with balanced circuit diagram internally labeled;

Figure 11 is a cycle stability chart of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and examples, but the present invention is not limited to the following examples.

Example 1:

The preparation of polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material includes the following steps:

(1) Dissolve 1g lithium fluoride in 20mL 9mol L ^-1 hydrochloric acid solution, and then slowly add 1g titanium aluminum carbide powder under magnetic stirring. After etching at 35°C for 24 hours, it was centrifuged and washed multiple times with ultrapure water until the pH of the supernatant was 7. Then, the aqueous solution of multi-layered two-dimensional titanium carbide was bubbled with nitrogen for 20 minutes and then ultrasonicated for 1 hour. Centrifuge at 3500 rpm for 1 h, and collect the supernatant of the single-layer two-dimensional titanium carbide colloid. The supernatant was collected in a glass bottle, continuously aerated with nitrogen for 20 min, and then stored in a 4°C refrigerator for later use. Calculation method for the concentration of two-dimensional titanium carbide colloid: measure 10 mL of the supernatant in a petri dish, freeze-dry and weigh the mass. The concentration is approximately 4.87 mg mL ^-1 . Figure 1 (A) and (B) are scanning electron microscopy images of bulk titanium aluminum carbide and single-layer two-dimensional titanium carbide nanosheets respectively. It can be seen that the single-layer two-dimensional titanium carbide nanosheets have been successfully prepared; Figure 1 ( C) is the synthesized calcium carbonate particles. It can be seen from Figure 1(D) that the particle size range of the calcium carbonate particles is 0.6 to 1.4 μm.

(2) Place equal volumes of 0.1 mol L ^-1 calcium chloride and 0.1 mol L ^-1 sodium carbonate solutions in water and ethylene glycol (volume ratio 1:5), and stir magnetically for 30 minutes. Subsequently, the synthesized calcium carbonate particles were collected by centrifugal washing with ethanol, methanol, and acetone at 10,000 rpm to remove unreacted ions and ethylene glycol, and then dried at 60°C for later use.

(3) Measure 10 mL of ultrapure water into a 30 mL glass sample bottle, add 0.3 g of sodium alginate, and magnetically stir evenly, then add 270 mg of pyrrole and stir evenly to form a sol. Then measure 5 mL of two-dimensional titanium carbide colloid (about 24.35 mg) obtained in step (1), and then respectively weigh 0, 10, 50, and 100 mg of calcium carbonate particles prepared in step (2), dissolve them in the above sol, and stir magnetically for 3 hours. . Then slowly add 1 mL of 2.28 mg L ^-1 ammonium persulfate solution dropwise, and stir for 10 s to form a black hydrogel. Place the hydrogel in a 4°C refrigerator until the pyrrole polymerization is complete. After freeze-drying at -58°C for 24 hours, it is soaked in 0.5 mol L ^-1 hydrochloric acid solution for 2 hours to completely etch the calcium carbonate particles, and then washed repeatedly with ultrapure water. , freeze-drying to obtain a three-dimensional porous polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material (according to the difference in mass of calcium carbonate particles, the sample is named polypyrrole/two-dimensional titanium carbide/sodium alginate-n, Among them, n=0, 1, 2, and 3, respectively representing the mass of added calcium carbonate of 0, 10, 50, and 100 mg).

As shown in Figure 2(A)(B)(C)(D), they are scanning electron microscope images of polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) respectively. It can be seen from Figure 2(A) that when no calcium carbonate particles are added to the airgel, there are fewer voids on the surface of the airgel; as the content of calcium carbonate particles increases, the pore size on the surface of the airgel gradually becomes larger, such as: Figure 2 (B)(C)(D). In particular, it can be seen from Figure 2(D) that there are large cavities on the surface of the airgel. It may be because the calcium carbonate particles contain too much and agglomerate, so large cavities are left after etching.

Figure 3 shows the X-ray powder diffraction patterns of polypyrrole, two-dimensional titanium carbide, sodium alginate, polypyrrole/two-dimensional titanium carbide/sodium alginate-2, and titanium aluminum carbide. In the figure, polypyrrole is at 2θ=15°~ The peak at 35° is a characteristic peak of amorphous polypyrrole. Among the diffraction peaks of titanium aluminum carbide precursor and two-dimensional titanium carbide, titanium aluminum carbide corresponds to (002), (004), (104) in titanium aluminum carbide at 2θ=9.55°, 19.00°, 38.75°, and 60.34° respectively. ) and (110) crystal plane (JCPDS No.52-0875). It is worth noting that the diffraction peaks of the (002) and (004) crystal planes of two-dimensional titanium carbide move to a lower angle than before etching, indicating that the aluminum layer in titanium aluminum carbide can be successfully removed by etching. In addition, the diffraction peak of two-dimensional titanium carbide at 38.75° corresponding to the (104) crystal plane disappeared, indicating the removal of the aluminum layer and the successful preparation of two-dimensional titanium carbide. The broad peaks of sodium alginate at 2θ=13.50° and 22.50° are characteristic peaks of the amorphous polymer structure of sodium alginate with low crystallinity. The diffraction peaks of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 at 2θ=6.07° and 17.49° respectively correspond to the (002) and (004) crystal planes of two-dimensional titanium carbide; the diffraction peaks at 2θ=13.5° The peak is the characteristic peak of sodium alginate, and the diffraction peak at 22.50° is attributed to the superposition of two broad peaks of polypyrrole and sodium alginate. In summary, it illustrates the successful preparation of polypyrrole/two-dimensional titanium carbide/sodium alginate-2.

Figure 4 shows the X-ray photoelectron spectrum of polypyrrole/two-dimensional titanium carbide/sodium alginate-2. It can be seen that there are fluorine, oxygen, titanium, nitrogen, and carbon elements in the composite material.

(4) Disperse the obtained polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) into ultrapure water to obtain a dispersion of 1 mg mL ^-1 , and pipette Use a gun to transfer 5 μL onto the surface of the electrode and dry it with an infrared lamp to obtain a polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) modified electrode. Then the polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) modified electrode was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum sheet electrode was used as the counter electrode, 2 mol L ^-1 H ₂ SO ₄ was used as the electrolyte, and cyclic voltammetry tests and galvanostatic charge and discharge were performed on polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) through an electrochemical workstation. test.

The performance verification of the polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material prepared in Example 1 is as follows:

Figure 5 shows the cyclic voltammetry curves of polypyrrole, two-dimensional titanium carbide, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) at a scan rate of 100mV s ^-1 , it can be seen from Figure 5 that the closed area of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 is the largest, indicating that it has the best capacitive behavior. In addition, the closed area of the curve is an irregular rectangle, indicating that the electrode material has both pseudocapacitive behavior and electric double layer capacitive behavior.

Figure 6 shows the cyclic voltammetry curves of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 at different scan rates. As the scan rate increases, the closed area of the curve gradually increases, but the shape remains unchanged. , indicating that the composite material has good reversibility and rate performance.

As shown in Figure 7, the relative contribution rate of capacitance control and diffusion control to current of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 at different scan rates is calculated by formula (a). The relative contribution rate at different scan rates can be calculated . As the scan rate increases, the contribution of capacitance control also increases, which indicates that the diffusion control dominated by the polypyrrole/2D titanium carbide/sodium alginate-2 electrode at low scan rates gradually changes to capacitance control.

Figure 8 shows the galvanostatic charge and discharge curves of polypyrrole, two-dimensional titanium carbide, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) at a current density of 1Ag ^-1 , polypyrrole/two-dimensional titanium carbide/sodium alginate-2 has the longest charge and discharge time, indicating that it has the largest specific capacitance. Through formula (b), the ratio of polypyrrole, two-dimensional titanium carbide, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3) can be calculated when the current density is 1Ag ^-1 The capacitances are 246F g ^-1 , 299Fg ^-1 , 475F g ^-1 , and 174F g ^-1 respectively.

Figure 9 shows the galvanostatic charge and discharge curves of polypyrrole/two-dimensional titanium carbide/sodium alginate-2 at different current densities. The shape of the curve is not a strictly symmetrical triangle. Especially at low current densities, the discharge curve is slightly Trailing. It shows that the electrode material has both pseudocapacitance and electric double layer capacitance properties.

Figure 10 shows the electrochemical AC impedance diagram of polypyrrole, two-dimensional titanium carbide, polypyrrole/two-dimensional titanium carbide/sodium alginate-n (n=0, 1, 2, 3), and the inset illustration is a balanced circuit diagram. In the low-frequency region, polypyrrole/two-dimensional titanium carbide/sodium alginate-2 has the largest slope, indicating that it has the smallest extended Warburg impedance and has faster mass transfer capabilities.

Figure 11 shows the cycle stability diagram of polypyrrole/two-dimensional titanium carbide/sodium alginate-2. After 1500 cycles of charge and discharge, the capacitance retention rate is 81%. This shows that the polypyrrole/two-dimensional titanium carbide/sodium alginate-2 aerogel has high stability.

i(V)＝k ₁ v+k ₂ v ^1/2 (a)

In formula a, i (V) represents the response current at a specific potential, v represents the scan rate, k ₁ and k ₂ represent the capacitance control and diffusion control coefficients respectively.

In formula b, Cs(F g ^-1 ) represents the specific capacitance, I(A) represents the current, Δt(s) represents the discharge time, m(g) represents the mass of the electroactive material, and ΔV(V) represents the potential window.

Example 2

The preparation of polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material includes the following steps:

(1) Dissolve 0.1g lithium fluoride in 15mL 5mol L ^-1 hydrochloric acid solution, and then slowly add 0.1g titanium aluminum carbide powder under magnetic stirring. After etching at 35°C for 20 h, it was centrifuged and washed multiple times with ultrapure water until the pH of the supernatant was approximately 6.8. Then, the aqueous solution of multi-layered two-dimensional titanium carbide was bubbled with nitrogen for 15 minutes and then ultrasonicated for 1 hour. Centrifuge at 3500 rpm for 1 h, and collect the supernatant of the single-layer two-dimensional titanium carbide colloid. The supernatant was collected in a glass bottle, continuously aerated with nitrogen for 20 min, and then stored in a 4°C refrigerator for later use.

(2) Place an equal volume of 30 mL of 0.05 mol L ^-1 calcium chloride and 0.05 mol L ^-1 sodium carbonate solution into water and ethylene glycol (volume ratio is 1:2), and stir magnetically for 20 minutes. Subsequently, the synthesized calcium carbonate particles were collected by centrifugal washing with ethanol, methanol, and acetone at 10,000 rpm to remove unreacted ions and ethylene glycol, and then dried at 50°C for later use.

(3) Measure 5 mL of ultrapure water into a 30 mL glass sample bottle, add 0.1 g of sodium alginate, and magnetically stir evenly, then add 200 mg of pyrrole and stir evenly to form a sol. Then measure 5 mL of two-dimensional titanium carbide colloid (approximately 24.35 mg) obtained in step (1), and then weigh 1 mg of calcium carbonate particles prepared in step (2), dissolve them in the above sol, and stir magnetically for 2 hours. Then slowly add 1 mL of 2.28 mg L ^-1 ammonium persulfate solution dropwise, and stir for 10 s to form a black hydrogel. Place the hydrogel in a 4°C refrigerator until the pyrrole polymerization is complete. After freeze-drying at -58°C for 24 hours, it is soaked in 0.1 mol L ^-1 hydrochloric acid solution for 1 hour to completely etch the calcium carbonate particles, and then washed repeatedly with ultrapure water. , freeze-drying to obtain a three-dimensional porous polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material. The polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material prepared in Example 2 has similar properties to the polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1.

Example 3:

The preparation of polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material includes the following steps:

(1) Dissolve 2g lithium fluoride in 25mL 10mol L ^-1 hydrochloric acid solution, and then slowly add 2g titanium aluminum carbide powder under magnetic stirring. After etching at 35°C for 30 h, it was centrifuged and washed multiple times with ultrapure water until the pH of the supernatant was 7.2. Then, the aqueous solution of multi-layered two-dimensional titanium carbide was bubbled with nitrogen for 30 minutes and then ultrasonicated for 1 hour. Centrifuge at 3500 rpm for 1 h, and collect the supernatant of the single-layer two-dimensional titanium carbide colloid. The supernatant was collected in a glass bottle, continuously aerated with nitrogen for 20 min, and then stored in a 4°C refrigerator for later use.

(2) Mix an equal volume of 60 mL of 0.2 mol L ^-1 calcium chloride and 0.2 mol L ^-1 sodium carbonate solution, place it in water and ethylene glycol (volume ratio: 1:15), and stir magnetically for 40 minutes. Subsequently, the synthesized calcium carbonate particles were collected by centrifugal washing with ethanol, methanol, and acetone at 10,000 rpm to remove unreacted ions and ethylene glycol, and then dried at 100°C for later use.

(3) Measure 15 mL of ultrapure water into a 30 mL glass sample bottle, add 0.5 g of sodium alginate, and magnetically stir evenly, then add 300 mg of pyrrole and stir evenly to form a sol. Then measure 5 mL of two-dimensional titanium carbide colloid (approximately 24.35 mg) obtained in step (1), and then weigh 120 mg of calcium carbonate particles prepared in step (2), dissolve them in the above sol, and stir magnetically for 5 hours. Then slowly add 1 mL of 2.28 mg L ^-1 ammonium persulfate solution dropwise, and stir for 10 s to form a black hydrogel. Place the hydrogel in a 4°C refrigerator until the pyrrole polymerization is complete. After freeze-drying at -58°C for 24 hours, it is soaked in 1 mol L ^-1 hydrochloric acid solution for 3 hours to completely etch the calcium carbonate particles, and then washed repeatedly with ultrapure water. Three-dimensional porous polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite was obtained by freeze-drying. The polypyrrole/two-dimensional titanium carbide/sodium alginate airgel composite material prepared in Example 3 has similar properties to the polypyrrole/two-dimensional titanium carbide/sodium alginate-2 prepared in Example 1.

Comparative example 1:

The preparation of polypyrrole includes the following steps:

(1) Under ice bath conditions, weigh 270 mg of pyrrole and dissolve it in 10 mL of ultrapure water, and stir evenly. Slowly add 1 mL of 2.28 mg L ^-1 ammonium persulfate solution dropwise, and place it in a 4°C refrigerator for reaction for 24 hours. The product was washed repeatedly with ultrapure water and absolute ethanol, and dried in a 60°C oven.

(2) Disperse the obtained polypyrrole into ultrapure water to obtain a dispersion of 1 mg mL ^-1 . Use a pipette to transfer 5 μL dropwise onto the surface of the electrode and dry it with an infrared lamp to obtain a polypyrrole modified electrode. Then, the polypyrrole modified electrode was used as the working electrode, the saturated calomel electrode was used as the reference electrode, the platinum electrode was used as the counter electrode, and 2 mol L ^-1 H ₂ SO ₄ was used as the electrolyte. Cyclic voltammetry was performed on the polypyrrole through the electrochemical workstation. Test and constant current charge and discharge test. According to the galvanostatic charge and discharge test chart of polypyrrole in Figure 8, the specific capacitance of polypyrrole when the current density is 1Ag ^-1 can be calculated by formula (b) to be 45F g ^-1 .

Comparative example 2:

The preparation of two-dimensional titanium carbide nanosheets includes the following steps:

(1) Dissolve 1g lithium fluoride in 20mL 9mol L ^-1 hydrochloric acid solution, and then slowly add 1g titanium aluminum carbide powder under magnetic stirring. After etching at 35°C for 24 hours, it was centrifuged and washed multiple times with ultrapure water until the pH of the supernatant was approximately 7. The multi-layered two-dimensional titanium carbide aqueous solution was further bubbled with nitrogen for 20 min and then ultrasonicated for 1 h. Centrifuge at 3500 rpm for 1 h, and collect a single layer of two-dimensional titanium carbide colloid as the supernatant. The supernatant was collected in a glass bottle, continuously aerated with nitrogen for 20 min, and then stored in a 4°C refrigerator. Calculation method for the concentration of two-dimensional titanium carbide colloid: measure 10 mL of the supernatant in a petri dish, freeze-dry and weigh the mass. The concentration is approximately 4.87 mg mL ^-1 .

(2) Disperse the obtained two-dimensional titanium carbide into ultrapure water to obtain a dispersion of 1 mg mL ^-1 . Use a pipette to transfer 5 μL dropwise onto the surface of the electrode and dry it with an infrared lamp to obtain two-dimensional titanium carbide. Modify the electrode. Then, the two-dimensional titanium carbide modified electrode was used as the working electrode, the saturated calomel electrode was used as the reference electrode, the platinum electrode was used as the counter electrode, and 2 mol L ^-1 H ₂ SO ₄ was used as the electrolyte. The two-dimensional titanium carbide was analyzed through the electrochemical workstation. Carry out cyclic voltammetry test and galvanostatic charge and discharge test. According to the galvanostatic charge and discharge test chart of two-dimensional titanium carbide in Figure 8, the specific capacitance of two-dimensional titanium carbide is 62F g ^-1 when the current density is 1Ag ^-1 and can be calculated through formula (b).

The above are only the preferred embodiments of the present invention. It should be pointed out that those of ordinary skill in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (9)

1. The preparation method of the polypyrrole/two-dimensional titanium carbide/sodium alginate aerogel composite material is characterized by adopting a one-pot method to prepare the polypyrrole/two-dimensional titanium carbide/sodium alginate/calcium carbonate hydrogel composite material, freeze-drying, and completely etching surface calcium carbonate particles of the polypyrrole/two-dimensional titanium carbide/sodium alginate/calcium carbonate hydrogel composite material by adopting hydrochloric acid to obtain the polypyrrole/two-dimensional titanium carbide/sodium alginate aerogel composite material with a three-dimensional porous structure;

specifically, the preparation method comprises the following steps:

(1) Weighing sodium alginate, adding the sodium alginate into ultrapure water, magnetically stirring, adding pyrrole, uniformly stirring to form sol, adding single-layer two-dimensional titanium carbide and calcium carbonate particles, magnetically stirring, slowly dropwise adding ammonium persulfate solution, magnetically stirring to form black gel, and standing in a refrigerator at 4 ℃ until pyrrole is completely polymerized;

(2) Freeze-drying, soaking in hydrochloric acid solution to completely etch calcium carbonate particles, repeatedly cleaning with ultrapure water, and freeze-drying to obtain the three-dimensional porous polypyrrole/two-dimensional titanium carbide/sodium alginate aerogel composite material;

the mass ratio of the sodium alginate to the pyrrole to the single-layer two-dimensional titanium carbide to the calcium carbonate particles is 0.1-0.5 g to 0.2-0.3 g to 20-30 mg to 1-120 mg, the mass ratio of the sodium alginate to the ultrapure water to the ammonium persulfate solution to the volume ratio is 0.1-0.5 g to 5-15 mL to 0.1-1.5 mL, and the concentration of the ammonium persulfate solution is 1.5-2.5 mol L ^‒1 ；

The magnetic stirring time is 2-5 h, and the concentration of the hydrochloric acid is 0.1-1 mol L ^‒1 The etching time is 1-3 h.

2. The preparation method according to claim 1, wherein the preparation process of the single-layer two-dimensional titanium carbide specifically comprises the following steps: weighing lithium fluoride, dissolving in hydrochloric acid solution, slowly adding titanium aluminum carbide under magnetic stirring, etching at room temperature, centrifugally washing with ultrapure water for several times until the pH of the supernatant is 6.8-7.2, collecting multilayer two-dimensional titanium carbide supernatant, introducing nitrogen for bubbling, performing ultrasonic treatment, centrifuging, collecting single-layer two-dimensional titanium carbide colloid supernatant, continuously introducing nitrogen, and storing in a refrigerator at 4 ℃.

3. The preparation method according to claim 2, wherein the mass to volume ratio of the lithium fluoride, the hydrochloric acid solution and the titanium aluminum carbide is 0.1-2 g:15-25 mL:0.1-2 g, and the concentration of the hydrochloric acid solution is 5-10 mol L ^‒1 The method comprises the steps of carrying out a first treatment on the surface of the The etching time of the titanium aluminum carbide is 20-30 h, and the time of introducing nitrogen is 15-30 min.

4. The method of claim 2, wherein the mass to volume ratio of lithium fluoride, hydrochloric acid solution, and titanium aluminum carbide is 1g:20ml:1g.

5. The preparation method according to claim 1, wherein the preparation process of the calcium carbonate particles specifically comprises: measuring an equal volume of a calcium chloride solution and a sodium carbonate solution with equal concentration, placing the calcium chloride solution and the sodium carbonate solution into a mixed solution of water and glycol, magnetically stirring the mixture for 20 to 40 minutes, sequentially and continuously centrifugally washing the mixture by ethanol, methanol and acetone, collecting precipitates, namely calcium carbonate particles, and drying the precipitates.

6. The process according to claim 5, wherein the concentration of the calcium chloride solution and the sodium carbonate solution is 0.05 to 0.2mol L ^‒1 The volumes of the calcium chloride solution and the sodium carbonate solution are 30-60 mL; the volume ratio of the water to the glycol is 1:2-15, and the drying temperature is 50-to-50%100℃。

7. The method according to claim 5, wherein the concentration of the calcium chloride solution and the sodium carbonate solution is 0.1mol L ^‒1 。

8. A polypyrrole/two-dimensional titanium carbide/sodium alginate aerogel composite material, characterized in that the polypyrrole/two-dimensional titanium carbide/sodium alginate aerogel composite material is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the polypyrrole/two-dimensional titanium carbide/sodium alginate aerogel composite material as described in claim 8 as an electrode material for super capacitors.