MXene / PPy-Fe < 2 + > aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to MXene / PPy-Fe < 2 + > aerogel as well as a preparation method and application thereof. The preparation method disclosed by the invention comprises the following steps: etching Ti3AlC2 to obtain an MXene colloidal solution; adding pyrrole and a solvent into the MXene colloidal solution, and stirring to obtain a mixed solution; dropwise adding the cooled APS solution into the cooled mixed solution to form MXene / PPy hydrogel, and carrying out impurity removal and freeze drying to obtain MXene / PPy aerogel; and soaking the MXene / PPy aerogel in a Fe < 2 + > ion solution, and drying to obtain the MXene / PPy-Fe < 2 + > aerogel. When the MXene / PPy-Fe < 2 + > aerogel is used as a particle electrode to be applied to a three-dimensional electrocatalytic oxidation system, the degradation effect on organic pollutants (such as phenol) in wastewater is good, and the cycling stability is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and particularly relates to an MXene / PPy-Fe 2+ aerogel and its preparation method and application. Background Art

[0002] Phenol is one of the common organic pollutants discharged by industries such as refineries, plastics, paper and pulp, pharmaceuticals, and coal processing. It is highly toxic, and even extremely low concentrations of phenol can cause serious pollution to water bodies. It not only seriously damages the environment but also poses a direct threat to human health. Currently, the treatment of phenol-containing wastewater using physical, chemical, and biological methods is time-consuming, expensive, and prone to secondary pollution.

[0003] Two-dimensional electrocatalytic oxidation technology (2DEF) refers to the in-situ continuous generation of H2O2 through an oxygen reduction reaction (ORR) at the cathode through an electrochemical reaction. During this process, ·O 2- with strong oxidation ability is generated. H2O2 is further activated by Fe 2+ to generate ·OH, and these free radicals play a key role in pollutant degradation. Three-dimensional electrocatalytic oxidation technology (3DEF) is an improvement and innovation based on two-dimensional electrocatalytic oxidation technology. It has the advantages of simple operation, good degradation effect, and high energy utilization rate, and is widely studied and used. Three-dimensional electrocatalytic oxidation technology introduces granular or debris-like conductive materials between the anode and cathode plates of two-dimensional electrodes. Under the action of an external power source, the filled conductive particles will be polarized to form many charged microelectrodes, thus becoming many independent degradation units. These filled particles or bulk materials are called particle electrodes or three-dimensional electrodes. Compared with traditional two-dimensional electrode electrolysis technology, three-dimensional electrode electrolysis technology has more active sites in the electrolytic cell due to the introduction of particle electrodes, enhancing the mass transfer efficiency of the current, and thus having higher sewage treatment efficiency. The ideal electrode material (particle electrode) for this technology should have capabilities such as high specific capacity, high electrical conductivity, good cycle stability performance, and high transmission rate.

[0004] MXene materials are metal carbides, nitrides, and carbonitrides with a two-dimensional layered structure. They have advantages such as high electrical conductivity, surface hydrophilicity, and processability, and have become highly potential electrode active materials. However, currently, MXene aerogels are affected by disadvantages such as poor cycle stability and easy oxidation, which affect their service life.

[0005] How to improve the stability of MXene aerogels as electrode materials for degrading wastewater is a technical problem that needs to be seriously studied by those skilled in the art.

[0006] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies of the prior art. Summary of the Invention

[0007] The object of the present invention is to provide an MXene / PPy-Fe 2+ aerogel and its preparation method and application, which helps to improve the degradation effect or service life of organic pollutants in wastewater when the MXene aerogel is applied as a particle electrode to a three-dimensional electrocatalytic oxidation system.

[0008] To achieve the above object, the present invention provides the following technical solution: A preparation method of an MXene / PPy-Fe 2+ aerogel, comprising the following steps: S1. Etch Ti3AlC2 with an etchant, after the etching is completed, perform solid-liquid separation, wash the obtained solid until the pH is neutral, and ultrasonically disperse the obtained solid in ice bath in water to obtain an MXene colloidal solution; S2. Add pyrrole and a solvent to the MXene colloidal solution, and stir to obtain a mixed solution; S3. Drop the cooled ammonium persulfate solution into the cooled mixed solution to form an MXene / PPy hydrogel, and after impregnation for impurity removal and freeze-drying treatment, obtain an MXene / PPy aerogel; S4. Immerse the MXene / PPy aerogel in an Fe 2+ ion solution, and after the immersion is completed, dry it to obtain the MXene / PPy-Fe 2+ aerogel.

[0009] Preferably, in step S2, the volume ratio of the pyrrole to the MXene colloidal solution is (1-1.5):10, and the concentration of the MXene colloidal solution is 20-25 mg / mL; the volume ratio of the solvent to the MXene colloidal solution is 1:1.

[0010] Preferably, the solvent is at least one of anhydrous ethanol, deionized water and isopropanone.

[0011] Preferably, in step S3, the volume ratio of the ammonium persulfate solution to the pyrrole is 10:1, and the concentration of the ammonium persulfate solution is 1-2 mol / L; the temperature of the cooled ammonium persulfate solution and / or the mixed solution is 1-5 °C.

[0012] Preferably, in step S3, the MXene / PPy hydrogel is impregnated with an impregnating solution, and the impregnating solution is replaced every 24 h during the impregnation process until the supernatant becomes clear; the impregnating solution is a mixed solution of water and ethanol, and the volume ratio of water to anhydrous ethanol is (10-20):1.

[0013] Preferably, in step S4, the concentration of the Fe 2+ ion solution is 0.1-1 mol / L, and the impregnation time of the MXene / PPy aerogel in the Fe 2+ ion solution for one time is 4-6 h;

[0014] Preferably, in step S4, the MXene / PPy aerogel is impregnated in an Fe 2+ ion solution and dried twice; after the first drying, the MXene / PPy aerogel is impregnated in the Fe 2+ ion solution again. After the second impregnation, drying gives the MXene / PPy-Fe 2+ aerogel.

[0015] More preferably, the Fe 2+ ion solution is an FeCl2 solution; the mass ratio of Fe 2+ in the FeCl2 solution to the MXene / PPy aerogel is (0.5 - 4):1.

[0016] Preferably, in step S1, the components of the etchant include LiF and hydrochloric acid solution, and the mass ratio of LiF to Ti3AlC2 is (1 - 2):1; the concentration of the hydrochloric acid solution is 12 mol / L, and the concentration of LiF in the etchant is 0.05 - 0.1 g / mL; in step S1, the etching temperature is 30 - 50 °C, the etching time is 24 - 48 h, and the etching is carried out under stirring conditions.

[0017] Preferably, in step S1, the temperature of the ice bath is 0 - 10 °C; during ultrasonic dispersion, the frequency of the ultrasonic wave is 30 - 50 kHz, and the ultrasonic dispersion time is 20 - 40 min; after ultrasonic dispersion, it further includes a step of centrifugal separation to obtain the upper black liquid.

[0018] The present invention also provides an MXene / PPy-Fe 2+ aerogel, which adopts the following technical solution: an MXene / PPy-Fe 2+ aerogel, and the MXene / PPy-Fe 2+ aerogel is prepared by the method as described above.

[0019] The present invention also provides an application of the MXene / PPy-Fe 2+ aerogel, which adopts the following technical solution: the application of the MXene / PPy-Fe 2+ aerogel as described above in the three-dimensional electrocatalytic oxidation degradation of organic pollutants.

[0020] Preferably, the organic pollutant is phenol.

[0021] Beneficial effects:

[0022] In view of the disadvantage of poor cycle stability of MXene aerogel itself, MXene and PPy are prepared into a three-dimensional conductive MXene / PPy aerogel with a stable structure by a one-step freeze-drying method. Finally, the active site Fe 2+ is loaded onto the MXene / PPy aerogel to obtain MXene / PPy-Fe 2+ aerogel. Based on the structural characteristics of MXene aerogel and PPy and their respective requirements, Fe 2+ is attached to the MXene / PPy aerogel substrate. On the basis of ensuring the structural integrity of both, a synergistic effect is exerted, thereby further improving the electrochemical performance when it is used as a three-dimensional electrocatalytic oxidation electrode material.

[0023] In the present invention, MXene is used as the matrix, pyrrole is used as the functional monomer, and ammonium persulfate (APS) is added as the initiator. A three-dimensional conductive MXene / PPy aerogel with a stable structure is prepared by a one-step freeze-drying method. Then, the obtained MXene / PPy aerogel is put into an FeCl2 solution for impregnation and drying treatment to synthesize MXene / PPy-Fe 2+ aerogel.

[0024] The MXene / PPy-Fe 2+ aerogel prepared by the preparation method of the present invention is a three-dimensional porous material. PPy is uniformly attached to the MXene sheets in a granular form. PPy and the MXene sheets support each other to form an interconnected three-dimensional network structure. Moreover, the MXene / PPy-Fe 2+ aerogel prepared by the present invention is applied to a three-dimensional electrocatalytic oxidation system and has excellent degradation ability and long cycle stability. Description of the Drawings

[0025] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Among them:

[0026] Figure 1 is the SEM image of the MXene / PPy-Fe 2+ aerogel prepared in Example 1 of the present invention (from left to right, the scales are 10μm, 1μm and 100nm in sequence);

[0027] Figure 2 is the SEM image of the MXene aerogel of Comparative Example 1;

[0028] Figure 3 is the SEM image of the MXene-Fe 2+ aerogel of Comparative Example 2;

[0029] Figure 4 The MXene / PPy-Fe prepared in Example 1 of the present invention 2+ X-ray diffraction intensity patterns of the aerogel, the MXene aerogel of Comparative Example 1, and the MXene / PPy aerogel of Comparative Example 3;

[0030] Figure 5 Schematic diagram of the phenol degradation experiment;

[0031] Figure 6 The MXene / PPy-Fe prepared in Example 1 of the present invention 2+ Comparison diagram of the degradation effects of the aerogel of the MXene / PPy-Fe prepared in Example 1 of the present invention and the aerogels of Comparative Examples 1, 2, and 3 as particle electrodes applied to the three-dimensional electrocatalytic oxidation system and the two-dimensional electrocatalytic oxidation system (i.e., without adding particle electrodes; represented by "2D" in the figure) for degrading phenol;

[0032] Figure 7 The MXene / PPy-Fe prepared in Example 1 of the present invention 2+ Test result diagram of the cyclic stability of the MXene / PPy-Fe aerogel during the three-dimensional electrocatalytic oxidation process;

[0033] Figure 8 For different Fe 2+ The MXene / PPy-Fe prepared with different mass ratios of Fe to MXene / PPy 2+ Comparison diagram of the degradation effects of the aerogel as a particle electrode applied to the three-dimensional electrocatalytic oxidation system and the two-dimensional electrocatalytic oxidation system (i.e., without adding particle electrodes; represented by "2D" in the figure) for degrading phenol;

[0034] Figure 9 The MXene-Fe of Comparative Example 2 2+ Test result diagram of the cyclic stability of the MXene-Fe aerogel during the three-dimensional electrocatalytic oxidation process.

[0035] Figure 10 Comparison diagram of the degradation effects of the aerogels of Comparative Example 2 and Comparative Examples 4-9 as particle electrodes applied to the three-dimensional electrocatalytic oxidation system and the two-dimensional electrocatalytic oxidation system (i.e., without adding particle electrodes; represented by "2D" in the figure) for degrading phenol;

[0036] Figure 11 The SEM image of the MXene / PPy-Fe aerogel of Example 2 2+ ;

[0037] Figure 12 The physical picture of the MXene / OG-Fe aerogel of Comparative Example 10 2+ ; Detailed implementation manners

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0039] The present invention will be described in detail below with reference to the embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0040] Aiming at the problems of poor degradation effect on organic pollutants in wastewater or poor cycling performance when MXene aerogel is applied as a particle electrode to a three-dimensional electrocatalytic oxidation system, the present invention provides a preparation method of MXene / PPy-Fe 2+ aerogel.

[0041] The inventors found in the research that polypyrrole (PPy) is a typical conductive polymer with low density and good environmental stability. As a C, N five-membered heterocyclic molecule, PPy has many N-H bonds, which helps to form hydrogen bonds with the oxygen or fluorine groups present on the surface of MXene. At the same time, some oligomers formed during the polymerization of pyrrole monomers have opposite charges to the surface of MXene. Therefore, under the synergistic action of hydrogen bonds and electrostatic forces, PPy can be promoted to be uniformly arranged on the surface of MXene, and thus a conductive aerogel with a stable structure can be constructed; however, the stable structure of PPy has no advantage in mass transfer, so it is necessary to add the active substance Fe 2+ , and at the same time introduce a multi-dimensional structure to improve the performance in terms of mass transfer.

[0042] The preparation method of the MXene / PPy-Fe 2+ aerogel in the embodiments of the present invention includes the following steps: S1 Etch Ti3AlC2 with an etchant, separate the solid and liquid after etching, wash the obtained solid until the pH is neutral, and ultrasonically disperse the obtained solid in ice bath in water to obtain a MXene colloidal solution; S2 Add pyrrole and a solvent to the MXene colloidal solution, stir to obtain a mixed solution; S3 Drop the cooled ammonium persulfate solution into the cooled mixed solution to form a MXene / PPy hydrogel. After impregnation for impurity removal (the purpose of this impregnation treatment is to remove the by-products generated by the polymerization reaction initiated by ammonium persulfate; for example, a mixed solution of water and absolute ethanol can be used for impregnation) and freeze-drying treatment, a MXene / PPy aerogel is obtained; S4 Immerse the MXene / PPy aerogel in an Fe 2+ ion solution, and after impregnation (this impregnation is to make Fe 2+ fully adhere to the required aerogel), dry to obtain MXene / PPy-Fe2+ Aerogel.

[0043] Preferably, the Fe 2+ ion solution is ferrous chloride solution; chloride ions are introduced during the etching of Mxene, and using FeCl2 helps to reduce the introduction of other impurity ions and reduce experimental errors.

[0044] In the present invention, taking MXene as the matrix, pyrrole as the functional monomer, adding ammonium persulfate (APS) as the initiator, a three-dimensional conductive MXene / PPy aerogel with a stable structure is prepared by a one-step freeze-drying method, and then the obtained MXene / PPy aerogel is put into a ferrous ion solution for impregnation and drying treatment to synthesize MXene / PPy-Fe 2+ aerogel. The MXene / PPy-Fe 2+ aerogel prepared by the preparation method of the present invention is a three-dimensional porous material, PPy is uniformly attached to the MXene sheets in a granular form, and PPy and the MXene sheets support each other to form a cross-linked three-dimensional network structure. Moreover, the composite aerogel prepared by the present invention has excellent charge transport performance and good conductivity.

[0045] The MXene / PPy-Fe 2+ In a preferred embodiment of the preparation method of the aerogel of the present invention, in step S2, the volume ratio of pyrrole to the MXene colloidal solution is (1 - 1.5):10 (for example, 1:10, 1.1:10, 1.2:10, 1.3:10, 1.4:10 or 1.5:10), and the concentration of the MXene colloidal solution is 20 - 25 mg / mL (for example, 21 mg / mL, 22 mg / mL, 23 mg / mL, 24 mg / mL or 25 mg / mL); the volume ratio of the solvent (the solvent mainly serves to dissolve Mxene) to the MXene colloidal solution is 1:1.

[0046] Preferably, the solvent is at least one of anhydrous ethanol, deionized water and isopropanone.

[0047] The MXene / PPy-Fe 2+In a preferred embodiment of the preparation method of the aerogel, in step S3, the volume ratio of the ammonium persulfate solution to pyrrole is 10:1, and the concentration of the ammonium persulfate solution is 1-2 mol / L (for example, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2.0 mol / L); the temperature of the cooled ammonium persulfate solution and / or the mixed solution is 1-5 °C (for example, 1 °C, 2 °C, 3 °C, 4 °C or 5 °C). Among them, if too much ammonium persulfate is added, the pyrrole polymerization reaction is too fast, the chain transfer reaction increases, the molecular weight of the generated polypyrrole is lower, and the conductivity is poor, resulting in a decrease in the conductivity of the product; if too little ammonium persulfate is added, the pyrrole polymerization reaction is incomplete, the yield of polypyrrole decreases, resulting in a higher degree of oxidation of MXene and a decrease in the adsorption capacity. If the temperature of the ammonium persulfate solution and / or the mixed solution is too high, the pyrrole polymerization reaction is too fast, side reactions increase, the molecular weight of the generated polypyrrole is lower, and the conductivity becomes poor, resulting in a decrease in the conductivity of the product; if the temperature of the ammonium persulfate solution / or the mixed solution is too low, the pyrrole polymerization reaction is incomplete, the yield of polypyrrole decreases, resulting in a higher degree of oxidation of Mxene and a decrease in the adsorption capacity.

[0048] Preferably, the cooling time of the ammonium persulfate solution and / or the mixed solution is 15-45 min (for example, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min or 45 min).

[0049] MXene / PPy-Fe of the present invention 2+ In a preferred embodiment of the preparation method of the aerogel, in step S3, the MXene / PPy hydrogel is impregnated with an impregnating solution, and the impregnating solution is replaced every 24 h during the impregnation process until the supernatant becomes clear; the impregnating solution is a mixed solution of water and ethanol, and the volume ratio of water to absolute ethanol is (10-20):1 (for example, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1).

[0050] Preferably, in step S3, freeze-drying is carried out in a vacuum freeze-dryer; the temperature of freeze-drying is -85 °C to -75 °C (for example, -85 °C, -82 °C, -80 °C, -78 °C or -75 °C), the vacuum degree is 1-3 Pa (such as 1 Pa, 1.5 Pa, 2 Pa, 2.5 Pa or 3 Pa), and the freeze-drying time is 40-50 h (such as 40 h, 42 h, 45 h, 48 h or 50 h)

[0051] MXene / PPy-Fe of the present invention 2+ In a preferred embodiment of the preparation method of the aerogel, in step S4, Fe 2+The concentration of the ionic solution is 0.1 - 1 mol / mL (for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L or 1.0 mol / L), and the MXene / PPy aerogel is immersed in Fe 2+ The time for the MXene / PPy aerogel to be immersed in the ionic solution once is 4 - 6 h. Among them, if the immersion time of the MXene / PPy aerogel in the FeCl2 solution is too short, the ferrous ions will not be completely attached to the MXene / PPy aerogel, resulting in a decrease in conductivity; if the immersion time of the MXene / PPy aerogel in the FeCl2 solution exceeds 6 h, the concentration of the attached ferrous ions hardly changes.

[0052] Preferably, in step S4, the step of immersing the MXene / PPy aerogel in Fe 2+ the ionic solution and drying is carried out twice; after the first drying, the MXene / PPy aerogel is immersed in Fe 2+ the ionic solution again, and after the second immersion, drying is carried out to obtain the MXene / PPy-Fe 2+ aerogel.

[0053] More preferably, the Fe 2+ ionic solution is FeCl2 solution; the mass ratio of Fe 2+ in the FeCl2 solution to the MXene / PPy aerogel is (0.5 - 4):1. Among them, when the mass ratio of Fe 2+ in the FeCl2 solution to the MXene / PPy aerogel is (0.5 - 4):1, when the prepared MXene / PPy-Fe 2+ aerogel is applied to the degradation of phenol, most of the phenol can be degraded within 60 min, and the degradation rate can reach more than 84%, and even complete degradation of phenol can be achieved.

[0054] Further preferably, the mass ratio of Fe 2+ in the FeCl2 solution to the MXene / PPy aerogel is 2:1. Among them, when the mass ratio of Fe 2+ in the FeCl2 solution to the MXene / PPy is less than 2:1, due to the small amount of FeCl2 as a crosslinking agent, the formed MXene-Fe 2+ aerogel skeleton is not stable enough, resulting in inevitable phenomena of bulk collapse and fragmentation during the operation of the MXene-Fe 2+ aerogel as a particle electrode, and the degradation rate of phenol decreases. As the Fe 2+When the mass ratio of [substance] to MXene / PPy increases from 2:1 to 4:1, the degradation rate of phenol also continuously decreases. This is due to an excessive amount of cross-linking agent. Excessive FeCl2 will cause an excessive cross-linking effect on the MXene sheets, resulting in severe stacking of the MXene sheets and significantly reducing the surface utilization rate of the MXene-Fe 2+ aerogel, and the degradation rate of phenol decreases; The Fe in FeCl2 2+ The optimal dosage ratio of [substance] to MXene / PPy is 2:1.

[0055] Preferably, in step S4, the drying is carried out in a vacuum drying oven. The drying temperature is 60 - 100 °C (for example, 60 °C, 70 °C, 80 °C, 90 °C or 100 °C), and the drying time is 4 - 8 h (for example, 4 h, 5 h, 6 h, 7 h or 8 h).

[0056] The MXene / PPy-Fe of the present invention 2+ In a preferred embodiment of the preparation method of the aerogel, in step S1, the components of the etching agent include LiF and hydrochloric acid solution. The mass ratio of LiF to Ti3AlC2 is (1 - 2):1 (for example, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1 or 2.0:1). Among them, if the dosage of LiF is too much, the etching reaction will be too violent, which may damage the MXene layered structure, increase vacancy defects at the same time, and reduce mechanical properties and electrochemical stability; if the dosage of LiF is too little, the etching reaction is insufficient, and the Al layer may not be removed, resulting in poor conductivity.

[0057] Preferably, the concentration of the hydrochloric acid solution is 12 mol / L, and the concentration of LiF in the etching agent is 0.05 - 0.1 g / mL (for example, 0.05 g / mL, 0.06 g / mL, 0.07 g / mL, 0.08 g / mL, 0.09 g / mL or 0.1 g / mL).

[0058] The MXene / PPy-Fe of the present invention 2+ In a preferred embodiment of the preparation method of the aerogel, in step S1, the etching temperature is 30 - 50 °C (for example, 30 °C, 35 °C, 40 °C, 42 °C, 45 °C, 48 °C or 50 °C), the etching time is 24 - 48 h (for example, 24 h, 30 h, 36 h, 42 h or 48 h), and the etching is carried out under stirring conditions. Among them, the etching needs to be carried out at a moderate temperature and time to ensure that the Al layer is completely removed and the MXene structure is intact; if the etching temperature is too high or the time is too long, it may cause excessive peeling of the MXene layer, damage its layered structure, and even produce fragments, reducing its electrical conductivity; if the etching temperature is too low or the time is too short, it may cause the Al layer not to be completely removed, affecting the quality of MXene and thus affecting subsequent use.

[0059] MXene / PPy-Fe of the present invention 2+ In a preferred embodiment of the preparation method of the aerogel, in step S1, the temperature of the ice bath is 0-10°C (for example, 0°C, 2°C, 5°C, 8°C or 10°C); when ultrasonically dispersing, the frequency of the ultrasonic wave is 30-50 kHz (for example, 30 kHz, 35 kHz, 40 kHz, 45 kHz or 50 kHz), and the time of ultrasonic dispersion is 20-40 min (for example, 20 min, 25 min, 30 min, 35 min or 40 min); after the ultrasonic dispersion is completed, it further includes the step of centrifugal separation to obtain the upper black liquid.

[0060] The present invention also provides a kind of MXene / PPy-Fe 2+ aerogel, and the MXene / PPy-Fe 2+ aerogel in the embodiment of the present invention is prepared by the method as described above.

[0061] The present invention also provides an application of MXene / PPy-Fe 2+ aerogel, and the application of the MXene / PPy-Fe 2+ aerogel (used as a particle electrode) in the three-dimensional electrocatalytic oxidation for degrading organic pollutants.

[0062] In a preferred embodiment of the application of the present invention, the organic pollutant is phenol.

[0063] The following further elaborates on the MXene / PPy-Fe 2+ aerogel of the present invention, its preparation method and application through specific examples.

[0064] The raw materials used in the following examples can be commercially available without special instructions; the sources of the main raw materials are as follows: Ti3AlC2, solid, 400 mesh; concentrated hydrochloric acid, 12 mol / L; lithium fluoride, solid, purity 99%; absolute ethanol, purity 99.7%; ferrous chloride tetrahydrate, purity 98%; pyrrole, purity 99%; ammonium persulfate, purity 99%.

[0065] Example 1

[0066] The preparation method of the MXene / PPy-Fe 2+ aerogel in this example includes the following steps:

[0067] Step S1, etching Ti3AlC2 with an etchant, separating the solid and liquid after etching, washing the obtained solid until the pH is neutral, and ultrasonically dispersing the obtained solid in ice bath in water to obtain a MXene colloidal solution; specifically:

[0068] Step S11: Weigh 3.2 g ± 0.001 g of LiF on an analytical balance. Subsequently, stir LiF and 40 mL ± 0.0001 mL of HCl (12 mol / L) in a polytetrafluoroethylene (PTFE) beaker at room temperature (to obtain an etchant). Then, slowly add 2 g ± 0.001 g of Ti3AlC2 powder to the etchant, and magnetically stir it in a constant temperature water bath at 40°C ± 2°C for 48 h;

[0069] Step S12: Place the product obtained after the etching reaction in Step S11 in a centrifuge for centrifugation. Set the centrifugation speed to 5000 rpm. After centrifugation is completed, pour off the supernatant and collect the bottom precipitate;

[0070] Step S13: Wash the precipitate collected in Step S12 with 1 mol / L hydrochloric acid and ultrapure water, then centrifuge and measure the pH value; repeat this process multiple times. Set the centrifugation speed to 5000 rpm until the pH value of the supernatant is close to neutral; then disperse the obtained MXene in ultrapure water, place the beaker on an ultrasonic disperser, and perform ultrasonic treatment in an ice bath; among them, the ice bath temperature is 2°C ± 1°C, the ultrasonic frequency of ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 30 min;

[0071] Step S14: After ultrasonic dispersion, place the MXene dispersion in a centrifuge for centrifugation. Set the centrifugation speed to 3500 rpm. After centrifugation is completed, collect the upper black liquid to obtain the MXene colloidal solution (20 mg / mL).

[0072] Step S2: Add 0.105 mL ± 0.0001 mL of Py and 1 mL ± 0.0001 mL of absolute ethanol to the prepared 1 mL ± 0.0001 mL of MXene solution, and stir at room temperature for 24 h to mix them evenly to obtain a mixed solution;

[0073] Step S3: Weigh 0.34 g ± 0.0001 g of APS, measure 1 mL ± 0.0001 mL of ultrapure water, and stir it in a beaker to dissolve it to obtain an APS solution;

[0074] Step S4: Simultaneously place the mixture obtained in Step S2 and the APS solution obtained in Step S3 in an environment at 3°C and cool for 30 min (cool to 3°C); drop the APS solution into the mixed solution of MXene and Py, and the MXene / PPy hydrogel is rapidly formed. Immerse the prepared MXene / PPy hydrogel in a mixed solution of water and absolute ethanol (the volume ratio of water to absolute ethanol is 15:1) for several days (change the solution every 24 h) until the supernatant becomes clear; place the treated MXene / PPy hydrogel in a vacuum freeze dryer for vacuum freeze drying (the temperature of freeze drying is set at -80°C, the vacuum degree is 2 Pa, and the freeze drying time is 48 h) to obtain the MXene / PPy aerogel;

[0075] Step S5: Weigh 5 g ± 0.001 g of FeCl2·4H2O solid on an analytical balance and dissolve it in 50 mL ± 0.0001 mL of ultrapure water. Immerse the MXene / PPy aerogel (the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 2:1) in the prepared 0.5 mol / L FeCl2 solution for 6 h, and then place it in a vacuum oven at 60°C for drying for 6 h; through two impregnation and drying treatments (that is, place the solid after the first drying in the 0.5 mol / L FeCl2 solution for impregnation treatment for 6 h again, and place it in a vacuum oven at 60°C for drying for 6 h after the second impregnation), the MXene / PPy-Fe 2+ aerogel of this example is obtained. 2+

[0076] Example 2

[0077] The preparation method of the MXene / PPy-Fe 2+ aerogel of this example includes the following steps:

[0078] Step S1: Etch Ti3AlC2 with an etchant, separate the solid and liquid after etching, wash the obtained solid until the pH is neutral, and ultrasonically disperse the obtained solid in ice bath in water to obtain the MXene colloidal solution; specifically:

[0079] Step S11: Weigh 3.2 g ± 0.001 g of LiF on an analytical balance, then stir LiF and 40 mL ± 0.0001 mL of HCl (12 mol / L) at room temperature in a polytetrafluoroethylene (PTFE) beaker (to obtain the etchant), and then slowly add 2 g ± 0.001 g of Ti3AlC2 powder to the etchant, and stir magnetically in a constant temperature water bath at 40°C ± 2°C for 48 h;

[0080] ​Step S12: Place the product obtained after the etching reaction in Step S11 in a centrifuge for centrifugation. Set the centrifugation speed to 5000 rpm. After centrifugation is completed, pour off the supernatant and collect the precipitate at the bottom.

[0081] Step S13: Wash the precipitate collected in Step S12 with 1 mol / L hydrochloric acid and ultrapure water, then centrifuge and measure the pH value. Repeat this process multiple times. Set the centrifugation speed to 5000 rpm until the pH value of the supernatant is close to neutral. Then disperse the obtained MXene in ultrapure water, place the beaker on an ultrasonic disperser, and perform ice bath ultrasonic treatment. Among them, the ice bath temperature is 2°C ± 1°C, the ultrasonic frequency of ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 30 min.

[0082] Step S14: After ultrasonic dispersion, place the MXene dispersion in a centrifuge for centrifugation. Set the centrifugation speed to 3500 rpm. After centrifugation is completed, collect the upper black liquid to obtain an MXene colloidal solution (20 mg / mL).

[0083] Step S2: Add 0.0525 mL ± 0.0001 mL of Py and 1 mL ± 0.0001 mL of absolute ethanol to the prepared 0.5 mL ± 0.0001 mL MXene solution, and stir at room temperature for 24 h to make it evenly mixed to obtain a mixed solution.

[0084] Step S3: Weigh 0.34 g ± 0.0001 g of APS, measure 1 mL ± 0.0001 mL of ultrapure water, and stir in a beaker to dissolve it to obtain an APS solution.

[0085] Step S4: Place the mixed solution obtained in Step S2 and the APS solution obtained in Step S3 in an environment at 3°C and cool for 30 min (cool to 3°C). Drop the APS solution into the mixed solution of MXene and Py, and the MXene / PPy hydrogel is quickly formed. Immerse the prepared MXene / PPy hydrogel in a mixed solution of water and absolute ethanol (the volume ratio of water to absolute ethanol is 15:1) for several days (change the solution every 24 h) until the supernatant becomes clear. Place the treated MXene / PPy hydrogel in a vacuum freeze dryer for vacuum freeze drying (the temperature of freeze drying is set to -80°C, the vacuum degree is 2 Pa, and the freeze drying time is 48 h) to obtain an MXene / PPy aerogel.

[0086] Step S5: Weigh 5 g ± 0.001 g of FeCl2·4H2O solid on an analytical balance and dissolve it in 50 mL ± 0.0001 mL of ultrapure water. The MXene / PPy aerogel (Fe in FeCl2·4H2O 2+The mass ratio with MXene / PPy aerogel is 2:1), and it is soaked in the prepared 0.5 mol / L FeCl2 solution for 6 h. After soaking, it is placed in a vacuum oven at 60 °C for drying for 6 h; through two impregnation and drying treatments (that is, the dried solid is placed in the 0.5 mol / L FeCl2 solution again for impregnation treatment for 6 h, and after the second impregnation, it is placed in a vacuum oven at 60 °C for drying for 6 h), MXene / PPy-Fe of this example is obtained 2+ aerogel.

[0087] Example 3

[0088] The preparation method of the MXene / PPy-Fe 2+ aerogel of this example includes the following steps:

[0089] Step S1, etching Ti3AlC2 with an etchant. After the etching is completed, solid-liquid separation is carried out, and the obtained solid is washed until the pH is neutral. The obtained solid is ultrasonically dispersed in water in an ice bath to obtain a MXene colloidal solution; specifically:

[0090] Step S11, weigh 3.2 g ± 0.001 g LiF on an analytical balance. Then, at room temperature, stir LiF and 40 mL ± 0.0001 mL of HCl (12 mol / L) in a polytetrafluoroethylene (PTFE) beaker (to obtain an etchant), and then slowly add 2 g ± 0.001 g of Ti3AlC2 powder to the etchant, and magnetically stir in a constant temperature water bath at 40 °C ± 2 °C for 48 h;

[0091] Step S12, place the product obtained after the etching reaction in step S11 in a centrifuge for centrifugation, and set the centrifugation speed to 5000 rpm. After centrifugation is completed, pour off the supernatant and collect the bottom precipitate;

[0092] Step S13, wash the precipitate collected in step S12 with 1 mol / L hydrochloric acid and ultrapure water, then centrifuge and measure the pH value; repeat this several times, set the centrifugation speed to 5000 rpm until the pH value of the supernatant is close to neutral; then disperse the obtained MXene in ultrapure water, place the beaker on an ultrasonic disperser, and perform ultrasonic treatment in an ice bath; among them, the ice bath temperature is 2 °C ± 1 °C, the ultrasonic frequency of ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 30 min;

[0093] Step S14, after ultrasonic dispersion, place the MXene dispersion in a centrifuge for centrifugation, set the centrifugation speed to 3500 rpm, and after centrifugation is completed, collect the upper black liquid to obtain the MXene colloidal solution (20 mg / mL).

[0094] Step S2: Add 0.105 mL ± 0.0001 mL of Py and 1 mL ± 0.0001 mL of absolute ethanol into the prepared 1.5 mL ± 0.0001 mL of MXene solution, and stir for 24 h at room temperature to mix them evenly, obtaining a mixed solution;

[0095] Step S3: Weigh 0.34 g ± 0.0001 g of APS, measure 1 mL ± 0.0001 mL of ultrapure water, and stir in a beaker to dissolve it, obtaining an APS solution;

[0096] Step S4: Place the mixed solution obtained in Step S2 and the APS solution obtained in Step S3 in an environment at 3 °C and cool for 30 min (cool to 3 °C); drop the APS solution into the mixed solution of MXene and Py, and the MXene / PPy hydrogel is rapidly formed. Immerse the prepared MXene / PPy hydrogel in a mixed solution of water and absolute ethanol (the volume ratio of water to absolute ethanol is 15:1) for several days (replace the solution every 24 h) until the supernatant becomes clear; place the treated MXene / PPy hydrogel in a vacuum freeze dryer for vacuum freeze drying (the temperature of freeze drying is set at -80 °C, the vacuum degree is 2 Pa, and the freeze drying time is 48 h), obtaining an MXene / PPy aerogel;

[0097] Step S5: Weigh 5 g ± 0.001 g of FeCl₂·4H₂O solid on an analytical balance, dissolve it in 50 mL ± 0.0001 mL of ultrapure water, and soak the MXene / PPy aerogel (the mass ratio of Fe in FeCl₂·4H₂O to the MXene / PPy aerogel is 2:1) in the prepared 0.5 mol / L FeCl₂ solution for 6 h. After the soaking is completed, place it in a vacuum oven at 60 °C for drying for 6 h; through two impregnation and drying treatments (that is, place the solid after the first drying in the 0.5 mol / L FeCl₂ solution again for soaking for 6 h, and place it in a vacuum oven at 60 °C for drying for 6 h after the second soaking is completed), obtain the MXene / PPy-Fe 2+ aerogel of this example. 2+

[0098] Example 4

[0099] The difference between this example and Example 1 is only that: in Step S5, the mass ratio of Fe in FeCl₂·4H₂O to the MXene / PPy aerogel is 0.5:1; the rest are the same as Example 1. 2+

[0100] Example 5

[0101] ​​The difference between this comparative example and Example 1 is only that: in step S5, the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 1:1; the rest are the same as in Example 1. 2+ The difference between this comparative example and Example 1 is only that: in step S5, the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 1:1; the rest are the same as in Example 1.

[0102] Example 6

[0103] The difference between this example and Example 1 is only that: in step S5, the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 3:1; the rest are the same as in Example 1. 2+ The difference between this example and Example 1 is only that: in step S5, the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 3:1; the rest are the same as in Example 1.

[0104] Example 7

[0105] The difference between this example and Example 1 is only that: in step S5, the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 4:1; the rest are the same as in Example 1. 2+ The difference between this example and Example 1 is only that: in step S5, the mass ratio of Fe in FeCl2·4H2O to the MXene / PPy aerogel is 4:1; the rest are the same as in Example 1.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing an MXene aerogel, including the following steps:

[0108] Step S1, etching Ti3AlC2 with an etchant, separating the solid and liquid after etching, washing the obtained solid until the pH is neutral, and ultrasonically dispersing the obtained solid in ice bath in water to obtain an MXene colloidal solution; specifically:

[0109] Step S2, weighing 3.2 g ± 0.001 g of LiF on an analytical balance, then stirring LiF and 40 mL ± 0.0001 mL of HCl (12 mol / L) in a polytetrafluoroethylene (PTFE) beaker at room temperature (to obtain an etchant), and then slowly adding 2 g ± 0.001 g of Ti3AlC2 powder to the etchant, and magnetically stirring in a constant temperature water bath at 40°C ± 2°C for 48 h;

[0110] Step S3, centrifuging the product obtained after the etching reaction in step S2, setting the centrifugation speed to 5000 rpm, after centrifugation is completed, pouring off the supernatant and collecting the bottom precipitate;

[0111] Step S4: Wash the precipitate collected in Step S3 with 1 mol / L hydrochloric acid and ultrapure water, then centrifuge and measure the pH value; repeat this process multiple times with a centrifuge speed set at 5000 rpm until the pH value of the supernatant is close to neutral; then disperse the obtained MXene in ultrapure water, place the beaker on an ultrasonic disperser, and perform ultrasonic treatment in an ice bath; where the ice bath temperature is 2°C ± 1°C, the ultrasonic frequency for ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 30 min;

[0112] Step S5: After ultrasonic dispersion, centrifuge the MXene dispersion in a centrifuge with a centrifuge speed set at 3500 rpm. After centrifugation is completed, collect the upper black liquid to obtain an MXene colloidal solution (20 mg / mL).

[0113] Step S6: Freeze-dry the MXene hydrogel in a vacuum freeze dryer. After 48 h of freeze-drying treatment (the freeze-drying temperature is set at -80°C, the vacuum degree is 2 Pa, and the freeze-drying time is 48 h), MXene aerogel is obtained.

[0114] Comparative Example 2

[0115] This comparative example provides a method for preparing MXene-Fe 2+ aerogel, including the following steps:

[0116] Step S1: Etch Ti3AlC2 with an etchant. After the etching is completed, separate the solid and liquid, wash the obtained solid until the pH is neutral, and ultrasonically disperse the obtained solid in water in an ice bath to obtain an MXene colloidal solution; specifically:

[0117] Step S11: Weigh 3.2 g ± 0.001 g of LiF on an analytical balance. Subsequently, stir LiF and 40 mL ± 0.0001 mL of HCl (12 mol / L) in a polytetrafluoroethylene (PTFE) beaker at room temperature (to obtain the etchant), and then slowly add 2 g ± 0.001 g of Ti3AlC2 powder to the etchant, and magnetically stir in a constant temperature water bath at 40°C ± 2°C for 48 h;

[0118] Step S12: Centrifuge the product obtained after the etching reaction in Step S11 in a centrifuge with a centrifuge speed set at 5000 rpm. After centrifugation is completed, pour off the supernatant and collect the bottom precipitate;

[0119] Step S13: Wash the precipitate collected in Step S12 with 1 mol / L hydrochloric acid and ultrapure water, then centrifuge and measure the pH value; repeat this process multiple times, set the centrifuge speed to 5000 rpm until the pH value of the supernatant is close to neutral; then disperse the obtained MXene in ultrapure water, place the beaker on an ultrasonic disperser, and perform ultrasonic treatment in an ice bath; wherein, the ice bath temperature is 2°C ± 1°C, the ultrasonic frequency of ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 30 min;

[0120] Step S14: After ultrasonic dispersion, centrifuge the MXene dispersion liquid in a centrifuge, set the centrifuge speed to 3500 rpm, after centrifugation is completed, collect the upper black liquid to obtain the MXene colloidal solution (20 mg / mL).

[0121] Step S2: Weigh 0.0627 g of FeCl2·4H2O solid on an analytical balance, dissolve it in 0.2 mL of ultrapure water, and perform ultrasonic treatment until the FeCl2·4H2O solid is completely dissolved.

[0122] Step S3: Drop the ultrasonicated solution into the prepared MXene colloidal solution (10 mg / mL, 2 mL; in this comparative example, the mass ratio of Fe in FeCl2·4H2O to MXene colloid is 2:1), and then the MXene-Fe 2+ hydrogel forms rapidly in a short time. 2+

[0123] Step S4: Let the prepared MXene-Fe 2+ hydrogel stand at room temperature for 12 h, and finally freeze-dry the MXene-Fe 2+ aerogel in a vacuum freeze dryer. After 48 h of freeze-drying treatment (the freeze-drying temperature is set at -80°C, the vacuum degree is 2 Pa, and the freeze-drying time is 48 h), the MXene-Fe 2+ aerogel is obtained.

[0124] Comparative Example 3

[0125] This comparative example provides a preparation method of MXene / PPy aerogel, including the following steps:

[0126] Step S1: Etch Ti3AlC2 with an etchant, after the etching is completed, separate the solid and liquid, wash the obtained solid until the pH is neutral, and ultrasonically disperse the obtained solid in water in an ice bath to obtain a MXene colloidal solution; specifically:

[0127] ​Step S11, weigh 3.2 g ± 0.001 g of LiF on an analytical balance. Subsequently, at room temperature, stir LiF and 40 mL ± 0.0001 mL of HCl (12 mol / L) in a polytetrafluoroethylene (PTFE) beaker (to obtain an etching agent). Then, slowly add 2 g ± 0.001 g of Ti3AlC2 powder to the etching agent, and magnetically stir in a constant temperature water bath at 40°C ± 2°C for 48 h;

[0128] Step S12, centrifuge the product obtained after the etching reaction in Step S11 in a centrifuge. Set the centrifuge speed to 5000 rpm. After centrifugation, pour off the supernatant and collect the bottom precipitate;

[0129] Step S13, wash the precipitate collected in Step S12 with 1 mol / L hydrochloric acid and ultrapure water, then centrifuge and measure the pH value; repeat this process multiple times. Set the centrifuge speed to 5000 rpm until the pH value of the supernatant is close to neutral; then disperse the obtained MXene in ultrapure water, place the beaker on an ultrasonic disperser, and perform ultrasonic treatment in an ice bath; among them, the ice bath temperature is 2°C ± 1°C, the ultrasonic frequency of ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 30 min;

[0130] Step S14, after ultrasonic dispersion, centrifuge the MXene dispersion in a centrifuge. Set the centrifuge speed to 3500 rpm. After centrifugation, collect the upper black liquid to obtain an MXene colloidal solution (20 mg / mL).

[0131] Step S2, add 0.105 mL ± 0.0001 mL of Py and 1 mL ± 0.0001 mL of absolute ethanol to the prepared 1 mL ± 0.0001 mL of MXene solution, and stir at room temperature for 24 h to mix evenly to obtain a mixed solution;

[0132] Step S3, weigh 0.34 g ± 0.0001 g of APS, measure 1 mL ± 0.0001 mL of ultrapure water, and stir in a beaker to dissolve it to obtain an APS solution;

[0133] Step S4: Place the mixture obtained in Step S2 and the APS solution obtained in Step S3 in an environment at 3°C and cool for 30 min (cool to 3°C); drop the APS solution into the mixed solution of MXene and Py, and the MXene / PPy hydrogel is rapidly formed. Immerse the prepared MXene / PPy hydrogel in a mixed solution of water and absolute ethanol (the volume ratio of water to absolute ethanol is 15:1) for several days (change the solution every 24 h) until the supernatant becomes clear; place the treated MXene / PPy hydrogel in a vacuum freeze dryer for vacuum freeze drying (the temperature of freeze drying is set at -80°C, the vacuum degree is 2 Pa, and the freeze drying time is 48 h) to obtain the MXene / PPy aerogel;

[0134] Comparative Example 4

[0135] This comparative example provides a method for preparing MXene-Mg 2+ aerogel: The difference between this comparative example and Comparative Example 2 is only that: Mg 2+ is used to replace Fe 2+ (in Comparative Example 2) (the mass ratio of Mg 2+ to the MXene colloid is 2:1); the rest are the same as in Comparative Example 2.

[0136] Comparative Example 5

[0137] This comparative example provides a method for preparing MXene-Co 2+ aerogel: The difference between this comparative example and Comparative Example 2 is only that: Co 2+ is used to replace Fe 2+ (in Comparative Example 2) (the mass ratio of Co 2+ to the MXene colloid is 2:1); the rest are the same as in Comparative Example 2.

[0138] Comparative Example 6

[0139] This comparative example provides a method for preparing MXene-Ni 2+ aerogel: The difference between this comparative example and Comparative Example 2 is only that: Ni 2+ is used to replace Fe 2+ (in Comparative Example 2) (the mass ratio of Ni 2+ to the MXene colloid is 2:1); the rest are the same as in Comparative Example 2.

[0140] Comparative Example 7

[0141] This comparative example provides a method for preparing MXene-Zn 2+ aerogel: The difference between this comparative example and Comparative Example 2 is only that: Zn 2+ is used to replace Fe 2+ (in Comparative Example 2) (the mass ratio of Zn2+ The mass ratio with the MXene colloid is 2:1); the rest are the same as in Comparative Example 2.

[0142] Comparative Example 8

[0143] This comparative example provides a method for preparing an MXene-Cu 2+ aerogel: The difference between this comparative example and Comparative Example 2 is only that: Cu 2+ is used to replace Fe in Comparative Example 2 2+ (The mass ratio of Cu 2+ to the MXene colloid is 2:1); the rest are the same as in Comparative Example 2.

[0144] Comparative Example 9

[0145] This comparative example provides a method for preparing an MXene-Mn 2+ aerogel: The difference between this comparative example and Comparative Example 2 is only that: Mn 2+ is used to replace Fe in Comparative Example 2 2+ (The mass ratio of Mn 2+ to the MXene colloid is 2:1); the rest are the same as in Comparative Example 2.

[0146] Comparative Example 10

[0147] This comparative example provides a method for preparing an MXene / OG-Fe 2+ aerogel. The difference from Example 1 is that in step S2, an equal amount of OG (graphene oxide) is used to replace Py (pyrrole); the rest are the same as in Example 1.

[0148] The MXene / OG-Fe 2+ aerogel of this comparative example is shown in Figure 12 the figure. OG can form an aerogel skeleton, but after drying, peeling will occur on the surface and it cannot be used as a particle electrode for the degradation of phenol.

[0149] Comparative Example 11

[0150] This comparative example provides a method for preparing an MXene / PVA-Fe 2+ aerogel. The difference from Example 1 is that in step S2, an equal amount of PVA (polyvinyl alcohol) is used to replace Py; the rest are the same as in Example 1.

[0151] PVA can form an aerogel skeleton, but it is not a conductive polymer, and the particle electrode made has very poor conductivity and cannot be used for the degradation of phenol.

[0152] Experimental Example

[0153] For the MXene / PPy-Fe of Example 12+ The morphology, composition, chemical and physical properties of the aerogel were detected, analyzed and characterized. Among them, the high-resolution transmission electron microscope was used for morphological structure analysis; the X-ray diffractometer was used for composition analysis; and its performance was studied by measuring the degradation rate of phenol.

[0154] 1. SEM and XRD tests:

[0155] Figure 1 For MXene / PPy-Fe 2+ SEM image of the aerogel; from Figure 1 it can be seen that MXene / PPy-Fe 2+ aerogel presents a rich network structure, and a large number of spherical and wedge-shaped particles of PPy are very evenly loaded on the surface of MXene sheets, indicating that while PPy polymerizes on the surface of MXene, it also plays a role in connecting MXene sheets.

[0156] Figure 2 SEM image of the MXene aerogel of Comparative Example 1; by observing the SEM image of the MXene aerogel, the MXene aerogel obtained by freeze-drying the pure MXene colloidal solution, although having a certain network structure, still has obvious sheet stacking phenomenon, and this stacking phenomenon reduces the surface utilization rate of the two-dimensional MXene material, making it unable to fully exert the conductive advantage of the MXene material as a particle electrode in the three-dimensional electrocatalytic oxidation process.

[0157] Figure 3 For MXene-Fe of Comparative Example 2 2+ SEM image of the aerogel; by observing the SEM image of the MXene-Fe 2+ aerogel, due to the cross-linking effect between Fe 2+ and the two-dimensional MXene sheets, the MXene sheets are cross-linked with each other, so that the MXene-Fe 2+ aerogel presents a rich porous structure, greatly improving the surface utilization rate of the MXene material. But on the one hand, the MXene sheets are prone to oxidation. While the MXene-Fe 2+ aerogel shows a rich network structure, it also makes the MXene sheets fully exposed, thus exacerbating the oxidation of MXene, resulting in poor conductivity of the particle electrode, reduced catalytic performance and decreased cycle stability.

[0158] Figure 11 SEM image of the MXene / PPy-Fe 2+ aerogel of Example 2. From Figure 11 it can be known that the MXene / PPy-Fe of Example 2 2+The aerogel material has a hierarchical porous structure, and a large number of spherical and wedge-shaped particles of PPy are loaded on the surface of the MXene sheets; the successful synthesis of the aerogel is demonstrated, and phenol in wastewater can be completely removed within 30 minutes.

[0159] Figure 4 For the MXene / PPy-Fe of Example 1 2+ X-ray diffraction intensity patterns of the aerogel, the MXene aerogel of Comparative Example 1, and the MXene / PPy aerogel of Comparative Example 3, from Figure 2 It can be seen that in the MXene / PPy-Fe 2+ aerogel spectrum, the characteristic peak at 2θ = 6.88° corresponds to the (002) crystal plane of MXene. At the same time, an amorphous peak of PPy is also found in the range of 2θ = 15° - 30° in the spectrum, and a typical diffraction peak of FeCl2·2H2O crystals also appears.

[0160] 2. Degradation experiment of phenol

[0161] Test method: A phenol solution obtained by mixing 50 mL of phenol and water is used as simulated industrial wastewater (in the simulated industrial wastewater, the concentration of phenol is 50 mg / L). Under the conditions of an applied voltage of 10 V, the pH of the simulated industrial wastewater = 3, and the dosage of the particle electrode (using the aerogel prepared in the above-mentioned example or comparative example as the particle electrode) is 1.8 g / L, a phenol degradation test is carried out (the schematic diagram of the phenol degradation experiment is as Figure 5 shown). During the experiment, the concentration of phenol in the simulated industrial wastewater is measured every 10 minutes.

[0162] Test results:

[0163] (1) Figure 6 This is a comparison diagram of the degradation effect of the MXene / PPy-Fe 2+ aerogel prepared in Example 1 of the present invention and the aerogels of Comparative Examples 1 - 3 as particle electrodes applied to the three-dimensional electrocatalytic oxidation system and the two-dimensional electrocatalytic oxidation system (that is, no particle electrode is added; represented by "2D" in the figure) for the degradation of phenol.

[0164] From Figure 6 it can be seen that the MXene / PPy-Fe of Example 1 2+When the aerogel is applied as a particle electrode to a three-dimensional electrocatalytic oxidation system, phenol in wastewater can be completely removed within 30 minutes, with a very high degradation rate. When the MXene / PPy aerogel of Comparative Example 3 is used as a particle electrode, the degradation effect on phenol is not as good as that of the pure MXene aerogel of Comparative Example 1. This is because PPy is loaded on the surface of MXene. On the one hand, it is loaded on the surface of MXene sheets, preventing the oxidation of MXene; on the other hand, the conductivity of PPy is not as good as that of MXene, which inevitably reduces the conductivity of MXene, making the conductivity of MXene / PPy aerogel worse than that of MXene aerogel and reducing the polarization effect of the particle electrode.

[0165] (2) Figure 7 For the MXene / PPy-Fe of Example 1 2+ Graph of the cyclic stability test results of the aerogel as a particle electrode during three-dimensional electrocatalytic oxidation.

[0166] From Figure 7 it can be seen that when the MXene / PPy-Fe 2+ aerogel of Example 1 undergoes 5 cycles of degradation, the system maintains an initial degradation rate of more than 80% and has good durability.

[0167] Note: During the cyclic stability test of the MXene / PPy-Fe 2+ aerogel of Example 1, the duration of each degradation experiment is 60 minutes; during the first degradation, when the degradation time is 30 minutes, the degradation rate can reach Figure 7 the effect shown; during each subsequent degradation, at 60 minutes, there is Figure 7 the phenol degradation effect shown.

[0168] (3) Figure 8 For Fe 2+ MXene / PPy-Fe prepared under different mass ratios of Fe to MXene / PPy 2+ Graph comparing the degradation effects of the aerogel as a particle electrode applied to a three-dimensional electrocatalytic oxidation system and a two-dimensional electrocatalytic oxidation system (i.e., without adding a particle electrode; represented by "2D" in the figure) on phenol.

[0169] The specific degradation effects are shown in Table 1 below:

[0170] Table 1

[0171]

[0172] From Figure 8As can be seen from Table 1 above: When the mass ratio of FeCl2·4H2O to MXene / PPy aerogel in Examples 4 - 5 is less than 2:1, since the amount of FeCl2 as a crosslinking agent is small, the formed MXene-Fe 2+ aerogel skeleton is not stable enough, resulting in inevitable block collapse and fragmentation of MXene-Fe 2+ aerogel during the operation as a particle electrode, a decrease in the degradation rate, and complete degradation of phenol only after 60 min; when the mass ratios of FeCl2·4H2O to MXene / PPy aerogel in Examples 6 and 7 are 3:1 and 4:1 respectively, with the increase in the mass ratio of FeCl2 to MXene / PPy, the degradation rate of phenol also continuously decreases; this is due to excessive crosslinking agent. Excessive FeCl2 will cause excessive crosslinking effect on MXene sheets, resulting in serious stacking of MXene sheets and reducing the surface utilization rate of MXene-Fe 2+ aerogel, and the degradation rate decreases, and complete degradation of phenol only after 60 min.

[0173] (4) Figure 9 Figure showing the cyclic stability test results of the MXene-Fe 2+ aerogel of Comparative Example 2 during three-dimensional electrocatalytic oxidation.

[0174] As can be seen from Figure 9 : When the MXene-Fe 2+ aerogel of Comparative Example 2 is applied as a particle electrode to the three-dimensional electrocatalytic oxidation system, the degradation rate of phenol significantly decreases to 75% during the second cycle of use.

[0175] Note: During the cyclic stability test of the MXene-Fe 2+ aerogel of Comparative Example 2, the duration of each degradation experiment is 60 min; during the first degradation, at the degradation time of 50 min, the degradation rate can reach Figure 9 the shown effect; during each subsequent degradation, at 60 min, there is Figure 9 the shown phenol degradation effect.

[0176] (5) Figure 10 Figure showing the MXene-Fe 2+ aerogel of Comparative Example 2 and the MXene-Mg 2+ aerogel, MXene-Co 2+ aerogel, MXene-Ni 2+ aerogel, MXene-Zn 2+ aerogel, MXene-Cu 2+ aerogel, and MXene-Mn 2+Comparison diagram of the degradation effect of aerogel used as a particle electrode in a three-dimensional electrocatalytic oxidation system and a two-dimensional electrocatalytic oxidation system (i.e., without adding a particle electrode; denoted as "2D" in the figure) for phenol degradation.

[0177] The specific degradation effects are shown in Table 2 below:

[0178] Table 2

[0179]

[0180] That is, when the aerogel of Comparative Examples 4-9 is used as a particle electrode in a three-dimensional electrocatalytic oxidation system, the degradation effect on phenol is significantly worse than that of MXene-Fe of Comparative Example 2 2+ aerogel.

[0181] In summary: The MXene / PPy-Fe 2+ aerogel of the present invention is a three-dimensional porous material. PPy is uniformly attached to the MXene sheets in the form of spherical particles. PPy and the MXene sheets support each other to form an interconnected three-dimensional network structure. Moreover, the MXene / PPy-Fe 2+ aerogel prepared by the present invention has excellent degradation ability and long cycle stability.

[0182] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of MXene / PPy-Fe 2+ aerogel, characterized in that It includes the following steps: S1. Etch Ti3AlC2 with an etchant. After the etching is completed, perform solid-liquid separation, wash the obtained solid until the pH is neutral, and ultrasonically disperse the obtained solid in water in an ice bath to obtain an MXene colloidal solution; S2. Add pyrrole and a solvent to the MXene colloidal solution, and stir to obtain a mixture; S3. Drop the cooled ammonium persulfate solution into the cooled mixture to form an MXene / PPy hydrogel. After impregnation for impurity removal and freeze-drying treatment, an MXene / PPy aerogel is obtained; S4. Immerse the MXene / PPy aerogel in an Fe 2+ ion solution, and after the immersion, dry it to obtain the MXene / PPy-Fe 2+ aerogel.

2. The MXene / PPy-Fe 2+ aerogel preparation method, characterized in that In step S2, the volume ratio of the pyrrole to the MXene colloidal solution is (1 - 1.5):10, and the concentration of the MXene colloidal solution is 20 - 25 mg / mL; The volume ratio of the solvent to the MXene colloidal solution is 1:1; Preferably, the solvent is at least one of anhydrous ethanol, deionized water, and isopropanone.

3. The preparation method of the MXene / PPy-Fe 2+ aerogel, characterized in that In step S3, the volume ratio of the ammonium persulfate solution to the pyrrole is 10:1, and the concentration of the ammonium persulfate solution is 1 - 2 mol / L; The temperature of the cooled ammonium persulfate solution and / or the mixture is 1 - 5 °C.

4. The preparation method of the MXene / PPy-Fe 2+ aerogel, characterized in that In step S3, impregnate the MXene / PPy hydrogel with an impregnating solution, and replace the impregnating solution every 24 h during the impregnation process until the supernatant becomes clear; The impregnating solution is a mixed solution of water and ethanol, and the volume ratio of water to anhydrous ethanol is (10 - 20):

1.

5. The preparation method of the MXene / PPy-Fe 2+ aerogel, characterized in that In step S4, the concentration of the Fe 2+ ion solution is 0.1-1 mol / L, and the time for the MXene / PPy aerogel to be impregnated once in the Fe 2+ ion solution is 4-6 h; Preferably, in step S4, the step of impregnating the MXene / PPy aerogel in an Fe 2+ ion solution and drying is carried out twice; after the first drying, the MXene / PPy aerogel is impregnated again in an Fe 2+ ion solution, and after the second impregnation, drying gives the MXene / PPy-Fe 2+ aerogel; More preferably, the Fe 2+ ion solution is an FeCl2 solution; the mass ratio of Fe in the FeCl2 solution 2+ to the MXene / PPy aerogel is (0.5 - 4):

1.

6. The preparation method of the MXene / PPy-Fe 2+ aerogel, characterized in that In step S1, the components of the etchant include LiF and a hydrochloric acid solution, and the mass ratio of LiF to Ti3AlC2 is (1 - 2):1; The concentration of the hydrochloric acid solution is 12 mol / L, and the concentration of LiF in the etchant is 0.05 - 0.1 g / mL; In step S1, the temperature of the etching is 30 - 50 °C, the time of the etching is 24 - 48 h, and the etching is carried out under stirring conditions.

7. The preparation method of the MXene / PPy-Fe 2+ aerogel, characterized in that In step S1, the temperature of the ice bath is 0 - 10 °C; During ultrasonic dispersion, the frequency of the ultrasonic wave is 30 - 50 kHz, and the time of ultrasonic dispersion is 20 - 40 min; After the ultrasonic dispersion is completed, it further includes the step of centrifugal separation to obtain the upper black liquid.

8. A MXene / PPy-Fe 2+ aerogel, characterized in that The MXene / PPy-Fe 2+ aerogel is prepared by the method described in any one of claims 1-7.

9. Application of the MXene / PPy-Fe 2+ aerogel in the three-dimensional electrocatalytic oxidation degradation of organic pollutants.

10. The application according to claim 9, characterized in that, The organic pollutant is phenol.

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