A five-transition metal high-entropy MXene material and its preparation method and application

Abstract

The present invention discloses a preparation method of a five-transition-metal high-entropy MXene material, which comprises the following steps: firstly, constructing a 514-phase high-entropy MAX material (TiVCrNbMo)5AlC4, and then reacting with an etching agent to obtain high-entropy MXene (TiVCrNbMo)5C4T x , and then preparing the high-entropy MXene (TiVCrNbMo)5C4T x into a high-entropy MXene (TiVCrNbMo)5C4T x aerogel, thereby obtaining the five-transition-metal high-entropy MXene material. The five-transition-metal high-entropy MXene material prepared by the present invention has uniform distribution of five metal elements without aggregation. It has a three-dimensional macroporous structure with an irregular shape formed by stacking single-layer or few-layer MXene flakes, a thin pore wall structure, a larger working voltage range, more excellent rate performance, and more excellent ionic and electronic conductivity, and thus has higher conductivity and charge storage capacity. Moreover, the high-entropy MXene electrode material prepared from the five-transition-metal high-entropy MXene material has excellent capacitance and excellent cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and specifically relates to a five-transition metal high-entropy MXene material for supercapacitors, and a preparation method and application thereof. Background Art

[0002] Since its discovery in 2011, two-dimensional layered transition metal carbides (MXenes) have shown broad application prospects in supercapacitors, batteries, and electrocatalysis due to their large interlayer spacing, good conductivity, chemical stability, good hydrophilicity, and adjustable interlayer spacing. The general chemical formula of MXene is M n+1 X n T x , which is obtained by reacting the precursor MAX material with a suitable etchant to selectively etch the A atomic layer. n+1 X n T x In the formula, M represents an early transition metal element; A is a 13-14 group element; X is mainly C; T x Represents the rich functional groups on the surface of MXene. Due to the multiple selectivity of early transition metals, the diversity of etching methods, and the wide range of n values, it has become a hot topic to adjust the composition and atomic structure of MXene to have different physical and chemical properties to meet the needs of multiple fields. The rich composition, excellent conductivity and stability, and easily adjustable surface chemical properties make MXenes very promising for applications in energy storage, catalysts, and electromagnetic shielding. After adjusting the M-site elements, the atomic layer with two or more transition metals exhibits a unique electronic structure (semiconductor or metallic characteristics) accompanied by unique surface terminations. Based on the bi-transition metal structure, the electronic state of the transition metal and the properties of the outer transition metal layer can be changed, and bimetallic MXenes have better conductivity, charge storage capacity, and catalytic activity.

[0003] Similar to high entropy alloys, high entropy MXenes are multi-element materials containing at least five metal elements. Due to its novel "high entropy effect" and excellent performance, it has become one of the research hotspots in the field of materials in recent years. The mixing of multiple main elements in high entropy alloys leads to the maximum mixing entropy of the material. High mixing entropy inhibits the formation of intermetallic compounds and promotes the formation of saturated solid solutions with simple crystal structures. Under the coupling of multiple mechanisms, high entropy alloys have many excellent properties that traditional materials cannot match, such as outstanding performance in mechanics, electromagnetism, high temperature resistance, corrosion resistance, etc. Therefore, high entropy alloys are regarded as one of the key materials that are expected to solve the bottleneck problem of material performance in the current engineering field. However, MXene-based supercapacitors currently have problems such as poor electrode performance, narrow operating voltage range, and short cycle life. And there is currently a lack of examples of applying high entropy MXene to the field of supercapacitors. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the main purpose of the present invention is to provide a five-transition metal high-entropy MXene material and a preparation method thereof, aiming to solve the problems that the preparation method of the existing high-entropy MXene material is single, the purity is not high and it is easy to aggregate, and to expand the types of high-entropy MXene.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] In a first aspect, a method for preparing a five-metal transition high entropy MXene material comprises the following steps:

[0007] 1) High entropy MAX material (TiVCrNbMo) 5 AlC 4 Powder synthesis

[0008] Ti, V, Cr, Nb, Mo, Al and graphite powders were uniformly mixed in a molar ratio of 1:1:1:1:1:1.3:3.5; the uniformly mixed powders were spread in an alumina crucible and then transferred to a tube furnace for sintering at 1400-1600°C. A constant argon flow rate should be maintained throughout the sintering process to prevent the sample from being oxidized. After cooling, the surface of the sintered blank was sanded and ground to obtain a high entropy MAX material (TiVCrNbMo) 5 AlC 4 powder;

[0009] 2) High entropy MXene (TiVCrNbMo) 5 C 4 T x Synthesis

[0010] MAX material (TiVCrNbMo)5 AlC 4 The powder was slowly added to a polytetrafluoroethylene reactor containing 40-50% hydrofluoric acid by mass. The whole process lasted for 60 seconds. High entropy MAX material (TiVCrNbMo) 5 AlC 4 The ratio of powder to hydrofluoric acid solution is 1:10-20 g / mL; react in a water bath at 45-50°C and stir continuously for 60-80 hours; the suspension after the reaction is centrifuged, dispersed and decanted multiple times until the pH of the supernatant is >6, and the MXenes are collected on cellulose filter paper by vacuum filtration and dried at 60°C in vacuum for 24 hours to obtain high entropy MXene (TiVCrNbMo) 5 C 4 T x ;

[0011] 3) High entropy MXene (TiVCrNbMo) 5 C 4 T x Synthesis of aerogel

[0012] Take the high entropy MXene (TiVCrNbMo) obtained in step 2) 5 C 4 T x , added to the intercalant, the mass concentration of the intercalant is 10-15wt%, high entropy MXene (TiVCrNbMo) 5 C 4 T x The ratio of the intercalation agent to the intercalation agent is 1:10-40 g / mL, and the mixture is stirred to obtain a mixture; the mixture is centrifuged for the first time to obtain a precipitate, and the pH value of the supernatant is measured; the precipitate is dispersed with deionized water, centrifuged for the second time, the precipitate is obtained again, and the pH value of the supernatant is measured again; repeat several times, when the pH value of the supernatant is 6.0-8.0, the precipitate is dispersed again with deionized water, ultrasonically treated for 1-2 hours under the action of inert gas bubbling, and centrifuged for the third time to obtain a supernatant, i.e., a few-layer MXene solution; the few-layer MXene solution is freeze-dried for 40-60 hours to obtain a high entropy MXene (TiVCrNbMo) 5 C 4 T x Aerogel is a five-metal transition high-entropy MXene material.

[0013] Preferably, in step 1), during sintering, a programmed temperature increase method is adopted, and the heating rate from room temperature to 1200° C. is 10° C. / min, and the heating rate from 1200° C. to the sintering temperature is 2° C. / min.

[0014] Preferably, in step 1), the high entropy MAX material (TiVCrNbMo)5 AlC 4 The particle size of the powder is 50-100 μm.

[0015] Preferably, in step 2), the stirring speed is 300-500 r / min, the centrifugal speed is 3000-4000 r / min, and the centrifugal time is 3-8 min.

[0016] Preferably, in step 3), the speed of the first centrifugation and the second centrifugation are both 4000-6000 r / min, and the centrifugation time is both 4-6 min; the speed of the third centrifugation is 3000-4000 r / min, and the centrifugation time is 50-70 min.

[0017] Preferably, in step 3), the intercalation agent is any one or more of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and dimethyl sulfoxide.

[0018] Preferably, in step 2), the high entropy MXene (TiVCrNbMo) 5 C 4 T x It presents a multi-layer accordion-like structure, wherein the multi-layer consists of five transition metal layers and four carbon layers; in step 3), the high entropy MXene (TiVCrNbMo) 5 C 4 T x The aerogel is composed of multiple layers of MXene flakes stacked together, presenting an irregularly shaped three-dimensional macroporous structure with an average pore wall thickness of 20 μm.

[0019] In a second aspect, a five-metal transition high entropy MXene material prepared according to the aforementioned preparation method, wherein the molecular formula of the five-metal transition high entropy MXene material is M 5 X 4 T x , wherein M is Ti, V, Cr, Nb and Mo; X represents at least one of carbon, nitrogen or boron; Tx represents a surface functional group, and Tx includes one or more of O, F, Cl, Br, I or OH.

[0020] Preferably, the mass percentage of Ti, V, Cr, Nb and Mo elements in the five-metal transition high entropy MXene material is 5%-30%, and further, the mass percentage of Ti, V, Cr, Nb and Mo elements is 20%;

[0021] In a third aspect, a method for preparing the aforementioned five-transition metal high entropy MXene supercapacitor electrode material comprises the following steps:

[0022] The aforementioned high entropy MXene (TiVCrNbMo)5 C 4 T x The aerogel is mixed with polytetrafluoroethylene (PTFE) adhesive and acetylene black, which is added between MXene sheets to form a conductive network, with a mass ratio of 80:10:10 and dispersed in 0.5-2mL n-methyl-2-pyrrolidone (NMP) solvent; the resulting mixture is homogenized with ultrasound, coated on a conductive carbon cloth substrate, and then dried in a vacuum freeze drying oven for 20-30h to obtain a five-transition metal high-entropy MXene supercapacitor electrode material.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] 1) The five-transition metal high-entropy MXene material provided by the present invention has five different early transition metals. The addition of the five metal elements increases the entropy value of the material, making the crystal structure of the material more stable; the prepared high-entropy MXene aerogel has an irregular three-dimensional macroporous structure formed by the superposition of a single layer or a few layers of MXene flakes, and the thin pore wall structure greatly shortens the diffusion distance of electrolyte ions, significantly optimizes the electrolyte diffusion kinetics, increases the contact area with the electrolyte, and improves the electrochemical performance; at the same time, by changing the electronic state of the metal and the specific characteristics of the outer transition metal layer, and improving the stability of the crystal structure, the high-entropy MXene (TiVCrNbMo) 5 C 4 T x The base supercapacitor electrode exhibits a more stable working state in the electrolyte, that is, it has a larger operating voltage range, better rate performance, and better ionic and electronic conductivity, and thus has higher conductivity and charge storage capacity.

[0025] 2) The preparation method of the five transition metal high entropy MXene material provided by the present invention is to construct a 514 phase high entropy MAX material (TiVCrNbMo) by directly increasing the number of atomic layers 5 AlC 4 , and then react with an etchant to obtain high entropy MXene (TiVCrNbMo) 5 C 4 T x , and then by high entropy MXene (TiVCrNbMo) 5 C 4 T x Preparation of high entropy MXene (TiVCrNbMo) 5 C 4 T xAerogel; This method increases the configurational entropy by adding element types, thereby reducing the Gibbs free energy and stabilizing the crystal structure. This makes the high-entropy MXene have a longer cycle life and can work in a wider voltage range without polarization; at the same time, the Ti, V, Cr, Nb, Mo, Al, and C elements in the high-entropy MXene material prepared by this method are evenly distributed in the layered high-entropy MAX powder, and the content of Ti, V, Cr, Nb and Mo is close to 20at%, within the range of 5-35%, and the distribution of the five metal elements is very uniform, without obvious aggregation effect; and the high-entropy MXene (TiVCrNbMo) 5 C 4 T x The high-entropy MXene electrode material prepared by aerogel has excellent capacitance and outstanding cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below.

[0027] Figure 1 XRD diagram of high entropy MXene of Example 1 of the present invention

[0028] Figure 2 The morphology photographs of Example 1 of the present invention; wherein: (a) high entropy MAX, (b) multilayer high entropy MXene, (c, d) high entropy MXene aerogel, (e) scanning electron microscope images of high entropy MXene film; the inset in (e) shows a photograph of the high entropy MXene film obtained by vacuum filtration; (f) transmission electron microscope image of high entropy MXene; the inset shows 10nm -1 SAED pattern; (g) HAADF-STEM image of high entropy MAX and the corresponding element distribution map.

[0029] Figure 3 It is a morphological photograph of Example 1 of the present invention; wherein: (a) and (b) are the top view and side view of the aberration-corrected STEM image of the high-entropy MXene, respectively; (c) the atomic resolution HAADF and corresponding Super-EDS image of the high-entropy MXene.

[0030] Figure 4 The morphology photos of Example 2, Example 3 and Example 4 of the present invention are shown as follows: (a) Ti 3 AlC 2 , (b) Nb 2 AlC, (c)V 2 AlC, (d)Ti 3 C 2 Tx , (e)Nb 2 CT x and (f)V 2 CT x Scanning electron microscope image of .

[0031] Figure 5 The performance diagrams of supercapacitors of the embodiments and control examples of the present invention are shown in Figure 1. (a) High entropy MXene (referred to as HE-MXene in the figure) has a high entropy capacity of 100 mV / s at different scan rates (2-100 mV s -1 ) at different current densities (1-10A). -1 ) under constant current charge and discharge curves; (c) high entropy MXene and Ti 3 C 2 T x , Nb 2 CT x and V 2 CT x Comparison of CV curves of single transition metal MXenes; (d) High entropy MXene and Ti 3 C 2 T x , Nb 2 CT x and V 2 CT x Mass capacitance of single transition metal MXenes at different current densities; (e) High entropy MXene and Ti 3 C 2 T x , Nb 2 CT x and V 2 CT x Impedance diagram of single transition metal Mxenes; (f) Comparison of the performance of HE-MXene with other types of electrodes. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples. The following examples are only descriptive and not restrictive, and the scope of protection of the present invention cannot be limited by them. Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed in the present invention are not limited to any implementation method. In addition, some aspects disclosed in the present invention can be used alone or in any appropriate combination with other aspects disclosed in the present invention.

[0033] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0034] Embodiment 1:

[0035] 1. Preparation of five-metal transition high entropy MXene materials

[0036] A method for preparing a five-transition metal high entropy MXene material comprises the following steps:

[0037] 1) High entropy MAX material (TiVCrNbMo) 5 AlC 4 Powder synthesis

[0038] Ti, V, Cr, Nb, Mo, Al and graphite powders were uniformly mixed in a molar ratio of 1:1:1:1:1:1.3:3.5; the uniformly mixed powders were spread in an alumina crucible, and then transferred to a tube furnace and sintered at 1500°C. A constant argon flow rate should be maintained throughout the sintering process to prevent the sample from being oxidized; after cooling, the surface of the sintered blank was polished with sandpaper and ground to obtain a high entropy MAX material (TiVCrNbMo) 5 AlC 4 powder;

[0039] 2) High entropy MXene (TiVCrNbMo) 5 C 4 T x Synthesis

[0040] MAX material (TiVCrNbMo) 5 AlC 4 The powder was slowly added to a polytetrafluoroethylene reactor containing 45% hydrofluoric acid. The whole process lasted for 60 seconds. High entropy MAX material (TiVCrNbMo) 5 AlC 4 The ratio of powder to hydrofluoric acid solution was 1:15 g / mL; the reaction was carried out in a 45°C water bath and stirred continuously for 70 hours; the suspension after the reaction was centrifuged, dispersed and decanted multiple times until the pH of the supernatant was >6, and the MXenes were collected on cellulose filter paper by vacuum filtration and dried at 60°C in vacuum for 24 hours to obtain high entropy MXene (TiVCrNbMo) 5 C 4 T x

[0041] 3) High entropy MXene (TiVCrNbMo) 5 C 4 T xSynthesis of aerogel

[0042] Take the high entropy MXene (TiVCrNbMo) obtained in step 2) 5 C 4 T x , added to the intercalant, the mass concentration of the intercalant is 10wt%, high entropy MXene (TiVCrNbMo) 5 C 4 T x The ratio of the intercalation agent to the mixture is 1:30 g / mL, stirred to obtain a mixture; the mixture is centrifuged for the first time to obtain a precipitate, and the pH value of the supernatant is measured; the precipitate is dispersed with deionized water, centrifuged for the second time, the precipitate is obtained again, and the pH value of the supernatant is measured again; repeated several times, when the pH value of the supernatant is 7.0, the precipitate is dispersed again with deionized water, ultrasonically treated for 1.5 hours under the action of inert gas bubbling, and centrifuged for the third time to obtain a supernatant, i.e., a few-layer MXene solution; the few-layer MXene solution is freeze-dried for 50 hours to obtain a high entropy MXene (TiVCrNbMo) 5 C 4 T x Aerogel is a five-transition metal high-entropy MXene material.

[0043] In step 1), during sintering, a programmed temperature rise method is used, and the heating rate from room temperature to 1200°C is 10°C / min, and the heating rate from 1200°C to the sintering temperature is 2°C / min. The prepared high entropy MAX material (TiVCrNbMo) 5 AlC 4 The particle size of the powder is 50-100 μm.

[0044] In step 2), the stirring speed is 450 r / min, the centrifugal speed is 3500 r / min, and the centrifugal time is 5 min. In step 3), the first centrifugal speed and the second centrifugal speed are both 5000 r / min, and the centrifugal time is 5 min; the third centrifugal speed is 3500 r / min, and the centrifugal time is 60 min. The intercalating agent used in this embodiment is tetrabutylammonium hydroxide.

[0045] 2. Performance test of five transition metal high entropy MXene materials:

[0046] The present application performs a performance test on the substance obtained by the preparation method provided in Example 1; specifically:

[0047] 1) Material identification

[0048] The present application is to prepare the high entropy MXene (TiVCrNbMo) obtained in Example 1 5 C 4 Tx Aerogel material was subjected to XRD test, and the results were as follows Figure 1 As shown, from Figure 1 It can be seen that there is an obvious (002) peak at 5°, indicating that the high entropy MXene (TiVCrNbMo) prepared by the present invention 5 C 4 T x The aerogel material is of extremely high purity, and a new type of five-transition metal high-entropy MXene was successfully synthesized.

[0049] 2) Material morphology determination

[0050] The present application used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study the morphology and microstructure of the product prepared in steps 1)-3) of Example 1. The results are as follows: Figure 2 As shown, Figure 2 a is the high entropy MAX material (TiVCrNbMo) in Example 1 5 AlC 4 The SEM image shows a typical dense layered structure. After the aluminum atomic layer in the high entropy MAX is selectively etched by hydrofluoric acid, the original dense layered structure is opened. After washing and vacuum drying, a multilayer high entropy MXene powder can be obtained, which shows a typical accordion-like microstructure ( Figure 2 b); after layering the multi-layer high entropy MXene powder, a few-layer or single-layer high entropy MXene solution is obtained, which is freeze-dried to obtain a high entropy MXene aerogel, such as Figure 2 As shown in Figures 2c and 2d, from the side view, the high entropy MXene aerogel has an irregular three-dimensional macroporous structure with thin pore walls. From the top view, the high entropy MXene aerogel is composed of a few or a single layer of MXene sheets stacked together. These three-dimensional holes and thin pore wall structures can greatly shorten the diffusion distance of electrolyte ions and increase the contact area with the electrolyte, which is beneficial to improving the electrochemical performance.

[0051] 3) Thin film structure of the material

[0052] In this application, a few-layer or single-layer high entropy MXene solution is prepared into a HE-MXene film by vacuum filtration ( Figure 2 e); the thickness of the obtained high-entropy MXene film is about 20μm. After the two-dimensional material is filtered, the nanosheets on the cross section show a typical layered and tightly packed morphology. This is because under the action of gravity, the two-dimensional nanosheets in the high-entropy MXene wet film are often assembled layer by layer; high-resolution TEM and the corresponding selected area electron diffraction pattern (SAED) clearly show the lattice and hexagonal structure of the prepared multilayer high-entropy MXene, indicating that after a long-term hydrofluoric acid reaction, the good crystallinity can be well maintained ( Figure 2 f). Figure 2 g shows the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of high-entropy MAX and its corresponding element distribution; it can be clearly seen that the Ti, V, Cr, Nb, Mo, Al, and C elements are evenly distributed in the stacked layers of high-entropy MAX powder.

[0053] 4) Element ratio of high entropy materials

[0054] This application uses SEM-EDS to analyze the element ratio of high entropy MAX and high entropy MXene. The EDS point scanning results are shown in Table 1:

[0055] Table 1 EDS point scanning results

[0056]

[0057] As can be seen from Table 1, after HF etching, multilayer HE-MXene still maintains a transition metal chemical ratio close to that of its MAX precursor, with the ratio of Ti, V, Cr, Nb, and Mo being approximately 1:1:1:1:1. Since the Cr-C bond in multilayer high-entropy MXene is weaker than other MC bonds, the proportion of Cr in multilayer HE-MXene is slightly lower than that in the precursor, and MXene containing Cr is more reactive during selective etching. In addition, we used ICP-OES to analyze the element ratio of the single-layer MXene, as shown in Table 2:

[0058] Table 2: Element ratios of MXene

[0059]

[0060] As can be seen from Table 2, the contents of Ti, V, Cr, Nb and Mo are close to 20 at.%, and are in the range of 5-35 at.%.

[0061] 5) Atomic arrangement of high entropy materials

[0062] This application further studies the atomic arrangement of high entropy MXenes using atomic resolution aberration-corrected electron microscopy. The results are as follows Figure 3 Shown: Among them Figure 3 a directly shows some regular arrangements of atoms with different brightness intensities. As we all know, the brightness of an atom is proportional to the square of its atomic number. Following this principle, Figure 3 In the enlarged image of a, the brightest atom is the Mo atom, and the darkest atom is the Ti atom. The uneven distribution of brightness indicates that the m-site element atoms in the high-entropy MXene are arranged in a solid solution manner. Figure 3 As shown in b, there are obvious dark areas between adjacent layers, which are caused by the reaction of Al atoms with hydrofluoric acid, indicating that high-entropy MAX is successfully converted into high-entropy MXene. Importantly, the super-EDS results ( Figure 3 c) shows that the distribution of the five elements is very uniform even in the nanometer range, with no obvious aggregation effect.

[0063] Example 2: Preparation of supercapacitor electrode materials

[0064] A method for preparing a five-metal transition high entropy MXene supercapacitor electrode material comprises the following steps:

[0065] The high entropy MXene (TiVCrNbMo) prepared in Implementation 1 5 C 4 T x The aerogel is mixed with polytetrafluoroethylene (PTFE) adhesive and acetylene black, which is added between MXene sheets to form a conductive network, with a mass ratio of 80:10:10 and dispersed in 0.5-2mL n-methyl-2-pyrrolidone (NMP) solvent; the resulting mixture is homogenized with ultrasound, coated on a conductive carbon cloth substrate, and then dried in a vacuum freeze drying oven for 20-30h to obtain a five-metal transition high entropy MXene supercapacitor electrode material.

[0066] Performance Testing:

[0067] 1) Electrochemical test

[0068] The present application conducts electrochemical tests on the five-metal transition high entropy MXene supercapacitor electrode material (hereinafter referred to as high entropy MXene electrode) in 1M KOH electrolyte using cyclic voltammetry (CV), constant current charge and discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results are as follows: Figure 5 Specifically, the present application selected a range of -1.0 to -0.3 V (vs. Hg / HgO) to test the cyclic voltammetry curve of the high entropy MXene electrode, with a scan rate of 2 to 100 mV s -1 .like Figure 5 As shown in a, in the range of 2 to 100 mV s -1 At a scan rate of , the CV curve of the high entropy MXene electrode is approximately a symmetrical regular rectangle, and no obvious redox peaks and polarization phenomena are observed (i.e., there is no upturn at both ends of the CV curve); with the increase of the scan rate, the CV curve is not obviously bent, showing good reversibility; the GCD test can record the voltage curve that changes with time, which can reflect the charge and discharge performance of the electrode like the CV curve; Figure 5As shown in Figure b, as the current density decreases, the charge and discharge time of the electrode increases. This is because at a lower current density, the ions in the electrolyte can be more fully inserted between the MXene layers. At the same time, it can be observed that there is an insignificant voltage drop process at the top of the charge and discharge curve. This small voltage drop can reflect the size of the electrode internal resistance. However, the voltage drop in this application is not very obvious, so it can be considered that the electrode internal resistance is low. When the current density is 1Ag -1 The mass capacitance of the high entropy MXene electrode is 284.6 F g -1 .

[0069] 2) Capacitor performance test

[0070] This application tests the capacitance performance of five-metal transition high entropy MXene supercapacitor electrode materials and introduces single transition metal MXenes, Nb 2 CT x ,V 2 CT x and Ti 3 C 2 T x As a comparative example, a supercapacitor electrode material was prepared by the same preparation method as that of Example 2; wherein Nb 2 CT x ,V 2 CT x and Ti 3 C 2 T x The preparation method of Nb is prior art and will not be described in detail here; 2 CT x ,V 2 CT x and Ti 3 C 2 T x The material can also be purchased from commercial sources; its Nb 2 CT x ,V 2 CT x and Ti 3 C 2 T x The morphology of the material is shown in Figure 4 As shown; where (a) Ti 3 AlC 2 , (b) Nb 2 AlC, (c)V 2 AlC, (d)Ti 3 C 2 T x , (e)Nb 2 CT x and (f)V2 CT x SEM images of Figure 5 c is in 1 M KOH electrolyte, with a scan rate of 100 mV s -1 The CV curves of different suitable voltage windows of high entropy MXene electrode and single transition metal MXene electrode materials in the three-electrode system. It can be seen that the high entropy MXene electrode has a higher voltage window than the single transition metal Nb 2 CT x ,V 2 CT x and Ti 3 C 2 T x The electrode has a wider operating voltage window. In the same electrolyte, V 2 CT x The electrode material begins to show slight polarization at -0.5V (i.e., the two ends of the curve show obvious upward curvature), which is more obvious at low scan rates. The high entropy MXene electrode has an operating voltage window of 0.7V and does not polarize at low and high scan rates. Figure 5 a, 5c can be seen, and Nb 2 CT x ,V 2 CT x and Ti 3 C 2 T x Compared with the MXene electrode, the integrated area of ​​the cyclic voltammetry curve of the high entropy MXene electrode is the largest at both low and high scan rates, which means that the crystal stability improved by the increase in the number of transition metal species in MXene can significantly optimize its working state in the electrolyte, that is, improve its electrochemical performance and working voltage window. By comparing the GCD curve, we can also see that the high entropy MXene electrode always has a longer discharge time than the single transition metal MXenes at low and high current densities; the weight capacitance of different MXenes at different current densities is as follows: Figure 5 As shown in Figure d, when the current density increases 10 times, the gravimetric capacitance of the high-entropy MXene electrode is still 170 Fg -1 , showing excellent rate performance.

[0071] Figure 5 e shows the Nyquist plots of different MXenes, with the inset being a magnified view of the high-frequency region. The Nyquist plot consists of a semicircle in the high-frequency region and a straight line in the low-frequency region. In the high-frequency region, the intersection of the semicircle and the real axis is the internal resistance (R s The internal resistance of the material is composed of the active material, the internal resistance of the collector, and the contact resistance between the electrode and the electrolyte. The radius of the semicircle is the charge transfer resistance (R ct), the smaller the radius, the smaller the charge transfer resistance of the electrode; the straight line part in the low-frequency region is related to the diffusion of ions in the electrolyte. It can be seen that the intercept value and radius of the high-entropy MXene electrode in the high-frequency region are both small, indicating that its R s and R ct are lower than those of single transition metal MXene electrodes. This indicates that high entropy MXene has better conductivity. This also reveals the reason why high entropy MXene electrodes have superior capacitance performance. In addition, the nearly vertical lines in the low-frequency region show the capacitance characteristics of the electrode, indicating that the electrode exhibits fast diffusion kinetics. By comparing our work with other works ( Figure 5 f), it can be found that (TiVCrNbMo) prepared by the preparation method of the present application 5 C 4 T x The high-entropy MXene electrodes prepared from aerogels have good capacitance. These excellent preliminary results indicate that (TiVCrNbMo) 5 C 4 T x Aerogels are promising candidate electrode materials for energy storage applications that may exceed the charge storage performance of conventional MXenes. Furthermore, the tunability of the M sites in MAX materials provides unlimited opportunities to tune the composition of the resulting MXenes, which are ideal for energy storage and catalysis applications.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a five-metal transition high entropy MXene material, characterized in that: The steps include: 1) Synthesis of high entropy MAX material (TiVCrNbMo) 5AlC4 powder Ti, V, Cr, Nb, Mo, Al and graphite powders are uniformly mixed in a molar ratio of 1:1:1:1:1:1.3:3.5; the uniformly mixed powders are spread in an alumina crucible, and then transferred to a tube furnace and sintered at 1400-1600° C. A constant argon flow rate should be ensured throughout the sintering process to prevent the sample from being oxidized; after cooling, the surface of the sintered blank is polished with sandpaper and ground to obtain a high entropy MAX material (TiVCrNbMo)5AlC4 powder; In step 1), during sintering, a programmed temperature increase method is adopted, and the heating rate from room temperature to 1200° C. is 10° C. / min, and the heating rate from 1200° C. to the sintering temperature is 2° C. / min; 2) High entropy MXene (TiVCrNbMo)5C4T x Synthesis The MAX material (TiVCrNbMo) 5AlC4 powder was slowly added to a polytetrafluoroethylene reactor containing 40-50% hydrofluoric acid by mass concentration. The whole process lasted for 60 seconds. The ratio of high entropy MAX material (TiVCrNbMo) 5AlC4 powder to hydrofluoric acid solution was 1:10-20 g / mL. The reaction was carried out in a 45-50°C water bath and stirred continuously for 60-80 hours. The suspension after the reaction was centrifuged, dispersed and decanted for multiple times until the pH of the supernatant was >6. The MXenes were vacuum filtered and collected on cellulose filter paper and vacuum dried at 60°C for 24 hours to obtain high entropy MXene (TiVCrNbMo) 5C4T x ; 3) High entropy MXene (TiVCrNbMo)5C4T x Synthesis of aerogel Take the high entropy MXene (TiVCrNbMo) 5C4T obtained in step 2) x , added to the intercalant, the mass concentration of the intercalant is 10-15wt%, high entropy MXene (TiVCrNbMo) 5C4T x The ratio of the intercalating agent to the intercalating agent is 1:10-40 g / mL, and the mixture is stirred to obtain a mixture; the mixture is centrifuged for the first time to obtain a precipitate, and the pH value of the supernatant is measured; the precipitate is dispersed with deionized water, centrifuged for the second time, the precipitate is obtained again, and the pH value of the supernatant is measured again; repeat several times, when the pH value of the supernatant is 6.0-8.0, the precipitate is dispersed again with deionized water, ultrasonically treated for 1-2 hours under the action of inert gas bubbling, and centrifuged for the third time to obtain a supernatant, i.e., a few-layer MXene solution; the few-layer MXene solution is freeze-dried for 40-60 hours to obtain a high entropy MXene (TiVCrNbMo)5C4T x Aerogel is a five-metal transition high entropy MXene material; The high entropy MXene (TiVCrNbMo) 5C4T obtained in step 2) x It presents a multilayer accordion-like structure, which is composed of five transition metal layers and four carbon layers alternating at the atomic scale; the high entropy MXene (TiVCrNbMo) 5C4T obtained in step 3) x The aerogel is composed of a few layers and / or a single layer of MXene flakes stacked together, presenting an irregularly shaped three-dimensional macroporous structure with an average pore wall thickness of 20 μm.

2. The method for preparing the five-metal transition high entropy MXene material according to claim 1, characterized in that: In step 1), the particle size of the high entropy MAX material (TiVCrNbMo)5AlC4 powder is 50-100 μm.

3. The method for preparing the five-metal transition high entropy MXene material according to claim 1, characterized in that: In step 2), the stirring speed is 300-500 r / min, the centrifugal speed is 3000-4000 r / min, and the centrifugal time is 3-8 min.

4. The method for preparing the five-metal transition high entropy MXene material according to claim 1, characterized in that: In step 3), the speed of the first centrifugation and the second centrifugation are both 4000-6000 r / min, and the centrifugation time is 4-6 min; the speed of the third centrifugation is 3000-4000 r / min, and the centrifugation time is 50-70 min.

5. The method for preparing the five-metal transition high entropy MXene material according to claim 1, characterized in that: In step 3), the intercalation agent is any one or more of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and dimethyl sulfoxide.

6. A five-metal transition high entropy MXene material prepared according to any one of claims 1 to 5, characterized in that: The molecular formula of the five-metal transition high entropy MXene material is M5X4T x , wherein M is Ti, V, Cr, Nb and Mo; X represents at least one of carbon, nitrogen or boron; Tx represents a surface functional group, and Tx includes one or more of O, F, Cl, Br, I or OH.

7. The five-metal transition high entropy MXene material according to claim 6, characterized in that The mass percentage of Ti, V, Cr, Nb and Mo elements in the five-metal transition high entropy MXene material is 5%-30%.

8. A method for preparing a five-transition metal high entropy MXene supercapacitor electrode material, characterized in that: The following steps are involved: The five-metal transition high entropy MXene material according to claim 6 or 7 is a high entropy MXene (TiVCrNbMo) 5C4T x The aerogel is mixed with polytetrafluoroethylene (PTFE) adhesive and acetylene black, which is added between MXene sheets to form a conductive network, with a mass ratio of 80:10:10 and dispersed in 0.5-2mL n-methyl-2-pyrrolidone (NMP) solvent; the resulting mixture is homogenized with ultrasound, coated on a conductive carbon cloth substrate, and then dried in a vacuum freeze drying oven for 20-30h to obtain a five-transition metal high-entropy MXene supercapacitor electrode material.

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