A layered V2C MXene energy storage catalytic material and its preparation method, storage method and application

Abstract

The present invention provides a layered V2C MXene energy storage catalytic material and its preparation, storage, and application, comprising the following steps: Step 1: Adding V2AlC powder to an HF solution to obtain a mixed system; Step 2: Stirring and etching the mixed system under heated and sealed conditions to obtain a reaction solution; Step 3: Washing the reaction solution until the pH of the resulting supernatant is 6-7 to obtain layered V2C MXene powder; Step 4: Adding the layered V2C MXene powder to a mixed solution of sodium borohydride and sodium hydroxide, stirring and etching to obtain a mixed reaction solution; Step 5: Washing, separating, and drying the mixed reaction solution to obtain the layered V2C MXene energy storage catalytic material. The resulting V2C MXene has a low content of surface end groups, maintains chemical stability for more than 30 days, and exhibits broad-spectrum catalytic degradation of organic compounds such as antibiotics under dark light and across the entire spectrum.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor MXene-based catalytic functional materials and relates to a layered V2C MXene energy storage catalytic material and a preparation method, storage method and application thereof. Background Art

[0002] In recent years, the great potential of new two-dimensional materials (MXene) in the field of catalysis has attracted widespread attention. The molecular formula of MXene can be expressed as M n+1 X n T x (n=1 to 4), wherein M represents a transition metal (such as Ti, V, Zr, Nb, etc.), X represents C or N, T represents a surface end group (such as -F, -O or -OH), M n+1 X n T x Can also be abbreviated as M n+1 X n MXene materials have an adjustable band gap (0.92-1.75 eV), excellent high conductivity and hydrophilicity, and are therefore widely used in energy storage and catalysis.

[0003] However, MXene is usually obtained by HF wet etching, and a large number of -F end groups are introduced during the HF etching process. On the one hand, the end groups can improve the properties of MXene itself, affect the work function of the MXene material itself, and affect the migration and charge storage capabilities of metal ions. On the other hand, due to the strong electronegativity of F, the surface -F can easily detach from the MXene surface, leaving defects on the MXene surface, making it easy for free water and active oxygen in the environment to attack the surface defects of MXene, thereby destroying the MXene structure and affecting the catalytic stability of MXene. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a layered V2C MXene energy storage catalytic material and its preparation method, storage method and application. The obtained V2C MXene has a low content of surface end groups, can maintain chemical stability for more than 30 days, and has a broad-spectrum catalytic degradation effect on organic matter such as antibiotics under dark light and within the full spectrum range.

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

[0006] A method for preparing a layered V2C MXene energy storage catalytic material comprises the following steps:

[0007] Step 1, adding V2AlC powder to HF solution to obtain a mixed system;

[0008] Step 2, stirring and etching the mixed system under heating and sealing conditions to obtain a reaction solution;

[0009] Step 3, washing the reaction solution until the pH of the obtained supernatant is 6-7 to obtain layered V2C MXene powder;

[0010] Step 4: Add the layered V2C MXene powder to a mixed solution of sodium borohydride and sodium hydroxide, stir and etch to obtain a mixed reaction solution;

[0011] In step 5, the mixed reaction liquid is washed, separated, and dried to obtain a layered V2C MXene energy storage catalytic material.

[0012] Preferably, in step 1, the mass fraction of the HF solution is 40%-49%.

[0013] Preferably, in step 2, the etching time is 48 to 72 hours.

[0014] Preferably, in step 4, the etching time is 20 to 24 hours.

[0015] Preferably, in step 4, in the mixed solution of sodium borohydride and sodium hydroxide, the molar ratio of sodium borohydride to sodium hydroxide is (0.05-0.9):0.5.

[0016] Preferably, in step 5, the drying is performed at 60-75° C. under vacuum for 10-14 hours.

[0017] The layered V2C MXene energy storage catalytic material is obtained by the preparation method.

[0018] The application of the layered V2C MXene energy storage catalytic material in the degradation of organic pollutants.

[0019] The storage method of the layered V2C MXene energy storage catalytic material is as follows: the layered V2C MXene energy storage catalytic material is dispersed in a supersaturated sodium chloride aqueous solution and stored in a light-proof environment at room temperature.

[0020] Preferably, the concentration of sodium chloride in the supersaturated sodium chloride aqueous solution is 0.5M to 5.5M.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The present invention discloses a method for preparing a layered V2C MXene energy storage catalytic material. V2C MXene is prepared through a two-step etching process. First, HF-etched vanadium carbide powder is treated with a mixed solution of sodium borohydride and sodium hydroxide. Under alkaline conditions, a large number of -OH groups are introduced to replace the -F groups on the MXene surface, replacing the -F end groups on the V2C MXene surface. This reduces the structural damage caused by the desorption of the surface -F groups, thereby obtaining a layered V2C MXene with excellent structural integrity. This method has a positive effect on the structural integrity and performance stability of the V2C MXene. The addition of the reducing agent NaBH4 inhibits local oxidation of the V2C MXene, exposing a large number of active sites. This results in the generation of holes and electrons on the surface and between the layers of the V2C MXene. The interlayer vacancies form positive potential centers, attracting and binding free electrons between the layers, resulting in the storage of a certain amount of holes on the V2C MXene surface. The localized holes between the layers can also store a certain amount of electrons. This method maintains the chemical stability of the V2C MXene while enhancing its redox capacity. Particularly in the dark, surface holes release before interlayer electrons, directly participating in the degradation of organic matter. Localized interlayer holes disappear as the holes are consumed, and electrons are released with a delay, gradually generating OH radicals that further contribute to the degradation of organic matter. This enables the V2C MXene of the present invention to directly mineralize macromolecular organic matter in the dark without external excitation. Furthermore, under illumination, holes and electrons can be continuously excited, and the surface plasmon effect enhances light absorption in the near-infrared range, further enhancing degradation performance under near-infrared light, thereby achieving all-weather energy storage catalysis in the dark and full-spectrum range. The vanadium carbide precursor is then secondary etched with a mixed solution of sodium borohydride and sodium hydroxide to reduce the surface end group content of the V2C MXene, resulting in a structurally complete layered V2C MXene capable of storing electrons and holes.

[0023] The layered V2C MXene of the present invention stores holes and electrons on its surface and between layers, which can directly produce a good mineralization effect on organic matter in the dark and effectively degrade antibiotic pollutants in the dark and full spectrum range.

[0024] The present invention's layered V2C MXene storage method involves dispersing V2C MXene powder in a supersaturated sodium chloride aqueous solution for storage. Small-radius anions in the inorganic salt inhibit the generation of free water and reactive oxygen species in the storage environment, protecting defect sites caused by -F desorption from attack by free water or reactive oxygen species. This maintains the structural stability and chemical stability of the layered V2C MXene. Upon use, the vanadium carbide MXene is separated and dried from the supersaturated sodium chloride solution to obtain a layered vanadium carbide MXene with a stable structure. This method can maintain the chemical stability of the V2C MXene for over 30 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD patterns of V2C-HF prepared in Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention are shown.

[0026] Figure 2 This is the XRD pattern of the layered V2C MXene prepared in Example 1 of the preparation part of the present invention.

[0027] Figure 3 This is the SEM spectrum of the hexagonal phase V2AlC in the present invention.

[0028] Figure 4 This is the SEM spectrum of the V2C MXene prepared in Comparative Example 1 of the present invention.

[0029] Figure 5 This is the SEM image of the V2C MXene prepared in Example 1 of the preparation part of the present invention.

[0030] Figure 6 Raman spectra of V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention.

[0031] Figure 7 This is the XPS total spectrum of the V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention.

[0032] Figure 8 V 2p XPS spectra of the V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention.

[0033] Figure 9 C1s XPS spectra of the V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention.

[0034] Figure 10 The degradation TC curves of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention in the dark are shown.

[0035] Figure 11 The degradation TC rate curves of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention in the dark are shown.

[0036] Figure 12 This is the TC organic carbon removal rate of the layered V2C MXene prepared in Example 1, Comparative Example 1 and Comparative Example 4 of the present invention during degradation in the dark.

[0037] Figure 13The degradation TC curves of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention under simulated sunlight are shown.

[0038] Figure 14 The degradation TC rate curves of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention under simulated sunlight are shown.

[0039] Figure 15 This is the TC organic carbon removal rate of the layered V2C MXene prepared in Example 1, Comparative Example 1 and Comparative Example 4 of the present invention under simulated sunlight.

[0040] Figure 16 Degradation TC curves of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention under near-infrared light.

[0041] Figure 17 The degradation TC rate curves of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention under near-infrared light are shown.

[0042] Figure 18 This is the TC organic carbon removal rate of the layered V2C MXene prepared in Example 1, Comparative Example 1 and Comparative Example 4 of the present invention under near-infrared light degradation.

[0043] Figure 19 EPR spectra of the layered V2C MXene prepared in Example 1 and Comparative Example 1 of the present invention.

[0044] Figure 20 The layered V2C MXene prepared in Example 1 of the present invention was prepared under dark light for h + EPR spectrum of .

[0045] Figure 21 This is a graph showing the absorbance change of the methylene blue decolorization experiment under dark light for the layered V2C MXene prepared in Example 1 of the preparation part of the present invention.

[0046] Figure 22 This is a diagram showing the capture of TC active species by the layered V2C MXene prepared in Example 1 of the preparation part of the present invention under dark light.

[0047] Figure 23 This is a graph showing the degradation of other pollutants by the layered V2C MXene prepared in Example 1 of the present invention under dark light.

[0048] Figure 24This is a graph showing the degradation of other pollutants by the layered V2C MXene prepared in Example 1 of the present invention under simulated visible light.

[0049] Figure 25 UV-visible diffuse reflectance spectra of the layered V2C MXene prepared in some Example 1, Comparative Example 1 and Comparative Example 4 of the present invention.

[0050] Figure 26 This is the EPR spectrum of DMPO-·OH of the layered V2C MXene prepared in Example 1 of the present invention under simulated sunlight conditions.

[0051] Figure 27 The layered V2C MXene prepared in Example 1 of the present invention was prepared under simulated sunlight conditions using DMPO-·O2 - EPR spectrum of .

[0052] Figure 28 The layered V2C MXene prepared in Example 1 of the present invention was prepared under simulated sunlight conditions. + EPR spectrum of .

[0053] Figure 29 Schematic diagram of the possible pathways and intermediate products of TC degradation by the layered V2C MXene prepared in Example 1 of the preparation part of the present invention under dim light.

[0054] Figure 30 Schematic diagram of the catalytic mechanism of the layered V2C MXene prepared in Example 1 of the preparation part of the present invention under dark light.

[0055] Figure 31 The XRD patterns of V2C MXene in storage part Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown.

[0056] Figure 32 This is the SEM image of the V2C MXene in Comparative Example 2 of the storage part of the present invention.

[0057] Figure 33 This is the SEM spectrum of the V2C MXene in Example 2 of the storage part of the present invention after storage for one month.

[0058] Figure 34 This is the SEM spectrum of the V2C MXene in Example 1 of the storage part of the present invention after storage for one month.

[0059] Figure 35 This is the degradation TC curve of V2CMXene stored in the dark for one month in Comparative Example 1, Comparative Example 2 and Examples 1 and 2 of the present invention.

[0060] Figure 36 This is the degradation TC curve of V2CMXene stored for one month under simulated sunlight in Comparative Example 1, Comparative Example 2 and Examples 1 and 2 of the present invention.

[0061] Figure 37 This is the degradation TC curve of V2CMXene stored for one month under near-infrared light in Comparative Example 1, Comparative Example 2 and Examples 1 and 2 of the present invention. DETAILED DESCRIPTION

[0062] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0063] The preparation method of the layered V2C MXene energy storage catalytic material of the present invention comprises the following steps:

[0064] Step 1: slowly adding V2AlC powder into HF solution with a mass fraction of 40%-49% to obtain a mixed system;

[0065] Step 2, stirring and etching the mixed system at 55° C. for 48 to 96 hours, and performing an etching reaction under a plastic wrap seal to obtain a reaction solution;

[0066] Step 3: The reaction solution is centrifuged and washed 6 to 9 times with deionized water and anhydrous ethanol respectively until the pH of the supernatant is 6 to 7 to obtain precipitated layered V2C MXene powder;

[0067] Step 4: Slowly add the layered V2C MXene powder to the prepared mixed solution of sodium borohydride and sodium hydroxide, seal with plastic wrap, etch and stir for 20 to 24 hours to obtain a mixed reaction solution; in the mixed solution of sodium borohydride and sodium hydroxide, the molar ratio of sodium borohydride to sodium hydroxide is (0.025-0.65):0.5;

[0068] Step 5: The mixed reaction liquid is washed, separated, and vacuum-dried at 60-75° C. for 10-14 hours to obtain a layered V2CMXene energy storage catalytic material.

[0069] The prepared layered V2C MXene energy storage catalytic material can be used to degrade antibiotic organic pollutants.

[0070] The storage method of the obtained layered V2C MXene energy storage catalytic material comprises the following steps:

[0071] The obtained structurally stable layered V2C MXene energy storage catalytic material is dispersed in a supersaturated sodium chloride aqueous solution and stored in a light-proof environment at room temperature. The concentration of sodium chloride in the prepared supersaturated sodium chloride aqueous solution is 0.5M to 5.5M. When used, the V2C MXene is washed and separated from the supersaturated sodium chloride aqueous solution to a pH of 6 to 7, and then vacuum-dried at 65 to 75°C for 12 to 14 hours to obtain the layered V2C MXene.

[0072] 1. Preparation of layered V2C MXene energy storage catalytic materials

[0073] Comparative Example 1:

[0074] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0075] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0076] Step 2: The obtained precipitated V2C MXene powder reaction solution was washed and separated, and vacuum dried at 65 °C for 12 h to obtain layered vanadium carbide powder, named V2C-HF (72).

[0077] Comparative Example 2:

[0078] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0079] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 48h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0080] Step 2: The precipitated V2C MXene powder reaction solution was washed and separated, and then vacuum-dried at 65 °C for 12 h to obtain layered vanadium carbide powder, named V2C-HF (48).

[0081] Comparative Example 3:

[0082] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0083] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 96h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0084] Step 2: The precipitated V2C MXene powder reaction solution was washed and separated, and then vacuum-dried at 65 °C for 12 h to obtain layered vanadium carbide powder, named V2C-HF(96).

[0085] Comparative Example 4:

[0086] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0087] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0088] Step 2: The obtained V2C MXene powder was slowly added to 20 ml of 0.5 M sodium hydroxide solution prepared in advance, and the mixture was etched and stirred for 22 hours under plastic wrap. The reaction liquid was washed and separated, and vacuum dried at 65°C for 12 hours to obtain layered vanadium carbide powder, named V2C-OH.

[0089] Example 1:

[0090] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0091] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%. The concentration of V2AlC powder in the mixed system is 0.35mol / mL. Seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution. The reaction solution is centrifuged and washed with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2C MXene powder.

[0092] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 22 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 65°C for 12 hours to obtain a layered V2C MXene energy storage catalytic material, designated V2C-BH.

[0093] Example 2:

[0094] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0095] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 6 to obtain precipitated V2CMXene powder.

[0096] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 22 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 6. The supernatant is then vacuum-dried at 60°C for 12 hours to obtain a layered V2C MXene energy storage catalytic material.

[0097] Example 3:

[0098] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0099] Step 1: Add 3 g of V2AlC powder to 60 ml of HF solution with a concentration of 49%, stir at 55 ° C for 72 hours to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 6 to obtain precipitated V2C MXene powder.

[0100] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 22 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 6. The supernatant is then vacuum-dried at 70°C for 12 hours to obtain a layered V2C MXene energy storage catalytic material.

[0101] Example 4:

[0102] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0103] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0104] Step 2: Slowly add the resulting V2C MXene powder to a pre-prepared 20ml mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 22 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 75°C for 10 hours to obtain a layered V2C MXene energy storage catalytic material.

[0105] Example 5:

[0106] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0107] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 6 to obtain precipitated V2CMXene powder.

[0108] Step 2: Slowly add the resulting V2C MXene powder to a pre-prepared 20ml mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 24 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 60°C for 14 hours to obtain a layered V2C MXene energy storage catalytic material.

[0109] Example 6:

[0110] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0111] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0112] Step 2: Slowly add the resulting V2C MXene powder to a pre-prepared 20ml mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 23 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 70°C for 11 hours to obtain a layered V2C MXene energy storage catalytic material.

[0113] Example 7:

[0114] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0115] Step 1: Add 3 g of V2AlC powder to 60 ml of HF solution with a concentration of 49%, seal with plastic wrap, and stir at 55 ° C for 72 hours to obtain a reaction solution. The reaction solution is centrifuged and washed with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder;

[0116] Step 2: Slowly add the resulting V2C MXene powder to a pre-prepared 20ml mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 21 hours. The NaBH4:NaOH concentration ratio is 0.65mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 65°C for 13 hours to obtain a layered V2C MXene energy storage catalytic material.

[0117] Example 8:

[0118] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0119] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder.

[0120] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 20 hours. The NaBH4:NaOH concentration ratio is 0.05mmol / ml:1M. The reaction solution is washed and separated to a pH of 6. The supernatant is then vacuum-dried at 60°C for 13 hours to obtain a layered V2C MXene energy storage catalytic material.

[0121] Example 9:

[0122] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0123] Step 1: Add 3g of V2AlC powder to 60ml of HF solution with a concentration of 49%, seal with plastic wrap and stir at 55°C for 72h to obtain a reaction solution, and centrifuge and wash the reaction solution with deionized water and ethanol until the pH of the supernatant is 6 to obtain precipitated V2CMXene powder.

[0124] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 22 hours. The NaBH4:NaOH concentration ratio is 0.05mmol / ml:1M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 65°C for 14 hours to obtain a layered V2C MXene energy storage catalytic material.

[0125] Example 10:

[0126] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0127] Step 1: Add 3 g of V2AlC powder to 60 ml of HF solution with a concentration of 49%, seal with plastic wrap, and stir at 55 ° C for 72 hours to obtain a reaction solution. The reaction solution is centrifuged and washed with deionized water and ethanol until the pH of the supernatant is 6 to obtain precipitated V2CMXene powder;

[0128] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 24 hours. The NaBH4:NaOH concentration ratio is 0.05mmol / ml:1M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 75°C for 11 hours to obtain a layered V2C MXene energy storage catalytic material.

[0129] Example 11:

[0130] The present invention provides a method for preparing a layered V2C MXene energy storage catalytic material, comprising the following steps:

[0131] Step 1: Add 3 g of V2AlC powder to 60 ml of HF solution with a concentration of 49%, seal with plastic wrap, and stir at 55 ° C for 72 hours to obtain a reaction solution. The reaction solution is centrifuged and washed with deionized water and ethanol until the pH of the supernatant is 7 to obtain precipitated V2CMXene powder;

[0132] Step 2: Slowly add the resulting V2C MXene powder to a 20ml pre-prepared mixed solution of sodium borohydride and sodium hydroxide. Seal the mixture with plastic wrap and stir for 22 hours. The NaBH4:NaOH concentration ratio is 0.44mmol / ml:0.5M. The reaction solution is washed and separated to a pH of 7. The supernatant is then vacuum-dried at 65°C for 12 hours to obtain a layered V2C MXene energy storage catalytic material.

[0133] Weigh 50 mg of the product prepared in step 2 of each comparative example and embodiment above and disperse it in 50 mL of TC solution. Place it in an XPA-7 photochemical reactor in a 50 mL quartz test tube as a container and place it in the dark, simulated sunlight (500 W xenon lamp), and near-infrared light (500 W xenon lamp + 780 nm filter) under magnetic stirring (1100 r min -1 ). Then, the photocatalytic reaction was started directly. During the reaction, 3 mL of the upper suspension of the test tube was taken every 20 min and centrifuged (4000 r·min -1 After removing the photocatalyst powder, the absorbance curve of the supernatant was measured using a UV-visible spectrophotometer, and the absorbance value at 358 nm reflected the concentration of TC in the supernatant.

[0134] Figure 1 The XRD patterns of V2C-HF prepared in the comparative examples of the present invention are shown in the figure from top to bottom, which are the XRD patterns of V2C-HF and V2AlC precursors prepared in Comparative Example 2 (V2C-48), Comparative Example 1 (V2C-72), and Comparative Example 3 (V2C-96). The figure shows that after V2AlC is etched with 49% HF at 55°C, the diffraction peaks of the prepared sample at diffraction angles 2θ = 13.4°, 35.5°, 41.2°, and 55.5° are consistent with the characteristic diffraction peaks of the hexagonal V2AlC precursor (JCPDS No. 29-0101), corresponding to the (002), (100), (103), and (106) crystal planes of the hexagonal V2AlC, respectively. The diffraction peak intensity decreases with increasing etching time. The sample etched for 72 hours showed a diffraction peak (V2C-72) corresponding to the V2C (002) crystal plane at 2θ = 6.2°, which corresponds to the characteristic peak of V2C few layers. This indicates that under this condition, the Al layer of the V2AlC precursor was etched and peeled off, and lamellar V2C Mxene was successfully prepared. In addition, after 48 hours of etching, a special diffraction peak (V2C-48) of the V2C (004) crystal plane appeared at 2θ = 9.1°, which corresponds to the multi-layer characteristic peak of V2C. However, the (002) characteristic peak was not obvious. After 96 hours of etching, no diffraction peaks of the (002) and (004) crystal planes of V2C appeared (V2C-96). This may be because the etching time is too long, and part of the layered V2C structure is destroyed and dissolved by HF. This shows that under the condition of 72 hours, the initial etching effect of Al in V2AlC is the best.

[0135] Figure 2Figure 1 shows the XRD patterns of the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention. From bottom to top, they are the XRD patterns of the V2AlC phase precursor, Comparative Example 1 (V2C-HF), Comparative Example 4 (V2C-OH), and V2C MXene of Example 1 (V2C-BH). The figure shows that after HF etching of V2AlC under heating conditions, the diffraction angles 2θ = 13.4° and 41.2° are consistent with the characteristic diffraction peaks of the hexagonal V2AlC precursor (JCPDS No. 29-0101), corresponding to the characteristic peaks of the (002) and (103) crystal planes of the hexagonal V2AlC, respectively. The figure shows that the peak intensity of the characteristic diffraction peak in the V2AlC phase precursor decreases after etching; the V2C MXene prepared by etching shows a diffraction peak corresponding to the V2C (002) crystal plane at 2θ = 6.2° (V2C-HF), indicating that the Al layer of the V2AlC precursor was stripped in HF, successfully preparing V2C MXene powder. After secondary etching with a mixture of NaBH4 and NaOH (V2C-BH), the diffraction peak intensity corresponding to the V2C (002) crystal plane increased at 2θ = 6.2°, and the characteristic peak of multilayer V2C (004) appeared at 2θ = 9.1°. The comparative sample (V2C-OH) after secondary NaOH etching showed slightly weaker V2C (002) and (004) characteristic peaks at 2θ = 6.2° and 9.1°. The figure shows that the (002) and (103) characteristic peaks of V2AlC decrease with V2C-HF, V2C-OH, and V2C-BH, indicating that the Al layer in the V2AlC phase is successfully stripped off and layered V2C MXene is successfully formed.

[0136] Figure 3 The SEM image of the hexagonal V2AlC precursor (200 mesh) used in the present invention shows that the V2AlC precursor has a typical ternary layered stacking structure of the MAX phase and a smooth surface.

[0137] Figure 4 This is a SEM image of the V2C MXene prepared in Comparative Example 1 of the present invention. After HF etching, the V2AlC formed an accordion-like structure with approximately 18 layers, 3.6 μm thick, and an interlayer spacing of approximately 80 to 400 nm. However, the edges of the structure appeared damaged, demonstrating that pure HF etching destroys the V2C edge structure, thereby reducing its structural stability.

[0138] Figure 5This is an SEM image of the V2C MXene prepared in Example 1 of the present invention. After secondary etching with a mixture of NaBH4 and NaOH, V2AlC formed an accordion-like structure with a thickness of approximately 19 layers and a thickness of 4.3 μm. The interlayer spacing was approximately 40 to 600 nm, and the edge structure had better integrity, verifying the successful preparation of V2C MXene. This is because the VC bonds of V2AlC are mainly ionic bonds and covalent bonds, which are relatively strong, while the V-Al and Al-Al bonds contain more metallic bonds and have relatively weak bonding forces. They are easily broken under the action of acids and bases, thereby peeling off the Al layer. There is a significant spacing between the layers, forming a two-dimensional layered structure similar to graphene. In addition, NaBH4 can better protect the structural stability of V2C.

[0139] Figure 6 The Raman spectra of V2C MXene prepared in Example 1, Comparative Example 1 and Comparative Example 4 of the present invention are shown in Figure 1. Raman spectrum analysis shows that the V2C MXene after etching is located at 280 cm-1 relative to the MAX phase V2AlC. -1 A new characteristic peak (E 1g ), while the V2AlC phase is at 256cm -1 The characteristic peak at 404 cm-1 disappears, which can be attributed to the enhanced interlayer interaction after the destruction of the Al layer. -1 , 520cm -1 and 690cm -1 The enhancement of the characteristic peak at is attributed to V2CT x E of V in MXene 1g and A 1g Active phonon vibration mode. 404cm -1 The peak at 520 cm is from V2C(OH)2 -1 and 690cm -1 The peaks at are from the A of V2CF2 and V2CO(OH) 1g Model. E 1g Model and A 1g The models are attributed to the in-plane vibration and out-of-plane vibration of V atoms respectively. 1g and A 1g The scattering peak intensity decreases with V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1), indicating that the total amount of V2C terminals is reduced, thereby exposing more defect sites. In particular, the peak value of V2CF2 in V2C-BH is the weakest, indicating that the content of -F end groups on the surface of V2C-HF is reduced after etching with NaBH4 alkaline solution, resulting in a weakening of the scattering peak intensity of V2CF2. This may be conducive to exposing defects in V2C, thereby storing more holes and electrons.

[0140] Figure 7 This is the XPS full spectrum of the V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention. The full spectrum clearly shows the presence of V, C, O, and F elements in V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1) compared to V2AlC, while the peak intensity of the Al element is reduced, thus verifying the successful exfoliation of the Al layer in XRD and SEM. The F element is attributed to the residual -F end groups on the surface and between the layers introduced during the HF etching process, and the peak gradually weakens with V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1), indicating a reduction in the total amount of -F end groups.

[0141] Figure 8 The V2p XPS spectra of the V2C MXene and V2AlC precursor prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention are shown. In the V 2p XPS spectra, the V 2p orbitals in V2AlC and V2C can be fitted into three groups of double peaks after deconvolution, corresponding to the V 2p 3 / 2 Peak and V 2p 1 / 2 Peak. The V of V2AlC was calculated by fitting. 2+ 、V 3+ and V 4+ The contents are 26.15%, 22.82%, and 51.02% respectively, while the V of V2C etched by HF is 2+ 、V 3+ and V 4+ The contents are 29.07%, 40.52%, and 30.41% respectively. The V atoms in V 4+ The content is reduced (Comparative Example 1), while V 2+ 、V 3+ The content increases because the Al layer is etched, the V-Al bond is destroyed, and vacancy defects are formed, thereby generating free state e in the positive potential center adsorption system. - , V 4+ Combined part e - Thus converted into low-valence state V 2+ and V 3+ . V of V2C etched by NaOH 2+ 、V 3+ and V 4+ The contents are 28.45%, 29.79%, and 41.76% (Comparative Example 4), respectively. 4+ The increase in content is related to the partial oxidation of transition metal V under alkaline conditions, which leads to the formation of low-valent V 2+ and V 3+ The content of V2C etched by NaBH4 alkaline solution is reduced. 2+ 、V3+ and V 4+ The contents are 26.41%, 46.64%, and 26.95% (Example 1), respectively. 3+ The content continues to increase, and the high-valence V 4+ The content is significantly reduced. Compared with V2AlC, V 2+ and V 3+ The content increased by 24.08%, which proved that the reducing NaBH4 can effectively weaken the oxidation phenomenon of V2CMxene in NaOH solution to enhance the structural stability of V2C Mxene.

[0142] Figure 9 The C1s XPS spectra of the V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention are shown. The C1s orbitals of V2AlC, V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1) can all be fitted into four peaks, of which the V2AlC peak at 284.84 eV corresponds to a C-C (graphitic carbon) bond, attributed to the introduction of graphitic carbon during the test. The binding energies at 282.53 eV, 286.29 eV, and 288.99 eV are attributed to VC, CO, and OC=O bonds, of which the VC bond is the main chemical bond in the structure, and the CO and OC=O bonds are attributed to the lattice oxygen and hydroxyl end groups in the bulk phase. The VC, CO, and OC=O bond contents of V2C etched with NaOH were 10.86%, 12.66%, and 14.71%, respectively. The VC content decreased by 3.6% compared to that of V2C etched with HF. This decrease is likely due to the introduction of a large amount of -OH under alkaline conditions, which increases the relative contents of CO and OC=O bonds. In contrast, the VC, CO, and OC=O bond contents of V2C etched with NaBH4 were 17.31%, 12.7%, and 8.32%, respectively. This suggests that the reducing properties of NaBH4 can slow the partial oxidation of V and expose more effective defect sites, potentially enhancing the oxidation of V2C-BH.

[0143] Figure 10 The following curves show the degradation of tetracycline hydrochloride (TC) in the dark by the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4. A mixed solution of TC and the photocatalyst V2C MXene was magnetically stirred in a photochemical reactor without illumination, and the TC concentration was measured at regular intervals. The figure clearly shows that the blank experiment without catalyst showed almost no degradation of TC after 140 minutes in the dark, while the V2C MXene prepared in Example 1 achieved the best degradation rate of 57.91% after 140 minutes in the dark.

[0144] Figure 11 The degradation rate curves of tetracycline hydrochloride (TC) in the dark by the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention are shown. The fitted mineralization rate of TC by the V2C MXene prepared in Example 1 in the dark is 0.01009 min -1 The blank experiment without adding catalyst had almost no mineralization rate for TC under dark light conditions.

[0145] Figure 12 Figure 3 shows the organic carbon removal rates of tetracycline hydrochloride (TC) in the dark using the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4. After 80 minutes in the dark, the organic carbon removal rates of 40 mg / L TC degradation products by V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1) were 5%, 13%, and 17%, respectively. This demonstrates the authenticity of V2C MXene's direct TC degradation in the dark, with the sample prepared in Example 1 achieving the best mineralization results.

[0146] Figure 13 The degradation curves of tetracycline hydrochloride (TC) under simulated sunlight for the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 are shown. Before exposure to sunlight, a mixed solution of TC and the photocatalyst V2C MXene was magnetically stirred in a photochemical reactor, and the TC concentration was measured at regular intervals. As can be seen from the figure, a blank experiment without the addition of a catalyst showed almost no degradation of TC after 140 minutes of simulated sunlight exposure. However, the V2C MXene prepared in Example 1 achieved a degradation rate of 72.15% after 140 minutes of simulated sunlight exposure.

[0147] Figure 14 The degradation rate curves of tetracycline hydrochloride (TC) by the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 under simulated sunlight are shown. The fitted mineralization rate of TC by the V2C MXene prepared in Example 1 under simulated sunlight is 0.00969 min -1 The blank experiment without adding catalyst showed almost no mineralization rate of TC under simulated sunlight irradiation.

[0148] Figure 15Figure 3 shows the organic carbon removal efficiency of tetracycline hydrochloride (TC) by the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 under simulated sunlight. After 80 minutes of simulated sunlight irradiation, the organic carbon removal rates of 40 mg / L TC degradation products by V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1) were 18%, 32%, and 42%, respectively. This demonstrates the authenticity of V2C MXene's direct TC degradation under simulated sunlight, and the sample prepared in Example 1 exhibits the best mineralization effect.

[0149] Figure 16 The degradation curves of tetracycline hydrochloride (TC) under near-infrared light for the layered V2C MXene prepared in Example 1, Comparative Examples 1, and 4 of the present invention are shown. Before exposure, a mixed solution of TC and the photocatalyst V2C MXene was magnetically stirred in a photochemical reactor, and the TC concentration was measured at regular intervals. The figure clearly shows that a blank experiment without catalyst showed almost no degradation of TC after 140 minutes of near-infrared light exposure, while the V2C MXene prepared in Example 1 achieved a degradation rate of 78.05% after 140 minutes of near-infrared light exposure.

[0150] Figure 17 The degradation rate curves of tetracycline hydrochloride (TC) under near-infrared light for the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention are shown. The fitted mineralization rate of TC for the V2C MXene prepared in Example 1 under near-infrared light is 0.01260 min -1 The blank experiment without catalyst showed almost no mineralization rate for TC under near-infrared light. This is due to the surface plasmon effect of V2C MXene, which enhances the light absorption in the near-infrared range and thus enhances the photocatalytic performance under near-infrared light.

[0151] Figure 18 Figure 3 shows the organic carbon removal efficiency of tetracycline hydrochloride (TC) under near-infrared light for the layered V2C MXene prepared in Example 1, Comparative Example 1, and Comparative Example 4. After 80 minutes of near-infrared light irradiation, the organic carbon removal rates of 40 mg / L TC degradation products by V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4), and V2C-BH (Example 1) were 15%, 35%, and 41%, respectively. This demonstrates the authenticity of V2C MXene's direct TC degradation under near-infrared light, and the sample prepared in Example 1 exhibits the best mineralization effect.

[0152] Figure 19The EPR spectra of the layered V2C MXene prepared in Example 1 and Comparative Example 1 of the present invention are shown in the figure. The EPR signals caused by defects appear when the g value is about 2.003. Among them, the V2AlC signal is weaker than that of V2C-HF (Comparative Example 1) and V2C-BH (Example 1), while the V2C-BH signal is the strongest. This shows that defects exist in the three samples of V2AlC, V2C-HF and V2C-BH. This is because after the secondary etching of V2C-BH, NaBH4 hinders the oxidation reaction of transition metal V, reduces the number of OH and F end groups on the surface of V2C-BH, exposes more defects, and stores e inside the crystal. - , surface storage h + .

[0153] Figure 20 The layered V2C MXene prepared in Example 1 of the present invention is + The EPR spectrum of DMPO-h is shown in the figure. The EPR spectrum of DMPO-h is shown in the figure. + Characteristic signal, the local enlarged image shows that its intensity decreases with the extension of the test time, and the clear DMPO-h can be captured at 0min in the dark light. + Characteristic peak signal, proving that V2C-BH itself stores a large amount of h + , and it is not generated by external stimulation, which also shows that the surface of V2C-BH crystal stores a large amount of h + The h stored in the V2C MXene catalyst was estimated by the quantum spin number obtained by EPR. + The concentration was 18.13 μmol g -1 .

[0154] Figure 21 The absorbance change diagram of the methylene blue decolorization experiment of the layered V2C MXene prepared in Example 1 of the present invention under dark light. The e stored in V2AlC, V2C-HF (Comparative Example 1) and V2C-BH (Example 1) were calculated by absorbance. - The concentrations were 37.74 μmol g -1 , 99.25 μmol g -1 and 106.37 μmol g -1 , indicating that after secondary etching with NaBH4 alkaline solution, the surface terminal content of V2C MXene is reduced, resulting in more defective active sites, allowing holes and electrons to be stored in the crystal.

[0155] Figure 22Figure 1 shows the capture of TC active species by the layered V2C MXene prepared in Example 1 of the present invention under dark light. It can be seen that the catalytic activity of V2C-BH is significantly inhibited after the addition of sodium oxalate (NaC2O4) and tert-butyl alcohol (tBuOH), while the catalytic activity of V2C-BH is somewhat inhibited after the addition of L-ascorbic acid (C6H8O4) and copper sulfate (CuSO4), proving that the degradation experiment under dark light has a significant impact on the catalytic activity of V2C-BH. + and ·OH are the main active species, ·O2 - and e - as a secondary active species.

[0156] Figure 23 Figure 2 shows the degradation of other pollutants by the layered V2C MXene prepared in Example 1 under dark light. In 80 minutes in the dark, V2C-BH degraded 20 mg / L methylene blue (MB) by 99.03%, 10 mg / L ciprofloxacin (CIP) by 52.49%, and 10 mg / L rose bengal (RhB) by 23.19%. This demonstrates that V2C-BH possesses broad-spectrum dark catalytic performance.

[0157] Figure 24 Figure 2 shows the degradation of other pollutants by the layered V2C MXene prepared in Example 1 under simulated visible light. Under simulated sunlight conditions for 80 minutes, V2C-BH degraded 20 mg / L methylene blue (MB) by 84.82%, 10 mg / L ciprofloxacin (CIP) by 76.09%, and 10 mg / L rose bengal (RhB) by 28.95%, demonstrating that V2C-BH possesses broad-spectrum catalytic performance.

[0158] Figure 25 The UV-visible diffuse reflectance spectra of the layered V2C MXene prepared in Example 1, Comparative Example 1 and Comparative Example 4 of the present invention are shown in Figure 1. In the UV-visible-near infrared spectrum, V2C-HF (Comparative Example 1), V2C-OH (Comparative Example 4) and V2C-BH (Example 1) show stronger light absorption than V2AlC, and the absorption increases in sequence. The local magnified image shows obvious absorption peaks at 405nm and 955nm. This is because the storage of h + and e - The V2C MXene exhibits LSPR effects similar to those of nanometals, such as the transverse surface plasmon resonance (TE) and longitudinal surface plasmon resonance (TM), which enhance the light response. Therefore, the reduction of surface ·OH and ·F end groups makes V2C-BH have stronger light absorption.

[0159] Figure 26This is the EPR spectrum of DMPO-·OH in the layered V2C MXene prepared in Example 1 of the present invention under simulated sunlight conditions. The EPR spectrum of DMPO-·OH shows that almost no signal is captured under dark conditions, but after illumination, four strong EPR signal peaks with an intensity ratio of 1:2:2:1 appear, corresponding to the characteristic peaks of DMPO-·OH. The intensity of the characteristic peaks gradually increases with the extension of illumination time. This shows that the e in the V2C MXene bulk phase under illumination - Excitation can generate ·OH.

[0160] Figure 27 The layered V2C MXene prepared in Example 1 of the present invention is DMPO-·O2 under simulated sunlight conditions. - EPR spectrum of DMPO-·O2 - The EPR spectrum of the DMPO-·O2 was observed under dark conditions, but the corresponding DMPO-·O2 was observed after illumination. - , four EPR signal peaks with an intensity ratio of 1:1:1:1, and the characteristic peak intensity gradually increases with the extension of illumination time. This shows that the e in the V2C MXene bulk phase under illumination - Transition occurs to produce O2 - , O2 - Free radicals can further react and transform into ·OH and continue to participate in the mineralization reaction.

[0161] Figure 28 The layered V2C MXene prepared in Example 1 of the present invention is DMPO-h + EPR spectrum of DMPO-h + There is an obvious characteristic peak signal, and its intensity increases with the extension of illumination time to 10min and 20min. + The characteristic peak signal shows an obvious downward trend. This shows that the h + It can provide V2C with stronger oxidative activity.

[0162] Figure 29Schematic diagram of possible degradation pathways and intermediate products of TC by the layered V2C MXene prepared in Example 1 of the present invention under dark light. The figure shows three possible degradation pathways under dark light. The reaction pathways under dark light may be pathway 1, pathway 2, and pathway 3. In pathway 1, TC (m / z = 445) loses methyl and water and produces hydroxyl groups to generate a product (m / z = 415). Then, after the carbon ring is cracked, a product (m / z = 318) is generated. Subsequently, a decarboxylation reaction occurs to generate a product (m / z = 274). In pathway 2, TC (m / z = 445) first generates a ketone group and a hydroxyl group by cleavage of the double bond to obtain a product (m / z = 461). Then, the methyl group of the tertiary amine is attacked by the hydroxyl group, the hydroxyl group is changed, and the ketone group is also stripped off to generate a product (m / z = 274). The product (m / z = 459) then loses the amide group and hydroxyl group to form the product (m / z = 400). Following the ring-opening reaction and cleavage of the carbonyl group, the product (m / z = 271) and the product (m / z = 231) are gradually formed. Path 3: The double bond on the carbon ring in the product (m / z = 461) breaks, forming a hydroxyl group, generating the product (m / z = 477). The hydroxyl group attacks dimethylamine to form the product (m / z = 448), which then undergoes a ring-opening reaction to form carboxyl and hydroxyl groups, generating the product (m / z = 496). Further ring-opening reactions gradually produce small molecule products (m / z = 461). This is then further mineralized into small organic molecules and ultimately converted into CO2, H2O, and small organic molecules.

[0163] Figure 30 This is a schematic diagram of the catalytic mechanism of the layered V2C MXene prepared in Example 1 of the present invention under dark light. Combining the above conclusions, it can be concluded that the V-Al bond is destroyed during the etching process of V2AlC, and Al atoms are separated from the system to form Al vacancies. and During the formation process, holes (h + ), holes are randomly distributed and stored in the interlayer and surface of V2C MXene, and in the positive potential center of the interlayer It will attract the free electrons generated during the etching process. Due to the localized hole state between the layers, an electrostatic field will be generated, resulting in the interlayer electrons (e - ) are bound in the interlayer electric field, so that some electrons (e - ). Combined Figure 26 , it can be obtained that the holes (h + ) before the interlayer electrons (e - ) release, mineralizing and degrading macromolecular organic matter into small molecular organic matter and CO2 and H2O (h + +TC→CO2+H2O;h + +H2O→H ++·OH). The consumption of holes relieves the electrostatic field generated by the localized hole state between the layers, and then binds the electrons (e - ) escapes later and forms O2 with dissolved oxygen - , O2 - Formation of H2O2(·O2 - +2H + +e - →H2O2), H2O2 can further form ·OH(H2O2+·O2 - → OH+OH - +O2), further participating in the degradation and mineralization of TC (·OH+TC→CO2+H2O). Since the reduction of NaBH4 slows down the oxidation of V, the total amount of surface end groups is reduced, and the storage of holes and electrons is increased, V2C MXene exhibits good dark catalytic performance in the dark.

[0164] 2. Storage Part of Layered V2C MXene Energy Storage Catalytic Materials

[0165] Comparative Example 1:

[0166] The layered V2C MXene energy storage catalytic material prepared in Example 1 of the preparation part of the layered V2C MXene energy storage catalytic material was directly used as a comparative example without any preservation treatment and was named V2C(0M)-0day.

[0167] Comparative Example 2:

[0168] The layered V2C MXene energy storage catalytic material prepared in Example 1 of the preparation part of the layered V2C MXene energy storage catalytic material was stored at room temperature in a dry and light-proof environment for 30 days and named V2C(0M)-30day.

[0169] Example 1:

[0170] The layered V2C MXene energy storage catalytic material prepared in Example 1 was dispersed in 50 ml of a 5.5 M supersaturated sodium chloride solution and stored at room temperature in the dark. Upon use, the vanadium carbide MXene was washed and separated from the supersaturated sodium chloride solution and vacuum-dried at 65°C for 12 hours to obtain a layered vanadium carbide MXene powder. The sample stored for 30 days was designated V2C(5.5M)-30day.

[0171] Example 2:

[0172] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 2.5 M. Other storage conditions are the same. The sample stored for 30 days is named V2C (2.5 M)-30day.

[0173] Example 3:

[0174] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 5.0 M, and the other storage conditions are the same.

[0175] Example 4:

[0176] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 4.5 M, and the other storage conditions are the same.

[0177] Example 5:

[0178] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 4.0 M, and the other storage conditions are the same.

[0179] Example 6:

[0180] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 3.5 M, and the other storage conditions are the same.

[0181] Example 7:

[0182] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 3.0 M, and the other storage conditions are the same.

[0183] Example 8:

[0184] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 2.0 M, and the other storage conditions are the same.

[0185] Example 9:

[0186] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 1.5 M, and the other storage conditions are the same.

[0187] Example 10:

[0188] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 1.0 M, and the other storage conditions are the same.

[0189] Example 11:

[0190] The difference from Example 1 is that the concentration of the supersaturated sodium chloride aqueous solution is 0.5 M, and the other storage conditions are the same.

[0191] After the above comparative example 2 and each example were stored for 30 days, 50 mg of vanadium carbide MXene powder was weighed and dispersed in 50 mL of TC solution. A 50 mL quartz test tube was used as a container and placed in an XPA-7 photochemical reactor. The reaction was carried out under conditions of darkness, simulated sunlight (500 W xenon lamp), and near-infrared light (500 W xenon lamp + 780 nm filter) and magnetic stirring (1000 r min) respectively. -1The photocatalytic reaction was started immediately. During the reaction, 3 mL of the upper suspension of the test tube was taken every 20 min and centrifuged (4000 r·min -1 After removing the photocatalyst powder (1 min), the absorbance curve of the supernatant was tested using a UV-visible spectrophotometer. The absorbance value at 358 nm reflected the change in TC concentration in the supernatant, verifying the catalytic stability of the V2C MXene obtained in step 3.

[0192] Figure 31 The XRD patterns of V2C MXene in Example 1, Comparative Example 1, and Comparative Example 2 are stored in the present invention. The XRD patterns of Comparative Example 1, Example 1, and Comparative Example 2 are shown from top to bottom. Figure 1 It is shown in the figure that after multi-step etching, the diffraction peaks of V2AlC at 13.4° and 41.2° are consistent with the characteristic diffraction peaks of the hexagonal V2AlC precursor (JCPDS No.29-0101), corresponding to the (002) and (103) crystal planes of the hexagonal V2AlC, respectively. In addition, the characteristic diffraction peaks of the comparative example 1 at 2θ=6.2° and 9.1° correspond to the characteristic diffraction peaks of the few-layer (002) crystal plane and the multi-layer (004) crystal plane of V2C, respectively (V2C(0M)-0day); Example 1 can still maintain a stable phase component (V2C(5.5M)-30day) after being stored in a supersaturated sodium chloride solution for 30 days, and the crystallinity is complete; while the characteristic diffraction peak of V2C in the comparative example 2 is no longer obvious after being stored at room temperature for 30 days (V2C(0M)-30day), indicating that its phase component may have changed. It shows that the secondary treatment of sodium borohydride alkaline solution and the storage method of supersaturated sodium chloride solution are of great significance to protect and maintain the crystallinity of V2C MXene.

[0193] Figure 32 This is the SEM spectrum of V2C (0M)-30 days in comparative example 2 of the present invention. The layered structure of V2C MXene in the figure is damaged, the edge structure is broken into small pieces, and the layers are sticky. Figure 5 In comparison, it is shown that the structure of V2C MXene prepared by HF wet etching is easily destroyed at room temperature.

[0194] Figure 33 This is an SEM image of V2C (2.5M) at 30 days in Example 2 of the present invention. The V2C MXene layered structure appears damaged at the edges, but the overall layered structure is distinct, exhibiting an accordion-like structure with approximately 14 layers and a thickness of 7.6 μm. This indicates that the sodium chloride solution has a positive effect on maintaining the structural stability of the V2C MXene.

[0195] Figure 34This is a SEM image of V2C (5.5M) at 30 days in Example 1. The image shows the complete layered, accordion-like structure of V2C MXene, indicating that storage in a supersaturated sodium chloride solution effectively preserves the structural integrity of V2C MXene, which may be of great value in maintaining the catalytic stability of V2C MXene.

[0196] Figure 35 The following are the degradation curves of tetracycline hydrochloride (TC) in the dark for V2C MXene in Comparative Examples 1, 2, Examples 1, and 2 of the present invention. As can be seen from the figure, under the same conditions, the TC degradation rates of Comparative Example 1 (V2C (0M) - 0 day) and Example 1 (V2C (5.5M) - 30 day) after 140 minutes were 57.91% and 53.64%, respectively. In contrast, Example 2 (V2C (2.5M) - 30 day), which was stored in an unsaturated salt solution, achieved a TC degradation rate of 42.97% after 140 minutes. Comparative Example 2, stored at room temperature, failed to catalyze TC degradation properly (V2C (0M) - 30 day), indicating that the chemical stability of V2C MXene not stored in a saturated salt solution changes after prolonged storage.

[0197] Figure 36 The degradation curves of tetracycline hydrochloride (TC) under simulated sunlight for the V2C MXene in Comparative Examples 1, 2, Examples 1, and 2 of the present invention are shown. As can be seen from the figure, under the same conditions, the newly prepared Comparative Example 1 (V2C (0M) - 0 day) and Example 1 stored in a supersaturated salt solution (V2C (5.5M) - 30 days) showed TC degradation rates of 72.15% and 68.32% after 140 minutes, respectively. In contrast, Example 2 (V2C (2.5M) - 30 days), stored in an unsaturated salt solution, showed a TC degradation rate of 42.76% after 140 minutes. Comparative Example 2, stored at room temperature, failed to catalyze TC degradation properly (V2C (0M) - 30 days), indicating that the chemical stability of V2C MXene changes after prolonged storage at room temperature.

[0198] Figure 37This is the degradation curve of tetracycline hydrochloride (TC) prepared in step 3 of Comparative Example 1, Comparative Example 2, Example 1 and Example 2 of the present invention under near-infrared light. As can be seen from the figure, under the same conditions, the newly prepared Comparative Example 1 (V2C (0M) -0 day) and the Example 1 stored in a supersaturated salt solution (V2C (5.5M) -30 day) have TC degradation rates of 78.05% and 69.32% after 140 minutes, respectively. While in Example 2 (V2C (2.5M) -30 day) stored in an unsaturated salt solution, the TC degradation rate in 140 minutes is 53.18%. Comparative Example 2 at room temperature cannot catalyze the degradation of TC normally (V2C (0M) -30 day). Figure 7 and Figure 8 , indicating that supersaturated salt solution can maintain the catalytic stability of V2C MXene.

Claims

1. Application of a layered V2C MXene energy storage catalytic material in the degradation of organic pollutants; a method for preparing the layered V2C MXene energy storage catalytic material, comprising the following steps: Step 1, adding V2AlC powder to HF solution to obtain a mixed system; Step 2, stirring and etching the mixed system under heating and sealing conditions to obtain a reaction solution; Step 3, washing the reaction solution until the pH of the obtained supernatant is 6-7 to obtain layered V2C MXene powder; Step 4: Add the layered V2C MXene powder to a mixed solution of sodium borohydride and sodium hydroxide, stir and etch to obtain a mixed reaction solution; In step 5, the mixed reaction liquid is washed, separated, and dried to obtain a layered V2C MXene energy storage catalytic material.

2. The use of the layered V2C MXene energy storage catalytic material according to claim 1 in the degradation of organic pollutants, characterized in that: In step 1, the mass fraction of the HF solution is 40% to 49%.

3. The use of the layered V2C MXene energy storage catalytic material according to claim 1 in the degradation of organic pollutants, characterized in that: In step 2, the etching time is 48 to 72 hours.

4. The use of the layered V2C MXene energy storage catalytic material according to claim 1 in the degradation of organic pollutants, characterized in that: In step 4, the etching time is 20 to 24 h.

5. The use of the layered V2C MXene energy storage catalytic material according to claim 1 in the degradation of organic pollutants, characterized in that: In step 4, in the mixed solution of sodium borohydride and sodium hydroxide, the molar ratio of sodium borohydride to sodium hydroxide is (0.05-0.9):0.

5.

6. The use of the layered V2C MXene energy storage catalytic material in the degradation of organic pollutants according to claim 1, characterized in that: In step 5, drying is performed at 60-75° C. in vacuum for 10-14 h.

Images