Metal element coated MXene composite material and preparation method thereof

Abstract

The invention provides a metal element coated MXene composite material and a preparation method thereof. The preparation method comprises the following steps: S1, adding MXene and a metal salt solution into an ethylene glycol solution, and stirring to enable metal ions to be uniformly attached to the surface of MXene; s2, an alkaline solution and a reducing agent are sequentially added into the solution in the step S1 for reaction, and metal ions attached to the surface of MXene are reduced into metal elementary substances; and S3, carrying out centrifugal washing on the solution obtained in the step S2, and drying the centrifugally washed precipitate to obtain the metal element coated MXene composite material. In the metal-coated MXene composite material prepared by the method, metal elements are uniformly distributed on the surface of MXene, and the metal-coated MXene composite material has good applicability to various metal elements.

Description

Technical Field

[0001] The present invention relates to the field of material preparation, and in particular to a metal element@MXene composite material and a preparation method thereof. Background Art

[0002] In the continuous exploration of materials science, the emergence of new materials continues to rewrite the technical landscape in various fields. MXene, as a new family of two-dimensional carbides and carbonitrides, has attracted widespread attention since its advent due to its outstanding performance. Its structural formula is M n+1 X n T x (n=1-3), where M is an early transition metal (such as Sc, Ti, V, Cr, Mo, Nb, etc.), X is C, N or CN, T x Indicates surface functional groups (-F, -OH, -O), such as Ti2CT x 、Nb2CT x MXene materials have excellent performance in mechanical strength, oxidation resistance, hydrophilicity, chemical stability, etc. In recent years, they have attracted much attention in the fields of energy storage, electrode materials, water treatment, sensors, thermal conductive materials, etc.

[0003] As the research on MXene deepens, researchers are actively engaged in the preparation and performance control of MXene-related composite materials. In this process, loading metal elements on MXene has become a very promising approach to prepare composite materials. However, current loading technologies generally face many challenges: Figure 1 As shown in the figure, the unique accordion structure (layered stacking structure) of MXene makes it difficult for metal elements to adhere and the uniformity is insufficient.

[0004] Taking the preparation method of MoSe2 / MXene composite materials disclosed in Chinese patent publication number CN115995535A as an example, this method first disperses Ti3C2 MXene powder in aqueous solvent A, ultrasonically treats it, and separates the solid-liquid phase to obtain a liquid phase component. Then, Se powder is dispersed in hydrazine hydrate and the liquid phase component is added to form solution A. Sodium molybdate is then dispersed in aqueous solvent B and stirred and added to solution A to obtain a precursor solution. Finally, a hydrothermal reaction is carried out at 190-210°C to produce the composite material. In this process, the excessively high reaction temperature (190-210°C) not only exacerbates the oxidative decomposition of functional groups on the MXene surface, destroying the stability of the layered structure, but also causes the metal ions to rapidly aggregate on the MXene surface due to thermal drive, further exacerbating the uneven loading. Moreover, this method is only applicable to the MoSe2 and MXene system and lacks universality for the composites of other metals and MXenes.

[0005] It can be seen from this that there is an urgent need to develop a simpler and more universal preparation method for uniformly loaded metals. Summary of the Invention

[0006] In response to the problems of uneven loading and lack of versatility in the prior art, the present invention provides a metal element@MXene composite material and a preparation method thereof.

[0007] The technical method of the present invention is as follows:

[0008] A method for preparing a metal element@MXene composite material, comprising:

[0009] S1. Add MXene and metal salt solution to ethylene glycol solution and stir to make the metal ions evenly adhere to the MXene surface;

[0010] S2. Adding an alkaline solution and a reducing agent to the solution in step S1 in sequence to react and reduce the metal ions attached to the surface of the MXene to metal elements;

[0011] S3. The solution in step S2 is centrifuged and washed, and the precipitate obtained by centrifugal washing is dried to obtain a metal element@MXene composite material.

[0012] In step S1, MXene is M n+1 X n T x , M is one or more of scandium, titanium, vanadium, chromium, molybdenum, and niobium, X is one or more of carbon, nitrogen, and a carbon-nitrogen blend, T x The surface functional groups include one or more of fluorine, hydroxyl, and oxygen, and n is 1 to 3. The metal salt solution includes one or more of a cobalt salt solution, a nickel salt solution, and a ferrous salt solution; wherein the cobalt salt solution includes a cobalt chloride solution and / or a cobalt sulfate solution, the nickel salt solution includes a nickel chloride solution and / or a nickel sulfate solution, and the ferrous salt solution includes a ferrous chloride solution and / or a ferrous sulfate solution. The ratio of the MXene, metal salt solution, and ethylene glycol solution is 1 to 2 g: 1 to 2 g: 200 mL. Magnetic stirring is used for stirring.

[0013] In step S2, the alkaline solution is a sodium hydroxide solution with a concentration of 2 to 3 mol / L. The alkaline solution controls the pH of the solution in step S1 to be above 11. The reducing agent is hydrazine hydrate, and the ratio of hydrazine hydrate to metal salt solution is 5 mL:0.1 to 2 g. The reaction temperature is 60 to 80°C, the reaction time is 0.5 to 2 hours, and the reaction is stirred magnetically.

[0014] In step S3, the centrifugal speed is 3000-4000 rpm, the centrifugal time is 2-4 minutes, and the drying is freeze-drying at a temperature of -40--20°C for 10-14 hours.

[0015] The present invention also provides a metal element@MXene composite material, which is obtained by the above-mentioned preparation method.

[0016] The beneficial effects of the present invention are:

[0017] First, the present invention first adds MXene and a metal salt solution to an ethylene glycol solution. This is because: first, in the ethylene glycol solution, the electrostatic interaction between the electronegative surface of the MXene and the metal ions promotes the initial adsorption of the ions, forming a uniform pre-adsorption layer; second, the hydroxyl and ether bonds in the ethylene glycol molecules can form coordination complexes with the metal ions, effectively preventing metal ion aggregation and promoting uniform distribution of the metal ions on the MXene surface; third, the oxygen solubility of the ethylene glycol solution is significantly lower than that of water, which can slow the oxidation rate of the MXene. Furthermore, ethylene glycol can release reducing intermediates (such as glyoxal) under reaction conditions, further inhibiting MXene oxidation. Subsequently, an alkaline solution and a reducing agent are added for reduction, reducing the metal ions uniformly attached to the MXene surface to elemental metal. Finally, the precipitate is washed by centrifugation and dried to obtain a metal element@MXene composite material. The metal element@MXene composite prepared by this method has a uniform distribution of the metal elements on the MXene surface and has good applicability for a variety of metal elements (such as Fe, Cu, Mo, etc.).

[0018] 2. The operation process of the present invention is simple and only involves basic operations such as solution mixing and reduction reaction.

[0019] 3. The reaction conditions of the present invention are mild, and the entire process is carried out at room temperature to 80°C and normal pressure, without the need for high temperature and high pressure equipment.

[0020] 4. The present invention uses magnetic stirring to uniformly disperse metal ions and achieve uniform adhesion of metal ions on the MXene surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the accordion structure diagram of MXene;

[0022] Figure 2 Fe@Ti3C2T in Example 1 x Scanning electron microscopy (SEM) image of MXene;

[0023] Figure 3 Ni@Ti3C2T of Example 2 x Scanning electron microscopy (SEM) image of MXene;

[0024] Figure 4 Ni@Ti3C2T of Example 2 x Energy dispersive X-ray spectroscopy (EDS) of MXene;

[0025] Figure 5 Fe@Ti3C2T in Example 3 x Scanning electron microscopy (SEM) image of MXene;

[0026] Figure 6 Fe@Ti3C2T in Example 3 x Energy dispersive X-ray spectroscopy (EDS) diagram of MXene. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] The present invention provides a method for preparing a metal element@MXene composite material, comprising:

[0029] S1. Add MXene and metal salt solution to ethylene glycol solution and stir to make the metal ions evenly adhere to the MXene surface.

[0030] In step S1, MXene is M n+1 X n T x , M is one or more of scandium, titanium, vanadium, chromium, molybdenum, and niobium, X is one or more of carbon, nitrogen, and a carbon-nitrogen blend, T x is a surface functional group, which includes one or more of fluorine, hydroxyl, and oxygen, and n is 1 to 3. It is preferably Ti3C2T x .

[0031] In step S1, the metal salt solution includes one or more of a cobalt salt solution, a nickel salt solution, and a ferrous salt solution. The cobalt salt solution includes a cobalt chloride solution and / or a cobalt sulfate solution, the nickel salt solution includes a nickel chloride solution and / or a nickel sulfate solution, and the ferrous salt solution includes a ferrous chloride solution and / or a ferrous sulfate solution.

[0032] In step S1, the ratio of MXene, metal salt solution, and ethylene glycol solution is 1-2g:1-2g:200mL. For example, the ratios of MXene, metal salt solution, and ethylene glycol solution are 1g:1g:200mL, 1.2g:1.2g:200mL, and 1.5g:1.5g:200mL. The metal ion loading is determined by the active sites on the MXene surface. Metal ions attach to the active sites, nucleate, and grow. Too low a metal ion concentration results in too little loading, while too high an ion concentration causes overly large metal particles, affecting the performance of the loaded product. MXene itself does not chemically react with metal ions and serves as a loading substrate.

[0033] In step S1, magnetic stirring is used for stirring. The stirring temperature can be 10-35°C, the stirring time is 10-30 minutes, and the stirring rate is 800-1000 rpm. Specifically, MXene and metal salt solution are added to the ethylene glycol solution and placed in a beaker. The beaker is placed on a magnetic stirring device and magnetically stirred for a certain period of time until the MXene is evenly dispersed. This step evenly disperses the MXene, making the reaction uniform and preventing agglomeration. It also allows the metal ions to evenly adhere to the MXene surface, which is conducive to the reduction reaction.

[0034] First, in the present invention, the electronegative surface of MXene is bonded to ions (e.g., Ni 2+ ) promotes the initial adsorption of ions and forms a uniform ion pre-adsorption layer. The electronegativity comes from the functional groups such as hydroxyl (-OH), oxygen (-O), and fluorine (-F) on the surface of MXene. Second, MXene (such as Ti3C2T x ) easily reacts with water molecules or dissolved oxygen in water, resulting in surface oxidation (generating TiO2, etc.), which destroys its conductivity and structural stability. The oxygen solubility of ethylene glycol is much lower than that of water, which can significantly slow down the oxidation rate of MXene, and ethylene glycol can release reducing intermediates (such as glyoxal) under high temperature or catalytic conditions, further inhibiting the oxidation of MXene. The dielectric constant of ethylene glycol (about 37.7) is lower than that of water (about 80), which weakens the polarization effect of the solvent and is conducive to the electrostatic repulsion between MXene sheets to maintain a dispersed state. Third, the hydroxyl group (-OH) and ether bond (COC) in the ethylene glycol molecule can react with metal ions (such as Ni 2+ ) to form coordination complexes (such as [Ni(OCH2CH2OH)6] 2+ ), prevent ion aggregation and promote uniform distribution.

[0035] S2. Alkaline solution and reducing agent are sequentially added to the solution of step S1 to react and reduce the metal ions attached to the surface of MXene to metal elements.

[0036] In step S2, the alkaline solution is a sodium hydroxide solution with a concentration of 2 to 3 mol / L. The alkaline solution controls the pH value of the solution in step S1 to be above 11, thereby increasing the reducing power of the reducing agent added in the next step and making the reduction reaction more likely to occur.

[0037] In step S2, the reducing agent is hydrazine hydrate, and the ratio of hydrazine hydrate to metal salt solution is 5 mL:0.1-2 g.

[0038] In step S2, the reaction temperature is 60-80°C for 0.5-2 hours, with magnetic stirring. The stirring rate is 800-1000 rpm. Preferably, the reaction temperature is 65°C, 70°C, or 75°C, and the reaction time is 1 hour or 1.5 hours. In this step, the strong reducing properties of hydrazine hydrate under alkaline conditions reduce the metal ions uniformly attached to the MXene surface to the elemental metal.

[0039] The present invention adopts redox reaction. Hydrazine hydrate has strong reducing property under alkaline conditions. Hydrazine hydrate reduces metal ions to metal elements through electron transfer mechanism. The reducing ability of hydrazine hydrate comes from the breaking of NH bond and oxidation of nitrogen atoms in its molecules. In the reaction, hydrazine (N2H4) is oxidized to nitrogen (N2), while releasing electrons. Metal ions capture electrons and are reduced to metal elements. Taking nickel as an example, 2Ni 2+ +N2H4+4OH - →2Ni↓+N2↑+4H2O.

[0040] S3. The solution in step S2 is centrifuged and washed, and the precipitate obtained by centrifugal washing is dried to obtain a metal element@MXene composite material.

[0041] In step S3, the centrifugal speed is 3000-4000 rpm, the centrifugal time is 2-4 minutes, and the number of centrifugal washings is 3-5 times. The impurities remaining in the reaction are removed by centrifugation and deionized water multiple times.

[0042] In step S3, the drying is performed by freeze drying, the freeze drying temperature is -40 to -20°C, and the freeze drying time is 10 to 14 hours.

[0043] The present invention also provides a metal element@MXene composite material, which is obtained by the above-mentioned preparation method.

[0044] The present invention provides a metal element@MXene composite material as a catalyst for improving the performance of magnesium hydride hydrogen storage materials.

[0045] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0046] The present invention is described in detail below by way of examples and experimental examples, which are merely illustrative and do not limit the present invention in any way.

[0047] Example 1 Preparation of Ti3C2 MXene

[0048] The present invention provides a method for preparing Ti3C2 MXene, comprising the following steps:

[0049] Step 1: 1 g of Ti3AlC2 powder was added to 20 mL of 40% HF (Aladdin) solution, followed by magnetic stirring at 60°C for 24 h. After the reaction, the solution was centrifuged at 3500 rpm for 3 min, and the precipitate was collected and washed with deionized water. This step was repeated until the pH value was close to neutral (pH>6).

[0050] Step 2: Place the precipitate in a refrigerator (-30°C) for 12 hours, and then use a freeze dryer at -20 to -30°C for 12 hours to obtain Ti3C2T x MXene.

[0051] Example 2Fe@Ti3C2T x Preparation of MXene

[0052] The present invention provides a Fe@Ti3C2T x The preparation method of MXene comprises the following steps:

[0053] 0.1 g FeCl2·4H2O and 0.1 g Ti3C2T prepared in Example 1 were added x MXene was added to 20 ml of ethylene glycol and magnetically stirred for 10 minutes. After thorough mixing, 2.5 mol / L NaOH solution was added dropwise until the pH of the solution was greater than 11. Then 5 ml of N2H4·H2O solution was added and magnetically stirred at 70 ° C for 2 hours. After the reaction, the obtained solution was centrifuged and washed 5 times at a centrifuge speed of 3500 rpm for 3 minutes. The obtained precipitate was freeze-dried at -20 to -30 ° C for 12 hours to finally obtain Fe@Ti3C2T x MXene powder. Figure 2 As shown, the SEM image proves that Fe is successfully loaded on Ti3C2T x On MXene.

[0054] Example 3Ni@Ti3C2T x Preparation of MXene

[0055] The present invention provides a Ni@Ti3C2T x The preparation method of MXene comprises the following steps:

[0056] 0.1 g NiCl2·6H2O and 0.1 g Ti3C2T prepared in Example 1 were added. x MXene was added to 20 ml of ethylene glycol and magnetically stirred for 10 minutes. After thorough mixing, 2.5 mol / L NaOH solution was added dropwise until the pH of the solution was greater than 11. Then 5 ml of N2H4·H2O solution was added and magnetically stirred at 70 ° C for 1 hour. After the reaction, the obtained solution was centrifuged and washed 5 times at a centrifuge speed of 3500 rpm for 3 minutes. The obtained precipitate was freeze-dried at -20 to -30 ° C for 12 hours to finally obtain Ni@Ti3C2T x MXene powder. Figure 3 and 4 As shown, SEM and EDS images prove that Ni is successfully loaded on Ti3C2T x On MXene. Here, the purple in the EDS image represents Ni.

[0057] Example 4Fe@Ti3C2T x Preparation of MXene

[0058] The present invention provides a Fe@Ti3C2T x The preparation method of MXene comprises the following steps:

[0059] 0.1 g of FeSO4·7H2O and 0.1 g of Ti3C2T prepared in Example 1 were added. x MXene was added to 20 ml of ethylene glycol and magnetically stirred for 10 minutes. After thorough mixing, 2.5 mol / L NaOH solution was added dropwise until the pH of the solution was greater than 11. Then 5 ml of N2H4·H2O solution was added and magnetically stirred at 70 ° C for 2 hours. After the reaction, the obtained solution was centrifuged and washed 5 times at a centrifuge speed of 3500 rpm for 3 minutes. The obtained precipitate was freeze-dried at -20 to -30 ° C for 12 hours to finally obtain Fe@Ti3C2T x MXene powder. Figure 5 and 6 As shown, SEM and EDS images prove that Fe is successfully loaded on Ti3C2T x On MXene. Here, the purple in the EDS image represents Fe.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a metal element@MXene composite material, characterized in that: include: S1. Add MXene and metal salt solution to ethylene glycol solution and stir to make the metal ions evenly adhere to the MXene surface; S2. Adding an alkaline solution and a reducing agent to the solution in step S1 in sequence to react and reduce the metal ions attached to the surface of the MXene to metal elements; S3. The solution in step S2 is centrifuged and washed, and the precipitate obtained by centrifugal washing is dried to obtain a metal element@MXene composite material.

2. The preparation method according to claim 1, characterized in that The MXene is M n+1 X n T x , M is one or more of scandium, titanium, vanadium, chromium, molybdenum, and niobium, X is one or more of carbon, nitrogen, and a carbon-nitrogen blend, T x is a surface functional group, which includes one or more of fluorine, hydroxyl, and oxygen, and n is 1 to 3.

3. The preparation method according to claim 1, characterized in that The metal salt solution includes one or more of a cobalt salt solution, a nickel salt solution, and a ferrous salt solution; wherein, The cobalt salt solution includes a cobalt chloride solution and / or a cobalt sulfate solution, the nickel salt solution includes a nickel chloride solution and / or a nickel sulfate solution, and the ferrous salt solution includes a ferrous chloride solution and / or a ferrous sulfate solution.

4. The preparation method according to claim 1, characterized in that The ratio of the MXene, metal salt solution, and ethylene glycol solution is 1-2 g: 1-2 g: 200 mL.

5. The preparation method according to claim 1, characterized in that The stirring is performed by magnetic stirring.

6. The preparation method according to claim 1, characterized in that The alkaline solution includes sodium hydroxide solution and / or potassium hydroxide, and the concentration of the alkaline solution is 2-3 mol / L. The alkaline solution controls the pH value of the solution in step S1 to be above 11.

7. The preparation method according to claim 1, characterized in that The reducing agent is hydrazine hydrate, and the ratio of hydrazine hydrate to metal salt solution is 5mL:0.1-2g.

8. The preparation method according to claim 1, characterized in that The reaction temperature in step S2 is 60-80° C., the reaction time is 0.5-2 h, and the reaction is carried out using magnetic stirring.

9. The preparation method according to claim 1, characterized in that The centrifugal speed in step S3 is 3000-4000 rpm, and the centrifugal time is 2-4 minutes. The drying in step S3 is performed by freeze drying, the freeze drying temperature is -40 to -20°C, and the freeze drying time is 10 to 14 hours.

10. A metal element@MXene composite material, characterized in that: The metal element@MXene composite material is obtained by the preparation method according to any one of claims 1 to 9.

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