Layer-by-layer assembled 2D-2D Schottky heterojunction composite material and preparation method and application thereof

Abstract

The invention provides a layer-by-layer assembled 2D-2D Schottky heterojunction composite material as well as a preparation method and application thereof, and relates to the technical field of nano composite electromagnetic microwave absorbing materials. The layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, and is prepared by the following steps: adsorbing p-region metal ions on the surfaces of MXene nanosheets through electrostatic adsorption, and then growing 2D SnSe2 semiconductor nanosheets on the surfaces of the interconnected MXene nanosheets in situ through a chemical vapor deposition-selenylation process to form the Schottky heterojunction composite material. The semiconductor SnSe2 nanosheets are anchored on the surfaces of the MXene nanosheets and interconnected MXene to form a 3D porous conductive network path, so that the impedance matching characteristic of the composite material can be optimized, and more electromagnetic waves can enter the composite material to be absorbed and converted by multiple loss mechanisms inside the composite material.

Description

Technical Field

[0001] This invention relates to the technical field of nanocomposite electromagnetic microwave absorbing materials, specifically to a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of communication technology, the Internet of Things, and military stealth technology, electromagnetic waves have received increasing attention as an information transmission medium. However, the miniaturization of electronic devices and the high-power radiation of 5G / 6G communication base stations have led to increasingly serious electromagnetic interference and pollution problems. Developing high-performance electromagnetic wave absorbing materials has become a research hotspot in the scientific field. Ideal electromagnetic wave absorbing materials possess characteristics such as thinness, low density, wide response bandwidth, and high absorption intensity. Two-dimensional materials such as graphene and Ti3C2T... x MXenes, transition metal sulfides, and other materials exhibit great potential in electromagnetic wave energy attenuation due to their unique layered structure, high specific surface area, and excellent physicochemical properties. However, single-component materials suffer from low loss capacity and poor impedance matching characteristics, making it difficult for their electromagnetic wave absorption performance to meet practical application requirements.

[0003] Constructing heterojunctions is considered an effective strategy for optimizing microwave absorption performance. Among them, Schottky heterojunctions (formed by the contact of metallic and semiconductor materials) can promote charge separation and redistribution under the influence of a built-in electric field. Under the influence of an alternating electric field, bound charges migrate and accumulate at the interface of these components, forming a macroscopic dipole moment. This process consumes the energy of the electromagnetic field, thereby achieving the absorption of electromagnetic waves and significantly enhancing dielectric loss. Traditional physical mixing methods struggle to precisely control the interface and microstructure of heterojunctions, leading to unstable performance. Layer-by-layer assembly technology enables controllable assembly of materials at the molecular level, providing an ideal strategy for constructing precisely structured, clearly defined 2D-2D heterostructures. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a simple, structurally controllable, and high-performance layer-by-layer assembled 2D-2D Schottky heterojunction composite material, along with its preparation method and applications, solving the current limitations of Ti3C2T... x MXene materials face technical challenges such as impedance mismatch and low dielectric polarization response intensity, which leads to poor absorption efficiency.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A layer-by-layer assembled 2D-2D Schottky heterojunction composite material, wherein the layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, comprising: p-region metal ions are adsorbed on the surface of MXene nanosheets by electrostatic adsorption, and then 2D SnSe2 semiconductor nanosheets are grown in situ on the interconnected MXene nanosheets by chemical vapor deposition-selenization process to form a Schottky heterojunction composite material.

[0006] Preferably, the SnSe2 nanosheets have abundant grain boundaries, and the interconnected MXene nanosheets form a 3D porous conductive network structure.

[0007] Preferably, the thickness of the SnSe2 nanosheet is 1 μm.

[0008] Preferably, the 2D-2D Schottky heterojunction is formed by in-situ growth of SnSe2 nanosheets on the surface of MXene nanosheets via pyrolysis selenization measurement.

[0009] A method for preparing layer-by-layer assembled 2D-2D Schottky heterojunction composite materials includes the following steps: S1. The 2D transition metal carbide Ti3AlC2MAX phase raw material was added in batches to a mixed etching solution formed by hydrochloric acid, hydrofluoric acid and deionized water for etching. After the reaction was completed, the raw material was centrifuged, washed with water and added to a LiCl intercalation ion solution. After intercalation, the raw material was repeatedly washed with water and centrifuged until the upper solution was turbid. Centrifugation was continued until a single-layer / few-layer MXene nanosheet suspension was obtained. S2. SnCl2·6H2O is added to the MXene nanosheet suspension prepared in step S1, and the mixture is stirred and freeze-dried to obtain MXene / Sn 2+ The powder was then vacuum-sealed for later use. S3. Take the MXene / Sn prepared in step S2... 2+ The powder and selenium powder were transferred to a tube furnace and pyrolyzed under argon and hydrogen atmosphere. After the reaction was completed, the layer-by-layer assembled 2D-2D Schottky heterojunction composite material MXene / SnSe2 was obtained.

[0010] Preferably, the acidic etching solution in step S1 is obtained by mixing 12-24 mL of 9-12 mol / L hydrochloric acid, 2-4 mL of hydrofluoric acid, and 6-12 mL of deionized water; And / or in step S1, 0.5-2.5g of Ti3AlC2 raw material is added to the etching solution, etched under water bath conditions, the reaction temperature is 30-50℃, the continuous centrifugation time is 20-50h, and the centrifuged water is washed until the pH is 6-7. And / or the amount of LiCl added to the intercalated ion solution in step S1 is 1-2g, and the volume of deionized water is 40-80mL.

[0011] Preferably, in step S2, the amount of SnCl2·2H2O is 0.05-0.5g, the concentration of MXene nanosheet suspension is 3-7 mg / mL, and the volume of suspension is 20-40 mL.

[0012] Preferably, in step S3, MXene / Sn 2+ The amount of powder added is 30-50mg, the amount of selenium powder added is 150-250mg, the heating temperature is 350-450℃, the reaction time is 1.5-2.5h, and the heating rate and cooling rate are 1-3℃ / min.

[0013] The layer-by-layer assembled 2D-2D Schottky heterojunction composite material or the layer-by-layer assembled 2D-2D Schottky heterojunction composite material prepared by the method described above is applied to electromagnetic wave absorption and conversion.

[0014] (III) Beneficial Effects This invention provides a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, its preparation method, and its application. Compared with the prior art, it has the following advantages: This invention provides a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, which first prepares a single-layer / few-layer Ti3C2T composite material through an acid etching combined with a peeling process. x MXene nanosheets were first prepared, and then p-region metal ions were adsorbed onto the surface of the MXene nanosheets via electrostatic adsorption. Further 2D / 2D Schottky heterojunction composites were then prepared via pyrolytic selenization. The SnSe2 nanosheets obtained through in-situ selenization exhibit semiconductor properties and form a 2D / 2D Schottky heterojunction interface with the highly conductive MXene nanosheets, significantly improving the interfacial polarization response intensity and enhancing interfacial polarization loss. Simultaneously, the abundant grain boundaries within the SnSe2 nanosheets further increase the interfacial electronic interaction region, promoting the attenuation of electromagnetic waves. Anchoring the semiconductor SnSe2 nanosheets and interconnected MXene on the surface of the MXene nanosheets to form a 3D porous conductive network optimizes its impedance matching characteristics, allowing more electromagnetic waves to enter the composite material and be absorbed and converted by the internal multiple loss mechanisms. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The X-ray diffraction patterns of the products prepared in Examples 1-4 and Comparative Example 1 of this invention are shown below. Figure 2 Scanning electron microscope (SEM) images (a, b) of the layer-by-layer assembled 2D-2D Schottky heterojunction composite material MXene / SnSe2 according to an embodiment of the present invention. Figure 3 Transmission electron microscopy (TEM) images (a, b) of the layer-by-layer assembled 2D-2D Schottky heterojunction composite material MXene / SnSe2 according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the preparation process of the layer-by-layer assembly of the 2D-2D Schottky heterojunction composite material MXene / SnSe2 according to an embodiment of the present invention; Figure 5 The diagram shows the electromagnetic wave absorption performance of the MXene material prepared in Comparative Example 1 of this invention. Figure 6 The following are performance diagrams of the 2D-2D Schottky heterojunction composite materials MXene / SnSe2-1(a), MXene / SnSe2-2(b), MXene / SnSe2-3(c), and MXene / SnSe2-4(d) prepared in Examples 1-4 of this invention; Figure 7 This is a performance comparison chart of the products prepared in Examples 1-4 and Comparative Example 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This application provides a simple, structurally controllable, and high-performance layer-by-layer assembled 2D-2D Schottky heterojunction composite material, along with its preparation method and applications, solving the current challenges of Ti3C2T... x MXene materials face technical challenges such as impedance mismatch and low dielectric polarization response intensity, which leads to poor absorption efficiency.

[0019] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0020] In a first aspect, embodiments of the present invention provide a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, wherein the layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, comprising: p-region metal ions are adsorbed onto the surface of MXene nanosheets via electrostatic adsorption, followed by in-situ growth of 2D SnSe2 semiconductor nanosheets on the MXene nanosheet surface through a chemical vapor deposition-selenization process, forming a Schottky heterojunction. The abundant grain boundaries within the SnSe2 nanosheets further increase the interfacial electronic interaction region, promoting the attenuation of electromagnetic waves. Simultaneously, the interconnected MXene nanosheets form a 3D porous conductive network structure, optimizing the impedance matching characteristics of the composite material. Figure 2-3 As shown, SnSe2 nanoplates are uniformly anchored on the surface of MXene nanosheets, forming a unique 2D / 2D layer-by-layer assembly structure.

[0021] Secondly, such as Figure 4 As shown, this embodiment of the invention provides a method for preparing a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, comprising: S1, 2D transition metal carbide Ti3C2T x MAX phase raw materials were added in batches to a mixed etching solution formed by hydrochloric acid, hydrofluoric acid, and deionized water, and etched under water bath conditions. After the reaction was completed, the mixture was centrifuged, washed with water, and then added to a LiCl intercalation ion solution. After intercalation, the mixture was repeatedly washed and centrifuged until the supernatant solution became turbid. Finally, a suspension of a few layers of MXene nanosheets was obtained by long-term centrifugation. S2. SnCl2·2H2O is added to the solution of few-layer MXene nanosheets prepared in step S1. After stirring for a certain period of time, the solution is freeze-dried to obtain MXene / Sn 2+ The powder was then vacuum-sealed for later use. S3. Take the MXene / Sn prepared in step S2... 2+ The powder and selenium powder were transferred to a tube furnace and pyrolyzed under argon and hydrogen atmosphere. After the reaction was completed, the layer-by-layer assembled 2D-2D Schottky heterojunction composite material MXene / SnSe2 was obtained.

[0022] Thirdly, embodiments of the present invention provide an application of layer-by-layer assembled 2D-2D Schottky heterojunction composite materials, wherein the 2D-2D Schottky heterojunction composite material as described in any of the preceding claims or the 2D-2D Schottky heterojunction composite material prepared by any of the preceding claims is applied to electromagnetic wave absorption.

[0023] This invention provides a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, which first prepares a few layers of Ti3C2T through an acid etching combined with a peeling process. xMXene nanosheets were first prepared, and then p-region metal ions were adsorbed onto the surface of the MXene nanosheets via electrostatic adsorption. A 2D / 2D Schottky heterojunction composite material was then prepared via pyrolytic selenization. The SnSe2 nanosheets obtained by in-situ selenization treatment possess semiconductor properties and form a 2D / 2D Schottky heterojunction interface with the highly conductive MXene nanosheets, significantly improving the interfacial polarization response intensity and enhancing interfacial polarization loss of the composite material. Simultaneously, the abundant grain boundaries within the SnSe2 nanosheets further increase the interfacial electronic interaction region, promoting the attenuation capability of electromagnetic waves. Anchoring the semiconductor SnSe2 nanosheets and interconnected MXene on the surface of the MXene nanosheets to form a 3D porous conductive network optimizes its impedance matching characteristics, allowing more electromagnetic waves to enter the composite material and be absorbed and converted by the internal multiple loss mechanisms.

[0024] Example 1: The layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, including: p-region metal ions are adsorbed on the surface of MXene nanosheets by electrostatic adsorption, and then 2D SnSe2 semiconductor nanosheets are grown in situ on the surface of MXene nanosheets by chemical vapor deposition-selenization process to form a Schottky heterojunction composite material.

[0025] A method for preparing layer-by-layer assembled 2D-2D Schottky heterojunction composite materials includes: S1, 18 mL of hydrochloric acid, 3 mL of hydrofluoric acid, and 9 mL of deionized water were added to a polytetrafluoroethylene reactor and stirred for 30 min to form an acidic etching solution. 1.5 g of the two-dimensional layered transition metal carbide MAX phase Ti3AlC2 precursor was added in batches to the strong acid etching solution, and the reaction was carried out at 35 °C for 35 h in a water bath. After centrifugation at 7000 r / min and washing with water, the pH of the supernatant reached 6-7. The resulting precipitate was redispersed in 60 mL of deionized water containing 1.5 g of LiCl and stirred for 8 h. After centrifugation at 7000 r / min and washing with water until the supernatant became turbid, it was centrifuged at 3500 r / min for 45 min to obtain a solution of a few-layer MXene nanosheets.

[0026] S2. Add 0.05 g SnCl2·2H2O to a 5 mg / mL MXene solution, stir for 1 h, and then freeze-dry to obtain MXene / Sn 2+ Powder.

[0027] S3, 40mg MXene / Sn 2+The powder and 200 mg of Se powder were placed in ceramic boats and transferred to the downstream and upstream sides of a tube furnace, respectively. The furnace was heated to 400 °C under an argon-hydrogen atmosphere and held at that temperature for 2 h. The heating and cooling rates were both 2 °C / min. After the reaction temperature cooled to room temperature, the MXene / SnSe2-1 composite material with a 2D-2D Schottky heterojunction was obtained.

[0028] like Figure 6 As shown in (a), the minimum reflection loss of the 2D-2D Schottky heterojunction composite material MXene / SnSe2-1 obtained above reaches -30.44dB, and the effective absorption bandwidth is 2.96GHz.

[0029] Example 2: The layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, including: p-region metal ions are adsorbed on the surface of MXene nanosheets by electrostatic adsorption, and then 2D SnSe2 semiconductor nanosheets are grown in situ on the surface of MXene nanosheets by chemical vapor deposition-selenization process to form a Schottky heterojunction composite material.

[0030] A method for preparing layer-by-layer assembled 2D-2D Schottky heterojunction composite materials includes: S1, 18 mL of hydrochloric acid, 3 mL of hydrofluoric acid, and 9 mL of deionized water were added to a polytetrafluoroethylene reactor and stirred for 30 min to form an acidic etching solution. 1.5 g of the two-dimensional layered transition metal carbide MAX phase Ti3AlC2 precursor was added in batches to the strong acid etching solution, and the reaction was carried out at 35 °C for 35 h in a water bath. After centrifugation at 7000 r / min and washing with water, the pH of the supernatant reached 6-7. The resulting precipitate was redispersed in 60 mL of deionized water containing 1.5 g of LiCl and stirred for 8 h. After centrifugation at 7000 r / min and washing with water until the supernatant became turbid, it was centrifuged at 3500 r / min for 45 min to obtain a solution of a few-layer MXene nanosheets.

[0031] S2. Add 0.1 g SnCl2·2H2O to a 5 mg / mL MXene solution, stir for 1 h, and then freeze-dry to obtain MXene / Sn 2+ Powder.

[0032] S3, 40mg MXene / Sn 2+ The powder and 200 mg of Se powder were placed in ceramic boats and transferred to the downstream and upstream sides of a tube furnace, respectively. The furnace was heated to 400 °C under an argon-hydrogen atmosphere and held at that temperature for 2 h. The heating and cooling rates were both 2 °C / min. After the reaction temperature cooled to room temperature, the MXene / SnSe2-2 composite material with a 2D-2D Schottky heterojunction was obtained.

[0033] like Figure 6 As shown in (b), the minimum reflection loss of the 2D-2D Schottky heterojunction composite material MXene / SnSe2-2 obtained above reaches -58.39dB, and the effective absorption bandwidth is 4.92GHz.

[0034] Example 3: The layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, including: p-region metal ions are adsorbed on the surface of MXene nanosheets by electrostatic adsorption, and then 2D SnSe2 semiconductor nanosheets are grown in situ on the surface of MXene nanosheets by chemical vapor deposition-selenization process to form a Schottky heterojunction composite material.

[0035] A method for preparing layer-by-layer assembled 2D-2D Schottky heterojunction composite materials includes: S1, 18 mL of hydrochloric acid, 3 mL of hydrofluoric acid, and 9 mL of deionized water were added to a polytetrafluoroethylene reactor and stirred for 30 min to form an acidic etching solution. 1.5 g of the two-dimensional layered transition metal carbide MAX phase Ti3AlC2 precursor was added in batches to the strong acid etching solution, and the reaction was carried out at 35 °C for 35 h in a water bath. After centrifugation at 7000 r / min and washing with water, the pH of the supernatant reached 6-7. The resulting precipitate was redispersed in 60 mL of deionized water containing 1.5 g of LiCl and stirred for 8 h. After centrifugation at 7000 r / min and washing with water until the supernatant became turbid, it was centrifuged at 3500 r / min for 45 min to obtain a solution of a few-layer MXene nanosheets.

[0036] S2. Add 0.2 g SnCl2·2H2O to a 5 mg / mL MXene solution, stir for 1 h, and then freeze-dry to obtain MXene / Sn 2+ Powder.

[0037] S3, 40mg MXene / Sn 2+ The powder and 200 mg of Se powder were placed in ceramic boats and transferred to the downstream and upstream sides of a tube furnace, respectively. The furnace was heated to 400 °C under an argon-hydrogen atmosphere and held at that temperature for 2 h. The heating and cooling rates were both 2 °C / min. After the reaction temperature cooled to room temperature, the MXene / SnSe2-3 composite material with a 2D-2D Schottky heterojunction was obtained.

[0038] like Figure 6 As shown in (c), the minimum reflection loss of the 2D-2D Schottky heterojunction composite material MXene / SnSe2-3 obtained above reaches -40.73dB, and the effective absorption bandwidth is 3.88GHz.

[0039] Example 4: The layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, including: p-region metal ions are adsorbed on the surface of MXene nanosheets by electrostatic adsorption, and then 2D SnSe2 semiconductor nanosheets are grown in situ on the surface of MXene nanosheets by chemical vapor deposition-selenization process to form a Schottky heterojunction composite material.

[0040] A method for preparing layer-by-layer assembled 2D-2D Schottky heterojunction composite materials includes: S1, 18 mL of hydrochloric acid, 3 mL of hydrofluoric acid, and 9 mL of deionized water were added to a polytetrafluoroethylene reactor and stirred for 30 min to form an acidic etching solution. 1.5 g of the two-dimensional layered transition metal carbide MAX phase Ti3AlC2 precursor was added in batches to the strong acid etching solution, and the reaction was carried out at 35 °C for 35 h in a water bath. After centrifugation at 7000 r / min and washing with water, the pH of the supernatant reached 6-7. The resulting precipitate was redispersed in 60 mL of deionized water containing 1.5 g of LiCl and stirred for 8 h. After centrifugation at 7000 r / min and washing with water until the supernatant became turbid, it was centrifuged at 3500 r / min for 45 min to obtain a solution of a few-layer MXene nanosheets.

[0041] S2. Add 0.4 g SnCl2·2H2O to a 5 mg / mL MXene solution, stir for 1 h, and then freeze-dry to obtain MXene / Sn 2+ Powder.

[0042] S3, 40mg MXene / Sn 2+ The powder and 200 mg of Se powder were placed in ceramic boats and transferred to the downstream and upstream sides of a tube furnace, respectively. The furnace was heated to 400 °C under an argon-hydrogen atmosphere and held at that temperature for 2 h. The heating and cooling rates were both 2 °C / min. After the reaction temperature cooled to room temperature, the MXene / SnSe2-4 composite material with a 2D-2D Schottky heterojunction was obtained.

[0043] like Figure 6 As shown in (d), the minimum reflection loss of the 2D-2D Schottky heterojunction composite material MXene / SnSe2-4 obtained above reaches -41.06dB, and the effective absorption bandwidth is 3.28GHz.

[0044] In this embodiment of the invention, electromagnetic parameters were obtained using a vector network analyzer. Paraffin wax was uniformly mixed with a prepared 2D-2D Schottky heterojunction composite material MXene / SnSe2 (15wt%). After being melted under vacuum heating, the mixture was pressed into a coaxial ring sample with an outer diameter of 7.0 mm, an inner diameter of 3.04 mm, and a thickness of 2.0 mm using a mold. The electromagnetic parameters of the coaxial ring sample were tested using a vector network analyzer (Ceyear 3656D). The minimum reflection loss (RL) at different thicknesses was fitted according to the transmission line theory formula. (1) (2) Z in Z0 is the effective input impedance, Z0 is the free space impedance, and ε is the effective input impedance. r =ε′- j ε″ and μ r =μ′- j μ″ represents the complex permittivity and complex permeability, respectively; f is the electromagnetic wave frequency; d is the corresponding sample thickness; and c is the speed of light in a vacuum.

[0045] from Figure 6 The minimum reflection loss curves of the 2D-2D Schottky heterojunction composite material MXene / SnSe2 prepared in Examples 1-4 at different thicknesses show that as the number of SnSe2 nanosheets formed in situ on the surface of MXene nanosheets gradually increases, the minimum reflection loss value first increases and then decreases.

[0046] Depend on Figure 6 (a) It can be seen that the minimum reflection loss of the MXene / SnSe2-1 composite material is -30.44dB when the thickness is 2.0mm.

[0047] Depend on Figure 6 (b) It can be seen that increasing the amount of SnSe2 nanosheets on the nanosheet surface results in the construction of a 2D-2D Schottky heterojunction composite material MXene / SnSe2-2 with abundant Schottky hetero interfaces, which improves the dielectric polarization response capability of the material. At a thickness of 1.5 mm, the minimum reflection loss reaches -58.39 dB.

[0048] Depend on Figure 6 (c,d) It can be seen that as the number of SnSe2 nanosheets is further increased, the electromagnetic wave absorption performance of the prepared MXene / SnSe2-3 and MXene / SnSe2-4 composite materials gradually decreases, from -40.73dB to -41.06dB, respectively.

[0049] Comparative Example 1: A method for preparing a layer-by-layer assembled 2D-2D Schottky heterojunction composite material is provided, comprising: S1, 18 mL of hydrochloric acid, 3 mL of hydrofluoric acid, and 9 mL of deionized water were added to a polytetrafluoroethylene reactor and stirred for 30 min to form an acidic etching solution. 1.5 g of the two-dimensional layered transition metal carbide MAX phase Ti3AlC2 precursor was added in batches to the strong acid etching solution, and the reaction was carried out at 35 °C for 35 h in a water bath. After centrifugation at 7000 r / min and washing with water, the pH of the supernatant reached 6-7. The resulting precipitate was redispersed in 60 mL of deionized water containing 1.5 g of LiCl and stirred for 8 h. After centrifugation at 7000 r / min and washing with water until the supernatant became turbid, it was centrifuged at 3500 r / min for 45 min to obtain a solution of a few-layer MXene nanosheets.

[0050] S2. Place 40 mg of MXene powder in a ceramic boat and transfer it to a tube furnace. Heat to 400 °C under an argon-hydrogen atmosphere and hold for 2 h. The heating and cooling rates are both 2 °C / min. After the reaction temperature drops to room temperature, the composite material MXene is obtained.

[0051] like Figure 5 As shown, the minimum reflection loss of the composite material MXene obtained above reaches -10.23dB, and the effective absorption bandwidth is 0.32GHz.

[0052] like Figure 1 , Figure 7 The figures show X-ray diffraction patterns and performance comparison diagrams of the products prepared in Examples 1-4 and Comparative Example 1, respectively. As can be seen from the figures, the electromagnetic microwave absorption performance of the composite materials prepared in Examples 1-4 is superior.

[0053] The excellent electromagnetic microwave absorption performance of the 2D-2D Schottky heterojunction composite material MXene / SnSe2 provided in this invention is mainly attributed to the following aspects: First, a few-layer Ti3C2T was prepared through an acid etching combined with a lift-off process. xMXene nanosheets were first prepared, and then p-region metal ions were adsorbed onto the surface of the MXene nanosheets via electrostatic adsorption. A 2D / 2D Schottky heterojunction composite material was then prepared via pyrolytic selenization. The SnSe2 nanosheets obtained by in-situ selenization treatment possess semiconductor properties and form a 2D / 2D Schottky heterojunction interface with the highly conductive MXene nanosheets, significantly improving the interfacial polarization response intensity and enhancing interfacial polarization loss of the composite material. Simultaneously, the abundant grain boundaries within the SnSe2 nanosheets further increase the interfacial electronic interaction region, promoting the attenuation capability of electromagnetic waves. Anchoring the semiconductor SnSe2 nanosheets and interconnected MXene on the surface of the MXene nanosheets to form a 3D porous conductive network optimizes its impedance matching characteristics, allowing more electromagnetic waves to enter the composite material and be absorbed and converted by the internal multiple loss mechanisms.

[0054] Secondly, in this embodiment of the invention, a 2D-2D Schottky heterojunction composite material MXene / SnSe2 is prepared using an electrostatic adsorption combined with a pyrolysis selenization strategy, exhibiting excellent reflection loss value and effective absorption frequency bandwidth.

[0055] Finally, this invention focuses on a few-layer MXene as the research object, employing a 2D-2D Schottky heterojunction composite material MXene / SnSe2 through electrostatic adsorption combined with a pyrolytic selenization strategy. The equipment used and the preparation process in this study are simple, safe, clean, and environmentally friendly, facilitating large-scale industrial production.

[0056] In summary, compared with existing technologies, it has the following beneficial effects: This invention provides a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, which first prepares a single-layer / few-layer Ti3C2T composite material through an acid etching combined with a peeling process. x MXene nanosheets were first prepared, and then p-region metal ions were adsorbed onto the surface of the MXene nanosheets via electrostatic adsorption. Further 2D / 2D Schottky heterojunction composites were then prepared via pyrolytic selenization. The SnSe2 nanosheets obtained through in-situ selenization exhibit semiconductor properties and form a 2D / 2D Schottky heterojunction interface with the highly conductive MXene nanosheets, significantly improving the interfacial polarization response intensity and enhancing interfacial polarization loss. Simultaneously, the abundant grain boundaries within the SnSe2 nanosheets further increase the interfacial electronic interaction region, promoting the attenuation of electromagnetic waves. Anchoring the semiconductor SnSe2 nanosheets and interconnected MXene on the surface of the MXene nanosheets to form a 3D porous conductive network optimizes its impedance matching characteristics, allowing more electromagnetic waves to enter the composite material and be absorbed and converted by the internal multiple loss mechanisms.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A layer-by-layer assembled 2D-2D Schottky heterojunction composite material, characterized in that, The layer-by-layer assembled 2D-2D Schottky heterojunction composite material is MXene / SnSe2, comprising: p-region metal ions are adsorbed on the surface of MXene nanosheets by electrostatic adsorption, and then 2D SnSe2 semiconductor nanosheets are grown in situ on the interconnected MXene nanosheets by chemical vapor deposition-selenization process to form a Schottky heterojunction composite material.

2. The layer-by-layer assembled 2D-2D Schottky heterojunction composite material as described in claim 1, characterized in that, The SnSe2 nanosheets contain abundant grain boundaries, and the interconnected MXene nanosheets form a 3D porous conductive network structure.

3. The layer-by-layer assembled 2D-2D Schottky heterojunction composite material as described in claim 1, characterized in that, The thickness of the SnSe2 nanosheet is 1 μm.

4. A method for preparing a layer-by-layer assembled 2D-2D Schottky heterojunction composite material, characterized in that, Includes the following steps: S1. The 2D transition metal carbide Ti3AlC2 MAX phase raw material was added in batches to a mixed etching solution formed by hydrochloric acid, hydrofluoric acid and deionized water for etching. After the reaction was completed, the raw material was centrifuged, washed with water and added to a LiCl intercalation ion solution. After intercalation, the raw material was repeatedly washed with water and centrifuged until the upper solution was turbid. Centrifugation was continued until a single-layer / few-layer MXene nanosheet suspension was obtained. S2. SnCl2·6H2O is added to the MXene nanosheet suspension prepared in step S1, and the mixture is stirred and freeze-dried to obtain MXene / Sn 2+ The powder is then vacuum-sealed for later use. S3. Take the MXene / Sn prepared in step S2... 2+ The powder and selenium powder were transferred to a tube furnace and pyrolyzed under argon and hydrogen atmosphere. After the reaction was completed, the layer-by-layer assembled 2D-2D Schottky heterojunction composite material MXene / SnSe2 was obtained.

5. The method for preparing the layer-by-layer assembled 2D-2D Schottky heterojunction composite material as described in claim 4, characterized in that, The acidic etching solution in step S1 is obtained by mixing 12-24 mL of 9-12 mol / L hydrochloric acid, 2-4 mL of hydrofluoric acid, and 6-12 mL of deionized water. And / or in step S1, 0.5-2.5g of Ti3AlC2 raw material is added to the etching solution, etched under water bath conditions, the reaction temperature is 30-50℃, the continuous centrifugation time is 20-50h, and the centrifuged water is washed until the pH is 6-7. And / or the amount of LiCl added to the intercalated ion solution in step S1 is 1-2g, and the volume of deionized water is 40-80mL.

6. The method for preparing the layer-by-layer assembled 2D-2D Schottky heterojunction composite material as described in claim 4, characterized in that, In step S2, the amount of SnCl2·2H2O is 0.05-0.5g, the concentration of MXene nanosheet suspension is 3-7 mg / mL, and the volume of suspension is 20-40 mL.

7. The method for preparing the layer-by-layer assembled 2D-2D Schottky heterojunction composite material as described in claim 4, characterized in that, In step S3, MXene / Sn 2+ The amount of powder added is 30-50mg, the amount of selenium powder added is 150-250mg, the heating temperature is 350-450℃, the reaction time is 1.5-2.5h, and the heating rate and cooling rate are 1-3℃ / min.

8. The layer-by-layer assembled 2D-2D Schottky heterojunction composite material as described in any one of claims 1-3, or the layer-by-layer assembled 2D-2D Schottky heterojunction composite material prepared by the preparation method as described in any one of claims 4-7, is applied to electromagnetic wave absorption and conversion.

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