Two-dimensional hexagonal transition metal boride h-mbenes material and preparation method and application thereof

Abstract

The application relates to the technical field of hexagonal MBenes material preparation, in particular to a two-dimensional hexagonal transition metal boride h-MBenes material, a preparation method and application thereof. The molecular formula of the h-MBenes material is Hf x B y T z (T=H, O, F, Cl or OH), the h-MBenes phase material has a hexagonal crystal structure and is formed by alternately stacking transition metal hafnium layers and graphene-like boron layers, and the h-MBenes phase material is easy to be functionalized. The hexagonal ternary layered transition metal boride h-MAB phase material is used as raw material, the hexagonal ternary layered transition metal boride h-MAB phase material is etched by using a wet chemical method or a molten salt method, and a two-dimensional hexagonal transition metal boride h-MBenes material is obtained, the method is simple and effective, the raw material is easy to obtain and low in price, and the method has important industrial application prospects. The application also discloses possible applications of the h-MAB phase for preparing the h-MBenes material, and the results show that the h-MBenes material has good conductivity and excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of hexagonal MBenes material preparation technology, specifically to two-dimensional hexagonal transition metal boride h-MBenes materials, their preparation methods, and applications. Background Technology

[0002] MXene, as one of the newest members of the two-dimensional material family, is a two-dimensional transition metal carbon and / or nitride obtained by chemically etching away the A layer from a layered ternary transition metal carbon and / or nitride MAX phase. The general formula for the MAX phase is M. n+1 AX n (Where M represents an early transition metal, A is a main group element, and X represents C and / or N). MXenes, due to their unique layered structure, large specific surface area, high conductivity, and abundant functional groups, have potential applications in many fields. However, to date, MXenes have been limited to carbon and / or nitrides due to the constraint of the precursor MAX phase. Recently, theoretical predictions have shown that two-dimensional transition metal borides (MBenes), similar to MXenes, can be used as potential metal-ion batteries (J. Mater. Chem. A 2017, 5, 23530), magnetic devices (Nanoscale 2021, 13, 8254), and catalysts (Nat. Commun. 2021, 12, 4080). However, most applications of MBenes remain at the theoretical prediction stage, and experimental verification still awaits the successful synthesis of MBenes.

[0003] Currently, over 30 MXenes have been experimentally synthesized and have wide applications in various fields (Science 2021, 372, 1165). Compared to MXenes, the applications of MBEnes are rarely reported experimentally, mainly because the experimental synthesis of MBEnes is limited by their parent phase, the ternary orthorhombic MAB (ort-MAB). Selectively etching away the Al layer from the ort-MAB is extremely difficult. To date, only two ort-MAB phases, MoAlB and Cr2AlB2, have been used as precursors to exfoliate MoB and CrBMBenes materials. Furthermore, the partial etching of the Al atomic layer or the complete dissolution of the parent phase in the ort-MAB results in poor quality MBEnes obtained by etching the ort-MAB (Adv. Mater. 2022, 34, 2108840). Therefore, there are two main reasons that currently affect the expansion of MBENS materials. First, there are too few types of orthogonal ort-MAB phase precursors that can exist stably. Second, there are problems such as partial oxidation, precursor dissolution and recrystallization during the etching process of ort-MAB phase, which makes it difficult for ort-MAB phase to be selectively etched.

[0004] To find a more suitable ternary MAB phase precursor for exfoliation, our team reported the first ternary hexagonal MAB phase (h-MAB) Ti₂InB₂ and prepared layered boride TiB using a high-temperature dealloying method. However, TiB underwent a severe phase transformation under high-temperature conditions (Nat. Comm., 2019, 10, 2284). Recently, inspired by the work on h-MAB phase Ti₂InB₂, Rosen et al. successfully synthesized two in-plane ordered hexagonal quaternary transition metal borides (i-MAB), Mo… 2 / 3 Y 1 / 3 )2AlB2 and (Mo 2 / 3Sc 1 / 3 By selectively stripping Al and Y layers or Al and Sc layers from 2AlB2, novel two-dimensional borides (i-MBenes) are obtained. However, i-MBenes have a large number of defects on their surface, which reduces their conductivity and limits their application to some extent.

[0005] Whether an ideal two-dimensional hexagonal transition metal boride (h-MBenes) can be obtained, and what properties h-MBenes materials should possess, have been difficult problems for researchers. Therefore, developing an h-MBenes material and providing a method for preparing h-MBenes materials are of great significance for exploring new properties and expanding the applications of MBENS materials. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides two-dimensional hexagonal transition metal boride (h-MBenes) materials, their preparation methods, and applications. Using hexagonal ternary layered transition metal boride (h-MAB) phase materials as raw materials, this invention prepares two-dimensional hexagonal transition metal boride (h-MBenes) materials through wet chemical etching or molten salt etching. The two-dimensional hexagonal transition metal boride (h-MBenes) materials are formed by alternating stacking of transition metal hafnium layers and graphene-like boron layers. Furthermore, the h-MBenes phase materials are easily functionalized. Their unique crystal structure and composition endow (h-MBenes) materials with novel physical properties, such as topological electronic states and superconducting characteristics. They have promising applications in lithium-ion battery anode materials, magnetic materials, HER catalysts, or nitrogen-catalyzed ammonia synthesis catalysts.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A method for preparing two-dimensional hexagonal transition metal boride h-MBenes material: using hexagonal ternary layered transition metal boride h-MAB phase material as raw material, the hexagonal ternary layered transition metal boride h-MAB phase material is etched by wet chemical method or molten salt method to obtain two-dimensional hexagonal transition metal boride h-MBenes material.

[0009] Wet chemical etching includes the following steps:

[0010] Hexagonal ternary layered transition metal boride h-MAB phase material was mixed with acid and reacted at 30-60℃ for 3.5-48h under stirring. After washing and drying, two-dimensional hexagonal transition metal boride h-MBenes material was obtained.

[0011] Etching using the molten salt method includes the following steps:

[0012] Hexagonal ternary layered transition metal boride (h-MAB) phase material, transition metal salt, and inorganic salt are ground and mixed to obtain a powder mixture. The powder mixture is then etched in an inert atmosphere at 300-800℃ for 1-48 hours to obtain a reaction product. The intermediate products of the etching reaction are removed from the reaction product, and the product is then cleaned and dried to obtain a two-dimensional hexagonal transition metal boride (h-MBenes) material.

[0013] Preferably, the hexagonal ternary layered transition metal boride h-MAB phase material is selected from Hf2InB2, and the hexagonal ternary layered transition metal boride h-MAB phase material is a powder with a diameter of 5-50 μm.

[0014] Preferably, the acid is selected from a mixture of hydrochloric acid and LiF or hydrofluoric acid, wherein the mass fraction of hydrofluoric acid is 5-50%, the mass fraction of hydrochloric acid is 1-37%, and the molar ratio of hydrochloric acid to LiF is 1:1; hydrochloric acid reacts with LiF to produce HF.

[0015] Preferably, the molar ratio of the hexagonal ternary layered transition metal boride (h-MAB) phase material to the acid is 1:2-10.

[0016] Preferably, the transition metal salt is selected from CuCl2, and the inorganic salt is selected from one or two of NaCl and KCl.

[0017] Preferably, the molar ratio of the hexagonal ternary layered transition metal boride h-MAB phase material, the transition metal salt, and the inorganic salt is 1:1-6:1-5.

[0018] Preferably, the intermediate product of the etching reaction is Cu, and the removal method is a displacement reaction. The conditions for the displacement reaction are: placing the reaction product in a dilute hydrochloric acid solution and stirring at room temperature until the red copper precipitate completely disappears and the solution turns copper-green.

[0019] This invention also protects the two-dimensional hexagonal transition metal boride h-MBenes material prepared by the above preparation method, wherein the molecular formula of the h-MBenes material is Hf x B y T z Where x = 1-4, y = 1-4, z = 1-4, and T in the molecular formula is any one or more of O, F, Cl, H, and OH.

[0020] Preferably, the h-MBenes material is prepared by extracting the A-site element from the h-MAB phase, and the h-MBenes material has an accordion structure, formed by alternating stacking of transition metal hafnium layers and graphene-like boron layers.

[0021] This invention also protects the application of two-dimensional hexagonal transition metal boride h-MBenes materials in the preparation of lithium-ion battery anode materials, magnetic materials, HER catalysts, and nitrogen-catalyzed ammonia synthesis catalysts.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The present invention provides a method for exfoliating h-MAB phase material into two-dimensional boride material. The method has a short reaction time, low reaction temperature, and saves costs. Moreover, the exfoliation method of h-MAB phase material provided by the present invention is simple, highly compatible with h-MAB phase material, and the exfoliation is more complete. It also has strong scalability.

[0024] (2) The two-dimensional hexagonal transition metal borides h-MBenes material provided by the present invention has more complete exfoliation and larger interlayer spacing than existing boride materials (CrB, MoB, TiB).

[0025] (3) The two-dimensional hexagonal transition metal boride h-MBenes material provided by the present invention has a graphene-like boron layer, and is formed by alternating stacking of transition metal hafnium layer and graphene-like boron layer. The special crystal structure gives the two-dimensional hexagonal transition metal boride h-MBenes material novel physical properties, such as topological electronic states and superconducting properties, which can be well applied in lithium-ion battery anode materials, magnetic materials, HER catalysts or nitrogen-catalyzed ammonia synthesis catalysts. In addition, the two-dimensional hexagonal transition metal boride h-MBenes material is easy to functionalize, and the diverse composition makes it have rich properties and wider applications.

[0026] (4) The principle of wet chemical etching in this invention is as follows: the chemical bonds of MA and MB in the ternary layered compound h-MAB phase exhibit obvious anisotropy, that is, the chemical bonds of MA are significantly weaker than those of MB. In a liquid environment, hydrofluoric acid selectively breaks the chemical bonds of MA and reacts with the A-site atoms in the h-MAB precursor to generate water-soluble fluorides, thereby causing the A-site atoms to detach from the h-MAB phase while retaining the MB layer.

[0027] The principle of the molten salt etching method used in this invention is as follows: the MA and MB chemical bonds in the h-MAB phase exhibit obvious anisotropy. At high temperature, the metal ions in the Lewis acid molten salt selectively undergo a substitution reaction with the A-site atoms in the h-MAB precursor, converting the A-site atoms into cations and generating volatile chlorides, thereby detaching them from the h-MAB phase precursor. The MB layer is retained with its original topological structure, while the cations in the Lewis acid are reduced to elemental metals. Attached Figure Description

[0028] Figure 1 In Example 1 of this invention, the h-MBenes material HfBT was obtained by wet chemical method and HF exfoliation of the h-MAB phase material Hf2InB2. x XRD patterns;

[0029] Figure 2 In Example 1 of this invention, the h-MBenes material HfBT was obtained by wet chemical method and HF exfoliation of the h-MAB phase material Hf2InB2. x SEM images;

[0030] Figure 3 In Example 2 of this invention, the h-MBenes material HfBT was obtained by wet chemical method, HCl and LiF exfoliation of the h-MAB phase material Hf2InB2. x XRD patterns;

[0031] Figure 4 In Example 2 of this invention, the h-MBenes material HfBT was obtained by wet chemical method, HCl and LiF exfoliation of the h-MAB phase material Hf2InB2. x SEM images;

[0032] Figure 5 The XRD pattern of h-MBenes material HfBO obtained by molten salt method and Lewis acid salt CuCl2 exfoliation of h-MAB phase material Hf2InB2 in Example 3 of this invention;

[0033] Figure 6The images show the SEM and STEM images of h-MBenes material HfBO obtained by the molten salt method and Lewis acid salt CuCl2 exfoliation of h-MAB phase material Hf2InB2 in Example 3 of the present invention; wherein, (a) is a scanning electron microscope (SEM) image of h-MBenes HfBO material, and (b) and (c) are both top view (STEM) images of h-MBenes HfBO material.

[0034] Figure 7 The figures show the theoretical predictions and experimental test results of the electrical properties of the h-MBenes material HfBO and the precursor Hf2InB2 obtained by the molten salt method and Lewis acid salt CuCl2 exfoliation of the h-MAB phase material Hf2InB2 in Example 3 of this invention. Among them, (a) is the theoretically predicted electronic structure band diagram of Hf2InB2; (b) is the theoretically predicted electronic structure band diagram of HfBO; (c) is the experimentally tested resistivity of Hf2InB2; and (d) is the experimentally tested resistivity of HfBO.

[0035] Figure 8 The above are characterization figures of the electrochemical performance of the h-MBenes material HfBO obtained by the molten salt method and Lewis acid salt CuCl2 exfoliation of the h-MAB phase material Hf2InB2 in Example 3 of this invention as a negative electrode material for lithium-ion batteries; wherein, (a) is at a rate of 0.5 mV s -1 (a) is the CV curve; (b) is the current density at 0.1Ag. -1 (c) is the long cycle curve of the electrode material at different current densities; (d) is the rate performance test graph of the negative electrode material in the current density range of 0.05-1A / g.

[0036] Figure 9 The images show the XRD and SEM images of the h-MBenes material HfBO obtained by the molten salt method and Lewis acid salt CuCl2 exfoliation of the h-MAB phase material Hf2InB2 in Example 3 of this invention before and after long cycling. Among them, (a) is the XRD image at 0, 100 and 600 cycles; (b) is the side view of the electrode material at 0 cycles; (c) is the side view of the electrode material after 600 cycles; and (d) is the top view of the electrode material after 600 cycles. Detailed Implementation

[0037] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0038] Unless otherwise specified, the experimental and testing methods described below are conventional methods; unless otherwise specified, the reagents and raw materials described below are commercially available.

[0039] Example 1

[0040] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0041] In this embodiment, the h-MAB phase material Hf2InB2 was etched using a wet chemical method with HF acid to obtain the h-MBenes material HfBT. x The specific preparation method of this material is as follows:

[0042] (1) Slowly introduce 1g of Hf2InB2 powder into a polytetrafluoroethylene bottle containing 20mL of 40wt% HF acid solution, stir magnetically for 10min at room temperature, and then place it in an oil bath and react at 35℃ for 3.5h. After the reaction is completed, take out the reaction product.

[0043] (2) Washing the reaction product with deionized water and alcohol: Transfer the reaction product to a 50 mL centrifuge tube, rotate at 8000 r / min for 5 min, discard the supernatant, and wash the reaction product repeatedly 5 times (the first 4 times with deionized water and the 5th time with alcohol) until the pH of the supernatant is 6, then discard the supernatant; then place it in a 60℃ oven for 6 h and remove it. The obtained solid product is h-MBenes HfBT. x Material.

[0044] Example 2

[0045] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0046] In this embodiment, the h-MAB phase Hf2InB2 material was co-etched using a wet chemical method with HCl and LiF to obtain the h-MBenes material HfBT. x The specific preparation method of this material is as follows:

[0047] (1) Weigh 1g of the prepared pure phase Hf2InB2 powder, add 10mL of 9mol / L hydrochloric acid and 1g of LiF for etching, and etch at 35℃ for 3.5h. After the reaction is completed, take out the reaction product.

[0048] (2) Washing the reaction product with deionized water and alcohol: Transfer the reaction product to a 50 mL centrifuge tube, rotate at 6000 r / min for 5 min, discard the supernatant, and wash the reaction product repeatedly 5 times (the first 4 times with deionized water and the 5th time with alcohol) until the pH of the supernatant is 5, then discard the supernatant; then place it in a 60℃ oven for 6 h and remove it. The obtained solid product is h-MBenes HfBT. x Material.

[0049] Example 3

[0050] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0051] In this embodiment, the h-MAB phase Hf2InB2 material was etched with molten salt CuCl2 to obtain the MBenes material HfBO. The specific preparation method of this material is as follows:

[0052] (1) Hf2InB2 phase of h-MAB, inorganic salt CuCl2, NaCl and KCl are mixed and ground in a molar ratio of 1:3:1:1 for 40 min to obtain a powder mixture. The powder mixture is reacted in an inert atmosphere at 700℃ for 24 h to obtain the reaction product.

[0053] (2) Transfer the reaction product to a beaker, wash away the displaced etching reaction intermediate metallic copper with dilute hydrochloric acid, stir at room temperature for 30 minutes until the red copper precipitate at the bottom of the beaker completely disappears and the solution turns copper green, stop stirring and remove the precipitate.

[0054] (3) The precipitate was placed in deionized water and centrifuged to separate the solution into layers. The supernatant was discarded and the precipitate was dried to obtain the h-MBenes etching product.

[0055] Example 4

[0056] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0057] (1) Slowly introduce 1g of Hf2InB2 powder into a polytetrafluoroethylene bottle containing 20mL of 5% HF solution, stir magnetically for 10min at room temperature, and then place it in an oil bath and react at 30℃ for 48h. After the reaction is completed, take out the reaction product.

[0058] (2) Washing the reaction product with deionized water and alcohol: Transfer the reaction product to a 50 mL centrifuge tube, rotate at 3500 r / min for 5 min, discard the supernatant, and wash the reaction product repeatedly 5 times (the first 4 times with deionized water and the 5th time with alcohol) until the pH of the supernatant is 6, then discard the supernatant; then place it in a 60℃ oven for 6 h and remove it. The obtained solid product is h-MBenes HfBT. x Material.

[0059] Example 5

[0060] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0061] (1) Slowly introduce 1g of Hf2InB2 powder into a polytetrafluoroethylene bottle containing 5mL of 50% HF solution, stir magnetically for 10min at room temperature, and then place it in an oil bath and react at 30℃ for 3.5h. After the reaction is completed, take out the reaction product.

[0062] (2) Washing the reaction product with deionized water and alcohol: Transfer the reaction product to a 50 mL centrifuge tube, rotate at 4000 r / min for 5 min, discard the supernatant, and wash the reaction product repeatedly 5 times (the first 4 times with deionized water and the 5th time with alcohol) until the pH of the supernatant is 6, then discard the supernatant; then place it in a 60℃ oven for 6 h and remove it. The obtained solid product is h-MBenes HfBT. x Material.

[0063] Example 6

[0064] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0065] (1) Hf2InB2 phase of h-MAB, inorganic salt CuCl2 and KCl are mixed and ground in a molar ratio of 1:1:1 for 40 min to obtain a powder mixture. The powder mixture is reacted in an inert atmosphere at 300℃ for 48 h to obtain the reaction product.

[0066] (2) Transfer the reaction product to a beaker, wash away the displaced etching reaction intermediate metallic copper with dilute hydrochloric acid, stir at room temperature for 30 minutes until the red copper precipitate at the bottom of the beaker completely disappears and the solution turns copper green, stop stirring and remove the precipitate.

[0067] (3) The precipitate was placed in deionized water and centrifuged to separate the solution into layers. The supernatant was discarded and the precipitate was dried to obtain the h-MBenes etching product.

[0068] Example 7

[0069] The preparation method of two-dimensional hexagonal transition metal boride h-MBenes materials includes the following steps:

[0070] (1) Hf2InB2 phase of h-MAB, inorganic salt CuCl2 and NaCl are mixed and ground for 40 min in a molar ratio of 1:6:5 to obtain a powder mixture. The powder mixture is reacted at 800℃ for 1 h in an inert atmosphere to obtain the reaction product.

[0071] (2) Transfer the reaction product to a beaker, wash away the displaced etching reaction intermediate metallic copper with dilute hydrochloric acid, stir at room temperature for 30 minutes until the red copper precipitate at the bottom of the beaker completely disappears and the solution turns copper green, stop stirring and remove the precipitate.

[0072] (3) The precipitate was placed in deionized water and centrifuged to separate the solution into layers. The supernatant was discarded and the precipitate was dried to obtain the h-MBenes etching product.

[0073] Examples 1-7 of this invention all yielded two-dimensional hexagonal transition metal borides h-MBenes materials with novel physical properties, and the effects were parallel. The following study uses the two-dimensional hexagonal transition metal borides h-MBenes materials obtained in Examples 1-3 of this invention as examples, and the specific research methods and results are shown below:

[0074] Figure 1 HfBT obtained by peeling after reaction in Example 1 x The X-ray diffraction (XRD) pattern of the material shows that, compared to the parent phase Hf₂InB₂, the main phase disappears and a new HfBT phase is generated. x The diffraction peaks of the phase indicate that Hf2InB2 was successfully etched.

[0075] Figure 2 The image shown is a scanning electron microscope (SEM) image of the HfBTx material obtained after the reaction in Example 1. It shows a typical accordion shape, indicating that the In layer was selectively etched away.

[0076] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the HfBTx material obtained after the reaction in Example 2. Compared with the parent phase Hf2InB2, the main phase disappears and new HfBTx phase diffraction peaks are generated, indicating that Hf2InB2 was successfully etched.

[0077] Figure 4 HfBT obtained by peeling after reaction in Example 2 x The scanning electron microscope (SEM) image of the material shows a distinct accordion shape, indicating that the In layer was selectively etched away.

[0078] Figure 5 The image shows the X-ray diffraction (XRD) pattern of the HfBO material obtained after etching following the reaction in Example 3. In the figure, "observed" represents the raw experimental data, "calculated" represents the theoretical simulation data, and "difference" represents the difference between the two. The results show that the main phase disappears compared to the parent phase Hf₂InB₂, and new HfBO phase diffraction peaks are generated, indicating successful etching of Hf₂InB₂.

[0079] Figure 6 (a) is a scanning electron microscope (SEM) image of the HfBO material obtained by etching after the reaction in Example 3. It has a distinct accordion shape, indicating that the In layer was selectively etched away. Figure 6 (b) is a top view of the HfBO obtained by stripping. The top view shows that the atoms are hexagonally close-packed, indicating that the etching product retains the hexagonal crystal structure of the parent phase. Figure 6 (c) is a side view (STEM) of the HfBO obtained after stripping. The side view shows the interlayer spacing. This indicates that the In layer was successfully stripped.

[0080] Figure 7 Electrical performance tests were conducted on Hf2InB2 and HfBO obtained by etching. Figure 7 Theoretical calculations in (a) and (b) show that both the Hf2InB2 precursor and the etched product exhibit good metallic conductivity. Due to the effect of oxygen-containing functional groups, only two bands pass through the Fermi level of the etched product HfBO, therefore the conductivity of h-MBenes is lower than that of the precursor. Figure 7 Experimental resistivity tests in (c) and (d) verified the theoretical predictions: the resistivity of Hf₂InB₂ was 0.0129 Ωm, while the resistivity of HfBO₂ was 6.1 × 10⁻⁶. -6 Ωm; the corresponding conductivity of Hf2InB2 is 78.13 S m. -1 The conductivity of HfBO is 1.6 × 10⁻⁶. 5 S m -1 .

[0081] The following study takes the preparation of h-MBenes material as an example to investigate battery performance. The sample is HfBO powder obtained by molten salt etching. The battery is prepared according to the following steps.

[0082] S1. Weigh HfBO powder, carbon black and PVDF in a mass ratio of 8:1:1, grind them into a uniform slurry, coat the slurry onto copper foil, dry it in a vacuum drying oven at 60°C for 8 hours, and then slice it to obtain the negative electrode working electrode sheet.

[0083] S2. When assembling the half-cell, the CR2032 battery case is selected, the finished lithium sheet is used as the counter electrode, the Celgard2302 microporous membrane is used as the separator, and the electrolyte is a mixed solution of ethylene carbonate (EC) and diethylene carbonate (DEC) containing 1.0 mol / L LiPF6, wherein the volume ratio of EC to DEC is 1:1.

[0084] Cyclic voltammetry (CV) test: The cutoff potential is in the range of 0.01-3V. One or more repeated scans are performed at a rate of 0.5mV / s. The cutoff potential is in the range of 0.01-3V so that different reduction and oxidation reactions can occur alternately on the electrode. The current-potential curve is recorded.

[0085] A constant current charge-discharge cycle test is performed, and the voltage change curve over time is recorded. Based on this, the specific capacity can be calculated, and the cycle and rate performance of the battery can be evaluated.

[0086] Figure 8 The image shows the performance of the h-MBenes HfBO lithium-ion anode battery material. Figure 8 As can be seen in (a), only in the first cycle, at 0.7V (vs Li / Li) + A broad reduction peak was observed at the initial potential, but this peak disappeared in subsequent scans. This indicates that electrolyte decomposition occurred and a solid electrolyte interphase (SEI) film was formed. The CV curves showed similar profiles in subsequent cycles, indicating that the h-MBenes electrode material has excellent cycle stability. Figure 8(b) shows that the capacity of the h-MBenes electrode material first gradually increases with increasing cycle number, and then tends to stabilize. Furthermore, it can be seen that the coulombic efficiency of the electrode material is relatively low (76-86%) in the first five cycles, but after the first five cycles, the coulombic efficiency significantly increases to 100% and remains stable. Figure 8(c) shows that the charge-discharge curves at constant current under different current densities show that the capacity of the electrode material gradually decreases with increasing current density. Figure 8(d) shows that as the rate capability of the electrode material first increases and then decreases, its capacity also exhibits a reversible change. HfBO, as an electrode material, has high capacity, and the battery capacity first increases and then stabilizes during long cycles, demonstrating good cycle stability and making it a potential electrode material.

[0087] Figure 9 XRD and SEM images of the HfBO electrode material before and after cycling are shown. Figure 9 (a) It can be seen that the material retains its original crystal structure after long cycling; Figure 9 (b) and Figure 9 (c) The thickness did not increase significantly, which further demonstrates that the material has good cycle stability; Figure 9 (d) The results show that the size of the electrode material decreased after long cycling.

[0088] In summary, compared with existing CrB, MoB, and TiB MBenes materials, the novel hexagonal MBenes material obtained by exfoliating the h-MAB phase material prepared in this embodiment of the invention has good electrical conductivity and good electrochemical performance. The preparation method is universal and the raw materials are widely available. It has potential application prospects in the fields of electrocatalysis, thermocatalysis, flexible electronic devices, and spintronics device candidate materials.

[0089] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. Two-dimensional hexagonal transition metal borides h Process for the production of MBenes materials, characterized in that, Hexagonal ternary layered transition metal borides h -MAB phase material is used as raw material, hexagonal ternary layered transition metal borides h -MAB phase material is etched by wet chemical method or molten salt method to obtain two-dimensional hexagonal transition metal borides h -MBenes material, the two-dimensional hexagonal transition metal borides h -MBenes material is an accordion shape; The wet chemical etching includes the following steps: Hexagonal ternary layered transition metal borides h -MAB phase material and acid are mixed, and after reaction at 30-60℃ for 3.5-48h under stirring condition, the two-dimensional hexagonal transition metal boride is obtained through washing and drying h -MBenes material; the acid is selected from a mixture of hydrochloric acid and LiF or hydrofluoric acid, the mass fraction of the hydrofluoric acid is 5-50%, the mass fraction of the hydrochloric acid is 1-37%, and the molar ratio of the hydrochloric acid and LiF is 1:1; wherein the hydrofluoric acid is used for reacting with the hexagonal ternary layered transition metal boride h The A-site atoms of the MAB phase material react The molten salt etching includes the following steps: Hexagonal ternary layered transition metal borides h The MAB phase material, the secondary metal salt and the inorganic salt are ground and mixed to obtain a powder mixture, and the powder mixture is etched and reacted at 300-800 ℃ for 1-48 h in an inert atmosphere to obtain a reaction product. The intermediate product of the etching reaction is removed from the reaction product, and then the reaction product is washed and dried to obtain a two-dimensional hexagonal transition metal boride h MBenes material; The hexagonal ternary layered transition metal boride h the MAB phase material is selected from Hf2InB2.

2. The two-dimensional hexagonal transition metal boride of claim 1 h Process for the production of MBenes materials, characterized in that, Hexagonal ternary layered transition metal borides h The -MAB phase material is a powder with a diameter of 5-50 µm.

3. The two-dimensional hexagonal transition metal boride of claim 1 h Process for the production of MBenes materials, characterized in that, Hexagonal ternary layered transition metal borides h The molar ratio of the -MAB phase material to the acid is 1:2-10.

4. The two-dimensional hexagonal transition metal boride of claim 1 h Process for the production of MBenes materials, characterized in that, The salt of the transition metal is selected from CuCl2, and the inorganic salt is selected from one or both of NaCl and KCl.

5. The two-dimensional hexagonal transition metal boride of claim 1 h Process for the production of MBenes materials, characterized in that, The molar ratio of the hexagonal ternary layered transition metal boride h-MAB phase material, the salt of the transition metal, and the inorganic salt is 1:1-6:1-5.

6. The two-dimensional hexagonal transition metal boride of claim 1 h Process for the production of MBenes materials, characterized in that, The intermediate product of the etching reaction is Cu, and the removal method is a displacement reaction, and the displacement reaction condition is that the reaction product is placed in a hydrochloric acid solution, stirred at room temperature until the red copper precipitate completely disappears, and the solution becomes green.

7. A two-dimensional hexagonal transition metal boride produced by the production method according to any one of claims 1 to 6. h - MBenes material, characterized in that, The h The molecular formula of the MBenes material is Hf x B y T z wherein x = 1-4, y = 1-4, z = 1-4, and T in the molecular formula is any one or several of O, F, Cl, H, OH.

8. The two-dimensional hexagonal transition metal boride of claim 7 h - MBenes material characterized in that, The h - MBenes materials are made by extracting h - A-site elements from the AAB structure, and h - MBenes materials are accordion structures formed by alternating stacks of transition metal hafnium layers and graphene-like boron layers.

9. A two-dimensional hexagonal transition metal boride of claim 7 h Use of MBenes materials in the preparation of lithium-ion battery anode materials, magnetic materials, HER catalysts, catalysts for the catalytic synthesis of ammonia from nitrogen.

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