Method for determining the fraction of functional group on the surface of mxene using the hall effect

Abstract

The present disclosure relates to a method for determining the fraction of surface functional groups of a two-dimensional MXene material through a Hall effect measurement method. Specifically, the method relates to a method for determining the fraction of surface functional groups of a two-dimensional MXene material, comprising the step of determining the distribution of surface functional groups of the MXene from the measured value of the Hall scattering coefficient of the MXene, determining that the surface functional groups are two or more selected from oxygen groups (-O), hydroxyl groups (-OH), and fluorine groups (-F), and determining the fraction of said two or more surface functional groups.

Description

Technology Field

[0001] The present disclosure relates to a method for determining the fraction of surface functional groups of a two-dimensional MXene material through a Hall effect measurement method.

[0002] [Explanation of government-supported R&D]

[0003] This research was conducted under the supervision of the National Research Foundation of Korea and supported by the Ministry of Science and ICT's Next Generation Intelligent Semiconductor Technology Development Project (Development of a Machine Learning-Based Multi-Scale Simulation Platform for ReRAM Crossbar Array (CBA) Circuit Design and Optimization for Artificial Intelligence Semiconductors, Project No.: 2710015457). Background Technology

[0004] Two-dimensional materials generally consist of ultrathin film structures made up of several layers of atoms, possessing electrical, mechanical, and thermal properties different from those of three-dimensional bulk materials composed of the same elements. A representative example of a two-dimensional material is graphene, which is composed solely of pure carbon; due to its high electrical conductivity, strength, and flexibility, it is expected to be applicable in various fields. However, graphene has a limitation in that, since it is composed solely of carbon, it can only exhibit a single property once its structure is determined. Recently, it has become a subject of extensive research and development following the discovery that MXene, composed of several atomic layers, can be isolated by dissolving the bulk phase of MAX ceramics—a type of transition metal compound—with strong acids such as hydrofluoric acid or hydrochloric acid. In the MAX phase, M represents a transition metal, A represents a metal such as aluminum, and X represents an element such as carbon, nitrogen, or oxygen; since the types and composition of the transition metal and X phases can be varied, there are thousands of different types of MXene that can be isolated from them. Since the elements constituting MXene each form unique chemical bonds, varying the thickness of the MXene phase and the combination of elements can produce different electrical properties, such as insulators, semiconductors, and conductors. Therefore, if a method to control the desired composition and thickness is developed, it can be utilized as a two-dimensional material to replace existing bulk materials.

[0005] The surface of MXene is primarily composed of transition metals, but because they are chemically unstable, various types of functional groups are formed on the surface during manufacturing to stabilize the MXene. These surface functional groups are formed by etching methods using strong acids or by gas-phase synthesis. To date, most MXene synthesis research, particularly studies involving dissolution in strong acids, has focused on synthesizing desired MXene phases, while there has been little research on the types and characteristics of surface functional groups. In the case of MXene produced using hydrofluoric acid, functional groups such as -O, -OH, and -F are typically formed on the surface. Since electronegativity and chemical bonding vary depending on the type of surface functional group, the properties of the manufactured MXene differ completely depending on which functional group is formed. To maximize the physical properties of the required material—for example, to maximize electromagnetic shielding capabilities, increase sensor sensitivity, or utilize it as an electronic device with specific characteristics—it is necessary to control the types of surface functional groups during the manufacturing of two-dimensional MXene, along with synthesizing MXene with a specific composition and structure. Furthermore, to achieve this, it is necessary to know what functional groups exist on the surface of the MXene and in what quantities—that is, the fraction of surface functional groups—in order to modify the process and determine the fraction. Prior art literature

[0006] Korean Patent Publication No. 10-2373455 The problem to be solved

[0007] The present disclosure aims to provide a method for efficiently controlling the MXene manufacturing process by determining the type and fraction of MXene surface functional groups through simple Hall effect measurements, thereby controlling the physical properties of the MXene, and simultaneously selectively synthesizing MXene formed with a desired type and fraction of surface functional groups. means of solving the problem

[0008] To achieve the above objective, one embodiment of the present invention comprises the step of preparing a MAX bulk phase of MAX composition;

[0009] A step of forming MXene by removing layer A from the MAX bulk phase of the above MAX composition;

[0010] A step of measuring the Hall scattering coefficient by measuring the above MXene; and

[0011] The method includes the step of determining the surface functional group distribution of the MXene from the measured value of the Hall scattering coefficient of the MXene.

[0012] The above M is at least one transition metal selected from elements of Group 3, Group 4, Group 5, and Group 6 of the periodic table, the above A layer is at least one selected from elements of Group 12, Group 13, Group 14, Group 15, and Group 16 of the periodic table, and the above X is carbon (C), nitrogen (N), or a combination thereof.

[0013] The step of determining the surface functional group distribution above is,

[0014] A method for classifying surface functional groups of MXene is provided, wherein the surface functional groups are determined to be two or more selected from oxygen groups (-O), hydroxyl groups (-OH), and fluorine groups (-F), and the fraction of said two or more surface functional groups is determined. Effects of the invention

[0015] According to the method of the present disclosure, the type and fraction of MXene surface functional groups are determined through simple Hall effect measurements, thereby controlling the physical properties of the MXene and selectively synthesizing MXene with the desired type and fraction of surface functional groups, which allows for efficient control of the MXene manufacturing process. Brief explanation of the drawing

[0016] Figure 1 schematically illustrates a method for measuring the Hall effect of MXene according to one embodiment of the present invention. Figure 2 shows the change in the Hall factor according to changes in temperature and electron density when fluorine groups (-F) among the surface functional groups of MXene are formed at 100%. Figure 3 shows the change in the Hall factor according to changes in temperature and electron density when the oxygen group (-O) among the surface functional groups of MXene is formed at 100%. Figure 4 shows the change in the Hall factor according to changes in temperature and electron density when hydroxyl groups (-OH) among the surface functional groups of MXene are formed at 100%. Figure 5 shows the formation energy of surface functional groups that may exist on the surface of Sc2C MXene according to one embodiment of the present invention. FIGS. 6a to 6d show the change in the Hall coefficient according to the fraction of two functional groups (F:OH) when fluorine groups and hydroxyl groups are present on the surface of Sc2C MXene according to one embodiment of the present invention. FIGS. 7a to 7d show the change in the Hall coefficient according to the fraction of two functional groups (F:OH) at room temperature when fluorine and hydroxyl groups are present on the surface of Sc2C MXene according to one embodiment of the present invention. FIG. 8 schematically illustrates a method for optimizing a MXene process using a method for determining the type and fraction of MXene surface functional groups according to an embodiment of the present invention. Specific details for implementing the invention

[0017] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention.

[0018] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0019] In this specification, terms such as “comprising” or “having” mean that the described features, numbers, steps, actions, components, parts, or combinations thereof exist unless specifically stated otherwise, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0020] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0021] In addition, although embodiments of the present invention have been described with reference to the accompanying drawings, this is for illustrative purposes only and does not limit the technical concept, configuration, and application of the present invention.

[0022] Hereinafter, the present invention will be described in detail through preferred embodiments of the present invention based on the attached drawings.

[0023] In one aspect, the present invention may relate to a method for classifying surface functional groups of MXene.

[0024] In one embodiment, the method may include: a step of preparing a MAX bulk phase of MAX composition; a step of removing layer A from the MAX bulk phase of MAX composition to form a MXene; a step of measuring the MXene by Hall measurement to measure the Hall scattering coefficient; and a step of determining the surface functional group distribution of the MXene from the measured value of the Hall scattering coefficient of the MXene.

[0025] According to one embodiment of the present invention, the type and fraction of functional groups present on the surface of MXene can be determined by measuring the Hall scattering factor, which changes dramatically depending on the type and distribution of surface functional groups of MXene.

[0026] This Hall scattering coefficient is a physical constant representing the charge transport characteristics of a semiconductor material. Even when the same MXene is manufactured, the Hall scattering coefficient shows a value of 2.49, for example, when the surface functional group is formed as 100% fluorine, 0.5 when the surface functional group is formed as 100% oxygen, and 1 when the surface functional group is formed as 100% hydroxyl, and through this, the type of surface functional group can be determined.

[0027] In one embodiment, M may be at least one transition metal selected from elements of Group 3, Group 4, Group 5, and Group 6 of the periodic table.

[0028] More specifically, the above M may be at least one transition metal selected from Sc, Y, Lu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.

[0029] In one embodiment, the A layer may be at least one selected from the elements of Group 12, Group 13, Group 14, Group 15 and Group 16 of the periodic table.

[0030] More specifically, the A layer may be composed of at least one selected from Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb.

[0031] In one embodiment, X may be carbon (C), nitrogen (N), or a combination thereof.

[0032] In one embodiment, the inorganic compound of the MAX composition is a layered hexagonal carbide, nitride, or carbonitride called the "MAX phase," and the MAX phase has a structure in which a carbide and / or nitride layer (MXene) and an A layer are alternately arranged by stacking with ionic metallic bonds, wherein unit cells in which one X atom is located inside six transition metal (M) atoms arranged in an octahedral shape are arranged in two dimensions.

[0033] According to one embodiment of the present invention, MXene can be produced by selectively removing layer A from the MAX phase, and such MXene has surface functional groups formed thereon.

[0034] These surface functional groups are functional groups bonded to the surface of MXene and may include, for example, oxide (O), epoxide, hydroxide (OH), carbon 1-5 alkoxide, fluoride (F), chloride (Cl), bromide (Br), iodide (I), or a combination thereof.

[0035] In one embodiment, the step of removing the A layer to form MXene can be performed under acidic conditions.

[0036] Specifically, the step of removing the A layer can be performed by treating an inorganic compound of MAX composition with a strong acid capable of reacting with an A atom, thereby etching and removing the A layer.

[0037] The acid capable of etching the above A layer may be an organic acid or an inorganic acid, and as long as it can remove the A atomic layer from the MAX phase, it may be applied in a gaseous or liquid phase.

[0038] In one embodiment, the removal step of layer A can be performed using a strong acid containing fluorine atoms.

[0039] Specifically, the strong acid may be hydrofluoric acid (HF) or an alkali metal difluoride such as LiHF2, NaHF2, or KHF2, and additionally, the strong acid may be a fluorine-containing compound capable of similarly producing hydrofluoric acid in the presence of an acid.

[0040] More specifically, the fluorine-containing compound may be, for example, lithium fluoride (LiF), sodium fluoride (NaF), magnesium fluoride (MgF2), strontium fluoride (SrF2), beryllium fluoride (BeF2), calcium fluoride (CaF2), ammonium fluoride (NH4F), ammonium difluoride (NH4HF2), ammonium hexafluoroaluminate ((NH4)3AlF6), or a combination thereof.

[0041] These fluorine-containing compounds can be mixed with strong acids, such as hydrochloric acid, sulfuric acid, nitric acid, or combinations thereof, and used as an etching solution to remove layer A.

[0042] In one embodiment, the step of removing layer A from the MAX bulk phase of the MAX composition to form MXene can be performed in a temperature range of 20 to 800°C.

[0043] Specifically, the step of removing layer A from the MAX bulk phase of the MAX composition to form MXene can be performed at 20°C or higher, 22°C or higher, 24°C or higher, 26°C or higher, 28°C or higher, 30°C or higher, 32°C or higher, 34°C or higher, 35°C or higher, 36°C or higher, 38°C or higher, 40°C or higher, 60°C or higher, 80°C or higher, 100°C or higher, 200°C or higher, or 300°C or higher, and can also be performed at a temperature of 800°C or lower, 700°C or lower, 600°C or lower, 500°C or lower, 400°C or lower, 300°C or lower, 200°C or lower, 100°C or lower, 80°C or lower, 60°C or lower, 40°C or lower, 38°C or lower, 36°C or lower, or 35°C or lower.

[0044] In one embodiment, the step of measuring the Hall scattering coefficient may be performed by applying a magnetic field in a direction perpendicular to the MXene and measuring the current in a direction horizontal to the MXene.

[0045] Specifically, as schematically shown in FIG. 1, to measure the Hall scattering factor, when a magnetic field is applied in the vertical direction (B) of a MXene (e.g., Sc2C) from which layer A has been removed, electrons that would normally travel in a straight line are deflected to the right side of FIG. 1 according to the applied magnetic field. The degree of this magnetic field deflection varies depending on the surface functional groups (e.g., -F, -O, -OH) of the formed MXene, and the Hall scattering factor (Hall factor) can be measured by measuring the current in the horizontal direction of the MXene.

[0046] According to Figure 1, it can be seen that the Hall scattering coefficient varies significantly depending on the type of surface functional group.

[0047] The application fields of these Hall scattering coefficients differ based on a value of 1. As mentioned above, values ​​lower than 1, which are measured when the surface functional groups are 100% hydroxyl groups (-OH), can be utilized in high-performance transistors, high-frequency generating devices, high-efficiency sensors, photodetectors, etc., while values ​​higher than 1 can be applied in thermoelectric materials (materials for generating power using temperature differences), magnetic sensors, etc. Considering that the size of the MXene is less than a few nanometers, the size of applicable devices and the required power can be drastically reduced.

[0048] Figures 2 to 4 show the change in the Hall scattering coefficient according to temperature and electron concentration when the surface functional groups of MXene are formed as 100% fluorine groups (-F), oxygen groups (-O), and hydroxyl groups (-OH), respectively.

[0049] According to Fig. 2, Sc2C When the surface functional groups of MXene are 100% fluorine groups (-F), the Hall scattering coefficient is measured to be 1.5 or higher, and the electron concentration is 3 x 10 13 cm -2 In this case, since it appears in the region of absolute temperature 500K or higher, if the Hall scattering coefficient is measured to be 1.5 or higher, it can be determined that the manufactured Sc-2C MXene has excellent characteristics that allow it to be applied to thermoelectric materials and magnetic sensors, which are power generation materials utilizing temperature differences.

[0050] According to Fig. 3, Sc2C When the surface functional group of the MXene is 100% oxygen (-O) group, the Hall scattering coefficient is measured to have a value in the range of 0.3 to 0.6, and unlike when the surface functional group is 100% fluorine group, it can be confirmed that the value is obtained over a considerably wide range. From this, it means that when the Hall scattering coefficient is measured in the range of 0.3 to 0.6, the MXene can be utilized under a wider range of application conditions, and since the Hall scattering coefficient is measured to be a value lower than 1, for example, 0.3 to 0.6, even at absolute temperatures above 500K, it can be determined that the measured MXene has excellent characteristics for application in high-performance transistors, high-frequency generating devices, high-efficiency sensors, and photodetectors.

[0051] According to Fig. 4, Sc2C In the case where the surface functional groups of MXene are 100% hydroxyl groups (-OH), it can be confirmed that the Hall scattering coefficient approaches 1 at temperatures below 500K absolute temperature, but low electron concentration (10 11 cm -2 It can be confirmed that under conditions of ) and high temperature (absolute temperature 600K or higher), the value is measured to be much lower than 1. From this, it can be expected that excellent electron transport characteristics can be utilized in the corresponding temperature and electron concentration range.

[0052] From the results of Figures 2 to 4, it can be seen that the type of surface functional group of the MXene can be determined by combining the measured values ​​with the temperature and electron concentration of the Hall scattering coefficient of the MXene.

[0053] As previously mentioned, the results of Figures 2 to 4 represent only cases where the surface functional groups of the MXene are formed as 100% fluorine groups (-F), oxygen groups (-O), and hydroxyl groups (-OH), respectively.

[0054] That is, in one embodiment of the present invention, if the Hall scattering coefficient is 1.5 or higher, the surface functional group can be determined to be a fluorine group; if the Hall scattering coefficient is 0.9 to 1.1, the surface functional group can be determined to be a hydroxyl group; and if the Hall scattering coefficient is 0.3 to 0.6, the surface functional group can be determined to be an oxygen group.

[0055] Meanwhile, depending on the manufacturing process of MXene, most forms consist of two or more functional groups mixed together rather than 100% of a single surface functional group.

[0056] Figure 5 shows the surface functional groups that may exist in Sc2C MXene and their formation energies. In this case, the formation energy is a quantitative indicator that can predict the stability of the surface functional groups before predicting electrical properties, and from the results of Figure 5, it can be expected that the surface functional groups of Sc2C MXene are likely to exist in a mixed form of fluorine groups and hydroxyl groups.

[0057] In one embodiment, the step of determining the surface functional group distribution may involve determining that the surface functional group is two or more selected from oxygen (-O), hydroxyl (-OH), and fluorine (-F), and determining the fraction of said two or more surface functional groups.

[0058] In one embodiment, in the step of determining the surface functional group distribution of the MXene from the measured value of the Hall scattering coefficient of the MXene, if the Hall scattering coefficient is 0.8 or higher, the surface functional group can be determined to be a mixture of hydroxyl groups and fluorine groups.

[0059] In one embodiment, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 When measured within the following electron concentration range and the Hall scattering coefficient is measured to be less than 1, the fraction of the surface functional group, i.e., the mixture of fluorine group and hydroxyl group, can be determined to be fluorine group : hydroxyl group 1 : 1 or less.

[0060] Specifically, the above Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 When measured within the following electron concentration range and the Hall scattering coefficient is measured to be less than 0.9, the fraction of the surface functional group can be determined to be fluorine group:hydroxyl group 1:5 or less.

[0061] In addition, specifically, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 When measured within the following electron concentration range and the Hall scattering coefficient is measured to be 0.9 or higher and less than 1, the fraction of the surface functional group can be determined to be greater than 1:5 and less than 1:5, with a fluorine group : hydroxyl group ratio.

[0062] In addition, specifically, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 When measured within the following electron concentration range and the Hall scattering coefficient is measured to be 1 or greater and less than 1.2, the fraction of the surface functional group can be determined to be greater than 1.5:1 and less than or equal to 5:1 for the fluorine group : hydroxyl group.

[0063] In addition, specifically, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 When measured within the following electron concentration range and the Hall scattering coefficient is measured to be greater than 1.2, the fraction of the surface functional group can be determined to be greater than 5:1 for fluorine groups : hydroxyl groups.

[0064] In one embodiment, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Excess and 10 12 cm -2 When measured in a range of electron concentrations less than 1 and the Hall scattering coefficient is 1 to 1.1, the fraction of the surface functional group can be determined to be fluorine group : hydroxyl group 1 : 1 or less.

[0065] In one embodiment, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Excess and 10 12 cm -2 When measured in a range of electron concentrations less than 1.1 and the Hall scattering coefficient is greater than 1.1, the fraction of the surface functional groups can be determined to be greater than 1:1, with a fluorine group : hydroxyl group ratio.

[0066] In one embodiment, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 12 cm -2 When measured within the above electron concentration range and the above Hall scattering coefficient is greater than 1, the fraction of the surface functional group can be determined to be fluorine group : hydroxyl group 2 : 1 or less.

[0067] In one embodiment, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 12 cm -2When measured within the above electron concentration range and the above Hall scattering coefficient is 1 or less, the surface functional group can be determined to have a fraction of fluorine group : hydroxyl group greater than 2 : 1.

[0068] FIGS. 6a to 6d show the change in the Hall coefficient according to the fraction of two functional groups (F:OH) when fluorine groups and hydroxyl groups are present on the surface of Sc2C MXene according to one embodiment of the present invention.

[0069] According to Figures 6a to 6d, when fluorine groups and hydroxyl groups exist in a mixed form on the surface of MXene, it can be confirmed that the Hall scattering coefficient changes according to the fraction of fluorine groups and hydroxyl groups. Specifically, it can be seen that depending on the measurement temperature and electron concentration, regions with values ​​greater than 1 and regions with values ​​less than 1 are mainly observed. Through this, it can be seen that when the surface functional groups of MXene are in a mixed form of fluorine groups and hydroxyl groups, the electron mobility becomes faster and it can operate as a high-performance switch.

[0070] FIGS. 7a to 7d show the change in the Hall coefficient according to the fraction of two functional groups (F:OH) at room temperature when fluorine and hydroxyl groups are present on the surface of Sc2C MXene according to one embodiment of the present invention.

[0071] According to Figures 7a to 7d, when measuring the Hall scattering coefficient at room temperature, it can be seen that the value varies depending on the electron concentration and the relative fraction of fluorine groups and hydroxyl groups, and through this, it can be seen that the fraction of surface functional groups can be predicted from the measured Hall scattering coefficient under specific temperature and electron concentration conditions.

[0072] From the results of FIGS. 6a to 6d and FIGS. 7a to 7d, it can be seen that, likewise, the Hall scattering coefficient measurement temperature and electron concentration of the MXene, and the measured values, can be combined to determine not only the type of surface functional group of the MXene but also its fraction.

[0073] FIG. 8 schematically illustrates a method for optimizing a MXene process using a method for determining the type and fraction of MXene surface functional groups according to an embodiment of the present invention.

[0074] As shown in Fig. 8, by measuring the Hall scattering coefficient of the manufactured MXene, it is determined whether the desired surface functional groups are distributed in the desired fraction, and accordingly, variables of the MXene manufacturing process, such as the concentration of acid for etching, the manufacturing temperature, or the time, can be changed, thereby optimizing the MXene manufacturing process.

[0075] That is, according to one embodiment of the present invention, the type and fraction of MXene surface functional groups can be easily determined without using complex and costly measurement methods, which in turn allows for the modification of process conditions to ultimately produce MXene having the desired purity, fraction, and physical properties of the surface functional groups, and through the repetition of this series of processes, the manufacturing process of MXene suitable for various applications can be optimized.

[0077] As one embodiment, the present invention may provide the following embodiments.

[0078] The first embodiment comprises the step of preparing a MAX bulk phase of MAX composition;

[0079] A step of forming MXene by removing layer A from the MAX bulk phase of the above MAX composition;

[0080] A step of measuring the Hall scattering coefficient by measuring the above MXene; and

[0081] The method includes the step of determining the surface functional group distribution of the MXene from the measured value of the Hall scattering coefficient of the MXene.

[0082] The above M is at least one transition metal selected from elements of Group 3, Group 4, Group 5, and Group 6 of the periodic table, the above A layer is at least one selected from elements of Group 12, Group 13, Group 14, Group 15, and Group 16 of the periodic table, and the above X is carbon (C), nitrogen (N), or a combination thereof.

[0083] The step of determining the surface functional group distribution above is,

[0084] A method for classifying surface functional groups of MXene can be provided, wherein the surface functional groups are determined to be two or more selected from oxygen groups (-O), hydroxyl groups (-OH), and fluorine groups (-F), and the fraction of said two or more surface functional groups is determined.

[0085] A second embodiment can provide a method for classifying surface functional groups of MXene, characterized in that, in the first embodiment, M is at least one transition metal selected from Sc, Y, Lu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

[0086] A third embodiment may provide a method for classifying surface functional groups of MXene, characterized in that, in one or more of the first and second embodiments, the A layer is composed of at least one selected from Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb.

[0087] A fourth embodiment may provide a method for classifying surface functional groups of MXene, wherein, in one or more of the first to third embodiments, the step of removing layer A is performed using a strong acid containing fluorine atoms.

[0088] A fifth embodiment may provide a method for classifying surface functional groups of MXene, wherein, in one or more of the first to fourth embodiments, the removal step of the A layer is performed using one or more selected from hydrofluoric acid (HF), LiHF2, NaHF2, KHF2, lithium fluoride (LiF), sodium fluoride (NaF), magnesium fluoride (MgF2), strontium fluoride (SrF2), beryllium fluoride (BeF2), calcium fluoride (CaF2), ammonium fluoride (NH4F), ammonium difluoride (NH4HF2), ammonium hexafluoroaluminate ((NH4)3AlF6) or a combination thereof, or a combination thereof with one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0089] A sixth embodiment may provide a method for classifying surface functional groups of a MXene, wherein, in one or more of the first to fifth embodiments, the step of measuring the Hall scattering coefficient is performed by applying a magnetic field in a direction perpendicular to the MXene and measuring the current in a direction horizontal to the MXene.

[0090] The seventh embodiment can provide a method for classifying surface functional groups of MXene, characterized in that in one or more of the first to sixth embodiments, when the Hall scattering coefficient is 0.8 or higher, the surface functional group is determined to be a mixture of hydroxyl groups and fluorine groups.

[0091] The eighth embodiment is, in one or more of the first to seventh embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Measured in the following range of electron concentration,

[0092] A method for classifying surface functional groups of MXene can be provided, characterized by determining that when the above-mentioned Hall scattering coefficient is less than 1, the fraction of the surface functional groups is fluorine group : hydroxyl group 1 : 1 or less.

[0093] The ninth embodiment can provide a method for classifying surface functional groups of MXene, characterized in that in one or more of the first to eighth embodiments, when the Hall scattering coefficient is less than 0.9, the fraction of the surface functional groups is determined to be fluorine group:hydroxyl group 1:5 or less.

[0094] The 10th embodiment can provide a method for classifying surface functional groups of MXene, characterized in that, in one or more of the 1st to 9th embodiments, when the Hall scattering coefficient is 0.9 or higher and less than 1, the fraction of the surface functional groups is determined to be greater than 1:5 and less than 1:5, where the fluorine group : hydroxyl group.

[0095] The 11th embodiment is, in one or more of the 1st to 10th embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Measured in the following range of electron concentration,

[0096] A method for classifying surface functional groups of MXene can be provided, characterized by determining that when the above-mentioned Hall scattering coefficient is 1 or more and less than 1.2, the fraction of the surface functional groups is greater than 1.5:1 and less than or equal to 5:1 for fluorine groups : hydroxyl groups.

[0097] The 12th embodiment is, in one or more of the 1st to 11th embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Measured in the following range of electron concentration,

[0098] A method for classifying surface functional groups of MXene can be provided, characterized by determining that when the above-mentioned Hall scattering coefficient is greater than 1.2, the fraction of the surface functional groups is greater than 5:1 for fluorine groups : hydroxyl groups.

[0099] The 13th embodiment is, in one or more of the 1st to 12th embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Excess and 10 12 cm -2 Measured in a range of less than the electron concentration,

[0100] A method for classifying surface functional groups of MXene can be provided, characterized in that when the above-mentioned Hall scattering coefficient is 1 to 1.1, the fraction of the surface functional groups is determined to be fluorine group : hydroxyl group 1 : 1 or less.

[0101] The 14th embodiment is, in one or more of the 1st to 13th embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Excess and 10 12 cm -2 Measured in a range of less than the electron concentration,

[0102] A method for classifying surface functional groups of MXene can be provided, characterized by determining that when the above-mentioned Hall scattering coefficient is greater than 1.1, the fraction of the surface functional groups is greater than 1:1 for fluorine groups : hydroxyl groups.

[0103] The 15th embodiment is, in one or more of the 1st to 14th embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 12 cm -2 Measured in the above electron concentration range,

[0104] A method for classifying surface functional groups of MXene can be provided, characterized by determining that when the above-mentioned Hall scattering coefficient is greater than 1, the fraction of the surface functional groups is fluorine group:hydroxyl group 2:1 or less.

[0105] The 16th embodiment is, in one or more of the 1st to 15th embodiments, wherein the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 12 cm -2 Measured in the above electron concentration range,

[0106] A method for classifying surface functional groups of MXene can be provided, characterized in that when the above-mentioned Hall scattering coefficient is 1 or less, the surface functional group is determined to have a fraction of fluorine group : hydroxyl group greater than 2 : 1.

[0108] With reference to the foregoing descriptions, those skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features.

[0109] Therefore, it must be understood that the embodiments described above are exemplary in all respects and are not intended to limit the invention to the embodiments described above, and the scope of the invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included within the scope of the invention.

Claims

Claim 1 A method for classifying surface functional groups of MXene, comprising: a step of preparing a MAX bulk phase of MAX composition; a step of removing layer A from the MAX bulk phase of MAX composition to form MXene; a step of measuring the MXene by Hall measurement to measure the Hall scattering coefficient; and a step of determining the surface functional group distribution of the MXene from the measured value of the Hall scattering coefficient of the MXene; wherein M is at least one transition metal selected from elements of Group 3, Group 4, Group 5, and Group 6 of the periodic table, and layer A is at least one selected from elements of Group 12, Group 13, Group 14, Group 15, and Group 16 of the periodic table, and X is carbon (C), nitrogen (N), or a combination thereof, and the step of determining the surface functional group distribution is to determine that the surface functional groups are two or more selected from oxygen groups (-O), hydroxyl groups (-OH), and fluorine groups (-F), and to determine the fraction of said two or more surface functional groups. Claim 2 A method for classifying surface functional groups of MXene, characterized in that, in claim 1, M is at least one transition metal selected from Sc, Y, Lu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W. Claim 3 A method for classifying surface functional groups of MXene, characterized in that, in claim 1, the A layer is composed of at least one selected from Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb. Claim 4 A method for classifying surface functional groups of MXene, characterized in that, in claim 1, the removal step of layer A is performed using a strong acid containing fluorine atoms. Claim 5 A method for classifying surface functional groups of MXene, wherein, in claim 4, the removal step of layer A is performed using one or more selected from hydrofluoric acid (HF), LiHF2, NaHF2, KHF2, lithium fluoride (LiF), sodium fluoride (NaF), magnesium fluoride (MgF2), strontium fluoride (SrF2), beryllium fluoride (BeF2), calcium fluoride (CaF2), ammonium fluoride (NH4F), ammonium difluoride (NH4HF2), ammonium hexafluoroaluminate ((NH4)3AlF6) or a combination thereof, or a combination thereof with one or more of hydrochloric acid, sulfuric acid, and nitric acid. Claim 6 A method for classifying surface functional groups of a MXene, characterized in that, in claim 1, the step of measuring the Hall scattering coefficient is performed by applying a magnetic field in a direction perpendicular to the MXene and measuring the current in a direction horizontal to the MXene. Claim 7 A method for classifying surface functional groups of MXene, characterized in that, in the first paragraph, when the Hall scattering coefficient is 0.8 or higher, the surface functional group is determined to be a mixture of hydroxyl groups and fluorine groups. Claim 8 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured within the following electron concentration range, and when the Hall scattering coefficient is less than 1, determining that the fraction of the surface functional groups is fluorine group : hydroxyl group 1 : 1 or less. Claim 9 A method for classifying surface functional groups of MXene, characterized in that, in claim 8, when the above-mentioned Hall scattering coefficient is less than 0.9, the fraction of the above-mentioned surface functional groups is determined to be fluorine group:hydroxyl group 1:5 or less. Claim 10 A method for classifying surface functional groups of MXene, characterized in that, in claim 8, when the above-mentioned Hall scattering coefficient is 0.9 or higher and less than 1, the fraction of the above-mentioned surface functional groups is determined to be greater than 1:5 and less than or equal to 1:5, where fluorine group : hydroxyl group. Claim 11 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured within the following electron concentration range, and when the Hall scattering coefficient is 1 or greater and less than 1.2, determining that the fraction of surface functional groups is greater than fluorine group:hydroxyl group and less than or equal to 5:

1. Claim 12 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured within the following electron concentration range, and when the Hall scattering coefficient is greater than 1.2, determining that the fraction of surface functional groups is greater than 5:1 for fluorine groups : hydroxyl groups. Claim 13 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Excess and 10 12 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured in a range of electron concentrations less than 1, and when the Hall scattering coefficient is 1 to 1.1, determining that the fraction of the surface functional groups is fluorine group : hydroxyl group 1 : 1 or less. Claim 14 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 9 cm -2 Excess and 10 12 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured in a range of electron concentrations less than 1, and when the Hall scattering coefficient is greater than 1.1, determining that the fraction of the surface functional groups is greater than 1:1 for fluorine groups : hydroxyl groups. Claim 15 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 12 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured in the above electron concentration range, and when the above Hall scattering coefficient is greater than 1, determining that the fraction of the surface functional groups is fluorine group : hydroxyl group 2 : 1 or less. Claim 16 In claim 7, the Hall scattering coefficient is in an absolute temperature range of 200K to 500K and 10 12 cm -2 A method for classifying surface functional groups of MXene, characterized by being measured in the above electron concentration range, and when the above Hall scattering coefficient is 1 or less, determining that the fraction of fluorine groups to hydroxyl groups of the surface functional group is greater than 2:1.

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