Graphene-supported metal monatomic atom material, preparation method and application thereof

Abstract

The application relates to a graphene-supported metal monatomic material and a preparation method and application thereof, and the preparation method of the graphene-supported metal monatomic material comprises the following steps: placing graphene, a metal source and a template salt in a dispersing agent to prepare a dispersion system; freeze-drying the dispersion system to obtain a precursor powder; performing heat treatment on the precursor powder in a non-oxidizing atmosphere; and washing and freeze-drying the heat treatment product. The graphene-supported metal monatomic material has a porous structure, a larger specific surface area, better dispersity of graphene and metal monatomic in the internal organization, less stacked graphene, a larger effective utilization area of graphene, more favorable formation of a gas-solid-liquid three-phase interface, less metal clusters, and thus higher catalytic activity of the material, and the material is particularly suitable for being used as an oxygen reduction reaction catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical catalytic materials, in particular to a graphene supported metal monatomic material and a preparation method and application thereof. BACKGROUND

[0002] To meet the increasing demand for energy, while addressing the increasing environmental problems, it is necessary to develop clean and sustainable new energy devices, such as proton exchange membrane fuel cells and metal-air batteries. Due to the slow reaction kinetics process of the cathode oxygen reduction reaction and the poor stability of the oxygen reduction reaction catalyst, the cathode is the bottleneck of these devices. It is imperative to develop a cathode oxygen reduction reaction catalyst with high activity and good durability. At present, the most commonly used catalyst is platinum nanocatalyst. However, the scarcity and high cost of platinum limit the widespread application of these new energy devices. The high intrinsic activity and low cost of constituent elements of monatomic catalyst make monatomic catalyst an ideal choice to replace platinum nanocatalyst. The intrinsic catalytic activity of monatomic catalyst depends on the content of monatomic, coordination environment and the morphology of the carrier.

[0003] Graphene has high specific surface area and high electrical conductivity, and is a good carrier for loading metal monatomic. However, in the preparation of graphene supported monatomic catalyst, graphene is prone to stacking, reducing the effective utilization area of graphene, and is not conducive to the formation of gas-liquid-solid three-phase interface. At the same time, in the preparation method of traditional graphene supported monatomic catalyst, the monatomic metal precursor is easy to migrate, causing the agglomeration of metal atoms, forming clusters, and reducing the catalytic activity. SUMMARY

[0004] Therefore, it is necessary to provide a graphene supported metal monatomic material and a preparation method and application thereof, which can avoid the stacking of graphene and the agglomeration of metal atoms in the preparation method of traditional graphene supported monatomic catalyst.

[0005] In one aspect of the present application, a preparation method of a graphene supported metal monatomic material is provided, comprising the following steps:

[0006] The graphene, metal source and template salt are placed in a dispersant to form a dispersion system;

[0007] The dispersion system is freeze-dried to obtain a precursor powder;

[0008] The precursor powder is heat treated in a non-oxidizing atmosphere;

[0009] The heat treated product is washed with water and freeze-dried;

[0010] The metal element in the metal source is a noble metal element or a transition metal element,

[0011] The heat treatment temperature is higher than the decomposition temperature of the metal source,

[0012] The template salt is a water-soluble salt, the decomposition temperature and the melting temperature of the template salt are both higher than the temperature of the heat treatment, and the template salt and the metal source do not react with the graphene,

[0013] The mass of the template salt is at least 2.5 times the mass of the metal source, and the mass of the graphene is not more than the mass of the template salt.

[0014] In some embodiments, the mass ratio of the graphene, the metal source and the template salt is 1:(0.01-0.4):(1-10).

[0015] In some embodiments, the ratio of the dispersoid and the dispersant in the dispersion system is 0.1 mg / mL-5 mg / mL, wherein the dispersoid is the graphene, the metal source and the template salt.

[0016] In some embodiments, the graphene is one or more of graphene oxide, nitrogen-doped graphene, sulfur-doped graphene and phosphorus-doped graphene.

[0017] In some embodiments, the metal element in the metal source is platinum, iron, nickel or cobalt.

[0018] In some embodiments, the metal source is selected from chloroplatinic acid, potassium chloroplatinate or ammonium chloroplatinate, and the template salt is sodium chloride or potassium chloride.

[0019] In some embodiments, the heat treatment temperature is 400-750°C.

[0020] In some embodiments, the heat treatment time is 30-120 min.

[0021] In yet another aspect of the present application, a graphene-supported metal monatomic material prepared by the preparation method is provided.

[0022] In yet another aspect of the present application, the graphene-supported metal monatomic material is used as a catalyst.

[0023] Compared with the prior art, the present application has at least the following beneficial effects:

[0024] The preparation method of the graphene supported metal monatomic material provided in the application mixes a large dose of template salt and graphene, metal source together. Since the amount of the template salt is much larger than that of the metal source, the metal source particles are surrounded by the template salt, which plays a fixing role and inhibits the migration and aggregation of the metal atoms during the heat treatment. At the same time, since the template salt can stably exist during the heat treatment, the contact between the graphenes is reduced, thereby inhibiting the stacking of the graphenes. Moreover, since the template salt is a water-soluble salt, the heat treatment product is washed with water, the template salt is dissolved in water, and holes are formed at the positions where the template salt originally exists, so that the finally prepared material has a porous structure.

[0025] The graphene supported metal monatomic material provided in the application has a porous structure, a larger specific surface area, better dispersity of the graphene and the metal monatomic in the internal organization, less stacked graphene, a larger effective utilization area of the graphene, and is more conducive to forming a gas-liquid-solid three-phase interface and less metal clusters, so that the material has higher catalytic activity and is particularly suitable for use as an oxygen reduction reaction catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The scanning electron microscope photos of the overall morphology of the materials prepared in Examples 1-5;

[0028] Figure 2 The scanning electron microscope photos of the overall morphology of the materials prepared in Comparative Examples 1-2;

[0029] Figure 3 The transmission electron microscope photos of the local enlarged parts of the materials prepared in Examples 1-5;

[0030] Figure 4 The transmission electron microscope photos of the local enlarged parts of the materials prepared in Comparative Examples 1-2. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the application, the application will be described more fully below with reference to the related drawings. The preferred embodiments of the application are shown in the drawings. However, the application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the application more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0033] Herein, in the technical features described in an open-ended manner, both the closed technical solution consisting of the listed features and the open technical solution containing the listed features are included.

[0034] Herein, in relation to numerical intervals, unless otherwise specified, the numerical intervals are considered to be continuous, and include the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value. Further, when the range refers to integers, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood as including any and all sub-ranges subsumed therein.

[0035] Herein, in relation to the unit of data range, if only the right end point is followed by a unit, it means that the units of the left end point and the right end point are the same. For example, 0.3-0.5 m / s means that the units of the left end point "0.3" and the right end point "0.5" are both m / s (meter / second).

[0036] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individual disclosed point or single numerical value can itself be combined as a lower limit or an upper limit with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0037] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0038] In one aspect of the present application, a method for preparing a graphene-supported metal monatomic material is provided, comprising the following steps:

[0039] (a) placing graphene, a metal source and a template salt into a dispersant to form a dispersion system;

[0040] (b) freeze-drying the dispersion system to obtain a precursor powder;

[0041] (c) heat-treating the precursor powder in a non-oxidizing atmosphere;

[0042] (d) washing the heat-treated product with water and freeze-drying.

[0043] It should be noted that perfect graphene is not suitable for the present application. The graphene of the present application has oxygen-containing functional groups, which can be graphene oxide, or heteroatom-doped graphene oxide, such as nitrogen-doped graphene oxide, sulfur-doped graphene oxide, phosphorus-doped graphene oxide, and combinations thereof. Preferably, the graphene is heteroatom-doped graphene oxide. The oxygen content of the graphene of the present application is not particularly limited and can be selected from those most suitable for the intended purpose, i.e., those that facilitate improved catalytic performance of the material. The number of layers of the graphene of the present application is not particularly limited and can be selected from those most suitable for the intended purpose, i.e., those that facilitate improved catalytic performance of the material. The graphene of the present application is typically in the form of sheet-like graphene, the size of which is not particularly limited and can be selected from those most suitable for the intended purpose, i.e., those that facilitate improved catalytic performance of the material.

[0044] The metal element in the metal source can include, but is not limited to, at least one of palladium (Pd), rhodium (Rh), iridium (Ir), platinum (Pt), gold (Au), silver (Ag), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). The metal source can be an acid, a base, or a salt of any form of these metal elements. Preferably, the metal source can be adsorbed on the graphene.

[0045] In some preferred embodiments, the metal element in the metal source is platinum, iron, nickel, or cobalt. These metal elements have better catalytic activity when doped into graphene. The terms "supported" and "doped" have the same meaning herein, both referring to the combination of metal monomers and graphene. This combination can be a physical action, a chemical action, or both. The specific action can be determined by the specific metal source, the heat treatment temperature, and other conditions in combination with common knowledge.

[0046] The template salt is a water-soluble salt that can be dissolved in water when washed with water after heat treatment, and removed from the material structure. The decomposition temperature and the melting temperature of the template salt are both higher than the temperature of the heat treatment, which can ensure that the template salt is stable during the heat treatment. Understandably, the template salt does not react with the graphene or the metal source. The temperature of the heat treatment needs to be determined by the metal source, and the temperature of the heat treatment needs to be higher than the decomposition temperature of the metal source so that the metal source can be decomposed to form metal atoms during the heat treatment.

[0047] In some embodiments, the metal source is selected from chloroplatinic acid, potassium chloroplatinate or ammonium chloroplatinate, and the template salt is selected from sodium chloride or potassium chloride. Preferably, the heat treatment temperature is any value between 400 °C and 750 °C, it being understood that the heat treatment temperature can also be 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C. The heat treatment time can be any value between 30 min and 120 min, it being understood that the heat treatment time can also be 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min.

[0048] When preparing the graphene-supported metal monatomic material, the mass of the template salt is at least 2.5 times the mass of the metal source, and the mass of the graphene is not more than the mass of the template salt. The mass ratio of the metal source and the graphene is not particularly limited and can be selected from those most suitable for the intended purpose, i.e. those that facilitate improved catalytic performance of the material.

[0049] In some embodiments, the mass ratio of graphene, the metal source and the template salt is any value between 1 : (0.01-0.4) : (1-10). It is understood that the mass ratio of graphene, the metal source and the template salt can be 1 :0.01 :1, 1 :0.02 :1, 1 :0.03 :1, 1 :0.04 :1, 1 :0.05 :1, 1 :0.06 :1, 1 :0.07 :1, 1 :0.08 :1, 1 :0.09 :1, 1 :0.1 :1, 1 :0.11 :1, 1 :0.12 :1, 1 :0.13 :1, 1 :0.14 :1, 1 :0.15 :1, 1 :0.16 :1, 1 :0.17 :1, 1 :0.18 :1, 1 :0.19 :1, 1 :0.2 :1, 1 :0.21 :1, 1 :0.22 :1, 1 :0.23 :1, 1 :0.24 :1, 1 :0.25 :1, 1 :0.26 :1, 1 :0.27 :1, 1 :0.28 :1, 1 :0.29 :1, 1 :0.3 :1, 1 :0.31 :1, 1 :0.32 :1, 1 :0.33 :1, 1 :0.34 :1, 1 :0.35 :1, 1 :0.36 :1, 1 :0.37 :1, 1 :0.38 :1, 1 :0.39 :1, 1 :0.4 :1, 1 :0.4 :1.5, 1 :0.4 :2, 1 :0.4 :3, 1 :0.4 :4, 1 :0.4 :5, 1 :0.4 :6, 1 :0.4 :7, 1 :0.4 :8, 1 :0.4 :9, 1 :0.4 :10.

[0050] The graphene, metal source and template salt in the dispersion system are dispersed in the dispersant. The dispersant can be water or an organic solvent such as methanol, ethanol or acetone, which is easy to remove in freeze drying. The concentration of the solute in the dispersion system should not be too low or too high. If the concentration is too low, it is not conducive to the removal of the dispersant in the freeze drying step, and if the concentration is too high, it is not conducive to the uniform dispersion of the dispersed substance. In some embodiments, the ratio of the dispersed substance and the dispersant is 0.1 mg / mL to 5 mg / mL, that is, 0.1 mg to 5 mg of the dispersed substance can be added to 1 mL of water. Understandably, in order to ensure the uniformity of the dispersed substance in the dispersion system, a mechanical stirring step or the like can be further added.

[0051] The temperature and time of freeze drying in step (b) are not particularly limited, and can be any conventional temperature and time of freeze drying in the art, for the purpose of removing the dispersant in the dispersion system as much as possible.

[0052] The precursor powder is directly obtained after freeze drying, and the size thereof is not limited.

[0053] The non-oxidizing atmosphere can be vacuum or inert atmosphere.

[0054] The temperature and time of freeze drying in step (d) are not particularly limited, and can be any conventional temperature and time of freeze drying in the art, for the purpose of removing the dispersant in the dispersion system as much as possible.

[0055] In another aspect, the application provides a graphene-supported metal monatomic material prepared by the preparation method of any one of the above embodiments. The graphene-supported metal monatomic material has a porous structure.

[0056] In some embodiments, the specific surface area of the graphene-supported metal monatomic material is 100 to 1000 m 2 / g.

[0057] In some embodiments, the porosity of the graphene-supported metal monatomic material is 25% to 55%.

[0058] In some embodiments, the loading amount of the metal monatomic in the graphene-supported metal monatomic material is 1 wt% to 10 wt%. The loading amount is calculated according to the formula: mass of metal monatomic / (mass of metal monatomic + mass of graphene).

[0059] In some embodiments, the content of the metal cluster in the graphene-supported metal monatomic material is less than 0.1 wt%.

[0060] In another aspect, the application also provides the use of the graphene-supported metal monatomic material as a catalyst. For example, it can be used as an oxygen reduction reaction catalyst.

[0061] The following are specific examples. The purpose is to make further detailed description of the present application, to help the skilled and researchers further understand the present application, and the relevant technical conditions do not constitute any limitation on the present application. Any form of modification made within the scope of the claims of the present application is within the scope of protection of the claims of the present application.

[0062] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. The instruments are all selected according to the conventional selection in the art. The experimental methods not specified in the examples are carried out according to the conventional conditions, such as the conditions described in the literature, books or the methods recommended by the manufacturer.

[0063] Example 1

[0064] (1) 100 mg of graphene, 40 mg of chloroplatinic acid and 100 mg of sodium chloride were weighed respectively and dispersed in 240 ml of deionized water to obtain a graphene-chloroplatinic acid-NaCl dispersion system.

[0065] (2) The graphene-chloroplatinic acid-NaCl dispersion system obtained in step (1) was freeze-dried to obtain a precursor powder.

[0066] (3) The precursor powder obtained in step (2) was placed in a heat treatment furnace and heat treated at 500°C for 1 h.

[0067] (4) The heat treated product obtained in step (3) was washed with deionized water to remove NaCl and freeze-dried to obtain a graphene-supported metal monatomic material.

[0068] Example 2

[0069] (1) 100 mg of graphene, 1 mg of chloroplatinic acid and 100 mg of sodium chloride were weighed respectively and dispersed in 201 mL of deionized water to obtain a graphene-chloroplatinic acid-NaCl dispersion system.

[0070] (2) The graphene-chloroplatinic acid-NaCl dispersion system obtained in step (1) was freeze-dried to obtain a precursor powder.

[0071] (3) The precursor powder obtained in step (2) was placed in a heat treatment furnace and heat treated at 500°C for 1 h.

[0072] (4) The heat treated product obtained in step (3) was washed with deionized water to remove NaCl and freeze-dried to obtain a graphene-supported metal monatomic material.

[0073] Example 3

[0074] (1) 100 mg of graphene, 40 mg of chloroplatinic acid, and 1000 mg of sodium chloride were weighed out respectively and dispersed in 1140 mL of deionized water to obtain a graphene-chloroplatinic acid-NaCl dispersion system.

[0075] (2) The graphene-chloroplatinic acid-NaCl dispersion system obtained in step (1) was freeze-dried to obtain a precursor powder.

[0076] (3) The precursor powder obtained in step (2) was placed in a heat treatment furnace and heat treated at 500°C for 1 h.

[0077] (4) The heat treatment product obtained in step (3) was washed with deionized water to remove NaCl and freeze-dried to obtain a graphene-supported metal monatomic material.

[0078] Example 4

[0079] (1) 100 mg of graphene, 40 mg of chloroplatinic acid, and 100 mg of sodium chloride were weighed out respectively and dispersed in 24 mL of deionized water to obtain a graphene-chloroplatinic acid-NaCl dispersion system.

[0080] (2) The graphene-chloroplatinic acid-NaCl dispersion system obtained in step (1) was freeze-dried to obtain a precursor powder.

[0081] (3) The precursor powder obtained in step (2) was placed in a heat treatment furnace and heat treated at 500°C for 1 h.

[0082] (4) The heat treatment product obtained in step (3) was washed with deionized water to remove NaCl and freeze-dried to obtain a graphene-supported metal monatomic material.

[0083] Example 5

[0084] (1) 100 mg of graphene, 40 mg of chloroplatinic acid, and 100 mg of sodium chloride were weighed out respectively and dispersed in 1200 mL of deionized water to obtain a graphene-chloroplatinic acid-NaCl dispersion system.

[0085] (2) The graphene-chloroplatinic acid-NaCl dispersion system obtained in step (1) was freeze-dried to obtain a precursor powder.

[0086] (3) The precursor powder obtained in step (2) was placed in a heat treatment furnace and heat treated at 500°C for 1 h.

[0087] (4) The heat treatment product obtained in step (3) was washed with deionized water to remove NaCl and freeze-dried to obtain a graphene-supported metal monatomic material.

[0088] Comparative Example 1

[0089] The preparation method is substantially the same as that of Example 1, except that no NaCl is added.

[0090] Comparative Example 2

[0091] The preparation method is substantially the same as that of Example 1, except that the mass of chloroplatinic acid is 45 mg.

[0092] The mass of each substance in Examples 1-5 and Comparative Examples 1-2 is shown in Table 1 below:

[0093] Table 1

[0094] Graphene Chloroplatinic acid Sodium chloride Deionized water Example 1 100 mg 40 mg 100 mg 240 mL Example 2 100 mg 1 mg 100 mg 201 mL Example 3 100 mg 40 mg 1000 mg 1140 mL Example 4 100 mg 40 mg 100 mg 24 mL Example 5 100 mg 40 mg 100 mg 1200 mL Comparative Example 1 100 mg 40 mg - 240 mL Comparative Example 2 100 mg 45 mg 100 mg 240 mL

[0095] The materials prepared in Examples 1-5 and Comparative Examples 1-2 were tested for morphology and catalytic performance,

[0096] The test conditions or standards for each performance test item are as follows:

[0097] 1. Morphology

[0098] Scanning electron microscopy and transmission electron microscopy were used to study the morphology of the materials.

[0099] 2. Catalytic performance

[0100] 4 mg of the sample, 50 microliters of Nafion, and 2 ml of ethanol were ultrasonically treated for 30 minutes to obtain a slurry. 8 microliters of the slurry were added dropwise to a glass carbon electrode and allowed to dry naturally. The LSV curve was tested in a 0.5 M sulfuric acid solution under an oxygen-saturated atmosphere at 1600 rpm to obtain the catalytic ORR performance of the material. The half-wave potential was taken as a measure of the catalytic ORR performance. The larger the half-wave potential, the greater the activity of the material in catalyzing ORR, and the better the catalytic performance of the material.

[0101] The results are as follows:

[0102] 1. The scanning electron micrographs of the overall morphology of the materials prepared in Examples 1-5 are shown in Figure 1 The scanning electron micrographs of the overall morphology of the materials prepared in Comparative Examples 1 and 2 are shown in Figure 2 As can be seen from Figure 1 and Figure 2 , the materials prepared in Examples 1-5 and Comparative Example 2 have a porous structure, while the material prepared in Comparative Example 1 has no porous structure.

[0103] 2. The transmission electron micrographs of the local magnified parts of the materials prepared in Examples 1-5 are shown in Figure 3 The transmission electron micrographs of the materials prepared in Comparative Examples 1-2 are shown in Figure 4 As can be seen fromFigure 3 and Figure 4 As compared with the comparative examples 1-2, the metal atoms in the materials prepared in the examples 1-5 are in a dispersed state, and the size is far less than 2 nm, while the metal atoms in the materials prepared in the comparative examples 1-2 are in an aggregated state, forming metal clusters, and the size is about 5 nm.

[0104] 3, the results of the catalytic performance test of the examples 1-5 and the comparative examples 1-2 are shown in Table 2. As shown in the table, the catalytic ORR performance of the materials prepared in the examples 1-5 is better than that of the materials prepared in the comparative examples 1-2.

[0105] Table 2

[0106] Half-wave potential (mV vs. RHE) Example 1 635 Example 2 626 Example 3 633 Example 4 631 Example 5 638 Comparative Example 1 502 Comparative Example 2 556

[0107] The technical features of the above-described examples can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combinations of the technical features do not contradict, they should be considered as the scope of the description.

[0108] The above-described examples only express several embodiments of the present application, facilitate the specific and detailed understanding of the technical solutions of the present application, but should not be understood as the limitation of the patent protection scope of the present application. It should be pointed out that, for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by the skilled in the art through logical analysis, reasoning or limited experiments are all within the protection scope of the appended claims of the present application. Therefore, the patent protection scope of the present application should be based on the contents of the appended claims, and the description and drawings can be used to explain the contents of the claims.

Claims

1. A method for preparing a graphene-supported metal monatomic material, characterized by, The method comprises the following steps: putting graphene, a metal source and a template salt into a dispersant to form a dispersion system; freeze-drying the dispersion system to obtain a precursor powder; heat-treating the precursor powder in a non-oxidizing atmosphere; washing the heat-treated product with water and freeze-drying it; wherein the metal element in the metal source is a noble metal element or a transition metal element, the heat-treatment temperature is higher than the decomposition temperature of the metal source, the template salt is a water-soluble salt, the decomposition temperature and the melting temperature of the template salt are both higher than the heat-treatment temperature, and the template salt does not react with the graphene or the metal source, the mass of the template salt is at least 2.5 times the mass of the metal source, and the mass of the graphene is not more than the mass of the template salt; the mass ratio of the graphene, the metal source and the template salt is 1:(0.01-0.4):(1-10); and the ratio of the dispersed substance to the dispersant in the dispersion system is 0.1 mg / mL-5 mg / mL, wherein the dispersed substance is the graphene, the metal source and the template salt.

2. The method for preparing a graphene-supported metal monatomic material according to claim 1, wherein the graphene is one or more of graphene oxide, nitrogen-doped graphene, sulfur-doped graphene and phosphorus-doped graphene.

3. The method for preparing a graphene-supported metal monatomic material according to claim 1, wherein the metal element in the metal source is platinum, iron, nickel or cobalt.

4. The method for preparing graphene-supported metal single-atom materials according to claim 3, characterized in that, The metal source is selected from chloroplatinic acid, potassium chloroplatinate or ammonium chloroplatinate, and the template salt is sodium chloride or potassium chloride.

5. The method for preparing graphene-supported metal single-atom materials according to claim 4, characterized in that, The heat-treatment temperature is 400-750°C.

6. The method of claim 5, wherein the graphene-supported metal monatomic atom material is prepared by the steps of: preparing a graphene substrate; and depositing a metal monatomic atom on the graphene substrate. The heat-treatment time is 30-120 min.

7. A graphene-supported metal monatomic material prepared by the method according to any one of claims 1-6.

8. The graphene-supported metal monatomics material of claim 7, wherein, satisfies one or more of the following conditions: (1) the graphene-supported metal monatomic material has a porous structure; (2) the specific surface area of the graphene supported metal monatomic material is 100 m 2 / g to 1000 m 2 / g; (3) the porosity of the graphene-supported metal monatomic material is 25%-55%; (4) the loading amount of metal monatomic in the graphene-supported metal monatomic material is 1wt%-10wt%; and (5) the content of metal clusters in the graphene-supported metal monatomic material is less than 0.1wt%.

9. Use of the graphene-supported metal monatomic material according to claim 7 or 8 as a catalyst.

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