Microwave preparation and use of single-metal-atom-doped reduced graphene oxide dielectric material

Abstract

The present invention relates to the technical field of dielectric materials, and specifically relates to the microwave preparation and use of a single-metal-atom-doped reduced graphene oxide dielectric material. The preparation of the present invention comprises: adding an aqueous solution of a metal salt to an aqueous dispersion of graphene oxide to obtain a mixed solution, mechanically stirring same to enable the metal salt and the graphene oxide to sufficiently interact with each other, and uniformly loading metal ions in the mixed solution onto the surfaces of lamellas of the graphene oxide by means of the interaction between the metal ions and oxygen-containing functional groups of the graphene oxide; conducting freeze-drying, so as to obtain a metal salt / graphene oxide compound; and placing the metal salt / graphene oxide compound in a microwave oven, adding an initiator, and performing a reduction reaction, so as to obtain a single-metal-atom-doped reduced graphene oxide dielectric material. In the present invention, a solid-phase microwave reduction process is used, and the reduction effect can be effectively controlled without the generation of industrial waste liquid; therefore, the process is more environmentally friendly, and the product is purer.

Description

Microwave preparation and application of metal single atom doped reduced graphene oxide dielectric materials Technical Field

[0001] The present invention relates to the technical field of dielectric materials, and in particular to microwave preparation and application of metal single atom doped reduced graphene oxide dielectric materials. Background Art

[0002] When an applied electric field primarily causes the displacement of positive and negative charges rather than their directional movement, the material is said to be polarized. Materials characterized by polarization are called dielectric materials. Polarization within a dielectric is essentially the separation of positive and negative charges, so the dielectric constant and dielectric loss (tan δ) are two of the primary indicators for evaluating a material's dielectric properties.

[0003] As an industrially produced, low-cost two-dimensional nanoparticle, graphene oxide (GO) has been widely used in many fields in recent years. Compared with graphene nanosheets (GNPs), GO has a rich surface of oxygen-containing functional groups. When these oxygen-containing functional groups are modified, various functionalized GO can be obtained. Therefore, the application field of GO is even wider. In addition, GO can be transformed into reduced graphene oxide (rGO) with excellent conductive properties under reducing agents or heat treatment conditions, so that it can be used as a current collector in the field of microelectronics. Researchers usually prepare GO with other nanoparticles into hybrid materials to achieve different functional uses. At present, nanoparticles that can form hybrid materials with GO mainly include metals, metal oxides, inorganic ceramics and carbon materials. The hybrid nanoparticles formed are usually used in many fields such as electrochemical sensing, catalysts, fuel cells and polymer functional composite materials.

[0004] To prepare metal single-atom-doped reduced graphene oxide, researchers at home and abroad have explored a variety of methods, including hydrothermal methods, impregnation-assisted high-temperature pyrolysis methods, chemical vapor deposition epitaxy simultaneous doping methods, and microwave-assisted synthesis. Microwave-assisted synthesis, which requires no additional reducing agents, is a greener process, produces purer products, and is carried out in a solid-state reaction, avoiding irreversible aggregation problems caused by the drying process of liquid-phase reaction systems. Furthermore, the rapid reaction time of microwave-assisted synthesis (within seconds or tens of seconds) effectively suppresses the occurrence of various side reactions, facilitating the preparation of industrial production requirements. However, there are currently no reports on the use of microwave-assisted methods to prepare metal single-atom-doped reduced graphene oxide dielectric materials. The introduction of metal single atoms into the graphene structure leads to local asymmetry within the two-dimensional structure, forming permanent dipoles, enhancing dielectric relaxation, improving the system's polarization properties, and improving multiple properties of graphene. Therefore, it can be widely used in supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, electromagnetic wave absorption, and other fields.

[0005] Summary of the Invention

[0006] In order to solve the problems that the conventional liquid phase preparation process of metal single atom doped reduced graphene oxide easily leads to irreversible agglomeration during the drying process, and the filling amount is large when it is used as a functional filler, resulting in poor performance of the composite material and limiting the actual application effect, the present invention provides a microwave preparation and application of metal single atom doped reduced graphene oxide dielectric material.

[0007] The present invention is achieved through the following technical solution: a microwave preparation of a metal single atom doped reduced graphene oxide dielectric material, comprising the following steps:

[0008] (1) adding deionized water to the graphene oxide slurry and dispersing it for a certain time at a certain ultrasonic power to obtain a graphene oxide aqueous dispersion of a set concentration;

[0009] (2) adding deionized water to the metal salt powder and dissolving it to obtain a metal salt aqueous solution of a set concentration;

[0010] (3) adding the metal salt aqueous solution of the set concentration prepared in step (2) to the graphene oxide aqueous dispersion of the set concentration prepared in step (1) to obtain a mixed solution, and mechanically stirring the solution at a certain speed for a certain time to allow the metal salt and the graphene oxide to fully interact with each other, and utilizing the interaction between the metal ions and the oxygen-containing functional groups of the graphene oxide to uniformly load the metal ions in the mixed solution on the surface of the graphene oxide sheet;

[0011] (4) freeze-drying the mixed solution obtained in step (3) to obtain a metal salt / graphene oxide composite;

[0012] (5) placing the metal salt / graphene oxide composite obtained in step (4) in a microwave oven, adding a certain mass of initiator, and causing the metal salt and graphene oxide in the composite to undergo reduction reactions simultaneously under different microwave powers, and obtaining a metal single atom-doped reduced graphene oxide dielectric material after a certain period of time.

[0013] As a further improvement of the technical solution of the present invention, in step (1), the ultrasonic power is 100-300 W, the ultrasonic dispersion time is 10-30 min; and the set concentration of the graphene oxide aqueous dispersion is 1-3 mg / mL.

[0014] As a further improvement of the technical solution of the present invention, in step (2), the metal salt is a mixture obtained by mixing one or more metal salts of iron, cobalt, and nickel in any proportion, and the set concentration of the metal salt aqueous solution is 0.02 to 0.20 mg / mL.

[0015] As a further improvement of the technical solution of the present invention, in step (3), the rotation speed of the mechanical stirring is 100 to 300 r / min, and the stirring time is 20 to 40 min.

[0016] As a further improvement of the technical solution of the present invention, in step (4), the temperature for freeze-drying the mixed solution is -40 to -10°C, and the freeze-drying time is 24 to 72 hours.

[0017] As a further improvement of the technical solution of the present invention, in step (5), the added initiator is chopped carbon fiber bundles, graphite powder or copper wire, and the added amount is 1 wt.% of the mass of the metal salt / graphene oxide composite.

[0018] As a further improvement of the technical solution of the present invention, in step (5), the microwave power is 100 to 700 W, and the reduction reaction time is 4 to 14 s.

[0019] The present invention also provides the application of the metal single atom doped reduced graphene oxide dielectric material obtained by microwave preparation of the metal single atom doped reduced graphene oxide dielectric material in the field of dielectric materials.

[0020] As a further improvement of the application technical solution of the present invention, the dielectric material field includes supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials.

[0021] As a further improvement of the application technical solution of the present invention, when the metal single atom doped reduced graphene oxide dielectric material is used as an electromagnetic wave absorbing material, its filling amount in the matrix does not exceed 1 wt.%.

[0022] The microwave preparation and application of the metal single atom doped reduced graphene oxide dielectric material provided by the present invention have the following advantages over the prior art:

[0023] (1) The microwave reduction reaction of the present invention is carried out completely in solid phase, which can effectively avoid the problems of irreversible agglomeration caused by the drying process of conventional liquid phase reduction process.

[0024] (2) Conventional liquid-phase reduction processes require the use of various chemical reducing agents, which not only significantly increases costs and significantly prolongs production cycles, but also worsens the production environment. In particular, the treatment and discharge of metal salt wastewater after use can cause serious environmental pollution. The present invention uses a solid-phase microwave reduction process, which effectively controls the reduction effect without generating industrial wastewater. Therefore, the process is more environmentally friendly and the product is purer.

[0025] (3) The present invention utilizes a one-step microwave reduction reaction to simultaneously achieve the reduction of graphene oxide, the reduction of metal ions, and the embedding of metal atoms generated by the reduction of metal ions into the reduced graphene oxide lattice; in addition, the reduced graphene oxide will continue to transfer heat energy to reduce the adjacent metal salt / graphene oxide complex until the reaction is completed, and the entire reduction process is very rapid.

[0026] (4) The microwave reduction process of the present invention has the advantages of being convenient and fast, lasting only a few seconds to more than ten seconds. While saving energy, it can also effectively inhibit the occurrence of various side reactions during conventional high-temperature reduction processes, and can meet the needs of industrial large-scale production of products with stable structural performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 is an XRD spectrum of the Fe single atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention, the Fe sub-nanocluster doped reduced graphene oxide dielectric material prepared in Comparative Example 1, the Fe nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2, and the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0030] FIG2 is a transmission electron microscope (TEM) photograph of the Fe single atom-doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention.

[0031] Figure 3 is a real part curve of the dielectric constants of the Fe single atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention, the Fe sub-nanocluster doped reduced graphene oxide dielectric material prepared in Comparative Example 1, the Fe nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2, and the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0032] Figure 4 is the imaginary part curve of the dielectric constants of the Fe single atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention, the Fe sub-nanocluster doped reduced graphene oxide dielectric material prepared in Comparative Example 1, the Fe nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2, and the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0033] FIG5 is a graph showing the real part of the magnetic permeability of the Fe single-atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention.

[0034] FIG6 is a graph showing the real part of the magnetic permeability of the Fe sub-nano cluster-doped reduced graphene oxide dielectric material prepared in Comparative Example 1.

[0035] FIG7 is a graph showing the real part of the magnetic permeability of the Fe-containing nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2.

[0036] FIG8 is a graph showing the real part of the magnetic permeability of the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0037] FIG9 is a graph showing the imaginary part of the magnetic permeability of the Fe single-atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention.

[0038] Figure 10 is a graph showing the imaginary part of the magnetic permeability of the Fe sub-nano cluster-doped reduced graphene oxide dielectric material prepared in Comparative Example 1.

[0039] Figure 11 is a graph showing the imaginary part of the magnetic permeability of the Fe-containing nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2.

[0040] Figure 12 is a graph showing the imaginary part of the magnetic permeability of the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0041] Figure 13 is a comparison of the dielectric loss curves of the Fe single atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention, the Fe sub-nanocluster doped reduced graphene oxide dielectric material prepared in Comparative Example 1, the Fe nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2, and the microwave reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0042] FIG14 is a magnetic loss curve of the Fe single atom-doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention.

[0043] Figure 15 is a magnetic loss curve of the Fe sub-nano cluster doped reduced graphene oxide dielectric material prepared in Comparative Example 1.

[0044] Figure 16 is a magnetic loss curve of the Fe-containing nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2.

[0045] Figure 17 is a magnetic loss curve of the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3.

[0046] Figure 18 is a comparison curve of the electromagnetic wave absorption performance (reflection loss) of the Fe single atom doped reduced graphene oxide dielectric material prepared in Example 1 of the present invention, the Fe sub-nanocluster doped reduced graphene oxide dielectric material prepared in Comparative Example 1, the Fe nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2, and the microwave reduced graphene oxide dielectric material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0047] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0048] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0049] The present invention provides a specific embodiment of microwave preparation of metal single atom doped reduced graphene oxide dielectric material, comprising the following steps:

[0050] (1) adding deionized water to the graphene oxide slurry and dispersing it for a certain time at a certain ultrasonic power to obtain a graphene oxide aqueous dispersion of a set concentration;

[0051] (2) adding deionized water to the metal salt powder and dissolving it to obtain a metal salt aqueous solution of a set concentration;

[0052] (3) adding the metal salt aqueous solution of the set concentration prepared in step (2) to the graphene oxide aqueous dispersion of the set concentration prepared in step (1) to obtain a mixed solution, and mechanically stirring the solution at a certain speed for a certain time to allow the metal salt and the graphene oxide to fully interact with each other, and utilizing the interaction between the metal ions and the oxygen-containing functional groups of the graphene oxide to uniformly load the metal ions in the mixed solution on the surface of the graphene oxide sheet;

[0053] (4) freeze-drying the mixed solution obtained in step (3) to obtain a metal salt / graphene oxide composite;

[0054] (5) placing the metal salt / graphene oxide composite obtained in step (4) in a microwave oven, adding a certain mass of initiator, and causing the metal salt and graphene oxide in the composite to undergo reduction reactions simultaneously under different microwave powers, and obtaining a metal single atom-doped reduced graphene oxide dielectric material after a certain period of time.

[0055] In the present invention, microwave reduction refers to a process in which microwave energy is converted into thermal energy by a material that can effectively absorb microwaves to achieve a reduction reaction. Since the dispersed graphite domains on the sheet are surrounded by large and disordered continuous oxidation regions, graphene oxide is insulating and cannot effectively absorb microwaves, and an initiator with good conductivity needs to be added. During the microwave reduction process, the initiator absorbs microwaves to induce electron flow and ionize the surrounding atmosphere. The absorbed microwaves are effectively converted into thermal energy through Joule heating, causing the temperature of the initiator and the metal salt / graphene oxide complex in its vicinity to rise sharply instantly, thereby achieving the reduction of graphene oxide, the reduction of metal ions, and the embedding of metal atoms generated by the reduction of metal ions in the reduced graphene oxide lattice in a one-step process; in addition, the reduced graphene oxide can continue to transfer thermal energy to reduce the adjacent metal salt / graphene oxide complex until the reduction reaction ends, and the entire reduction process is very rapid.

[0056] In one embodiment provided by the present invention, in step (1), the ultrasonic power is 100-300 W, the ultrasonic dispersion time is 10-30 min; and the set concentration of the graphene oxide aqueous dispersion is 1-3 mg / mL.

[0057] In another embodiment provided by the present invention, in step (2), the metal salt is a mixture obtained by mixing one or more metal salts of iron, cobalt, and nickel in any proportion, and the set concentration of the metal salt aqueous solution is 0.02-0.20 mg / mL.

[0058] In one embodiment provided by the present invention, in step (3), the rotation speed of the mechanical stirring is 100 to 300 r / min, and the stirring time is 20 to 40 min.

[0059] In another embodiment provided by the present invention, in step (4), the temperature for freeze-drying the mixed solution is -40 to -10°C, and the freeze-drying time is 24 to 72 hours.

[0060] In one embodiment of the present invention, in step (5), the added initiator is chopped carbon fiber bundles, graphite powder, or copper wire, and the added amount is 1 wt.% of the mass of the metal salt / graphene oxide composite. Specifically, the chopped carbon fiber bundles are conventional commercial chopped carbon fiber bundles with a length of 4-10 mm; the graphite powder is conventional commercial graphite powder with a mesh size of 325; and the copper wire is conventional commercial copper wire with a diameter of 0.15 mm and a length of 4-10 mm. The initiators used in the following embodiments of the present invention have the same parameters.

[0061] In another embodiment provided by the present invention, in step (5), the microwave power is 100-700 W, and the reduction reaction time is 4-14 s.

[0062] The present invention also provides the application of the metal single atom doped reduced graphene oxide dielectric material obtained by microwave preparation of the metal single atom doped reduced graphene oxide dielectric material in the field of dielectric materials.

[0063] In one embodiment provided by the present invention, the dielectric material field includes supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials.

[0064] In another embodiment provided by the present invention, when the metal single atom doped reduced graphene oxide dielectric material is used as the electromagnetic wave absorbing material, its filling amount in the matrix does not exceed 1 wt.%.

[0065] The performance test standards used in the embodiments of the present invention are as follows:

[0066] (1) X-ray diffraction (XRD) test: The sample was placed in a test mold, flattened, and covered with a glass slide, and tested using an X-ray diffractometer 2700BX (Haoyuan, China).

[0067] (2) Resistivity test: A 7.00 mm diameter disc was prepared by uniformly mixing 1 wt.% sample with 99 wt.% paraffin wax, and the test was performed using a four-probe resistivity tester RTS-9 (Four Probes Tech, China).

[0068] (3) Electromagnetic parameter test: A coaxial ring with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm was prepared using a uniform mixture of 1 wt.% sample and 99 wt.% paraffin wax. The dielectric constant and magnetic permeability of the sample were measured in the range of 2 to 18 GHz using a vector network analyzer 3672C (Ceyear, China) by the coaxial reflection / transmission method. The dielectric loss and magnetic loss were calculated. The electromagnetic wave absorption performance of the sample in the range of 2 to 18 GHz was calculated using the transmission line theory.

[0069] (4) TEM test: The test was performed using a field emission transmission electron microscope Talos F200S (Thermo Scientific, USA).

[0070] The specific embodiments of the present invention are described in detail below.

[0071] Example 1

[0072] A microwave preparation method for a Fe single-atom doped reduced graphene oxide dielectric material comprises the following steps:

[0073] (1) Deionized water was added to a 1 wt.% graphene oxide slurry, and the mixture was dispersed under an ultrasonic power of 200 W for 15 min to obtain a graphene oxide aqueous dispersion with a concentration of 3 mg / mL;

[0074] (2) adding deionized water to the ferric sulfate powder and fully dissolving it to obtain an aqueous solution of ferric sulfate with a concentration of 0.056 mg / mL;

[0075] (3) adding the ferric sulfate aqueous solution prepared in step (2) to the graphene oxide aqueous dispersion prepared in step (1) to obtain a mixed solution, and mechanically stirring at a speed of 100 r / min for 30 min to allow the ferric sulfate and graphene oxide to fully interact;

[0076] (4) freeze-drying the uniform mixed solution prepared in step (3) at a temperature of -40°C for 24 hours to obtain an iron sulfate / graphene oxide composite;

[0077] (5) The iron sulfate / graphene oxide composite obtained in step (4) is placed in a microwave oven, and after adding 1 wt.% of an initiator 6 mm short-cut carbon fiber bundle, the iron sulfate / graphene oxide composite is reduced for 10 s at a microwave power of 350 W to obtain an Fe single atom-doped reduced graphene oxide dielectric material.

[0078] The obtained Fe single atom doped reduced graphene oxide was characterized by XRD, and its microstructure was characterized by TEM.

[0079] Comparative Example 1

[0080] A microwave preparation method for a Fe sub-nano cluster doped reduced graphene oxide dielectric material comprises the following steps:

[0081] (1) Deionized water was added to a 1 wt.% graphene oxide slurry, and the mixture was dispersed under an ultrasonic power of 200 W for 15 min to obtain a graphene oxide aqueous dispersion with a concentration of 3 mg / mL;

[0082] (2) adding deionized water to the ferric sulfate powder and fully dissolving it to obtain an aqueous solution of ferric sulfate with a concentration of 0.3 mg / mL;

[0083] (3) adding the ferric sulfate aqueous solution prepared in step (2) to the graphene oxide aqueous dispersion prepared in step (1) to obtain a mixed solution, and mechanically stirring at a speed of 100 r / min for 30 min to allow the ferric sulfate and graphene oxide to fully interact;

[0084] (4) freeze-drying the uniform mixed solution prepared in step (3) at a temperature of -40°C for 24 hours to obtain an iron sulfate / graphene oxide composite;

[0085] (5) The iron sulfate / graphene oxide composite obtained in step (4) is placed in a microwave oven, and after adding 1 wt.% of an initiator 6 mm short-cut carbon fiber bundle, the iron sulfate / graphene oxide composite is reduced for 10 s at a microwave power of 350 W to obtain a Fe sub-nano cluster-doped reduced graphene oxide dielectric material.

[0086] Comparative Example 2

[0087] A microwave preparation method for a dielectric material containing Fe nanoparticles loaded with reduced graphene oxide comprises the following steps:

[0088] (1) Deionized water was added to a 1 wt.% graphene oxide slurry, and the mixture was dispersed under an ultrasonic power of 200 W for 15 min to obtain a graphene oxide aqueous dispersion with a concentration of 3 mg / mL;

[0089] (2) adding deionized water to the ferric sulfate powder and fully dissolving it to obtain an aqueous solution of ferric sulfate with a concentration of 1 mg / mL;

[0090] (3) adding the ferric sulfate aqueous solution prepared in step (2) to the graphene oxide aqueous dispersion prepared in step (1) to obtain a mixed solution, and mechanically stirring at a speed of 100 r / min for 30 min to allow the ferric sulfate and graphene oxide to fully interact;

[0091] (4) freeze-drying the uniform mixed solution prepared in step (3) at a temperature of -40°C for 24 hours to obtain an iron sulfate / graphene oxide composite;

[0092] (5) The iron sulfate / graphene oxide composite obtained in step (4) is placed in a microwave oven, and after adding 1 wt.% of an initiator 6 mm short-cut carbon fiber bundle, the iron sulfate / graphene oxide composite is reduced for 10 s at a microwave power of 350 W to obtain a Fe-containing nanoparticle-loaded reduced graphene oxide dielectric material.

[0093] Comparative Example 3

[0094] The preparation of microwave-reduced graphene oxide dielectric material comprises the following steps:

[0095] (1) Deionized water was added to a 1 wt.% graphene oxide slurry, and the mixture was dispersed under an ultrasonic power of 200 W for 15 min to obtain a graphene oxide aqueous dispersion with a concentration of 3 mg / mL;

[0096] (2) freeze-drying the graphene oxide aqueous dispersion obtained in step (1) at a temperature of -40°C for 24 hours to obtain graphene oxide floccules;

[0097] (3) The graphene oxide flocs obtained in step (2) were placed in a microwave oven, 1 wt.% of an initiator 6 mm short-cut carbon fiber bundle was added, and the graphene oxide was reduced for 10 s at a microwave power of 350 W to obtain a microwave-reduced graphene oxide dielectric material.

[0098] Comparative Example 4

[0099] The preparation process is exactly the same as that of Comparative Example 3, except that the concentration of the GO dispersion in step (1) is 1 mg / mL.

[0100] Comparative Example 5

[0101] The preparation process is the same as that of Comparative Example 3, except that the microwave power in step (3) is 700W.

[0102] Comparative Example 6

[0103] The preparation process is the same as that of Comparative Example 3, except that the microwave power in step (3) is 100 W.

[0104] Comparative Example 7

[0105] The preparation process is the same as that of Comparative Example 3, except that the microwave reaction time in step (3) is 4 s.

[0106] Comparative Example 8

[0107] The preparation process was the same as that of Comparative Example 3, except that the microwave reaction time in step (3) was 14 s.

[0108] Figure 1 shows that compared with the XRD spectra of unreduced graphene oxide (i.e., graphene oxide slurry), the (002) diffraction peak at 10.58° belonging to graphene oxide for the Fe single atom-doped reduced graphene oxide dielectric material prepared in Example 1, the Fe sub-nanocluster-doped reduced graphene oxide dielectric material prepared in Comparative Example 1, the Fe nanoparticle-loaded reduced graphene oxide dielectric material prepared in Comparative Example 2, and the microwave-reduced graphene oxide dielectric material prepared in Comparative Example 3 all disappear, indicating that the oxygen-containing functional groups in these materials are effectively reduced; the diffraction peak at 20.5° (2θ) represents amorphous carbon, and the diffraction peak at 26° (2θ) is generated by the interlayer stacking of graphite-like structure crystal planes. Different Fe forms will affect the interlayer stacking of reduced graphene oxide. In addition, no diffraction peaks of Fe crystals appear in the spectra of Example 1 and Comparative Example 1, indicating that Fe is not aggregated into nanoparticles (clusters are relatively stable microscopic or submicroscopic aggregates composed of several or even thousands of atoms, molecules or ions through physical or chemical binding forces, and their physical and chemical properties vary with the number of atoms contained. The spatial scale of clusters ranges from a few angstroms to hundreds of angstroms, and many properties are different from those of single atoms and molecules, solids and liquids, and cannot be obtained by simple linear extension or interpolation of the properties of the two. Therefore, clusters are regarded as a new level of material structure between atoms, molecules and macroscopic solid substances. The properties of clusters may be very different from those of single atoms or molecules. Metal clusters have different properties from single atoms and nanoparticles. The properties of the clusters are very different, and these properties may be related to the size, shape and structure of the clusters. Subnanoclusters refer to tiny clusters composed of several atoms or molecules with a size at the subnanometer level. The size of subnanoclusters is usually between 1 and 10 nanometers. Agglomerates are aggregates formed by primary particles or aggregates connected to each other by edges or corners. Its specific surface area is not significantly different from the sum of the specific surfaces of the particles or aggregates that make it up. The process of forming agglomerates is called agglomeration. Our subnanoclusters are a special state that requires precise experimental control. The performance results of the samples are also good, which is different from conventional agglomerate systems. ), Comparative Example 2 has a new diffraction peak at 2θ of 35.3°, corresponding to the (311) crystal plane of Fe3O4 nanoparticles (PDF standard card ICDD 01-089-0688), indicating the formation of Fe-containing nanoparticles.

[0109] The resistivity of the Fe single atom-doped reduced graphene oxide prepared in Example 1 was tested by a four-probe resistivity tester and was found to be 9.11×10-2Ω·m, which was 83% lower than the 5.26×10-1Ω·m of the Fe sub-nano cluster-doped reduced graphene oxide prepared in Comparative Example 1, 97% lower than the 2.97Ω·m of the Fe nanoparticle-loaded reduced graphene oxide prepared in Comparative Example 2, and 1476% higher than the 5.78×10-3Ω·m of the microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 3. The material can be applied in the fields of supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials.

[0110] The TEM dark field morphology of the Fe single atom-doped reduced graphene oxide dielectric material prepared in Example 1 in Figure 2 shows that the bright spot (Fe) particle size is less than 1 nm, which is at the single-atom level, indicating that the material prepared in Example 1 is indeed a metal single-atom-doped reduced graphene oxide dielectric material.

[0111] Figure 3-17 shows the dielectric constant, magnetic permeability, and calculated dielectric loss and magnetic loss of paraffin composite materials filled with modified graphene functional particles with the same filling amount within 2 to 18 GHz, obtained by vector network analyzer testing. It can be seen that the dielectric constant of the Fe single atom doped reduced graphene oxide / paraffin composite material prepared in Example 1 is significantly different from the dielectric constant of the Fe sub-nano cluster doped reduced graphene oxide / paraffin composite material prepared in Comparative Example 1, the dielectric constant of the Fe nanoparticle-loaded reduced graphene oxide / paraffin composite material prepared in Comparative Example 2, and the dielectric constant of the microwave reduced graphene oxide / paraffin composite material prepared in Comparative Example 3. The real part of the dielectric constant in the low frequency range is significantly improved, the imaginary part of the dielectric constant in the full frequency range (2 to 18 GHz) is significantly increased, and the dielectric loss in the full frequency range is significantly improved; the change trend of the magnetic permeability of the Fe single atom doped reduced graphene oxide / paraffin composite material prepared in Example 1 is not significantly different from that of the paraffin composite materials corresponding to Comparative Examples 1-3, indicating that the effect of the change in magnetic loss on the electromagnetic wave absorption performance of the materials prepared in Example 1 and Comparative Examples 1-3 is negligible.

[0112] Figure 18 shows the electromagnetic wave absorption performance of paraffin wax composites filled with modified graphene functional particles at the same loading level, calculated using transmission line theory, within the 2-18 GHz range. As can be seen, the Fe single-atom-doped reduced graphene oxide dielectric material prepared in Example 1, with a loading level of only 1 wt.%, has a maximum effective absorption bandwidth of 6.46 GHz. This is a 19%, 31%, and 70% improvement over the 5.44 GHz of the Fe sub-nano cluster-doped reduced graphene oxide / paraffin wax composite prepared in Comparative Example 1, the 4.92 GHz of the Fe nanoparticle-loaded reduced graphene oxide / paraffin wax composite prepared in Comparative Example 2, and the 3.80 GHz of the microwave-reduced graphene oxide / paraffin wax composite prepared in Comparative Example 3, respectively.

[0113] Example 2

[0114] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the concentration of the GO dispersion in step (1) is 1 mg / mL.

[0115] The resulting Fe-single-atom-doped reduced graphene oxide dielectric material exhibits a resistivity of 8.56×10⁻²Ω·m, a 1336% increase compared to the 5.96×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 4. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt% Fe-doped composite material, exhibits a maximum effective absorption bandwidth of 5.66 GHz, a 61% increase compared to the 3.52 GHz of the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 4 with the same loading.

[0116] Example 3

[0117] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the concentration of the ferric sulfate aqueous solution prepared in step (2) is 0.028 mg / mL.

[0118] The resulting Fe-single-atom-doped reduced graphene oxide absorber material has a resistivity of 9.91×10⁻²Ω·m, a 1615% increase compared to the 5.78×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 3. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt% Fe-single-atom loading, exhibited a maximum effective absorption bandwidth of 4.92 GHz, a 30% increase compared to the 3.80 GHz achieved by the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 3 with the same loading.

[0119] Example 4

[0120] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the concentration of the ferric sulfate aqueous solution prepared in step (2) is 0.13 mg / mL.

[0121] The resulting Fe-single-atom-doped reduced graphene oxide dielectric material exhibits a resistivity of 4.80×10⁻²Ω·m, a 730% increase compared to the 5.78×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 3. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, nanoelectronic devices, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt% Fe-single-atom loading, exhibits a maximum effective absorption bandwidth of 4.68 GHz, a 23% increase compared to the 3.80 GHz of the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 3 with the same loading.

[0122] Example 5

[0123] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the microwave power in step (5) is 700W.

[0124] The resulting Fe-single-atom-doped reduced graphene oxide dielectric material exhibits a resistivity of 6.49×10⁻²Ω·m, an 1855% increase compared to the 3.32×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 5. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, nanoelectronic devices, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt% Fe-doped composite material, exhibits a maximum effective absorption bandwidth of 5.90 GHz, a 64% increase compared to the 3.60 GHz of the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 5 with the same loading.

[0125] Example 6

[0126] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the microwave power in step (5) is 100 W.

[0127] The resulting Fe-single-atom-doped reduced graphene oxide dielectric material exhibits a resistivity of 3.64×10⁻²Ω·m, a 276% increase compared to the 9.67×10⁻³Ω·m of microwave-reduced graphene oxide prepared using the same reduction process in Comparative Example 6. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, nanoelectronic devices, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt% Fe-doped composite material, exhibits a maximum effective absorption bandwidth of 3.19 GHz, a 10% increase compared to the 2.90 GHz of the microwave-reduced graphene oxide composite material prepared using the same reduction process in Comparative Example 6.

[0128] Example 7

[0129] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the microwave reaction time in step (5) is 4 s.

[0130] The resulting Fe-single-atom-doped reduced graphene oxide dielectric material has a resistivity of 1.26×10⁻¹Ω·m, a 2014% increase compared to the 5.96×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 7. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, nanoelectronic devices, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a filling content of only 1wt.%, achieved a maximum effective absorption bandwidth of 5.93GHz, a 67% increase compared to the 3.55GHz of a microwave-reduced graphene oxide composite material prepared by the same process and with the same filling content.

[0131] Example 8

[0132] A microwave preparation of a Fe single atom-doped reduced graphene oxide dielectric material, the process of which is exactly the same as that of Example 1, except that the microwave reaction time in step (5) is 14 s.

[0133] The resulting Fe-single-atom-doped reduced graphene oxide dielectric material exhibited a resistivity of 8.20×10⁻³Ω·m, a 276% increase compared to the 2.18×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 8. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, nanoelectronic devices, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt.% Fe-doped composite material, achieved a maximum effective absorption bandwidth of 4.54 GHz, a 62% increase compared to the 2.80 GHz of the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 8 with the same loading.

[0134] Example 9

[0135] A microwave preparation method for a Co single-atom doped reduced graphene oxide dielectric material is described, wherein the process is identical to that of Example 1, except that the metal salt powder in step (2) is cobalt sulfate.

[0136] The resulting Co single-atom-doped reduced graphene oxide dielectric material has a resistivity of 9.68×10⁻²Ω·m, a 1575% increase compared to the 5.78×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 3. The material has applications in supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt% Co loading, exhibited a maximum effective absorption bandwidth of 6.22GHz, a 64% increase compared to the 3.80GHz of the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 3 with the same loading.

[0137] Example 10

[0138] A microwave preparation method for a Ni single-atom doped reduced graphene oxide dielectric material is described, wherein the process is identical to that of Example 1, except that the metal salt powder in step (2) is nickel sulfate.

[0139] The resulting Ni single-atom-doped reduced graphene oxide dielectric material has a resistivity of 9.96×10⁻²Ω·m, a 1623% increase compared to the 5.78×10⁻³Ω·m of microwave-reduced graphene oxide prepared by the same reduction process in Comparative Example 3. The material is suitable for applications in supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials. When used in electromagnetic wave absorption materials, the composite material, with a 1wt.% Ni loading, exhibited a maximum effective absorption bandwidth of 6.06 GHz, a 59% increase compared to the 3.80 GHz achieved by the microwave-reduced graphene oxide composite material prepared by the same reduction process in Comparative Example 3 with the same loading.

[0140] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. A microwave preparation of metal single atom doped reduced graphene oxide dielectric material, characterized in that: The steps include: (1) adding deionized water to the graphene oxide slurry, dispersing for a certain period of time under a certain ultrasonic power, and obtaining a graphene oxide aqueous dispersion of a set concentration; (2) adding deionized water to the metal salt powder to dissolve it to obtain a metal salt aqueous solution of a set concentration; (3) adding the metal salt aqueous solution of a set concentration prepared in step (2) to the graphene oxide aqueous dispersion of a set concentration prepared in step (1) to obtain a mixed solution, and mechanically stirring the solution at a certain speed for a certain period of time to allow the metal salt and the graphene oxide to fully interact with each other, and utilizing the interaction between the metal ions and the oxygen-containing functional groups of the graphene oxide to uniformly load the metal ions in the mixed solution on the surface of the graphene oxide sheet; (4) freeze-drying the mixed solution obtained in step (3) to obtain a metal salt / graphene oxide composite; (5) placing the metal salt / graphene oxide composite obtained in step (4) in a microwave oven, adding a certain mass of initiator, and causing the metal salt and graphene oxide in the composite to undergo reduction reactions simultaneously under different microwave powers, and obtaining a metal single atom-doped reduced graphene oxide dielectric material after a certain period of time.

2. The microwave preparation of a metal single atom doped reduced graphene oxide dielectric material according to claim 1, characterized in that: In step (1), the ultrasonic power is 100-300 W, the ultrasonic dispersion time is 10-30 min; and the set concentration of the graphene oxide aqueous dispersion is 1-3 mg / mL.

3. The microwave preparation of a metal single atom doped reduced graphene oxide dielectric material according to claim 1, characterized in that: In step (2), the metal salt is a mixture of one or more metal salts of iron, cobalt and nickel mixed in any proportion, and the set concentration of the metal salt aqueous solution is 0.02 to 0.20 mg / mL.

4. The microwave preparation of a metal single atom doped reduced graphene oxide dielectric material according to claim 1, characterized in that: In step (3), the rotation speed of the mechanical stirring is 100 to 300 r / min, and the stirring time is 20 to 40 min.

5. The microwave preparation of a metal single atom doped reduced graphene oxide dielectric material according to claim 1, characterized in that: In step (4), the temperature of freeze-drying the mixed solution is -40 to -10°C, and the freeze-drying time is 24 to 72 hours.

6. The microwave preparation of a metal single atom doped reduced graphene oxide dielectric material according to claim 1, characterized in that: In step (5), the added initiator is chopped carbon fiber bundles, graphite powder or copper wire, and the added amount is 1wt.% of the mass of the metal salt / graphene oxide composite.

7. The microwave preparation of metal single atom doped reduced graphene oxide dielectric material according to claim 1, characterized in that: In step (5), the microwave power is 100 to 700 W, and the reduction reaction time is 4 to 14 s.

8. Application of the metal single atom doped reduced graphene oxide dielectric material prepared by microwave of the metal single atom doped reduced graphene oxide dielectric material according to any one of claims 1 to 7 in the field of dielectric materials.

9. The use according to claim 8, characterized in that The dielectric material field includes supercapacitors, hydrogen storage materials, batteries, transistors, biosensors, and electromagnetic wave absorption materials.

10. The use according to claim 9, characterized in that: When the metal single atom doped reduced graphene oxide dielectric material is used as an electromagnetic wave absorbing material, its filling amount in the matrix does not exceed 1 wt.%.

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