Production of high-quality graphene from solid carbon sources

Abstract

The present invention relates generally to systems and methods for producing high quality graphene from solid carbon sources.

Description

[Technical field]

[0001] The present invention relates to the production of high quality graphene from solid carbon sources. [Background technology]

[0002] 2. Background of the Invention Graphene is one of the most promising materials in nanotechnology. Due to its high atomic lattice perfection, graphene samples have exceptional mechanical, thermal, and electrical properties, but structural defects that can appear during growth or processing degrade the performance of graphene-based devices. What is needed in the field are improved methods to produce high-quality graphene. Summary of the Invention [Means for solving the problem]

[0003] The present invention relates to methods for producing and using high purity graphene.

[0004] In an embodiment, the present invention provides a method of producing graphene comprising: a) providing a high purity solid carbon source; and b) applying a voltage pulse across the solid carbon source to convert the solid carbon source to graphene.

[0005] In an embodiment, the invention provides a method of producing graphene comprising: a) providing a high purity solid carbon source, wherein the solid carbon source is greater than 99.99% (w / w) elemental carbon; and b) applying a voltage pulse across the solid carbon source to convert the solid carbon source to graphene, wherein the graphene contains less than 200 ppm extrinsic defects.

[0006] In some embodiments, the solid carbon source is greater than 99.995% (w / w) elemental carbon. In some embodiments, the solid carbon source is greater than 99.999% (w / w) elemental carbon. In some embodiments, the solid carbon source is greater than 99.9995% (w / w) elemental carbon. In some embodiments, the solid carbon source is greater than 99.9999% (w / w) elemental carbon.

[0007] In some embodiments, the graphene contains less than 100 ppm extrinsic defects. In some embodiments, the graphene contains less than 50 ppm extrinsic defects. In some embodiments, the graphene contains less than 25 ppm extrinsic defects. In some embodiments, the graphene contains less than 10 ppm extrinsic defects. In some embodiments, the graphene contains less than 5 ppm extrinsic defects. In some embodiments, the graphene contains less than 1 ppm extrinsic defects.

[0008] In some embodiments, extrinsic defects are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), ICP mass spectrometry (ICP-MS), proton induced X-ray emission, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), oxidative combustion, and / or thermogravimetric analysis.

[0009] In some embodiments, the extrinsic defects are oxygen, hi some embodiments, the graphene comprises less than 200 ppm oxygen.

[0010] In some embodiments, the graphene contains less than 0.01 ppm of intrinsic defects. In some embodiments, the intrinsic defects are non-sp 2 In some embodiments, the graphene contains less than 0.01% sp 3 In some embodiments, the percent sp of graphene 2 is at least 95%.

[0011] In some embodiments, the graphene has an I(D) / I(G) ratio of less than 0.2 as measured by Raman spectroscopy. In some embodiments, the graphene has an I(2D) / I(G) ratio of 0.5 to 2 as measured by Raman spectroscopy.

[0012] In some embodiments, the electrical conductivity of graphene is at least 10 4 In some embodiments, the specific surface area (SSA) of the graphene is greater than 1000 m 2 / g. In some embodiments, the graphene is a graphene flake, and the graphene flake has an average lateral size (D50) of at least 10 μm.

[0013] In some embodiments, the graphene is not purified after step b). In some embodiments, the extrinsic defects are not removed after step b). In some embodiments, the method further comprises the step of c) combining the graphene with a binder or dispersant without further purification.

[0014] In some embodiments, the solid carbon source comprises greater than 90% (w / w) amorphous carbon, hi some embodiments, the solid carbon source comprises greater than 90% (w / w) graphitic carbon.

[0015] In some embodiments, the solid carbon source is produced by reduction of carbon dioxide or carbon monoxide with hydrogen gas. In some embodiments, the solid carbon source is produced from carbon dioxide and hydrogen gas by the Bosch reaction. In some embodiments, hydrogen gas is provided in an amount greater than the stoichiometric ratio required for reduction of carbon dioxide or carbon monoxide. In some embodiments, the solid carbon source is produced from carbon monoxide by the Boudouard reaction. In some embodiments, the reaction includes a catalyst or catalyst precursor. In some embodiments, the reaction occurs at room temperature. In some embodiments, the reaction occurs at a temperature between 450° C. and 2000° C. In some embodiments, step b) is performed under atmospheric pressure.

[0016] In some embodiments, the method produces at least 1 gram of graphene. In some embodiments, the yield of graphene from the solid carbon source is at least 90%.

[0017] The invention further features a device that includes in combination: (a) a first component for providing a high purity solid carbon source by reducing carbon dioxide or carbon monoxide with hydrogen gas; and (b) a second component for applying a voltage pulse across the solid carbon to convert the solid carbon to graphene.

[0018] definition To facilitate understanding of the present invention, a number of terms are defined below and throughout this disclosure. 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 invention belongs. Terms in this specification are used to describe certain embodiments of the present invention, but their use does not limit the invention, except as outlined in the claims.

[0019] Terms such as "a," "an," and "the" are not intended to refer only to a singular entity, but include general classes for which specific examples can be used for illustration.

[0020] As used herein, the term "about" refers to a value within 10% above or below the stated value.

[0021] As used herein, the term "amorphous" refers to a material in which the constituent atoms, molecules, or ions are arranged randomly without any regular repeating pattern, such as, for example, amorphous carbon materials. Amorphous materials may have some degree of localized crystallinity (i.e., order), but lack long-range order in the positions of the atoms. Pyrolytic and / or activated carbon materials are generally amorphous.

[0022] As used herein, the term "defect" refers to a physical abnormality in a material compared to an ideal material, for example, a defect is a physical difference between as-prepared graphene and ideal graphene.

[0023] As used herein, the term "intrinsic defects" refers to defects in a material that result from carbon bonds. For example, intrinsic defects are described in Tian et al., Micromacines vol. 8, 5 163 (2017), which is incorporated herein by reference.

[0024] As used herein, the term "extrinsic defects" refers to defects in a material that result from the presence of foreign atoms, such as non-carbon atoms, in graphene. For example, extrinsic defects are described in Tian et al., Micromacines vol. 8, 5 163 (2017).

[0025] As used herein, "sp 2The term "hybridization" refers to a carbon atom that is directly bonded to three other carbon atoms and has a planar structure. For example, the sp 2 The hybridization is described in Kovtun et al., 2D Mater. 6, (2019).

[0026] As used herein, "sp 3 The term "hybridized" refers to a carbon atom that is bonded to four other atoms and has a tetrahedral structure. For example, the sp 3 The hybridization is described in Kovtun et al., 2D Mater. 6, (2019).

[0027] The following detailed description of the embodiments of the invention may be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently exemplary. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities of the embodiments shown in the drawings. [Brief description of the drawings]

[0028] [Figure 1A] FIG. 1A illustrates an embodiment of a chamber for producing solid carbon and / or graphene. [Figure 1B] FIG. 1B illustrates an embodiment of a chamber for producing solid carbon and / or graphene. [Figure 1C] FIG. 1C illustrates an embodiment of a chamber for producing solid carbon and / or graphene. [Figure 2A] FIG. 2A shows an embodiment of the catalyst. [Figure 2B] FIG. 2B shows an embodiment of the catalyst. [Diagram 3] FIG. 3 shows an embodiment of a gasket. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In the following description, various examples are presented with specific details to provide a thorough understanding of the claimed subject matter. However, it will be apparent to one of ordinary skill in the art that the subject matter of the present invention may be practiced without one or more of the specific details disclosed herein. Moreover, in some circumstances, well-known methods, procedures, systems, and / or components have not been described in detail to avoid unnecessarily obscuring the claimed subject matter. The exemplary embodiments described in the detailed description and claims are not intended to be limiting. Other embodiments may be utilized and other changes may be made without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that aspects of the present disclosure, as generally described herein, may be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are expressly contemplated and form part of this disclosure.

[0030] Without limiting the scope of the present invention, the present invention relates to the production of high purity graphene. In particular, the present disclosure provides a method for the efficient industrial-scale production of graphene from high purity solid carbon sources.

[0031] Graphene and defects in graphene Graphene is sp 2 It is a two-dimensional honeycomb-structured material formed by a single layer of hybrid orbital carbon atoms. The thickness of an ideal graphene single layer is about 0.335 nm, which corresponds to the thickness of one carbon atom. Graphene, which has a two-dimensional crystal structure, has many advantageous features, such as a high specific surface area, as well as favorable electrical, thermal, and mechanical properties. For example, graphene has sp lattice structures that form a hexagonal crystal lattice and resist deformation in various planes. 2 Due to the stability of the bond, it has excellent mechanical properties.

[0032] Potential applications of graphene include use in composites (e.g., as a reinforcing or thermal agent), field effect transistors, electromechanical systems, strain sensors, electronics, batteries, supercapacitors, micro-nanodevices, hydrogen storage, and solar cells. As the availability of low-cost, high-quality graphene increases, the applications of graphene will expand.

[0033] However, conventional methods for producing graphene are full of defects. In most cases, these defects can affect the mechanical properties of graphene and graphene-based composites as well as their thermal and electrical conductivity. Graphene defects can be classified into two different groups: intrinsic defects and extrinsic defects.

[0034] Intrinsic defects are the non-sp 2 The graphene may be composed of orbitally hybridized carbon atoms. Intrinsic defects in graphene may cause the graphene layers to be attached to each other. Ideal graphene without defects has no chemically bonded carbon atoms between the layers. However, if graphene has intrinsic defects (e.g., holes, dangling bonds, or mobile carbon atoms), the defective graphene layer may form new chemical bonds with neighboring carbon atoms in other graphene layers.

[0035] Extrinsic defects are defined by the crystalline order of graphene that is disturbed by foreign atoms or non-carbon atoms. Foreign atoms can be substitutional (replacing original lattice atoms) or interstitial. In previous methods, the foreign atoms are most often oxygen atoms or oxygen-containing functional groups such as hydroxyl or carboxyl groups. In fact, oxygen atoms in graphene are difficult to completely remove during the subsequent reduction process, and therefore the best way to produce graphene with low levels of oxygen-related defects is to prevent contamination during the synthesis of graphene itself, as taught herein.

[0036] Defects can affect the mechanical, electrical, and thermal properties of graphene. For example, the thermal conductivity of ideal graphene is about 5000 W / m·K, but defects can change the thermal conductivity. It has been found that point defects or single void defects in graphene can reduce the thermal conductivity to 20% of the previous figure. If the defect concentration is further increased, the thermal conductivity can be further reduced.

[0037] Various techniques may be used to characterize graphene, including Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), ICP mass spectrometry (ICP-MS), proton induced X-ray emission, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), oxidative combustion, and / or thermogravimetric analysis.

[0038] In some embodiments, Raman spectroscopy is used to characterize graphene. Raman spectroscopy can be used to evaluate the electronic structure and in identifying the two-dimensional nature of graphene. In particular, the D peak in the Raman spectrum of graphene is absent in ideal graphene, but increases in intensity as the number of defects increases. The D peak is associated with grain boundaries, vacancies, edges, sp 3The G peak is sensitive to the breaking of the symmetry of the graphene honeycomb lattice, such as the carbon atoms due to hybridization. The G peak, on the other hand, is sensitive to the number of layers present in the graphene. In some embodiments, the ratio of the intensities of the D and G peaks, I(D) / I(G), is used to estimate the level of defects in graphene. However, as the disorder of graphene increases, I(D) / I(G) exhibits two different behaviors. There is a region of "low" defect density, where I(D) / I(G) increases with more defects. This phenomenon occurs up to a region of "high" defect density, at which point I(D) / I(G) begins to decrease as the carbon structure becomes more amorphous due to the increasing defect density and all Raman peaks are attenuated. Furthermore, single-layer graphene can also be identified by analyzing the peak intensity ratio of the 2D and G bands. For example, the I(2D) / I(G) ratio of defect-free single-layer graphene is equal to 2.

[0039] The oxygen content of graphene can be characterized by photoelectron spectroscopy. UV-Vis spectroscopy is also useful for the chemical analysis of graphene dispersions in different solvents, since it allows the monitoring of reaction processes by using the Beer law and the linear relationship between the absorbance of the solution and the concentration. Furthermore, XRD can be applied to evaluate the exfoliation and intercalation of graphite, as well as the final formation of graphene.

number

[0040] Various forms of microscopy may be used to evaluate graphene and the degree or lack of defects. TEM may be used to characterize the atomic structure of graphene, for example to quantify intrinsic defects in graphene including vacancies, bond rotations, dislocation edges, grain boundaries, and to visualize the stacking of layers. SEM may be used to observe the surface morphology of graphene. STM may provide information about the morphology and electronic properties of graphene in three dimensions. AFM may be used to characterize the number of layers of graphene.

[0041] Production of high-purity solid carbon sources The present invention produces graphene from a high purity solid carbon source. In some embodiments, the solid carbon source is produced from carbon oxides, including carbon monoxide (CO) and carbon dioxide (CO2). The carbon oxides may be reduced, in some embodiments, with a reducing gas, such as hydrogen gas, to form solid carbon. U.S. Patent No. 8,679,444, incorporated herein by reference, describes various methods of producing solid carbon by reduction of carbon oxides.

[0042] There is a spectrum of reactions involving carbon, hydrogen, and oxygen that can produce solid carbon. Pyrolysis of hydrocarbons is a range of equilibria between hydrogen and carbon that favors the production of solid carbon, generally with little or no oxygen present. The Boudouard reaction, also called carbon monoxide disproportionation, is a range of equilibria between carbon and oxygen that favors the production of solid carbon, generally with little or no hydrogen present. The Bosch reaction is a range of equilibria where carbon, oxygen, and hydrogen are all present that favor the production of solid carbon. Other equilibria favor the production of carbon oxides or hydrocarbons without a solid carbon product (e.g., Sabatier and Fischer-Tropsch processes).

[0043] The Bosch reaction (CO2+2H2←→C+2H2O) reduces carbon dioxide with hydrogen to produce solid carbon and water. The temperature of the Bosch reaction can range from 400° C. to over 2000° C. In some embodiments, a catalyst can be used to improve the reaction rate and reduce the reaction temperature. In some embodiments, a solid carbon source is formed via the Bosch reaction. In some embodiments, the solid carbon formed via the Bosch reaction is used to produce graphene.

[0044] The Boudouard reaction (2CO←→C+CO), also known as carbon monoxide disproportionation, reduces carbon monoxide to produce solid carbon and carbon dioxide. In some embodiments, a solid carbon source is formed via the Boudouard reaction. In some embodiments, the solid carbon formed via the Boudouard reaction is used to produce graphene.

[0045] The type, purity, and uniformity of the solid carbon source can be controlled by the reaction conditions (time, temperature, pressure, partial pressure of reactants) and, in some embodiments, by the catalyst (such as size, method of formation, and morphology of the catalyst).

[0046] In some embodiments, the temperature for the production of the solid carbon source is 400°C to 2000°C, e.g., 400°C to 700°C, 400°C to 800°C, 400°C to 900°C, 400°C to 1000°C, 400°C to 1200°C, 400°C to 1400°C, 400°C to 900°C, 500°C to 600°C, 500°C to 700°C, 500°C to 800°C, 550°C to 650°C, 550°C to 750°C, 575°C to 625°C, 600°C to 650 ... The temperature may be in the range of 0°C, 600°C to 700°C, 600°C to 800°C, 625°C to 675°C, 650°C to 700°C, 700°C to 1200°C, 700°C to 1400°C, 800°C to 1200°C, 800°C to 1400°C, 900°C to 1400°C, 1000°C to 1400°C, 1100°C to 1400°C, 1200°C to 1400°C, 1300°C to 1400°C, 1000°C to 2000°C, or 1400°C to 2000°C.

[0047] In some embodiments, the solid carbon source is produced under pressure. In some embodiments, the pressure for producing the solid carbon is between 1 bar and 10 bar, e.g., between 1 bar and 2 bar, between 1 bar and 3 bar, between 1 bar and 4 bar, between 1 bar and 5 bar, between 1 bar and 6 bar, between 1 bar and 7 bar, between 1 bar and 8 bar, between 1 bar and 9 bar, between 2 bar and 3 bar, between 2 bar and 4 bar, between 2 bar and 5 bar, between 2 bar and 6 bar, between 2 bar and 7 bar, between 2 bar and 8 bar, between 2 bar and 9 bar, between 2 bar and 10 bar, between 3 bar and 4 bar, between 3 bar and 5 bar, between 3 bar and 6 bar, between 3 bar and 7 bar, between 3 bar and 8 ... The pressure range may be from 1000 to 9 bar, 3 bar to 10 bar, 4 bar to 5 bar, 4 bar to 6 bar, 4 bar to 7 bar, 4 bar to 7 bar, 4 bar to 8 bar, 4 bar to 9 bar, 4 bar to 10 bar, 5 bar to 6 bar, 5 bar to 7 bar, 5 bar to 8 bar, 5 bar to 9 bar, 5 bar to 10 bar, 6 bar to 7 bar, 6 bar to 8 bar, 6 bar to 9 bar, 6 bar to 10 bar, 7 bar to 8 bar, 7 bar to 9 bar, 7 bar to 10 bar, 8 bar to 9 bar, 8 bar to 10 bar, or 9 bar to 10 bar. In some embodiments, the solid carbon source is produced under atmospheric pressure. In some embodiments, the solid carbon source is produced under vacuum.

[0048] The use of an inert gas during the production of a solid carbon source is beneficial in that it limits the introduction of foreign atoms, such as those found in the atmosphere, into the system. In some embodiments, the solid carbon source is produced under an inert gas. In some embodiments, the inert gas is a noble gas. In some embodiments, the noble gas is argon or helium.

[0049] In some embodiments, the reaction includes a catalyst. A favorable reaction kinetic for the formation of a desired species of solid carbon can be established by including a suitable catalyst. For example, the reaction can be accelerated and run at a lower temperature in the presence of a catalyst. In some embodiments, for example, using a catalyst, the reaction can proceed to completion in less than 5 seconds (e.g., less than 4 seconds, less than 3 seconds, less than 2 seconds, less than 1 second, or less than 0.5 seconds). In some embodiments, the catalyst is iron. In some embodiments, the catalyst includes a coating, sheet, lattice structure, honeycomb structure, etc. In some embodiments, the catalyst includes a repeating honeycomb. A lattice or honeycomb structure catalyst is advantageous in that the unique structure can increase the surface area of ​​the catalyst while also maintaining the strength of the catalyst.

[0050] The solid carbon source can be in the form of graphite, graphene, carbon black, amorphous carbon, fibrous carbon, Buckminsterfullerenes (e.g., buckyballs, single-walled carbon nanotubes, and multi-walled carbon nanotubes), etc. In some embodiments, the solid carbon source comprises greater than 90% (w / w) amorphous carbon, e.g., greater than 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.95%, or 99.99% (w / w) amorphous carbon. In some embodiments, the solid carbon source comprises greater than 90% (w / w) graphitic carbon, e.g., greater than 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.95%, or 99.99% (w / w) graphitic carbon.

[0051] The obtained solid carbon source is of high purity. The method of the present invention is advantageous in that the graphene produced is substantially free of defects due to the high purity of the solid carbon source. In some embodiments, the solid carbon source is more than 99.99% (w / w) elemental carbon (e.g., more than 99.995% (w / w), more than 99.999% (w / w), more than 99.9995% (w / w), or more than 99.9999% (w / w) elemental carbon).

[0052] Producing high quality graphene The present invention relates to the synthesis of graphene by flash joule heating (FJH) of a high purity solid carbon source, which is advantageous in that the resulting graphene is nearly defect-free compared to previous methods. In FJH, a voltage pulse is applied across a solid carbon source, rapidly heating it to produce graphene. FJH is described in U.S. Patent Publication No. US20210206642A1, which is incorporated herein by reference.

[0053] The method of the present invention rapidly produces graphene from a high purity solid carbon source. In some embodiments, the duration of the voltage pulse may be less than 5 seconds (e.g., 4 seconds, 3 seconds, 2 seconds, 1 second, 500 milliseconds, 400 milliseconds, 300 milliseconds, 200 milliseconds, 100 milliseconds, 10 milliseconds, 1 millisecond, 500 microseconds, 100 microseconds, less than 10 microseconds). The voltage across the sample may be between 1 V / cm and 4000 V / cm. The step of applying a voltage pulse across the material to form graphene may include multiple voltage pulses applied across the material. In some embodiments, the number of voltage pulses may range from 1 pulse to 100 pulses.

[0054] The inventive method of producing graphene is advantageous in that it can produce bulk quantities of high quality or purity graphene, which is needed in both industry and academia, and can propel graphene into further commercial applications. Bulk graphene as currently produced is known to be highly defect-prone, adversely affecting the mechanical, thermal, and electrical properties of graphene. In some embodiments, the inventive method is scaled to produce at least 1 gram of graphene (e.g., at least 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, 7 grams, 8 grams, 9 grams, 10 grams, 20 grams, 25 grams, 30 grams, 40 grams, 50 grams, 75 grams, 100 grams, 150 grams, 200 grams, 250 grams, 300 grams, 400 grams, 500 grams, 750 grams, 1 kilogram, or more) per hour or day.

[0055] The methods of producing graphene of the invention are also advantageous in that they produce a high yield of graphene from a solid carbon source. In some embodiments, the yield of graphene from a solid carbon source is at least 90% (w / w) (e.g., at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.5%, at least 99.9%, at least 99.95%, at least 99.99%, at least 99.995%, at least 99.999%, at least 99.9995%, or at least 99.9999%).

[0056] In some embodiments, the graphene has properties close to ideal graphene due to the absence of extrinsic and / or intrinsic defects.

[0057] In some embodiments, the graphene has at least 10 4 S / m (e.g., at least 1.5×10 4 S / m, at least 2×10 4 S / m, at least 2.5×10 4 S / m, at least 3×10 4 S / m, at least 3.5×10 4 S / m, at least 4×10 4 S / m, at least 4.5×10 4 S / m, at least 5×10 4 S / m, at least 5.5×10 4 S / m, at least 6×10 4 S / m, at least 6.5×10 4 S / m, at least 7×10 4 S / m, at least 7.5×10 4 S / m, at least 8×10 4 S / m, at least 8.5×10 4 S / m, at least 1.5×10 4 S / m, at least 9×10 4 S / m, or at least 9.5×10 4In some embodiments, the electrical conductivity of graphene is measured by conductive atomic force microscopy (C-AFM).

[0058] In some embodiments, the graphene has a specific surface area (SSA) of 1000 m 2 / g (e.g., 1100m 2 / g, 1200m 2 / g, 1300m 2 / g, 1400m 2 / g over 1500m 2 / g, 1600m 2 / g, 1700m 2 / g over 1800m 2 / g, 1900m 2 / g over 2000m 2 / g, 2100m 2 / g, 2200m 2 / g, 2300m 2 / g, 2400m 2 / g or more than 2500m 2 / g). In some embodiments, the SSA of graphene is measured by the Brunauer-Emmett-Teller (BET) model.

[0059] In some embodiments, the graphene is a graphene flake, and the graphene flake has an average lateral size (D50) of at least 10 μm (e.g., at least 50 μm, at least 100 μm, at least 150 μm, at least 200 μm, at least 250 μm, at least 300 μm, at least 350 μm, at least 400 μm, at least 450 μm, at least 500 μm, at least 550 μm, at least 600 μm, at least 650 μm, at least 700 μm, at least 750 μm, at least 800 μm, at least 850 μm, at least 900 μm, at least 950 μm, or at least 1 mm). In some embodiments, the average lateral size of the graphene flakes is measured by static light scattering.

[0060] In some embodiments, the graphene contains less than 200 ppm of extrinsic defects (e.g., less than 100, 75, 50, 25, 10, 5, or 1 ppm of extrinsic defects). A common extrinsic defect in the production of graphene is contaminated oxygen. In some embodiments, the graphene contains less than 200 ppm of oxygen (e.g., less than 100, 75, 50, 25, 10, 5, or 1 ppm of oxygen). The level of extrinsic defects can be determined by Raman spectroscopy.

[0061] The methods of the present invention minimize intrinsic and extrinsic defects. In some embodiments, the graphene contains less than 0.01% intrinsic defects (e.g., less than 0.005%, 0.001%, 0.0005%, or 0.0001% intrinsic defects). Intrinsic defects include standard sp 2 In contrast to sp 3 In some embodiments, the graphene has carbon atoms hybridized with more than 90% sp 2 Hybridized carbon atoms (e.g., greater than 95%, 96%, 97%, 98%, 99%, 99.9%, 99.95%, 99.99%, 99.995%, 99.999%, 99.9995%, or 99.9999% sp 2- In some embodiments, the graphene comprises less than 10% sp 3 Hybridized carbon atoms (e.g., less than 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, 0.01%, 0.005%, 0.001%, 0.0005%, or 0.0001% sp 3- The carbon hybridization may be determined by X-ray photoelectron spectroscopy (XPS) or Raman spectroscopy.

[0062] In some embodiments, the graphene comprises multiple graphene sheets. Raman spectroscopy or ellipsometry may be used to assess the number of layers. Due to the absence of extrinsic defects, the graphene sheets remain unbonded and retain their 2D properties upon stacking, such as a low I(D) / (G) ratio, as determined by Raman spectroscopy. In some embodiments, the graphene has an I(D) / I(G) ratio of less than 0.2 (e.g., less than 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, 0.005, 0.001, 0.0005, 0.0001, 0.00005, or 0.00001). In some embodiments, the graphene has an I(2D) / I(G) ratio in the range of 0.5 to 2 (e.g., between 0.6 to 2, 0.7 to 2, 0.8 to 2, 0.9 to 2, 1 to 2, 1.1 to 2, 1.2 to 2, 1.3 to 2, 1.4 to 2, 1.5 to 2, 1.6 to 2, 1.7 to 2, 1.8 to 2, or 1.9 to 2).

[0063] In one embodiment, the present invention provides a method for producing graphene, where a solid carbon source is produced in a first chamber, and the solid carbon source is transferred to a second chamber, the second chamber comprising a plurality of electrodes, and a voltage pulse is applied across the solid carbon source to convert the solid carbon source to graphene. However, in some embodiments, the solid carbon source and graphene may be produced in the same chamber. In one embodiment, the present invention provides a method for producing graphene, where a solid carbon source is produced in a chamber, the chamber comprising a plurality of electrodes, and the plurality of electrodes applies a voltage pulse across the solid carbon source to convert the solid carbon source to graphene. A closed system, such as two interconnected chambers, or a single chamber, may be advantageous in that it minimizes the risk of exposing the system to foreign substances, such as the atmosphere.

[0064] Figures 1A, 1B, and 1C show one embodiment of a chamber. In some embodiments, the chamber is non-conductive and / or non-reactive. In some embodiments, the chamber is resistant to high heat and pressure, for example, temperatures above 700°C and pressures above 200 PSI. In some embodiments, the chamber comprises Monel K500. Figures 2A and 2B show a catalyst for use with the chamber of Figures 1A, 1B, and 1C. The catalyst may be iron.

[0065] The electrodes may be non-corrosive and resistant to high temperatures, hi some embodiments, the electrodes comprise Inconel, which is advantageous because it has high electrical conductivity.

[0066] In some embodiments, the graphene production system comprises polytetrafluoroethylene (PTFE). In some embodiments, the graphene production system comprises a PTFE-lined chamber. In some embodiments, the graphene production system comprises a PTFE-lined carbon steel pipe, such as a PTFE-lined carbon steel schedule 40 pipe. PTFE is advantageous in that it is a non-corrosive material that can withstand high temperatures and pressures.

[0067] The chamber may include a seal. In some embodiments, the seal includes a silicone, such as a mica-silicon composite. The mica-silicon composite is advantageous in that it provides high heat resistance and sealing under high pressure. Figure 3 shows one embodiment of a seal for use in the chamber of Figures 1A, 1B, and 1C.

[0068] Once produced, graphene is prepared in a variety of ways to produce secondary products. Preparation strategies include, for example, solution blending, melt blending, in situ polymerization, and layer-by-layer assembly. The graphene disclosed herein is advantageous in that it does not require post-processing (e.g., purification) before preparation for secondary use. By producing graphene from a high purity solid carbon source, post-processing steps typically required in graphene production are avoided. In some embodiments, graphene may be mixed with a binder (e.g., a polymer solution) or dispersion to form a mixture without a prior purification step. In some embodiments, the binder is a polymer solution. Graphene may be present in the mixture at between 0.1% and 99.99% (w / w) (e.g., between 0.1% and 1% (w / w), between 1% and 5% (w / w), between 5% and 10% (w / w), 10% (w / w) and 25% (w / w), 25% and 50% (w / w), 50% and 75% (w / w), or 90% and 99.99% (w / w)). In some embodiments, graphene may be present in the mixture at greater than 90% (w / w) (e.g., greater than 91% (w / w), 92% (w / w), 93% (w / w), 94% (w / w), 95% (w / w), 96% (w / w), 97% (w / w), 98% (w / w), or 99% (w / w)). EXAMPLES

[0069] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to perform, make and evaluate the methods and compounds claimed in this disclosure, and are intended to be merely illustrative of the invention and are not intended to limit the scope of what the inventors regard as their invention.

[0070] Example 1: Production of high-quality graphene A stoichiometric mixture of carbon dioxide and hydrogen gas is added to a first chamber according to the Bosch reaction. The chamber is heated to 600°C and pressurized with argon gas. After one hour, the chamber is purged with argon and the resulting solid carbon is transferred to a second chamber. The solid carbon is deposited between two electrodes connected to a number of capacitors operable to apply voltage pulses. Voltage pulses having a duration of 10 milliseconds and a voltage between 100V and 400V are applied to the solid carbon to produce high purity graphene.

Claims

1. A method for producing graphene: a. To provide a high-purity solid carbon source, wherein the solid carbon source provides elemental carbon exceeding 99.99% (w / w), b. Applying a voltage pulse to the entire solid carbon source to convert the solid carbon source into graphene, wherein the graphene contains less than 200 ppm of extrinsic defects, The method, including the method described above.

2. The method according to claim 1, wherein the solid carbon source is elemental carbon exceeding 99.995% (w / w).

3. The method according to claim 1, wherein the solid carbon source is elemental carbon exceeding 99.999% (w / w).

4. The method according to claim 1, wherein the solid carbon source is elemental carbon exceeding 99.9995% (w / w).

5. The method according to claim 1, wherein the solid carbon source is elemental carbon exceeding 99.9999% (w / w).

6. The method according to claim 1, wherein the graphene includes extrinsic defects of less than 100 ppm.

7. The method according to claim 1, wherein the graphene includes extrinsic defects of less than 50 ppm.

8. The method according to claim 1, wherein the graphene includes extrinsic defects of less than 25 ppm.

9. The method according to claim 1, wherein the graphene includes extrinsic defects of less than 10 ppm.

10. The method according to claim 1, wherein the graphene includes extrinsic defects of less than 5 ppm.

11. The method according to claim 1, wherein the graphene includes extrinsic defects of less than 1 ppm.

12. The method according to claim 1, wherein the extrinsic defect is evaluated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma emission spectrometry (ICP-OES), ICP mass spectrometry (ICP-MS), proton-induced X-ray emission, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning tunneling microscope (STM), atomic force microscopy (AFM), energy-dispersive X-ray analysis (EDX), oxidative combustion, and / or thermogravimetric analysis.

13. The method according to claim 1, wherein the extrinsic defect is oxygen.

14. The method according to claim 13, wherein the graphene contains less than 200 ppm of oxygen.

15. The method according to claim 1, wherein the graphene contains less than 0.01% intrinsic defects.

16. The aforementioned intrinsic defect is nonsp ２ The method according to claim 1, comprising orbital hybridized carbon atoms.

17. The aforementioned graphene is less than 0.01% sp ３ The method according to claim 1, including the method described in claim 1.

18. Percent sp of the aforementioned graphene ２ The method according to claim 1, wherein the percentage is at least 95%.

19. The method according to claim 1, wherein the graphene has an I(D) / I(G) ratio of less than 0.2 as measured by Raman spectroscopy.

20. The method according to claim 1, wherein the graphene has an I(D) / I(G) ratio between 0.5 and 2, as measured by Raman spectroscopy.

21. The electrical conductivity of the graphene is at least 10 ４ The method according to claim 1, wherein the ratio is S / m.

22. The specific surface area (SSA) of the graphene is 1000 m². ２ The method according to claim 1, which is greater than / g.

23. The method according to claim 1, wherein the graphene is graphene flakes and the graphene flakes have an average transverse size (D50) of at least 10 μm.

24. The method according to claim 1, wherein the graphene is not purified after step b).

25. The method according to claim 1, wherein the extrinsic defect is not removed after step b).

26. The method according to claim 1, wherein the solid carbon source contains more than 90% (w / w) amorphous carbon.

27. The method according to claim 1, wherein the solid carbon source contains more than 90% (w / w) graphite carbon.

28. The method according to claim 1, wherein the solid carbon source is produced by reducing carbon dioxide or carbon monoxide with hydrogen gas.

29. The method according to claim 1, wherein the solid carbon source is produced from carbon dioxide and hydrogen gas via a Bosch reaction.

30. The method according to claim 1, wherein the hydrogen gas is provided in an amount greater than the stoichiometric ratio required for the reduction of carbon dioxide or carbon monoxide.

31. The method according to claim 1, wherein the solid carbon source is produced from carbon monoxide via a Booduor reaction.

32. The method according to claim 29, wherein the reaction comprises a catalyst or a catalyst precursor.

33. The method according to claim 29, wherein the reaction occurs at room temperature.

34. The method according to claim 29, wherein the reaction occurs at a temperature between 450°C and 2000°C.

35. The method according to claim 1, wherein step b) is performed under atmospheric pressure.

36. The method according to claim 1, wherein the method produces at least 1 gram of graphene.

37. The method according to claim 1, wherein the yield of graphene from the solid carbon source is at least 90%.

38. The method according to claim 1, further comprising the step of c) mixing the graphene with a binder or dispersant without further purification.

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