Graphene separation

Abstract

The present invention relates to a method for producing graphene and / or graphene oxide. The method includes the steps of providing a copper-based sheet coated on one side with a carbonaceous material; + , Na + , K + , Mg 2+ or Ca 2+ The method includes providing a bath containing an aqueous solution containing a salt of at least one ion selected from the group consisting of: a first electrode disposed in the bath; providing a copper-based sheet in the bath; applying a first voltage between the copper-based sheet and the first electrode; and applying a second voltage, opposite to the first voltage, between the copper-based sheet and the first electrode such that the graphene and / or graphene oxide is exfoliated from the carbonaceous material. The present invention also relates to a system for producing graphene and / or graphene oxide. The present invention also relates to a graphene material formed as crystalline, self-supporting hexagonal flakes. The present invention also relates to a graphene material formed as crystalline, self-supporting flakes consisting of dendrites.

Description

Technical Field

[0001] The present invention relates to a method for producing at least one of graphene and graphene oxide, a production system for at least one of graphene and graphene oxide, and a graphene material formed as a self-supporting crystal flake.

Background Art

[0002] Since two-dimensional materials, particularly graphene, were first synthesized in the early 21st century, they have attracted great attention mainly due to their mechanical, electronic, and optical properties. Since the discovery of graphene materials, their use in various applications has been steadily increasing. Several methods have been proposed for the production of graphene, such as chemical vapor deposition (CVD) and exfoliation methods.

[0003] Graphene or a graphene composite can be produced on a metal substrate such as a copper substrate. Patent Document 1 discloses a method for producing a carbon composite material including a graphene film disposed on an amorphous carbon substrate on a metal surface such as a copper surface. Patent Document 1 discloses that, for example, flakes of the composite material can be removed from the copper substrate by dissolution of copper using a strong acid or by electrolytic exfoliation. The disclosed electrolytic exfoliation uses copper as the first electrode, a graphite electrode as the second electrode, and a 0.05 M NaOH solution as the electrolyte, and then applies a current of 25 mA / cm 2 to the electrodes. Thereafter, the copper electrode was transferred to a container of MilliQ water, and flakes of the composite material were removed.

[0004] However, there is a need in the art today for a method of producing at least one of pure crystalline graphene and graphene oxide from a carbonaceous material supplied on a copper substrate, preferably in a manner that does not consume the copper substrate.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2019 / 180227 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to alleviate at least some of the problems associated with the prior art. In particular, the object of the present invention is to provide an improved method for producing at least one of pure and crystalline graphene and graphene oxide from a carbonaceous material deposited on a metal substrate, preferably a copper substrate. The object of the present invention is to provide a method for producing at least one of graphene and graphene oxide that provides flakes of at least one of pure and crystalline graphene and graphene oxide without consuming a metal substrate. [Means for solving the problem]

[0007] These and other problems are addressed by a method for producing at least one of graphene and graphene oxide, which includes the following steps: - The step of providing a copper-based sheet with at least one side coated with a carbonaceous material, -Li + na + , K + Mg 2+ or Ca 2+ The steps include providing a bathtub containing an aqueous solution containing a salt of at least one ion selected from, and placing a first electrode in the bathtub, - The step of putting the copper sheet into the bathtub, - The steps of applying a first voltage between a copper-based sheet and a first electrode such that at least one ion is intercalated into the carbonaceous material, - Applying a second voltage opposite to the first voltage between the copper-based sheet and the first electrode so that at least one of graphene and graphene oxide is exfoliated from the carbonaceous material.

[0008] According to one aspect of the concept of the present invention, there is provided a method for producing at least one of graphene and graphene oxide, including the following steps. The method - Providing a copper-based sheet coated with a carbonaceous material on at least one side; - Li + 、Na + 、K + 、Mg 2+ or Ca 2+ - Providing a bath containing an aqueous solution containing a salt of at least one ion selected from the group consisting of, and disposing a first electrode in the bath; - Inserting the copper-based sheet into the bath; - Applying a first voltage between the copper-based sheet and the first electrode so that at least one ion is intercalated into the carbonaceous material; - Applying a second voltage opposite to the first voltage between the copper-based sheet and the first electrode so that at least one of graphene and graphene oxide is exfoliated from the carbonaceous material.

[0009] The method for producing at least one of graphene and graphene oxide according to the present invention is advantageous in that it provides a method for producing at least one of pure and crystalline high-quality graphene and graphene oxide without consuming copper plates.

[0010] The present invention is based on the recognition that at least one of graphene and graphene oxide can be produced by a method comprising the intercalation of large alkali or alkali metal ions into a carbonaceous material provided on a copper substrate. Ion intercalation is mitigated by applying a voltage between the copper substrate and an electrode, which causes positive ions to move toward the copper-based sheet and intercalate between the graphene sheets of the carbonaceous material. Intercalation increases the distance between graphene sheets in the carbonaceous material, thereby weakening the binding force between the materials. When the voltage between the copper substrate and the electrode is reversed, the intercalated ions move away from their intercalation locations in the carbonaceous material, thereby causing at least one of graphene and graphene oxide to detach and be removed from the carbonaceous material.

[0011] The method according to the present invention involves a copper-based sheet in which at least one side, for example both sides, is coated with a carbonaceous material, Li + na + , K + Mg 2+ or Ca 2+ This is carried out by supplying a bath containing an aqueous solution containing a salt of at least one ion selected from the following. Preferably, the bath does not contain solutions that would dissolve or damage the copper substrate, such as strong acids. Thus, a method can be obtained to remove at least one of graphene and graphene oxide from carbonaceous material deposited on a copper sheet without consuming the copper sheet.

[0012] The copper sheet is preferably supplied into the bath by a supply device configured to supply the copper sheet into the bath for a two-stage process of intercalation and peeling. The supply device then removes the copper sheet from the bath after the two-stage process. This can be achieved, for example, in a manner similar to how a continuous paper web moves through a paper machine. The copper sheet is attached between a first roller and a second roller. The copper sheet is positioned to move through the bath by a pair of support guide rollers provided in the bath. Thus, a continuous process can be achieved in which a new portion of the copper sheet is continuously supplied into the bath by the first and second rollers, subjected to the two-stage process, and removed from the bath by the rollers. Simultaneously, a new portion of the copper sheet is supplied into the bath. This process can preferably be carried out continuously over the length of the copper sheet.

[0013] The two-step process of intercalation and exfoliation is carried out by supplying a first voltage between an electrode and a copper sheet provided in a bath. This voltage can be obtained by contacting the copper sheet with an electrode such as an inert electrode, such as a platinum electrode. A voltage control means can then be used to apply the first voltage between the copper sheet and a counter electrode in the bath. Since the intercalated ions have a positive charge, the first voltage is selected so that the copper sheet attracts the positive ions, thereby mitigating the intercalation of positive ions into the carbonaceous material. After intercalation, by reversing the voltage from the first voltage, the intercalated ions are attracted to the counter electrode, thereby mitigating the exfoliation of at least one of graphene and graphene oxide from the carbonaceous material. At least one of the graphene and graphene oxide removed from the carbonaceous material was found to be of high purity and crystallinity.

[0014] The first voltage may be in the range of -8V to -2V, for example, in the range of -6V to -2V. The first voltage may be applied for a period of at least 0.5 seconds, for example, a period of 1 second to 5 seconds, or at least 1 second.

[0015] Alternatively, the first voltage may be in the range of -30V to -2V, for example, -12V to -2V, for example, -10V to -2V, for example, -8V to -2V, for example, -6V to -2V. Alternatively, the first voltage may be -2V or less.

[0016] The second voltage may be in the range of +2V to +12V, for example, in the range of +2V to +8V. The second voltage can be applied for a period of less than 0.15 seconds, for example, less than 0.1 seconds. Preferably, the second voltage is applied for a shorter time than the first voltage in order to prevent oxidation of the copper.

[0017] Alternatively, the second voltage may be in the range of +0.3V to +12V, for example, in the range of +0.5V to +12V, for example, in the range of +2V to +12V, for example, in the range of +2V to +10V, for example, in the range of +2V to +8V.

[0018] Alternatively, the second voltage may be +0.3V or higher.

[0019] The inventors have found that when using copper-based sheets, an upper limit of +12V for the second voltage may be sufficient. Furthermore, it has been found that the lower limit of the first voltage (i.e., the negative voltage with the largest absolute value) is preferably selected by considering one or more setting parameters, such as the thickness and capacitance of the lead wires connected to the voltage control means (e.g., to avoid lead wire melting), the volume of the aqueous solution, and the salt concentration. In some situations, it has been found that it is possible to carry out a method according to the concept of the present invention with a first voltage lower than -30V.

[0020] Furthermore, it should be understood that the lower and upper limits of the disclosed first voltage range can be combined to form ranges not explicitly formulated in this disclosure. Similarly, it should be understood that the lower and upper limits of the disclosed second voltage range can be combined to form ranges not explicitly formulated in this disclosure.

[0021] The voltage control means is preferably configured as appropriate to provide the voltage disclosed above.

[0022] The two-step process of intercalation and peeling can be performed multiple times, such that the same carbonaceous material is subjected to a voltage sequence that begins with a first voltage, is followed by a second voltage, and so on, while the copper-based sheet moves through the bath. This process can be repeated continuously until at least one of graphene and graphene oxide is sufficiently removed from the copper-based sheet.

[0023] Here, the term "graphene" refers to a two-dimensional carbon material well known to those skilled in the art. The term is also intended to refer to so-called "multiple layers of graphene," which refers to a material consisting of stacked layers of 2 to 10 layers of graphene.

[0024] Here, the term "graphene oxide" refers to graphene oxide, as is well known to those skilled in the art, i.e., oxidized two-dimensional carbon material. It is also intended to refer to several layers of oxidized graphene.

[0025] Here, the term “copper-based sheet” is intended to refer to a sheet of copper metal or a copper alloy. The copper-based sheet may be provided as a foil. The sheet is preferably thin enough so that the copper-based sheet is wound onto rollers configured in the feeding device of this disclosure. The sheet may preferably have a thickness much smaller than the width of the sheet. Preferably the width is much smaller than the length of the sheet.

[0026] The term "one-sided coating" refers to the provision of a carbonaceous material on at least one side of a copper-based sheet. The coating does not need to completely cover the sheet.

[0027] The coating may be applied to both sides of the copper-based sheet.

[0028] The term "carbonaceous material" refers to a carbon material from which graphene can be exfoliated according to the present invention. The carbonaceous material of this invention may consist of at least one of bound graphene and graphene oxide. The carbonaceous material may consist of graphite, which consists of laminated and bound graphene sheets. Alternatively, or in addition to the above, the carbonaceous material may consist of a carbon composite material comprising graphite, a graphene film disposed on a graphite substrate, and / or a graphene film disposed on an amorphous carbon substrate. The carbonaceous material may consist of graphite, a graphene film disposed on a graphite substrate, and / or a graphene film disposed on an amorphous carbon substrate. In the process according to the present invention, bound graphene in the carbonaceous material is removed by an intercalation / exfoliation process. The carbonaceous material may contain at least 80% by weight of carbon, for example, at least 90% by weight of carbon, for example, at least 95% by weight of carbon, for example, carbon consisting of essentially a certain amount of carbon by weight. Therefore, the present invention provides a method for separating at least one of graphene and graphene oxide from a carbonaceous material provided on a copper-based sheet. In principle, by repeating intercalation / exfoliation, at least one layer of graphene and graphene oxide can be exfoliated per intercalation / exfoliation cycle.

[0029] Therefore, the conceptual method according to the present invention is considered to be advantageously flexible in that at least one of graphene and graphene oxide can be produced from multiple different carbonaceous materials.

[0030] The term “Li + na+ , K + Mg 2+ or Ca 2+ "An aqueous solution containing a salt of at least one ion selected from Li" is Li + na + , K + Mg 2+ or Ca 2+ This refers to a composition formed by supplying a salt containing to water or a solution containing a large amount of water. Here, the aqueous solution does not have to contain strong acids such as HCl, H2SO4, and HNO3. Nor does it have to contain other compositions known to degrade copper. Preferably, the aqueous solution contains Ca 2+ or Na + It consists of.

[0031] It is believed that when ions become larger during intercalation, the separation between adjacent graphene sheets in the carbonaceous material increases, thereby mitigating delamination. The ion concentration in the bath can be at least 0.001 M, in the range of 0.001 to 0.1 M, for example, in the range of 0.001 M to 0.01 M, for example, in the range of 0.002 M to 0.006 M.

[0032] The "first electrode" may refer to an inert electrode such as a platinum electrode. The first electrode may be positioned as a roller in the bathtub and guide the copper sheet as it moves through the bathtub. In this way, a good conductive contact can be provided between the electrode and the copper sheet, allowing a voltage to be supplied.

[0033] The bathtub is equipped with at least one counter electrode.

[0034] In some embodiments, the carbonaceous material consists of a graphene film disposed on an amorphous carbon substrate.

[0035] Patent Document 1 discloses a method for producing a composite material including a graphene film disposed on an amorphous carbon substrate on a metal surface such as a copper surface. The method disclosed herein may be provided for producing flakes of at least one of graphene and graphene oxide from a composite material in an improved embodiment that obtains a high yield of at least one of graphene and graphene oxide without consuming copper-based sheets.

[0036] Carbonaceous materials can be obtained from bio-oils and / or lignin sources, such as lignin sources consisting of refined lignin, purified lignin, alkaline lignin, and lignosulfonates.

[0037] The term "bio-oil," sometimes called pyrolysis oil, tar, or biocrude, refers to oils obtained from raw materials such as coniferous trees like rapeseed, pine, fir, and spruce, or lipids from microalgae, or their residual products. Therefore, bio-oils are considered a renewable resource and an environmentally friendly method.

[0038] During the application of the first voltage, it is assumed that the ions supplied to the bath are intercalated between the graphene film and the amorphous carbon substrate. When the second voltage is applied, preferably at least 1 μm 2 Graphene flakes with an average size are exfoliated from the composite material. When the graphene film consists of several layers of graphene, intercalation is also thought to occur between the graphene layers of the several layers of graphene.

[0039] Graphene has a minimum thickness of 1 μm. 2 It can be exfoliated as flakes having an average size of [size]. Graphene oxide may also be exfoliated as flakes having a smaller size.

[0040] The inventors have surprisingly discovered that some of the exfoliated graphene can form as hexagonal flakes. These hexagonal flakes are thought to represent high-purity crystalline graphene. Such flakes offer the advantage of high conductivity and are suitable for use in a variety of electrical and electrochemical applications.

[0041] The inventors have further discovered that a portion of the graphene may be formed in the form of flakes consisting of dendrites. The dendritic shape is thought to be a precursor to hexagonal flakes.

[0042] In some examples, this method may further include the steps of supplying a lignin source and an aqueous solution to form a composition, depositing the composition onto a copper-based sheet, and heating the composition on the copper-based sheet to form a composite material on the copper-based sheet. This method can be carried out using heating temperatures and other process conditions as described in Patent Document 1, preferably temperatures of 500 to 1100°C. The reaction temperature may also be in the range of 600 to 1000°C, for example, 700 to 900°C, preferably 750 to 850°C, more preferably 790 to 815°C, for example, about 805°C. The reaction time, which corresponds to the time the composition on the copper-based sheet is exposed to the reaction temperature, is typically less than 1 hour, for example less than 50 minutes, preferably in the range of 10 to 50 minutes, for example about 30 minutes or about 20 minutes.

[0043] In some examples, this method may further include the steps of providing bio-oil, depositing the bio-oil onto a copper-based sheet, and heating the bio-oil on the copper-based sheet to form a carbon composite material on the copper-based sheet. This method can be carried out using heating temperatures and other process conditions as described in Patent Document 1, preferably temperatures of 500 to 1100°C. The reaction temperature may also be in the range of 600 to 1000°C, for example, 700 to 900°C, preferably 750 to 850°C, more preferably 790 to 815°C, for example, about 805°C. The reaction time, which corresponds to the time the bio-oil on the copper-based sheet is exposed to the reaction temperature, is typically less than 1 hour, for example less than 50 minutes, preferably in the range of 10 to 50 minutes, for example about 30 minutes or about 20 minutes.

[0044] The carbon composite material may consist of graphite, a graphene film disposed on a graphite substrate, and / or a graphene film disposed on an amorphous carbon substrate.

[0045] The inventors have surprisingly found that, for example, the concept of the present invention relating to graphene separation can be implemented using any carbonaceous material. Preferably, the carbonaceous material may consist of graphite, a graphene film disposed on a graphite substrate, and / or a graphene film disposed on an amorphous carbon substrate.

[0046] The method steps described in paragraphs

[0037] and

[0038] utilize lignin to provide a carbonaceous material such as a carbon composite material, but other options are possible within the scope of the present invention, such as using bio-oil to provide a carbonaceous material such as a carbon composite material as disclosed in Example 2.

[0047] In some embodiments, the carbonaceous material consists of graphite. Graphite is a material in which graphene sheets are laminated and integrally bonded together by interlayer forces such as fragile van der Waals bonds. This method allows for the intercalation and exfoliation of ions in an aqueous solution between the graphene layers in the graphite material. It is known that when the carbonaceous material consists of graphite, at least one of graphene and graphene oxide can be exfoliated in the form of flakes.

[0048] In some embodiments, the copper sheet is supplied into the bathtub by a supply device comprising a plurality of rollers. The first roller may be located at a first end of the bathtub, and the second roller at a second end on the opposite side of the bathtub. At least one of the first and second rollers may be motor-driven, thereby automatically feeding the copper sheet into and passing through the bathtub. The plurality of rollers may further include at least one guide roller provided in the bathtub and configured to guide the copper sheet through the bathtub. The guide roller may be a passive roller.

[0049] In some embodiments, the first electrode is positioned as one of several rollers. The first electrode may be an inert electrode, such as a precious metal electrode, preferably a platinum electrode. The electrode is preferably positioned on a guide roller. In this way, good conductive contact can be obtained between the electrode and the copper-based sheet.

[0050] In some embodiments, this method -The procedure further includes filtering the aqueous solution to recover at least one of graphene and graphene oxide, and optionally providing a filtered aqueous solution containing copper ions. After the step of applying a second voltage, at least one of the detached graphene and graphene oxide is present in the aqueous solution in the bath. At least one of the graphene and graphene oxide can be separated from the aqueous solution by a filter such as a filter press. The filter may be configured to separate at least one of the graphene and graphene oxide from other types of carbonaceous residues in the aqueous solution, such as amorphous carbon.

[0051] The bathtub may include a liquid outlet for draining liquid from the bathtub. The liquid outlet may be in liquid communication with a filter for performing the filtration described above.

[0052] By applying the first voltage and the second voltage, a portion of the copper is oxidized to Cu 2+ This may also be done. As a result, Cu is added to the aqueous solution. 2+ It may exist.

[0053] In some embodiments, the method further includes the step of cleaning the copper-based sheet using ultrasonic treatment. After separating graphene or graphene oxide, ultrasonic treatment can be used to remove carbonaceous residue from the copper-based sheet.

[0054] In some embodiments, this method -The procedure further includes the step of reducing copper ions in the filtered aqueous solution on the copper sheet. If the copper on the copper sheet has oxidized and exists as copper ions in the aqueous solution, the step of reducing copper ions on the copper sheet may be performed. The copper sheet may have been previously washed to remove carbonaceous residue. This step is advantageous in that it minimizes material consumption of the copper sheet.

[0055] In some embodiments, the method may further include the step of centrifuging at least one of the recovered graphene and graphene oxide.

[0056] At least one of the obtained graphene and graphene oxide is preferably at least 1 μm thick. 2 It can be supplied in the form of flakes having a size. By centrifugation, sorting based on the size of at least one of the resulting graphene and graphene oxide is possible.

[0057] In some embodiments, the salt is Na + and Ca 2+ It includes at least one of the following. Larger ions are preferred because, compared to smaller ions, they are thought to increase the distance between graphene layers in the carbonaceous material during intercalation. This is thought to weaken the interlayer bonding in the carbonaceous material, thereby mitigating the delamination process.

[0058] In some embodiments, the pH of the bathtub is at least 6. Since acids can corrode copper sheets, it is preferable not to add acidic solutions to the bathtub.

[0059] In some embodiments, at least one of graphene and graphene oxide exfoliated from the carbonaceous material is at least 1 μm thick. 2 It consists of hexagonal flakes with crystalline and self-supporting properties, having an average size of [size missing].

[0060] The inventors have surprisingly found that at least one of the graphene and graphene oxide produced by this method exhibits high crystallinity and high purity. This is because at least one of the graphene and graphene oxide has a minimum particle size of 1 μm. 2This is illustrated by the fact that it can consist of crystalline and self-supporting hexagonal flakes with an average size of [size missing]. The term "self-supporting" indicates that the flakes can support their own weight. The shape can be determined using a microscope, such as a scanning electron microscope.

[0061] Hexagonal flakes are produced, in particular, when the carbonaceous material consists of a graphene film arranged on an amorphous carbon substrate.

[0062] In some embodiments, at least one of graphene and graphene oxide exfoliated from a carbonaceous material consists of crystalline and self-supporting flakes, preferably at least 1 μm in size. 2 The average size is [size not specified], and the flakes contain multiple dendrites. This can also be used as an indicator of high crystallinity and purity of at least one of the resulting graphene and graphene oxide. The dendritic shape is thought to be a precursor to the hexagonal shape.

[0063] Preferably, the flakes having dendrites are formed from graphene.

[0064] Preferably, the hexagonal flakes are formed from graphene.

[0065] Furthermore, the object of the present invention is achieved by a system for producing at least one of graphene and graphene oxide. The system is - A copper-based sheet coated with a carbonaceous material on at least one side, -Li + na + , K + Mg 2+ or Ca 2+ A bathtub containing an aqueous solution containing a salt of at least one ion selected from, - A supply device for supplying copper-based sheets to the bathtub, - A first electrode configured to be placed in the bathtub, -Voltage control means configured to apply a first voltage and a second voltage between a copper sheet and a first electrode, wherein the second voltage is inversely relative to the first voltage.

[0066] The systems defined herein can be used to carry out the methods of this disclosure. The inventors have found that the provision of a system as defined herein can be used to produce at least one of graphene and graphene oxide in an advantageous manner. The system can be used to produce at least one of graphene and graphene oxide in a copper-free manner and has been found to be able to produce high-purity, crystalline flakes of at least one of graphene and graphene oxide.

[0067] The system is preferably configured such that a copper-based sheet, coated on at least one side, for example both sides, with a carbonaceous material, is supplied to the bathtub on a first side of the bathtub, moves within the bathtub, and is removed from the bathtub on a second side of the bathtub. The second side is preferably located on the opposite side of the first side.

[0068] The voltage control means may be any device well known to those skilled in the art, configured to apply a first voltage and a second voltage between a copper sheet and a first electrode, the second voltage being inverse to the first voltage. The voltage control means may consist of a potentiostat. Preferably, the voltage control means should be configured to supply the first voltage and the second voltage in a pulse sequence.

[0069] In some embodiments, the carbonaceous material of the system may consist of graphite, a graphene film disposed on an amorphous carbon substrate, and / or a graphene film disposed on a graphite substrate. Copper-based sheets coated on one side with such a carbonaceous material have been found to be particularly advantageous in systems of the concept of the present invention.

[0070] In some embodiments, the system further comprises liquid removal means for removing the aqueous solution and at least one of graphene and graphene oxide from the bathtub. The liquid removal means may be located on the bathtub. Preferably, the liquid removal means comprises an outlet and a valve configured to open and close the outlet. When the valve is opened, the liquid can flow out of the bathtub. The liquid outlet may be in liquid communication with a filter so that at least one of graphene and graphene oxide can be separated from the aqueous solution and at least one of the debris present in the aqueous solution.

[0071] Alternatively, the liquid removal means may consist of a suction device configured to draw the aqueous solution from the bathtub. The suction device may consist of a pump.

[0072] In one embodiment, the supply device comprises at least one powered roller configured to supply a copper sheet and at least one passive roller configured to guide the copper sheet through the bathtub. The powered roller is powered by a motor and configured to drive the metal sheet into, through, and / or out of the bathtub. Preferably, the supply device comprises a pair of powered rollers positioned on opposing sides of the bathtub.

[0073] The passive rollers are configured to guide the copper sheet into the bathtub. The passive rollers can be installed on the inside and outside of the bathtub.

[0074] In some embodiments, the passive roller is configured to be placed in the bathtub and constitutes the first electrode. To ensure good contact between the copper sheet and the first electrode, it is advantageous for the electrode to be placed on the passive roller provided in the bathtub. The first electrode is preferably an inert electrode, such as a precious metal electrode like a platinum electrode.

[0075] The object of the present invention is at least 1 μm 2This can also be achieved by graphene material formed as crystalline and self-supporting hexagonal flakes having an average size of . Surprisingly, the inventors have found that by the method disclosed herein, at least 1 μm 2 We found that a graphene material could be obtained that was formed as crystalline and self-supporting hexagonal flakes with an average size of [size missing].

[0076] In particular, when the carbonaceous material consists of a graphene film disposed on an amorphous carbon substrate, at least 1 μm 2 Hexagonal flakes with crystalline and self-supporting properties having an average size of can be obtained. The carbonaceous material, consisting of a graphene film disposed on an amorphous carbon substrate, is preferably obtained from a lignin source and may be provided on a copper-based sheet by the method disclosed in Patent Document 1. As described herein, the carbonaceous material may also be obtained from a bio-oil source. By removing at least one of graphene and graphene oxide from such a carbonaceous material using the method of this disclosure, at least 1 μm can be obtained. 2 A graphene material is formed as hexagonal flakes with crystalline and self-supporting properties, having an average size of [size not specified]. The hexagonal shape indicates high-purity, crystalline graphene with high conductivity and good mechanical properties, making it suitable for various electrical and electrochemical applications.

[0077] The flake shape is characterized using a scanning electron microscope. Raman spectroscopy can also be used to characterize graphene, for example, by identifying two-dimensional peaks.

[0078] The term "self-supporting" indicates that a flake can support its own weight. As a result, the flake can maintain its shape even though it is not necessarily supported by a substrate. In other words, "self-supporting" can be considered to be the property of not breaking even when subjected to the force of gravity. For example, graphene flakes that can float in the air without a supporting substrate can be considered to possess self-supporting properties, as they do not crack or shatter. Graphene flakes that float in water without cracking or shattering can be considered to possess self-supporting properties. Graphene flakes that float in a solvent without cracking or shattering can be considered to possess self-supporting properties. Therefore, the term "self-supporting" may also refer to flakes that are held together integrally and maintain structural integrity without being supported by, for example, a supporting substrate.

[0079] In some embodiments, the area of ​​a hexagonal flake is defined by six connected line segments, where adjacent segments are connected at six vertices, and the interior angles at each vertex are in the range of 110° to 130°. The term “hexagonal shape” is defined herein as an area defined by six connected line segments, where adjacent segments are connected at six vertices, and the interior angles at each vertex are in the range of 110° to 130°, preferably around 120°.

[0080] In some cases, the flakes are at least 1 μm in size. 2 The average size, for example, 1 μm 2 ~50mm 2 The range, for example, 1 μm 2 ~1mm 2 range or 1mm 2 ~50mm 2 It can have an average size in the range of nanoparticles or at least 50 mm. Generally, graphene materials, especially graphene composites, are nanoparticles or at least 50 mm. 2 They are manufactured as large sheets with an average size of . Nanoparticles generally have low electronic conductivity, and large sheets are disadvantageous for bulk applications. The inventors have found that they can be manufactured with at least 1 μm 2 For example, 1 μm 2 ~50mm2 We have found that by providing flakes according to this disclosure having an average size in the range of [specify range], composite materials exhibiting high conductivity can be obtained. Another advantage is that the flakes are suitable for bulk applications.

[0081] The object of the present invention is also at least 1 μm 2 This is achieved by crystalline and self-supporting flakes with an average size, and the flakes contain multiple crystalline dendrites.

[0082] The inventors have found that at least 1 μm 2 We have found that crystalline and self-supporting flakes having an average size of 1 μm, and having multiple crystalline dendrites, can be obtained by the method disclosed herein. In particular, when the carbonaceous material consists of a graphene film disposed on an amorphous carbon substrate, at least 1 μm 2 Hexagonal flakes with crystalline and self-supporting properties having an average size of can be obtained. When the carbonaceous material consists of graphite, a graphene film disposed on a graphite substrate, and / or a graphene film disposed on an amorphous carbon substrate, at least 1 μm 2 Hexagonal flakes with crystalline and self-supporting properties having an average size of can be obtained. The carbonaceous material, consisting of a graphene film disposed on an amorphous carbon substrate, is preferably obtained from a lignin source and may be provided on a copper-based sheet by the method disclosed in Patent Document 1. By removing at least one of graphene and graphene oxide from such a carbonaceous material using the method of the present disclosure, at least 1 μm can be obtained. 2 A graphene material is formed as crystalline and self-supporting hexagonal flakes having an average size. As described herein, the carbonaceous material can be obtained from a bio-oil source.

[0083] In some cases, the flakes are at least 1 μm in size. 2 The average size, for example, 1 μm 2 ~50mm2 The range, for example, 1 μm 2 ~1mm 2 range or 1mm 2 ~50mm 2 It can have an average size in the range of nanoparticles or at least 50 mm. Generally, graphene materials, especially graphene composites, are nanoparticles or at least 50 mm. 2 They are manufactured as large sheets with an average size of . Nanoparticles generally have low electronic conductivity, and large sheets are disadvantageous for bulk applications. The inventors have found that they can be manufactured with at least 1 μm 2 For example, 1 μm 2 ~50mm 2 We have found that by providing flakes according to this disclosure having an average size in the range of [specify range], composite materials exhibiting high conductivity can be obtained. Another advantage is that the flakes are suitable for bulk applications. [Brief explanation of the drawing]

[0084] [Figure 1A] Figure 1A is a schematic diagram illustrating the intercalation of ions into a carbonaceous material according to the present invention. [Figure 1B] Figure 1B is a schematic diagram showing the exfoliation of at least one of graphene and graphene oxide from a carbonaceous material according to the present invention. [Figure 2] Figure 2 is a schematic diagram showing the system according to the present invention. [Figure 3A] Figure 3A is a scanning electron microscope image showing hexagonal carbon flakes according to the present invention. [Figure 3B] Figure 3B is a scanning electron microscope image showing multiple hexagonal carbon flakes according to the present invention. [Figure 4] Figure 4 is a scanning electron microscope image showing graphene flakes made of dendrites according to the present invention. [Figure 5] Figure 5 is a scanning electron microscope image showing carbonized bio-oil on a copper plate. [Figure 6A] Figures 6A and 6B show scanning electron microscope images of graphene flakes at different magnifications. [Figure 6B] Figures 6A and 6B show scanning electron microscope images of graphene flakes at different magnifications. [Modes for carrying out the invention]

[0085] The present invention will be described with reference to the following drawings: Figures 1A and 1B show schematic diagrams useful for understanding the manufacturing process of at least one of the graphene and graphene oxides of the present invention. Figure 1 schematically shows the step of applying a first voltage between a copper-based sheet and a first electrode so that at least one ion is intercalated into the carbonaceous material. Figure 1A shows the carbonaceous material 101 deposited on the copper-based sheet 103. The carbonaceous material is depicted herein as layers of graphene 101a and 101b bound by fragile forces. When a voltage is supplied between the copper material 103 and the first electrode 105, ions 107 are attracted toward the copper material. + na + , K + Mg 2+ or Ca 2+ When selected, the first voltage is applied such that the copper-based sheet 103 is the negative electrode and the first electrode 105 is the positive electrode. At least some of the ions may intercalate between layers 101a to 101c to form intercalated ions 107a. The size of the ions increases the distance between the graphene layers 101a to 101c and weakens the interlayer bonds.

[0086] Figure 1B shows the situation when a second voltage is applied. The second voltage is the opposite of the first voltage, with the copper sheet 103 acting as the positive electrode and the first electrode 105 as the negative electrode. When the second voltage is applied, the intercalated ions 107 are attracted to the first electrode 105. This causes the ions 107 to move from their intercalation positions. During this movement, the ions mitigate the exfoliation of at least one of graphene and graphene oxide in the form of flakes 107c that are exfoliated from the carbonaceous material.

[0087] Figure 2 is a schematic diagram showing a system 200 for producing at least one of graphene and graphene oxide. The system 200 comprises a copper-based sheet 203 coated with a carbonaceous material 201. The copper-based sheet 203 is wound onto a first roller 211 of a feeder 213, guided into a bath 215 by a first set of passive guide rollers 217a to 217d, and wound onto a second roller 219. The first roller 211 and the second roller 219 are preferably motor-driven so that the copper-based sheet is supplied into the bath 215, transported through the bath 215 by a first set of guide rollers 217a to 217d positioned in the bath and a second set of guide rollers 218a to 218d positioned above the surface of the aqueous solution in the bath, and removed from the bath 215. The bath is Li + na + , K + Mg 2+ or Ca 2+ For example, Ca 2+ The solution includes an aqueous solution containing a salt of at least one ion selected from the following. In the bath, at least one of the passive guide rollers 217a to 217d is positioned as a first electrode 205, which is a platinum electrode. In the illustrated example, a pair of counter electrodes 221a to 221d are positioned.

[0088] While a portion of the copper-based sheet 203 coated with carbonaceous material 201 is in the bath 215, a first voltage is applied between the copper-based sheet 203 and the first electrode 205, causing at least one ion to intercalate into the carbonaceous material 203. Furthermore, while a portion of the copper-based sheet 203 coated with carbonaceous material 201 is in the bath 215, a second voltage, opposite to the first voltage, is applied between the copper-based sheet 203 and the first electrode 205, causing at least one of graphene and graphene oxide to peel off from the carbonaceous material 203.

[0089] The first and second voltages are applied by a voltage control means 223, such as a potentiostat. The voltage control means 223 is configured to apply a first voltage in the range of -8V to -2V, for example, -6V to -2V, and a second voltage in the range of +2V to 12V, for example, +2V to +8V, for example, +2V to +6V.

[0090] The first voltage can be applied for a period of at least 0.5 seconds, for example, a period of 1 to 5 seconds, or at least 1 second.

[0091] The second voltage can be applied for a period of less than 0.15 seconds, for example, less than 0.1 seconds. Preferably, the second voltage is applied for a shorter time than the first voltage to prevent oxidation of the copper.

[0092] The bathtub 215 is further provided with a liquid outlet 225 having a valve 225a. Preferably, the liquid outlet is in liquid communication with a filter 227 via a pump 230, so that the aqueous solution can be filtered through the filter 229 to separate at least one of graphene and graphene oxide from the aqueous solution. The aqueous solution after the graphene has been removed may contain carbonaceous debris and copper ions. A small portion of the copper sheet 203 is thought to have been oxidized by copper ions present in the aqueous solution during the application of the first and second currents.

[0093] After delamination, the copper-based sheet 203 may be cleaned to remove carbonaceous debris from its surface. Cleaning can be carried out using ultrasonic treatment equipment (not shown).

[0094] The cleaned copper sheet 203 is placed in a container 250 containing an electrode 245, an aqueous solution, and copper ions. The copper sheet is exposed to a negative potential 240, which can reduce the amount of copper ions on the copper surface. In this way, a method and system are obtained that minimizes the consumption of the copper substrate.

[0095] Figure 3A shows an annotated scanning electron microscope image of a hexagonal graphene flake according to the present invention. The graphene flake 300 has a region defined by six connected line segments 301 to 306, where adjacent line segments are connected by six vertices 307 to 312, and the interior angle at each vertex is in the range of 110° to 130°, for example, about 120°. The hexagonal shape is thought to indicate highly crystalline and pure graphene. The flake is self-supporting in the sense that it is not placed on a substrate. Alternatively, the flake can support its own weight.

[0096] Figure 3B is a low-magnification microscope image showing several hexagonal graphene flakes.

[0097] Figure 4 is an annotated scanning electron microscope image of graphene flakes made of dendrites according to the present invention. Flake 401 consists of multiple dendrites 402. The dendritic state is considered to be a precursor state of the hexagonal shape shown in Figure 3. The flakes possess self-supporting properties in the sense that they are not placed on a substrate. Alternatively, the flakes can support their own weight.

[0098] Examples Example 1 A carbon-based composite material was prepared as follows: 0.5 grams of softwood lignin obtained by the Lignoboost process, as well as is well known to those skilled in the art, was supplied to a beaker with 0.4 grams of deionized water, 0.05 grams of poly(vinyl alcohol) (PVA) solution (10 mol-% PVA in water), and 1.05 grams of isopropanol to form a slurry. The slurry was then transferred to a ball mill (planetary mill, Palberizet) and ground using grinding balls ranging in diameter from 0.6 to 0.8 mm to a volume approximately twice the weight of the slurry. The slurry was ground in a 5 x 30 minute cycle, with a 15-minute rest period between each grinding cycle. The ground slurry was collected from the mill using 60 ml of a 1:1 solution of isopropanol and water. After grinding, the ground slurry was treated in an ultrasonic bath. The pulverized slurry was electrodeposited onto the copper substrate sheet in the form of copper rolls using a continuous roll-to-roll system, at the same concentration as the pulverization, to obtain a slurry layer that substantially covered both sides of the copper substrate sheet. The slurry was then dried on the copper surface for approximately 30 minutes.

[0099] A copper plate on which the slurry was deposited was then heated in a tubular oven at a reaction temperature of approximately 805°C under an inert atmosphere. The inert atmosphere was created by purging the oven with argon gas. The copper surface on which the slurry was deposited was then exposed to the reaction temperature for approximately 30 minutes. The flow rate of hydrogen gas in the oven was 500 cc / min. After 30 minutes of heating, the oven was purged with argon gas. Following this treatment, an intermediate product consisting of a carbon-based composite material with a graphene film placed on amorphous carbon was placed on the copper substrate sheet.

[0100] Subsequently, a copper roll was placed between the first and second active rollers and rolled in a bath containing an aqueous solution with a CaC concentration of approximately 0.004 M. Four guide rollers were provided in the bath. The guide rollers were provided as platinum electrodes. The copper-based sheet was rolled through the bath on the platinum electrodes. Four counter electrodes were provided in the bath. The platinum electrodes and counter electrodes were connected to a potentiostat that operated in a pulse sequence of a galvanostat. The potentiostat applied a first voltage of -4V between the copper substrate sheet and the platinum electrodes. This caused the Ca in the aqueous solution to... 2+ Ions intercalated between the graphene film and amorphous carbon. A second voltage of +4V, opposite to the first voltage, was then applied between the copper substrate sheet and the platinum electrode. The second voltage extracted at least one of graphene and graphene oxide from the carbon-based composite material as the intercalated ions moved toward the platinum electrode. The first and second voltages were applied alternately in pulses, with each period of the first voltage lasting approximately 1.1 seconds and each period of the second voltage lasting approximately 0.1 seconds. The graphene flakes were removed into the aqueous solution while minimizing copper consumption.

[0101] The aqueous solution was then drained from the bathtub, and graphene and graphene oxide flakes were separated from the solution by passing it through a filter press.

[0102] The copper surface sheet was then passed through an ultrasonic treatment tank, and subsequently through a bath containing an aqueous solution and electrodes. Reduction was performed in the bath to reduce the copper ions oxidized during the application of the first and second voltages back into the copper sheet substrate.

[0103] The obtained graphene and graphene oxide were observed using a scanning electron microscope. As shown in Figures 3A and 3B, at least 1 μm 2 Graphene flakes were obtained that were formed as hexagonal flakes with crystalline and self-supporting properties, having an average size of at least 1 μm. As shown in Figure 4, at least 1 μm 2A crystalline and self-supporting flake with an average size was obtained, and this flake contained multiple crystalline dendrites.

[0104] Example 2 A carbon-based composite material was prepared as follows: 0.5 grams of bio-oil was electrodeposited onto a copper substrate sheet in the form of a copper roll using a continuous roll-to-roll system, obtaining a bio-oil layer that substantially covered both sides of the copper substrate sheet.

[0105] The copper plate from which the bio-oil had been deposited was then heated in a tubular oven at a reaction temperature of approximately 820°C under an inert atmosphere.

[0106] An inert atmosphere was created by purging the oven with argon gas. The copper surface of the bio-oil was then exposed to the reaction temperature for approximately 30 minutes. The hydrogen gas flow rate in the oven was 350 cc / min. After 40 minutes of heating, the oven was purged with argon gas. Following this treatment, an intermediate product consisting of a carbon-based composite material with a graphene film on graphite was placed on the copper substrate sheet.

[0107] The results were confirmed by scanning electron microscopy. Figure 5 is a scanning electron microscope image showing the carbon-based composite material 501 on the copper substrate sheet 502.

[0108] A copper roll was then placed between the first and second active rollers and rolled in a bath containing an aqueous solution with a concentration of approximately 0.001 M of KaSC. Four guide rollers were provided in the bath, and the guide rollers were provided as platinum electrodes. The copper-based sheet was rolled through the bath on the platinum electrodes. Four counter electrodes were provided in the bath. The platinum electrodes and counter electrodes were connected to a potentiostat operated by a pulse sequence of a galvanostat. The potentiostat applied a first voltage of -10V between the copper substrate sheet and the platinum electrodes. This allowed the K in the aqueous solution to be absorbed. +Ions intercalated between the graphene film and graphite, and / or within the graphite. A second voltage of +2V, opposite to the first voltage, was then applied between the copper substrate sheet and the platinum electrode. The second voltage extracted at least one of graphene and graphene oxide from the carbon-based composite material as the intercalated ions moved toward the platinum electrode. The first and second voltages were applied alternately in pulses, with each period of the first voltage being approximately 1.1 seconds and each period of the second voltage being approximately 0.1 seconds. The graphene flakes were removed into the aqueous solution with minimal copper consumption.

[0109] The aqueous solution was then drained from the bathtub, and graphene and graphene oxide flakes were separated from the solution by passing it through a filter press.

[0110] The copper surface sheet was then passed through an ultrasonic treatment tank, and subsequently through a bath containing an aqueous solution and electrodes. Reduction was performed in the bath to reduce the copper ions oxidized during the application of the first and second voltages back into the copper sheet substrate.

[0111] The obtained graphene and graphene oxide were observed using a scanning electron microscope. Scanning electron microscopy confirmed the formation of graphene flakes (see Figures 6A and 6B). Figures 6A and 6B are scanning electron microscope images showing the formed graphene flakes positioned on an SiO2 plate.

[0112] As illustrated in Examples 1 and 2, it has been found that the concept of the present invention relating to graphene separation can be carried out using any carbonaceous material.

[0113] In addition, variations of the disclosed embodiments and examples can be understood and utilized by a person skilled in the art who practices the claimed invention, from a review of the drawings, disclosures, and appended claims. In the claims, the word “including” does not exclude other elements or steps, and the indefinite articles “a” and “an” do not exclude plurals. The mere fact that certain means are described in different dependent claims does not indicate that a combination of these means cannot be used advantageously.

Claims

1. - A step of providing a copper-based sheet, wherein at least one side is covered with a carbonaceous material, and the copper-based sheet is a sheet of copper metal or a copper alloy. -Li ＋ Na ＋ _K ＋ Mg ２＋ or Ca ２＋ The steps include providing a bathtub containing an aqueous solution containing a salt of at least one ion selected from, and placing a first electrode in the bathtub, - The step of putting the copper-based sheet into the bathtub, - The step of applying a first voltage between the copper-based sheet and the first electrode so that at least one ion is intercalated in the carbonaceous material, A method for producing at least one of graphene and graphene oxide, comprising the step of applying a second voltage, which has the opposite polarity to the first voltage, between the copper sheet and the first electrode, such that at least one of graphene and graphene oxide is peeled off from a carbonaceous material.

2. A method for producing at least one of graphene and graphene oxide according to claim 1, wherein the carbonaceous material comprises a graphene film disposed on an amorphous carbon substrate.

3. A method for producing at least one of graphene and graphene oxide according to claim 1, wherein the carbonaceous material is graphite.

4. A method for producing at least one of graphene and graphene oxide according to any one of claims 1 to 3, wherein the copper-based sheet is supplied into the bathtub by a supply device consisting of a plurality of rollers.

5. The method for producing at least one of graphene and graphene oxide according to claim 4, wherein the first electrode is arranged as a roller in the plurality of rollers.

6. A method for producing at least one of graphene and graphene oxide according to any one of claims 1 to 5, further comprising the step of filtering the aqueous solution to recover at least one of graphene and graphene oxide, and providing a filtered aqueous solution containing copper ions.

7. - A method for producing at least one of graphene and graphene oxide according to claim 6, further comprising the step of reducing the copper ions in the filtered aqueous solution on the copper-based sheet.

8. The salt is Na ＋ or Ca ２＋ A method for producing at least one of graphene and graphene oxide according to any one of claims 1 to 7, including

9. At least one of graphene and graphene oxide exfoliated from the carbonaceous material consists of hexagonal graphene flakes having a crystalline and self-supporting property with an average size of at least 1 μm ２ and at least one of graphene and graphene oxide exfoliated from the carbonaceous material consists of graphene flakes having a crystalline and self-supporting property with an average size of at least 1 μm ２ and the flakes have a plurality of dendrites, the method according to any one of claims 1 to 8, wherein at least one of the above is satisfied

10. - A copper-based sheet having one side coated with a carbonaceous material, wherein the copper-based sheet is a sheet of copper metal or a copper alloy, -Li ＋ Na ＋ _K ＋ Mg ２＋ or Ca ２＋ A bathtub containing an aqueous solution containing a salt of at least one ion selected from, - A supply device for supplying the copper-based sheet to the bathtub, - A first electrode configured to be placed in the bathtub, A system for producing at least one of graphene and graphene oxide, comprising: a voltage control means configured to apply a first voltage and a second voltage between the copper-based sheet and the first electrode, wherein the second voltage has the opposite polarity to the first voltage.

11. A system for producing at least one of graphene and graphene oxide according to claim 10, wherein the supply device includes at least one powered roller configured to supply the copper-based sheet and at least one passive roller configured to guide the copper-based sheet through the bathtub.

12. A system for producing at least one of graphene and graphene oxide according to claim 11, wherein the passive roller is configured to be placed in the bathtub, and the passive roller is the first electrode.

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