Graphene separation

Abstract

The present invention relates to a method of producing graphene and / or graphene oxide. The method comprises: providing a copper base sheet coated on one side with a carbonaceous material; providing a tank containing an aqueous solution comprising at least one salt of an ion selected from Li + , Na + , K + , Mg 2+ or Ca 2+ , a first electrode being arranged in the tank; feeding the copper base sheet into the tank; applying a first voltage between the copper base sheet and the first electrode; applying a second voltage, opposite to the first voltage, between the copper base sheet and the first electrode, such that 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 platelets. The present invention also relates to a graphene material formed as crystalline self-supporting platelets comprising dendrites.

Description

Technical Field

[0001] The present invention relates to a method for producing graphene and / or graphene oxide, a system for producing graphene and / or graphene oxide, and graphene materials formed as self-supporting crystalline sheets. Background Technology

[0002] Two-dimensional materials, and especially graphene, have attracted considerable attention since their first synthesis in the early 21st century, primarily due to their mechanical, electronic, and optical properties. The use of graphene materials in a variety of applications has steadily increased since their discovery. Several methods have been proposed for the fabrication of graphene, including chemical vapor deposition (CVD) and exfoliation.

[0003] Graphene or graphene composites can be produced on metal substrates, such as copper substrates. WO 2019 / 180227A1 discloses a method for producing carbon composite materials on metal surfaces, such as copper surfaces, comprising a graphene film disposed on an amorphous carbon substrate. WO 2019 / 180227 A1 discloses that the composite sheet can be removed from the copper substrate by, for example, dissolving copper using a strong acid or by electro-delamination. The disclosed electro-delamination involves using copper as a first electrode, a graphite electrode as a second electrode, and a 0.05M NaOH solution as an electrolyte, followed by a 25 mA / cm²... 2 A current is applied to the electrodes. The copper electrodes are then transferred to a container of MilliQ water, which removes the film from the composite material.

[0004] However, there is a current need in the art for a preferred method to produce pure and crystalline graphene and / or graphene oxide from carbonaceous materials disposed on a copper substrate without consuming the copper substrate. Summary of the Invention

[0005] The object of this invention is to at least alleviate some of the problems associated with the prior art. In particular, the object of this invention is to provide an improved method for producing pure and crystalline graphene and / or graphene oxide from carbonaceous materials deposited on a metal substrate, preferably a copper substrate. The object is to provide a method for producing graphene and / or graphene oxide that does not consume a metal substrate and provides pure sheets of crystalline graphene and / or graphene oxide. These and other objects are achieved by a method for producing graphene and / or graphene oxide comprising the following steps:

[0006] - Provide a copper-based sheet coated with a carbonaceous material on at least one side;

[0007] - Provides a tank containing an aqueous solution, the aqueous solution containing at least one component selected from Li + Na + K+ Mg 2+ or Ca 2+ The salt of ions, with the first electrode arranged in the tank;

[0008] - The copper-based sheet is supplied to the tank;

[0009] - Apply a first voltage between the copper-based sheet and the first electrode, causing the at least one ion to embed into the carbonaceous material;

[0010] - Applying a second voltage, which is opposite to the first voltage, between the copper-based sheet and the first electrode, causes graphene and / or graphene oxide to be peeled off from the carbonaceous material.

[0011] According to one aspect of the present invention, a method for producing graphene and / or graphene oxide is provided, the method comprising the following steps:

[0012] - Provide a copper-based sheet coated with a carbonaceous material on at least one side;

[0013] - A tank containing an aqueous solution is provided, the aqueous solution containing at least one salt of ions selected from Li+, Na+, K+, Mg2+ or Ca2+, and a first electrode is arranged in the tank;

[0014] - The copper-based sheet is supplied to the tank;

[0015] - A first voltage is applied between the copper-based sheet and the first electrode, thereby embedding at least one ion into the carbonaceous material;

[0016] - A second voltage, which is opposite to the first voltage, is applied between the copper-based sheet and the first electrode to peel graphene and / or graphene oxide from the carbonaceous material.

[0017] The advantage of the method for producing graphene and / or graphene oxide is that it provides a way to produce pure, crystalline, high-quality graphene and / or graphene oxide without consuming copper sheets.

[0018] This invention is based on the understanding that graphene and / or graphene oxide can be produced by a method involving the embedding of large alkali metal or alkali metal ions into a carbonaceous material disposed on a copper substrate. Ion embedding is improved by applying a voltage between the copper substrate and an electrode, which causes positive ions to travel toward the copper substrate sheet and embed between the graphene sheets in the carbonaceous material. This embedding extends the distance between the graphene sheets in the carbonaceous material, thereby weakening the forces holding the material together. When the voltage between the copper substrate and the electrode is reversed, the embedded ions travel from their embedding sites in the carbonaceous material, causing the graphene and / or graphene oxide to be removed by peeling from the carbonaceous material.

[0019] The method of the present invention involves feeding a copper-based sheet coated with a carbonaceous material on at least one side, such as both sides, into a tank containing an aqueous solution, the aqueous solution comprising at least one component selected from Li. + Na + K + Mg 2+ or Ca 2+ The tank should preferably be free of any solution that would dissolve or otherwise damage the copper substrate, such as strong acids. Therefore, a method can be obtained to remove graphene and / or graphene oxide from carbonaceous materials deposited on a copper substrate without consuming the copper substrate.

[0020] Preferably, the copper-based sheet is fed through the trough by a feeding device configured to feed the copper-based sheet into the trough for a two-step process of embedding and peeling. Then, after the two-step process, the feeding device removes the copper-based sheet from the trough. This can be achieved, for example, in a manner similar to how a continuous paper web travels in a paper machine. The copper-based sheet is attached between a first roll and a second roll. The copper-based sheet is arranged to travel through the trough via a set of support guide rolls disposed in the trough. Thus, a continuous process can be achieved, in which new portions of the copper-based sheet are continuously fed into the trough via the first and second rolls, undergo the two-step process, and are removed from the trough by the rolls. Simultaneously, new portions of the copper-based sheet are fed into the trough. This process is preferably continuous for the length of the copper-based sheet.

[0021] The process involves a two-step process of embedding and stripping, achieved by applying a first voltage between an electrode positioned in a trench and a copper sheet. This voltage can be obtained by placing a copper-based sheet in contact with the electrode, such as an inert electrode or a platinum electrode. The first voltage is then applied between the copper-based sheet and a counter electrode in the trench using a voltage control device. Since the ions to be embedded are positively charged, the first voltage is chosen to attract positive ions to the copper-based sheet, thereby improving the embedding of positive ions into the carbonaceous material. After embedding, the voltage is reversed compared to the first voltage, causing the embedded ions to be attracted by the counter electrode, which improves the stripping of graphene and / or graphene oxide from the carbonaceous material. The graphene and / or graphene oxide removed from the carbonaceous material has been found to be pure and highly crystalline.

[0022] The first voltage can be in the range of -8V to -2V, for example, in the range of -6V to -2V. The first voltage can be applied for a period of at least 0.5 seconds, for example, a period of at least 1 second, for example, a period of 1 to 5 seconds.

[0023] Alternatively, the first voltage can be in the range of -30V to -2V, such as in the range of -12V to -2V, such as in the range of -10V to -2V, such as in the range of -8V to -2V, such as in the range of -6V to -2V. Alternatively, the first voltage can be -2V or lower.

[0024] The second voltage can 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 to avoid the risk of copper oxidation.

[0025] Alternatively, the second voltage can be in the range of +0.3V to +12V, such as in the range of +0.5V to +12V, such as in the range of +2V to +12V, such as in the range of +2V to +10V, such as in the range of +2V to +8V. Alternatively, the second voltage can be +0.3V or higher.

[0026] The inventors have recognized that a +12V upper limit for the second voltage may be sufficient when using copper-based sheets. Furthermore, it has been recognized that the lower limit of the first voltage (i.e., the negative voltage with the largest absolute value) should preferably be selected considering one or more setting parameters, such as the thickness and capacity of the leads connected to the voltage control device (e.g., to avoid melting the leads), the volume of the aqueous solution, and the salt concentration. It has been recognized that in some cases, the method conceived according to the invention can be performed with a first voltage below -30V.

[0027] Furthermore, it should be understood that the lower and upper limits of the disclosed first voltage range can be combined to form a range not explicitly stated 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 a range not explicitly stated in this disclosure.

[0028] The voltage control device is preferably configured accordingly to provide the voltage disclosed above.

[0029] During the movement of the copper-based sheet in the trench, several two-step processes of embedding and peeling can be performed, subjecting the same carbonaceous material to a voltage sequence that begins with a first voltage, followed by a second voltage, then a first voltage, and then a second voltage. This process can be repeated continuously until graphene and / or graphene oxide have been satisfactorily removed from the copper-based sheet.

[0030] In this document, the term "graphene" refers to two-dimensional carbon materials known to those skilled in the art. The term is also intended to refer to so-called "few-layer graphene," which refers to materials comprising a stack of 2-10 graphene layers.

[0031] In this document, the term "graphene oxide" refers to oxidized graphene, as is known to those skilled in the art, i.e., two-dimensional carbon material that has been oxidized. It is also intended to refer to oxidized few-layer graphene.

[0032] In this document, the term "copper-based sheet" is intended to refer to a sheet of copper metal or a copper alloy. The copper-based sheet can be provided as a foil. The sheet is preferably thin enough that it can be rolled around a roller included in the supply apparatus disclosed herein. The sheet may preferably have a thickness much smaller than its width. The width should preferably be much smaller than the length of the sheet.

[0033] The term "coating on one side" refers to providing a carbonaceous material on at least one side of a copper-based sheet. The coating does not need to completely cover the sheet. The coating may also be provided on both sides of the copper-based sheet.

[0034] The term "carbonaceous material" refers to a carbonaceous material from which graphene can be exfoliated using this invention. The carbonaceous material of the present invention may include bonded graphene and / or graphene oxide materials. The carbonaceous material may include graphite sheets comprising graphene bonded in a stacked manner. The carbonaceous material may alternatively or additionally include carbon composite materials comprising graphite, graphene films disposed on a graphite substrate, and / or graphene films disposed on an amorphous carbon substrate. The carbonaceous material may include graphite, graphene films disposed on a graphite substrate, and / or graphene films disposed on an amorphous carbon substrate. In the method of the present invention, the bonded graphene in the carbonaceous material is removed by an embedding / exfoliation method. The carbonaceous material may contain at least 80% by weight of carbon, such as at least 90% by weight of carbon, such as at least 95% by weight of carbon, such as being substantially composed of carbon by weight. Therefore, the present invention provides a method for separating graphene and / or graphene oxide from a carbonaceous material disposed on a copper-based sheet. In principle, by repeating the embedding / peeling process, each embedding / peeling cycle can peel off one layer of graphene and / or graphene oxide.

[0035] Therefore, the method of the present invention can be considered advantageously flexible, since graphene and / or graphene oxide can be produced from a variety of different carbonaceous materials.

[0036] The term "contains at least one selected from Li" + Na + K + Mg 2+ or Ca 2+ "An aqueous solution of a salt containing Li+ ions" refers to the solution containing Li+ ions, which is obtained by supplying water or a solution containing mostly water with an aqueous solution. + Na + K + Mg 2+ or Ca2+ The composition is formed by the salt. In this document, the aqueous solution may not contain strong acids such as HCl, H₂SO₄, and HNO₃. It may also not contain other components known to degrade copper. Preferably, the aqueous solution contains Ca. 2+ Or Na + It is anticipated that during intercalation, larger ions will provide increased separation between adjacent graphene sheets in the carbonaceous material, thereby improving exfoliation. The concentration of ions in the trench can be at least 0.001 M, in the range of 0.001-0.1 M, such as in the range of 0.001-0.01 M, such as in the range of 0.002 M to 0.006 M.

[0037] The "first electrode" can refer to an inert electrode, such as a platinum electrode. The first electrode can be arranged as a roller positioned in a groove and configured to guide the copper sheet as it travels through the groove. This provides good conductive contact between the electrode and the copper substrate, allowing a voltage to be applied between them.

[0038] At least one counter electrode can be placed in the tank.

[0039] In some implementations, the carbonaceous material includes a graphene film disposed on an amorphous carbon substrate.

[0040] WO 2019 / 180227 A1 discloses a method for producing composite materials on metal surfaces, such as copper surfaces, comprising a graphene film disposed on an amorphous carbon substrate. The method disclosed herein can be provided to produce graphene and / or graphene oxide sheets from the composite material in an improved manner, providing high yields of graphene and / or graphene oxide without consuming copper-based sheets.

[0041] Carbonaceous materials can be obtained from bio-oils and / or from lignin sources, such as refined lignin, purified lignin, alkali lignin, and lignin sulfonates.

[0042] The term "bio-oil," sometimes referred to as pyrolysis oil, tar, or bio-crude oil, refers to oil that can be obtained from feedstocks such as rapeseed, coniferous trees such as pine, fir, and spruce, as well as microalgal lipids, or their residual products. Therefore, bio-oil can be considered a renewable resource that advantageously allows for environmentally friendly methods.

[0043] It is anticipated that during the application of the first voltage, ions provided in the trench will be intercalated between the graphene film and the amorphous carbon substrate. When the second voltage is applied, a minimum thickness of 1 μm is preferred. 2 Graphene flakes of average size are peeled from the composite material. When the graphene film includes few-layer graphene, intercalation is also expected between the graphene layers in the few-layer graphene.

[0044] Graphene can be exfoliated to have an average size of at least 1 μm. 2 Graphene oxide can be peeled into thin sheets with smaller dimensions.

[0045] The inventors unexpectedly discovered that a portion of the exfoliated graphene could be formed into hexagonal flakes. These hexagonal flakes were expected to indicate high-purity crystalline graphene. The advantage of such flakes lies in their high electrical conductivity, making them suitable for a wide range of electrical and electrochemical applications.

[0046] The inventors further discovered that a portion of graphene can form thin sheets including dendrites. The dendrite shape is expected to be a precursor to hexagonal sheets.

[0047] In some embodiments, the method may further include the following prior steps: providing 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. The method can be carried out using heating temperatures and other method conditions as described in WO 2019 / 180227 A1, preferably at temperatures of 500°C to 1100°C. The reaction temperature can also be in the range of 600°C to 1000°C, such as in the range of 700°C to 900°C, preferably in the range of 750°C to 850°C, more preferably in the range of 790°C to 815°C, for example, about 805°C. The reaction time is typically less than one hour, such as less than 50 minutes, preferably in the range of 10 to 50 minutes, such as about 30 minutes or about 20 minutes, which corresponds to the time it takes for the composition to manifest on the copper-based sheet with respect to the reaction temperature.

[0048] In some embodiments, the method may further include the following prior steps: 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. The method can be carried out using heating temperatures and other method conditions as described in WO 2019 / 180227 A1, preferably at temperatures of 500°C to 1100°C. The reaction temperature can also be in the range of 600°C to 1000°C, such as in the range of 700°C to 900°C, preferably in the range of 750°C to 850°C, more preferably in the range of 790°C to 815°C, for example, about 805°C. The reaction time is typically less than one hour, such as less than 50 minutes, preferably in the range of 10 to 50 minutes, such as about 30 minutes or about 20 minutes, which corresponds to the time it takes for the bio-oil to manifest on the copper-based sheet with respect to the reaction temperature.

[0049] Carbon composite materials may include graphite, graphene films disposed on graphite substrates, and / or graphene films disposed on amorphous carbon substrates.

[0050] The inventors have unexpectedly recognized that, for example, the inventive concept involving graphene separation can be carried out using any carbonaceous material. Preferably, the carbonaceous material includes graphite, a graphene film disposed on a graphite substrate, and / or a graphene film disposed on an amorphous carbon substrate.

[0051] Although the method steps discussed on page 8, lines 27-30 to page 9, lines 1-10 utilize lignin to provide carbonaceous materials, such as carbon composites, other alternatives are possible within the scope of the inventive concept, such as using bio-oils to provide carbonaceous materials, such as the carbon composites disclosed in Example 2.

[0052] In some embodiments, the carbonaceous material includes graphite. Graphite is a material that, by definition, comprises stacked sheets of graphene held together by interlayer forces, such as weak van der Waals bonds. The method of the present invention allows ions in an aqueous solution to intercalate and exfoliate between graphene layers in a graphene material. It has been recognized that when the carbonaceous material includes graphite, graphene and / or graphene oxide can be exfoliated in the form of flakes.

[0053] In some embodiments, the copper-based sheet is fed into a trough via a feeding device comprising multiple rollers. A first roller may be arranged at a first end of the trough, and a second roller may be arranged at a second, opposite end of the trough. At least one of the first and second rollers may be motorized, thereby enabling the copper-based sheet to be automatically fed into and passed through the trough. The multiple rollers may also include at least one guide roller disposed in the trough, configured to guide the copper-based sheet through the trough. The guide roller may be a passive roller.

[0054] In some embodiments, the first electrode is arranged as one of a plurality of rollers. The first electrode can be an inert electrode, such as a noble metal electrode, preferably a platinum electrode. This electrode is preferably arranged in a guide roller. Therefore, good conductive contact can be achieved between the electrode and the copper-based sheet.

[0055] In some implementations, the method further includes the following steps:

[0056] - The aqueous solution is filtered to collect graphene and / or graphene oxide and provide a filtered aqueous solution optionally containing copper ions. After the step of applying a second voltage, the exfoliated graphene and / or graphene oxide remains in the aqueous solution in the tank. The graphene and / or graphene oxide can be separated from the aqueous solution in a filter such as a filter press. The filter can be configured to separate the graphene and / or graphene oxide from other types of carbonaceous residues in the aqueous solution, such as amorphous carbon.

[0057] The tank may include a liquid outlet for discharging liquid from the tank. This liquid outlet may be connected to a filter liquid for performing the filtration described above.

[0058] The steps of applying the first and second voltages can oxidize some copper to Cu. 2+ Therefore, Cu 2+ It may be present in aqueous solutions.

[0059] In some embodiments, the method further includes a step of cleaning the copper-based sheet using ultrasonic treatment. After the graphene or graphene oxide has been separated, ultrasonic treatment can be used to remove carbonaceous residues from the copper-based sheet.

[0060] In some implementations, the method further includes the following steps:

[0061] - Reduce copper ions from the filtered aqueous solution on the copper-based sheet. This step can be performed if any copper from the copper-based sheet has been oxidized and is present as copper ions in the aqueous solution. The copper-based sheet can be pre-cleaned to remove carbonaceous residues. The advantage of this step is that it minimizes the consumption of copper-based sheet material.

[0062] In some embodiments, the method may further include the step of centrifuging and collecting graphene and / or graphene oxide.

[0063] The obtained graphene and / or graphene oxide can be provided in the form of sheets, preferably having a thickness of at least 1 μm. 2 The size of the graphene and / or graphene oxide can be determined by centrifugation.

[0064] In some implementations, the salt contains Na. + and / or Ca 2+ Larger ions are preferred because, compared to smaller ions, they are thought to cause greater expansion of the distance between graphene layers in carbonaceous materials during intercalation. This is expected to improve the exfoliation process, as the interlayer bonds in carbonaceous materials will be weaker.

[0065] In some implementations, the pH in the tank is at least 6. It is advantageous to avoid acidic solutions in the tank, as acids can consume the copper-based sheet.

[0066] In some embodiments, the graphene and / or graphene oxide exfoliated from the carbonaceous material comprises graphene with an average size of at least 1 μm. 2 Crystallized self-supporting hexagonal thin sheets.

[0067] The inventors unexpectedly discovered that the graphene and / or graphene oxide produced by this method are highly crystalline and pure. This is exemplified by the fact that the graphene and / or graphene oxide can include an average size of at least 1 μm. 2The crystals are self-supporting hexagonal sheets. The term "self-supporting" means that the sheets can support their own weight. The shape can be determined using microscopy techniques such as scanning electron microscopy.

[0068] In particular, when carbonaceous materials include graphene films arranged on an amorphous carbon substrate, hexagonal flakes are produced.

[0069] In some embodiments, the graphene and / or graphene oxide exfoliated from the carbonaceous material comprises crystalline self-supporting sheets, preferably having a thickness of at least 1 μm. 2 The average size of these flakes indicates that they have multiple dendrites. This can also be used as an indicator that the produced graphene and / or graphene oxide is highly crystalline and pure. The expected dendrite shape is a hexagonal precursor.

[0070] Preferably, the dendritic sheet is formed of graphene.

[0071] Preferably, the hexagonal sheets are formed of graphene.

[0072] The object of the present invention is also achieved by a system for producing graphene and / or graphene oxide, the system comprising:

[0073] - A copper-based sheet coated with a carbonaceous material on at least one side;

[0074] - A tank containing an aqueous solution, the aqueous solution containing at least one component selected from Li + Na + K + Mg 2+ or Ca 2+ Salts of ions;

[0075] - A supply device for feeding the copper-based sheet into the tank;

[0076] - Configured as the first electrode arranged in the slot;

[0077] - A voltage control device configured to apply a first voltage and a second voltage between the copper-based sheet and the first electrode, wherein the second voltage is inversely proportional to the first voltage.

[0078] The system as defined herein can be used to perform the methods disclosed herein. The inventors have discovered that the system provided herein can be used to advantageously produce graphene and / or graphene oxide. It has been found that the system can be used to produce graphene and / or graphene oxide in a manner that does not consume copper and produces high-purity and crystalline flakes of graphene and / or graphene oxide.

[0079] The system is preferably arranged such that a copper-based sheet coated with a carbonaceous material on at least one side (e.g., both sides) can be fed into the tank on a first side, travel through the tank, and be removed from the tank on a second side. The second side is preferably arranged opposite to the first side.

[0080] The voltage control device can be any device known to those skilled in the art, configured to apply first and second voltages between the copper substrate and the first electrode, wherein the second voltage is inversely proportional to the first voltage. The voltage control device may include a voltage regulator. Preferably, the voltage control device should be configured to provide the first and second voltages in a pulse sequence.

[0081] In some embodiments, the carbonaceous material of the system includes graphite, a graphene film disposed on an amorphous carbon substrate, and / or a graphene film disposed on a graphite substrate. It has been recognized that copper-based sheets coated with such carbonaceous material on one side are particularly advantageous in the systems conceived in this invention.

[0082] In some embodiments, the system further includes a liquid removal device for removing the aqueous solution and graphene and / or graphene oxide from the tank. The liquid removal device may be arranged on the tank. Preferably, the liquid removal device includes an outlet and a valve configured to open and close the outlet. When the valve is open, liquid can flow out of the tank. The liquid outlet may be connected to a filter liquid, allowing the graphene and / or graphene oxide to be separated from the aqueous solution and / or debris present in the aqueous solution.

[0083] The liquid removal apparatus may also include a suction device configured to draw the aqueous solution from the tank. The suction device may include a pump.

[0084] In some embodiments, the feeding device includes at least one driven roller and at least one driven roller, the driven roller being configured to feed copper-based sheet and the driven roller being configured to guide the copper-based sheet through a slot. The driven roller may be powered by a motor and configured to drive the metal-based sheet into, through, and / or out of the slot. Preferably, the feeding device includes a pair of driven rollers arranged on opposite sides of the slot.

[0085] The passive roller is configured to guide the copper-based sheet through the groove. The passive roller can be located inside or outside the groove.

[0086] In some embodiments, the passive roller is configured to be arranged in a groove including the first electrode. If the electrode is arranged in the passive roller disposed in the groove, it is advantageous to provide good contact between the copper-based sheet and the first electrode. The first electrode is preferably an inert electrode, such as a noble metal electrode, like a platinum electrode.

[0087] The present invention also aims to form an average size of at least 1 μm. 2This is achieved by forming graphene materials with crystalline self-supporting hexagonal sheets. The inventors have unexpectedly realized that the method disclosed herein can yield graphene materials with an average size of at least 1 μm. 2 Graphene materials consisting of crystalline, self-supporting hexagonal sheets. In particular, when the carbonaceous material includes a graphene film disposed on an amorphous carbon substrate, an average size of at least 1 μm can be obtained. 2 The crystalline self-supporting hexagonal sheets are formed. The carbonaceous material, comprising a graphene film disposed on an amorphous carbon substrate, can preferably be obtained from a lignin source and is provided on a copper-based sheet by the method disclosed in WO 2019 / 180227 A1. As described herein, the carbonaceous material can be obtained from a bio-oil source. When graphene and / or graphene oxide are removed from such carbonaceous material using the method disclosed herein, a layer is formed having an average size of at least 1 μm. 2 Graphene materials consisting of crystalline, self-supporting hexagonal sheets. The hexagonal shape is expected to indicate high-purity and crystalline graphene with high electrical conductivity and good mechanical properties, making it suitable for a variety of electrical and electrochemical applications.

[0088] The shape of the flakes can be characterized using scanning electron microscopy. Raman spectroscopy can be further used to characterize graphene, for example, by identifying 2D peaks.

[0089] The term "self-supporting" means that a sheet can support its own weight. Therefore, the sheet does not need to be supported by any substrate, but can maintain its shape. In other words, "self-supporting" can be considered a property that allows it to withstand gravity without breaking. For example, a graphene sheet that can suspend in air without breaking or fracturing can be considered self-supporting. A graphene sheet that suspends in water without breaking or fracturing can be considered self-supporting. A graphene sheet that suspends in a solvent without breaking or fracturing can be considered self-supporting. Therefore, the term self-supporting can refer to sheets that remain together and maintain structural integrity without being supported by, for example, a substrate.

[0090] In some embodiments, the region of the hexagonal sheet is defined by six connecting line segments, wherein adjacent line segments are connected at the six vertices, and wherein the interior angle at each vertex is in the range of 110°–130°. The term "hexagonal shape" is defined herein as a region defined by six connecting line segments, wherein adjacent line segments are connected at the six vertices, and wherein the interior angle at each vertex is in the range of 110°–130°, preferably about 120°.

[0091] In some embodiments, the sheet may have a thickness of at least 1 μm. 2 For example, at 1μm 2 -50 mm 2 Within a range, for example, within 1μm2 Within -1 mm or within 1 mm 2 -50 mm 2 The average size within the range. Typically, graphene materials, and especially graphene composites, are produced as nanoparticles or with an average size of at least 50 mm. 2 Large sheets are used. Nanoparticles typically have poor electron conductivity, and large sheets are disadvantageous in mass production applications. The inventors have discovered that by providing an average size of at least 1 μm according to this disclosure, nanoparticles can be used in mass production applications. 2 For example, 1μm 2 -50mm 2 Thin sheets within this range can be used to obtain composite materials exhibiting high electrical conductivity. Another advantage is that the thin sheets are suitable for mass production applications.

[0092] Another objective of this invention is to achieve an average size of at least 1 μm. 2 The crystallization of self-supporting thin sheets is achieved, and these sheets have multiple crystal dendrites.

[0093] The inventors have recognized that an average size of at least 1 μm can be obtained using the methods disclosed herein. 2 Crystalline self-supporting sheets with multiple crystal dendrites. In particular, when the carbonaceous material includes graphene films arranged on an amorphous carbon substrate, an average size of at least 1 μm can be obtained. 2 Crystalline self-supporting hexagonal sheets. When the carbonaceous material includes graphite, graphene films disposed on a graphite substrate, and / or graphene films disposed on an amorphous carbon substrate, an average size of at least 1 μm can be obtained. 2 The crystalline self-supporting hexagonal sheets are formed. The carbonaceous material, including a graphene film disposed on an amorphous carbon substrate, can preferably be obtained from a lignin source and is provided on a copper-based sheet by the method disclosed in WO 2019 / 180227 A1. When graphene and / or graphene oxide are removed from such carbonaceous material using the method disclosed herein, a layer is formed with an average size of at least 1 μm. 2 Graphene materials consisting of crystalline, self-supporting hexagonal flakes. As described in this article, carbonaceous materials can be obtained from bio-oil sources.

[0094] In some embodiments, the sheet may have a thickness of at least 1 μm. 2 For example, at 1μm 2 -50 mm 2 Within a range, for example, within 1μm 2 Within -1 mm or within 1 mm 2 -50 mm 2 The average size within the range. Typically, graphene materials, and especially graphene composites, are produced as nanoparticles or with an average size of at least 50 mm. 2Large sheets are used. Nanoparticles typically have poor electron conductivity, and large sheets are disadvantageous in mass production applications. The inventors have discovered that by providing an average size of at least 1 μm according to this disclosure, nanoparticles can be used in mass production applications. 2 For example, 1μm 2 -50mm 2 Thin sheets within this range can be used to obtain composite materials exhibiting high electrical conductivity. Another advantage is that the thin sheets are suitable for mass production applications. Attached Figure Description

[0095] The invention will be described with reference to the following figures, in which:

[0096] Figure 1a is a schematic diagram of the ion-intercalated carbonaceous material according to the present invention.

[0097] Figure 1b is a schematic diagram of the process of peeling graphene and / or graphene oxide from carbonaceous materials according to the present invention.

[0098] Figure 2 This is a schematic diagram of the system according to the present invention.

[0099] Figure 3a is a scanning electron microscope image of a hexagonal carbon sheet according to the present invention.

[0100] Figure 3b is a scanning electron micrograph of several hexagonal carbon sheets according to the present invention.

[0101] Figure 4 This is a scanning electron microscope image of a graphene sheet including dendrites according to the present invention.

[0102] Figure 5 This is a scanning electron micrograph of carbonized bio-oil on a copper plate.

[0103] Figures 6a-6b These are scanning electron micrographs of graphene sheets at different magnifications. Detailed Implementation

[0104] Figures 1a and 1b illustrate schematic diagrams of a method for producing graphene and / or graphene oxide that can be used to understand the present invention. In Figure 1, the step of applying a first voltage between a copper substrate and a first electrode is schematically shown, causing at least one ion to embed in the carbonaceous material. Figure 1a shows carbonaceous material 101 deposited on a copper substrate 103. The carbonaceous material is described herein as graphene layers 101a-b held together by weak forces. When a voltage is applied between the copper material 103 and the first electrode 105, ions 107 are attracted to the copper material. Given that the ions are selected from Li... + Na + K + Mg 2+ or Ca 2+A first voltage is applied, making the copper-based sheet 103 the negative electrode and the first electrode 105 the positive electrode. At least some ions can embed between layers 101a-c and form embedded ions 107a. The size of the ions will increase the distance between the graphene layers 101a-c, which weakens the bonding between them.

[0105] Figure 1b illustrates the situation when a second voltage is applied. This second voltage is reversed compared to the first voltage, making the copper-based sheet 103 the positive electrode and the first electrode 105 the negative electrode. When the second voltage is applied, the embedded ions 107 are attracted to the first electrode 105. This causes them to travel from their embedding sites. During this travel, the ions will improve the exfoliation of graphene and / or graphene oxide in the form of sheets 107c, which are then peeled from the carbonaceous material.

[0106] Figure 2 A schematic diagram of a system 200 for producing graphene and / or graphene oxide is shown. System 200 includes a copper-based sheet 203 coated with a carbonaceous material 201. The copper-based sheet 203 is rolled onto a first roller 211 in a feeding device 213, guided through a trough 215 by a first set of passive guide rollers 217a-d, and rolled upwards onto a second roller 219. The first roller 211 and the second roller 219 are preferably motorized, allowing the copper-based sheet to be fed into the trough 215, conveyed through the trough 215 by the first set of guide rollers 217a-d arranged in the trough and the second set of guide rollers 218a-d arranged above the surface of the aqueous solution in the trough, and removed from the trough 215. The trough contains an aqueous solution comprising at least one component selected from Li. + Na + K + Mg 2+ or Ca 2+ Ions in (such as Ca) 2+ The salt. In the tank, at least one of the passive guide rollers 217a-d is arranged as a first electrode 205, which is a platinum electrode. In the example shown in the schematic diagram, a set of counter electrodes 221a-d are arranged.

[0107] During the period when a portion of the copper-based sheet 203 coated with carbonaceous material 201 is in the trench 215, a first voltage is applied between the copper-based sheet 203 and the first electrode 205, causing at least one ion to be embedded in the carbonaceous material 203. Furthermore, during the period when a portion of the copper-based sheet 203 coated with carbonaceous material 201 is in the trench 215, a second voltage, opposite to the first voltage, is applied between the copper-based sheet 203 and the first electrode 205, causing graphene and / or graphene oxide to be peeled off from the carbonaceous material 203.

[0108] The first and second voltages are applied by a voltage control device 223, such as a voltage regulator. The voltage control device 223 is configured to apply a first voltage in the range of -8V to -2V, such as in the range of -6V to -2V, and a second voltage in the range of +2V to 12V, such as in the range of +2V to +8V, such as in the range of +2V to +6V.

[0109] The first voltage can be applied for a period of at least 0.5 seconds, such as at least 1 second, such as a period of 1 to 5 seconds.

[0110] The second voltage can be applied for a period of less than 0.15 seconds, such as less than 0.1 seconds. Preferably, the second voltage is applied for a shorter time than the first voltage to avoid the risk of copper oxidation.

[0111] Tank 215 is further provided with a liquid outlet 225 having a valve 225a. The liquid outlet is preferably liquid-connected to filter 227 via pump 230, so that the aqueous solution can be filtered in filter 229 to separate graphene and / or graphene oxide from the aqueous solution. After the graphene has been removed, the aqueous solution may contain carbonaceous debris and copper ions. It is anticipated that during the application of the first and second currents, a small portion of the copper-based sheet 203 has been oxidized to copper ions now present in the aqueous solution.

[0112] After peeling, the copper-based sheet 203 can be cleaned to remove carbonaceous debris from its surface. Cleaning can be performed using an ultrasonic treatment device (not shown).

[0113] A cleaned copper-based sheet 203 can be supplied to a container 250 containing an electrode 245, an aqueous solution, and copper ions. The copper-based sheet is then subjected to a negative potential 240 capable of reducing copper ions on the copper surface. This provides a method and system for supplying a copper substrate with minimal consumption.

[0114] Figure 3a shows an annotated scanning electron micrograph of a hexagonal graphene sheet according to the present invention. The graphene sheet 300 has a region defined by six connected line segments 301-306, wherein adjacent line segments are connected at six vertices 307-312, and wherein the interior angle at each vertex is in the range of 110-130°, for example, about 120°. The hexagonal shape is intended to indicate highly crystalline and pure graphene. The sheet is self-supporting in the sense that it is not provided on a substrate. Alternatively, it can support its own weight.

[0115] Figure 3b shows a low-magnification micrograph depicting several hexagonal graphene flakes.

[0116] Figure 4Annotated scanning electron micrographs of a graphene sheet comprising dendrites according to the present invention are shown. The sheet 401 comprises a plurality of dendrites 402. The desired dendritic state is a precursor state with a hexagonal shape as shown in Figure 3. The sheet is self-supporting in the sense that it is not provided on a substrate. Alternatively, it can support its own weight.

[0117] Example

[0118] Example 1

[0119] Carbon-based composite materials were prepared as follows: 0.5 g of cork lignin from the Lignoboost method, known to those skilled in the art, was provided in a beaker with 0.4 g of deionized water, 0.05 g of poly(vinyl alcohol) (PVA) solution (10 mol% PVA aqueous solution), and 1.05 g of isopropanol to form a slurry. The slurry was then transferred to a ball mill (Planetary Mill Pulverisette) where it was ground using grinding balls with a diameter in the range of 0.6–0.8 mm at a volume approximately twice the weight of the slurry. The slurry was ground at a rate of 5 × 30 minutes, with a 15-minute rest period between each grinding repetition. The ground slurry was then collected from the mill using a 1:1 solution of 60 ml isopropanol and water. After grinding, the ground slurry was treated in an ultrasonic bath. The ground slurry was electrocoated onto a copper substrate sheet in the form of a copper roll in a continuous roll-to-roll system at the same concentration as the ground slurry to obtain a slurry layer that substantially covers both sides of the copper substrate sheet. Then allow the slurry to dry on the copper surface for about 30 minutes.

[0120] The slurry-deposited copper sheet was then heated in a tube furnace at a reaction temperature of approximately 805°C in an inert atmosphere. The inert atmosphere was created by purging the furnace with argon. The slurry-deposited copper surface was then subjected to this reaction temperature for approximately 30 minutes. The hydrogen flow rate in the furnace was 500 cc / min. After heating for 30 minutes, the furnace was purged with argon. Following this treatment, an intermediate product comprising a carbon-based composite material (including a graphene film disposed on amorphous carbon) was provided on the copper substrate sheet.

[0121] The copper coil is then positioned between the first and second drive rollers and rolled through a tank containing an aqueous solution of CaCl2 with a concentration of approximately 0.004 M. Four guide rollers are positioned within the tank. These guide rollers are configured as platinum electrodes. The copper substrate sheet rolls across the tank on the platinum electrodes. Four counter electrodes are positioned within the tank. The platinum electrodes and counter electrodes are connected to a voltage regulator operating with a constant current pulse sequence. A first voltage of -4 V is applied between the copper substrate sheet and the platinum electrodes via the voltage regulator. This causes CaCl2 to... 2+Ions are embedded between a graphene film and amorphous carbon from an aqueous solution. A second voltage of +4V, which is the reverse voltage compared to the first voltage, is then applied between a copper substrate sheet and a platinum electrode. As the embedded ions travel toward the platinum electrode, the second voltage pulls graphene and / or graphene oxide out of the carbon-based composite material. The first and second voltages are pulsed alternately, 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 sheet is then transferred into the aqueous solution with minimal copper consumption.

[0122] The aqueous solution is then drained from the tank and passed through a filter press, where graphene and graphene oxide flakes are separated from the aqueous solution.

[0123] The copper surface sheet is then fed through an ultrasonic bath and subsequently into a tank containing an aqueous solution and electrodes. Reduction occurs in the tank to reduce the copper ions that were oxidized and returned to the copper sheet substrate during the application of the first and second voltages.

[0124] Graphene and graphene oxide obtained by scanning electron microscopy. As shown in Figures 3a-3b, graphene with an average size of at least 1 μm was obtained. 2 Graphene sheets that are crystalline, self-supporting hexagonal flakes. For example... Figure 4 As shown, an average size of at least 1 μm was obtained. 2 Crystalline self-supporting lamellae, which have multiple crystal dendrites.

[0125] Example 2

[0126] Carbon-based composite materials were prepared as follows: 0.5 g of bio-oil was electrocoated onto a copper-based sheet in the form of a copper roll using a continuous roll-to-roll system to obtain a bio-oil layer that substantially covers both sides of the copper-based sheet.

[0127] The bio-oil-deposited copper sheet was then heated in a tube furnace at a reaction temperature of approximately 820°C in an inert atmosphere. The inert atmosphere was created by purging the furnace with argon. The bio-oil-coated copper surface was then subjected to this reaction temperature for approximately 30 minutes. The hydrogen flow rate in the furnace was 350 cc / min. After heating for 40 minutes, the furnace was purged with argon. Following this treatment, an intermediate product containing a carbon-based composite material (including a graphene film disposed on graphite) was provided on the copper substrate sheet. The results were confirmed using scanning electron microscopy. Figure 5 This is a scanning electron micrograph showing a carbon-based composite material 501 on a copper substrate sheet 502.

[0128] The copper coil is then positioned between the first and second drive rollers and rolled through a tank containing an aqueous solution of K₂SO₄ with a concentration of approximately 0.001 M. Four guide rollers are positioned within the tank. These guide rollers are configured as platinum electrodes. The copper substrate sheet rolls across the platinum electrodes through the tank. Four counter electrodes are positioned within the tank. The platinum electrodes and counter electrodes are connected to a voltage regulator operating with a constant current pulse sequence. A first voltage of -10 V is applied between the copper substrate sheet and the platinum electrodes via the voltage regulator. This causes K₂SO₄ to... + Ions are embedded from an aqueous solution between the graphene film and graphite, and / or into the graphite. A second voltage of +2V is then applied between a copper substrate sheet and a platinum electrode, which is the reverse voltage compared to the first voltage. As the embedded ions travel toward the platinum electrode, the second voltage pulls graphene and / or graphene oxide out of the carbon-based composite material. The first and second voltages are pulsed alternately, 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 sheet is then transferred into the aqueous solution with minimal copper consumption.

[0129] The aqueous solution is then drained from the tank and passed through a filter press, where graphene and graphene oxide flakes are separated from the aqueous solution.

[0130] The copper surface sheet is then fed through an ultrasonic bath and subsequently into a tank containing an aqueous solution and electrodes. Reduction occurs in the tank to reduce the copper ions that were oxidized and returned to the copper sheet substrate during the application of the first and second voltages.

[0131] Graphene and graphene oxide were studied using a scanning electron microscope. The formation of graphene sheets was confirmed using scanning electron microscopy. See [link to relevant documentation]. Figures 6a-6b . Figures 6a-6b This is a scanning electron micrograph showing a graphene sheet formed on a SiO2 plate.

[0132] As illustrated in Examples 1 and 2, it has been recognized that the inventive concept involving graphene separation can be carried out using any carbonaceous material.

[0133] Furthermore, variations in the disclosed embodiments and examples are things that a person skilled in the art would understand and accomplish by studying the drawings, the disclosure, and the appended claims when practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. The mere fact that certain measures are described in mutually different dependent claims does not imply that combinations of these measures cannot be advantageously used.

Claims

1. A method for producing graphene and / or graphene oxide, the method comprising the following steps: a) Provide a copper-based sheet coated with a carbonaceous material on at least one side; b) providing a tank containing an aqueous solution comprising at least one salt of an ion selected from Li + , Na + , K + , Mg 2+ or Ca 2+ , a first electrode being arranged in the tank; c) The first portion of the copper-based sheet is fed into the tank; d) Applying a first voltage between the copper-based sheet and the first electrode, such that at least one ion is embedded in the carbonaceous material on the first portion of the copper-based sheet; e) Applying a second voltage, opposite to the first voltage, between the copper-based sheet and the first electrode, causing graphene and / or graphene oxide to peel off from the carbonaceous material on the first portion of the copper-based sheet; f) Repeat steps d) and e); g) The copper-based sheet is fed through the groove to remove a first portion of the copper-based sheet from the groove, while a second portion of the copper-based sheet is fed into the groove; h) Applying a first voltage between the copper-based sheet and the first electrode, causing the at least one ion to embed into the carbonaceous material on the second portion of the copper-based sheet; i) Applying a second voltage, which is opposite to the first voltage, between the copper-based sheet and the first electrode, causing graphene and / or graphene oxide to peel off from the carbonaceous material on the second portion of the copper-based sheet; j) Repeat steps h) and i); k) Filter the aqueous solution to collect the graphene and / or graphene oxide and provide a filtered aqueous solution containing copper ions. Wherein, the first voltage is a negative voltage and the second voltage is a positive voltage, the second voltage is applied for a shorter time than the first voltage, and the second voltage is applied for less than 0.15 seconds.

2. The method for producing graphene and / or graphene oxide according to claim 1, wherein, The carbonaceous material includes a graphene film arranged on an amorphous carbon substrate.

3. The method for producing graphene and / or graphene oxide according to claim 1 or 2, wherein, The carbonaceous material includes graphite.

4. The method for producing graphene and / or graphene oxide according to claim 1, wherein, The copper-based sheet is fed into the trough via a feeding device that includes multiple rollers.

5. The method for producing graphene and / or graphene oxide according to claim 4, wherein, The first electrode is arranged as one of the plurality of rollers.

6. The method for producing graphene and / or graphene oxide according to claim 1, further comprising the following steps: -Reducing copper ions from the filtered aqueous solution on the copper-based sheet.

7. The method for producing graphene and / or graphene oxide according to claim 1, wherein, The salt comprises Na + or Ca 2 + .

8. The method according to claim 1, wherein, The graphene and / or graphene oxide exfoliated from the carbonaceous material comprises graphene with an average size of at least 1 µm. 2 Crystalline self-supporting hexagonal graphene sheets, and / or wherein the graphene and / or graphene oxide exfoliated from the carbonaceous material comprises an average size of at least 1 µm. 2 Crystalline self-supporting graphene sheets with multiple dendrites.

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