Method for manufacturing graphene film, graphene film and apparatus for manufacturing the same
By using a composite of catalyst metal foil, graphene film, and proton-conducting film, the graphene film is exfoliated from the catalyst metal surface through electrolysis, addressing the inefficiencies of existing methods and enabling cost-effective, high-speed production of large-area graphene films with both sides usable.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NAGOYA INSTITUTE OF TECHNOLOGY
- Filing Date
- 2025-01-16
- Publication Date
- 2026-07-29
AI Technical Summary
The removal of catalyst metal after graphene film formation is a time-consuming and costly process, and existing methods result in waste of graphene on one surface and inability to reuse the catalyst metal.
A method involving a composite of catalyst metal foil, graphene film, and proton-conducting film, utilizing electrolysis to exfoliate the graphene film from the catalyst metal surface through electrochemical action, allowing for simultaneous peeling on both surfaces and eliminating the need for etching.
Enables reuse of the catalyst metal, reduces manufacturing costs, accelerates the graphene transfer process, and allows for large-area graphene films to be produced without affecting processing time, utilizing both sides of the graphene film.
Smart Images
Figure 2026122509000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a graphene film, a graphene film, and a manufacturing apparatus therefor.
Background Art
[0002] A graphene film with an extremely thin thickness of 1 nanometer or less is light, flexible, and transparent, can be flexibly bent while having diamond-like strength, has an electrical conductivity higher than silver, and a thermal conductivity about 10 times that of copper. Therefore, due to its high chemical resistance and heat resistance, it has attracted attention as a substitute for silicon and precious metals.
[0003] Although details will be described later, as a method for realizing the production of highly crystalline and large-area graphene, the CVD method (see FIG. 1) for chemically synthesizing graphene on the surface of a catalytic metal such as Cu has attracted attention.
[0004] The present inventor has disclosed in Patent Document 1 a proton permeable electrode composed of a two-dimensional substance (preferably graphene), having catalytic nanoparticles supported on the surface of one side of the two-dimensional shape, and having proton permeability and capable of serving as a cathode. Non-Patent Document 1 also describes that a uniform single-layer graphene film can be formed on the surface of a Cu foil heated to 1000°C by a CVD method using a mixed gas of methane and hydrogen.
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Non-Patent Documents
[0006]
Non-Patent Document 1
[0007] However, the need to remove the catalyst metal by chemical etching after graphene film formation has been a time-consuming and costly process. Therefore, the present invention aims to provide a method for manufacturing a graphene film by utilizing the proton permeability of graphene to exfoliate the graphene film from the catalyst metal surface, as well as a graphene film and an apparatus for manufacturing the same. [Means for solving the problem]
[0008] The present invention, which solves the above problems, is as follows. [1] A method for manufacturing a graphene film, comprising: a raw material manufacturing step for manufacturing a composite of raw materials; and an intermediate material manufacturing step for manufacturing a composite of intermediate materials by performing electrolysis on the composite of raw materials, wherein the intermediate material is included in the composite of intermediate materials and can be used to coat the surface of an object to be coated, wherein the composite of raw materials is a catalyst metal foil / graphene film / proton conduction film composite in which graphene films are formed on both surfaces of a catalyst metal foil, and a proton conduction film is further formed on the outer surface of each of the graphene films, the electrolysis is performed with an electrolyte capable of supplying protons and the composite of raw materials as the cathode or anode, and the composite of intermediate materials is a graphene film / proton conduction film composite in which a proton conduction film is formed on one surface of the graphene film that has been peeled off from the composite of raw materials. [2] The peeling is carried out based on an electrochemical action by which the protons can permeate the proton-conducting film and the graphene film and reach the surface of the catalyst metal foil, as described in [1]. [3][1] is a graphene film included in the composite of intermediate materials. This is a method for transferring graphene films, which allows for the isolation and transfer of graphene films from the composite of intermediate materials described in [4][1]. The surface of the coated material is covered with the graphene film described in [5][3]. [6] A graphene film manufacturing apparatus according to [1], comprising a power supply, an electrolytic cell, an electrolyte that can supply protons stored in the electrolytic cell, an anode, and a cathode, wherein one of the anode and the cathode is a composite of the raw materials described in [1]. The anode or cathode contains a composite of the raw materials described in [7] and [6]. [Effects of the Invention]
[0009] According to the graphene film manufacturing method of the present invention, etching of the catalyst metal foil becomes unnecessary, enabling the reuse of the catalyst metal foil and leading to a significant reduction in manufacturing costs. Single-crystal catalyst metal substrates can also be used, making it possible to create single-crystal graphene films. Since etching time is eliminated, the graphene transfer process is accelerated. Because graphene exfoliation proceeds simultaneously across the entire catalyst metal surface, the effect of being able to produce large-area graphene films without affecting processing time can be achieved. [Brief explanation of the drawing]
[0010] [Figure 1] This diagram illustrates the conventional process for manufacturing a graphene film using a metal catalyst foil / graphene film / PMMA film composite, and the process for transferring the graphene film contained in the graphene film / PMMA film composite to the object to be transferred. [Figure 2] This figure schematically shows the manufacturing process of a graphene film and the transfer process of a graphene film when a catalyst metal foil / graphene film / proton-conducting film composite is used as the cathode (in the case of hydrogen generation), which is one embodiment of the present invention. [Figure 3] (a) In the case of hydrogen generation, the figures show the change in current density over time between the Nafion coating, which is a proton-conducting membrane, and the PMMA coating, which is an insulating film, and (b) the Cu contamination of the graphene film peeled off from the graphene film / Nafion film composite by the conventional method and the present invention method, respectively. [Figure 4] This figure shows the Raman spectrum of Nafion, which is a layered graphene film, exfoliated from a catalyst Cu foil / graphene film / Nafion film composite. [Figure 5] This diagram schematically shows the manufacturing process of a graphene film when a catalyst metal foil / graphene film / proton-conducting film composite is used as the anode (in the case of oxidative dissolution of the catalyst Cu surface). [Figure 6] This figure shows the change in current density over time as the Nafion film / graphene film composite is peeled off during the oxidative dissolution of the catalyst Cu surface. [Modes for carrying out the invention]
[0011] Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and modifications, alterations, and improvements may be made without departing from the scope of the invention.
[0012] In conventional technology, the graphene film 2 is transferred to the transfer target M in the process shown in Figures 1(a) to (f). Here, the transfer target M is a typical example of the object to be coated, and the transfer of the graphene film 2 results in one side surface of the transfer target M being coated with the graphene film 2. The catalyst metal foil / graphene film composite 3 is manufactured by a CVD method in which a catalyst metal foil 1 such as Cu or Ni with a thickness of several tens of micrometers (Figure (a)) is treated, for example, in CH4 gas at 1000°C, thereby depositing the graphene film 2 on one side surface 1a and the graphene film 2' on the other side surface 1a' of the catalyst metal foil 1 (Figure (b)).
[0013] By spin coating, a PMMA film 4 is formed on the outer surface 2a of one of the graphene films 2 and 2' on both sides of the catalyst metal foil / graphene film composite 3, thereby producing the first catalyst metal foil / graphene film / PMMA film composite 5 (Figure (c)). The first catalyst metal foil / graphene film / PMMA film composite 5 is then subjected to treatment such as Ar sputtering or UV ozone to remove the graphene film 2' formed on the other surface 1a', thereby producing the second catalyst metal foil / graphene film / PMMA film composite 6 (Figure (d)). Note that the method is not limited to spin coating; methods such as attaching the PMMA film 4 can also be used.
[0014] The second catalyst metal foil / graphene film / PMMA film composite 6 is etched to remove the catalyst metal foil 1 and produce the graphene film / PMMA film composite 7 (Figure (e)). Then, the graphene film 2, which is the object to be transferred, is transferred from the graphene film / PMMA film composite 7, which is the source material, to one side surface of the transfer destination M, and the PMMA film 4 is dissolved and removed (Figure (f)). As a result, a coating M' (not shown) having the graphene film 2 on one side surface is produced.
[0015] The first catalyst metal foil / graphene film / PMMA film composite 5 has graphene films 2 and 2' laminated on both surfaces 1a of one side and the other surface 1a' of the catalyst metal foil 1 respectively, and a PMMA film 4 laminated on the outer surface 2a of the graphene film 2 on one side. The second catalyst metal foil / graphene film / PMMA film composite 6 has a graphene film 2 laminated on one surface 1a of the first catalyst metal foil 1, and a PMMA film 4 laminated on the outer surface 2a of the graphene film 2. And the graphene film / PMMA film composite 7 has the graphene film 2 and the PMMA film 4 laminated together.
[0016] The conventional method for manufacturing a graphene film shown in FIG. 1 has the following main manufacturing process problems 1 to 4. Problem 1 of the manufacturing process: Etching of the catalyst metal foil (catalyst metal foil 1) requires an etching agent and an etching time (about 6 hours). Problem 2 of the manufacturing process: The catalyst metal foil (catalyst metal foil 1) cannot be reused. Problem 3 of the manufacturing process: Post-treatment of the etching solution is required. Problem 4 of the manufacturing process: Only the graphene (graphene film 2) on one surface (one surface 1a of the second catalyst metal foil / graphene film / PMMA film composite 6) of the formed graphene film can be used. That is, the graphene (graphene film 2') on the other surface 1a' of the second catalyst metal foil / graphene film / PMMA film composite 6 is wasted.
[0017] The graphene film manufacturing method according to the present invention can solve the above-mentioned manufacturing process problems by utilizing the processes of conventional graphene film manufacturing methods while incorporating a completely different and groundbreaking process. This groundbreaking process involves using a composite of a proton-donating electrolyte and raw materials that can be manufactured using conventional manufacturing processes as the cathode or anode and performing electrolysis, utilizing the electrochemical action at the cathode or anode. This will be explained below. Although the graphene film manufacturing method according to the present invention directly manufactures an intermediate material containing a graphene film, the graphene film contained in this intermediate material can be used within the scope of the prior art, so the manufacturing method of the present invention can be called a graphene film manufacturing method.
[0018] A typical example of electrochemical action when a composite of raw materials, namely a catalyst metal foil / graphene film / proton-conducting film composite, is used as the cathode is due to hydrogen (H2) generated on the surface of the catalyst metal foil. On the other hand, a typical example of electrochemical action when a catalyst metal foil / graphene film / proton-conducting film composite is used as the anode is due to the oxidative dissolution of the surface of the catalyst metal foil. Both will be explained, but the electrochemical action is not limited to these two, as long as it utilizes the composite of raw materials as either the cathode or anode.
[0019] As shown in Figure 2, the manufacturing process of the graphene film 2 is the same as in Figures 1(a) and 1(b), and the catalyst metal foil / graphene film composite 3 is manufactured by these manufacturing processes. In Figure 1(c), the catalyst metal foil / graphene film / Nafion film composite 15, which is a composite of raw materials, is formed by spin coating to create a Nafion film 10 instead of a PMMA film 4 on both sides of the Cu foil 1 (one side surface 1a and the other side surface 1a'). The Nafion film is an example of a proton-conducting film, and is not limited to any film that has proton conductivity. In addition, methods other than spin coating, such as attaching the Nafion film to the catalyst metal foil / graphene film composite 3, can be used.
[0020] The catalyst Cu foil / graphene film / Nafion film composite 15 has graphene films 2 and 2' laminated on one side surface 1a and the other side surface 1a' of the catalyst metal foil 1, respectively, and Nafion films 10 laminated on the outer surface 2a of the graphene film 2 on one side and the outer surface 2a' of the graphene film 2 on the other side.
[0021] Multiple 1 cm square catalyst metal foil / graphene film / Nafion composites 15 were manufactured according to the manufacturing process shown in Figures 2(a) to (c). The catalyst metal foil had a thickness of approximately 25 μm, the graphene film was a single layer, and the Nafion film had a thickness of approximately 25 μm.
[0022] (When a composite of raw materials is used as the cathode, peeling occurs due to hydrogen (H2)) As shown in Figure 2(d), electrolysis was performed by applying a voltage from a power supply 12 to a 0.5 M dilute sulfuric acid aqueous solution 14 (sulfuric acid is a typical example of an electrolyte that can donate protons, but is not limited to this) stored in the electrolytic cell 11, a Cu substrate 13 as the anode, and a catalyst Cu foil / graphene film / Nafion film composite (composite of raw materials) 15 as the cathode, which is a catalyst metal foil / graphene film / proton-conducting film composite. As a result, since graphene (film) is proton-permeable, as shown in Figure 2(e), a reaction occurred in which protons that permeated the Nafion film 10 and the graphene film 2 reached both surfaces of the Cu foil 1 and were reduced to hydrogen (H2). This reaction proceeded across both surfaces of the Cu foil 1.
[0023] Since the Cu foil 1 and graphene film 2(2') are impermeable to hydrogen (H2), the generated hydrogen (H2) pushes open the interface between the Cu foil 1 and the graphene film 2(2'), creating a gap, and the surface of the graphene film 2(2') and the surface of the Cu foil 1 peel off. In other words, the graphene film 2(2') peeled off from the Cu foil 1, and a graphene film / Nafion film composite (intermediate material composite) 17 could be produced (Example 1). Since such peeling occurs on both surfaces of the Cu foil 1, two graphene film / Nafion film composites (intermediate material composites) 17 can be produced from one catalyst Cu foil / graphene film / Nafion film composite (raw material composite) 15. The graphene film / Nafion film composite 17 consists of a graphene film 2 and a Nafion film 10 stacked on top of each other.
[0024] Then, using the graphene film 2(2') contained in the graphene film / Nafion film composite (composite of intermediate materials) 17, the graphene film 2(2'), which is the object to be transferred, can be transferred from the graphene film / Nafion film composite 15, which is the source of the transfer, to one side surface of the transfer destination M, which is a substrate such as a semiconductor (Figure (f)). Note that the substrate such as a semiconductor is just one example of an object to be coated, and is not limited to these, but various electronic components and the like can be used as objects to be coated.
[0025] On the other hand, electrolysis was performed using a second catalyst metal foil / graphene film / PMMA film composite 6 instead of the catalyst Cu foil / graphene film / Nafion film composite 15 as the cathode (Comparative Example 1). In this case, the graphene film 2 did not peel off from the Cu foil 1, and the graphene film / Nafion film composite 15 could not be manufactured. This is because protons do not permeate the PMMA film and cannot reach the surface of the catalyst Cu foil 1.
[0026] In Figure 2, after Figures (a) and (b), a Nafion film was formed on one side surface as shown in Figure (c) to produce another catalyst Cu foil / graphene film / Nafion film composite 16 (not shown). The other catalyst Cu foil / graphene film / Nafion film composite 16 was etched to remove the catalyst metal foil 1 to produce another graphene film / Nafion film composite 18 (a conventional graphene film / Nafion film, not shown) (Comparative Example 2).
[0027] As shown in Figure 3(a), when -0.3V (reverse hydrogen electrode reference) was applied in 0.5M dilute sulfuric acid 14, a large negative current flowed in the catalyst Cu foil / graphene film / Nafion film composite 15, which was surface-protected with a proton-conducting Nafion film, because protons in the dilute sulfuric acid 14 passed through Nafion and graphene to cause a hydrogen evolution reaction on the Cu surface (Measurement Example 1). As bubbles from hydrogen evolution covered the surface of the Cu foil 1, the current value decreased and the peeling of the graphene film 10 progressed (Example 1). On the other hand, in the second catalyst metal foil / graphene film / PMMA film composite 6, which was surface-protected with a PMMA film that does not conduct protons, no current flowed because hydrogen evolution did not progress on the surface of the Cu foil 1 (Comparative Measurement Example 1), and peeling did not progress (Comparative Example 2).
[0028] Figure 3(b) shows the current-potential response measured in 0.5 M dilute sulfuric acid, using the graphene / Nafion film 15 exfoliated by the present invention and another graphene / Nafion film composite 18 obtained by a conventional method (copper etching) as electrodes. The other graphene / Nafion film composite 18 obtained by the conventional method shows a large current flow, which is due to Cu ions generated by the etching process remaining in the film and causing an oxidation-reduction response (comparative measurement example 2). In contrast, in the present invention, almost no response from Cu ions is observed (measurement example 2). Since the Nafion film 10 itself is not conductive, the flow of current indicates that the graphene / Nafion film 15 has been exfoliated. The current value was measured as follows: A three-electrode potentiostat was used, which can control the potential of the working electrode with a reversible hydrogen electrode as a reference and measure the current value flowing between the working electrode and the counter electrode.
[0029] Furthermore, as shown in Figure 4, the presence of a single layer of graphene on Nafion was confirmed by Raman spectroscopy (spectrum G, 2D) at an excitation wavelength of 785 nm for graphene film / Nafion film composite (composite of intermediate material) 17 (Example 1) (Measurement Example 3).
[0030] (When a composite of raw materials is used as the anode, peeling occurs due to oxidative dissolution of the Cu surface.) Figures 5(a) to (c) are the same as Figures 2(a) to (c). In Figure 5(e), the anode uses a catalyst Cu foil / graphene film / Nafion film composite 15' as a catalyst metal foil / graphene film / proton conductive film composite, and electrolysis is performed by applying a voltage with power supply 12. Then, due to the proton permeability of graphene 2(2') and Nafion film 10, the Cu foil 1 is not insulated as an electrode, so selective electrochemical oxidation dissolution of only the surface of the Cu foil 1 in contact with graphene 2(2') becomes possible. + or Cu 2+ The graphene film 2(2') was peeled off from the Cu foil 1 by oxidation (to which the graphene film 2(2') was produced, thereby manufacturing a graphene film / Nafion film composite 17' (Example 2). The graphene film / Nafion film composite 17' consists of a graphene film 2(2') and a Nafion film 10 laminated together.
[0031] Note that the catalyst Cu foil / graphene film / Nafion film composite 15' is the same as the catalyst Cu foil / graphene film / Nafion film composite 15 as a composite, but the former is used as the anode and the latter as the cathode.
[0032] As shown in Figure 6, the electrochemical oxidative dissolution of the surface of the Cu foil 1 caused the graphene film / Nafion film composite 17 to peel off, and the current density of the Cu foil 1 decreased over time (Measurement Example 4). This change in current value is because, since the pH of the Nafion film is lower than the pH of the electrolyte, the Cu dissolution rate is fast when the graphene film / Nafion film composite 17 is in close contact with the Cu surface, and the dissolution rate slows down as peeling progresses. The current value was measured using a three-electrode potentiostat in the same manner as described above.
[0033] Furthermore, in the case of the graphene film / Nafion film composite (composite of intermediate material) 17' (Example 2), similar to Figure 3(b), we were able to confirm that the graphene had peeled off from the Cu foil by electrochemically measuring the conductivity of the graphene film / Nafion film composite (Measurement Example 5).
[0034] The manufacturing method shown in Figure 1 is compared to the manufacturing methods shown in Figures 2 and 3 as follows. The manufacturing method in Figure 1 has several problems: only one side of the deposited graphene film can be used, the metal catalyst cannot be reused, and it requires an etching agent and etching time (~6 hours) for the metal catalyst. In contrast, the manufacturing method shown in Figure 2 eliminates the need for etching the catalyst metal, making it reusable and leading to a significant reduction in manufacturing costs. Single-crystal catalyst metals can also be used, making it possible to create single-crystal graphene. The graphene transfer process is accelerated because etching time is eliminated. Since graphene peeling proceeds simultaneously across the entire catalyst metal surface, high-speed processing (approximately 5 minutes) can be performed regardless of the processing area of the graphene film to be manufactured. Furthermore, it offers the remarkable effect of being able to use both sides of the deposited graphene film. Note that the catalyst metal material that can be used in the manufacturing method in Figure 2 must not dissolve due to the hydrogen generation potential. Therefore, Ni is not suitable for use.
[0035] Next, in the manufacturing method shown in Figure 3, the reaction proceeds across the entire Cu surface, allowing for high-speed processing (approximately 5 minutes) regardless of the processing area. Since only the outermost surface of the Cu catalyst is slightly dissolved, it is recyclable. Furthermore, similar to the manufacturing method shown in Figure 2, etching of the catalyst metal is unnecessary, single-crystal graphene can be produced, and both sides of the deposited graphene can be utilized. [Industrial applicability]
[0036] The CVD method is being researched as the most promising industrial method for producing graphene, and the cost-reduction effect of this invention has the potential to be a useful technology in all aspects of the industrial use of graphene. [Explanation of symbols]
[0037] 1: Catalyst metal foil (Cu foil) 1a: One side surface of the catalyst metal foil 1a': Other surface of the catalyst metal foil 2, 2': Graphene film 2a: Outer surface of the graphene film 3: Catalyst metal foil / graphene film composite 4:PMMA membrane 5: First catalyst metal foil / graphene film / PMMA film composite 6: Second catalyst metal foil / graphene film / PMMA film composite 7: Graphene membrane / PMMA membrane composite 10:Nafion membrane 11: Electrolytic cell 12: Power supply 13:Cu substrate 14: Dilute sulfuric acid aqueous solution 15, 15': Catalyst Cu foil / graphene film / Nafion film composite (composite of raw materials) 16: Another catalyst Cu foil / graphene film / Nafion film composite 17, 17': Graphene film / Nafion film composite (composite of intermediate materials) 18: Another graphene membrane / Nafion membrane composite M: Transfer futures М´:Coating
Claims
1. A method for manufacturing a graphene film comprising: a raw material manufacturing step for manufacturing a composite of raw materials; and an intermediate material manufacturing step for manufacturing a composite of intermediate materials by performing electrolysis on the composite of raw materials, wherein the intermediate material is included in the composite of intermediate materials and can be used to coat the surface of an object to be coated, wherein the composite of raw materials is a catalyst metal foil / graphene film / proton conduction film composite in which graphene films are formed on both sides of a catalyst metal foil, and a proton conduction film is further formed on the outer surface of each of the graphene films, the electrolysis is performed using an electrolyte capable of supplying protons and the composite of raw materials as the cathode or anode, and the composite of intermediate materials is a graphene film / proton conduction film composite in which a proton conduction film is formed on one side surface of the graphene film that has been peeled off from the composite of raw materials.
2. The method for producing a graphene film according to claim 1, wherein the peeling is performed based on an electrochemical action resulting from the protons being able to permeate the proton-conducting film and the graphene film and reach the surface of the catalyst metal foil.
3. A graphene film comprising the composite of intermediate materials according to claim 1.
4. A method for transferring a graphene film, which allows for the isolation and transfer of a graphene film from a composite of intermediate materials as described in claim 1.
5. A coating whose surface is covered with the graphene film described in claim 3.
6. A graphene film manufacturing apparatus according to claim 1, comprising a power supply, an electrolytic cell, an electrolyte that can supply protons stored in the electrolytic cell, an anode, and a cathode, wherein one of the anode and the cathode is a composite of the raw materials described in claim 1.
7. An anode or cathode comprising a composite of the raw materials described in claim 6.