Method for metal film assisted transfer of graphene thin films and applications

Abstract

The application discloses a method for transferring a graphene film with the aid of a metal film and application thereof. The method of the application can eliminate the influence of residual glue, and can realize batch preparation without any organic polymer glue layer with the aid of the metal film. The method is simple in process, short in time consumption, and high in graphene integrity in the prepared composite film, and can reach 90%-99%. The graphene composite film prepared by the method can be directly applied to hydrogen isotope separation without removing the metal film.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional carbon materials, specifically relating to a method for metal-assisted transfer of graphene films and its applications. Background Technology

[0002] Graphene, a two-dimensional thin film material with a single atomic layer thickness, possesses excellent optical, electrical, mechanical, and thermal properties. Furthermore, due to its unique two-dimensional honeycomb lattice structure, it has been widely applied in recent years in fields such as support membranes, filter membranes, and separators. A perfect graphene film cannot allow any atoms or molecules to pass through, but protons can pass through a single layer of graphene without difficulty. According to theoretical analysis, hydrogen ions (H+)... + ) and deuterium ions (D + The 60 meV difference in the zero-point energy of the intermediate state through graphene leads to the H at room temperature + The rate at which graphene passes through is D. + This is 10 times faster, potentially enabling low-energy, high-efficiency hydrogen isotope separation. Simultaneously, single-crystal graphene can maintain its perfect structure and excellent properties to the greatest extent. To achieve this goal, in addition to preparing high-quality, intact single-crystal graphene, constructing a high-quality graphene separation membrane is crucial. The preparation of the graphene separation membrane requires transferring the graphene film from a copper substrate to the target substrate. However, this transfer process often causes damage and contamination of the graphene film, leading to poor isotope separation or even failure. Furthermore, considering the poor self-support of atomically thin graphene separation membranes, the target substrate also needs to provide mechanical support and proton transport; therefore, the selection and optimization of the target substrate are also critical.

[0003] Therefore, developing a method and stable production process for preparing high-integrity, large-area single-crystal graphene composite separation membranes will lay the material foundation for graphene films in key areas such as hydrogen isotope separation, and has important scientific significance and application value. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for transferring graphene films using a metal film-assisted process.

[0005] The first aspect of this invention provides a method for metal-film-assisted transfer of graphene films, comprising: S1, providing a metal substrate / graphene film composite, wherein the graphene film is grown on the metal substrate; S2, depositing a metal film on the surface of the graphene film of the metal substrate / graphene composite; S3, attaching a thermo-pressure-sensitive organic film to the surface of the metal film to obtain a metal substrate / graphene / metal film / thermo-pressure-sensitive organic film composite; S4, further processing the metal substrate / graphene / metal film / thermo-pressure-sensitive organic film... The composite is suspended on the surface of the etching solution, and the metal substrate in the metal substrate / graphene / metal film / thermosensitive organic film composite is etched away to obtain the graphene / metal film / thermosensitive organic film composite; S5, the target substrate is combined with the graphene / metal film / thermosensitive organic film composite to obtain the target substrate / graphene / metal film / thermosensitive organic film composite; and S6, the thermosensitive organic film in the target substrate / graphene / metal film / thermosensitive organic film composite is released.

[0006] According to one embodiment of the present invention, the metal film is selected from one or more of cobalt, nickel, ruthenium, rhodium, palladium and rhenium; preferably, the thickness of the metal film is 2-100 nm.

[0007] According to another embodiment of the present invention, the metal film is deposited by thermal evaporation or electron beam evaporation in step S2.

[0008] A second aspect of the present invention provides a method for preparing a metal-graphene-organic composite film, comprising: S1, providing a metal substrate / graphene film composite, wherein the graphene film is grown on the metal substrate; S2, depositing a metal film on the surface of the graphene film of the metal substrate / graphene composite; S3, attaching a thermo-pressure-sensitive organic film to the surface of the metal film to obtain a metal substrate / graphene / metal film / thermo-pressure-sensitive organic film composite; and S4, suspending the metal substrate / graphene / metal film / thermo-pressure-sensitive organic film composite on the surface of an etching solution. S5, the metal substrate in the metal substrate / graphene / metal film / thermosensitive (pressure-sensitive) organic film composite is etched away to obtain the graphene / metal film / thermosensitive (pressure-sensitive) organic film composite; S6, the organic film serving as the target substrate is composited with the graphene / metal film / thermosensitive (pressure-sensitive) organic film composite to obtain the organic film / graphene / metal film / thermosensitive (pressure-sensitive) organic film composite; and S7, the thermosensitive (pressure-sensitive) organic film in the organic film / graphene / metal film / thermosensitive (pressure-sensitive) organic film composite is released to obtain the metal-graphene-organic composite film.

[0009] According to one embodiment of the present invention, the graphene film is a single-layer monocrystalline graphene film.

[0010] According to another embodiment of the present invention, the metal film is selected from at least one of platinum and palladium; preferably, the thickness of the metal film is 2-100 nm.

[0011] According to another embodiment of the present invention, the metal film is deposited by thermal evaporation or electron beam evaporation in step S2.

[0012] According to another embodiment of the present invention, the organic membrane is polytetrafluoroethylene (PTFE), polyimide (PI), polycarbonate (PC), polyethylene (PE), polypropylene (PP), or perfluorosulfonic acid proton exchange membrane (Nafion).

[0013] A third aspect of the present invention provides a metal-graphene-organic composite membrane prepared by the above method.

[0014] A fourth aspect of the present invention provides a separation membrane comprising the above-described metal-graphene-organic composite membrane.

[0015] The method of this invention utilizes a metal film without the need for any organic polymer adhesive layer, eliminating the influence of residual adhesive. The resulting graphene film exhibits high integrity and a wide clean area after transfer, and can be mass-produced. This method is simple, time-efficient, and produces composite films with high graphene integrity, reaching 90%-99%. Furthermore, the prepared graphene composite films do not require removal of the metal film and can be directly applied to hydrogen isotope separation. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the metal film-assisted transfer of graphene film according to the present invention.

[0017] Figure 2 This is a schematic diagram of the preparation process in Example 1.

[0018] Figure 3 This is a large-area graphene film prepared on copper foil in Example 1, and its scanning electron microscope (SEM) characterization image.

[0019] Figure 4 The organic target substrate / graphene / metal composite film in Example 1, along with its SEM characterization images and statistical results, are shown.

[0020] Figure 5 Scanning transmission electron microscopy (TEM) imaging of the graphene / metal film in Example 1.

[0021] Figure 6 The statistical results show the hydrogen isotope separation performance of the Pd / graphene / N-212 composite membrane prepared in Example 1. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments.

[0023] like Figure 1 As shown, the method for metal-film-assisted transfer of graphene films according to the present invention includes: S1, providing a metal substrate / graphene film composite, wherein the graphene film is grown on the metal substrate; S2, depositing a metal film on the surface of the graphene film of the metal substrate / graphene composite; S3, attaching a thermo-pressure-sensitive organic film to the surface of the metal film to obtain a metal substrate / graphene / metal film / thermo-pressure-sensitive organic film composite; S4, suspending the metal substrate / graphene / metal film / thermo-pressure-sensitive organic film composite. Floating on the surface of the etching solution, the metal substrate in the metal substrate / graphene / metal film / thermosensitive organic film composite is etched away to obtain the graphene / metal film / thermosensitive organic film composite; S5, the target substrate is combined with the graphene / metal film / thermosensitive organic film composite to obtain the target substrate / graphene / metal film / thermosensitive organic film composite; and S6, the thermosensitive organic film in the target substrate / graphene / metal film / thermosensitive organic film composite is released.

[0024] Steps S1, S2, S3, S4, S5, and S6 in this patent are merely for distinguishing different steps and are not intended to limit the steps to a tight connection. On the contrary, other auxiliary steps may be included between each step, such as etching to remove the graphene film on the back side grown on the metal substrate by CVD before step S1, and cleaning, drying, and other steps may be included between each step.

[0025] This invention relates to a method for metal-film-assisted transfer of graphene films. By replacing existing organic polymer adhesive layers with metal-film assistance, the influence of residual adhesive can be eliminated, resulting in graphene films with high integrity and a wide clean area after transfer, and enabling mass production. The method of this invention is explained in detail below.

[0026] The method of this invention can transfer graphene films grown on a substrate in any manner onto a target substrate. The substrate can be a single-crystal and / or polycrystalline substrate of a transition metal or a transition metal alloy. The transition metal can be selected from at least one of copper, nickel, molybdenum, and gold. The transition metal alloy can be a copper-nickel alloy, etc. The graphene film can be a single-layer, single-crystal graphene film. The target substrate can be an organic film, etc.

[0027] Taking CVD growth on a copper foil substrate as an example, the graphene film on one surface of the copper foil can be removed by etching to form a metal substrate / graphene composite. The etching method can be air plasma etching. Preferably, the excitation power is 20-200 watts, the etching time is 1-5 minutes, and the gas flow rate is 5-20 sccm.

[0028] A metal film is deposited on the surface of a graphene film on a metal substrate / graphene composite. The metal film can be formed using thermal evaporation or electron beam evaporation, with a deposition rate of [missing information]. The thickness of the metal film can range from 2 to 100 nm. If the metal film thickness is less than 2 nm, it is difficult to form a continuous film layer, and it cannot provide support for the graphene film. If the metal film is too thick, it will increase the cost. The metal film can be one or more of cobalt, nickel, ruthenium, rhodium, palladium, and rhenium.

[0029] Subsequently, a heat-sensitive (pressure-sensitive) organic film is attached to the surface of the metal film to obtain a metal substrate / graphene / metal film / heat-sensitive organic film composite. Heat-sensitive (pressure-sensitive) organic films include, but are not limited to, heat-release tape, polydimethylsiloxane (PDMS), and polyaluminum iron silicate (PSAF).

[0030] Subsequently, the metal substrate / graphene / metal film / thermosensitive organic film composite is suspended on the surface of the etching solution. The metal substrate in the composite is then etched away, yielding the graphene / metal film / thermosensitive organic film composite. The etching solution can be ammonium persulfate solution, ferric chloride solution, or aqua regia. The concentration of the etching solution can be 0.1-1 mol / L. The volume ratio of nitric acid to hydrochloric acid in the aqua regia is specifically 1:3. The etching temperature can be 20-30℃.

[0031] Subsequently, the target substrate is laminated with a graphene / metal film / thermosensitive (pressure-sensitive) organic film composite to obtain the target substrate / graphene / metal film / thermosensitive (pressure-sensitive) organic film composite. Before lamination, the graphene / metal film / thermosensitive (pressure-sensitive) organic film composite can be cleaned on a deionized water surface. The lamination can be performed in two ways. The first method involves suspending the graphene / metal film / thermosensitive (pressure-sensitive) organic film composite in deionized water, then using the target substrate to retrieve the suspended composite, with the substrate in contact with the graphene film, thus transferring the graphene film from the growth substrate to the target substrate. The second method involves coating the surface of the target substrate with a dispersion of organic matter, then attaching the graphene / metal film / thermosensitive (pressure-sensitive) organic film composite to the target substrate coated with the dispersion, followed by drying to complete the transfer process. Preferably, the organic matter is made of the same material as the target substrate. The solvent for the dispersion can be any suitable solvent.

[0032] Finally, the heat (pressure) sensitive organic film is released to obtain the target substrate / graphene / metal film composite film.

[0033] The transfer method of this invention can be used to prepare metal-graphene-organic composite membranes. By selecting an organic membrane as the target substrate in the above method, a metal-graphene-organic composite membrane can be prepared. The composite membrane prepared by this method has a high graphene film integrity, reaching 90%-99%. Furthermore, the prepared graphene composite membrane does not require removal of the metal membrane and can be directly applied to hydrogen isotope separation. When used as a hydrogen isotope separation membrane, platinum and palladium are preferred metal membranes.

[0034] In an optional embodiment, the graphene film in the metal-graphene-organic composite film is preferably a single-layer monocrystalline graphene film, and more preferably a large domain region (domain region size on the order of hundreds of micrometers) monocrystalline graphene film.

[0035] In optional embodiments, the organic membrane can be polytetrafluoroethylene (PTFE), polyimide (PI), polycarbonate (PC), polyethylene (PE), polypropylene (PP), or a perfluorosulfonic acid proton exchange membrane (Nafion). To increase the adhesion between the organic membrane and the graphene film, the organic membrane can be treated before lamination. This treatment can be plasma treatment.

[0036] The present invention will be further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.

[0037] Unless otherwise specified, all reagents, materials and instruments used in the following examples and comparative examples are commercially available.

[0038] Example 1: Preparation of Nafion / graphene / Pd composite membrane by metal-assisted transfer

[0039] The following combination Figure 2 The preparation process of this embodiment is described in detail.

[0040] I) Since graphene films prepared by the CVD method grow graphene on both sides of the copper foil, the unused side of the copper foil needs to be removed by air plasma etching. The copper foil, with the graphene on the back side facing upwards, is placed in a plasma apparatus (Diener, pico model, Germany) at a flow rate of 10 sccm, a power of 60W, and a treatment time of 1 minute. After treatment, the graphene on the back side of the copper foil is removed, while the graphene on the front side remains intact, yielding a graphene / Cu composite (approximately 1 × 1 cm).

[0041] II) Plasma-treated graphene / Cu was placed on the sample stage of a thermal evaporation apparatus (Beijing Taicono Technology, ZHD300), with the graphene film facing the metal source. Pd particles were placed in the tungsten boat for metal source evaporation, and the evaporation chamber was evacuated to a vacuum level of 1×10⁻⁶. -4 Pa, evaporation rate is The Pd film thickness was 10 nm. This step yielded a Pd / graphene / Cu composite.

[0042] III) Gently cover the Pd film of the composite in step II) with a PDMS film (Gel-Pak, California, USA, model WF-40×40-0060-X4) to ensure complete adhesion between the PDMS film and the composite film, thus obtaining the PDMS / Pd / graphene / Cu composite.

[0043] IV) PDMS / Pd / graphene / Cu was floated on the surface of a 0.2 mol / L ammonium persulfate solution until the copper foil was completely etched. The etching temperature was room temperature, and the etching time was 1.5-2.5 h.

[0044] V) Gently remove the etched PDMS / Pd / graphene from the surface of the ammonium persulfate solution and place it on a surface of deionized water for cleaning to remove any residual ammonium persulfate solution from the graphene surface. Clean three times in total, one minute each time.

[0045] VI) The PDMS / Pd / graphene composite was transferred onto a Nafion commercial film as follows:

[0046] 1) Method 1: Plasma treatment is applied to the surface of the Nafion commercial membrane to enhance its adhesion to graphene. Specifically, the Nafion commercial membrane (N-212 / PET) is placed with the N-212 side facing up in a plasma device at a flow rate of 10 sccm, a power of 60W, and a treatment time of 3 minutes. The PDMS / Pd / graphene is then rapidly lifted from deionized water using the N-212 / PET and dried at room temperature to obtain the PDMS / Pd / graphene / N-212 / PET composite.

[0047] 2) Method Two: A layer of Nafion dispersion (Jiangsu Kerun New Materials, 5wt%) was spin-coated onto the N-212 surface of a Nafion commercial film (Jiangsu Kerun New Materials, N-212 / polyethylene terephthalate (PET), with PET as a protective layer). The spin-coating speed was 1000 rpm, and the spin-coating time was 60 s. The PDMS / Pd / graphene composite was then bonded to the spin-coated Nafion commercial film and dried at room temperature to obtain the PDMS / Pd / graphene / N-212 / PET composite.

[0048] VII) Place the PDMS / Pd / graphene / N-212 / PET on a hot plate at 150°C with the PDMS side facing up. After about 1 minute, the PDMS film detaches from the Pd surface, and the PDMS film is gently peeled off to obtain the Pd / graphene / N-212 / PET composite film. In use, gently peel off the PET protective layer to perform hydrogen isotope separation tests.

[0049] VIII) The hydrogen isotope separation test of the Pd / graphene / N-212 composite membrane was completed by using an electrochemical workstation (Biological, Israel) capable of outputting constant current and a helium mass spectrometer leak detector (ZQJ-3000G, CAS Instruments).

[0050] Figure 2-4 The characteristics are of the samples and final products during the preparation of Pd / graphene / N-212 / PET composite film using Method 1.

[0051] Figure 3 Photo a is a photograph of a large-area graphene film prepared on copper foil using chemical vapor deposition in Example 1; photos b and c are optical micrographs and SEM images of a single-layer graphene film on the copper foil surface, respectively. Figure 3 As can be seen, the graphene on the copper foil surface is intact and undamaged, and has good monolayer properties.

[0052] Figure 4 Photo a is an image of the Pd / graphene / Nafion composite film prepared in Example 1; photo b is the SEM characterization result of graphene in the composite film. The light gray areas in the image indicate that the graphene is intact, while the dark gray linear areas represent the wrinkles and damaged areas of the graphene, with a graphene integrity of up to 99%. Figure 4 Photo c shows the integrity statistics of 10 graphene samples after Pd-assisted transfer. The damage rate of the transferred graphene was less than 10%, and the average integrity rate was over 97%.

[0053] Figure 5 Transmission electron microscopy imaging of graphene after Pd-assisted transfer. Figure 5 Image a shows a high-magnification TEM image of graphene on a Pd film. The graphene film is uniformly distributed and intact. Due to the presence of the Pd film beneath the graphene, the graphene lattice diffraction pattern is easily affected by the Pd signal, but a clear hexagonal graphene diffraction pattern can still be observed, such as... Figure 5 As shown in photo b.

[0054] Figure 6 The hydrogen isotope separation performance of the Pd / graphene / N-212 composite membrane was studied. The composite membrane prepared by method one had a hydrogen isotope (hydrogen / deuterium) separation coefficient of 7.77; the composite membrane prepared by method two had a hydrogen isotope (hydrogen / deuterium) separation coefficient of 6.53. This verifies the feasibility and effectiveness of the metal-assisted method, and the separation coefficient of the composite membrane is close to the world's leading level.

[0055] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A hydrogen isotope separation membrane, characterized in that, Including metal-graphene-organic composite films; The method for preparing the separation membrane includes: S1, providing a metal substrate / graphene film composite, wherein the graphene film is grown on the metal substrate; S2, depositing a metal film on the surface of the graphene film of the metal substrate / graphene composite; S3, attach a thermosensitive or pressure-sensitive organic film to the surface of the metal film to obtain a metal substrate / graphene / metal film / thermosensitive or pressure-sensitive organic film composite. S4, the metal substrate / graphene / metal film / thermosensitive or pressure-sensitive organic film composite is suspended on the surface of the etching solution, and the metal substrate in the metal substrate / graphene / metal film / thermosensitive or pressure-sensitive organic film composite is etched away to obtain the graphene / metal film / thermosensitive or pressure-sensitive organic film composite. S5, the organic film serving as the target substrate is combined with the graphene / metal film / thermosensitive or pressure-sensitive organic film composite to obtain the organic film / graphene / metal film / thermosensitive or pressure-sensitive organic film composite. S6, release the thermosensitive or pressure-sensitive organic membrane from the organic membrane / graphene / metal membrane / thermosensitive or pressure-sensitive organic membrane composite to obtain the metal-graphene-organic composite membrane; The organic membrane is a polytetrafluoroethylene, polyimide, polycarbonate, polyethylene, polypropylene, or perfluorosulfonic acid proton exchange membrane, and the metal membrane is selected from at least one of platinum and palladium.

2. The separation membrane according to claim 1, characterized in that, The graphene film is a single-layer monocrystalline graphene film.

3. The separation membrane according to claim 1, characterized in that, The thickness of the metal film is 2-100 nm.

4. The separation membrane according to claim 1, characterized in that, In step S2, the metal film is deposited by thermal evaporation or electron beam evaporation.

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