Method for producing a porous graphene film and film produced using the method

Abstract

1. A method for producing a porous graphene layer (5) having a thickness of less than 100 nm, the method comprising the steps of: providing a catalytically active substrate (1) having a plurality of catalytically inactive domains (2) provided on its surface (3) having a size that essentially corresponds to the size of the pores (6) of the resulting porous graphene layer (5); and forming the porous graphene layer (5) on the surface (3) of the catalytically active substrate (1) by chemical vapor deposition, wherein the catalytically active substrate (1) is a copper-nickel alloy substrate having a copper content in the range of 98% to less than 99.96% by weight and a nickel content in the range of greater than 0.04% to 2% by weight, the copper and nickel contents being complementary to each other to add up to 100% by weight of the catalytically active substrate (1).

Description

Technical Field

[0001] The present invention relates to a method for producing a waterproof but highly breathable porous (“honey”) graphene film by promoting vapor permeation through pores opened in a graphene layer. Further, the present invention relates to a graphene film produced using the above method and the use of such a film, and a catalyst substrate for producing such a film and its use.

Background Art

[0002] Waterproof membranes used in outdoor clothing are effective against high hydrostatic pressures (rainwater penetration resistance). However, these waterproof membranes generally have the problem of low moisture permeability, which results in insufficient water vapor transport, breathability of clothing, and user comfort.

[0003] Highly breathable membranes are also suitable for various technical textile applications, including military uniforms for chemical protection, uniforms for emergency personnel, protective gloves, and protective packages for outdoor electronic circuits. Also, membranes that provide high emission rates and / or selectivity have extensive potential uses in separation and energy applications. These membranes will also serve as a catalyst for many other potential application fields that have not been seen due to the current absence of highly breathable membranes.

[0004] In the waterproof membrane market, GoreTex (trademark) is the mainstream, but there are many other suppliers that produce membranes from various polymers other than PTFE, such as polyamide and polyurethane. In any case, the membrane consists of a polymer film having small pores that allow the passage of water vapor. Due to the limitations of the thickness and pore area density of conventional membranes, the magnitude of vapor transport is limited.

[0005] One of the alternative materials proposed for applications that require high moisture permeability and water tightness is porous graphene. sp 2Graphene, a two-dimensional monolayer sheet of hybrid carbon atoms, has attracted worldwide attention and research interest due to its excellent physical properties including high electron conductivity, thermal stability, and mechanical strength. The use of porous graphene membranes in fabric laminate structures has been proposed in the following literature.

[0006] Patent Document 1 generally describes the fixation of a porous graphene layer to a fibrous substrate backing. A laminate assembly is described along with the method of constructing and assembling the laminate. The method used to form the porous graphene layer is not described.

[0007] Patent Document 2 developed the method described in Patent Document 1 by including a selective membrane layer on the graphene layer side and assembling a porous graphene membrane on a fabric substrate. The fabrication of the porous graphene membrane material is outlined to include the growth of continuous monolayers and the perforation of the layers, as well as subsequent processes.

[0008] Aspects related to the present invention in connection with porous graphene and its various fabrication methods can be summarized as follows in categories and subcategories.

[0009] Category 1: Post-synthesis formation of porous graphene - continuous process Post-synthesis formation involves opening holes in a continuous graphene layer synthesized in a previous step. The continuous process involves the fabrication of each hole in the porous graphene layer. This is a time-consuming process and is hardly useful for the scale-up production of porous membranes.

[0010] Category 1.1: Nitrogen-assisted electron beam perforation Using scanning electron microscope (SEM) imaging in the presence of nitrogen gas, a local reactive ion etching process can be induced by ionizing nitrogen molecules with the focused electron beam of the SEM. With this approach, holes up to 10 nm can be etched into multilayer graphene (less than 10 layers). However, due to the diffusion of nitrogen ions from the electron beam focusing region, holes are etched outside the target area, and there are problems in obtaining a dense array of small holes with this approach. Furthermore, the use of SEM results in a continuous hole milling process, making it difficult to scale up.

[0011] Category 1.2: FIB & Unfocused Electron Beam Patterning In this two-step process, first, 3 keV Ar + focused ion beam (FIB) is used to create one-atom and two-atom defects in a single layer of graphene. To obtain the desired defect size, it is necessary to cool the single layer down to 148 K. Next, using an 80 keV unfocused electron beam, it is possible to grow the defects from the edge of the holes without affecting the non-defective graphene part, generating holes with a diameter up to 0.6 nm.

[0012] Alternatively, a focused ion beam using either Ga + ions or He + ions can be used to generate holes with sizes ranging from 1000 nm to less than 10 nm. In this process, control of the pore diameter, pore density, and pore arrangement is possible, but due to the continuity of milling, scaling up is still difficult. Also, milling holes less than 5 nm is difficult.

[0013] Patent Document 3 discloses a graphene film and a method for manufacturing the same. The graphene film includes a graphene layer having a porous pattern including a plurality of holes with a size of 5 nm to 100 nm, and a support configured to support the graphene layer and including a plurality of holes with a size larger than the target holes of the graphene layer. The proposed method includes forming block copolymer domains on the graphene surface and forming a mask template. Subsequently, ion beam irradiation exposure is used to etch holes in the graphene layer.

[0014] Category 1.3: TEM-based method To measure the movement of DNA through graphene nanopores, free-standing graphene can be perforated by an electron beam with an acceleration voltage of 300 kV in a transmission electron microscope (TEM). Holes in the range of 2 nm to 40 nm can be patterned in single-layer graphene and multi-layer graphene. Amorphization is not observed around the holes, indicating that local crystallinity is maintained. However, this method is not parallel and takes a considerable amount of time.

[0015] Category 2: Post-synthesis formation of porous graphene - parallel process Post-synthesis formation includes opening holes in a continuous graphene layer synthesized in a previous step. Parallel processing includes perforating a plurality of positions in the graphene layer simultaneously.

[0016] Category 2.1: Ultraviolet-induced oxidative etching Perform UV etching to create sub-nanometer defects in graphene and grow them by long-term exposure. When etching a bilayer graphene film 15 times by exposure for 1 minute is repeated, for example, holes showing size-selective sieving with a dynamic diameter of 4.9 Å 6 are obtained.

[0017] Category 2.2: Ion bombardment & oxidative etching 8 keV Ga +Ions can be accelerated at an incident angle of 52° on the graphene surface to create defects in the graphene lattice. Subsequently, the graphene defects can be etched using potassium permanganate in acid to etch unsaturated carbon bonds, and the pores can be enlarged until stability at a pore diameter of 0.4 nm occurs after an etching time of 60 minutes. This is thought to be due to the formation of functional groups that inhibit further growth reactions.

[0018] Category 2.3: Oxygen plasma Sub-nanometer pores can be generated by exposing floating monolayer graphene to oxygen plasma etching (20 W) for 1 second to 6 seconds, and the pore diameter and pore density are determined by the etching time. By exposing to plasma for 1.5 seconds, a pore diameter of 0.5 nm to 1 nm can be achieved at a pore density of 1 pore / 100 nm 2 of.

[0019] Category 2.4: Pt nanoparticle perforation by strain By self-assembly of block copolymer (BCP) micelles containing Pt precursors, Pt nanoparticles are dispersed on a substrate, and a pre-fabricated graphene monolayer is transferred onto it. After annealing at 400 °C, perforations can be obtained. Local strain in the Pt nanoparticles promotes catalytic perforation of graphene. The pore diameter and pore density can be controlled by the micelle composition, and pores up to 17 nm can be obtained with a porosity of 12.8%. Theoretically, large-scale perforation should be possible, but it is difficult to obtain a uniform dispersion of the Pt precursor, and the largest area shown is about 4 μm 2 is.

[0020] Category 2.5: Perforation using catalytic oxidation by contact with metal particles Patent Documents 4 and 5 propose depositing a thin metal film layer (Au or Ag) on the surface of an existing graphene layer, followed by an annealing process to form metal particle domains on the graphene surface. By a further thermal process, pores are formed by catalytic oxidation at the contact points with the metal domains.

[0021] Category 2.6: Use of Anodic Alumina as a Template Graphene on a substrate can be patterned using an anodic alumina membrane. The anodic alumina is placed with the side of the small holes facing the existing continuous graphene substrate, and through plasma exposure, the graphene not protected by the alumina is removed. The resulting pore diameter is between 40 nm and 60 nm.

[0022] Category 3: Formation of Porous Graphene Membrane from Graphene Flakes The porous membrane of the graphite layer can alternatively be formed by the assembly of films composed of graphene (or graphene oxide) flakes. In principle, the flakes form a layer structure, and pores are formed between the boundaries of the flakes. In the graphene flake approach, relatively thick layers tend to be formed, and the inherent two-dimensional planar (low thickness) geometry of graphene is not fully utilized.

[0023] Category 3.1: Pore Template during Film Formation Patent Document 6 describes a method for fabricating a graphene film having a three-dimensional porous structure. The polystyrene domains are used as a sacrificial template for pore formation in a film layer formed from graphene oxide flakes as starting materials.

[0024] Category 4: Direct Synthesis of Porous Graphene Membrane The direct synthesis of a porous graphene membrane involves the simultaneous formation of graphene layer(s) that directly form porous features in the graphene layer. In the direct synthesis method, there is no need for post-synthesis treatment to achieve the porous structure.

[0025] Category 4.1: Pores due to Grain Boundary Defects Patent Document 7 proposes the growth of a graphene layer on a non-treated copper substrate. After successively solution-coating a single molecular layer with PMMA, it is immersed in an etching solution to remove copper. The PMMA layer having the graphene layer is attached to a PTMSP film, and the PMMA layer is removed using a solvent. In the obtained graphene layer, there are a plurality of graphene grains, and pores exist as defects between the graphene grains. Patent Document 7 describes the film properties for separating various substances from liquids and gases.

[0026] Category 4.2: Graphene layer formation following template patterning of a carbon source Patent Document 8 provides a method for fabricating a graphene nanopore array, including: 1) a step of coating a carbon source solution on the surface of a porous anodic alumina (PAA) template; 2) a step of pressing the PAA template coated with the carbon source on the surface of a metal base, peeling off the PAA template, and ensuring that the carbon source is maintained on the surface of the metal base and maintains a pattern that matches that on the surface of the PAA template; and 3) a step of performing an annealing treatment on the obtained metal base in the presence of a mixed gas flow of hydrogen gas and argon gas to convert the carbon source into a graphene nanopore array. The nanopore array obtained by this invention has an interconnected nanopore array structure rather than a single nanopore or several nanopores. The pore diameter of the nanopores can be adjusted by the template effect of PAA itself and can be further adjusted by growth and etching in subsequent steps.

[0027] Patent Document 9 describes a method for forming a large-area graphene layer on a porous substrate by a chemical vapor deposition process. In the first step, a carbon material is deposited on a porous template using CVD. In the second step, the carbon material is subjected to annealing and catalytic graphitization to convert the carbon into a graphene layer. In the third step, liquid exfoliation is used to reduce the number of graphene layers on the substrate.

[0028] Category 4.3: Direct growth of porous graphene using a porous template and a pattern Patent Document 10 describes a method for producing a graphene material having a porous structure. A porous magnesium oxide / silicon composite material is used as a template substrate. Graphene is directly grown on the porous template by chemical vapor deposition (CVD). The graphene layer retains the porous structure of the template substrate. The porous graphene layer is recovered by the destructive etching of the magnesium oxide / silicon composite substrate.

[0029] Patent Document 11 discloses a method for fabricating a graphene pattern by forming a pattern of a passivation material on a growth substrate. The pattern of the passivation material defines an inverse pattern of the exposed surface on the growth substrate. A carbon-containing gas is supplied to the inverse pattern of the exposed surface of the growth substrate to form the patterned graphene from carbon. The passivation material does not promote graphene growth, but the inverse pattern of the exposed surface of the growth substrate promotes graphene growth.

[0030] Patent Document 12 proposes a method for growing microstructured and nanostructured graphene by directly growing microstructured and nanostructured graphene in a desired pattern in a bottom-up manner. The graphene structure can be grown by chemical vapor deposition (CVD) on a substrate that is partially covered by a patterned graphene growth barrier that guides the growth of graphene.

[0031] Patent Document 13 proposes a method for producing a porous graphene layer having an average size pore in the range of 5 nm to 900 nm and a thickness of less than 100 nm, including a step of preparing a catalytically active copper substrate that catalyzes graphene formation under chemical vapor deposition conditions, wherein a plurality of catalytically inactive domains having a size essentially corresponding to the size of the pores of the resulting porous graphene layer are provided on or on the surface of the catalytically active substrate, and a step of performing chemical vapor deposition using a carbon source in the gas phase to form a porous graphene layer on the surface of the catalytically active substrate, wherein the pores of the graphene layer are formed in situ due to the presence of the catalytically inactive domains.

[0032] In the field of graphene CVD growth, Dong et al (Non-Patent Document 1) found that the carbon solubility in metals is an important factor affecting uniform graphene growth by chemical vapor deposition (CVD) at high temperatures. However, at low temperatures, it has been found that the carbon diffusion rate (CDR) on the metal catalyst surface has a greater impact on the number and uniformity of graphene layers compared to carbon solubility. The CDR rapidly decreases with decreasing temperature, resulting in heterogeneous multilayer graphene. In this study, based on the following characteristics, a Ni-Cu alloy sacrificial layer was used as a catalyst. Cu was selected to increase the CDR, and Ni was used to obtain high catalytic activity. Graphene was grown on the surface of a Ni-Cu alloy under low pressure using methane as a carbon source by plasma-accelerated CVD. The optimal composition of the Ni-Cu alloy of 1:2, i.e., a ratio of 33% Ni, was selected experimentally. In addition, the plasma output was optimized to improve the graphene quality. Together with the in situ sacrificial metal layer etching method previously reported by the present inventors, relatively uniform wafer-sized patterned graphene was directly obtained on a 2-inch SiO 2 / Si substrate at low temperature (about 600 °C).

[0033] Losurdo et al (Non-Patent Document 2) reported that understanding the chemical vapor deposition (CVD) kinetics of graphene growth is important for the progress of graphene processing and achieving better control of the thickness and properties of graphene. From the perspective of improving the quality of large-area graphene, the CVD kinetics using a CH 4 -H 2 precursor has been investigated in real time on both polycrystalline copper substrates and nickel single substrates. The role of hydrogen in differentiating the growth kinetics and thickness of graphene on copper and nickel has been emphasized. Specifically, the growth kinetics and mechanism fall into the framework of competition of in-diffusion of carbon and hydrogen, where the competitive dissociative chemisorption of H 2 and the dehydrogenative chemisorption of CH 4 , and the internal diffusion of hydrogen is faster on copper than on nickel, and the carbon diffusion is faster on nickel than on copper. Hydrogen promotes the dehydrogenation of CH 4It has been shown to act as an inhibitor of dehydrogenation, contribute to suppressing deposition on the copper substrate, and degrade the quality of graphene. Furthermore, evidence is also provided for the role of hydrogen in the formation of out-of-plane C-H defects in CVD graphene on Cu. Conversely, the recombination of hydrogen that reoccurs promotes CH 4 decomposition in the case of Ni. Better understanding the dynamics of graphene growth and providing other elements can help define the optimal CH 4 / H 2 ratio and ultimately contribute to improving the thickness uniformity of the graphene layer even on polycrystalline substrates.

[0034] Samir Al-Hilfi (Non-Patent Document 3) investigated the influence of the C solubility in the catalyst substrate on the CVD growth of graphene. The Cu-Ni alloy exhibits complete solid solubility over its composition range and can be used to investigate the influence of C solubility on graphene growth. Graphene is grown on Cu-Ni alloys of composition Cu, Cu70-Ni30, Cu55-Ni45, Cu33-Ni67, and Ni in a high-temperature wall CVD reactor. Thus, in all cases, the substrate either contained no Ni or at least 30% Ni. First, growth was achieved on pure metals (Cu and Ni) using CH 4 as the C source, and the fabricated films were characterized by Raman spectroscopy and scanning electron microscopy (SEM). The C profile within the substrate bulk was measured by glow discharge optical emission spectroscopy (GDOES). The latter showed the difference in the bulk C content between Cu and Ni, which reflects the influence on the graphite film on the surface. In the CVD growth of graphene on Cu-Ni alloys, as the Ni content increased, a transition from bilayer graphene (BLG) to few-layer graphene (FLG) surface coverage was shown, accompanied by an increase in the diffusion of C in the bulk and the incubation time. The cooling rate showed a significant effect on the graphene surface coverage rate, and the effect varied with the Ni content. Fluid flow simulation showed that the gas velocity under the substrate was very low and the mass transfer to the bottom surface of the substrate decreased. Gas-phase dynamics simulation revealed the influence of the gas residence time on the concentration of active species, and furthermore, the concentration increased towards the downstream of the flowing gas. Finally, CH4 / H 2 The surface reaction of the hybrid model showed good agreement with experimental observations at low growth pressures but failed at high growth pressures.

[0035] In summary, the existing technologies for waterproof breathable membranes can be improved and there is room for improvement. For the purpose of customer comfort and protection of the materials under clothing or packaging, epoch-making technologies are needed to obtain vapor permeability (rapid gas-phase transport) while maintaining liquid barrier properties. Porous graphene membranes have been proposed for such applications, analyzed, and compared with conventional breathable membranes, and have been shown to exhibit better breathability. However, the existing processes for fabricating suitable porous graphene membranes are not necessarily fully suitable for scale-up and industrial processes.

Prior Art Documents

Patent Documents

[0036]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

[0037] [Non-Patent Document 1] The Growth of Graphene on Ni-Cu Alloy Thin Films at a Low Temperature and Its Carbon Diffusion Mechanism, Nanomaterials (Basel). 2019 Nov; 9(11): 1633 [Non-Patent Document 2] Graphene CVD growth on copper and nickel: role of hydrogen in kinetics and structure, Phys. Chem. Chem. Phys., 2011, 13, 20836-20843 [Non-Patent Document 3] Chemical vapour deposition of graphene on Cu-Ni alloy, Thesis, The University of Manchester, 2018 [Summary of the Invention]

[0038] An object of the present invention is to provide a new method for producing a highly porous graphene layer for use as the above-mentioned film and a multilayer structure including such a porous graphene layer. Further, it is also an object to provide a corresponding tool for the production process, particularly a catalyst substrate or the like. It is also an object of the present invention to propose a corresponding porous graphene layer and a multilayer structure including such a porous graphene layer.

[0039] The newly proposed method for fabricating a graphene layer is particularly characterized by being a simple and reliable process that enables the reuse of the catalyst substrate, allows not only for a simple synthesis process of the graphene layer itself but also for subsequent transition to a multi-layer structure. The resulting graphene layer is particularly characterized by having both a high porosity and a high thickness and / or mechanical rigidity (mechanically robust) either alone or in combination with a non-woven fabric such as a specific woven fabric or polyurethane non-woven fabric.

[0040] The proposed method includes the following elements: 1. Preparation of a specific copper / nickel alloy catalyst substrate; 2. Generation of the topology of a catalyst-inactive material in the form of catalyst-inactive nanostructures on such a catalyst substrate; 3. Synthesis of a porous graphene layer on a copper / nickel alloy catalyst substrate having such a topology of the catalyst-inactive nanomaterial; 4. Separation and exfoliation of the porous graphene layer from the catalyst substrate, preferably by an electrochemical separation method; 5. Mechanical exfoliation of the porous graphene layer from the catalyst substrate; 6. Application of such a porous graphene layer to a non-woven or porous fabric.

[0041] These individual steps can be carried out as follows.

[0042] 1. Preparation of the Cu-Ni alloy: Prepare a Cu catalyst, for example, a Cu catalyst purchased from Alfa Aesar (copper foil, 0.025 mm, 99.8%, product number 49686). Deposit Ni films of various thicknesses from 10 nm to 2.2 μm or 50 nm to 300 nm onto the as-received commercial Cu catalyst in a vacuum using an electron beam evaporator or sputtering (e.g., FHR, Pentaco 100, Ni purity 99.95%, 3×10 -3Deposit by mbar(0.3 Pa). The sputtering pressure is about 0.006 mbar(0.6 Pa) with 200 sccm of Ar. Deposit the obtained Ni film with a 0.25 kW DC plasma for 10 nm to 2.2 μm or 50 nm to 300 nm. Deposit the two-layer structure of the Ni / Cu catalyst in a chemical vapor deposition (CVD) system (e.g., Graphene Square. Inc, TCVD-RF100CA) under low pressure (e.g., 200 mTorr(26.7 Pa)), using, for example, 50 sccm of H 2 Anneal at, for example, 1000 °C for, for example, 1 hour using, for example, to convert it into a binary metal alloy (Cu-Ni alloy).

[0043] The Ni concentration ranges from over 0.04% to 10%, or preferably from over 0.04 wt% to 2 wt%, or further from 0.1% to 10%, preferably from 0.2% to 8% or 0.3% to 5%, typically from 0.4% to 3%. Particularly preferably, the catalytically active substrate has a nickel content in the range of 0.06 wt% to 1 wt% or 0.08 wt% to 0.8 wt% that is complemented to 100 wt% by the copper content. The remainder is Cu (for this reason, Cu is in the widest range 99.96% to 90%, in the typical range less than 99.94% to 99% or 99.6% to 97%, and this remainder may be present in the starting Cu foil or starting Ni, and contains no trace impurities that would be less than 0.05 wt% or less than 0.02 wt% in the final substrate). The range of the Ni content is determined by the initial Ni thickness. The typical working content of Ni is preferably in the range of 0.5% to 2%.

[0044] 2. Conversion of the W thin film to the W nanostructure: According to the previous section, by sputtering in vacuum or an electron beam evaporator (e.g., FHR, Pentaco 100, W purity 99.95%), for example, an electron beam evaporator or sputtering in vacuum (e.g., 3×10 -3A thin film of W (thickness 1 nm to 10 nm) is deposited on a Cu-Ni alloy using a pressure of, for example, 0.3 Pa (mbar). The sputtering pressure is, for example, 0.2 Pa (0.002 mbar) with 100 sccm of Ar. The thin film of W is deposited 1 nm to 10 nm using, for example, a 0.25 kW DC plasma. The W / Cu-Ni alloy is attached to the center of a 4-inch quartz tube chamber installed inside a CVD system (for example, Graphene Square, Inc, TCVD-RF100CA). After evacuating the chamber to reach a pressure of, for example, 6.00 Pa (45 mTorr), it is purged with an inert gas, for example, N 2 (for example, 100 sccm) for, for example, 5 minutes, usually at room temperature. After purging, the chamber is placed under vacuum again (for example, 6.00 Pa (45 mTorr)), and then, for example, Ar and H 2 (800 sccm and 40 sccm respectively) to increase the pressure with a mixed gas. Thereby, the W thin film is converted into a W nanostructure (NS). The NS is based on symmetric W nanoparticles and asymmetric W nanowalls in various ways due to various degrees of interparticle aggregation. The W / Cu-Ni alloy is carefully annealed at a high temperature (for example, 750 °C to 950 °C or 800 °C to 900 °C) for a long time, for example, including ramping for 1 hour under 533 Pa (4 Torr) with, for example, 800 sccm of Ar and 40 sccm of H 2 by continuous supply.

[0045] 3. Synthesis of highly porous graphene After the W nanostructure appears in the process according to the previous section, in a low-pressure CVD system under 533 Pa (4 Torr), for example, 300 sccm of Ar and 40 sccm of H 2 and a hydrocarbon source, for example, 40 sccm of methane, are introduced into the chamber. The growth period is carefully controlled, for example, from 5 minutes to 120 minutes, according to the desired level of porosity or thickness. Then, the furnace is filled with Ar and H 2Program to cool down to room temperature under flowing. Under these conditions, a graphene layer thickness of approximately 10 nm can be obtained with a total CVD time of 120 minutes. With a CVD time of 5 minutes, a graphene layer thickness of less than approximately 1 nm can be obtained, although this may also depend on further parameters.

[0046] 4. Electrochemical exfoliation of highly porous graphene by electrochemistry: After the growth of highly porous graphene, a pre-leaching process of the as-grown highly porous graphene, for example, in 0.1 M NaOH, is carried out for, for example, 10 minutes to 60 minutes, usually at a mild temperature (40 °C to 60 °C). Subsequently, the sample material can be rinsed with DI water and dried before the next step. Another material such as poly(methyl methacrylate) (PMMA), or a polymer porous membrane, for example, polyurethane (PU; such as Finetex ENE), etc., is assembled as a support layer on the sample. It has been found that a NaOH concentration range of 0.5 M to 1.5 M is suitable, with lower concentrations resulting in unacceptably long pre-leaching times and higher concentrations decomposing the copper / nickel substrate.

[0047] PMMA: PMMA (950k, AR-P 672.03) can be used and, for example, spin-coated at 4000 rpm for 40 seconds, and the PMMA / highly porous graphene can be baked at 110 °C for 1 minute.

[0048] Isopropyl alcohol can be applied to the laminated PU / as-grown highly porous graphene on the Cu-Ni alloy to achieve a close interfacial adhesion during drying. A controlled melt adhesion process may also be used.

[0049] The sample and the Pt electrode are connected to the respective anode and cathode of a power supply (for example, GW Instek, GPR-3060D) in, for example, an aqueous NaOH solution (1 M).

[0050] Then, by applying a voltage (3 V to 10 V), H electrochemically generated at the interface between the highly porous graphene and the surface of the catalyst 2Bubbles can exfoliate highly porous graphene with a support material from the designed catalyst.

[0051] Reuse of the catalyst substrate: After the electrochemical exfoliation process, the Cu-Ni alloy can be reused to repeatedly grow highly porous graphene.

[0052] 5. Mechanical exfoliation of highly porous graphene The as-grown highly porous graphene on the Cu-Ni alloy can be immersed in 0.1 M NaOH at a mild temperature (40 °C to 60 °C) for 10 minutes to 60 minutes or 15 minutes to 60 minutes to remove / dissolve the W NS and separate the bond between the highly porous graphene and the surface of the Cu-Ni alloy. After the preliminary leaching process, the sample can be rinsed with DI water and dried with an N 2 gas flow. The sample can be directly attached at room temperature by lamination or a pressing tool to an adhesive tape, such as a thermal release tape (e.g., Revalpha, Nitto Denko Corporation) or a water-soluble tape, to improve adhesion. The adhesive tape is mechanically exfoliated from the catalyst together with the adhered highly porous graphene.

[0053] Reuse of the catalyst substrate: After the mechanical exfoliation process, the Cu-Ni alloy can be reused to repeatedly grow highly porous graphene.

[0054] 6. Interface of the polyurethane nonwoven fabric: 1. Characteristic filament diameter: 314 nm (standard deviation: 190 nm) (The characteristic filament diameter is defined as the average diameter of the individual filaments of the nonwoven material) 2. Characteristic pore width: 1281 nm (standard deviation: 603 nm) (The characteristic pore width is defined as the average width of the individual topmost pores in the nonwoven material).

[0055] More generally, the present invention according to the first aspect is a method for producing a porous graphene layer having a thickness of less than 100 nm and having pores with an average characteristic width in the range of 1 nm to 1000 nm, preferably in the range of 5 nm to 900 nm, preparing a catalytically active substrate that catalyzes graphene formation under chemical vapor deposition conditions, on which a plurality of catalytically inactive domains having a nanostructure essentially corresponding to the shape of the pores of the resulting porous graphene layer are provided on the surface; performing chemical vapor deposition using a carbon source in the gas phase to form a porous graphene layer on the surface of the catalytically active substrate, wherein the pores of the porous graphene layer are formed in situ due to the presence of the catalytically inactive domains; relates to a method comprising.

[0056] The average characteristic width of the pores is defined and measured as follows.

[0057] Since the shape of the pores becomes elongated and non-uniform due to the W nanostructure, it is difficult to determine the pore diameter. Therefore, the characteristic width is selected and defined as the widest width of the pores, rather than the pore diameter. The characteristic width of the pores was extracted using image analysis software (ImageJ) for a scanning electron microscope (SEM) image. The porous graphene was transferred onto a SiN x chip containing holes with a diameter of 4 μm to prepare a self-supporting section suitable for clear image interpretation. Then, five representative SEM images of the porous graphene were taken over 1.14 μm 2 to visualize a clear difference in contrast between the pores and the surrounding graphene (for example, the pores are black and the graphene is gray). Since the characteristic width of the pores is several tens of nm, a high-magnification SEM image was required. Thereafter, based on the SEM image, the widest width of each pore opening was measured, and the average of the measured widths was subsequently calculated.

[0058] According to the present invention, in particular, the catalytically active substrate is a copper-nickel alloy substrate having a copper content in the range of 85 wt% to 98 wt% or 90 wt% to 99.9 wt%, and a nickel content in the range of 2 wt% to 15 wt% or in particular more than 0.04 wt% to 2 wt%, and the copper content and the nickel content complement each other so as to be 100 wt% of the catalytically active substrate.

[0059] Unexpectedly, it has been found that the use of such a catalytically active substrate alloy enables the production of a relatively thick graphene layer having a higher porosity than the porous graphene layer that has been available heretofore. Without being bound by any theoretical explanation, this particular alloy can impart a particular topology of catalytically inactive domains to the surface, and as a result of this topological structure, it seems possible to produce a thicker graphene layer having excellent gas permeability and liquid barrier properties.

[0060] According to a first preferred embodiment of the proposed method, the catalytically active substrate has a nickel content in the range of 0.06 wt% to 1 wt% or 0.08 wt% to 0.8 wt%.

[0061] The catalytically active substrate can be produced, for example, preferably by using electrochemical plating, electron beam evaporation, PVD or sputtering, applying a nickel film having a thickness in the range of 0.01 μm to 2.2 μm, preferably in the range of 25 nm to 300 nm or 20 nm to 500 nm, preferably in the range of 50 nm to 300 nm, preferably to a pure copper foil having a thickness in the range of 0.01 mm to 0.10 mm or 0.02 mm to 2 mm, preferably in the range of 0.02 mm to 0.04 mm and in particular having a purity of more than 99.5%. Subsequently, this structure is preferably subjected to an annealing process at a temperature in the range of 800 °C to 1200 °C, preferably in the range of 900 °C to 1100 °C, for a time in particular in the range of 5 minutes to 120 minutes, preferably in the range of 10 minutes to 60 minutes or 30 minutes to 90 minutes.

[0062] The porous graphene layer preferably has a thickness in the range of less than 50 nm, preferably in the range of 1 nm to 20 nm, particularly in the range of 5 nm to 15 nm or 7 nm to 12 nm.

[0063] At a preferred nickel concentration, the corresponding graphene preferably has an areal porosity (defined as the ratio of the total area of the pores to the total projected area of the layer) in the range of more than 2.5%, preferably more than 5%, preferably in the range of 10% to 70%, and simultaneously has a thickness in the range of more than 1 nm, preferably more than 2 nm, preferably in the range of 2 nm to 15 nm. More preferably, the porous graphene layer has an areal porosity defined as the areal fraction of the pores in the total graphene layer of at least 10%, preferably at least 15%, more preferably at least 20% or at least 25%, or at least 40%.

[0064] According to yet another preferred embodiment, a plurality of catalytically inactive domains are provided on the surface of the catalytically active substrate, preferably by applying an essentially continuous tungsten layer using sputtering, electron beam evaporation or PVD. Preferably, this tungsten layer has a thickness in the range of more than 1 nm, preferably more than 3 nm, more preferably more than 5 nm, or in the range of 1 nm to 10 nm, preferably in the range of 5 nm to 10 nm. Subsequently, this structure is subjected to an annealing process at a pressure below atmospheric pressure, preferably below 100 mTorr (13.3 Pa) or below 4 Torr (533 Pa), particularly in a reducing atmosphere, preferably in the presence of an inert gas such as argon gas or nitrogen gas combined with hydrogen gas, to convert the tungsten film into a plurality of catalytically inactive domains. Typically, the annealing is carried out at a temperature in the range of 700 °C to 1100 °C, more preferably in the range of 750 °C to 950 °C or 800 °C to 900 °C, and typically over a time in the range of 10 minutes to 180 minutes, preferably in the range of 10 minutes to 60 minutes or 50 minutes to 100 minutes.

[0065] According to a preferred embodiment, the method is adapted such that a catalytically inactive domain having an average characteristic width in the range of 1 nm to 1000 nm, preferably in the range of 10 nm to 100 nm, more preferably in the range of 10 nm to 50 nm, or preferably having an average characteristic width in the range of 5 nm to 900 nm, preferably in the range of 10 nm to 200 nm, more preferably in the range of 10 nm to 100 nm is obtained.

[0066] According to a second aspect of the invention, the invention also relates to a catalytically active substrate structure obtained by using the method detailed above, which is suitable for use in the graphene layer fabrication process detailed above, independently of the above method.

[0067] The chemical vapor deposition process for forming the graphene layer can be carried out using a carbon source in the gas phase during the formation of a porous graphene layer on the surface of the catalytically active substrate. The pores of the graphene layer are preferably formed in situ by the presence of a catalytically inactive domain using methane gas as the carbon source in the co - existence of argon gas and hydrogen gas, preferably under a reduced pressure of less than 50 Torr (6670 Pa), preferably less than 5 Torr (667 Pa), and preferably over a time in the range of 10 minutes to 120 minutes, preferably less than 60 minutes, more preferably less than 50 minutes, most preferably less than 35 minutes. This graphene layer deposition process is preferably carried out over a time that enables the production of a graphene layer with an average thickness in the range of more than 5 nm, preferably in the range of 8 nm to 12 nm.

[0068] The porous graphene layer can be removed from the catalytic substrate and further applied to a porous, preferably non - woven or woven support substrate. Preferably, for the removal of the graphene layer, a support carrier layer is first applied to the surface of the graphene layer opposite to the catalytic substrate, and after removing the sandwich of this carrier layer and the graphene from the catalytic substrate, this structure is applied directly or indirectly to a porous, preferably non - woven or woven support substrate, and subsequently the temporary carrier layer can be removed if necessary.

[0069] Before removing the graphene layer, the layered structure of the catalyst substrate having a catalytically inactive domain and the grown graphene layer can preferably be subjected to a preliminary leaching process that weakens or removes the bond between the graphene layer and the catalyst substrate and / or the catalytically inactive domain.

[0070] Preferably, this preliminary leaching step includes forming an oxide layer at least partially, preferably essentially completely, between the graphene layer and the catalyst substrate and removing the catalytically inactive domain.

[0071] The preliminary leaching step can preferably be carried out by subjecting the substrate having the graphene layer to a basic or acidic environment, preferably in water, more preferably at a pH less than 6 or greater than 7, preferably greater than 10, more preferably greater than 12. Most preferably, for the preliminary leaching, a 0.01 M - 0.5 M aqueous NaOH solution is used at a temperature in the range of 40°C - 60°C for a time in the range of 10 minutes - 60 minutes, optionally followed by rinsing with water and drying.

[0072] Preferably, after the preliminary leaching step, an electrochemical method can also be used to remove the graphene layer, for example, by immersing the layered structure of the catalyst substrate having the catalytically inactive domain and the graphene layer in an electrolyte and applying an electrochemical potential to the substrate with respect to a counter electrode in the same electrolyte.

[0073] The graphene layer can be attached to a porous, preferably non - woven or woven support substrate that, after or for the purpose of removal from the catalyst substrate, preferably has a characteristic filament diameter in the range of 200 nm - 2000 nm, preferably in the range of 300 nm - 1000 nm, particularly with a standard deviation of less than 500 nm, and / or a characteristic pore diameter in the range of 500 nm - 50000 nm, preferably in the range of 1000 nm - 10000 nm, particularly with a standard deviation of less than 1000 nm.

[0074] Preferably, a non-woven or woven support substrate is attached to the graphene layer using solvent-induced adhesion or thermal adhesion. Preferably, the adhesion to the non-woven fabric is achieved using isopropanol-mediated adhesion and annealing and / or heat treatment.

[0075] According to a third aspect of the present invention, the present invention relates to a graphene layer on at least one support substrate that can be obtained or is obtained using the method detailed above.

[0076] Such a graphene layer typically has a thickness in the range of less than 50 nm, preferably in the range of 1 nm to 20 nm, particularly in the range of 5 nm to 15 nm or 7 nm to 12 nm, and / or has an areal porosity in the range of at least 10%, preferably at least 15%, more preferably at least 20% or at least 25% or at least 30% or at least 40%.

[0077] According to yet another aspect of the present invention, the present invention relates to a textile piece or clothing item in the form of clothing, preferably having at least one graphene layer produced using the above method and having water resistance and / or water repellency and / or breathability, such as clothing (e.g., jackets, trousers, gloves, hats, etc.).

[0078] Finally, the present invention relates to the use of graphene obtained using the method detailed above as a semi-permeable membrane, particularly for textile applications in the field of clothing, or for providing a waterproof barrier particularly in electronic devices and / or portable devices, or to the graphene layer itself as detailed above.

[0079] Further embodiments of the present invention are defined in the dependent claims.

[0080] Preferred embodiments of the present invention are described below with reference to the drawings, which are provided to illustrate preferred embodiments of the present invention and are not intended to limit the present invention.

Brief Description of the Drawings

[0081]

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[0082] Figure 1 schematically shows the proposed method in individual steps. On the catalytic copper / nickel substrate, a layer 12 of a catalytically inert material, in particular a layer 12 of tungsten, is provided on the surface in the first step, specifically in the tungsten deposition step 11. Subsequently, after this coated substrate 1 is optionally introduced into a housing in step 14, it is subjected to a thermal annealing step under reducing conditions. As a result, a pattern of catalytically inert domains 2 is generated on the surface of the catalytic substrate 1. In the next step 4 of growing a graphene layer on the substrate, the substrate is again subjected to chemical vapor deposition of methane, optionally within a housing 13, to form a porous graphene layer 5 in which catalytically inert domains 2 locally intervene to form holes for future porosity. In the next step 16 of removing the housing (if used), after releasing this layered substrate, it is subjected to a PMMA coating step 17. The substrate layer 18, in this case the PMMA coating, is applied, for example, by spin coating or curtain coating. Pretreatment can be carried out as will be further described below before this step. Subsequently, as will be described in more detail below, a step 19 of removing the substrate is again carried out using mechanical and / or electrochemical methods. Then, this sandwich of the coating layer 18 and the porous graphene layer 5 is applied to a desired carrier substrate 21, such as a non-woven or porous fabric. This is shown in a cross-sectional view 22 , and in a top view 23 schematically showing the porosity of the graphene layer using dots.

[0083] Thick porous graphene and thick highly porous graphene are synthesized using a binary metal alloy that provides a high catalytic effect on the decomposition of hydrocarbon gases and favorable growth kinetics. For example, nickel films 8 of various thicknesses are deposited by physical vapor deposition on a Cu metal substrate 7, which is the most widely used catalyst, in a thickness range of 50 nm to 300 nm. Subsequently, as shown in Figure 2, the two-layer Ni / Cu catalyst is annealed in a CVD reactor to convert it into a Cu-Ni alloy substrate 1.

[0084] After the transformation of the Cu-Ni alloy, X-ray photoelectron spectroscopy (XPS) was performed using a Sigma 2 spectrometer (Thermo Scientific) with polychromatic Mg Kα X-rays and a hemispherical analyzer to measure the actual Ni content on the surface of the alloy. The binding energy was calibrated with C 1s = 284.8 eV. The results of the Ni content are as follows: 0.43% for 50 nm of Ni, 0.68% for 150 nm of Ni, 1.43% for 300 nm of Ni, and 2.73% for 500 nm of Ni.

[0085] The progress of the catalytically inert material on the substrate can be distinguished by the process temperature as shown in FIGS. 3 and 4. In FIG. 3, first, a thin film 12 of the catalytically inert material is deposited by physical vapor deposition in a thickness range of 1 nm to 10 nm. Subsequently, the obtained material is annealed in a CVD reactor at a temperature higher than 900 °C. Nanoparticles of the catalytically inert material are formed without any lithography and etching processes. The size and density of the nanoparticles of the catalytically inert material can be controlled by the thickness of the initially deposited film 12 of the catalytically inert material, the annealing temperature, pressure, and the duration of the annealing process.

[0086] In Fig. 4, similar to Fig. 3 above, a thin film 12 of a catalytically inactive material was deposited by physical vapor deposition in an amount of 1 nm to 10 nm. Subsequently, the resulting material was annealed at a high temperature of less than 900 °C in a CVD reactor. Annealing at a lower temperature generates a nanowall structure of the catalytically inactive material together with nanoparticles. Such a combination of nanoparticles and nanowalls results in a higher porosity than that of nanoparticles alone because the porosity of the graphene layer 5 is approximately proportional to the coverage of the catalytically inactive material. A decrease in the annealing temperature enables partial de-wetting rather than complete de-wetting of the catalytically inactive material. Therefore, a new structure of the topology of the catalytically inactive material is achieved without any lithography and etching processes. Furthermore, the ratio of nanoparticles to nanowalls of the catalytically inactive material, as well as the shape, size, and density of the nanoparticles and nanowalls, can be controlled by the thickness of the initial film of the catalytically inactive material, the annealing temperature, the pressure, and the duration of the annealing process.

[0087] Except for the morphological form of the nanostructure of the resulting catalytically inactive material as shown in Fig. 5 (porous graphene) and Fig. 6 (highly porous graphene), a CVD process is performed to produce either porous graphene or highly porous graphene by synthesizing graphene on these two types of the above-mentioned catalytic substrates.

[0088] Depending on the catalytically inactive material, the (chemical) bond between the edge of the graphene and the catalytically inactive material may be stronger than the bond between the graphene and the substrate. When such a strong bond occurs, a pre-leaching process to be described later may be advantageous. As a result, in Fig. 7, not only is the catalytically inactive material dissolved and removed, but also a natural oxide layer 9 of the substrate 1 is formed, and the bond between the graphene 5 and the substrate 1 is relaxed. This promotes the peeling of the graphene layer 5 from the substrate 1, enabling the reuse of the substrate.

[0089] Grown porous graphene and highly porous graphene can also be removed by an electrochemical or mechanical approach schematically shown in FIGS. 8 and 9, instead of etching the metal catalyst.

[0090] In FIG. 8, after the pre-leaching process and the formation of the oxide layer 9, an adhesive material layer 10 based on PMMA, PVA, PC, etc. can be coated on the grown porous graphene 5 and highly porous graphene 5 on the substrate 1. Subsequently, this material composite composed of the porous graphene layer on this support layer 10 5 is removed by applying a shearing force as schematically shown by the arrow 24. Subsequently, it can be immersed in an electrolyte such as a basic solution or an acid solution containing an electrically connected metal. The support material 10 having porous graphene or highly porous graphene can be peeled off by the generation of hydrogen or oxygen bubbles.

[0091] In FIG. 9, after the pre-leaching process, a support material 25 such as PMMA, PVA, PC, etc. or an adhesive material such as a thermal release tape or an adhesive tape can be directly applied onto the grown porous graphene and highly porous graphene 5 on the substrate 1. Then, the porous graphene and highly porous graphene 5 having the support or adhesive material 25 can be peeled off by the mechanical force 24 for the relaxation of the bond between the graphene 5 and the metal catalyst 1 resulting from the generation of the natural oxide 9 during the pre-leaching process, as also shown in FIG. 8c. In either case, the porous graphene and highly porous graphene 5 can be transferred onto any substrate 10 / 25 such as a polymer substrate, a porous substrate, glass, a wafer, etc. by dissolving the support material or separating the adhesive material.

[0092] For electrochemical removal, the substrate 1 having or not having the oxide layer 9, the graphene layer 5, and a further substrate layer 25 is immersed in the electrolyte 27 in the same way as the counter electrode 26, and the required potential is established between the substrate 1 and this counter electrode 26. Thereby, after the graphene layer 5 on the substrate 25 is peeled off, it can be subsequently taken out from the electrolyte and used further.

[0093] General scheme for fabricating nanostructures of catalytically inert materials on binary metal alloys: Physical vapor deposition (sputtering, FHR, Pentaco 100, Ni purity 99.95% or electron beam evaporator, Evatec) was performed to deposit a nickel film on a base catalyst substrate (copper foil, 0.025 mm, 99.8%, product number 49686, Alfa Aesar) to obtain a binary metal alloy (Cu-Ni alloy). This was achieved by thermal annealing at a high temperature (800 °C to 1000 °C) in a CVD system (Graphene Square. Inc, TCVD-RF100CA). The concentration of Ni on the surface of the binary metal alloy can be controlled by the thickness of the initial Ni film and / or the annealing temperature. For example, a 50 nm thick Ni film becomes 0.43 wt% in 99.57% copper of the substrate at 1000 °C for a time in the range of 10 minutes to 60 minutes. When using an initial Ni layer thickness of 300 nm on a copper substrate, as the thickness of the Ni film increases, the concentration of Ni increases up to 1.43%.

[0094] A thin film 12 of a catalytically inert material (tungsten) is deposited on the binary metal alloy 1 by physical vapor deposition such as sputtering or electron beam evaporation, or in some cases by spraying nanoparticles on the binary metal alloy. Then, a thermal annealing process is carried out at various temperatures (700 °C to 950 °C) to convert the thin film into nanostructures such as nanoparticles and / or nanowalls. This can be explained by solid dewetting where a very small amount of material diffuses laterally on the surface of the substrate by thermal annealing, resulting in nanoparticles and / or nanowalls by aggregation and Ostwald ripening.

[0095] As an example, in Figure 10, most of the W nanoparticles on the Cu-Ni alloy are successfully demonstrated at a higher temperature (above 900 °C). When the temperature is less than 900 °C, a mixture of W nanoparticles and W nanowalls occurs on the Cu-Ni alloy as shown in Figure 11.

[0096] General Scheme for CVD Synthesis of Porous Graphene and Highly Porous Graphene: To synthesize a porous graphene and / or highly porous graphene layer, a two-component metal alloy 1 having a thin film 12 of a catalyst-inactive material (tungsten) is placed into a CVD system.

[0097] The bilayer metal catalyst is annealed in an Ar / H 2 environment to form tungsten-based nanostructures. Then, porous graphene and / or highly porous graphene is CVD-grown by introducing a certain amount of a carbon source (ethylene, acetylene, or methane), ensuring complete coverage of the graphene on the two-component metal alloy but not on the tungsten domains. The tungsten domains may be converted into a carbide material, which is a preferred form for absorbing the carbon precursor instead of growing graphene on top of the tungsten.

[0098] The porosity of the graphene can be controlled by the morphology of the W nanostructures, which may be affected by the annealing and growth temperatures. The thickness of the porous graphene and highly porous graphene can be controlled simply by the growth time, process pressure, or the amount of the carbon source.

[0099] For example, to synthesize porous graphene, a bilayer W / Cu-Ni alloy is annealed at 930 °C under 4 Torr (533 Pa) using 800 sccm of Ar and 40 sccm of H 2 to convert the thin film of W into the W nanoparticles shown in FIG. 10. After the formation of the W nanoparticles is complete, 40 sccm of CH 4 is introduced into the chamber together with 300 sccm of Ar and 40 sccm of H 2 under 2 Torr (266 Pa). Growth is carried out for 10 minutes to fabricate a 5-nm-thick porous graphene. FIG. 12 shows the porous graphene transferred onto a SiO 2 / Si substrate, showing relatively circular holes in the graphene layer.

[0100] For the synthesis of highly porous graphene, the annealing and growth temperatures are lowered to 800 °C. In Figure 11, under 4 Torr (533 Pa), at 800 °C, 800 sccm of Ar and 40 sccm of H 2 After the W nanostructure was completed by thermal annealing using, under 4 Torr (533 Pa), 40 sccm of CH 4 , 300 sccm of Ar and 40 sccm of H 2 were used to synthesize highly porous graphene for 30 minutes, and 10-nm-thick highly porous graphene was obtained. Figure 13 shows free-standing highly porous graphene on a SiN x membrane chip. Compared with porous graphene, very dense, small, and irregularly shaped pores are observed.

[0101] Characterization of the porosity and thickness of highly porous graphene: The porosity and thickness of porous graphene and highly porous graphene may be affected by growth parameters such as the initial thickness of the Ni film, the initial thickness of the W thin film, and the growth time.

[0102] Ni thickness: To investigate the effect of Ni film 8 on the porosity and thickness, various Ni thicknesses from 50 nm to 300 nm were deposited on Cu foil 7 by physical vapor deposition and annealed at 1000 °C to form Cu-Ni alloy 1. On the alloy based on a 4-nm-thick W film (with Ni contents of 0.43%, 0.68%, and 1.43% for 50 nm, 150 nm, and 300 nm respectively, annealed at 1000 °C for 1 hour), highly porous graphene 5 was synthesized under 4 Torr (533 Pa) using 40 sccm of CH 4 , 300 sccm of Ar and 40 sccm of H 2It is grown at 800 °C for 30 minutes using [the relevant method]. Then, the catalyst is etched away, and the resulting film is transferred onto the SiN film to accurately observe the porosity and thickness. The SEM images in Fig. 15 show free-standing highly porous graphene grown on a Cu-Ni alloy from Ni films with thicknesses of (a) 50 nm, (b) 100 nm, and (c) 150 nm. The Cu-Ni alloy (50 nm of Ni) showed the highest porosity (over 30%) and the thickest graphene film (about 6 nm). In Fig. 14, as the Ni thickness increases, both the porosity and thickness of the graphene layer decrease to 20% and 4 nm, respectively. The porosity here is defined as the ratio of the total area of the pores to the total projected area.

[0103] Growth time: To explain the influence of the growth time on the porosity and thickness, various periods from 30 minutes to 60 minutes are applied, and high-porosity graphene is grown on a Cu-Ni alloy from a 50-nm-thick Ni film and a 4-nm-thick W film (with a Ni content of 0.43% for the 50-nm-thick Ni, annealed at 1000 °C for 1 hour) using [the relevant substances]. 4 and 300 sccm of Ar and 40 sccm of H 2 at 4 Torr (533 Pa) and 800 °C for 30 minutes. Then, the high-porosity graphene is transferred onto the SiN film, and the porosity and thickness are observed. Fig. 17 shows representative SEM images of free-standing high-porosity graphene grown for (a) 30 minutes, (b) 45 minutes, and (c) 60 minutes. As the growth period increases, the high-porosity graphene becomes thicker from 6 nm to 11 nm, but the porosity of the high-porosity graphene decreases from 30% to 5% as the graphene covers the W nanostructure as shown in Fig. 16.

[0104] W thickness: To investigate the influence of the thickness of the W film on the porosity and thickness of the graphene layer, a 50-nm-thick W film (with a Ni content of 0.43% for the 50-nm-thick Ni, annealed at 1000 °C for 1 hour), as well as [the relevant substances]. 4 and 300 sccm of Ar and 40 sccm of H 2Growth was carried out at 800 °C for 30 minutes under 4 Torr (533 Pa) using various W layer thicknesses from 2 nm to 6 nm. After the growth of highly porous graphene, the obtained film was transferred onto the SiN film, and the porosity and thickness were observed. The SEM images in Fig. 19 show free-standing highly porous graphene grown on a Cu-Ni alloy using (a) 2-nm-thick, (b) 4-nm-thick, and (c) 6-nm-thick W films. The 6-nm-thick W thin film achieved the highest porosity (about 40%) simultaneously with the thickest graphene film (about 10 nm). In the case of the 2-nm-thick W, as shown in Fig. 18, the porosity and thickness decreased significantly because graphene was grown on the W nanostructure.

[0105] Exfoliation of Porous Graphene or Highly Porous Graphene: After the growth of porous graphene or highly porous graphene, it is necessary to non-destructively exfoliate the graphene from the catalyst substrate and reuse the catalyst for the re-growth of porous graphene or highly porous graphene. For this purpose, two different methods of mechanical exfoliation and electrochemical exfoliation can be used.

[0106] In any case, the surface of the catalyst included a nanostructure of W that tended to bind more strongly to graphene than the catalyst (Cu-Ni alloy). As a result, mechanical exfoliation may not be possible, and there may be problems such as high voltage and long periods for electrochemical exfoliation. To address these problems, a preliminary leaching process of immersing the as-grown porous graphene or highly porous graphene in a low-concentration alkaline solution (0.1 M NaOH) can be applied. As shown in FIG. 20B, the nanostructure of W completely disappeared within 20 minutes as compared with the as-grown sample of FIG. 20A. Furthermore, the surface of the catalyst was slightly oxidized, resulting in relaxation of the bond between the graphene and the catalyst. At least 12 hours are required to mechanically exfoliate the graphene in its original state (non-porous), i.e., when there are no pores in the graphene, from the catalyst. This is because such a long period is required for oxidation of the surface of the catalyst. However, in the case of the present inventors, since the pores in the graphene are a path for the oxidant to penetrate the interfacial gap between the graphene and the surface, the pretreatment time for separating the graphene from the catalyst could be significantly reduced.

[0107] In FIG. 21A, after the preliminary leaching process, an adhesive material (here, a thermal release tape) is attached onto the sample. A laminator is used to improve the adhesiveness between the graphene and the tape. Since the interaction between the graphene and the surface of the catalyst is weak, the tape with porous graphene or highly porous graphene can be directly and mechanically exfoliated from the catalyst substrate. As shown in FIG. 21B, the graphene is peeled off together with the tape, and no graphene remains on the surface of the catalyst.

[0108] In addition to mechanical exfoliation, the conditions for electrochemical exfoliation could be relaxed at relatively low voltages (3 V to 5 V) and short times (1 minute to 3 minutes). First, a polymer support material such as PMMA is coated onto the sample. The polymer-coated sample is immersed in an electrolyte, such as NaOH, at various angles (30° to 90°) together with a counter electrode (Pt or graphite). A DC voltage is applied with the sample as the cathode and the counter electrode as the anode. When the voltage is applied, hydrogen bubbles are gently generated at the end of the cathode, and subsequently these bubbles can enter the interface between the graphene and the surface of the catalyst, making it possible to separate the graphene from the surface of the catalyst.

[0109] Assembly of porous graphene or highly porous graphene and a porous polymer support material: An assembly of porous graphene or highly porous graphene onto a porous polymer support material such as porous polyurethane (PU) or non-woven fabric is carried out. The porous PU non-woven fabric has a characteristic pore width of 1 μm to 10 μm, and the non-woven fabric material has a characteristic pore width of an average of 25 μm (the characteristic pore width is defined as the average of the widths of the individual pores at the top of the non-woven fabric material). To determine the characteristic pore width, an SEM image of the non-woven fabric material is taken and the pores at the top of the non-woven fabric are identified. Then, the characteristic width of the pores is measured using the ImageJ program. Here, too, the widest width of the pores is defined as the characteristic width. Since the graphene is in direct contact with and supported by the top filament structure, the geometric shape of the openings of the pores formed by the intersection of the top filaments is important. Therefore, the dimensions of the pores in the non-woven fabric represent the area of free-standing graphene between the contact points. The shorter the distance of the free-standing graphene, the greater the mechanical support and the strength against breakage due to bending and distortion.

[0110] To assemble the graphene and the porous polymer support material, two different methods were carried out: (1) isopropanol (IPA)-mediated adhesion and (2) heat treatment.

[0111] Graphene is bonded to the porous material using IPA. For example, place a porous PU non-woven fabric on top of the grown porous graphene or highly porous graphene attached to the catalyst. Gently drop IPA onto the porous PU to moisten the PU. As the IPA evaporates, intimate contact between the graphene and the porous PU is achieved. To further improve the adhesion, anneal the graphene and the porous PU at 120 °C for 10 minutes. The SEM image in Figure 22 shows highly porous graphene transferred onto the porous PU non-woven fabric. The highly porous graphene is supported on the filaments of the non-woven fabric, and the highly porous graphene layer floats in the openings between the filaments, showing a contrast difference between the pores and the bottom surface of the graphene, and further between the filaments.

[0112] Heat treatment can also be used to strongly bond graphene and the porous material. For example, preheat the grown porous graphene or highly porous graphene on the catalyst at a high temperature (150 °C - 180 °C) for 1 minute. Then, place a non-woven fabric material (such as polyurethane or other thermoplastic polymers like polyester) on top of the preheated graphene sample. Perform the heat treatment at a certain pressure (for example, place a mass of 100 g on a circular assembly with a diameter of 10 cm) for 10 minutes. In Figure 23, by using this method, a large sample (7×7 cm) of highly porous graphene can be transferred onto the PU non-woven fabric.

[0113] Finally, the obtained sample assembly can be mechanically or electrochemically peeled, or the catalyst can be dissolved and removed in a conventional chemical etching method.

[0114] Regrowth of highly porous graphene: Regrowth of highly porous graphene is carried out on the used Cu-Ni alloy from which the highly porous graphene has been peeled. Since the W nanostructure was dissolved and removed during the preliminary leaching process, a thin film of W is redeposited by physical vapor deposition before regrowth.

[0115] In Figure 24, a two-layer metal catalyst (W / used Cu-Ni alloy) is in Ar / H 2Anneal in an environment to achieve a tungsten-based nanostructure, and then repeatedly perform CVD growth of porous graphene and / or highly porous graphene while introducing a hydrocarbon gas. Therefore, a binary metal alloy can be reused by using the above-described non-invasive exfoliation method and redeposition of a thin film of W.

[0116] Detailed examples: Fabrication of a Cu / Ni substrate: A Cu-Ni alloy catalyst was formed to synthesize thick highly porous graphene. A Ni film was coated on an as-received Cu foil (0.025 mm, 99.8%, product number 49686, Alfa Aesar) by physical vapor deposition (PVD, sputtering or electron beam evaporation). The Ni film (thickness 50 nm to 500 nm or thickness 0.01 μm to 2.2 μm) was coated using sputtering (FHR, Pentaco 100, Ni purity 99.95%) for 85 seconds to 18700 seconds or 425 seconds to 4250 seconds depending on the thickness of the Ni film at 6×10 -3 mbar (0.6 Pa) with 200 sccm of Ar and a plasma power of 0.25 kW. The bilayer Ni / Cu was placed in a low-pressure chemical vapor deposition (LP-CVD, Graphene Sqaure. Inc, TCVD-RF100CA) system and annealed. The temperature of the furnace was first raised to a maximum of 1000 °C over 60 minutes with 50 sccm of H 2 . Further, to prevent unnecessary oxidation, the annealing process was performed at 1000 °C for 15 minutes in an H 2 environment. Then, mutual diffusion in the bulk state was achieved by complete dissolution on one side to complete the formation of the Cu-Ni alloy. The furnace was moved to a downstream position to rapidly lower the temperature to room temperature. A cooling rate of 50 °C / min was obtained while maintaining the same level of H 2 .

[0117] Fabrication of W nanostructures on the Cu / Ni substrate: After the formation of the Cu-Ni alloy, a thin film of W (2 nm to 10 nm) was deposited on the Cu-Ni alloy by sputtering (FHR, Pentaco 100, W purity 99.95%). The deposition was carried out at 3×10 -3 mbar (0.3 Pa) with 0.25 kW of DC power and 100 sccm of Ar for 15 seconds to 75 seconds to obtain various thicknesses.

[0118] The as-fabricated W / Cu-Ni alloy was placed in the center of the furnace of the LP-CVD system. The chamber was evacuated to 0.05 mTorr (6.67 mPa) by a turbo molecular pump to remove all the residual gases, and then the pressure was increased to a maximum of 45 mTorr (6.00 Pa) with 50 sccm of Ar. Then, the chamber was purged out with N 2 for 5 minutes and evacuated to 45 mTorr (6.00 Pa). The furnace was heated to a growth temperature of 750 °C to 950 °C or 800 °C to 950 °C while supplying 800 sccm of Ar and 40 sccm of H 2 After reaching the target temperature, the temperature was maintained for 10 minutes to stabilize it. During that time, the thin film of W was transformed into a W nanostructure by solid dewetting. Since there is no solid solubility between the Cu-Ni alloy and W, various forms of W nanostructures can be obtained without any preliminary lithography process.

[0119] Fabrication of the graphene layer: When the desired form of W was achieved, the synthesis of highly porous graphene was continued for 30 minutes while introducing 40 sccm of CH 4 , 40 sccm of H 2 and 300 sccm of Ar at 4 Torr (533 Pa). Then, the temperature was programmed to cool to room temperature under a mixture of 800 sccm of Ar and 40 sccm of H 2 .

[0120] Preliminary leaching process: After the CVD synthesis of highly porous graphene, a preliminary leaching process was carried out to remove the W nanostructures. The as-synthesized highly porous graphene was immersed in 0.1 M NaOH heated to 40 °C for 10 to 20 minutes depending on the initial thickness of the W thin film. Subsequently, the highly porous graphene / Cu-Ni alloy sample was immersed in DI water for 10 minutes, rinsed, and then dried by flushing with N 2 gas.

[0121] Application of the carrier substrate layer: After the preliminary leaching process, poly(methyl methacrylate) (PMMA, 950k, AR-P 672.03) was spin-coated onto the preliminarily leached highly porous graphene sample at 4000 rpm for 40 seconds. Subsequently, the PMMA / highly porous graphene sample was baked at 110 °C for 1 minute.

[0122] Removal of the graphene layer: To facilitate characterization, the Cu-Ni alloy catalyst substrate was dissolved and removed by floating the sample in 0.5 M ammonium persulfate ((NH 4 ) 2 S 2 O 8 , APS, 248614, Sigma Aldrich). The PMMA / highly porous graphene was rinsed with DI water for 60 minutes, and the sample was transferred onto a target substrate, e.g., a Si wafer with 280 nm thick SiO 2 to examine the highly porous graphene. Subsequently, the PMMA layer was removed with acetone.

[0123] Assembly of highly porous graphene on the porous nonwoven material: An assembly of highly porous graphene and a porous nonwoven material such as polyurethane (Finetex ENE, DT007) was carried out. After the preliminary leaching process, the nonwoven material was adhered onto the highly porous graphene by various methods regarding the thickness of the nonwoven material: (1) isopropanol (IPA)-mediated adhesion and (2) heat treatment.

[0124] An assembly of highly porous graphene and a thin porous nonwoven material (characteristic pore diameter of approximately 1.2 μm (hole in) and thickness of 9 μm) was achieved by an IPA-mediated method. The thin nonwoven material was directly laminated onto the pre-impregnated highly porous graphene. IPA was gently applied until the laminated nonwoven / highly porous graphene was completely wet. The laminated sample was then dried under ambient conditions. As the IPA evaporated, the interfacial contact between the nonwoven material and the highly porous graphene became stronger. After completion of the drying process, the laminated sample was fired at 120 °C for 10 minutes on a hot plate (IKA, C-Mag HS 7) to further improve the adhesiveness.

[0125] An assembly of highly porous graphene and a relatively thick porous nonwoven material (characteristic pore width greater than 10 μm and thickness greater than 100 μm) was achieved by heat treatment and melt bonding. The thick nonwoven material is not suitable for the IA method due to deformation of the nonwoven fabric. The pre-impregnated highly porous graphene was heated on a hot plate (IKA, C-Mag HS 7) at a high temperature (150 °C to 180 °C) for 1 minute. After the preheating process, the thick nonwoven material was placed on the preheated highly porous graphene. The heat treatment process was carried out at 7×7 cm 2 with a weight of 100 g for 10 minutes and brought into firm contact.

[0126] After the assembly of the highly porous graphene and the nonwoven material, the sample was immersed in 0.5 M ammonium persulfate ((NH 4 ) 2 S 2 O 8 4, APS, 248614, Sigma Aldrich) to dissolve and remove the Cu-Ni alloy. The laminated nonwoven / highly porous graphene was rinsed with a mixture of 5% to 10% ethanol and DI water for 60 minutes to minimize the surface tension of water. The laminated sample was then dried under ambient conditions.

[0127] Fabrication of membranes for measurement of gas flow rate and water intrusion pressure: The assembly of highly porous graphene and the non-woven fabric material was cut into small pieces of about 1 cm × 1 cm. A 2 cm × 2 cm frame for the assembled membrane was made of stainless steel, and a 2 mm hole was opened in the center of the frame. The assembled membrane was placed on a metal foil having a small hole with a diameter of 0.8 mm as mechanical support. Then, after attaching carbon tape with a hole in the center to both sides of the membrane, the entire membrane was sandwiched between the frames. Note that it is necessary to align all the holes in the axial direction.

[0128] Gas flow measurement: The nitrogen gas permeation flow rate was characterized using a custom setup. The above-mentioned membrane was installed in a custom fixture, and sealing was achieved using rubber O-rings on both sides of the membrane. Nitrogen was supplied to the supply side, and the pressure was controlled by a regulator (SMC, IR1000-F01) while measuring the upstream pressure rise with a digital manometer (OMEGA, HHP91). The downstream flow rate was measured in sccm by a mass flow meter (MKS, Germany). All measurements were performed at room temperature.

[0129] The assembly of highly porous graphene on the non-woven fabric material was fabricated according to the synthesis of the above-mentioned highly porous graphene and their assembly. A 150 nm Ni film was deposited on a commercially available Cu foil by a sputtering process, and then a two-layer Ni / Cu catalyst was annealed to transform it into a Cu-Ni alloy, and highly porous graphene was synthesized on the catalyst. The synthesis process of highly porous graphene having a porosity of approximately 24% and a thickness of 5 nm on a Cu-Ni alloy having a thin film of 4 nm W was carried out at 4 Torr (533 Pa) with 40 sccm of CH 4 40 sccm of H 2 and 300 sccm of Ar introduced at 800 °C for 30 minutes. In addition, for the purpose of investigating how the porosity of graphene affects the gas flow rate, the synthesis period was adjusted from 30 minutes to 60 minutes, resulting in a decrease in porosity. The assembly of highly porous graphene and the non-woven fabric material was carried out by an IPA-mediated method, and then the metal catalyst was etched away with 0.5 M APS and rinsed with a mixture of 5% ethanol and DI water after the drying process.

[0130] A membrane of a highly porous graphene / nonwoven material was attached to a stainless-steel frame. The frame with the membrane was placed and fixed in a custom fixture connected to a gas pipe equipped with a regulator and a mass flow meter. Note that the mass flow meter was limited to 20 sccm of N 2 It should be noted that it is limited to. The pressure of N 2 was slowly and gradually increased. For example, the pressure of N 2 was increased by 20 mbar (2000 Pa) at a time, and maintained for 1 minute until the mass flow meter indicated 20 sccm of N 2 to stabilize the pressure.

[0131] Figure 25a shows the gas flow rate of the highly porous graphene membrane as a function of growth time. The porous nonwoven material itself showed 4351 sccm / cm 2 However, for the highly porous graphene membrane grown for 30 minutes, the gas flow rate decreased by 18%, corresponding to 3605 sccm / cm 2 As the duration of the synthesis process extends, the gas flow rate decreases to 3160 sccm / cm 2 and 971 sccm / cm 2 respectively for growth times of 45 minutes and 60 minutes. In addition, Figure 25b shows the gas flow rate of the highly porous graphene membrane before and after the water intrusion pressure shown later. Highly porous graphene grown for 45 minutes was used. Due to partial blockage of the pores during drying after the liquid measurement, the gas flow rate decreased slightly to 11%, corresponding to 2814 sccm / cm 2 .

[0132] Water intrusion pressure measurement (ISO 811, hydrostatic head test): The water intrusion pressure was characterized using distilled water with a custom setup. The entire above-mentioned membrane was inserted into the fixture and firmly fixed, and sealing was achieved by rubber O-rings on both sides of the membrane. The tube was filled with DI water using a syringe. The upstream side of the tube was connected to an N 2 gas pipe, and the downstream side of the tube was connected to the fixture. N 2The pressure of the gas was controlled by a regulator (SMC, IR1000-F01) and monitored by a digital manometer (OMEGA, HHP8200). As the pressure increased, the pressure of the DI water from the supply side rose, generating a liquid contact pressure against the corresponding membrane surface. The pressure was gradually increased by the regulator and maintained at the target pressure for 30 minutes to examine the long-term stability. The pressure was increased until water droplets were observed from the back side. The pressure corresponding to water breakthrough was defined as the water intrusion pressure.

[0133] The assembly of highly porous graphene on the nonwoven fabric material was carried out in the same manner as described above for gas flow measurement. The frame with the membrane was installed and fixed in a custom fixture connected to a water pipe. The opposite side of the water pipe was connected to an N 2 gas pipe equipped with a regulator. 2 The pressure of N was slowly and gradually increased. For example, the pressure of N was increased by 50 mbar (5000 Pa) at a time until water droplets were observed behind the membrane, and maintained for 1 minute to stabilize the pressure. 2

[0134] Figures 26a to 26c show representative SEM images of the highly porous graphene membrane before water intrusion pressure measurement. A 150-nm Ni film was coated on a Cu foil by a sputtering process, and a two-layer Ni / Cu catalyst was subsequently annealed at 1000 °C to convert it into a Cu-Ni alloy, and highly porous graphene was obtained on the binary metal alloy. After the deposition of a thin W film (4 nm) on the Cu-Ni alloy, the synthesis process of highly porous graphene in which the thin W film is converted to W NS during heating was carried out at 800 °C for 30 minutes under 4 Torr (533 Pa) using 40 sccm of CH 4 40 sccm of H 2 and 300 sccm of Ar, obtaining a porosity of approximately 24% and a thickness of 5 nm. In the high-magnification SEM image of Figure 26a, the highly porous graphene was transferred to the nonwoven fabric material and mechanically supported. In addition, the porous structure of the highly porous graphene was not affected during the transfer and drying in Figures 26b and 26c. The water intrusion pressure measurement was carried out after the SEM investigation. N 2The pressure was gradually increased by 50 mbar (5000 Pa) at a time and maintained for 1 minute repeatedly. When the pressure reached 3 bar (3×10 5 Pa), which is equivalent to a water column of 30 m, the increase in pressure was stopped and maintained for 30 minutes to examine the long-term stability. After 30 minutes, the pressure was decreased and the membrane frame was dried under ambient conditions for SEM inspection. Figures 26d to 26f show typical SEM images of the membrane after water intrusion pressure measurement. Notably, Figure 26d shows that the highly porous graphene on the nonwoven material was not damaged at all. It was suggested that the highly porous graphene could withstand a pressure exceeding 3 bar (3×10 5 Pa) for 30 minutes, indicating high resilience and long-term stability against water intrusion pressure. Although the highly porous graphene withstood the pressure of 3 bar (3×10 5 Pa) well, Figures 26e and 26f show that the porous structure of graphene was partially blocked due to the blocking effect of contaminants during the test.

[0135] Effect of Ni concentration on the areal porosity and thickness of highly porous graphene: Cu is the most widely used catalyst for the synthesis of high-quality single-layer graphene. However, due to its low catalytic effect, the growth period is long and the thickness is limited (i.e., single layer). To accelerate the growth process and control the thickness of graphene, other metals with high catalytic effects can be added to Cu in the form of an alloy. Among other transition metals, Ni can form a binary metal alloy (i.e., Cu-Ni alloy), enabling the promotion of the growth reaction. Furthermore, by modifying the Cu-Ni alloy, i.e., changing the Ni concentration, the graphene growth mechanism can be adjusted from a surface-mediated to a precipitation behavior. For example, in a Cu-Ni alloy with a low Ni concentration, i.e., low C solubility, graphene growth occurs on the surface of the catalyst by a surface-mediated mechanism. In contrast, at high Ni concentrations, C tends to be absorbed into the bulk of the Cu-Ni alloy, and during the cooling process, C diffuses from the bulk, promoting the completion of multilayer graphene growth (precipitation behavior). Therefore, it is important to evaluate how the Ni concentration affects the structural properties (e.g., thickness and areal porosity) of highly porous graphene and find the optimal Ni concentration for the desired properties.

[0136] To analyze the dependence of the Ni concentration of the Cu-Ni alloy on the thickness and areal porosity of highly porous graphene, Ni films of various thicknesses were applied onto Cu catalysts. Using physical vapor deposition as described above, Ni films with thicknesses of 10 nm, 25 nm, 50 nm, 100 nm, 150 nm, 300 nm, 1 μm, and 2.2 μm were deposited onto Cu catalysts.

[0137] The prepared catalysts were subjected to an annealing process to form a Cu-Ni alloy. The annealing process was carried out at 1000 °C for 1 hour under 50 sccm of H 2 The Ni concentration obtained from each Ni thickness ranged from 0.04% to 9% after annealing.

[0138] After preparing Cu-Ni alloys with different Ni concentrations, a 6-nm-thick W thin film was coated onto the alloy using physical vapor deposition. Then, following the method described above, 40 sccm of CH 4 、40 sccm of H 2Using Ar at 300 sccm, high-porosity graphene was grown at 750 °C for 30 minutes under 4 Torr (533 Pa) in a short time.

[0139] After the synthesis of high-porosity graphene, the high-porosity graphene was transferred onto a substrate such as SiO 2 or SiN x and its thickness and areal porosity were measured.

[0140] As a protective layer, PMMA (950k, AR-P 672.03) was spin-coated onto the as-grown high-porosity graphene at 4000 rpm for 40 seconds. Then, the Cu-Ni alloy was removed by etching with a chemical solution (ammonium persulfate, 0.5 M) for 3 hours. Next, the high-porosity graphene with PMMA was rinsed with deionized water for 30 minutes and transferred onto a substrate. The PMMA film was removed by acetone for 30 minutes or by thermal annealing at 400 °C for 2 hours.

[0141] SiO 2 The thickness of each high-porosity graphene transferred onto SiO was measured by atomic force microscopy (AFM). Figure 27 shows a plot of the thickness of high-porosity graphene as a function of the Ni content in the substrate.

[0142] At a Ni concentration of 0.04%, the thickness of the high-porosity graphene was found to be on average 2.8 nm, corresponding to 8 or 9 layers. A dramatic increase in the thickness of the graphene film was observed from a Ni concentration of about 0.08%, reaching an average of 6.93 nm. This increased gradually up to a Ni concentration of 0.4%, at which the thickest high-porosity graphene film with an average of 10.8 nm was obtained, corresponding to 32 or 33 layers. From a Ni concentration of 0.7%, the thickness of the high-porosity graphene decreased counterintuitively to an average of 5 nm, estimated to be 15 layers. Even thinner graphene with an average of 4 nm for about 12 graphene layers was obtained at a Ni concentration of 1.4% in the Cu-Ni alloy. Using even higher Ni concentrations such as 4% and 9%, single layers of graphene with a thickness of 0.34 nm appeared.

[0143] The results based on the dependence on Ni concentration are contrary to previous reports which have reported that the highest possible Ni concentration on the Cu-Ni alloy facilitates the synthesis of multilayer graphene. In the case of the present inventors, with the increase in Ni concentration, the highly porous graphene becomes thinner from 1% and becomes monolayer from a Ni content of about 5%.

[0144] By using the same thickness of W thin film, the same effect of the W nanostructure on the C flux at the surface is suggested, and it can be expected that the C flux can also be manipulated by the Ni concentration.

[0145] In other words, the Cu-Ni alloy having a high C solubility due to a high Ni concentration tends to absorb more active C species, and thus the C concentration on the surface can be reduced. The shortage of the C flux cannot achieve a supersaturated state, and preferably, instead of the formation of additional graphene layers, the attachment of C to the ends of the pores occurs. As a result, the thickness of the graphene does not increase further.

[0146] In addition to the manipulation of the C flux at the surface, the Ni concentration also has a great influence on the evolution of the W nanostructure. From the characteristics of W such as a high melting temperature and no solid solubility in Cu-Ni, by heating, the W thin film was successfully converted into a W nanostructure having nanowalls and lens-shaped nanoparticles connected at a low Ni concentration of 0.04% to 1.4%. However, at Ni concentrations of 4% and 9%, subsequently, instead of the connected nanowalls, lens-shaped nanoparticles of W appeared on the surface. Since the solid dewetting of the W thin film is affected by the surface energy of the alloy, different Ni concentrations of the alloy result in different surface energies, and the morphology of the W nanostructure can change. As a result, due to a large difference in the morphology of the W nanostructure, the Ni concentration may affect the areal porosity of the highly porous graphene.

[0147] The areal porosity is generally calculated in detail as follows in this specification. First, five representative SEM images of the highly porous graphene transferred onto the substrate were collected, and the pore regions were extracted using the ImageJ program. Typically, the pore regions of the above measurements have an area of 4.6 μm 2 in area.

[0148] Based on the results of the extracted pore areas, the areal porosity of the highly porous graphene represents the proportion of pores (voids) in the highly porous graphene.

[0149] At a Ni concentration of 0.04%, W nanostructures appear, but the areal porosity is 5.6%. In the Cu-Ni alloy with such a low Ni concentration, only a limited amount of active C species are generated, which may cause adhesion to the pore ends and a low areal porosity.

[0150] When the Ni concentration was increased from 0.1% to 1.4%, active C species were effectively supplied and could reach a supersaturated state. As a result, instead of the C atoms on the surface adhering to the ends of the pores, they can initiate the growth of additional graphene layers under the bottom graphene layer. Since a Ni concentration of 0.1% resulted in a dense W nanostructure, the areal porosity was approximately 45.2%, which is the highest value. At Ni concentrations of 0.2% and 0.4%, due to the morphology of the W nanostructures, the areal porosity decreased slightly to 36.7% and 38.4% respectively.

[0151] At Ni concentrations of 0.7% and 1.4%, the areal porosities were found to be 23.3% and 20.3% respectively. It was found that W nanoparticles appeared at Ni concentrations of 4% and 9%, and the areal porosity decreased significantly to 0.7% and 0.4% respectively.

[0152] In summary, a plot of the thickness and areal porosity of the highly porous graphene as a function of the Ni concentration, including that of the porous graphene grown on bare Cu according to the prior art patent document 13 (D1), is shown in FIG. 27.

[0153] It is concluded that Ni has a great influence on the growth behavior of graphene and the morphology of W nanostructures.

[0154] W nanoparticles appeared by the Cu encapsulation method, and porous single-layer graphene was obtained. Due to the low catalytic activity of Cu, sufficient concentration of C did not occur on the surface, and the thickness of graphene was limited to a single layer.

[0155] A small amount of Ni in an appropriate ratio, as in the claims, converts the W thin film into W nanostructures and helps to rapidly decompose CH 4 into active C species. Furthermore, the low Ni concentration limits the diffusion of C into the bulk of the Cu-Ni alloy, maintaining a high C flux on the surface and synthesizing thick graphene with a high areal porosity.

[0156] In contrast, single-layer graphene with an areal porosity of less than 1% grown on a Cu-Ni alloy with a high Ni concentration occurred as a result of the transformation of the W thin film into lens-shaped W nanoparticles and the bulk diffusion of active C species into the Cu-Ni alloy.

[0157] In the present invention, a Ni concentration of 0.1% to 0.4% enables the achievement of the thickest film of graphene and the highest areal porosity, suggesting that such a Ni concentration not only promotes the growth of additional graphene layers but also advances the W nanostructures and can increase both the thickness and the areal porosity.

Description of Reference Numerals

[0158] 1 Catalytic substrate, copper / nickel substrate 2 Catalytically inactive domain 3 Substrate surface 4 Process of growing graphene layer on substrate 5 Porous graphene layer 6 Pores in 5 7 Copper foil 8 Ni film 9 Natural oxide layer 10 Adhesive material 11 Tungsten deposition 12 Consecutive tungsten film layers 13 Any housing 14 Any process of applying a (copper) housing 15 Process of thermal annealing 16 Removal of any (copper) housing 17 PMMA coating process 18 PMMA coating layer 19 Removal of the substrate 20 Transfer to a carrier substrate 21 Carrier substrate 22 Cross-sectional view 23 Top view 24 Mechanical force 25 Support material 26 Electrode 27 Electrolyte 28 W nanoparticles 29 W nanowalls 30 Polyurethane

Claims

1. A method of fabricating a porous graphene layer (5) having a thickness of less than 100 nm and having pores (6) with an average characteristic width defined in this specification in the range of 1 nm to 1000 nm, comprising: preparing a catalytically active substrate (1) that catalyzes graphene formation under chemical vapor deposition conditions, on which a plurality of catalytically inactive domains (2) having nanostructures substantially corresponding to the shape of the pores (6) of the resulting porous graphene layer (5) are provided on the surface (3); performing chemical vapor deposition using a carbon source in the gas phase to form the porous graphene layer (5) on the surface (3) of the catalytically active substrate (1), wherein the pores (6) of the porous graphene layer (5) are formed in-situ due to the presence of the catalytically inactive domains (2); wherein the catalytically active substrate (1) is a copper-nickel alloy substrate having a copper content in the range of 98 wt% to less than 99.96 wt% and a nickel content in the range of more than 0.04 wt% to 2 wt%, and the copper content and the nickel content complement each other to be 100 wt% of the catalytically active substrate (1).

2. the catalytically active substrate (1) has a nickel content in the range of 0.06 wt% to 1 wt% or 0.08 wt% to 0.8 wt%, which is complemented to be 100 wt% by the copper content, and / or the catalytically active substrate (1) is fabricated by applying a nickel film in the range of 10 nm to 2.2 μm in thickness, or 25 nm to 300 nm in thickness, or 20 nm to 500 nm in thickness, or 50 nm to 300 nm in thickness on a pure copper foil and annealing, wherein the annealing temperature may be in the range of 800 °C to 1200 °C, or in the range of 900 °C to 1100 °C. and / or, the catalytically active substrate (1) is formed by applying a nickel film with a thickness in the range of 10 nm to 2.2 μm, or in the range of 25 nm to 300 nm, or in the range of 20 nm to 500 nm, or in the range of 50 nm to 300 nm, using electrochemical plating, electron beam evaporation, PVD or sputtering, onto a pure copper foil with a thickness in the range of 0.01 mm to 0.10 mm, or in the range of 0.02 mm to 0.04 mm, and annealing at a temperature in the range of 800 °C to 1200 °C, or in the range of 900 °C to 1100 °C, for a time in the range of 10 minutes to 120 minutes, or in the range of 30 minutes to 90 minutes. At this time, the pure copper foil may be a pure copper foil with a purity exceeding 99.5%, according to the method of claim 1.

3. The method according to claim 1 or 2, wherein the porous graphene layer (5) has a thickness in the range of less than 50 nm, or in the range of 1 nm to 20 nm, or in the range of 5 nm to 15 nm, or in the range of 7 nm to 12 nm.

4. The method according to any one of claims 1 to 3, wherein the porous graphene layer (5) has an areal porosity in the range of at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40%.

5. Apply an essentially continuous tungsten layer, and then anneal at a pressure less than atmospheric pressure to convert the tungsten film into a plurality of the catalytically inactive domains (2), whereby a plurality of the catalytically inactive domains (2) are provided on the surface (3) of the catalytically active substrate (1). The annealing can be carried out at a temperature in the range of 700 °C to 1100 °C, or in the range of 750 °C to 950 °C, or in the range of 800 °C to 900 °C. The annealing can be carried out for a time in the range of 10 minutes to 180 minutes, or in the range of 50 minutes to 100 minutes. The application of the tungsten layer can be carried out using sputtering, electron beam evaporation, or PVD. The essentially continuous tungsten layer may have a thickness in the range of more than 1 nm, or more than 3 nm, or more than 5 nm, or in the range of 1 nm to 10 nm, or in the range of 5 nm to 10 nm. The annealing may be performed under a pressure of less than 100 mTorr (13.3 Pa), and / or in a reducing atmosphere, and / or in the presence of an inert gas, and the inert gas may be argon gas or nitrogen gas combined with hydrogen gas, the method according to any one of claims 1 to 4.

6. The catalyst-inactive domain (2) has an average characteristic width in the range of 1 nm to 1000 nm, or in the range of 10 nm to 100 nm, or in the range of 10 nm to 50 nm, or has an average characteristic width in the range of 5 nm to 900 nm, or in the range of 10 nm to 200 nm, or in the range of 10 nm to 100 nm, the method according to any one of claims 1 to 5.

7. Using methane gas as a carbon source, performing chemical vapor deposition using a carbon source in the gas phase, and forming the porous graphene layer (5) on the surface (3) of the catalyst-active substrate (1), whereby the pores (6) of the porous graphene layer (5) are formed in situ due to the presence of the catalyst-inactive domain (2), The chemical vapor deposition may be performed under reduced pressure in the coexistence of argon gas and hydrogen gas, and the reduced pressure may be less than 50 Torr (6670 Pa), or less than 5 Torr (667 Pa), and the chemical vapor deposition may be performed over a time in the range of 10 minutes to 120 minutes, or less than 60 minutes, or less than 50 minutes, or less than 35 minutes. This graphene layer deposition process can be performed over a time that enables the production of a graphene layer with an average thickness in the range of more than 5 nm, or in the range of 8 nm to 12 nm, the method according to any one of claims 1 to 6.

8. The porous graphene layer (5) is removed from the catalyst-active substrate (1) and applied to a porous support substrate. The porous support substrate may be a non-woven or woven support substrate. For the removal of the porous graphene layer (5), first, a carrier layer (10, 25) is applied to the surface of the porous graphene layer (5) opposite to the catalyst-active substrate (1), and the sandwich of the carrier layer (10, 25) may be removed from the catalyst-active substrate (1), the method according to any one of claims 1 to 7.

9. Before the removal of the porous graphene layer (5), subject the layered structure of the catalytically active substrate (1) having the catalytically inert domain (2) and the porous graphene layer (5) to a preliminary leaching process that weakens or removes the bond between the porous graphene layer (5) and the catalytically active substrate (1) and / or the catalytically inert domain (2). The preliminary leaching process may include forming an oxide layer (10) at least partially or essentially completely between the porous graphene layer (5) and the catalytically active substrate (1) and removing the catalytically inert domain (2). And / or, before the removal of the porous graphene layer (5), subject the layered structure of the catalytically active substrate (1) having the catalytically inert domain (2) and the porous graphene layer (5) to a preliminary leaching process that weakens or removes the bond between the porous graphene layer (5) and the catalytically active substrate (1). And / or, subject the preliminary leaching process to a basic or acidic environment. The preliminary leaching process may be in water and may have a pH less than 6, or greater than 7, or greater than 10, or greater than 12. An aqueous 0.01 M to 0.5 M NaOH solution can be used. The preliminary leaching process may be carried out at a temperature in the range of 40°C to 60°C for a time in the range of 10 minutes to 60 minutes, followed by rinsing with water and drying. The method according to any one of claims 1 to 8.

10. Using an electrochemical method, immerse the layered structure of the catalytically active substrate (1) having the catalytically inert domain (2) and the porous graphene layer (5) in an electrolyte, and apply an electrochemical potential to the catalytically active substrate (1) with respect to a counter electrode in the same electrolyte to remove the porous graphene layer (5). The removal of the porous graphene layer (5) may be after the preliminary leaching process. The method according to any one of claims 1 to 9.

11. Attach the porous graphene layer (5) to a porous support substrate after or for the purpose of removal from the catalytically active substrate (1). The porous support substrate may be a non-woven or woven support substrate. The porous support substrate may have characteristic filament diameters in the range of 200 nm to 2000 nm, or in the range of 300 nm to 1000 nm, and may have characteristic filament diameters with a standard deviation of less than 500 nm, and / or the porous support substrate may have characteristic pore diameters in the range of 500 nm to 50000 nm, or in the range of 1000 nm to 10000 nm, and may have characteristic pore diameters with a standard deviation of less than 1000 nm. The non-woven or woven support substrate can be attached to the porous graphene layer (5) using solvent-induced adhesion and / or thermal adhesion. The adhesion to the non-woven fabric may be achieved using isopropanol-mediated adhesion and annealing and / or heat treatment, the method according to any one of claims 1 to 10. **Claim 12** A graphene layer (5), The graphene layer (5) has a thickness of less than 50 nm and is provided with pores (6) having an average characteristic width defined herein in the range of 1 to 1000 nm. The graphene layer (5) has an areal porosity in the range of at least 10%. The graphene layer (5) may be on at least one support substrate. **Claim 13** Having a thickness in the range of 1 nm to 20 nm, or in the range of 5 nm to 15 nm, or in the range of 7 nm to 12 nm, and / or having an areal porosity in the range of at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40%, the graphene layer (5) according to claim 12. **Claim 14** A textile piece or clothing item having at least one graphene layer (5) according to claim 12 or 13, wherein the textile piece or clothing item may be a textile piece or clothing item in the form of a water-resistant and / or water-repellent and / or breathable clothing item. **Claim 15** Use of the graphene layer (5) according to claim 12 or 13 as a semi-permeable membrane, wherein the semi-permeable membrane may be a semi-permeable membrane for textile applications in the field of clothing items, or a semi-permeable membrane in the technical field for providing a waterproof barrier in electronic devices and / or portable devices.

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