Methods of making and / or delaminating porous graphene membranes and membranes made using the methods

Abstract

A method for producing a porous graphene layer (5) comprising the steps of: providing a catalytically active substrate (1) for catalysing graphene formation under chemical vapour deposition conditions, said catalytically active substrate (1) being provided with a plurality of catalytically inactive domains (2) on its surface (3); performing chemical vapour deposition on the surface (3) of the catalytically active substrate (1), in-situ forming pores (6) in the porous graphene layer (5) due to the presence of the catalytically inactive domains (2); wherein after chemical vapour deposition the porous graphene layer (5) is detached from the substrate (3) in such a way that the exposed porous graphene layer (5) is subjected to an aqueous solution containing dissolved oxidizing agent, directly or indirectly followed by treatment of the exposed porous graphene layer (5) with an aqueous solution of a persulfate salt, directly or indirectly followed by lamination of a carrier layer to the exposed porous graphene layer (5) from the side opposite to the catalytically active substrate (1), and mechanical separation of said carrier layer (16) with the exposed porous graphene layer (5) from said catalytically active substrate (1).

Description

Technical Field

[0001] This invention relates to a method for preparing porous graphene films that are waterproof and highly permeable due to enhanced vapor permeability through the pores penetrating the graphene layers, with particular concern regarding delamination from a catalytic substrate. Furthermore, this invention relates to graphene films prepared using this method and their uses, as well as catalytic substrates for preparing such films and their applications. Background Technology

[0002] Waterproof membranes used in outdoor clothing are effective against high hydrostatic pressure (rain penetration resistance). However, they typically have low vapor permeability, which does not allow sufficient water vapor transmission, breathability of the garment, and user comfort.

[0003] Highly permeable membranes are also relevant to a wide range of technical textile applications, including military uniforms for chemical protection, emergency responder uniforms, protective gloves, and outdoor electronic circuitry protection packaging. Membranes offering high effluent rates and / or selectivity also have broad potential applications in separation and energy applications. They will also inspire many other potential application areas that are currently unseen due to the lack of highly permeable membranes.

[0004] While GoreTex® dominates the waterproof membrane market, numerous alternative membrane suppliers exist, manufacturing membranes from a variety of polymers besides PTFE, such as polyamides and polyurethanes. In each case, the membrane consists of a polymer membrane with small pores to allow water vapor to pass through. The thickness of conventional membranes and limitations on pore density restrict the amount of vapor transport.

[0005] One proposed alternative material for applications requiring high vapor permeability and water-sealing properties is porous graphene. Graphene (a two-dimensional monolayer of sp2-hybridized carbon atoms) has attracted worldwide attention and research interest due to its outstanding physical properties, including high electronic conductivity, thermal stability, and mechanical strength. The use of porous graphene films in fabric laminates has been proposed in the following literature:

[0006] WO-A-2014084860 generally describes the fixation of porous graphene layers onto a fiber substrate backing. It describes laminated assemblies and methods for constructing and assembling such assemblies. It does not describe methods for forming the porous graphene layers.

[0007] US-A-2015273401 extends the method described in WO-A-2014084860 to assemblies of porous graphene films on fabric substrates, including selective film layers on the graphene layer side. The preparation of porous graphene film materials is outlined, involving the growth of continuous monolayers and the perforation of layers, as well as subsequent steps.

[0008] The aspects related to porous graphene and its various production methods can be summarized into the following categories and subcategories.

[0009] Category 1: Post-synthesis formation of porous graphene - continuous method

[0010] Post-synthesis formation involves perforating pores in the continuous graphene layers synthesized in the previous steps. The continuous method involves the pore-by-pore fabrication of porous graphene layers. This is a slow method offering minimal practicality for the large-scale production of porous membranes.

[0011] Category 1.1: Nitrogen-assisted electron beam perforation

[0012] Scanning electron microscopy (SEM) imaging in the presence of nitrogen can be used to induce localized reactive ion etching processes by ionizing nitrogen molecules with a focused electron beam from the SEM. This method can etch holes as small as 10 nm into multilayer graphene (less than 10 layers). However, the diffusion of nitrogen ions out of the area where the electron beam is focused causes holes to be etched outside the target area, raising questions about the ability to produce dense arrays of small holes. Furthermore, the use of SEM makes it a continuous hole milling process, which is difficult to scale up.

[0013] Category 1.2: FIB & Unfocused Electron Beam Patterning

[0014] In this two-step method, 3 keV Ar is first used. + Focused ion beam (FIB) techniques generate single-atom and diatomic defects in graphene monolayers, requiring the monolayer to be cooled to 148 K to obtain the desired defect size. Subsequently, an unfocused electron beam of 80 keV is used to grow defects from the hole edges while leaving the defect-free graphene portions unaffected, enabling the generation of holes with diameters as low as 0.6 nm.

[0015] Alternatively, you can use Ga + Ions or He + Focused ion beams are used to generate pores ranging in size from 1000 nm to sub-10 nm. This method allows for control over pore size, density, and arrangement; however, scaling up remains difficult due to the continuity of milling. Furthermore, milling sub-5 nm pores presents significant challenges.

[0016] WO-A-2015167145 discloses a graphene film and a method for preparing the same. The graphene film comprises a graphene layer with a porous pattern and a support. The porous pattern includes multiple pores with sizes ranging from 5 nm to 100 nm. The support is configured to support the graphene layer and includes multiple pores larger than the target pores in the graphene layer. The proposed method involves forming block copolymer domains on a graphene surface to form a mask template. The pores are then etched into the graphene layer using subsequent exposure to ion beam radiation.

[0017] Category 1.3: TEM-based methods

[0018] To measure DNA translocation through graphene nanopores, freestanding graphene can be perforated using a 300 kV accelerating voltage electron beam in a transmission electron microscope (TEM). Pores ranging from 2 nm to 40 nm can be patterned in both monolayer and multilayer graphene. No amorphization was observed around the pores, indicating that local crystallinity is maintained. However, this method is not parallel and is quite time-consuming.

[0019] Category 2: Post-synthesis formation of porous graphene - parallel method

[0020] Post-synthesis formation involves perforating the continuous graphene layers synthesized in previous steps. Parallel processing involves perforating the graphene layers simultaneously at multiple locations.

[0021] Category 2.1: UV-induced oxidation etching

[0022] UV etching was performed to generate sub-nm defects in the graphene, which grew under extended exposure. The etching was repeated 15 times, with each minute of exposure to the bilayer graphene film, to produce, for example, pores exhibiting size-selective sieving of SF6 with a kinetic diameter of 4.9 Å.

[0023] Category 2.2: Ion Bombardment & Oxidation Etching

[0024] Ga+ ions at 8 keV can be accelerated at an incident angle of 52° on the graphene surface, thereby creating defects in the graphene lattice. Subsequently, unsaturated carbon bonds can be etched using acidic potassium permanganate to etch the graphene defects and thus enlarge the pores until stabilization occurs at a pore size of 0.4 nm after 60 minutes of etching time, which is believed to be due to the formation of functional groups that inhibit further growth reactions.

[0025] Category 2.3: Oxygen Plasma

[0026] Sub-nm pores can be generated by exposing suspended monolayer graphene to oxygen plasma etching (20 W) for 1 to 6 seconds, where the etching time determines the pore size and pore density. A pore density of 1 pore / 100 nm can be achieved by exposing the graphene to plasma for 1.5 seconds. 2 The pore size ranges from 0.5 nm to 1 nm.

[0027] Category 2.4: Strain-Assisted Pt Nanoparticle Perforation

[0028] The self-assembly of block copolymer (BCP) micelles containing Pt precursors leads to the distribution of Pt nanoparticles through a substrate to which previously prepared graphene monolayers can be transferred, resulting in perforation after annealing at 400 °C. Catalytic perforation of the graphene is promoted by localized strain at the Pt nanoparticles. Pore size and density can be controlled by micelle composition, producing pores as low as 17 nm with a porosity of 12.8%. Large-scale perforation should theoretically be possible; however, obtaining a uniform dispersion of the Pt precursor is challenging, and the largest area shown is approximately 4 μm².

[0029] Category 2.5: Perforation using catalytic oxidation in contact with metal particles

[0030] KR-A-20120081935 and KR-A-101325575 propose applying a thin metal film (Au or Ag) deposited on the surface of an existing graphene layer, followed by an annealing step to form metal particle domains on the graphene surface. A further thermal step results in the formation of pores at the contact points with the metal domains via catalytic oxidation.

[0031] Category 2.6: Using anodized aluminum as a template

[0032] Anodized aluminum oxide films can be used to pattern graphene on a substrate. The anodized aluminum oxide is placed with small holes sideways to the existing continuous graphene substrate, and if the graphene is not protected by the aluminum oxide, plasma exposure is used to remove the graphene. The resulting hole sizes are 40 nm to 60 nm.

[0033] Category 3: Porous graphene films formed from graphene sheets

[0034] Porous membranes of graphite layers can alternatively be formed by assembling membranes composed of graphene (or graphene oxide) sheets. The sheets, in principle, form a layered structure, with pores formed between the sheet boundaries. The graphene sheet method tends to produce relatively thick layers that do not fully utilize the inherent two-dimensional planar (low-thickness) geometry of graphene.

[0035] Category 3.1: Pore templates during membrane formation

[0036] CN-A-104261403 describes a method for preparing graphene films with a three-dimensional porous structure. Polystyrene domains are used as sacrificial templates to form pores within a film layer formed from graphene oxide sheets as the starting material.

[0037] Category 4: Direct Synthesis of Porous Graphene Membranes

[0038] The direct synthesis of porous graphene films involves forming porous features directly within the graphene layer during its formation. This direct synthesis method avoids the need for post-synthesis processing to achieve the porous structure.

[0039] Category 4.1: Pores caused by grain boundary defects

[0040] EP-A-2511002 discloses the growth of a graphene layer on an untreated copper substrate. This monolayer is then coated with a PMMA solution and immersed in an etchant to remove the copper. The PMMA layer carrying the graphene layer is attached to a PTMSP film, and the PMMA layer is removed using a solvent. In the resulting graphene layer, multiple graphene grains exist, with pores serving as defects between the graphene grains. This patent describes membrane properties for separating various substances from liquids and gases.

[0041] Category 4.2: Template patterning of carbon source followed by graphene layer formation

[0042] CN-A-103241728 discloses a method for preparing graphene nanopore arrays, comprising the following steps: 1) coating a carbon source solution onto the surface of a porous anodic alumina (PAA) template; 2) pressing the carbon source-coated PAA template onto the surface of a metal substrate, peeling off the PAA template, ensuring that the carbon source remains on the surface of the metal substrate and retains a pattern consistent with the pattern on the surface of the PAA template; and 3) annealing the obtained metal substrate in the presence of a mixed gas flow of hydrogen and argon, thereby transforming the carbon source into a graphene nanopore array. The nanopore arrays obtained by this invention are interconnected nanopore array structures rather than single nanopores or a few nanopores; and the pore size of the nanopores can be adjusted by the template effect of the PAA itself, and can be further adjusted by subsequent growth and etching.

[0043] TW-A-201439359 describes a method for forming large-area graphene layers on porous substrates via chemical vapor deposition (CVD). In the first step, carbon material is deposited onto a porous template using CVD. In the second step, the carbon material is subjected to annealing and catalytic graphitization to convert the carbon into graphene layers. In the third step, liquid-phase exfoliation is used to reduce the amount of graphene layers on the substrate.

[0044] Category 4.3: Direct growth of porous graphene using porous templates and patterns

[0045] CN-A-102583337 describes a method for preparing graphene materials with a porous structure. A porous magnesium oxide / silicon composite material is used as a template substrate. Graphene is grown directly on the porous template using chemical vapor deposition (CVD). The graphene layer retains the porous structure of the template substrate. The porous graphene layer is recovered by destructively etching the magnesium oxide / silicon composite substrate.

[0046] US-A-2012241069 discloses how to fabricate graphene patterns by forming a pattern of passivation material on a growth substrate. The pattern of the passivation material defines a reverse pattern of the exposed surface on the growth substrate. A carbon-containing gas is supplied to the reverse pattern of the exposed surface of the growth substrate, and patterned graphene is formed from the carbon. The passivation material does not promote graphene growth, while the reverse pattern of the exposed surface of the growth substrate does promote graphene growth.

[0047] US-A-2013160701 proposes a method for growing microstructured and nanostructured graphene by directly growing microstructured and nanostructured graphene from the bottom up with desired patterns. Graphene structures can be grown via chemical vapor deposition (CVD) on a substrate partially covered by a patterned graphene growth barrier guided by graphene growth.

[0048] WO2017212039 discloses a method for preparing porous graphene layers with a thickness of less than 100 nm and pores having an average size in the range of 5 nm to 900 nm. The method includes the following steps: providing a catalytically active copper substrate for catalytic graphene formation under chemical vapor deposition conditions, wherein the catalytically active substrate has a plurality of non-catalytically active domains disposed in or on its surface, the size of the plurality of non-catalytically active domains substantially corresponding to the size of the pores in the resulting porous graphene layer; performing chemical vapor deposition using a gaseous carbon source and forming a porous graphene layer on the surface of the catalytically active substrate, thereby forming pores in the graphene layer in situ due to the presence of non-catalytically active domains.

[0049] In the field of graphene CVD growth, Dong et al. (The Growth of Graphene on Ni–Cu AlloyThin Films at a Low Temperature and Its Carbon Diffusion Mechanism, Nanomaterials (Basel). November 2019; 9(11): 1633) found that the solid solubility of carbon in metals is an important factor affecting the uniform growth of graphene by chemical vapor deposition (CVD) at high temperatures. However, at low temperatures, it was found that the carbon diffusion rate (CDR) on the surface of the metal catalyst has a greater impact on the number and uniformity of graphene layers than the solid solubility of carbon. The CDR decreases rapidly with decreasing temperature, resulting in heterogeneous and multilayered graphene. In this work, a Ni-Cu alloy sacrificial layer was used as a catalyst based on the following characteristics: Cu was chosen to improve the CDR, while Ni was used to provide high catalytic activity. Graphene was grown on the surface of the Ni-Cu alloy using methane as a carbon source at low pressure via plasma-enhanced CVD. The optimal Ni-Cu alloy composition of 1:2, i.e., 33% Ni, was selected experimentally. Furthermore, the plasma power was optimized to improve graphene quality. Based on parameter optimization, and combined with our previously reported in-situ sacrificial metal layer etching technique, relatively homogeneous wafer-sized patterned graphene was obtained directly on a 2-inch SiO2 / Si substrate at a low temperature (approximately 600°C).

[0050] Losurdo et al. (Graphene CVD growth on copper and nickel: role of hydrogen in kinetics and structure, Phys. Chem. Chem. Phys., 2011, 13, 20836-20843) reported that understanding the chemical vapor deposition (CVD) kinetics of graphene growth is important for advancing graphene processing and achieving better control over graphene thickness and properties. From the perspective of improving the quality of large-area graphene, they investigated the CVD kinetics of CH4-H2 precursors on both polycrystalline copper and nickel-only substrates in real time. They highlighted the role of hydrogen in differentiating the growth kinetics and thickness of graphene on copper and nickel. Specifically, the growth kinetics and mechanisms were modeled as a competition between the dissociative chemisorption of H2 and the dehydrogenation chemisorption of CH4, and a competition between the internal diffusion of carbon and hydrogen, where hydrogen diffuses faster in copper than in nickel, while carbon diffuses faster in nickel than in copper. This indicates that hydrogen acts as an inhibitor of CH4 dehydrogenation on copper, helping to suppress deposition on copper substrates and reduce graphene quality. Furthermore, evidence is provided of the role of hydrogen in the formation of out-of-plane CH defects in CVD graphene on Cu. Conversely, in the case of Ni, surface remodeling and reorganization by hydrogen contributes to CH4 decomposition. A better understanding of graphene growth kinetics and the provision of other factors for it helps to define the optimal CH4 / H2 ratio, which can ultimately contribute to improving the uniformity of graphene layer thickness, even on polycrystalline substrates.

[0051] Samir Al-Hilfi (Chemical vapor deposition of graphene on Cu-Ni alloy, paper, University of Manchester, 2018) explored the effect of carbon solubility in catalytic substrates on the CVD growth of graphene. Cu-Ni alloys exhibit complete solid solubility across their entire composition range and can be used to explore the effect of carbon solubility on graphene growth. Graphene was grown on Cu-Ni alloys with compositions of Cu, Cu70-Ni30, Cu55-Ni45, Cu33-Ni67, and Ni in a hot-wall CVD reactor. Thus, in all cases, the substrates were either Ni-free or contained at least 30% Ni. First, growth was achieved on pure metals (Cu and Ni) using CH4 as the carbon source, and the resulting films were characterized by Raman spectroscopy and scanning electron microscopy (SEM). The carbon distribution within the substrate bulk was measured by glow discharge optical emissions tereoscopy (GDOES). The latter revealed the difference in bulk carbon content between Cu and Ni, reflecting the effect on the graphite film on the surface. As the Ni content increases, the CVD growth of graphene on Cu-Ni alloys exhibits a transition from bilayer graphene (BLG) to few-layer graphene (FLG) surface coverage, accompanied by increased C diffusion in the bulk and incubation time. Cooling rate shows a significant effect on graphene surface coverage; however, this effect varies with Ni content. Fluid flow simulations indicate very low gas velocities beneath the substrate, resulting in poor mass transfer to the bottom substrate surface. Gas-phase kinetic simulations reveal the effect of gas residence time on the concentration of active material; furthermore, the concentration increases with the flow of gas. Finally, the surface reaction model using a CH4 / H2 mixture shows excellent agreement with experimental observations at low growth pressures; however, it is inconsistent at high growth pressures.

[0052] WO2021121952 discloses a method for preparing a porous graphene layer with a thickness of less than 100 nm, comprising the following steps: providing a catalytically active substrate having a plurality of non-catalytically active domains disposed on its surface, the size of the non-catalytically active domains substantially corresponding to the pore size in the resulting porous graphene layer; performing chemical vapor deposition to form a porous graphene layer on the surface of the catalytically active substrate; wherein the catalytically active substrate is a copper-nickel alloy substrate with a copper content in the range of 98 wt% to less than 99.96 wt% and a nickel content in the range of greater than 0.04 wt% to 2 wt%, the copper content and nickel content being complementary to 100 wt% of the catalytically active substrate.

[0053] According to US4784687, the scarcity of high-grade tungsten ore forces users to seek ways to recover tungsten from waste, but drill bits present particular challenges. Existing methods using acidic hydrogen peroxide to oxidize and dissolve tungsten are extremely inefficient in terms of reagent consumption per unit of recovered tungsten. According to this invention, hydrogen peroxide can be used significantly more efficiently to extract tungsten into acidic aqueous solutions by employing certain accelerators in the form of molten blocks that are solid at 50 degrees Celsius. These blocks slowly release the accelerator into the reaction solution and achieve similar efficiency in the use of hydrogen peroxide and acid compared to the same accelerator added in powder or granular form, but with significantly reduced accelerator consumption. Examples of such accelerators are hydroxyl- or amino-substituted aromatic carboxylic acids, such as 2-hydroxybenzoic acid. These accelerators are most conveniently suited for multi-stage tungsten extraction processes.

[0054] In summary, existing technologies for waterproof and breathable membranes can be improved, and there is room for improvement for consumer comfort and protection of materials beneath clothing or packaging. Breakthrough technologies are needed to achieve vapor permeability (rapid gas phase transport) while maintaining liquid barrier properties. Porous graphene membranes have been proposed for such applications and have been analyzed and compared with conventional breathable membranes, showing better breathability. However, existing methods for preparing suitable porous graphene membranes are not always adequate for scaling up and industrial processes. Summary of the Invention

[0055] A key aspect associated with these methods for manufacturing porous graphene layers is how to separate the porous graphene layer from the catalytic substrate on which the graphene layer is grown.

[0056] The most advanced graphene delamination methods currently available include etching, electrochemical delamination, and mechanical delamination.

[0057] Etching involves removing the catalytic substrate through complete dissolution. Etching is a mature method, but it is time-consuming, costly, complex, and generates a large amount of chemical waste, the recycling of which requires energy and costs.

[0058] Electrochemical delamination is non-destructive and allows for the reuse of the catalytic substrate. However, it also requires electrolytes and electricity, and in particular, the bubbles generated to effectively separate graphene from the catalytic substrate can introduce defects in the porous graphene layer and degrade its properties, and the process is slow if bubbles are to be avoided as much as possible. Therefore, this method is not suitable for highly porous graphene.

[0059] Mechanical delamination is non-destructive and allows for substrate reuse, and in principle, allows for short delamination times. On the other hand, achieving mechanical delamination requires pretreatment for oxidation of the catalytic substrate layer, thus consuming the substrate layer. Furthermore, the strong adhesion between graphene and the catalytic layer makes controlling this mechanical delamination difficult, and therefore this method is not suitable for highly porous graphene.

[0060] The aforementioned document WO-A-2021 / 121952 discloses a delamination method involving a pre-leaching process with a sodium hydroxide solution at elevated temperatures, followed by coating with PMMA as a temporary support substrate and baking at elevated temperatures, followed by electrochemical or mechanical delamination. A method for characterization is also disclosed, wherein after pre-leaching and PMMA coating, the catalyst substrate is completely dissolved by floating in an ammonium persulfate solution, transferred to a silicon wafer, and subsequently removed with acetone. However, this method only allows for characterization and not subsequent transfer to porous woven or nonwoven support materials for end-use. In any case, the problem with sodium hydroxide pre-leaching is that it cannot completely remove tungsten (or other non-catalytic) nanoparticles from the catalytic substrate. This document discloses immersing graphene grown on a substrate in a NaOH solution. NaOH is known to be a reducing agent and, under the conditions given in this document, will reduce WO3 without catalytically active domains to Na2WO4.

[0061] According to a first aspect of the present invention, the present invention relates to a method for preparing a porous graphene layer with a thickness of less than 100 nm, the porous graphene layer having pores with an average characteristic width in the range of 1 nm to 1000 nm as defined in the specification, the method comprising the following steps:

[0062] A catalytically active substrate is provided for catalytically forming graphene under chemical vapor deposition conditions, the catalytically active substrate having a plurality of non-catalytically active domains disposed on its surface, the plurality of non-catalytically active domains having a nanostructure substantially corresponding to the shape of the pores in the obtained porous graphene layer.

[0063] Chemical vapor deposition is performed using a gaseous carbon source to form a porous graphene layer on the surface of a catalytically active substrate. Due to the presence of non-catalytically active domains, pores are formed in situ within the porous graphene layer.

[0064] Thus, this method is based on the procedures disclosed in the aforementioned documents WO-A-2017 / 212039 and WO-A-2021 / 121952, the contents of which regarding the above steps are expressly incorporated into this disclosure.

[0065] The proposed method includes the following elements:

[0066] 1. Preparation of a catalytic substrate (preferably a specific copper / nickel alloy);

[0067] 2. Prepare the topological structure of a catalytically inactive material in the form of a catalytically inactive nanostructure on top of such a catalytic substrate;

[0068] 3. A porous graphene layer was synthesized on a (copper / nickel alloy) catalytic substrate with such a non-catalytically active nanomaterial topology, and then...

[0069] 4. Pre-leaching and conditioning of the interface between the porous graphene layer and the catalytic substrate, and

[0070] 5. Mechanically separate the porous graphene layer from the catalytic substrate; optionally:

[0071] 6. Apply such a porous graphene layer to nonwovens or porous fabrics.

[0072] These individual steps can be performed as follows:

[0073] 1. Preparation of Cu-Ni alloys:

[0074] Provide, for example, Cu catalysts (copper foil, 0.025 mm, 99.8%, product number 49686) purchased from Alfa Aesar; deposit Ni films (e.g., FHR, Pentaco 100, Ni purity 99.95%, 3 × 10⁻⁶) with thicknesses of 10 nm to 2.2 µm or 50 nm to 300 nm on the original commercial Cu catalyst in vacuum by electron beam evaporation or sputtering. -3 The sputtering pressure was approximately 0.006 mbar, accompanied by 200 sccm of Ar; the resulting Ni film was deposited using DC plasma with a power of 0.25 kW for 10 nm to 2.2 µm or 50 nm to 300 nm; the bilayer structure of the Ni / Cu catalyst was annealed at, for example, 1000 °C for, for example, 1 hour in a chemical vapor deposition (CVD) system (e.g., Graphene Square. Inc., TCVD-RF100CA) at a low pressure (e.g., 200 mTorr) with, for example, 50 sccm of H2 to convert it into a binary metal alloy (Cu-Ni alloy).

[0075] The Ni concentration, by weight, is greater than 0.04% to 10%, or preferably greater than 0.04% to 2%, or also in the range of 0.1% to 10%, preferably in the range of 0.2% to 8% or 0.3% to 5%, typically in the range of 0.4% to 3%. Particularly preferably, the nickel content of the catalytically active substrate is in the range of 0.06 wt% to 1 wt% or 0.08 wt% to 0.8 wt%, which is made up to 100 wt% by copper content. The balance is Cu (therefore, for the widest range, it is 99.96% to 90%, and for a typical range, it is 99.94%, less than 99%, or 99.6% to 97%, the balance excluding very small amounts of impurities that may be present in the initial Cu foil or initial Ni and which total less than 0.05 wt% or less than 0.02 wt% in the final substrate). The range of Ni content depends on the initial Ni thickness. The typical working Ni content is preferably in the range of 0.5% to 2%.

[0076] 2. Transformation from W thin films to W nanostructures:

[0077] A thin film of W (1 nm to 10 nm thick) (e.g., FHR, Pentaco 100, W purity 99.95%) can be deposited on the Cu-Ni alloy according to the preceding paragraph in a vacuum by sputtering or electron beam evaporation, for example in a vacuum (e.g., 3 × 10⁻⁶). -3 Under electron beam evaporation or sputtering at a pressure of, for example, 0.002 mbar, accompanied by, for example, 100 sccm of Ar; a W thin film is deposited to a thickness of 1 nm to 10 nm using, for example, DC plasma at a pressure of, for example, 0.25 kW; a W / Cu-Ni alloy is mounted in the center of a 4-inch quartz tube chamber located within a furnace of a CVD system (e.g., Graphene Square. Inc., TCVD-RF100CA); the chamber is evacuated to a pressure of, for example, 45 mTorr, and then purged, typically at room temperature, with an inert gas such as N2 (e.g., 100 sccm) for, for example, 5 minutes; after purging, the chamber is returned to a vacuum (e.g., 45 mTorr), and then the pressure is increased, for example, with a gas mixture of Ar and H2 (800 sccm and 40 sccm, respectively); to transform the W thin film into W nanostructures (NS). NS are based in various ways on symmetrical W nanoparticles with varying degrees of interparticle aggregation and asymmetric W nanowalls. The W / Cu-Ni alloy was carefully annealed at 4 Torr at elevated temperatures (e.g., 750°C to 950°C or 800°C to 900°C) for extended periods, such as 1 hour, including heating with a continuous supply of, for example, 800 sccm of Ar and 40 sccm of H2.

[0078] 3. Synthesis of highly porous graphene

[0079] Once the W nanostructure appears during the process described in the preceding paragraph, for example, a hydrocarbon source, such as 40 sccm of methane, is introduced into the chamber at 4 Torr under low-pressure CVD conditions with, for example, 300 sccm of Ar and 40 sccm of H2; the growth duration is carefully controlled, for example, from 5 to 120 minutes or from 5 to 60 minutes, depending on the desired porosity or thickness level; subsequently, the furnace is programmed to cool to room temperature under a flow of Ar and H2. Under these conditions, a total CVD time of 30 to 120 minutes yields a graphene layer thickness of approximately 10 nm. A CVD time of 5 minutes yields a graphene layer thickness of approximately less than 1 nm, but this may also depend on other parameters.

[0080] 4. Pre-leaching and conditioning of highly porous graphene:

[0081] Following the growth of highly porous graphene, either directly or after intermediate treatment, the grown highly porous graphene undergoes a pre-leaching process with an oxidant on its exposed surfaces, as detailed below. The sample material can then be rinsed with deionized water and dried before the next step. Subsequently, the highly porous graphene is subjected to persulfate treatment on its exposed surfaces, as detailed below. The sample material can then be rinsed with deionized water and dried before the next step. A carrier layer is then applied to the exposed surfaces of the highly porous graphene.

[0082] 5. Mechanical separation of highly porous graphene with a carrier layer, as further detailed below.

[0083] Recovery of the catalytic substrate:

[0084] After the mechanical separation (delamination) process, the Cu-Ni alloy can be repeatedly used to grow highly porous graphene.

[0085] 6. Polyurethane nonwoven interface (which may be the aforementioned carrier layer or an additional layer added after this process, or another thermoplastic polymer in the form of a nonwoven or other porous woven or knitted structure):

[0086] 1. Typical characteristic filament diameter: 314 nm (standard deviation: 190 nm) (characteristic filament diameter is defined as the average diameter of a single filament in a nonwoven material)

[0087] 2. Typical feature aperture width: 1281 nm (standard deviation: 603 nm) (feature aperture width is defined as the average width of a single topmost aperture in a nonwoven material).

[0088] More generally, the present invention relates, according to its first aspect, to a method for preparing a porous graphene layer with a thickness of less than 100 nm, particularly having an average feature width in the range of 1 nm to 1000 nm, preferably in the range of 5 nm to 900 nm, the method comprising the steps of:

[0089] A catalytically active substrate is provided for catalytically forming graphene under chemical vapor deposition conditions, the catalytically active substrate having a plurality of non-catalytically active domains disposed on its surface, the plurality of non-catalytically active domains having a nanostructure substantially corresponding to the shape of the pores in the obtained porous graphene layer.

[0090] Chemical vapor deposition is performed using a gaseous carbon source to form a porous graphene layer on the surface of a catalytically active substrate. Due to the presence of non-catalytically active domains, pores are formed in situ within the porous graphene layer.

[0091] The average feature width of the hole is defined and measured as follows:

[0092] Obtaining the pore size is challenging due to the elongated and non-uniform shape of the W nanostructure. Therefore, the feature width was chosen and defined as the widest width of the pore rather than its diameter. The feature width of the pore was extracted from scanning electron microscopy (SEM) images using image analysis software (ImageJ). Porous graphene was transferred onto a SiNx chip including pores with a diameter of 4 µm to create a separate section suitable for clear image interpretation. Then, at 1.14 μm... 2 Five representative SEM images of porous graphene were captured to visualize the significant contrast difference between the pores and the surrounding graphene (e.g., black representing pores and gray representing graphene). High-magnification SEM images were required due to the characteristic width of the pores being tens of nm. Subsequently, based on the SEM images, the widest width of each pore opening was measured, and the average of the measured widths was calculated.

[0093] According to a preferred embodiment of the invention, the catalytically active substrate is, in particular, a copper-nickel alloy substrate with a copper content ranging from 85% to 98% or 90% to 99.9% by weight and a nickel content ranging from 2% to 15% by weight or, in particular, greater than 0.04% to 2% by weight, wherein the copper and nickel contents complement each other to 100% by weight of the catalytically active substrate.

[0094] Using such a catalytically active substrate alloy, relatively thick graphene layers with higher porosity than previously available porous graphene layers can be prepared. Unbound by any theoretical explanation, it appears that this particular alloy allows for a specific topology on its surface free of catalytically active domains, and as a result of this topology, allows for the preparation of thicker graphene layers with excellent permeability and liquid barrier properties.

[0095] The thickness of the porous graphene layer is preferably less than 50 nm, more preferably in the range of 1 nm to 20 nm, and particularly in the range of 5 nm to 15 nm or 7 nm to 12 nm.

[0096] For a preferred nickel concentration, the corresponding graphene preferably has an area porosity (defined as the ratio of the total area of ​​pores to the total projected area of ​​the layer) greater than 2.5%, preferably greater than 5%, and preferably in the range of 10% to 70%, and simultaneously has a thickness greater than 1 nm, preferably greater than 2 nm, and preferably in the range of 2 nm to 15 nm. More preferably, the area porosity of the porous graphene layer (defined as the area fraction of pore space in the total graphene layer) is in the range of at least 10%, preferably at least 15%, more preferably at least 20%, at least 25%, or at least 40%.

[0097] According to yet another preferred embodiment, the catalytically active substrate has a plurality of non-catalytically active domains on its surface by applying, preferably by sputtering, electron beam evaporation, or PVD, a substantially continuous tungsten layer. Preferably, the thickness of this tungsten layer is greater than 1 nm, more preferably greater than 3 nm, more preferably greater than 5 nm, or in the range of 1 nm to 10 nm, preferably in the range of 5 nm to 10 nm. Subsequently, the structure is subjected to an annealing step at a pressure below atmospheric pressure, preferably below 100 mTorr or below 4 Torr, particularly in a reducing atmosphere, preferably in the presence of an inert gas such as argon or nitrogen combined with hydrogen, to transform the tungsten film into a plurality of non-catalytically active domains. Typically, annealing is carried out at a temperature in the range of 700°C to 1100°C, more preferably 750°C to 950°C or 800°C to 900°C, typically lasting for a time span 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.

[0098] According to a preferred embodiment, the method is suitable for, for example, obtaining catalytically inactive domains with an average feature 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 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.

[0099] The chemical vapor deposition process for forming a graphene layer can be performed as follows: a porous graphene layer is formed on the surface of a catalytically active substrate using a gaseous carbon source. Pores in the graphene layer are formed in situ due to the presence of non-catalytically active domains. Methane gas is used as the carbon source, preferably in the presence of argon and hydrogen, under reduced pressure, preferably below 50 Torr, preferably below 5 Torr, for a duration preferably between 10 and 120 minutes, preferably below 60 minutes, more preferably below 50 minutes, and most preferably below 35 minutes. This graphene layer deposition process preferably allows for a continuous time span that permits the formation of a graphene layer with an average thickness greater than 5 nm, preferably in the range of 8 nm to 12 nm.

[0100] The porous graphene layer can be removed from the catalytic substrate and can be further applied to a porous, preferably nonwoven or woven, support substrate. Preferably, in order to remove the graphene layer, a support carrier layer is first applied to the surface of the graphene layer opposite to the catalytic substrate, and the sandwich structure of the support layer and graphene is removed from the catalytic substrate. This structure can then be applied directly or indirectly to the porous, preferably nonwoven or woven, support substrate, followed by the removal of the temporary support layer (if necessary).

[0101] As a carrier layer prior to mechanical separation from the substrate, a porous material layer is preferably selected. This type of carrier layer can be divided into two categories: track-etched films and nonwoven porous films. Track-etched films exhibit a porosity typically ranging from less than 1% to 16%, which refers to the percentage of the total surface area occupied by pores (as characterized by electron microscopy imaging). In the case of nonwoven porous films, porosity represents the percentage of the total volume occupied by pores, which typically falls between 40% and 80%.

[0102] The carrier layer can be a woven or nonwoven layer, and it can be based on at least one of the following materials: bio-based materials or synthetic materials or combinations thereof, the former including cotton, rayon, cellulose, chitosan, alginate, starch, keratin, silk fibroin or combinations thereof, and the latter including polyurethane (PU; e.g. Finetex ENE), polyester, polycarbonate, polyamide, polyacrylonitrile, polyethersulfone, polyethylene, polypropylene, polysiloxane, polymethyl methacrylate or combinations thereof.

[0103] Porous material layers can be added to the exposed surface of highly porous graphene layers through lamination.

[0104] After mechanical separation from the catalytic substrate, or for the purpose of mechanical separation from the catalytic substrate, the graphene layer can be attached to a porous, preferably nonwoven or woven, support substrate—preferably having a characteristic filament diameter in the range of 200 nm to 2000 nm, preferably in the range of 300 nm to 1000 nm, particularly with a standard deviation of less than 500 nm, and / or having a characteristic pore size in the range of 500 nm to 50000 nm, preferably in the range of 1000 nm to 10000 nm, particularly with a standard deviation of less than 1000 nm.

[0105] Preferably, the support substrate of the nonwoven or fabric is attached to the graphene layer using solvent-induced bonding or thermal bonding, wherein, preferably, the bonding with the nonwoven is achieved using isopropanol-mediated adhesion combined with annealing and / or heat treatment.

[0106] According to the present invention, particularly and more broadly, after chemical vapor deposition of the porous graphene layer, the porous graphene layer is removed from the substrate in the following manner:

[0107] Exposing the porous graphene layer on the surface of the catalytically active substrate to an aqueous solution containing a dissolved oxidant (particularly leading to the oxidation of non-catalytically active domains, which in the case of an iron oxidant solution, such as a Murakami reagent containing potassium ferricyanide, results in the formation of FeWO4).

[0108] The exposed porous graphene layer on the surface of the catalytically active substrate was subsequently treated directly or indirectly with an aqueous persulfate solution (chemical reaction: S2O8). 2− + Cu = Cu 2+ + 2SO4 2− ),

[0109] The support layer is subsequently laminated and / or formed directly or indirectly onto the exposed porous graphene layer from the side opposite to the catalytically active substrate.

[0110] And the support layer with the exposed porous graphene layer is mechanically separated from the catalytically active substrate.

[0111] It should be noted that for the non-catalytically active domains (especially W nanoparticles) to dissolve, their oxidation must precede their dissolution. When using 0.1 M NaOH at mild temperatures (40°C to 60°C), the oxidation reaction of W nanoparticles, for example due to the oxygen present in the water, is slow. As a result, the removal of W nanoparticles takes an excessively long time, and even then, it cannot be completely removed within a realistic reaction time, leaving residues. Over time, not only do some W nanoparticles remain on the surface of the metal catalyst, but NaOH also crystallizes on the graphene surface. Therefore, the slow kinetics of 0.1 M NaOH alone render it essentially unusable.

[0112] Therefore, the aqueous solution containing the dissolved oxidant preferably contains a dissolved, preferably iron-based oxidant, as well as sodium hydroxide and / or potassium hydroxide. The dissolved oxidant according to the invention does not include gases such as oxygen present in the solution, which are not considered "dissolved oxidants" because they are not dissolved.

[0113] Therefore, according to the present invention, a method for incomplete chemical dissolution of the substrate is proposed.

[0114] The key elements of this method are a novel pre-leaching process (removal of W nanoparticles) and water intercalation separation (water intercalation separation of highly porous graphene layers).

[0115] The bonding between graphene and metals plays a crucial role in graphene separation (delamination).

[0116] In this method, the W film is transformed into W nanoparticles, which are then transformed into WC (tungsten carbide) nanoparticles upon introduction of a carbon feedstock. Carbon atoms at the pore edges of the highly porous graphene bind to the WC nanoparticles, and the binding energy between WC and CC is very high. Therefore, it is impossible to detach the highly porous graphene from the metal catalyst via electrochemical and mechanical delamination. To overcome this, the proposed method provides a suitable and adapted pre-leaching step with an oxidant, followed by a step that gently disrupts (conditions) the adhesion between the catalytic substrate and the highly porous graphene layer without completely chemically dissolving the substrate.

[0117] The proposed process involves a pre-leaching procedure using a dissolved oxidant (e.g., Murakami reagent) to remove WC nanoparticles, and a persulfate (e.g., APS, ammonium persulfate) treatment, particularly for partial etching at the interface between Cu-Ni alloys and graphene. Without being bound by any interpretation, the APS solvent permeates through the pores of the exposed surface of the porous graphene layer, allowing for rapid and spatially uniform lateral diffusion and subsequent local etching throughout the interface. A support layer is then applied, followed by (water intercalation) separation, where water, for example, permeates into the interface between the hydrophobic graphene and the hydrophilic Cu-Ni surface due to capillary forces. Thus, highly porous graphene can be readily separated from the catalytic surface.

[0118] The proposed method is not only more reliable and stable, and economically and ecologically beneficial, but it also allows for a significant reduction in production time of at least two or three times compared to pre-leaching and electrochemical separation processes.

[0119] According to a preferred embodiment of the proposed method, the catalytically active substrate with a porous graphene layer is rinsed with water, preferably with distilled water, and more preferably with repeated rinsing with distilled water before treatment with a persulfate solution.

[0120] According to another preferred embodiment of the proposed method, the aqueous solution containing the dissolved oxidant is selected from aqueous hydroxide solutions containing ferricyanide or acidic solutions containing hydrogen peroxide (e.g., HNO3 + H2O2 or H2SO4 (3% wt / wt) + H2O2 (9% wt / wt)).

[0121] Preferably, the aqueous solution containing the dissolved oxidant is selected from aqueous solutions of sodium hydroxide and / or potassium hydroxide that further contain sodium ferricyanide and / or potassium ferricyanide, such as Murakami reagent. The reaction that typically occurs here is: tungsten carbide is oxidized by (potassium)ferricyanide; a chemical reaction occurs between WO3 and (Na)OH to form Na2WO4 (sodium tungstate) and water; sodium tungstate is water-soluble and serves as a source of tungsten recovery for subsequent chemical synthesis.

[0122] Preferably, in such an aqueous solution containing a dissolved oxidant, the weight ratio of potassium hydroxide (and / or sodium) is in the range of 0.05% to 10%, preferably in the range of 0.1% to 3%, or in the range of 0.3% to 2%, or in the range of 0.5% to 1.5%, and / or the weight ratio of potassium ferricyanide (and / or sodium) relative to water is in the range of 0.05% to 10%, preferably in the range of 0.1% to 3%, or in the range of 0.3% to 2%, or in the range of 0.5% to 1.5%, in each case relative to 100% water used to prepare the solution.

[0123] Preferably, for the aqueous solution containing the dissolved oxidant, a diluted version of the starting reagent is used, which is prepared by adding 10 g of potassium ferricyanide and 10 g of potassium hydroxide to 100 mL of water, such that the starting solution has a potassium ferricyanide concentration of 0.3 M and a potassium hydroxide concentration of 1.8 M. Preferably, the solution is diluted with water by at least 80%, or at least 90%, or up to 95%, thus reducing the concentration from the initial concentration to 1 / 5, 1 / 10, or 1 / 20, respectively.

[0124] Preferably, the aqueous solution containing the dissolved oxidant is an aqueous solution containing, preferably only containing, potassium hydroxide (and / or sodium) and potassium ferricyanide (and / or sodium), wherein the concentration of (potassium) hydroxide is in the range of 0.05 M to 0.4 M, preferably in the range of 0.07 M to 0.2 M, and the concentration of (potassium) ferricyanide is in the range of 0.005 M to 0.1 M, preferably in the range of 0.01 M to 0.04 M.

[0125] Alternatively, the weight ratio of sodium hydroxide to potassium ferricyanide may be in the range of 0.2 to 5, preferably in the range of 0.5 to 2, or in the range of 0.8 to 1.2.

[0126] According to another preferred embodiment of the proposed method, the step of treatment with an aqueous solution containing a dissolved oxidant is carried out at a temperature ranging from 15°C to 35°C, preferably from 20°C to 30°C, and / or for a duration ranging from 0.5 minutes to 20 minutes, preferably from 1 minute to 5 minutes.

[0127] Preferably, the persulfate aqueous solution contains a persulfate selected from the group consisting of ammonium persulfate, sodium persulfate, potassium persulfate, or combinations thereof, wherein the concentration of the persulfate is preferably in the range of 0.05 M to 2 M, and more preferably in the range of 0.075 M to 1.5 M.

[0128] The treatment with persulfate aqueous solution is typically carried out at a temperature ranging from 15°C to 35°C, preferably from 20°C to 30°C, and / or for a short duration, such as from 1 second to 180 seconds, preferably from 5 seconds to 120 seconds, 5 seconds to 60 seconds, or 5 seconds to 20 seconds.

[0129] According to another preferred embodiment of the proposed method, the substrate with the porous graphene layer is rinsed with water, preferably with distilled water, and more preferably repeatedly with distilled water directly after the step of treatment with persulfate aqueous solution.

[0130] According to another preferred embodiment of the proposed method, the mechanical separation of the carrier layer with the exposed porous graphene layer from the substrate is performed by water intercalation separation, preferably by gradual immersion in water, more preferably distilled water. In this context, mechanical separation means that the mechanical separation is not accomplished by overcoming interfacial adhesive forces, but by releasing the adhesive through pre-immersion and mediating separation through water intercalation and (gentle) separation, in contrast to mechanical intercalation methods.

[0131] The carrier layer is preferably a porous carrier layer, and more preferably a carrier layer intended for end use (e.g., for clothing), as further defined below.

[0132] According to another preferred embodiment of the proposed method, the catalytically active substrate is a copper-nickel alloy substrate with 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, wherein the copper content and nickel content complement each other to 100% by weight of the catalytically active substrate (1), wherein preferably the catalytically active substrate has a nickel content in the range of 0.06% to 1% by weight or 0.08% to 0.8% by weight, which is made up to 100% by weight by the copper content.

[0133] Furthermore, the present invention relates to a graphene layer, preferably on at least one carrier layer, which is obtained using the methods given above.

[0134] The thickness of such a layer can be less than 50 nm, preferably in the range of 1 nm to 20 nm, and particularly in the range of 5 nm to 15 nm or 7 nm to 12 nm.

[0135] And / or its surface gap ratio may be in the range of at least 10%, preferably at least 15%, more preferably at least 20%, at least 25%, at least 30%, or at least 40%.

[0136] Furthermore, the present invention relates to textiles or garments having at least one graphene layer prepared using the methods defined above and / or as defined above, preferably a graphene layer on at least one carrier layer, wherein the textiles or garments are preferably in the form of waterproof and / or water-repellent and / or breathable garments.

[0137] Last but not least, the present invention relates to the use of graphene layers prepared using the methods defined above and / or graphene layers according to the above, preferably graphene layers on at least one carrier layer, as semi-permeable membranes, particularly in the field of clothing or in textile applications in the technical field of providing water barriers in electronic and / or mobile devices.

[0138] Further embodiments of the invention are given in the dependent claims. Attached Figure Description

[0139] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, which are for illustrative purposes only and not for limiting the scope of the invention. In the drawings,

[0140] Figure 1 A schematic diagram of the first stage of the method is shown, including the growth process of porous graphene and the pre-leaching process using Murakami reagent;

[0141] Figure 2 Representative SEM images of the surface of a metal catalyst with a graphene layer before (a) and after a 2-minute pre-leaching process with Murakami reagent are shown.

[0142] Figure 3 Representative SEM images of the surface of a metal catalyst with a graphene layer after pre-leaching with Murakami reagent at different dilutions are shown, and depending on the dilution of the Murakami reagent, (a) undiluted, (b) 80% diluted, (c) 90% diluted, and (d) 95% diluted.

[0143] Figure 4 A schematic diagram of the second stage of the method is shown, including APS treatment and water separation;

[0144] Figure 5 Representative SEM images of the metal catalyst surface are shown: (a) after pre-leaching with Murakami reagent without a graphene layer and (b) after pre-leaching with Murakami reagent and APS treatment without a graphene layer.

[0145] Figure 6 Representative AFM images of (a) porous graphene on SiO2 and (b) porous graphene on a porous polymer film are shown.

[0146] Figure 6 The presence of tungsten particles is shown after sodium hydroxide treatment for 5 minutes (a), 10 minutes (b), and 15 minutes (c).

[0147] Figure 7 The formation of sodium hydroxide crystals after treatment with sodium hydroxide alone for 15 minutes (a), 20 minutes (b), and 30 minutes (c) is shown.

[0148] Figure 8The effects of treatment with Murakami reagent for 10 seconds (a), 20 seconds (b), and 30 seconds (c) are shown. Detailed Implementation

[0149] Figure 1 The steps of the first stage of the proposed method are schematically illustrated up to and including pre-leaching. In the first step, a layer of non-catalytically active material 12, specifically the tungsten layer 12 from the tungsten deposition step 11, is formed on the surface of a catalytic copper / nickel substrate. Subsequently, the coated substrate 1 is optionally introduced into a closed chamber and then subjected to thermal annealing 15 under reducing conditions. The result is the formation of a pattern of non-catalytically active domains 2 on the surface 3 of the catalytic substrate 1. In the subsequent step 4, which again takes place in an optional closed chamber to grow a graphene layer on the substrate 1, the substrate 1 is subjected to chemical vapor deposition of methane to form a porous graphene layer 5 interrupted by non-catalytically active domains 2, which locally form pores for future porosity. In the subsequent step of removing the closed chamber (if actually used), the layered substrate is released.

[0150] The layered substrate was then subjected to a pre-leaching step by immersion in Murakami reagent to remove non-catalytically active domain 2. The conditions were as follows: 10 g KOH + 10 g K3[Fe(CN)6] + 100 ml water, for 2 minutes.

[0151] The layered substrate is then subjected to rinsing in deionized water (8, as mentioned herein, deionized water is water that has been treated to remove all ions, which generally means the removal of all dissolved mineral salts, and typically has a conductivity of less than 10 μS / cm or less than 1 μS / cm or 0.5 μS / cm; distilled water that has been boiled to evaporate and then condensed to leave most of the impurities) for 2 minutes.

[0152] Figure 2 The following are representative SEM images of the resulting structure, namely the surface of the metal catalyst 1 with graphene layer 5, before and after a 2-minute pre-leaching process with Murakami reagent (a) and (b). As can be seen from the comparison of these images, the un-pre-leached representation (…) Figure 2 Image a) shows bright spots of non-catalytically active domain 2 (i.e., tungsten points) on the surface of catalytic substrate 1 after pre-leaching. Figure 2 b) was completely removed. This was confirmed by elemental analysis of the separated graphene layers and by examining the surface of the catalytic substrate 1 after the highly porous graphene layers were removed, as will be further detailed below.

[0153] This is a major advantage compared to previously known pre-leaching processes, where, under many conditions, tungsten residue remains in / on the highly porous graphene layer in previously known pre-leaching processes without oxidizing components. This presents problems on the one hand with tungsten recovery during recycling, and on the other hand with the undesirable tungsten content in the final graphene layer.

[0154] Figure 3 Representative SEM images of the metal catalyst with graphene layer after pre-leaching with Murakami reagent at different dilutions are shown, and depending on the Murakami reagent dilution, (a) undiluted, (b) 80% diluted, (c) 90% diluted, and (d) 95% diluted (see also experimental information in further detail below).

[0155] The effectiveness of different dilutions of Murakami reagent in removing tungsten carbide particles from the catalytic substrate surface was investigated at different time points. This is because undiluted Murakami reagent successfully removed tungsten completely within 10 seconds, but caused partial detachment of the graphene layer during deionized water rinsing. Therefore, it is not always optimal for graphene film applications. To address this issue and prevent any potential damage, the use of diluted Murakami reagent is recommended. Three dilution percentages were tested: 80%, 90%, and 95%. 80% diluted Murakami reagent required 30 seconds to remove tungsten without causing any damage. 90% diluted Murakami reagent effectively removed tungsten from the substrate surface within 60 seconds without any damage. Similarly, 95% diluted Murakami reagent successfully etched away all tungsten from the catalytic substrate surface within 120 seconds without observed damage. Therefore, reaction time can be precisely controlled to match subsequent processes if necessary.

[0156] Figure 4 The steps in the subsequent second stage of the proposed method are schematically illustrated, up to and including pre-leaching. In this second stage, the pre-leaching is performed as follows... Figure 1 The structure obtained from the process shown is subjected to persulfate treatment, i.e., immersion in an aqueous persulfate solution (step 9). The corresponding conditions are as follows: 0.1 M ammonium persulfate solution ((NH4)2S2O8 in water, APS) for 10 seconds.

[0157] This short-span APS treatment, performed on the exposed surface of the porous graphene layer 5, allows for slight edge etching of the interface between the porous graphene layer 5 and the catalytic substrate 1, resulting in the release of bonds 13 between the two layers, as the APS solution can reach the surface 3 of layer 1 through the pores 6 in layer 5. However, the conditions are adjusted so that the substrate layer 1 is not completely etched away.

[0158] Following the edge etching step performed with APS, the catalytic substrate 1, with a porous graphene layer 5 on its surface 3, was rinsed with deionized water. The conditions were as follows: 60 seconds in deionized water.

[0159] This results in a structure in which the porous graphene layer 5 is located on the catalytic substrate 1 ( Figure 4 (The rightmost illustration in the top row), but the previously fairly strong bond between the catalytic substrate 1 and the graphene layer 5 is released 13, thus the structure is ready for the gentle mechanical removal of the porous graphene layer 5 from the substrate 1. This is initiated by first applying a porous membrane or support layer 16 to the exposed surface of the porous graphene layer 5 in the support layer application step 14. This can be a lamination step, but it can also be a step of forming the porous membrane layer 16 in situ on the porous graphene layer 5.

[0160] Once the stacked structure 21 of the porous membrane layer 16 and the porous graphene layer 5 is formed, it is ready to be removed from the catalytic substrate 1. This can be achieved, for example, by gradually immersing structures 1 and 21 in a bath of aqueous solution or deionized water 17. The final structure 21 will then gradually float on the surface 18 of the water with a free-floating portion 19, and will gradually be released from the substrate 1, so that the portion 20 remaining on the substrate will become smaller and smaller. After this process, the supported, released porous graphene layer 21, floating in a controlled manner on the surface 18 of the water, can be picked up without causing any damage to the structure 21, particularly by using its upper surface.

[0161] Figure 5 Representative SEM images of the metal catalyst surface are shown: (a) after a Murakami pre-leaching process without a graphene layer, and (b) after a Murakami pre-leaching process followed by APS treatment without a graphene layer. As can be seen from the images, tungsten is essentially absent on the copper / nickel catalyst substrate after the Murakami pre-leaching process. Therefore, the pre-leaching step ensures efficient and complete removal of tungsten. However, the roughness of the catalyst substrate becomes noticeable due to oxidation by NaOH during the pre-leaching process, necessitating further treatment to achieve a smooth surface. Conversely, the APS treatment following the pre-leaching process loosens the bond between the graphene layer and the catalyst substrate surface and gently etches the interfacial surface, resulting in a smooth surface. Therefore, the APS treatment has proven beneficial for the recovery of the catalyst substrate, promoting its reusability.

[0162] Figure 6 Representative AFM images of (a) porous graphene on SiO2 and (b) representative SEM images of porous graphene on porous polymer films are shown. The samples are based on... Figure 1 and Figure 4 The process involves preparing porous graphene. For example, one preparation method involves synthesizing porous graphene, then pre-leaching it using Murakami, followed by APS treatment. This treatment prepares the porous graphene layer for separation, regardless of whether it has a porous membrane. After the separation process, porous graphene without a porous membrane is transferred onto SiO2, while porous graphene with a porous membrane is directly picked up. It is worth noting that, as... Figure 6 As shown in (a) and (b), the structural integrity of the porous graphene remained intact even after undergoing the pre-leaching process and subsequent APS treatment. This observation underscores the fact that these processes do not adversely affect the structural characteristics of the porous graphene.

[0163] Specific working examples:

[0164] Preparation of Cu / Ni substrate:

[0165] A Cu-Ni alloy catalyst was formed for the synthesis of thick, highly porous graphene. Untreated raw Cu foil (0.025 mm, 99.8%, product number 49686, Alfa Aesar) was coated with a Ni film via physical vapor deposition (PVD, sputtering, or electron beam evaporation). The Ni film was then applied using sputtering (FHR, Pentaco 100, Ni purity 99.95%) at a depth of 6 × 10⁻⁶ mm. -3 Ni films (thicknesses of 50 nm to 500 nm or 0.01 µm to 2.2 µm) were coated at 200 sccm of Ar and 0.25 kW plasma power for 85 to 18700 seconds or 425 to 4250 seconds (depending on the thickness of the Ni film). The bilayer Ni / Cu was then annealed in a low-pressure chemical vapor deposition (LP-CVD, Graphene Square, Inc., TCVD-RF100CA) system. The furnace temperature was first raised to 1000 °C at 50 sccm of H₂ for 60 minutes. An annealing process was then performed at 1000 °C in an H₂ environment for 15 minutes to prevent undesirable oxidation. Subsequently, the Cu-Ni alloy was formed in the bulk state by interdiffusion due to complete dissolution in the other. To rapidly reduce the temperature to room temperature, the furnace was moved downstream. A cooling rate of 50 °C / min was achieved while maintaining the same H₂ level.

[0166] Preparation of W nanostructures on Cu / Ni substrates:

[0167] Following the formation of the Cu-Ni alloy, a thin film of W (2 nm to 10 nm) was deposited on the Cu-Ni alloy using sputtering (FHR, Pentaco 100, W purity 99.95%). The deposition was achieved at 3 × 10⁻⁶ ppm using Ar sputtering at 0.25 kW DC power and 100 sccm. -3 Deposition can be performed at millibars for 15 to 75 seconds to achieve various thicknesses.

[0168] The prepared W / Cu-Ni alloy was placed in the center of the furnace in the LP-CVD system. The chamber was evacuated to 0.05 mTorr using a turbomolecular pump to remove any residual gases, and then the pressure was increased to 45 mTorr with 50 sccm of Ar. The chamber was then purged with N2 for 5 minutes and evacuated to 45 mTorr. The furnace was heated to a growth temperature of 750°C to 950°C or 800°C to 950°C at 4 Torr with a supply of 800 sccm of Ar and 40 sccm of H2. Once the target temperature was reached, it was held for 10 minutes to stabilize. Simultaneously, the W film transformed into W nanostructures due to solid-state dehumidification. Since there is no solid solution between the Cu-Ni alloy and W, different morphologies of W nanostructures can be obtained without any pre-lithography process.

[0169] Preparation of graphene layers:

[0170] When the desired morphology of W was achieved, highly porous graphene was synthesized at 4 Torr for 30 minutes with the introduction of 40 sccm of CH4, 40 sccm of H2, and 300 sccm of Ar. Then, the temperature was programmed to cool to room temperature in a mixture of 800 sccm of Ar and 40 sccm of H2. The resulting structure was... Figure 2 The answer is given in a (see also above).

[0171] Pre-leaching steps:

[0172] Following the CVD synthesis of highly porous graphene, a pre-leaching process was performed to remove the W nanostructures while the highly porous graphene was exposed (i.e., freely accessible from the side opposite to the catalytic substrate). The synthesized highly porous graphene on the catalytic substrate was immersed in Murakami reagent, i.e., 10 g KOH + 10 g K3[Fe(CN)6] + 100 ml water, at room temperature (temperature 20 °C, 293.15 K, and absolute pressure 1 atm, 101.325 kPa, also known as ambient temperature and pressure, abbreviated as NTP), for 10 to 120 seconds as a function of reagent concentration (see also below). The highly porous graphene / Cu-Ni alloy sample was then rinsed twice with fresh deionized water for 60 seconds each time, followed by drying by purging with N2 gas. The resulting structure was... Figure 2 The answer is given in b (see also above).

[0173] Using the same starting material, a series of different dilutions and impregnation times were tested to study the pre-leaching behavior: undiluted for 10 seconds, 80% diluted for 30 seconds, 90% diluted for 60 seconds, and 95% diluted for 120 seconds. The resulting structures were... Figure 3 The information is given in (see also above).

[0174] Graphene layer release:

[0175] To release the bond between the Cu-Ni alloy catalyst substrate and the highly porous graphene, the Cu-Ni alloy catalyst substrate with the highly porous graphene layer was immersed in a 0.1 M ammonium persulfate solution ((NH4)2S2O8, APS, 248614, Sigma Aldrich) at room temperature (NTP) for 10 seconds. The resulting structure was then rinsed with deionized water for 60 seconds.

[0176] Assembly of highly porous graphene on porous nonwoven materials:

[0177] The highly porous graphene was assembled with a porous nonwoven material such as polyurethane (Finetex ENE, DT007). After the pre-extraction process, the nonwoven material was bonded to the highly porous graphene in different ways: (1) isopropanol (IPA) mediated bonding and (2) thermal lamination.

[0178] The assembly of highly porous graphene with a porous nonwoven material (i.e., a characteristic pore size of approximately 1.2 μm and a thickness of 9 μm) was achieved using an IPA-mediated method and / or thermal lamination. The IPA-mediated bonding process involves directly laminating a thin nonwoven material onto pre-impregnated highly porous graphene at room temperature. IPA is then gently applied after lamination until complete wetting is achieved. The laminated sample is subsequently dried under ambient conditions. During the drying process, the interfacial contact between the nonwoven material and the highly porous graphene is significantly enhanced as the IPA evaporates, ensuring a robust bond. To further enhance this bonding, the dried sample is heated at 150 °C for 10 minutes on a hot plate (IKA, C-Mag HS 7). For the thermal lamination method, a thin nonwoven material is directly laminated onto pre-impregnated highly porous graphene, where the temperature varies according to the glass transition temperature of the polymer. Alternatively, a heat lamination method can be employed, in which a thin nonwoven material is directly laminated onto pre-impregnated highly porous graphene at a temperature adjusted for the glass transition temperature of the polymer. In the case of polyurethane films, a polyurethane carrier layer is directly laminated onto the pre-impregnated highly porous graphene at 130°C. After the lamination process, the sample is heated on a hot plate (IKA, C-Mag HS 7) at 150°C for 10 minutes to further improve adhesion.

[0179] Alternative approaches to working with nonwoven materials include, for example, depositing fibers directly onto a porous graphene substrate via electrospinning or melt spinning.

[0180] Graphene layer separation:

[0181] To exfoliate highly porous graphene with a support layer from a Cu-Ni alloy catalyst substrate, the Cu-Ni alloy catalyst substrate with the highly porous graphene on the support layer was gradually immersed in deionized water at a certain angle relative to the water surface with the highly porous graphene face upwards. This allowed the highly porous graphene on the support layer to gradually float on the water surface while being exfoliated from the Cu-Ni alloy catalyst substrate. The resulting structure... Figure 6 The answer is given in b (see also above).

[0182] For analytical purposes, the sample was transferred onto a Si wafer with a 280 nm thick SiO2 layer to study highly porous graphene. See also Figure 6 a (see also above).

[0183] Membrane preparation for measuring gas flow rate and inlet water pressure:

[0184] The highly porous graphene and nonwoven material assembly was cut into small pieces of approximately 1 cm × 1 cm. A 2 cm × 2 cm frame for assembling the membrane was made of stainless steel, with a 2 mm hole in the center of the frame. The assembled membrane was laid on a metal foil containing holes with a diameter of 0.8 mm, which served as a mechanical support. The entire membrane was then attached to a carbon ribbon, with a hole punched in the center on either side of the membrane, and then clamped through the frame. Note that each hole needs to be axially aligned.

[0185] Gas flow measurement:

[0186] Nitrogen permeation flow rate was characterized using custom settings. The membrane was placed in a custom fixture and sealed using rubber O-rings on both sides of the membrane. Nitrogen was distributed to the feed side, with pressure controlled by a regulator (SMC, IR1000-F01), and the upstream pressure rise was measured using a digital pressure gauge (OMEGA, HHP91). A mass flow meter (MKS, Germany) measured the downstream flow rate in sccm. All measurements were performed at room temperature.

[0187] The highly porous graphene assembly on the nonwoven material was fabricated by synthesizing and assembling the highly porous graphene as described above. The highly porous graphene was synthesized on a catalyst, wherein a 150 nm Ni film was deposited on top of a commercial Cu foil via a sputtering process, followed by annealing of the bilayer Ni / Cu catalyst to transform it into a Cu-Ni alloy. The synthesis of highly porous graphene with approximately 24% porosity and a thickness of 5 nm on the Cu-Ni alloy with a 4 nm W film was carried out at 800 °C for 30 minutes at 4 Torr with the introduction of 40 sccm of CH4, 40 sccm of H2, and 300 sccm of Ar. Furthermore, to investigate how the porosity of the graphene affected the gas flow rate, the synthesis duration was adjusted from 30 minutes to 60 minutes, resulting in a decrease in porosity. After assembling highly porous graphene with nonwoven materials using an IPA-mediated method, the metal catalyst was etched away with 0.5 M APS, rinsed with a mixture of 5% ethanol and deionized water, and then dried.

[0188] A highly porous graphene / nonwoven membrane is mounted on a stainless steel frame. The frame with the membrane is placed and clamped in a custom-made fixture, which is connected to the gas line via a regulator and then to a mass flow meter. Note that the mass flow meter is limited to 20 sccm of N2. The pressure of N2 is increased slowly and gradually. For example, the pressure of N2 is increased at 20 mbar intervals and held for 1 minute to stabilize the pressure until the mass flow meter displays 20 sccm of N2.

[0189] To specifically illustrate the differences between the treatment of a catalytic substrate (with tungsten particles as non-catalytically active particles) and the formation of a graphene layer thereon under conditions disclosed in WO2021121952 using sodium hydroxide, the following experiments were conducted.

[0190] As mentioned, in order for W nanoparticles to dissolve, the oxidation of W nanoparticles must precede their dissolution.

[0191] The oxidation reaction of W nanoparticles was very slow when using 0.1 M NaOH at a mild temperature (40°C to 60°C). As a result, the removal of W nanoparticles took more than 10 minutes.

[0192] Even so, W nanoparticles cannot be completely removed, and some residues always remain within the optimal reaction time.

[0193] Figure 7 The results of the corresponding experiments are shown. Using the procedure according to WO2021121952, i.e., 0.1 M NaOH at 40 °C, the results are shown as a), b), and c) at 5 minutes, 10 minutes, and 15 minutes, respectively. Circles indicate the locations of remaining W nanoparticles. For the 5-minute reaction (a), most of the W nanoparticles remain on the surface, hindering mechanical separation. For the 10-minute reaction (b), many W nanoparticles are still observed on the surface. For the 15-minute reaction (c), a small number of W nanoparticles are present on the surface; however, longer processes may cause additional problems.

[0194] Over time, not only do some W nanoparticles remain on the surface of the metal catalyst, but NaOH also crystallizes on the graphene surface.

[0195] Figure 8 The results of the corresponding experiments regarding the presence of sodium hydroxide crystals are shown. After a reaction time of 15 minutes (a), a large amount of NaOH crystals had formed on the highly porous graphene surface, with a small amount of W nanoparticles remaining. After a reaction time of 20 minutes (b), although most of the W nanoparticles disappeared, an increased number of NaOH crystals were generated on the highly porous graphene surface. After a reaction time of 30 minutes (c), many large NaOH crystals were formed on the highly porous graphene surface.

[0196] The presence of crystals is problematic because they cause physical contamination of the membrane surface and pores, which can lead to blockage and interfere with membrane function.

[0197] Crystal fragments (with an alkaline pH) pose a further problem because they may negatively interact with materials that subsequently come into contact with the graphene surface, such as laminates or other support layers.

[0198] A further problem is the inconsistency in processing. The accumulation of NaOH crystals over time leads to a processing trade-off between the dissolution of W particles and the formation of NaOH crystals. This results in suboptimal removal of W particles compared to the proposed methods, particularly the Murakami method, which offers rapid and residue-free processing.

[0199] Furthermore, the severe oxidation of the Cu-Ni surface makes the substrate unsuitable for recycling when used for long processing times.

[0200] Therefore, rapid kinetics are crucial for the complete removal of W nanoparticles and the recovery of metal catalysts.

[0201] Therefore, the slow kinetics of 0.1 M NaOH severely limit its availability.

[0202] Conversely, when using Murakami reagent, the rapid chemical reaction of W nanoparticles with WO3 causes the W nanoparticles to dissolve rapidly within 30 seconds without damaging the underlying substrate.

[0203] This rapid and intense chemical reaction enables the rapid and complete removal of W nanoparticles, such as... Figure 9 As shown.

[0204] Therefore, the proposed oxidizing agents, especially the Murakimi reagent, show particularly advantageous effects in achieving rapid reaction kinetics by reducing the reaction time from more than 10 minutes for NaOH to less than 30 seconds for Murakimi reagent.

[0205] List of reference numerals

[0206] 1. Catalytic substrate, copper / nickel substrate

[0207] 2. No catalytic active domain

[0208] 3. Surface of the substrate

[0209] 4. Steps for growing graphene layers on a substrate

[0210] 5 porous graphene layers

[0211] Hole in 65

[0212] 7. Dissolved oxidizing agent solution, Murakami reagent

[0213] 8. Aqueous rinsing solution, deionized water

[0214] 9. Persulfate aqueous solution, APS solution

[0215] 10. Aqueous rinsing solution, deionized water

[0216] 11 Tungsten Deposition

[0217] 12 continuous tungsten film layers

[0218] The combination released between 131 and 5

[0219] Step 14: Applying the carrier layer 16

[0220] 15. Hot annealing steps

[0221] 16 carrier layers

[0222] 17. Aqueous solution, deionized water

[0223] 1817 surface

[0224] The free-floating section of 1921

[0225] The portion of 2021 that is still on the base.

[0226] 21 Supported Released Porous Graphene Layers

Claims

1. A method for preparing a porous graphene layer (5) with a thickness of less than 100 nm, said porous graphene layer (5) having pores (6) with an average characteristic width in the range of 1 nm to 1000 nm as defined in the specification, said method comprising the following steps: A catalytically active substrate (1) is provided for catalyzing the formation of graphene under chemical vapor deposition conditions, the catalytically active substrate (1) having a plurality of non-catalytically active domains (2) disposed on its surface (3), the plurality of non-catalytically active domains (2) having nanostructures substantially corresponding to the shape of the pores (6) in the obtained porous graphene layer (5); Chemical vapor deposition is performed using a gaseous carbon source to form the porous graphene layer (5) on the surface (3) of the catalytically active substrate (1), and the pores (6) in the porous graphene layer (5) are formed in situ due to the presence of the non-catalytically active domain (2). After the chemical vapor deposition of the porous graphene layer (5), the porous graphene layer (5) is removed from the substrate (3) in the following manner: The exposed porous graphene layer (5) on the surface (3) of the catalytically active substrate (1) is subjected to an aqueous solution containing a dissolved oxidant. The exposed porous graphene layer (5) on the surface (3) of the catalytically active substrate (1) is subsequently treated directly or indirectly with an aqueous persulfate solution. The support layer (16) is then laminated and / or generated directly or indirectly onto the exposed porous graphene layer (5) from the side opposite to the catalytically active substrate (1). And the support layer (16) with the exposed porous graphene layer (5) is mechanically separated from the catalytically active substrate (1).

2. The method according to claim 1, wherein the catalytically active substrate (1) with the porous graphene layer (5) is rinsed with water, preferably with distilled water, and more preferably repeatedly with distilled water before treatment with the persulfate solution.

3. The method according to any one of the preceding claims, wherein the aqueous solution containing the dissolved oxidant is selected from: an aqueous hydroxide solution containing ferricyanide, or an acidic solution containing hydrogen peroxide. Preferably, the aqueous solution containing the dissolved oxidant is selected from an aqueous solution of sodium hydroxide and / or potassium hydroxide containing sodium ferricyanide and / or potassium ferricyanide. More preferably, the aqueous solution containing the dissolved oxidant consists of water, aqueous sodium hydroxide and / or potassium hydroxide, and sodium ferricyanide and / or potassium ferricyanide. More preferably, in the aqueous solution containing the dissolved oxidant, the weight ratio of potassium hydroxide is in the range of 0.05% to 10%, preferably in the range of 0.1% to 3%, or in the range of 0.3% to 2%, or in the range of 0.5% to 1.5%, and / or the weight ratio of potassium ferricyanide relative to water is in the range of 0.05% to 10%, preferably in the range of 0.1% to 3%, or in the range of 0.3% to 2%, or in the range of 0.5% to 1.5%, in each case relative to 100% water used to prepare the solution. And / or the weight ratio of potassium hydroxide to potassium ferricyanide is in the range of 0.2 to 5, preferably in the range of 0.5 to 2, or in the range of 0.8 to 1.

2.

4. The method according to claim 3, wherein the step of treatment with the aqueous solution containing the dissolved oxidant is carried out at a temperature ranging from 15°C to 35°C, preferably from 20°C to 30°C, and / or for a time span ranging from 0.5 minutes to 20 minutes, preferably from 1 minute to 5 minutes.

5. The method according to any one of the preceding claims, wherein the persulfate aqueous solution comprises a persulfate selected from: ammonium persulfate, sodium persulfate, potassium persulfate, or a combination thereof, wherein preferably the concentration of the persulfate is in the range of 0.05 M to 2 M, more preferably in the range of 0.075 M to 1.5 M.

6. The method according to claim 5, wherein the step of treatment with the persulfate aqueous solution is carried out at a temperature ranging from 15°C to 35°C, preferably from 20°C to 30°C, and / or for a time span ranging from 1 second to 180 seconds, preferably from 5 seconds to 120 seconds, 5 seconds to 60 seconds, or 5 seconds to 20 seconds.

7. The method according to any one of the preceding claims, wherein, directly after the step of treatment with the persulfate aqueous solution, the substrate with the porous graphene layer (5) is rinsed with water, preferably with distilled water, and more preferably repeatedly with distilled water.

8. The method according to any one of the preceding claims, wherein the mechanical separation of the carrier layer (16) with the exposed porous graphene layer from the substrate is carried out by water intercalation separation, preferably by gradual immersion in water, preferably distilled water.

9. The method according to any one of the preceding claims, wherein the carrier layer (16) is a porous carrier layer, preferably the carrier layer is intended for end use, particularly as a semi-permeable membrane, particularly in the field of clothing or in textile applications in the technical field of providing a water barrier in electronic and / or mobile devices.

10. The method according to any one of the preceding claims, wherein the catalytically active substrate (1) is a copper-nickel alloy substrate with a copper content in the range of 98% by weight to less than 99.96% by weight and a nickel content in the range of greater than 0.04% by weight to 2% by weight, wherein the copper content and the nickel content are complementary to 100% by weight of the catalytically active substrate (1), wherein preferably the catalytically active substrate (1) has a nickel content in the range of 0.06% by weight to 1% by weight or 0.08% by weight to 0.8% by weight, which is made up to 100% by weight by the copper content.

11. The method according to any one of the preceding claims, wherein the aqueous solution containing the dissolved oxidant is an aqueous solution comprising at least one of potassium hydroxide and sodium hydroxide and at least one of potassium ferricyanide and sodium ferricyanide, preferably an aqueous solution comprising at least one of potassium hydroxide and sodium hydroxide and at least one of potassium ferricyanide and sodium ferricyanide, wherein the concentration of potassium hydroxide is in the range of 0.05 M to 0.4 M, preferably in the range of 0.07 M to 0.2 M, and wherein the concentration of potassium ferricyanide is in the range of 0.005 M to 0.1 M, preferably in the range of 0.01 M to 0.04 M.

12. A graphene layer (5) on at least one carrier layer (16), wherein the graphene layer (5) is obtainable by a method according to any one of the preceding claims or the graphene layer (5) is obtained by a method according to any one of the preceding claims.

13. The graphene layer (5) according to claim 12, wherein the thickness of the graphene layer (5) is 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 the porosity of the graphene layer (5) therein is at least 10%, preferably at least 15%, more preferably at least 20%, at least 25%, at least 30%, or at least 40%.

14. A textile or garment piece having at least one graphene layer (5) prepared by the method according to any one of claims 1 to 11 and / or according to any one of claims 12 or 13, preferably on at least one carrier layer (16), said textile or garment piece preferably in the form of waterproof and / or water-repellent and / or breathable garment.

15. Use of the graphene layer (5) according to any one of the preceding claims, preferably on at least one carrier layer (16), as a semi-permeable membrane, particularly in the field of clothing or in textile applications in the technical field of providing a water barrier in electronic and / or mobile devices.

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