Coated porous media, method of manufacturing a coated porous media and the use of such coated porous media

Abstract

The present invention relates to a coated porous media comprising a porous media grafted with at least one compound according to Formula 1 or Formula 2: (1), (2) wherein the asterisk * designates a covalent bond with the porous media, wherein at least one of R1, R2, R3, R4, and R5 groups are different from a hydrogen atom, wherein R1, R2, R3, R4 and R5 groups are independently selected from nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl, polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree comprise at least one group selected from: nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, wherein R6 group is selected from vinylic terminated organo-silicon compounds, compounds with alkyl chains with at least 6 carbon atoms, preferably at least 10 carbon atoms, or vinylic terminated polar molecules, and wherein R7 group is either a hydrogen atom or a methyl group. The present invention further relates to a coated porous media, comprising a porous media grafted with at least one compound wherein the compound is a derivative of aniline or a co-polymer thereof. The present invention further relates to a method of manufacturing said coated porous media by chemical or electrochemical grafting.

Description

[0001] TITLE Coated porous media, method of manufacturing a coated porous media and the use of such coated porous media

[0002] TECHNICAL FIELD

[0003] The invention relates to a coated porous material. The invention further relates to a method of manufacturing such coated porous media. The invention further relates the use of this coated porous media, specifically to a fuel cell comprising this coated porous media.

[0004] BACKGROUND

[0005] Electrochemical energy systems such as fuel cells rely on porous materials that determines the performance of the device. In the field of electrochemical technologies, the cell design typically contains a multitude of porous, conductive layers. For example, in low temperature fuel cells, the porous gas diffusion electrode is comprised of three layers, namely (1) a gas diffusion layer (also called microporous substrate) which is typically made of carbon fibers and dip coated with a hydrophobic polymer like PTFE, (2) a microporous layer made of carbon black and a hydrophobic polymer like PTFE, and (3) a catalyst layer typically made of platinum supported on carbon nanoparticles and a ionomer (e.g. Nation). The role of these porous media is to distribute the reactant gases (oxygen in air), remove the reaction products (generated water), and conduct electrons and heat. To achieve the function of thermal and electrical conductivity, carbon-based porous substrates are widely used (typically made of carbon fibers and nanoparticles).

[0006] Pristine porous media typically can exhibit mildly hydrophobic properties; however, depending on specific conditions and types, they can also show a tendency to be hydrophilic. Depending on the final application, the wettability can be further tuned by coating of the material. In the context of hydrogen fuel cells, a limited hydrophobic or even hydrophilic character of the gas diffusion layer and microporous layer can lead to flooding of the porous material and catastrophic performance losses. During a flooding event the porous material becomes saturated with liquid water, limiting the effective transport reactant to the catalytic surface. On the other hand, on the membrane-catalyst interface, hydrophilic properties of the porous medium are desired, as this improves proton conductivity and membrane humidification. The challenge of porous media flooding has been tackled by applying hydrophobic polymeric coatings based on fluoropolymers such as polytetrafluoroethylene (PTFE) and fluoroethyelene propylene (FEP). The application of these polymers is carried out industrially with dip coating procedures, in which the solid substrate is immersed in a liquid dispersion containing the fluoropolymers, which is subsequently thermally treated to evaporate the liquid components and sinter the coating.

[0007] The catalyst layer is composed of a carbon support (or any other conductive material like inorganic particles or oxides) and an electrocatalyst (e.g. platinum group metals) that is kept together by incorporation of a binder material (e.g. Nation™ ionomer in polymer electrolyte fuel cells). The surface properties of the support and electrocatalyst determine the final properties of the material such as kinetic activity, mass transport, microstructure and interactions with the binder.

[0008] US10581088B2 described a gas diffusion layer for a fuel cell, made of a carbon substrate grafted with a diazonium aromatic group. The aromatic group itself is functionalized with fluorinated end-groups.

[0009] While this is functional, several challenges arise with the application of these coatings (e.g. durability, heterogeneity, maldistribution). The most notable challenge is that per- and polyfluoroalkyl substances are considered not friendly for the environment, and regulations to the use of these substances is becoming very strict.

[0010] Thus, there is a need for a method of manufacturing a coated porous material that does not involve the use of fluoropolymers, while retaining a similar or improved level of control over the water management (e.g. flooding prevention) within the porous material.

[0011] SUMMARY

[0012] It is an object of the present invention to provide an improved coated porous media.

[0013] It is a further object of the present invention to provide a coated porous media with suitable wettability for its application.

[0014] It is a further object of the present invention to provide a coated porous media with good water repellency. It is a further object of the present invention to provide an improved method of manufacturing for a coated porous media.

[0015] It is a further object of the present invention to provide a method of manufacturing for a coated porous media that does not require the use of fluoropolymers or fluorinated molecules.

[0016] It is an object of the present invention to provide an improved fuel cell.

[0017] It is a further object of the present invention to provide a fuel cell with improved fluid management.

[0018] The invention therefore relates in a first aspect to a coated porous material according to claim 1.

[0019] The invention relates in a second aspect to a coated porous material according to claim 4.

[0020] The invention further relates in a third aspect to a method of manufacturing of such coated porous media according to claim 11.

[0021] The invention further relates in a fourth aspect to a method of manufacturing of such coated porous media according to claim 12.

[0022] The invention further relates in a fifth aspect to a fuel cell comprising this coated porous media according to claim 25.

[0023] The invention further relates in a sixth aspect to uses of this coated porous media according to claims 26 and 27.

[0024] At least one of the above-mentioned objects is achieved by the present invention.

[0025] Embodiments of the coated porous media are applicable correspondingly to the method of manufacturing, the fuel cell and the use of the coated porous media according to the present invention.

[0026] The present invention relates i.a. to methods for functionalizing a wide range of porous materials used in electrochemical energy devices, such as carbon fibers, carbon particles and metals. The functionalization can be performed on single fibers or particles as a powder in solution or dispersion or can be performed after producing a layer of these materials.

[0027] Without wishing to be bound by the theory, the inventors believe that the coated porous media according to the present invention has a unique grafting pathway that provides hydrophobic properties throughout their entire 3D structure. The method of manufacturing the coated porous media according to the present invention involves the use of a diazonium salt to introduce radicals onto a separate vinylic functional end group with hydrophobic backbone and subsequently graft this vinylic-ended structure on top of a porous media substrate. This usage of diazonium salts to indirectly graft several functional coatings on top of substrates provides the unexpected benefits of a unique grafting pathway that allows for tuned wettability (hydrophobicity, hydrophilicity) throughout the entire 3D structure of an electrochemical cell.

[0028] The method provides coatings with long-term integrity of the carbon support and long-term flooding stability.

[0029] The method according to the present invention involves indirect grafting of diazonium, which enables accurately tuning of the wettability of various types of porous media (e.g. carbon fiber, carbon particles) and extends the library of molecules that can be grafted.

[0030] A wide range of functionalities can be introduced via the method according to the present invention, allowing to tune the wetting properties of the material from hydrophilic to hydrophobic. In particular, it enables the use of fluorine- free molecules with hydrophobic properties to enhance water repellency.

[0031] BRIEF DESCRIPTION OF DRAWINGS

[0032] The present invention is described hereinafter with reference to the accompanying drawings in which embodiments of the present invention are shown and in which like reference numbers indicate the same or similar elements.

[0033] Figure 1 shows an example of cyclic voltammetry onto a Freudenberg H15 at 50 mV / s in acetonitrile + 0.1 M Et4(NH4)+BF4-.

[0034] Figure 2 shows survey spectra of a) untreated and b)-d) electrografted materials (Freudenberg H15) for Examples 1-3.

[0035] Figure 3 shows elemental composition extracted from the survey spectra.

[0036] Figure 4 shows N 1s and Si 2p high resolution spectra before etching, Si 2p after etching and Si 2p peak area as a function of etching time; etching is performed at 1 keV with a monochromatic Ar+ ion gun within the XPS chamber. Figure 5 shows external contact angles of 2 pL water droplets and 5 pL ethanol-water mixture droplets on bare and modified substrates.

[0037] Figure 6 shows schematics of 3-electrodes cell set-up.

[0038] Figure 7 shows schematics of a flow-cell set-up.

[0039] Figure 8 shows electrochemical double-layer capacitance obtained in two different set-ups in HCI 0.5 M.

[0040] Figure 9 shows surface energy values with their components for untreated and electrografted glassy carbon.

[0041] Figure 10 shows polarization curves of the different GDLs at different operating conditions: a) Differential; b) Dry; c) Wet; d) Super-wet.

[0042] Figure 11 shows polarization curves of the different GDLs at different operating conditions: a) Differential; b) Dry; c) Wet; d) Super-wet.

[0043] Figure 12 shows polarization and HFR curves versus current density of the different GDLs at different operating conditions: a) Normal conditions; b) Humid conditions; c) Low-T normal conditions; d) Low-T humid conditions.

[0044] Figure 13 shows chemical grafting on a porous media in a schematic way.

[0045] Figure 14 shows thermogravimetric measurements for the grafting of an aniline derivative relative to the baseline 40 wt% Platinum on Vulcan.

[0046] Figure 15 shows XPS spectra of Platinum on Vulcan powders.

[0047] Figure 16 shows polarization curves measured under differential conditions (2 and 5 liters per minute of hydrogen and air respectively on the anode and cathode compartment) in a 5 cm2 single cell test bench at 80 degrees Celsius, 1 MPa compression, 100% relative humidity at 0.5 bar gauge pressure.

[0048] Figure 17 shows cyclic voltammetry of a redox probe, ferricyanide (1 mM) in KCI 1.0 M, at a scan rate of 100mV / s, on baseline and grafted materials.

[0049] Figure 18 shows XPS survey spectra of the compounds prepared after step 1 and step 2 and of the bare substrate.

[0050] Figure 19 shows external contact angles of 5pL water droplets of the bare substrate and of the substrate after step 2.

[0051] Figure 20 shows polarization and HFR curves versus current density of the different GDLs at different operating conditions: a) Normal conditions; b) Humid conditions; c) Low-T normal conditions; d) Low-T humid conditions. Figure 21 shows (a) TGA, (b) ^-potential, and (c) hydrodynamic radius measurements of grafted and ungrafted samples.

[0052] Figure 22 shows (a) XRD, and (b) XPS measurements and (c) grafted weight estimations of samples prepared with different precursor concentrations.

[0053] Figure 23 shows iR-corrected linear sweep voltammograms of grafted and ungrafted samples.

[0054] Figure 24 shows polarization and HFR curves of the samples prepared with different precursor concentrations.

[0055] Figure 25 shows the results of (a) Roughness factor, (b) proton conductance, and (c)-(d) oxygen mass transport resistance tests performed with samples prepared with different precursor concentrations.

[0056] Figure 26 shows polarization and HFR curves of the samples having different supports.

[0057] DESCRIPTION OF EMBODIMENTS

[0058] Coated porous media

[0059] As stated above, the invention relates in a first aspect to a coated porous media comprising a porous media grafted with at least one compound according to Formula 1 or Formula 2: wherein the asterisk * designates a covalent bond with the porous media, wherein at least one of R1, R2, R3, R4, and R5groups are different from a hydrogen atom, wherein R1, R2, R3, R4and R5groups are independently selected from nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl, polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree comprise at least one group selected from: nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, wherein R6group is selected from vinylic terminated organo-silicon compounds, compounds with alkyl chains with at least 6 carbon atoms, preferably at least 10 carbon atoms, or vinylic terminated polar molecules, wherein R7group is either a hydrogen atom or a methyl group.

[0060] The R6group can be selected according to the desired wetting properties to be achieved: from the family of vinylic terminated organo-silicon compounds or long alkyl chains for hydrophobicity, and from the family of vinylic terminated polar molecules (such as amines, amides, alcohols, thiols, aldehydes, ketones, carboxylic acids) for hydrophilicity. Preferably, R6group is selected from vinylic terminated organo-silicon compounds.

[0061] It is to be understood that any of R1, R2, R3, R4and R5may alternatively be another compound according to Formula I. This could result in the compound that is grafted to the porous media being an oligomer. More details on the reaction scheme can be found in the experimental section.

[0062] In an embodiment, R1, R2, R4, and R5are hydrogen, and R3is nitro.

[0063] In another embodiment, R2and R4are alkyl comprising amide according to -C(=O)NH-alkyl, preferably wherein said alkyl group is C10 to C20. In said embodiment, said compound is according to: In a second aspect, the present invention relates to a coated porous media, comprising a porous media grafted with at least one compound wherein the compound is a derivative of aniline or a co-polymer thereof, preferably wherein the compound is selected from the group consisting of sulfanilic acid, nitroaniline, chloroaniline, phenylenediamine (or p-phenylenediamine), toluidine (that includes o-toluidine, m-toluidine and p-toluidine), and aminobenzoic acid (or 4- aminobenzoic acid), 4-(1 H-lmidazol-1-yl)aniline. The structures of these compounds are given below.

[0064] (4-aminobenzoic acid), (4-(1 H-lmidazol-1-yl)aniline). Derivatives of aniline in the present context can be seen as aminosubstituted benzene rings possibly also carrying additional substitutions on the ortho, meta and / or para positions.

[0065] In an embodiment of this second aspect, the compound is selected from the group consisting of:

[0066] In an embodiment of the first or second aspect, the coated porous media is fluorine-free.

[0067] In a further embodiment of the first or second aspect, the coated porous media has a porosity of 20-99 %.

[0068] In a further embodiment of the first or second aspect, the coated porous media has a coating thickness of between 1 nm - 1 micron.

[0069] In a further embodiment of the first or second aspect, an external contact angle, denoted by the angle established on the porous media’s outer surface, is between 90 and 160 degrees, preferably between 110 and 160 degrees, more preferably between 130 and 160 degrees.

[0070] In a further embodiment of the first or second aspect, an external contact angle, denoted by the angle established on the porous media’s outer surface, is between 0 and 90 degrees, preferably between 0 and 50 degrees.

[0071] The external contact angle can be seen as a measure for a homogenous wetting resistance. A higher external contact angle relates to more hydrophobic properties, whereas a lower external contact angle relates to more hydrophilic properties.

[0072] In general, the choice of R-groups allows for tunability of properties for certain applications. For example, the coated porous media can be tuned to have a surface energy of below 30 mN / m for hydrophobic applications, and above 30 mN / m for hydrophilic applications. Method of manufacturing a coated porous media

[0073] The present invention also relates in the third aspect to a method of manufacturing a coated porous media according to the first or second aspect by chemical or electrochemical grafting, comprising: providing a porous media; immersing the porous media in a bath of a solution or dispersion comprising at least one monomer or polymer which can be radically grafted, at least one diazonium salt or a precursor thereof, and at least one solvent; grafting a polymer on a surface of the porous media to obtain a coated porous media.

[0074] The present invention further relates in the fourth aspect to a method of manufacturing a coated porous media according to the first or second aspect by chemical or electrochemical grafting, comprising: providing a bath of a solution or a dispersion comprising at least one diazonium salt of the compound according to Formula 1 or Formula 2, or a precursor thereof, and at least one solvent; reducing said at least one diazonium salt to a radical compound; providing a porous media and immersing said porous media in said bath; grafting said radical compound on a surface of said porous media to obtain a coated porous media or a precursor thereof; optionally, post-functionalizing said precursor of said coated porous media to obtain said coated porous media.

[0075] An example of a general reaction mechanism of the method according to the fourth aspect of the present disclosure could be as follows: X represents an R group, e.g., any of the R1, R2, R3, R4, and R5groups, and the X group may also be present on another C atom of the C6 ring. Y represents a molecule with which the precursor is post-functionalized, for example to introduce hydrophobic functionality. An example of such as a molecule having an alkylic chain, like octadecylamine (ODA).

[0076] In an embodiment according to a first aspect of the method, at least one monomer or polymer which can be radically grafted is a vinyl terminated organosilicon compound or a vinyl terminated hydrocarbon compound.

[0077] This embodiment relates to the manufacture of a coated porous media according to the first aspect.

[0078] In a further embodiment according to a first aspect of the method, the method is by electrochemical grafting, wherein the porous media is electrically conductive; wherein the solution or dispersion is an electrolyte solution or dispersion further comprises at least one supporting electrolyte; and wherein there is a potential difference applied to the bath prior to immersion of the porous media in the bath, said potential difference being generated by an electrochemical cell created between two electrodes immersed in said bath, the two electrodes being different from the porous media.

[0079] The supporting electrolyte can be for example an organic salt, such as (C2H4)4NH4+BF4-.

[0080] In a further embodiment according to a first aspect of the method, the organosilicon compound is selected from Allyltriisopropylsilane (CAS 24400-84-8) Acryloxymethyltrimethylsilane (CAS 67186-35-0) and Monomethacryloxypropyl terminated polydimethyl siloxane (CAS 146632-07-7), preferably wherein the organosilicon compound is Monomethacryloxypropyl terminated polydimethyl siloxane.

[0081] In a further embodiment according to a first aspect of the method, the hydrocarbon compound is a compound with a long alkyl chain, being for instance at least 6 carbon atoms, preferably at least 10 carbon atoms.

[0082] In a further embodiment according to a first aspect of the method, the voltage for the electrochemical grafting is between 0.5 and -1.0 V relative to an Ag7Ag reference electrode. In an embodiment according to the first or a second aspect of the method, the at least one monomer or polymer which can be radically grafted is a polar compound, preferably selected from acrylate, amine, alcohol, amide, keton, carboxylic acid, sulphonate, aldehyde, and cyanide. This embodiment relates to the manufacture of a coated porous media according to the second aspect.

[0083] In an embodiment according to a second aspect of the method, the method is by chemical grafting, wherein the solution or dispersion further comprises at least one reducing agent, preferably selected from ascorbic acid, hypophosphorous, sodium dithionite and iron (Fe2+).

[0084] It is noted that although a reducing agent is required for chemical grafting, the porous media itself can also serve as the reducing agent. In that case, it is not required that a reducing agent be present is the solution or dispersion.

[0085] In an embodiment according to the first or second aspect of the method, the porous media is selected from carbon, carbon fiber, metal, nobel metal, a surface containing reducible oxide, a graphite surface, a conductive or semiconductive organic surface, a surface of an alloy, a surface of one or more conventional conductive polymer(s), such as a surface based on pyrrole, on aniline, on thiophene, on EDOT, on acetylene or on polyaromatics, a surface of an intrinsic or doped semiconductor, and any combination of these compounds, preferably wherein the porous media is carbon fiber or carbon particles.

[0086] In a further embodiment according to the first or second aspect of the method, the porous media is a microporous material, preferably carbon particles, preferably with a pore size of between 0.5 mm and 100 nm.

[0087] In a further embodiment according to the first or second aspect of the method, the porous media is a catalyst material, preferably platinum supported on a porous substrate, preferably wherein the porous substrate is selected from the group of carbon, or other conductive materials.

[0088] Carbon in this context includes Vulcan carbon, Ketjen black, Acetylene black, Graphitized carbon, Graphite, Graphene, and Carbon nanotubes. Suitable other conductive materials are metals, such as stainless steel or titanium.

[0089] In a further embodiment according to the first or second aspect of the method, the solvent or dispersion is an organic solvent or water, preferably the solvent is a low surface tension solvent, more preferably the solvent is acetonitrile. In a further embodiment according to the first or second aspect of the method, the diazonium salt is a diazonium salt or a mixture of diazonium salts of generic formula R' — N2+, X~, wherein X~ is a counterion and R' comprises an organic or mineral group selected from the group consisting of nitro, fluoro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, diazonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree include a group selected from the group consisting of: nitro, fluoro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, diazonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, preferably nitrobenzene diazonium tetrafluoroborate.

[0090] The diazonium salt may be soluble in the solvent comprised in the solution or dispersion.

[0091] The concentration of the diazonium salt is the solution or dispersion can for example be between 10-4and 1 mol / l.

[0092] The at least one monomer or polymer which can be radically grafted is preferably used in excess, e.g. 10 fold excess compared to stoichiometric amount.

[0093] The solution or dispersion may for instance be room temperature upon immersion of the porous media into the solution or dispersion, such as having a temperature of between 15 and 30 °C.

[0094] The porous media may optionally be pretreated prior to immersion into the solution or dispersion. Suitable pretreatments could include thermal treatment, plasma treatment, washing, and / or sonication. For instance, the porous media is subjected to thermal pretreatment prior to immersion into the solution or dispersion, preferably wherein the thermal pretreatment comprises of the porous media to a temperature of between 200-500 °C for a duration of between 1-48 hours. The effect of such pretreatment steps is that it improves the wettability in aqueous media.

[0095] The immersion and grafting may possibly take place at an underpressure (e.g. vacuum). The immersion and grafting may possibly take place in a convectively or forced-pressure driven system. The porous media may possibly be a dispersion of solid particles (slurry).

[0096] Use of the coated porous media

[0097] The present invention also relates to a fuel cell comprising the coated porous media according to the present invention.

[0098] The present invention also relates to the use of the coated porous media according to the present invention for an electrochemical energy system, preferably wherein the electrochemical energy system is a multiphase electrochemical energy system, preferably selected from a polymer electrolyte membrane fuel cell, a polymer electroyte membrane water electrolyzer, an alkaline exchange membrane fuel cell, an alkaline exchange membrane water electrolyzer, a reversible fuel cell system, or a carbon dioxide electrolyzer.

[0099] Other potential uses of the coated porous media according to the present invention include hydrogen-bromine redox flow battery, an iron-air battery, or other redox flow battery chemistries.

[0100] The present invention also relates to the use of the coated porous media according to the present invention as protective coating in textiles, automotive, aerospace or maritime applications, electronics, kitchenware, sanitation and plumbing, oil and gas pipelines, solar panels, medical equipment, constructions and food processing.

[0101] The coated porous media can be tuned to suit the desired application. For instance, a textile is a non-conductive surface while the electrografting requires a conductive coating, so chemical grafting can be used to manufacture the coated porous media for such an application.

[0102] The table 1 below indicates possible uses for the coated porous media according to the present invention, indicating industry type, specific application, type of porous medica, and whether electrochemical or chemical grafting can be used for the manufacturing of the coated porous media.

[0103] Table 1 : Possible uses for the coated porous media according to the present invention

[0104] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof.

[0105] The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims.

[0106] EXAMPLES

[0107] The present invention is further elucidated based on the Examples below which are illustrative only and not considered limiting to the present invention.

[0108] Methods

[0109] Electrochemical modification (grafting)

[0110] For all electrochemical examples, the electrochemical modification has been performed with a BioLogic potentiostat in a standard three-electrodes cell set-up: a Pt mesh (Pt, 99%, 2 cm diameter) as counter electrode, a silver-silver nitrate electrode (Ag / AgNO3 in 0.1 M Et4NH4+ BF4- in acetonitrile) as reference, and a pristine gas diffusion layer (Freudenberg H15) as working electrode. An organic solvent (acetonitrile) with 0.1 M of a supporting electrolyte (tetraethylammoniumtetrafluoroborate, Et4NH4+ BF4-) has been used as electrolyte, in order to maximise the electrode-electrolyte wetted interface.

[0111] For the chemical examples, a diazonium salts is firstly formed in-situ by dissolving sodium nitrite in a 1.0 M HCI solution, and cooling it down to -1 °C . Afterwards, the aniline derivative (e.g. 5-aminoisophthalic acid) is added and to the reaction mixture and magnetically stirred for one hour. Once the diazonium salt is formed, an untreated electrode is immersed in the solution and a reducing agent (e.g. ascorbic acid) is added, in order to generate the aryl radical that grafts onto the electrode surface. After this step, the substituent groups are attached to the carbon paper and can undergo further functionalization. In the specific case, an amidation reaction is performed, in order to functionalize the electrode with long alkylic chains.

[0112] Chemical modification (grafting)

[0113] For all chemical examples, typically 100 mg of 20 or 40% Platinum on carbon was used, specifically 40% Platinum on Vulcan dispersed in 10 mL of 0.5M HCI. To this dispersion 1 mmol of the aniline derivative (e.g. sulfanilic acid) was added under stirring. After dissolution of the aniline derivative one equivalent of sodium nitrite was predissolved in 10 mL 0.5M HCI is added, still under stirring. The dispersion was kept stirring like this overnight at room temperature and atmospheric pressure. After the reaction was stopped by ultrafiltration of the dispersion by washing it with ethanol (100 mL) and distilled water until the pH of the effluent was neutralized. After this step the grafted Platinum on Vulcan was dried in a vacuum oven at 60 degrees Celsius.

[0114] A schematic representation of chemical grafting is given in Figure 13. From the aniline derivative, diazonium is created in situ. For example following the following mechanism:

[0115] To probe the fluid-repellency of the newly developed material, external contact angle measurements have been carried out with a DataPhysics Optical Contact Angle OCA30 goniometer. The sessile-drop method has been employed and 2 pL droplets were used for water, while 5 pL droplets were used for the 20 wt.% ethanol in water mixture, due to its lower surface tension and its tendency to crawl up the needle. Water-ethanol mixture was used because a lower surface tension solvent enables assessing superhydrophobic surfaces that cannot be quantitatively assessed with water. Double layer capacitance measurements

[0116] Electrochemical double-layer capacitance (EDLC) measurements have been performed in two different set-ups (3-electrodes cell and flow cell) as proxy of electrode wettability. Electrodes with higher wettability show higher capacitance because of the higher interfacial contact between the electrode and the electrolyte; on the contrary, it is expected that electrodes with lower wettability show low capacitance. This way, a qualitative evaluation can be made on the wettability of the different electrodes. A BioLogic Potentiostat has been used in both cases.

[0117] The materials capacitance in the 3-electrodes cell set-up (shown in Figure 6) has been measured via cyclic voltammetry with a 0.5 M HCI electrolyte, by cycling the potential for 5 times from 0.0 V to 0.4 V at varying scan rates (10-25-50- 100-200-500 mV / s). In this steady set-up, the aqueous electrolyte poorly wets the naturally hydrophobic working electrode, bringing to quite low capacitance values, even though in accordance with the expected wetting properties of the materials.

[0118] In order to confirm the obtained values, the same parameter has been measured in a flow-cell set-up (shown in Figure 7), where the electrolyte is forced through the pores of the electrodes with a pump with a 10 mL / min flow rate. This way, a higher contact of the electrolyte with the electrode is ensured and a more accurate result is expected. Again, cyclic voltammetry with a 0.5 M HCI electrolyte was used, but cycling the potential for 5 times at varying scan rates (10-25-50-100-200-500 mV / s) from -0.1 V to 0.1 V.

[0119] All measurements have been corrected for solution resistance by automatic iR compensation (solution resistance extracted at 100 kHz and 20 mV sinus amplitude, 85% compensation applied).

[0120] Then, the current values have been extracted for anodic and cathodic sweep, and the capacitance of the electrodes was calculated by the following equation: dV i = EDLC — dt where i is the average current in absolute value (mA) at mid-voltage value of the scan bounds, EDLC is the electrochemical double-layer capacitance (F) and dV / dt is the scan rate.

[0121] Calculating the surface energy of a solid material allows to predict how it would interact with any liquid of known physicochemical properties. It basically determines the interaction of a solid with a fluid and provides a complimentary metric to contact angle measurements. A high surface energy means that the interfaces between solids and air are not thermodynamically favourable. Since liquid wetting eliminates solid / air interfaces in favour of solid / liquid interfaces, high surface energy solids wet well by liquids. Conversely, low surface energy solids are very poorly wet by most I iquids[6] . Thus, in order to gain more insight into the wetting properties of the prepared coatings, this parameter has also been experimentally determined. The measurement resulted to be complex on a porous material, therefore, the modifications (following the same protocol) and the measurements have been carried out on glassy carbon (1x1 cm2 pieces). Even though the characteristics of glassy carbon are different from the ones of carbon fibres papers, the obtained value can be representative of the relative changes occurred on the carbon surface after modification.

[0122] By using the Owens-Wendt theory, which accounts for non-site specific and site specific interactions between solid surfaces and liquids, it is possible to calculate the solid surface energy. Surface energies of the solid-vapour YSV and liquid-vapour YLV interphases consist of two components: the dispersive one, which accounts for van der Waals and other non-site specific interactions, and the polar one, which accounts for dipole-dipole, dipole-induced dipole, hydrogen bonding, and other site-specific interactions. d i V Ysv = Ysv + Ysv d i P YLV = YLV + YLV

[0123] Combining Good-Fowkes’ equation (1) with Young’s equation (2)

[0124] YSL = Ysv + YLV ~ 2( J Ysv YLV + JYSVYLV) (1) yLVcos0 = ysv- YSL (2) yields the linear relation (3) where 0 is the contact angle between liquid and solid. The two unknown components of the solid surface energy YdSV and YpSV in equation (3) can be determined from measured contact angle values of different liquids with known values of surface tension components.

[0125] Single cell fuel cell tests

[0126] Performance of the coated porous media was tested in singe cell fuel cell tests. Fuel cell tests were conducted in a 5 cm2 active area single cell (Baltic) with parallel graphite flow fields.

[0127] Moreover, the newly developed materials have only been tested at the cathode side, while at the anode side a 10 wt. % PTFE dip-coated electrode was kept as a baseline. All tested material did not have an MPL. Same as for the ex-situ characterization presented above, the three modifications have been compared with untreated FH15 and with PTFE- coated FH15.

[0128] Initial cell conditioning is performed by stepping the voltage under hydrogen and air at Tcell = 80 °C, pabs=1.5 bar, and 100% relative humidity (RH) in the following sequence: 0.6 V for 1 minute, 0.3 V for 1 minute and OCV for 1 minute, the sequence is repeated twenty times. Differential-flow and laminar-flow H2 / air polarization curves are recorded in potentiostatic mode, by stepping the voltage from OCV to 0.35 V in steps of 50 mV. Each point is held for 1 minute and a datapoint is taken every 5 seconds, the shown data are an average of the 12 points and the error bars are the standard deviation of each dataset. The testing conditions are summarised in Table 2, using Freudenberg material H15 as substrate for modifications, and they have been calculated in order to simulate operative conditions Table 2: conditions for polarization curves

[0129] The best performing modification was carried out on a different carbon fibers paper substrate, the Toray RGP H060, and tested at the conditions laid down in Table 3.

[0130] Table 3: conditions for second set of polarization curves

[0131] X-Ray Photoelectron Spectroscopy

[0132] To resolve the chemical composition at the electrodes surface, X-Ray Photoelectron Spectroscopy (XPS) has been employed. A Thermo Scientific K-alpha X-ray photoelectron spectrometer, equipped with a monochromatic small-spot X-ray source and a 180° double focusing hemispherical analyzer with a 128-channel detector, has been used. An aluminum anode (Al Ka = 1486.6 eV) source operating at 72 W and a spot size of 400 pm have been used to obtain the spectra. Survey scans have been measured at a constant pass energy of 100 eV. Examples of electrochemical grafting

[0133] Three different molecules have been chosen as the monomer or polymer which can be radically grafted and used for grafting in these examples, aiming to evaluate the behaviours of the different chemistries in the electrografting procedure and their effect on the wetting properties. In order to avoid fluorine-containing materials, water-repellent organic silicon-based chemistries have been investigated.

[0134] Example 1 (modification 1)

[0135] Example 1 was performed as described above, using

[0136] Allyltriisopropylsilane (CAS 24400-84-8):

[0137] Example 2 (modification 2)

[0138] Example 2 was performed as described above, using

[0139] Acryloxymethyltrimethylsilane (CAS 67186-35-0):

[0140] Example 3 (modification 3) Example 3 was performed as described above, using

[0141] Monomethacryloxypropyl terminated polydimethyl siloxane (CAS 146632-07-7):

[0142] This is also known as PDMS with methacryloxy-termination.

[0143] Results

[0144] A first indication of the successful coating application is already given by the electrografting footprint (Figure 1), which resulted to be the same for all three modifications. On the cyclic voltammograms a decreasing current is observed over the 15 cycles, which suggests that the substrate’s surface is being grafted and therefore saturated.

[0145] X-Ray Photoelectron Spectroscopy

[0146] Survey spectra of untreated FH15 and electrografted material are seen in Figure 2, and the resulting elemental distribution in Figure 3 shows quantitative silicon signals of the treated materials, which are not present in the bare FH15, together with higher contents of nitrogen and oxygen. In particular, as expected from the chosen molecules, in the case of Example 1 and Example 2 the oxygen content corresponds to twice the nitrogen content, and only a low silicon content is detected. In the case of Example 3, the oxygen content is even higher due to the different nature of the grafted siloxane.

[0147] In all three Examples, the obtained results agree with the expected ones, confirming a successful surface modification.

[0148] Figure 4 show N 1s and Si 2p high resolution spectra before etching, Si 2p after etching and Si 2p peak area as a function of etching time. The etching is performed at 1 keV with a monochromatic Ar+ ion gun within the XPS chamber. From the results it can be concluded that covalent bonds (which are more stable) have been formed with the carbon substrate. The etching shows that the coatings are in fact really thin (in the range of a few nanometers). Compared to the state-of-the-art materials, i.e., a) ‘Bare FH15’ (PTFE coated Gas Diffusion Layers (GDLs)), there is one core difference: the examples Mod 1 , Mod 2 and Mod 3 have covalently grafted bonds while the Bare FH15 is sustained by weak interactions.

[0149] Contact anole

[0150] All novel materials have been compared with both an untreated Freudenberg H15 and an hydrophobized electrode treated with a standard procedure (PTFE dip-coating with a final PTFE content of 10 wt.%).

[0151] The bare FH15 is intrinsically highly hydrophobic due to its roughness (i.e. Cassie Baxter state): it shows, before any treatment, high water contact angles (around 130°). To gain additional insight, the measurement has been carried out with a lower surface tension liquid (20 wt.% ethanol in water). A lower surface tension liquid would more favourably wet solid surfaces, therefore, it can give clearer information on the wettability of different surfaces with different surface energies when compared to water.

[0152] As shown in Figure 5, for the water contact angles similar results among the samples were obtained. While the bare FH15 has a contact angle of 130.1 °, Modification 1 and 2 show values of 131.5 ° and 131.8 °, which are still within the error interval. In the case of Modification 3 a 10 ° increase was observed, while in the case of the PTFE dip-coated a 20 ° increase, which are more noticeable differences, but not as significant as when measured with the water-ethanol mixture. For instance, for Modification 1 and 2 the mixture contact angles are increased by 33.9 ° and by 46.8 ° when compared to the bare FH15, even though larger error bars are obtained due to uneven distribution of the grafted molecules. Modification 3 and PTFE dip- coated sample show, at the same time, very similar repellency with contact angle values of 139.8 ° and 133.7 °, and smaller error bars.

[0153] Electrochemical double-layer capacitance

[0154] The results are reported in Figure 8 where, again, the electrografted materials are compared to the untreated electrode and the PTFE dip-coated one. When comparing to the untreated material, lower EDLC values are observed for all the treated materials. In particular, as already observed via contact angle measurements, Modification 1 and 2 do not show significant differences and are comparable to the bare FH15, while Modification 3 is comparable to the PTFE dip-coated electrode, with capacitance values around 20 % lower in the case of the 3-electrodes cell set-up, and 80% lower in the case of the flow-cell set-up. These results validate the significantly higher hydrophobicity of the modification 3. Surface Energy

[0155] For these measurements, the used test liquids and their surface tension values are listed in Table 4-1 and the measured contact angles on the unmodified and modified glassy carbon are listed in Table 4-2. Table 4-1 . Used test fluids and their surface tension values with their components.

[0156] Table 4-2. Contact angles against 5 pL droplets of test fluids.

[0157] The obtained surface energy values with their components are showed in Figure 9, where it is possible to observe that the solid surface energy of the glassy carbon is decreased by all modifications, in particular, by Modification 3. Moreover, while for the glassy carbon the polar component is predominant, the dispersive component is predominant for the three modifications. A solid material with higher polar component will interact better with polar liquids. On the contrary, a solid material with higher dispersive component interacts better with non-polar liquids. This explains why, being the water a polar liquid, wets better the unmodified glassy carbon and less the modified samples. Therefore, the modified surfaces show lower wettability and higher hydrophobicity.

[0158] The results, acquired according to the conditions of Table 2, show that, at 80°C - Figure 10a) and 10c) - the electrografted materials perform equal if not slightly better than the baselines (untreated material and PTFE dip-coated). In particular, the best performing electrografted material (Modification 3) was tested and compared to the baselines at 50°C and showed improved performances.

[0159] The results, acquired according to the conditions of Table 3, wherein the electrografted material was only compared to the PTFE dip-coated material, are shown in Figure 11. The results show again that, while at 80°C the two materials have comparable performances, at 50°C the PDMS electrografted material shows improvements. This may be due to the fact that the electrografted material has lower electrical and thermal resistance and its porous structure is more open when compared to the PTFE dip-coated material.

[0160] Figure 12 a)-d) show differential-flow H2 / Air (0.5 / 5 nlpm) polarization curves of cell voltage and high-frequency resistance (HFR) curves of single cells with, respectively, PFTE dip-coated (considered the baseline), Modification 1 (Mod 1), Modification 2 (Mod 2) or Modification 3 (Mod 3) electrografted material. In a), normal conditions were used (Tcell = 80 °C, RH = 100 %, pabs = 150 kPa), in b) humid conditions (Tcell = 80 °C, RH = 120 %, pabs = 150 kPa), in c) low-temperature normal conditions (Tcell = 50 °C, RH = 100 %, pabs = 150 kPa), and in d) low-temperature humid conditions (Tcell = 50 °C, RH = 120 %, pabs = 150 kPa).

[0161] From the results in Figure 12 it can be concluded that there is a correlation with temperature. Whereas the Modification 1 and Modification 2 materials do not show any performance improvement in comparison to the state-of-the-art (PTFE dip-coated), the Modification 3 material seems to show improvements when operating at low temperatures. Theoretical reaction mechanism

[0162] Without wishing to be bound by theory, the inventors believe that step

[0163] 1 of the reaction taking place of the diazonium salt being grafted to the porous media is, in an example, as follows:

[0164] Results

[0165] Figure 14: Thermogravimetric measurements reveal that relative to the baseline 40 wt% Platinum on Vulcan the grafting of the aniline derivatives is successful to different extents. The sulfanilic acid, nitro aniline and phenylene diamine appear to graft in greater quantity relative to the 4-(1 H-lmidazol-1-yl)aniline (also called ‘Pt / C-lmid’. Where phenylene diamine appears to graft the most, gravimetrically when compared to the other molecules

[0166] Figure 15: XPS spectra of Platinum on Vulcan powders subjected to the conditions of the grafting reaction as described before. The presence of the characteristic bands belonging to the respective functional groups of the molecules that were used as grafting agents indicates successful grafting in 3 out of 4 cases, where the spectrum of the Pt / C-lmid does not show the expected bands. This is also supported by the fact that the TGA results also indicate a much lower amount of grafted material for this molecule. The other three molecules seem to graft successfully onto the Platinum on Vulcan.

[0167] Figure 16: Polarization curves measured under differential conditions (2 and 5 liters per minute of hydrogen and air respectively on the anode and cathode compartment) in a 5 cm2 single cell test bench at 80 degrees Celsius, 1 MPa compression, 100% relative humidity at 0.5 bar gauge pressure. The results show that apart from the phenylenediamine and the sulfanilic acid grafted substrates the nitroaniline and Pt / C-lmid sample perform equal if not better than the baseline material. It is likely that further optimization in the grafting conditions of the two ill- performing samples could also increase their performance. This result overall shows that grafting of these particles works and can help improve the properties of the cathode catalyst layer of a proton exchange membrane fuel cell.

[0168] An example of a reaction mechanism for chemical grafting of diazonium salt and post-functionalization for introduction of a hydrophobic functionality (alkylic chain) is as follows:

[0169] STEP 1 - In-situ formation and reduction of diazonium salt Confirmation of the surface modification was found with an Iron redox probe, as shown in Figure 17. It shows that, while for the untreated and PTFE-dip- coated electrodes it is possible to observe the oxidation and reduction peaks related to the redox reaction of the iron specie, the peaks are no longer observed in the case of the grafted material. This shows that the surface of the electrode has been successfully modified, and that the organic layer formed around the fibers behaves as barrier for the electron transfer, fully inhibiting the redox reaction of the iron specie.

[0170] The XPS survey spectra for elemental composition determination as shown in Figure 18 of the compounds obtained after the above-shown respective steps 1 and 2 are compared with that of the bare substrate (untreated FH15). It shows that, when comparing the spectra of the bare substrate and of the substrate after step 1 (addition of carboxylic groups onto the surface), the oxygen content is higher for the modified electrode, confirming the successfulness of the grafting procedure. When comparing the spectra of the substrate after step 1 and of the substrate after step 2, instead, it can be observed that the oxygen content is lower for the substrate after step 2, as could be expected from a successful amidation reaction (as it consists of a condensation reaction).

[0171] Figure 19 shows the external contact angle of 5 pL water droplet on the surface of a bare substrate (untreated FH 15) and of a coated porous media (FH 15) obtained after the above-shown step 2. It shows that the water contact angle (CA) can be increased up to a value higher compared to the water contact angle of the bare substrate: 139 ° and 131 °, respectively. Hence, chemically grafting the porous media with the method as shown above can provide coated porous media with increased hydrophobicity. These results are in line as found for the electrochemical grafted examples, as shown in Figure 5.

[0172] Figure 20 a)-d) show differential-flow H2 / Air (0.5 / 5 nlpm) polarization curves of cell voltage and high-frequency resistance (HFR) curves of single cells with, respectively, PFTE dip-coated material (“PTFE”) and with octadecylamine (ODA) postfunctionalized chemically grafted material (“C18"). In a), normal conditions were used (Tcell = 80 °C, RH = 100 %, pabs= 150 kPa), in b) humid conditions (Tcell = 80 °C, RH = 120 %, pabs = 150 kPa), in c) low-temperature normal conditions (Tcell = 50 °C, RH = 100 %, pabs = 150 kPa), and in d) low-temperature humid conditions (Tcell = 50 °C, RH = 120 %, pabs = 150 kPa). From the results shown in Figure 20 it can be concluded that the chemically grafted material, at low temperatures (such as 50 °C), performs better than the state-of the art material (dip-coated with 10 wt % PTFE).

[0173] Acid-grafted Pt / Vulcan catalysts

[0174] The effect of grafting catalyst particles with a compound according to the first or second aspect of the present disclosure was also investigated. Sulfonic acid-grafted 40% Pt / Vulcan catalysts were prepared according to the following method, which is in accordance with method path 1 shown above:

[0175] Thermo-gravimetric analysis (TGA), ^-potential measurements and x- ray photoelectron spectroscopy (XPS) indicate the presence of grafted sulfonic acid moieties (Figure 21 and 22).

[0176] In Figure 21(a), TGA in N2 of grafted and ungrafted 40% Pt / V are shown. Figure 21 (b) shows ^-potential measurement of the same powders in water and Figure 21 (c) shows the hydrodynamic radius measured with dynamic light scattering.

[0177] Amine concentration influences grafting degree

[0178] The X-ray diffraction measurements of Figure 22(a) show that grafting has no clear influence on Pt particle size; the XPS spectra as a function of precursor concentration of Figure 22(b) show a correlation with -SO3H peak intensity; and Figure 22(c) shows the grafted weight estimation based on TGA residual in O2.

[0179] Intrinsic kinetics Thin-film ORR-RDE measurements are performed and the results (Figure 23) show that the grafted catalyst boasts slightly lower catalytic activity. This is also seen in Table 1 which shows the electrochemical surface area (ECSA), mass activity (lm) and specific activity (ls). The slightly lower mass activity of the grafted compared to the ungrafted catalyst indicates a small negative effect of the grafting procedure on the catalytic activity.

[0180] Table 1. ECSA, mass activity (lm) and specific activity (ls) Measured at 1600 RPM in 0.1 M HCIO4, mass transport corrected.

[0181] Single cell performance

[0182] The grafted catalysts with different precursor concentrations (low - medium - high) were incorporated into a membrane electrode assembly (MEA) using a low ionomer-to-carbon ratio (l / C) according to the scheme below. Figure 24(a) and (b) show a clear difference in performance in the ohmic and mass transport limited regime vs. the ungrafted catalyst and performance as function of relative humidity: in (a), the H2 / air polarization curve and corresponding high frequency resistance (RHF) show the positive influence of the grafting on overall performance at low l / C ratio, and in (b), the H2 / Air polarization curve show the influence of relative humidity on the catalyst grafted with a high precursor concentration.

[0183] The marked difference in proton conductivity seems to be the performance determining factor, although the O2transport resistance is also impacted (see Figure 25(a)-(d)): in (a), the Roughness factor (Rf) as a function of relative humidity and precursor concentration reveal higher retainment of active surface area at lower humidities for grafted samples, in (b), the proton conductance as a function of relative humidity and precursor concentration show a significant difference between grafted and ungrafted samples, in (c), the oxygen mass transport resistance (Ro*al) based on Baker’s method separated in pressure dependent (RQ2) and independent (RQ2) contributions show the most-grafted sample has the lowest transport resistances, and in (d), the Ro*alas a function of the limiting current show a plateau for the highest precursor concentration, indicating a high catalyst layer water saturation possibly owed to the higher intrinsic wettability.

[0184] Support influence

[0185] The influence of the support on the single cell performance was investigated as well. Figure 26 shows H2 / air polarization curves of 40% Pt on Vulcan and Ketjenblack (KB) with l / C = 0.1 , ungrafted vs. grafted. Form these results it can be concluded that the grafting procedure needs to be tuned for different carbon supports. One could think about surface area normalized reactant concentrations or pretreatment / activation of the carbon material. It also shows that specifically Ketjenblack, which is a high surface area support, likely requires a higher degree of proton conductivity as a result of its morphological difference compared to Vulcan.

[0186] CLAUSES

[0187] 1. Coated porous media comprising a porous media grafted with at least one compound according to Formula 1 : wherein the asterisk * designates a carbon atom with no hydrogen and no R' group, with i=1 to 6, and covalently bonded to the porous media, wherein at least one of R1, R2, R3, R4, and R5groups are different from a hydrogen atom, wherein R1, R2, R3, R4and R5groups are independently selected from nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl, polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree comprise at least one group selected from: nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, wherein R6group is selected from vinylic terminated organo-silicon compounds, compounds with alkyl chains with at least 6 carbon atoms, preferably at least 10 carbon atoms, or vinylic terminated polar molecules, wherein R7group is either a hydrogen atom or a methyl group.

[0188] 2. Coated porous media according to clause 1 , wherein R1, R2, R4, and R5are hydrogen, and R3is nitro.

[0189] 3. Coated porous media, comprising a porous media grafted with at least one compound wherein the compound is a derivative of aniline or a co-polymer thereof, preferably wherein the compound is selected from the group consisting of sulfanilic acid, nitroaniline, chloroaniline, phenylenediamine, toluidine, and aminobenzoic acid, 4-(1 H-lmidazol-1-yl)aniline.

[0190] 4. Coated porous media according to clause 3, wherein the compound is selected from the group consisting of:

[0191] 5. Coated porous media according to any of the preceding clauses, wherein the coated porous media is fluorine-free.

[0192] 6. Coated porous media according to any of the preceding clauses, wherein the coated porous media has a porosity of 20-99 %. 7. Coated porous media according to any of the preceding clauses, wherein the coated porous media has a coating thickness of between 1 nm - 1 micron.

[0193] 8. Coated porous media according to any of the preceding clauses, wherein the external contact angle, denoted by the angle established on the porous media’s outer surface, is between 90 and 160 degrees, preferably between 110 and 160 degrees, more preferably between 130 and 160 degrees.

[0194] 9. Coated porous media according to any of clauses 3-7, wherein the external contact angle, denoted by the angle established on the porous media’s outer surface, is between 0 and 90 degrees, preferably between 0 and 50 degrees.

[0195] 10. Method of manufacturing a coated porous media according to any of clauses 1-9 by chemical or electrochemical grafting, comprising: providing a porous media; immersing the porous media in a bath of an solution or dispersion comprising at least one monomer or polymer which can be radically grafted, at least one diazonium salt or a precursor thereof, and at least one solvent; grating a polymer on a surface of the porous media to obtain a coated porous media.

[0196] 11. Method according to clause 10, wherein the at least one monomer or polymer which can be radically grafted is a vinyl terminated organosilicon compound or a vinyl terminated hydrocarbon compound.

[0197] 12. Method according to clause 11 by electrochemical grafting, wherein the porous media is electrically conductive; wherein the solution or dispersion is an electrolyte solution further comprises at least one supporting electrolyte; and wherein there is a potential difference applied to the bath prior to immersion of the porous media in the bath, said potential difference being generated by an electrochemical cell created between two electrodes immersed in said bath, the two electrodes being different from the porous media. 13. Method according to any one of clauses 11-12, wherein the organosilicon compound is selected from Allyltriisopropylsilane (CAS 24400-84-8) Acryloxymethyltrimethylsilane (CAS 67186-35-0) and Monomethacryloxypropyl terminated polydimethyl siloxane (CAS 146632-07-7), preferably wherein the organosilicon compound is Monomethacryloxypropyl terminated polydimethyl siloxane.

[0198] 14. Method according to any one of clauses 12-13, wherein the voltage for the electrochemical grafting is between 0.5 and -1.0 V relative to an Ag+ / Ag reference electrode.

[0199] 15. Method according to clause 10, wherein the at least one monomer or polymer which can be radically grafted is a polar compound, preferably selected from acrylate, amine, alcohol, amide, keton, carboxylic acid, sulphonate, aldehyde, and cyanide.

[0200] 16. Method according to clause 10, 11 or 15 by chemical grafting, wherein the solution or dispersion further comprises at least one reducing agent, preferably selected from ascorbic acid, hypophosphorous, sodium dithionite and iron (Fe2+).

[0201] 17. Method according to any one of clauses 10-16, wherein the porous media is selected from carbon, carbon fiber, metal, nobel metal, a surface containing reducible oxide, a graphite surface, a conductive or semiconductive organic surface, a surface of an alloy, a surface of one or more conventional conductive polymer(s), such as a surface based on pyrrole, on aniline, on thiophene, on EDOT, on acetylene or on polyaromatics, a surface of an intrinsic or doped semiconductor, and any combination of these compounds, preferably wherein the porous media is carbon fiber or carbon particles.

[0202] 18. Method according to any one of clauses 10-16, wherein the porous media is a microporous material, preferably carbon particles, preferably with a pore size of between 0.5 mm and 100 nm. 19. Method according to any one of clauses 10-16, wherein the porous media is a catalyst material, preferably platinum supported on a porous substrate, preferably wherein the porous substrate is selected from the group of carbon, or other conductive materials.

[0203] 20. Method according to any one of clauses 10-19, wherein the diazonium salt is a diazonium salt or a mixture of diazonium salts of generic formula R' — N2+, X~, wherein X~ is a counterion and R' comprises an organic or mineral group selected from the group consisting of nitro, fluoro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, diazonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree include a group selected from the group consisting of: nitro, fluoro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, diazonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, preferably nitrobenzene diazonium tetrafluoroborate.

[0204] 21. Method according to any one of clauses 10-20, wherein the immersion and grafting takes place at an underpressure, or in a convectively or forced-pressure driven system.

[0205] 22. Method according to any one of clauses 10-21 , wherein the porous media is a dispersion of solid particles.

[0206] 23. Fuel cell comprising the coated porous media according to any of clauses 1-9.

[0207] 24. Use of a coated porous media according to any of clauses 1-9 for an electrochemical energy system, preferably wherein the electrochemical energy system is a multiphase electrochemical energy system, preferably selected from a polymer electrolyte membrane fuel cell, a polymer electroyte membrane water electrolyzer, an alkaline exchange membrane fuel cell, an alkaline exchange membrane water electrolyzer, a reversible fuel cell system, a carbon dioxide electrolyzer, 25. Use of a coated porous media according to any of clauses 1-9 as protective coating in textiles, automotive, aerospace or maritime applications, electronics, kitchenware, sanitation and plumbing, oil and gas pipelines, solar panels, medical equipment, constructions and food processing.

Claims

rising a porous media grafted with at least one compound according to Formula 1 or Formula 2:(1) , (2) wherein the asterisk * designates a covalent bond with the porous media, wherein at least one of R1, R2, R3, R4, and R5groups are different from a hydrogen atom, wherein R1, R2, R3, R4and R5groups are independently selected from hydrogen, nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl, polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree comprise at least one group selected from: nitro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, wherein R6group is selected from vinylic terminated organo-silicon compounds, compounds with alkyl chains with at least 6 carbon atoms, preferably at least 10 carbon atoms, or vinylic terminated polar molecules, wherein R7group is either a hydrogen atom or a methyl group.

2. Coated porous media according to claim 1 , wherein R1, R2, R4, and R5are hydrogen, and R3is nitro.

3. Coated porous media according to claim 1 , wherein R2and R4are alkyl comprising amide according to -C(=O)NH-alkyl, preferably wherein said alkyl group is at least C10, more preferably C10 to C20.

4. Coated porous media, comprising a porous media grafted with at least one compound wherein the compound is a derivative of aniline or a co-polymer thereof, preferably wherein the compound is selected from the group consisting of sulfanilic acid, nitroaniline, chloroaniline, phenylenediamine, toluidine, and aminobenzoic acid, 4-(1 H-lmidazol-1-yl)aniline.

5. Coated porous media according to claim 4, wherein the compound is selected from the group consisting of:according to any of the preceding claims, wherein the coated porous media is fluorine-free.

7. Coated porous media according to any of the preceding claims, wherein the coated porous media has a porosity of 20-99 %.

8. Coated porous media according to any of the preceding claims, wherein the coated porous media has a coating thickness of between 1 nm - 1 micron.

9. Coated porous media according to any of the preceding claims, wherein an external contact angle, denoted by the angle established on the porous media’s outer surface, is between 90 and 160 degrees, preferably between 110 and 160 degrees, more preferably between 130 and 160 degrees.

10. Coated porous media according to any of claims 1-8, wherein an external contact angle, denoted by the angle established on the porous media’s outer surface, is between 0 and 90 degrees, preferably between 0 and 50 degrees.

11. Method of manufacturing a coated porous media according to any of claims 1-10 by chemical or electrochemical grafting, comprising: providing a porous media; immersing the porous media in a bath of a solution or dispersion comprising at least one monomer or polymer which can be radically grafted, at least one diazonium salt or a precursor thereof, and at least one solvent; grafting a polymer on a surface of the porous media to obtain a coated porous media.

12. Method of manufacturing a coated porous media according to any of the claims 1-10 by chemical or electrochemical grafting, comprising: providing a bath of a solution or a dispersion comprising at least one diazonium salt of the compound according to Formula 1 or Formula 2, or a precursor thereof, and at least one solvent; reducing said at least one diazonium salt to a radical compound; providing a porous media and immersing said porous media in said bath; grafting said radical compound on a surface of said porous media to obtain a coated porous media or a precursor thereof; optionally, post-functionalizing said precursor of said coated porous media to obtain said coated porous media.

13. Method according to claim 11 , wherein the at least one monomer or polymer which can be radically grafted is a vinyl terminated organosilicon compound or a vinyl terminated hydrocarbon compound.

14. Method according to claim 13 by electrochemical grafting, wherein the porous media is electrically conductive;wherein the solution or dispersion is an electrolyte solution further comprises at least one supporting electrolyte; and wherein there is a potential difference applied to the bath prior to immersion of the porous media in the bath, said potential difference being generated by an electrochemical cell created between two electrodes immersed in said bath, the two electrodes being different from the porous media.

15. Method according to any one of claims 13-14, wherein the organosilicon compound is selected from Allyltriisopropylsilane (CAS 24400-84-8) Acryloxymethyltrimethylsilane (CAS 67186-35-0) and Monomethacryloxypropyl terminated polydimethyl siloxane (CAS 146632-07-7), preferably wherein the organosilicon compound is Monomethacryloxypropyl terminated polydimethyl siloxane.

16. Method according to any one of claims 14-15, wherein the voltage for the electrochemical grafting is between 0.5 and -1.0 V relative to an Ag7Ag reference electrode.

17. Method according to claim 11 , wherein the at least one monomer or polymer which can be radically grafted is a polar compound, preferably selected from acrylate, amine, alcohol, amide, keton, carboxylic acid, sulphonate, aldehyde, and cyanide.

18. Method according to claim 11 , 12, 13 or 17 by chemical grafting, wherein the solution or dispersion further comprises at least one reducing agent, preferably selected from ascorbic acid, hypophosphorous, sodium dithionite and iron (Fe2+).

19. Method according to any one of claims 11-18, wherein the porous media is selected from carbon, carbon fiber, metal, nobel metal, a surface containing reducible oxide, a graphite surface, a conductive or semiconductive organic surface, a surface of an alloy, a surface of one or more conventional conductive polymer(s), such as a surface based on pyrrole, on aniline, on thiophene, on EDOT, on acetyleneor on polyaromatics, a surface of an intrinsic or doped semiconductor, and any combination of these compounds, preferably wherein the porous media is carbon fiber or carbon particles.

20. Method according to any one of claims 11-18, wherein the porous media is a microporous material, preferably carbon particles, preferably with a pore size of between 0.5 mm and 100 nm.

21. Method according to any one of claims 11-18, wherein the porous media is a catalyst material, preferably platinum supported on a porous substrate, preferably wherein the porous substrate is selected from the group of carbon, or other conductive materials.

22. Method according to any one of claims 11-21 , wherein the diazonium salt is a diazonium salt or a mixture of diazonium salts of generic formula R' — N2+, X“, wherein X“ is a counterion and R' comprises an organic or mineral group selected from the group consisting of nitro, fluoro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, diazonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, acid halide, alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree, and wherein the alkyl, alkenyl, alkynyl, aryl, naphthyl, anthryl, pyrryl and polyaromatic groups of higher degree include a group selected from the group consisting of: nitro, fluoro, bromo, chloro, iodo, thiocyanato, sulphate, sulphonate, sulphonium salts, phosphate, phosphonate, phosphonium salts, diazonium salts, amine, ammonium, alcohol, aldehyde, ketone, carboxylic acid, ester, amide, nitrile, anhydride, and acid halide, preferably nitrobenzene diazonium tetrafluoroborate.

23. Method according to any one of claims 11-22, wherein the immersion and grafting takes place at an underpressure, or in a convectively or forced-pressure driven system.

24. Method according to any one of claims 11-23, wherein the porous media is a dispersion of solid particles.

25. Fuel cell comprising the coated porous media according to any of claims 1-10.

26. Use of a coated porous media according to any of claims 1-10 for an electrochemical energy system, preferably wherein the electrochemical energy system is a multiphase electrochemical energy system, preferably selected from a polymer electrolyte membrane fuel cell, a polymer electroyte membrane water electrolyzer, an alkaline exchange membrane fuel cell, an alkaline exchange membrane water electrolyzer, a reversible fuel cell system, a carbon dioxide electrolyzer,27. Use of a coated porous media according to any of claims 1-10 as protective coating in textiles, automotive, aerospace or maritime applications, electronics, kitchenware, sanitation and plumbing, oil and gas pipelines, solar panels, medical equipment, constructions and food processing.

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