FR3001732A1 - USE OF DISPERSING AGENTS FOR THE PREPARATION OF INKS FOR FUEL CELLS - Google Patents

Abstract

The present invention relates to the use of a compound as a dispersing agent in a dispersion comprising said compound, at least one catalytic pigmentary conductor and at least one solvent, said compound comprising an aromatic hydrophobic part, and a hydrophilic part. comprising an anionic end and / or a linear chain comprising at least 12 links -OCH2CH2-. The present invention also relates to the use of said compound as a dispersing agent in an ink formulation comprising said dispersion and a proton conductive polymer. The present invention also relates to a dispersion comprising said compound, suitable for the preparation of an ink formulation for a fuel cell electrode, particularly for a PEMFC electrode.

Description

The present invention relates to the use of dispersing agents for the preparation of dispersions, more particularly fuel cell inks. Inks used for the preparation of fuel cell electrodes, particularly for proton exchange membrane (PON) fuel cell electrodes, are generally deposited on substrates by coating or spraying . These inks, in aqueous base, generally comprise catalytic particles dispersed in an aqueous dispersion of proton conductive polymer. These deposition techniques require that the inks exhibit good dispersion properties of the catalytic particles and a good affinity for the printing medium of the cell, while maintaining catalytic and electrochemical properties adapted to the operation of the battery. combustible. In the formulations of the state of the art, there are generally problems of instability of the dispersion of the catalytic particles, such as agglomeration and sedimentation of the particles - agglomerates up to a size of 50 μm, which makes difficult depositing said inks. In order to overcome these problems, additives, such as surfactants, wetting agents or dispersing agents, are generally used which make it possible to maintain a good dispersion of the catalytic particles in the aqueous proton-conducting polymer dispersion.

Nevertheless, these additives have the disadvantage of polluting by poisoning the catalytic particles, which causes a decrease in the electrochemical performance of the fuel cell. As additives for fuel cell inks, mention may be made of the dispersants of the brands Darvan, Disperbyk, Solsperse, Tego Dispers used in US 2006/0292434 or the Triton X-100 used in US 6844286. There is therefore a need for additives which make it possible to obtain ink formulations which do not alter the initial size of the particles, the stability of their dispersion or the electrochemical performances of said inks. Furthermore, the state of the art mainly deals with inks for spray deposition, that is, inks with low solids and low viscosity.

There is therefore also a need for additives to obtain stable solid ink formulations with high solids, suitable for the preparation of fuel cell electrodes, more particularly PEMFC electrodes.

An object of the present invention is to provide a dispersion suitable for preparing fuel cell electrode ink, particularly for PEMFC electrode. Another object of the present invention is to provide a dispersion having properties of stability, viscosity and a particle size suitable for the preparation of such an ink. Another object of the present invention is to provide a dispersion suitable for the preparation of such an ink, without altering its catalytic and electrochemical activity. Another object of the present invention is to provide an ink suitable for deposition by spraying, coating or any other type of deposit, such as for example inkjet, screen printing, flexography, gravure and offset. , having stability properties, particle size, and catalytic activity suitable for preparing a fuel cell electrode, particularly a PEMFC electrode. For this purpose, the present invention proposes to use a dispersing agent in a dispersion comprising a catalytic pigment conductor and a solvent. The present invention further provides the use of a dispersing agent in an ink formulation comprising a catalytic pigment conductor, a proton conductive polymer and a solvent. More specifically, the subject of the present invention is the use of a compound as a dispersing agent in a dispersion comprising said compound, at least one catalytic pigmentary conductor and at least one solvent, said compound comprising: an aromatic hydrophobic part, and a hydrophilic portion comprising an anionic end and / or a linear chain comprising at least 12 links -OCH 2 CH 2 -. By "hydrophobic aromatic part" is meant a hydrophobic, that is to say, lipophilic and insoluble in water, molecular fragment comprising at least one hydrophobic aromatic unit, typically a phenyl group.

By "hydrophilic part" is meant a hydrophilic, that is to say lipophobic and water-soluble molecular fragment, comprising hydrophilic groups, such as oxygenated groups or anionic groups, for example. Oxygen groups that may be mentioned include polyethylene glycol chains or hydroxyl groups. As anionic groups, mention may be made of sulphate, phosphate or sulphonate groups. The aromatic hydrophobic part and the hydrophilic part of the compound used as dispersing agent according to the invention give said compound its surfactant and dispersant properties. More particularly, the aromatic hydrophobic portion interacts, through the hydrophobic aromatic unit, with the catalytic pigmentary conductor, which is typically in the form of particles. The hydrophilic part makes it possible to stabilize the dispersion in aqueous phase thanks to the negative charge of its anionic end or thanks to its oxygenated linear chain. According to one embodiment, the molar mass of the dispersing agents according to the invention is less than 500 g / mol. According to one embodiment, the compound used as dispersing agent is a compound of formula ABZ, in which: the group A- represents a phenyl or naphthyl group, optionally substituted with 1 to 5 groups independently selected from the group consisting of alkyl groups, linear or branched, comprising from 1 to 20 carbon atoms, and phenyl, optionally substituted by one or more alkyl, aryl, halogen or haloalkyl groups, the -B- group represents a single bond or a chain - ( OCH2CH2), where n is greater than or equal to 12, and the group -Z is selected from the group consisting of -OH group and -SO3-1V1 +, -0SO3-M + and -0P (O) (OH) groups. (0-M +) in which 1V1 + represents a positive charge counter-ion.

Groups A- and -Z are monovalent groups.

The -B- group is either a single bond or a divalent oxygenated hydrocarbon chain. The M + cation typically represents a cation selected from the group consisting of H +, Na, K +, NH4 + cations and alkylammonium cations.

By "alkylammonium" is meant here a primary ammonium cation (RaNH3 +), secondary (RaRMH2 +), tertiary (RaRpRyNH ±) or quaternary (RaRpRyRôN ±), in which the groups Ra, Rp, Ry and Flo independently represent an alkyl in C1 -06. Preferably, -O-P (O) (OH) (O-M +) is -O-P (O) (OH) 2. Preferably, -OP (O) (OH) (O-M +) is -OR (O) (OH) (O-NH4 +).

Preferably, -SO 3 -M + is -SO 3 -Na +. Preferably, -SO3-M + is -SO3-Na +. According to the present invention, the "alkyl" groups represent saturated hydrocarbon radicals, straight or branched chain, comprising from 1 to 20 carbon atoms. When they are linear, mention may be made especially of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl and decyl groups. When they are branched or substituted by one or more alkyl groups, mention may be made especially of the isopropyl, tert-butyl, 2-ethylhexyl, 2-methylbutyl, 2-methylpentyl, 1-methylpentyl and 3-methylheptyl radicals. According to the present invention, the term "aryl" denotes a hydrocarbon aromatic system, mono or bicyclic comprising from 6 to 30, preferably from 6 to 10, carbon atoms. Among the aryl groups, mention may especially be made of phenyl, naphthyl and anthracenyl groups, more particularly substituted with at least one halogen atom. Preferably, the term aryl means a phenyl group.

According to one embodiment, the compound used as dispersing agent is a compound of formula (I): R7A7Z1 (1) in which: the group -A1- represents a phenylene or naphthylene radical, optionally substituted by one or more groups alkyl, aryl, halogen or haloalkyl, the group R1- represents a linear or branched alkyl group comprising from 1 to 20 carbon atoms, optionally substituted with one or more alkyl, aryl, halogen or haloalkyl groups, and the group -Z1 represents a group -S03-M1 +, wherein M1 + is a positive charge counter-ion.

The M1 + cation typically represents a cation selected from the group consisting of H +, Na, K +, NH4 + cations and alkylammonium cations. According to one embodiment, in the formula (1), the group R1- represents an unsubstituted linear alkyl chain comprising at least 10 carbon atoms. According to one embodiment, in the formula (1), the group -A1- represents a phenylene radical. According to one embodiment, in formula (1), the group -Z1 represents a group -SO3-Na +.

According to one embodiment, the compound used as dispersing agent is a compound of formula (1 '): SO, Na + in which the R'1- group represents a linear or branched alkyl group comprising from 10 to 20 carbon atoms, optionally substituted by one or more alkyl, alkoxy, aryl, halogen or haloalkyl groups. According to one embodiment, in the formula (1 '), the R'1- group represents a linear alkyl chain comprising from 10 to 20 carbon atoms, typically 12 carbon atoms.

Preferably, the group R'l is not substituted. By way of example of a compound corresponding to formulas ABZ, (1) and (1 '), mention may be made of sodium n-dodecylbenzene sulphonate of formula: SO3Na According to one embodiment, the compound used as dispersing agent is a compound of formula (2): n Z2 (2) wherein: the group -Z2 is selected from the group consisting of -OH and -SO3-1V1 + and -0P (O) (OH) groups (0) -M ±) in which IV1 + represents a positive charge counter-ion, the R2- group represents a linear or branched alkyl group comprising from 1 to 10 carbon atoms, optionally substituted by one or more alkyl, aryl or halogen groups; or haloalkyl, n is greater than or equal to 12, and m is 0 to 5.

According to one embodiment, in the formula (2), the group R2- represents a linear or substituted alkyl chain comprising from 1 to 6 carbon atoms. According to one embodiment, in the formula (2), the group R2- represents an alkyl chain substituted by at least one phenyl group.

According to one embodiment, in formula (2), m is greater than 1. According to one embodiment, in formula (2), n is equal to 16. According to one embodiment, in formula (2) , -0S03-1V1 + represents -SO3-Na +. According to one embodiment, in the formula (2), -O P (O) (OH) (O-M +) represents -O P (O) (OH) 2. According to one embodiment, in the formula (2), -O P (O) (OH) (O-M +) represents -O P (O) (OH) (O-NH +). According to one embodiment, the compound used as dispersing agent is a compound of formula (2 '): n (2') in (2 ') in which: the group -Z'2 is chosen from the group consisting of of the -OH group, the -SO 3 -Na + group and the -O P (O) (OH) (O-M 1) group in which IV 1 + represents a positively charged counterion, the group -R '2 represents an alkyl group linear, comprising from 1 to 6 carbon atoms, substituted with at least one phenyl group, optionally substituted with one or more alkyl or halogen groups, and n is greater than or equal to 12.

According to one embodiment, in the formula (2 '), -O P (O) (OH) (O-M +) represents -O P (O) (OH) 2. According to one embodiment, in the formula (2 '), -O P (O) (OH) (O-M +) represents -O P (O) (OH) (O-NE 14 +). According to one embodiment, in the formula (2 '), the group -R'2 represents a methyl or ethyl chain, substituted by an optionally substituted phenyl group. According to one embodiment, in the formula (2 '), the group -R'2 represents a benzyl chain (-CH2Ph), 2-ethylbenzene (-CH2CH2Ph) or 1-ethylbenzene (-CH (Ph) CH3). According to one embodiment, in formula (2 '), n is equal to 16.

According to one embodiment, the compound used as dispersing agent is a compound of formula (2 "): nZ.2 (2 ') Ph - in which the group -Z'2 and n are as defined in formula (2 ').

According to one embodiment, in the formula (2 "), n is equal to 16. By way of example of a compound corresponding to the formulas ABZ, (2), (2 ') and (2"), mention may be made of Compounds of formula: Phonazole Tristyrylphenol ethoxy Z = -PO (O) (OH) 2 gO1 n = 16 phosphate (acid form) Ph Ph Tristyrylphenol ethoxy Z = -OH (<10%) and Z = -0P (0) (OH) 2 phosphate Tristyrylphenol ethoxylate Z = -OH Tristyrylphenol ethoxy Z - -OSO3 NH4 + ammonium sulfate The dispersing agents according to the invention are particularly suitable for the preparation of dispersions and ink formulations for PEMFC electrode. Another object of the present invention is a dispersion comprising one of the compounds mentioned above as dispersing agent according to the invention. More specifically, the subject of the present invention is also a dispersion, comprising: at least one dispersing agent according to the invention, at least one catalytic pigmentary conductor, and at least one solvent. By "dispersion" is meant a stable suspension of particles in a solvent.

According to the invention, the term "dispersing agent" is understood to mean a surfactant chemical compound making it possible to fix hydrophobic particles contained in a hydrophilic solution, such as an aqueous solution, which makes it possible to create a stable dispersion, that is to say say an aqueous solution containing suspended particles. These agents prevent the flocculation of the particles, that is to say their agglomeration and their sedimentation in the bottom of the solution. By "catalytic pigmentary conductor" is meant an electrocatalytic species comprising a conductive support, said support being in the form of particles coated with catalyst, that is to say a catalyst supported on a conductive support.

By "catalyst-coated particles" it is meant that the particles are at least partly or completely covered with a catalyst layer. According to one embodiment, the catalytic pigment conductor is in the form of conductive particles coated with a catalyst layer. In the context of the present invention, the term "catalyst" means a species, preferably metal, which promotes an electrochemical reaction. The catalyst of the invention is deposited, at least partially or totally, on an electrical conductor; the whole is called electrocatalyst. The catalyst may be supported on a conductive support, such as carbon particles, in the form of spherical particles, carbon fibers, or carbon nanotubes for example. According to the present invention, the term "dispersion" corresponds to the mixture stable form of a catalytic pigmentary conductor, in the form of conductive particles as described above, in a solvent, said mixture being stabilized by a dispersing agent according to the invention.

The use of the dispersing agent according to the invention makes it possible to stably disperse the catalytic pigmentary conductor in the dispersion according to the invention. The dispersion according to the invention is stable for at least one week. The dispersions according to the invention are particularly suitable for the preparation of PEMFC inking electrode formulations. The use of the dispersing agent according to the invention makes it possible to efficiently disperse the catalytic pigmentary conductor in the dispersion and in the ink formulation according to the invention.

No macroscopic aggregate is observed when spreading the dispersion or the ink according to the invention on a Hegman gauge, unlike inks prepared with dispersing agents of the state of the art. According to one embodiment, the solvent of the dispersion according to the invention is chosen from water, an organic solvent, or mixtures thereof. According to one embodiment, the dispersions according to the invention comprise, as a solvent, a mixture of water and at least one organic solvent. According to one embodiment, the dispersions according to the invention are aqueous dispersions, that is to say that they contain at least water, generally in a proportion by weight of between 30% and 80%, preferably from 50% to 70%, based on the total mass of the dispersion. According to one embodiment, the dispersions according to the invention comprise one or more organic solvents, in a total mass proportion of 5% to 20%, preferably 10% to 15%, relative to the total mass of the dispersion. Suitable solvents for the invention include glycols (for example ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol or mixtures thereof), alcohols (for example alcohols, Cl-04 and mixtures thereof), esters (for example esters of Cl-02 alcohols with a C 1 -C 2 carboxylic acid and mixtures thereof), aprotic polar solvents (for example N-methylpyrrolidone, ethylene carbonate, propylene carbonate or DMSO), as well as their mixtures. According to one embodiment, the solvent is chosen from glycols and is, for example, ethylene glycol. Ethylene glycol is a cosolvent suitable for the implementation of the invention by its amphiphilic character and its solvation and compatibilization properties. According to one embodiment, the catalytic pigmentary conductor comprises a surface comprising a metal selected from the group consisting of platinum, silver, palladium, ruthenium, nickel, tungsten, cobalt, osmium, molybdenum, titanium, chromium, iron, iridium, gold, tin, and their alloys. According to one embodiment, the metal of the catalytic pigmentary conductor is platinum. In the context of electrodes for PEMFC, platinum is a catalyst particularly suitable for being the seat of electrochemical reactions of oxidation of hydrogen and reduction of oxygen. Platinum is a catalyst particularly suitable for producing inks for active layers of PEMFC.

As a catalytic pigmentary conductor suitable for the invention, mention may be made of Tanaka TEC10V50E Pt / C 45.6% Pt (carbon black particles partially coated with platinum). According to one embodiment, the catalytic pigmentary conductor is in the form of individualized conductive particles or aggregates of conductive particles, covered with a layer of metal selected from the group consisting of platinum, silver, palladium, ruthenium nickel, tungsten, cobalt, osmium, molybdenum, titanium, chromium, iron, iridium, gold, tin, and their alloys.

According to this embodiment, the catalytic pigmentary conductor particles generally comprise a mass proportion of catalyst of from 5% to 80% and a mass proportion of conductive support of from 95% to 20%.

The dispersions of the invention make it possible to obtain individualized particles or aggregates of catalytic pigmentary conductor particles of average size in dispersion of less than 5 μm, preferably less than 2 μm, preferably of from 0.1 μm to 1 μm. mean dispersion size "means here the average size, as measured by light scattering, of particles or aggregates of particles within the dispersion themselves. Particle size can be measured with a Malvern Instrument laser granulometer, using the light scattering technique. This range of particle size distribution allows the use of inks for screen printing processes (eg screen size of a screen printing screen = 10 μm) and ink jet (example: diameter of nozzles = 21 lm). According to one embodiment, the mass ratio between the dispersing agent and the catalytic pigmentary conductor in the dispersion is between 0.3 and 0.5, and preferably about 0.4. This mass ratio range allows effective dispersion of the catalytic pigmentary conductor particles by the dispersing agent.

According to one embodiment, the dispersion according to the invention further comprises an anti-foaming agent, preferably in a mass proportion of from 0.01% to 0.5% relative to the total mass of the dispersion. By "anti-foaming agent" is meant a compound for reducing the formation of foam in a liquid.

The presence of an anti-foaming agent in the dispersion of the invention makes it possible to limit or even prevent the formation of foam during the preparation of said dispersion, in particular during the mixing and / or grinding steps. As anti-foaming agent, mention may be made of silicone-based agents and agents based on a mixture of paraffin and nonionic surfactant.

For example, Rhodoline® 1010 (Rhodia) and Foamaster® NDW (Cognis) may be mentioned. The dispersion according to the invention has a viscosity suitable for grinding the catalytic pigmentary conductor, unlike dispersions prepared with dispersing agents of the state of the art.

According to one embodiment, the dispersion has a dynamic viscosity of from 10 cP to 2000 cP, which corresponds to a range of 0.01 Pa.s at 2 Pa.s. Preferably, the dispersion has a dynamic viscosity of from 50 cP to 1500 cP, advantageously from 100 cP to 1000 cP, and typically a few hundred cP. The dynamic viscosity of the dispersions according to the invention can be measured according to a conventional protocol, for example using a Brookfield LVT 8500 viscometer (axis 3 at 60 rpm).

According to one embodiment, the mass ratio between the anti-foaming agent and the catalytic pigmentary conductor is from 0.01 to 0.05, preferably approximately equal to 0.02. According to one embodiment, the dispersion according to the invention comprises, relative to the total mass of the dispersion: a mass proportion of dispersing agent according to the invention of from 1% to 10%, preferably from 4% to 6% a mass proportion of catalytic pigmentary conductor of from 10% to 20%, preferably from 14% to 18%, a mass proportion of organic solvent of from 10% to 20%, preferably from 12% to 16%, and a mass proportion of water of from 50% to 75%, preferably from 60% to 70%.

Another object of the present invention is an ink formulation, typically for PEMFC electrodes, comprising a dispersion as mentioned above. More specifically, the present invention also relates to an ink formulation, comprising: a dispersion according to the invention, and a proton conductive polymer. According to one embodiment, the ink formulation also includes an additional amount of water. By "additional" it is meant that the mixture of the dispersion of the invention and the proton conducting polymer is diluted by an additional amount of water.

This mode makes it possible to dilute the ink formulation in order to adjust the desired mass proportion of solids. According to one embodiment, the ink formulation also comprises an additional amount of organic solvent, as defined above.

The use of the dispersing agent according to the invention makes it possible to maintain a good quality of dispersion of the ink formulations and a good size of catalytic pigmentary conductor particles, even after the addition of proton conducting polymer to the dispersion according to the invention. invention, in contrast to inks prepared with dispersing agents of the state of the art. The ink formulations of the invention make it possible to obtain individualized particles or aggregates of catalytic pigmentary conductor particles having a mean size of less than 5 μm, preferably less than 2 μm, preferably of between 0.1 μm and 1 μm. . By "average size" of the particles is meant here the average size, as measured by light scattering, of particles or aggregates of particles within the ink formulation. The particle size ranges described above facilitate the process of coating substrates with the ink formulations of the invention. Such ranges allow the use of various deposition techniques, such as screen printing, coating, spraying or inkjet. Indeed, these methods require particle size characteristics to pass, for example, in screen printing screen cells (size 10 lm for example) or ejection nozzles (diameter 21 lm for example). By "proton conductive polymer", also called ionomer, is meant a polymer capable of transporting protons. Within a PEMFC fuel cell, the proton conducting polymer present in the electrodes allows the transport of protons from the anode electrode (oxidation of hydrogen according to the reaction H2 2H + + 2e-) to the cathode electrode (reduction oxygen through the reaction 2H + + 2e- +02 2H20) through the polymer membrane proton exchange, the electrochemical reactions of oxidation of hydrogen and reduction of oxygen occurring on the catalytic sites of the driver catalytic pigment.

According to one embodiment, the proton conducting polymer is a perfluorinated polymer. According to one embodiment, the proton conducting polymer is a perfluorosulfonic acid polymer.

Typically, the proton conductive polymer is a copolymer of tetrafluoroethylene and perfluoro [2- (fluorosulfonyl-ethoxy) -propyl] vinyl ether, having the following formula: [(CF 2 CF 2) n - CF - C [OC F 2 -CF 2 OCF 2] - CF SO3 CF in which: m is an integer of 1, 2 or 3, n is an integer from 5 to 13, and x is generally about 1000. As a proton conductive polymer, there may be mentioned Nafion® , commercially available at DuPont de Nemours, and in particular the commercial solutions Nafion® DE 520, Nafion® DE 521, Nafion® DE 1020, Nafion® DE 1021, Nafion® DE 2020 or Nafion® DE 2021. Among these solutions, those adapted to the present invention are in particular the commercial solutions Nafion® DE 520, Nafion® DE 2020 or Nafion® DE 2021.

According to another embodiment, a polymer of formula (I) as described in WO 2010/142772 (under the name of "(per) fluoroionomoère") is used as the proton conducting polymer.

As a protonic conductive polymer, it is possible to use in particular a polymer comprising repeating units derived from a fluorinated monomer chosen from the group consisting of the following fluorinated monomers: (M1) perfluoroolefin sulfone of formula (M1): F SO, X ' F (M1) wherein: n is an integer from 0 to 6, and X 'is selected from the group consisting of halogen atoms (Cl, F, Br, I) and the group -O-M +, wherein M + is a cation selected from the group consisting of H +, NH4, K +, Lit, Na, or mixtures thereof, X 'preferably being -O-H +; preferred sulfonated perfluoroolefins being those of the formula (MI-A) and (MI-B): CF FF, 50, X '' - '- CF; - CF - F (M1-A) F (MI) -B) in which X 'is as defined above; (M2) sulfonated perfluorovinyl ether of formula (M2): F CF, F F (M2) j77.-1 5 ° 2x' wherein: m is an integer inclusive from 1 to 10, and X 'is selected from the group consisting of halogen atoms (Cl, F, Br, I) and the group -O-M +, wherein M + is a cation selected from the group consisting of H +, NH 4, K +, Lit, Na, or mixtures thereof, X 'being preferably -O-H +, the preferred sulfonated perfluorovinyl ethers being those of formula (M2-A), (M2-B) and (M2-C): FFF F ## STR5 ## F 2 (M2-B) F (M2-C) F N F 1, CF 1, CF 2. Wherein CF 'is as defined above; and a particularly preferred sulfonated perfluorovinyl ether being perfluoro-5-sulfonylfluoride-3-oxa-1-pentene (also referred to as "SFVE") of the formula (M2-D): ## STR2 ## 42-b) which exists in its form -SO2F or, preferably, in one of the forms -SO2X 'described above, and more particularly in the form -SO3H; (M3) sulfonated perfluoroalkoxyvinyl ether of formula (M3): ## STR2 ## in which: w is an integer ranging from 0 to 2, RF and RF2; , which may be identical or different, independently represent F, Cl or a C 1 -C 10 perfluoroalkyl group, optionally substituted by one or more ether groups, y is an integer from 0 to 6, and X 'is chosen from the group consisting of halogen (Cl, F, Br, I) and the group -O-M +, wherein M + is a cation selected from the group consisting of H +, NH4, K +, Lit, Na, or mixtures thereof, X 'being preferably -0-H +; a preferred sulfonated perfluoroalkoxyvinyl ether being that of formula (M3-A), also called "PSEPVE": CF O CF '(M3-A) which exists in its -SO2F form or, preferably, in one of the forms -SO2X' described herein above, and more particularly in the form -S03H; (M4) perfluoroalkoxyvinyl ether carboxylate of formula (M4): ## STR2 ## in which w, y, RF and RF2 have the same meanings as in formula (M3) ci above, and RH represents a C1-C6 alkyl or fluoroalkyl group, a perfluoroalkoxyvinyl ether carboxylate being preferred having the formula (M4-A): (M4-A) (M5) (per) sulfonated aromatic fluorinated olefin of formula (M5) Wherein: Ar is an aromatic or heteroaromatic link at 03-015, and X 'is selected from the group consisting of halogen atoms (Cl, F, Br, I); ) and the group -O-M +, wherein M + is a cation selected from the group consisting of H +, NH4, K +, Lit, Na, or mixtures thereof, X 'preferably being -O-H +. the mass proportion of proton conductive polymer in the ink formulation is from 1% to 5% relative to the total mass of the formulation According to one embodiment, the pigm concentration The volume void (PVC) of the ink formulation according to the invention is from 50 to 100. By "pigment volume concentration" is meant the ratio of the volume of the catalytic pigmentary conductor to the sum of the volumes of the catalytic pigmentary conductor. and proton conductive polymer. According to one embodiment, the ink formulation according to the invention comprises a mass proportion of liquid phase of 85% to 98% relative to the total weight of the formulation. By "liquid phase" is meant all of the liquid components of the ink formulation, i.e. water and organic solvent (s). Ink formulations according to this mode are particularly suitable for depositing the ink on a substrate by inkjet or sputtering.

According to one embodiment, the ink formulation according to the invention comprises a mass proportion of liquid phase of 60% to 80% relative to the total weight of the formulation. Ink formulations according to this mode are particularly suitable for depositing the ink on a substrate by screen printing or coating. According to one embodiment, the inks according to the invention have a dry extract comprised of 4% to 30%, preferably 15% to 30%.

By "dry extract" of a dispersion (or an ink formulation) is meant the ratio of the residual dry mass of the dispersion (or of the ink formulation) after removal of its volatile components by evaporation, on the total mass of the dispersion (or the ink formulation) before evaporation.

An ink with a high solids content is particularly suitable for deposition by screen printing or coating. In the context of the invention, it is referred to as "high solids" for a percentage of dry mass greater than 10%, generally 10% and 30%. A low solids ink is particularly suitable for ink jet or spray deposition. In the context of the invention, the term "low solids" for a dry weight percentage of less than 10%, generally from 4% to 10%. According to one embodiment, a low solids ink formulation according to the invention comprises, with respect to the total mass of the ink formulation: a mass proportion of dispersing agent according to the invention of 0.1% at 4%, preferably from 0.5% to 1%, a mass proportion of catalytic pigmentary conductor of from 1% to 7%, preferably from 2% to 4%, an organic solvent proportion of from 10% to 20%, preferably 14% to 18%, and a mass proportion of water of 50% to 90%, preferably 65% to 85%. According to one embodiment, an ink formulation with a high solids content according to the invention comprises, with respect to the total mass of the ink formulation: a mass proportion of dispersing agent according to the invention of from 2% to 7%; %, preferably from 4% to 6%, a mass proportion of catalytic pigmentary conductor of 10% to 20%, preferably 12% to 15%, an organic solvent proportion of 10% to 30%, preferably from 15% to 25%, and a mass proportion of water of 50% to 70%, preferably 50% to 60%.

Another object of the present invention is the process for preparing the dispersions according to the invention. More specifically, the subject of the present invention is also a method for preparing a dispersion according to the invention, comprising the following steps: the mixing of the solvent, of the dispersing agent and of the catalytic pigmentary conductor, and the grinding of the mixture obtained to obtain said dispersion. Preferably, the order of introduction of the various constituents is such that the catalyst is weighed first, then is covered with the aqueous phase, the dispersing agent is then added. This mixing step is also called the pre-dispersion step. The grinding of the mixture comprising the solvent, the dispersing agent and the catalytic pigmentary conductor may be carried out by mechanical stirring, using grinding balls, typically Burundum® zirconium grinding balls, or by using a dispersing disc. The grinding generally lasts several hours, typically from 2 to 12 hours. The grinding step makes it possible to obtain a stable dispersion of particles and a fine particle size, that is to say particles of small size, preferably less than 1. Another object of the present invention is the process for the preparation of ink formulations according to the invention. More precisely, the subject of the present invention is also a process for preparing an ink formulation according to the invention, comprising a step of mixing the proton conducting polymer with a dispersion according to the invention.

The mixing step is optionally followed by a dilution step with an additional amount of water. Alternatively, the proton conducting polymer and / or the dispersion according to the invention are previously diluted with water.

This prior dilution step makes it possible to adjust the dry extract of the prepared ink formulation. The mixing step is optionally followed by a grinding step by mechanical stirring to provide the ink formulation according to the invention. This grinding step makes it possible in particular to preserve the small size of the catalytic pigmentary conductor particles. The present invention also relates to the use of an ink formulation according to the invention for the preparation of a substrate coated with a catalytic pigmentary conductor layer.

This type of substrate comprising a catalytic pigmentary conductor layer is particularly suitable for use in electrochemistry, for example for fuel cells.

Unlike the dispersing agents of the state of the art, the use of the dispersing agents according to the invention causes no pollution, or very low pollution, of the catalytic pigmentary conductor, more precisely the catalyst that it comprises. The dispersing agents according to the invention do not alter the electrochemical performances of the catalysts within the fuel cell electrodes and do not affect the performance of a fuel cell operating under reactive gases. The ink formulations according to the invention are particularly suitable for the preparation of a proton exchange membrane (PEMFC) fuel cell electrode. The subject of the present invention is also the process for preparing a substrate coated with a layer comprising the catalytic pigmentary conductor and the proton conducting polymer, comprising the following steps: depositing an ink formulation according to the invention on a substrate, and - drying the resulting substrate to obtain said coated substrate.

Drying is typically carried out under standard conditions, at room temperature, or below or equal to 80 ° C (depending on the methods chosen) and in air.

As a suitable substrate on which the catalytic ink formulations are deposited, mention may be made of the Gas Diffusion Layer (GDL) diffusion layers commonly used for fuel cells, such as GDLs based on carbon fabric, felt carbon or carbon paper. There may also be mentioned the proton conducting polymer membrane on which the inks can be deposited. It is also possible to deposit the inks on a neutral support (teflon type) and then to postpone this layer on the GDL or the membrane. The layer comprising the catalytic pigment conductor and the proton conductor comprises the catalyst which corresponds to the catalytic sites where the electrochemical reduction or oxidation reactions take place in the fuel cell electrodes. According to one embodiment, the deposition step on the substrate is carried out by a deposition technique chosen from inkjet, coating, screen printing, spraying, flexography, gravure and offset. Depending on the deposition mode that one wishes to achieve, one will choose an ink formulation with a high solids content (greater than 10%, typically from 10% to 30%) or a low solids ink formulation (lower at 10%, typically ranging from 4% to 10%). The dispersing agents according to the invention make it possible to prepare both high solids and low solids ink formulations.

The dispersing agents according to the invention make it possible to prepare ink formulations suitable for any type of deposit. The present invention also relates to a coated substrate obtainable by the method described above. The subject of the present invention is also a proton exchange membrane fuel cell electrode comprising a substrate coated according to the invention. . An ink formulated according to the invention, comprising a dispersing agent, a catalytic pigmentary conductor and a proton conducting polymer, may be deposited by coating on a diffusion layer (of the carbon fabric type), according to the CCB (Catalyst Coated Backing) technique. . This set constitutes a GDE (Gas Diffusion Electrode), which is assembled with a polymer membrane and another GDE, in order to constitute the AME (Membrane Electrode Assembly). The differentiation between anode electrode and a cathode electrode can be effected by the catalyst loading which is generally lower at the anode (for example: 0.2 mgPt / cm 2 at the anode and 0.4 mg Pt / cm 2 at the cathode) . According to one embodiment, the electrode according to the invention is anodic and is intended to be used as anode in a fuel cell.

According to one embodiment, the electrode according to the invention is cathodic and is intended to be used as a cathode in a fuel cell. The present invention also relates to a proton exchange membrane fuel cell comprising a coated substrate according to the invention or an electrode according to the invention.

EXAMPLES Dispersions and inks were made according to the conditions of the following examples. Two versions of dispersions and inks were prepared, a catalytic version and a non-catalytic version. Dispersions and non-catalytic inks (that is to say not comprising a metal catalyst) nevertheless have the same mechanical dispersion behavior as their catalytic counterparts. These non-catalytic dispersions and inks are prepared in order to show the dispersant properties of the compounds according to the invention compared to the compounds of the state of the art used as dispersing agent. Dispersions and catalytic inks have also been prepared to show the compatibility of the compounds according to the invention with respect to catalysts intended to promote electrochemical reactions within PEMFC in particular.

Catalytic and Non-Catalytic Pigmenting Paste Catalytic dispersions and inks were prepared with Tanaka TEC10V50E Catalytic Powder Pt / C 45.6% Pt (Catalytic Pigmenting Conductive). The non-catalytic dispersions and inks were prepared with Vulcan XC 72 R non-catalytic powder (carbon black) (non-catalytic pigment conductor), having the same carbon support as the Tanaka catalytic powder. Dispersing agents Dispersing agents according to the invention 1 to 5: 1 n-dodecylbenzene sulphonate C12H25 go S 03N a sodium 2 Tristyrylphenol ethoxy Ph 0 n ZZ = -Op (O) (OH) 2 phosphate (acid form) el _ n = Ph Ph 3 Tristyrylphenol ethoxy Z = -OH (<10%) and Z = -O P (O) (OH) 2 phosphate (low nonionic) 4 Tristyrylphenol ethoxylate Z = -OH 5 Tristyrylphenol ethoxy Z - -SO 3 NH 4 + ammonium sulfate Dispersing agent described in the state of the art: 5 - Triton X100 (ethoxy octyl o-benzene) nn - 9-10 - Comparative dispersing agents 6 to 9: 6 Polypropylene oxide-polyethylene oxide 7 α-olefin sulfonate sodium CH 3 (CH 2) n-CH = CH-CH2-SO3Na n = 14-16 8 Oleyl N-methyl tau spleen of 0 sodium C8H, NSO3Na 7 I CH3 9 Laureth-3-sulfosuccinate of 0 disodium SO3Na 0121-125 0 COONa Anti-foaming agents Rhodoline ® 1010 (Rhodia) Foamaster® NDW (Cognis) Proton Conductive Polymer (Dupont ionomer solutions) Nafion® Propanol Water Nafion® Solution DE 520 5 21 21 Nafio Solution DE 2020 50 45.5 45.5 Nafion® solution DE 2021 45 33.5 33.5 Example 1: Preparation of a reference ink A (without dispersing agent) The reference ink A was prepared without dispersing agent. In a 500 ml flask, 36.02 g of Nafion® DE2020 solution are added to 0.14 g of Rhodoline 1010, then 18.06 g of ethylene glycol and then 72 g of millipore water. The mixture is then homogenized with magnetic stirring using a magnetic bar. The continuous phase is then injected with a syringe into a 500 mL "hermetic" jar containing 20.59 g of Vulcan XC 72R carbon black. In order to impregnate the carbon black, the jar is placed for 13 hours on a Roller-mill. The resulting mixture (composition shown in Table 1) is pre-dispersed with a deflocculator 8 cm in diameter for 15 minutes at 2000 rpm. In order to grind the carbon black, a mixture of 150 g and 383 g of Burundum® Zirconium grinding balls (cylindrical shape, height and diameter of 6) is added to a 500 ml jar containing 1/3 (by volume) of the mixture, ie 150 g. mm). The jar is then placed on the roller-mill to ensure the movement of the balls for 8 hours. Table 1: Ink A (reference) Components Mass (3/0 mass relative to the total solution Nafion® DE2020 36.02 g 24.5% Rhodoline 1010 0.14 g 0.095% Ethylene glycol 18.06 g 12.3% Water 72.0 g 49.0% Vulcan XC 72R 20.59 g 14.0% Example 2: Preparation of a reference dispersion B (with Triton X100 dispersing agent) The Triton X100 dispersing agent was used to prepare the dispersion reference B.

This dispersing agent is known to disperse carbon black and has already been used in catalytic ink formulations of the literature (A.A. Abaoud, Int.J. Hydrogen Energy, 2005, 30: 385-391). Pre-dispersion of the non-catalytic pigmentary conductor In a 500 ml flask was added 10.8 g of Triton X100 solution with 0.18 g of Rhodoline 1010, then 18.06 g of ethylene glycol and then 105 g of millipore water. The mixture is then homogenized with magnetic stirring using a magnetic bar. The continuous phase is then injected with a syringe into a 500 mL "hermetic" jar containing 26.57 g of Vulcan XC 72R carbon black.

In order to impregnate the carbon black, the jar is placed for 13 hours on a Roller-mill. The resulting mixture (composition shown in Table 2) is pre-dispersed with a deflocculator 8 cm in diameter for 15 minutes at 2000 rpm. Grinding In order to grind the carbon black, a mixture of 150 g and 383 g of Burundum® Zirconium grinding balls (cylindrical shape, height and diameter) is added to a 500 ml jar containing 1/3 (by volume) of the mixture, ie 150 g. 6mm). The jar is then placed on the roller-mill to ensure the movement of the balls for 8 hours.

Table 2: Dispersion B (reference) Components Mass (3/0 mass relative to total Triton X100 10.8g 6.7% Rhodoline 1010 0.18g 0.11% Ethylene glycol 18.06g 11.2% Water 105.0 g 65.4% Vulcan XC 72R 26.57 g 16.5% EXAMPLE 3 Preparation of Non-Catalytic Dispersions According to the Invention D1 to D5 and Comparative Non-Catalytic Dispersions D6 to D9 The Dispersing Agents According to the Invention 1 to 5 were used to prepare dispersions D1 to D5.

Comparative dispersing agents 6 to 9 were used to prepare comparative dispersions D6 to D9. Pre-dispersion In a 500 ml flask, Rhodoline 1010, the dispersing agent, ethylene glycol and millipore water are added in the proportions indicated in Table 3. The mixture is then homogenized with magnetic stirring. using a magnetic bar. The continuous phase is then injected with a syringe into a 500 mL "sealed" jar containing Vulcan XC 72R carbon black. In order to impregnate the carbon black, the jar is placed for 13 hours on a Roller-mill. The mixture obtained is pre-dispersed with a deflocculator 8 cm in diameter for 15 minutes at 2000 rpm. Grinding In order to grind the carbon black, 500 ml jar containing 1/3 (by volume) of the mixture is added to the Burundum® zirconium grinding balls (approximately 2.5 g of beads per gram of premix). ). The jar is then placed on the roller-mill to ensure the movement of the balls for 8 hours. In the same way, dispersions D6 to D9 were prepared using dispersing agents 6 to 9 respectively.

Table 3: Dispersions D1 to D9 Components (3/0 by mass to total dispersing agent 4`) / 0 (1, 2, 3, 4, 5, 6, 7, 8 or 9) Rhodoline 1010 0.1% Ethylene glycol 13.6% Water 66.3% Vulcan XC 72R 16% Evaluation of the ink A and dispersions B and D1 to D9 The evaluation of the dispersions obtained after grinding is done at two stages during the preparation protocol: the viscosity of the mixture is measured after the pre-dispersion step, using a Brookfield LVT 8500 (axis 3 at 60 rpm): if the viscosity of the mixture is between 10 and 1000 cP (i.e. say that the mixture is not too viscous), the mixture will allow the movement of the balls during grinding, the Hegman gauge value is measured after grinding in a jar. The results of these tests carried out on the reference ink A, the reference dispersion B, on the dispersions according to the invention D1 to D5, and on the comparative dispersions D6 to D9 are indicated in Table 4.

Table 4: Heqman Viscosity and Gauge Tests Dispersion Viscosity test Hegman gauge value Ink A Solid gel (can not be milled) = 260 cP 7.5 D1 q = 680cP 7 D2 q = 175cc 7 D3 q = 280cP 7 D4 q = 5OcP 7 D5 1-1 = 280cP 7.75 D6 7 D7 1-1 = 700 cP 7.75 D8 1-1 = 530cP 7.75 D9 q = 840cP 7 * in this case, the viscosity It could be measured because the mixture was not homogeneous after the impregnation step. The reference ink formulation A does not make it possible to carry out a jar grinding. Indeed, the viscosity of the mixture is too high, which prevents the movement of the grinding balls. For the reference dispersion B, the dispersions according to the invention D1 to D5 and the dispersions D6 to D9, the viscosity of the mixtures obtained after the impregnation step allows the grinding in a jar with balls (less than 1000 cP) and the dispersions obtained after grinding have a satisfactory gauge value (greater than 7). In addition, the dispersions are stable for at least one week.

Example 4: Preparation of diluted non-catalytic ink-jet inks EdB, Ed1 to Ed6 diluted inks, low dry extract, were prepared from the reference dispersion B or one of the dispersions D1 to D6, and the Nafion® DE 520 ionomer solution, according to the proportions given in Table 5.

The solution of Nafion® DE 520 (5 g) is diluted with 5 g of millipore water. The dispersion (2.75 g of B, D1, D2, D3, D4, D5 or D6) is itself diluted with 5 g of millipore water. The diluted solution of Nafion® DE 520 is added to the diluted carbon black dispersion. Table 5: Diluted inks EdB Ed1 to Ed6 Components (3/0 by mass relative to total Dispersing agent 0.83% (Triton X100, 1, 2, 3, 4, 5 or 6) Rhodoline 1010 0.015% Ethylene glycol 2.11 % Nafion® 1.41% Propanol 14.1% Water 79.07% Vulcan XC 72R 2.48% Solids 4.72 PVC 66.2 Concentration pigment volume (PVC) is the ratio of the volume of carbon black and the sum of the volumes of carbon black and ionomer (the density of the Vulcan XC72 R is 1.8 and the density of the Nafion® is 2.) Evaluation of the diluted inks for inkjet The inks are evaluated in If no aggregate is observed when spreading the ink on the gauge, the ink has a good dispersion quality.The results of these tests showed that the ink EdB and Ed6 have agglomerates, while Ed1 to Ed3 inks do not have agglomerates.

EXAMPLE 5 Preparation of concentrated non-catalytic inks for screen printing Concentrated inks E, B and E, 1 to E, 9, with a high solids content were prepared from the reference dispersion B or one of the dispersions D1 to D9, and the Nafion® DE 2020 ionomer solution, in the proportions shown in Table 7.

The solution of Nafion® DE 2020 (2.15 g) is added using a syringe to the dispersion (7.84 g of B, D1, D2, D3, D4, D5, D6, D7, D8 or D9) with stirring. The mixture is stirred for 30 minutes.

Table 7: Concentrated inks E, B and E, 1 to E, 9 Components (3/0 by mass relative to total Triton X100 or Dispersant 1 to 9 5.02% Rhodoline 1010 0.08% Ethylene glycol 10.67% Nafion® 4.52% Propanol 9.79% Water 57.36% Vulcan XC 72R 12.56% Solids content 22.1 PVC 76 Evaluation of concentrated inks E, B and E, 1 to E9 The corresponding inks and dispersions are evaluated by the dry route.

Thus, the ink is deposited using a film-puller of 80 lm liquid thickness and then dried for 24 hours in the open air and at room temperature and the gloss is measured at 85 ° with a gloss -Meter BYK Gardner. This measurement consists in evaluating the quality of dispersion of the ink. Indeed, the gloss of the dry film reflects the presence of aggregates, and the higher the value of the gloss, the fewer agglomerates in the sample. The results of these tests performed on dispersions B and D1 to D9, and on concentrated inks E, B and E, 1 to E, 9 are shown in Table 8.25 Table 8: Gloss tests on dispersions and inks Agent dispersant Gloss measurement dispersion silkscreen ink Triton X100 90.8 15.5 1 77.4 78.6 2 79.2 60.8 3 80.75 69.3 4 88.9 75.3 87.3 76.3 6 85 42 7 59.8 30 8 76.4 32.7 9 77.4 39 In the case of Triton X100, the dispersion B of carbon black with a gloss of 90.8 is well dispersed whereas the ink E, B corresponding is not (low gloss of 15.5). Triton X100 does not stabilize a screen printing ink containing Nafion®. In the same way, dispersions D6 to D9 are well dispersed (high gloss between about 60 and about 85), while the associated inks are not (low gloss between about 4 and about 40). Dispersants 6 to 9 do not stabilize an ink containing Nafion®. On the contrary, for dispersing agents 1 to 5, inks E, 1 to E, maintain a good dispersion quality, even after the addition of Nafion® (high gloss between about 60 and about 80). Moreover, these inks E, 1 to E, have a good particle size, with an average particle size of less than 1 μm.

Example 6: Preparation of Catalytic Dispersions D1 to D5 According to the Invention D1 to D5 catalytic dispersions were prepared using dispersing agents 1 to 5. The proportions are shown in Table 9.

Pre-dispersion In a flask with a magnetic bar, 2.34 g of ethylene glycol, 11 g of water, 0.023 g of Foamaster (anti-foam) and 1.133 g of dispersing agent according to the invention (1, 2, 3, 4 or 5). This flask is placed under magnetic stirring until complete dissolution, then 2.76 g of Tanaka TEC10V50E Pt / C (at 45.4) oPt catalytic powder are added to the previous solution. The mixture is agitated manually with a spatula and this pre-dispersion is dispersed at 1500 rpm for 30 minutes, then at 3000 rpm for 45 minutes at the dispersing disc (grinding stage).

Grinding 0.017g of Foamaster NDW (anti-foaming agent) is then added and the mixture is again dispersed to the dispersing disk at 3000 rpm for 15 min. Table 9: Catalytic dispersions D1 to 5 Components Mass (3/0 mass relative to total Dispersing agent 1 to 5 1.133 g 6.6% Foamaster NDW 0.023 g + 0.017 g 0.2% Ethylene glycol 2.34 g 13, 5% Water 11 g 63.7% Tan aka Pt / C 2.76 g 16% 20 Example 7: E aration of catalytic inks 33 Ed'l to Ed'5 according to the invention Catalytic inks Ed'1 to Ed'5 were prepared from dispersions D1 to D5, and the ionomer solution Nafion® DE 2021, in the proportions indicated in Table 10. 1.214 g of Nafion® DE2021 solution were mixed with 4.490 g of water, then the mixture is stirred magnetically until the solution is homogenized (approximately 15 min) 4.38 g of catalytic dispersion D1 to D5 are added to the diluted Nafion® solution. Magnetic stirring for 10 min and dispersed with a dispersing disc at 1500 rpm for 10 min In order to break the last remaining agglomerates, the final dispersion is ultrasonic sounding (21% amplitude) for 3 minutes. Table 10: Inks catal (3/0 mass by Components vs total dispersing agent 1 to 5 2.8% Foamaster NDW 0.1% Ethylene glycol 5.9% Nafion 2.6% Propanol 9.4% Water 72.2 % Tanaka Pt / C 6.9% Dry extract 9.59 PVC 92 Example 8: Evaluation of catalytic inks The Ed'1 catalytic ink was evaluated in terms of particle size distribution in order to see the effectiveness of the grinding, in particular with the Foamaster (antifoam) in the presence of the dispersing agent 1 according to the invention The particle size was measured with a Malvern Instrument laser particle size analyzer.It is observed a good dispersion (average particle size less than 1). The catalytic ink Ed'3 was then electrochemically characterized in order to observe the influence of the presence of the dispersing agent 3 according to the invention on its catalytic activity.The catalytic ink is previously diluted in water. ethanol (80% dilution in ethanol) and the method e Ring Rotor Electrode Characterization (ETDA) was used. The ETDA ring current measurement makes it possible to quantify the level of pollution of the catalysts contained in the ink, during measurements such as cyclic voltammetry carried out under nitrogen. For a value of% H 2 O 2 less than 1%, it is considered that the pollution of the catalyst is negligible. Figure 1 shows the evolution of the% H202 at the ETDA ring according to the type of ink used (3: standard ink without additive, to: catalytic ink Ed'3, - standard ink + Foamaster) . Compared to a so-called standard ink without additive (catalyst + ionomer solution), the results show that the values of (3/0 of H 2 O 2 are less than 1%, and more particularly lower than the value corresponding to the standard ink. of the current at the annulus of the ring-disk rotating electrode have revealed no trace of pollution at the level of the catalysts Figure 1 shows that the dispersing agent 3 according to the invention and Foamaster antifoam do not come Pollution of the platinum carbon catalysts of the PEMFC electrodes can therefore be used in PEMFC (anodic and cathodic) electrode formulations.

Identical tests have been carried out with the dispersing agents 1 to 5, and none of them causes pollution against the catalysts. The catalytic inks Ed'2 and Ed'3 were tested in fuel cell mono-cells to evaluate their electrochemical performance, to observe the influence of the presence of the dispersing agents according to the invention on the catalytic activity of the inks.

A coating table is used with a 40-μm threaded bar and the Ed'2 or Ed'3 ink is deposited on a diffusion layer. The target catalyst loadings are 0.2 mg Pt / cm2. The drying conditions of the deposit are 80 ° C for 30 min.

This deposit will serve as a cathode electrode for single-cell fuel cell tests. Indeed, the reduction of oxygen is a slow and difficult reaction, the presence of additives in the active layer can further impede this reaction. This deposit (ink on a diffusion layer, also called GDE Gas Diffusion Electrode) is then assembled with components such as a Nafion® membrane, an anodic active layer, all mounted in a fuel cell monolith including monopolar plates ( gas distributors and electric conductor) and end plates. This assembly is tested in a representative fuel cell test condition, here the so-called automotive condition 80 ° C-50 ° AHR-1.5bars-H2 / air-StH2 / air = 1.2 / 2.

The performances are characterized by polarization curves representing the evolution of the voltage (mV) as a function of the current density (mA / cm2). FIG. 2 shows the polarization curve (voltage versus current density), for a standard ink without additive (o), an ink containing the dispersing agent 2 and Foamaster antifoam (0), and a ink containing the dispersing agent 3 and Foamaster antifoam (0). The evolution curves for these three inks are substantially superimposed. Figure 2 shows that the inks containing the dispersing agents 2 and 3 according to the invention have identical performance to an ink without additive. Identical tests were performed in fuel cell monolayers with dispersing agents 1 to 5 to show that they do not alter the electrochemical performance. These results clearly show that it is possible to use the dispersing agents 1 to 5 according to the invention in PEMFC electrode inks, without impact on the electrochemical performance of the catalysts. The dispersing agents 1 to 5 according to the invention make it possible to prepare: a catalytic dispersion having a good dispersion quality, which is not the case when an additive-free ink is produced (reference A), an ink for jet d ink or for screen printing or coating containing Nafion® with a good dispersion quality contrary to reference B (Triton X100), an ink for spraying or for screen printing or coating, for PEMFC electrodes, the catalysts of which are not affected by the presence of these additives, an ink jet ink or for screen printing or coating for PEMFC electrodes, whose electrochemical performances are identical to inks without additives, thus showing the neutrality of the additives with respect to the electrochemical performances in single-cell PEMFC.

Claims (29)

REVENDICATIONS1. Use of a compound as a dispersing agent in a dispersion comprising said compound, at least one catalytic pigmentary conductor and at least one solvent, said compound comprising: an aromatic hydrophobic part, and a hydrophilic part comprising an anionic end and / or a linear chain comprising at least 12 links -OCH2CH2-. The use according to claim 1, wherein the compound is of formula ABZ, wherein: the group A- represents a phenyl or naphthyl group, optionally substituted with 1 to 5 groups independently selected from the group consisting of alkyl, linear or branched, comprising from 1 to 20 carbon atoms, and the phenyl group, optionally substituted by one or more alkyl, aryl, halogen or haloalkyl groups, the -B- group represents a single bond or a - (OCH 2 CH 2) - chain, - n is greater than or equal to 12, and the group -Z is selected from the group consisting of -OH and -SO3-1V1 +, -0SO3-1V1 + and -OP (O) (OH) (O-M ±) groups; in which IV1 + represents a counterion of positive charge. 3. Use according to claim 1, wherein the compound is of formula (1): R7A7Z1 (1) wherein: the group -A1- represents a phenylene or naphthylene radical, optionally substituted by one or more alkyl, aryl, halogen groups; or haloalkyl, the group R1- represents a linear or branched alkyl group comprising from 1 to 20 carbon atoms, optionally substituted by one or more alkyl, aryl, halogen or haloalkyl groups, and the group -Z1 represents a group -SO3 -1V11 ±, wherein M1 + is a positive charge counter-ion. 4. Use according to claim 3, wherein the compound is of formula (1 '): SO-3Na + in which the R'1- group represents a linear or branched alkyl group comprising from 10 to 20 carbon atoms, optionally substituted by one or more alkyl, alkoxy, aryl, halogen or haloalkyl groups. 5. Use according to claim 4, wherein the R'1- group represents a linear alkyl chain comprising from 10 to 20 carbon atoms. The use according to claim 1, wherein the compound is of formula (2). Z2 (2) in which: the group -Z2 is chosen from the group consisting of the -OH group and the groups -SO3-1V1 + and -OP (O) (OH) (O-M +) in which IV1 + represents a counter-ion of positive charge, the group R2- represents a linear or branched alkyl group comprising from 1 to 10 carbon atoms, optionally substituted by one or more alkyl, aryl, halogen or haloalkyl groups, n is greater than or equal to 12, and m is from 0 to 5. Use according to claim 6, wherein the compound is of formula (2 '): wherein: the group -Z'2 is selected from the group consisting of -OH, of the group -SO 3 -Na + and the group -O P (O) (OH) (O-M 1) in which 1 V 1 + represents a positive charge counter-ion, the group -R '2 represents a linear alkyl group, comprising from 1 to 6 carbon atoms, substituted by at least one phenyl group, and n is greater than or equal to 12. 8. Use according to claim 7, wherein the compound is of formula (2 "): Ph - O nZ.2 (2 ') Ph Ph in which the group --Z'2 and n are as defined in claim 7 . 9. Dispersion, comprising: at least one dispersing agent defined in any one of claims 1 to 8, at least one catalytic pigmentary conductor, and at least one solvent. The dispersion of claim 9, wherein the solvent is selected from water, an organic solvent, or mixtures thereof. The dispersion of any one of claims 9 or 10, wherein the catalytic pigment conductor comprises a surface comprising a metal selected from the group consisting of platinum, silver, palladium, ruthenium, nickel, tungsten , cobalt, osmium, molybdenum, titanium, chromium, iron, iridium, gold, tin, and their alloys. The dispersion of claim 11 wherein the metal is platinum. 13. Dispersion according to any one of claims 9 to 12, wherein the catalytic pigmentary conductor is in the form of individualized conductive particles or aggregates of conductive particles, covered with a metal layer selected from the group consisting of platinum , silver, palladium, ruthenium, nickel, tungsten, cobalt, osmium, molybdenum, titanium, chromium, iron, iridium, gold, tin, and their alloys. 14. Dispersion according to claim 13, wherein the average size in dispersion of the individualized particles or aggregates of particles is less than 5 μm, preferably less than 2 μm, preferably between 0.1 μm and 1 μm. 15. Dispersion according to any one of claims 9 to 14, wherein the mass ratio between the dispersing agent and the catalytic pigmentary conductor is 0.3 to 0.5, and preferably about 0.4. An ink formulation, comprising: a dispersion according to any of claims 9 to 15, and a proton conductive polymer. The ink formulation of claim 16, wherein the proton conductive polymer is a perfluorosulfonic acid polymer. 18. An ink formulation according to claim 17, wherein the mass proportion of proton conductive polymer is from 1% to 5% based on the total weight of the formulation. 19. An ink formulation according to any one of claims 16 to 18, wherein the mass proportion of liquid phase is from 85% to 98% based on the total weight of the formulation. 20. An ink formulation according to any one of claims 16 to 18, wherein the mass proportion of liquid phase is from 60% to 80% based on the total weight of the formulation. A process for the preparation of a dispersion according to any one of claims 9 to 15, comprising the following steps: mixing the solvent, the dispersing agent and the catalytic pigmentary conductor, and grinding the mixture obtained to obtain said dispersion. A process for preparing an ink formulation according to any one of claims 16 to 20, comprising a step of mixing the proton conducting polymer with a dispersion according to any one of claims 9 to 15. 23. Use of an ink formulation according to any one of claims 16 to 20, for the preparation of a substrate coated with a layer of catalytic pigmentary conductor. 24. Use according to claim 23 for the preparation of a proton exchange membrane fuel cell electrode. 25. A process for preparing a substrate coated with a catalytic pigmentary conductor layer, comprising the following steps; depositing an ink formulation according to one of claims 16 to 20 on a substrate, and drying the resulting substrate to obtain said coated substrate. 26. The method according to claim 25, wherein the deposition step is performed by a deposition technique selected from ink jet, coating, screen printing, spraying, flexography, gravure and the like. offset. 27. The coated substrate obtainable by the process of any one of claims 25 or 26. A proton exchange membrane fuel cell electrode comprising a coated substrate according to claim 27, said electrode being anodic or cathodic. 29. A proton exchange membrane fuel cell comprising a coated substrate according to claim 27 or an electrode according to claim 28.