Fuel cell electrode ink, preparation method for such an ink and an electrode, and fuel cell incorporating such an electrode

Abstract

Ink for fuel cell electrode, method for preparing such an ink and an electrode, and fuel cell incorporating such an electrode The invention relates to an ink capable of forming an electrode on a base membrane or a gas diffusion layer of a fuel cell, comprising a dispersion of ionomer and catalyst supported in a mixture of water, an alcohol comprising a single hydroxyl function, carried by a carbon chain, the latter comprising or not one or more aromatic cycles, and a polyalkylene glycol devoid of terminal OH functions and having a number-average molecular mass Mn of between 200 and 1000.The invention also relates to a method for preparing this ink, a method for applying it to a base membrane or a gas diffusion layer, the dried ink thus produced, the membrane or layer coated with this ink, a membrane-electrode or a membrane-electrode assembly, and a fuel cell incorporating this ink. Figure for the abstract: none.

Description

Title of the invention: Ink for fuel cell electrode, method for preparing such an ink and an electrode, and fuel cell incorporating such an electrode

[0001] The present invention relates to an ink intended to form a catalytic layer or electrode of a membrane electrode (MEA) or a membrane electrode assembly (MEA) of a fuel cell. The invention also relates to a method for preparing this ink. It further relates to the manufacture of a membrane electrode and a membrane electrode assembly of a fuel cell. It also relates to such a membrane electrode, such a membrane electrode assembly, and a fuel cell comprising at least one such electrode, such a membrane electrode, or such a membrane electrode assembly.

[0002] In the field of fuel cells, it is known to insert a stack of electrochemical cells between two end plates, located on either side of this stack in a stacking direction, and possibly to arrange this stack in a casing. The electrochemical cells are formed by membrane-electrode assemblies and bipolar plates. A membrane-electrode assembly is sometimes called MEA, from the English “Membrane-Electrode Assembly”, and generally comprises a base membrane (or proton exchange membrane), which can be coated on one or both of its faces, with a catalytic layer comprising a catalyst, as well as a frame which supports this membrane.The frame may include openings which, in the stack, define fluid flow galleries within the stack of electrochemical cells for the distribution and recovery of these fluids in the corresponding fluid compartments of each cell. This frame is most often associated with at least one seal, sometimes called a "gasket", with which it also provides a sealing function for the flow of fluids within the stack.

[0003] The membrane, when coated with catalytic layers comprising a catalyst, is sometimes called CCM, from the English “Catalyst Coated Membrane” and in this case comprises three layers, namely, a membrane itself, a catalytic layer on the anode side and a catalytic layer on the cathode side. In certain cases, the CCM comprises the membrane and a catalytic layer.

[0004] In the stack, a membrane-electrode assembly is interposed between two bipolar plates and thus delimits, between the bipolar plates, an anodic compartment on one side of the membrane-electrode assembly, in which the oxidation of the dihydrogen occurs, and a cathodic compartment on the other side, in which produces the reduction of oxygen. On each side, the catalyst-coated membrane can be covered by a gas diffusion layer which is therefore received in the corresponding anode or cathode compartment and promotes contact between the chemical species present in the corresponding anode or cathode compartment and the membrane. Each gas diffusion layer also plays a role in electron conduction. These diffusion layers are sometimes called GDL, from the English “Gas Diffusion Layer”.

[0005] It is known to manufacture a membrane-electrode assembly by attaching the catalyst-coated membrane to the frame, which in particular makes it possible to stiffen this membrane and facilitate its handling. This is done by sealingly bonding the membrane to the frame. Once this operation has been carried out, it is known to immobilize, on the pre-assembled membrane and frame, the diffusion layer(s), during an additional operation, for example by a hot pressing operation and / or by means of an adhesive.

[0006] The MEA membrane-electrode assembly therefore comprises a base membrane which is a proton exchange polymer membrane and which is coated, as previously stated, with a catalytic layer, generally on each of its two faces. This base membrane is often made of a polymer material which is an ionomer, generally a perfluorosulfonated acid ionomer or perfluorosulfonic acid (PFSA), preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether such as NAFION™, which has a very small thickness, generally less than 0.1 mm, while the catalytic layers are made from an ionomer and a supported catalyst, typically platinum supported by carbon and also of very small thickness, typically less than 0.05 mm.The deposition of these catalytic layers on the base membrane involves the use of water and volatile organic solvents, and their evaporation to leave a dry layer.

[0007] In view of the extreme thinness of both the base membrane and the catalytic layers, it is understood that the difficulty is to succeed in depositing a thin and perfectly homogeneous or continuous catalytic layer both after deposition and after drying, without the appearance in particular of imperfections such as cracks, and without the constituents of the catalytic layers, in particular water and solvents, damaging the base membrane itself at the time of application or drying. The invention therefore aims to design an ink making it possible to form one or more catalytic layers fulfilling these objectives.

[0008] Furthermore, it would be interesting to be able to apply an ink by industrial processes, for example using slot die deposition, and even making it possible to produce MEAs using a roll-to-roll process. The ink must be suitable for this type of deposition in order to obtain the extremely thin, homogeneous and continuous layer mentioned in the previous paragraph, with good adhesion to the support and good electrochemical properties.

[0009] Ideally, this ink could also be deposited on the base membrane as well as on a gas diffusion layer (GDL).

[0010] It is to these technical problems that the invention intends more particularly to address itself by proposing a new ink composition, its preparation process, and its method of implementation, making it possible to produce a stable dried ink layer, adhering to the support, homogeneous and without cracks, on the surface of a membrane or a GDL without damaging them, and having good electrochemical performances. Other objectives of the invention will appear in the remainder of the description.

[0011] To this end, the invention relates to an ink capable of forming an electrode on a proton exchange membrane or on a gas diffusion layer (GDL), intended to form a fuel cell MEA. This ink comprises a dispersion of ionomer and supported catalyst in the form of particles, in a mixture of water, an alcohol comprising a single hydroxyl function, carried by a carbon chain, the latter comprising or not one or more aromatic cycles, and a polyalkylene glycol devoid of terminal OH functions. Preferably, this polyalkylene glycol has a number-average molecular weight Ma of between 200 and 1000, preferably between 200 and 500.

[0012] In particular, the alcohol comprising a single hydroxyl function has a boiling point of between 75 and 130°C, preferably between 75 and 100°C. It is preferably 1-propanol (propan-1-ol), 2-propanol (propan-2-ol), or a mixture of the two.

[0013] In particular, the polyalkylene glycol is a polyalkylene glycol dialkyl ether. It is preferably chosen from: polyethylene glycol dimethyl ether (PEGDME), polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diglycidyl ether, polypropylene glycol / polyethylene glycol copolymer with dibutyl ether termination, polyethylene glycol / polypropylene glycol / polyethylene glycol block copolymer with dibutyl ether termination. It is preferably PEGDME. Preferably, the polyalkylene glycol chosen from this list has a number-average molecular weight Mn of between 200 and 1000, preferably between 200 and 500.

[0014] The solvent part (water, alcohol, polyalkylene glycol dialkyl ether) of the ink composition has several functions. It combines water, the majority constituent, with a low-boiling alcohol and a high-boiling solvent capable of producing a binding effect. It makes it possible to disperse the ionomer in colloidal form, while maintaining a contact between chains to allow the formation of an ionomer network, it induces an interaction between the ionomer and the catalyst, it stabilizes the dispersion. It allows to confer the appropriate viscosity for the method of application of the ink on the base membrane or the GDL. It confers an evaporation rate that is not too rapid. It allows to avoid an internal swelling of the base membrane typically comprising an ionomer.

[0015] Without wishing to be bound by theory, it is believed that the presence of polyalkylene glycol devoid of OH functions, such as PEGDME, plays a determining role in achieving the objectives that the invention has set itself, by the combination of at least two factors. The first factor is the polymer status. The second is a high boiling point reducing its volatility under operating conditions. This polymer can then play a role as a binder in the catalytic layer both in the applied ink and in the dried ink layer, and therefore makes it possible to improve the homogeneity of this layer. Advantageously, the polymer and the ionomer can contribute together to this role of binder. In addition and very advantageously, the fact of not having OH groups reduces the risk of flammability during the ink manufacturing process, during its application and during the drying step.This produces a layer of ink which has a very good affinity for the base membrane or for the GDL, with a good level of adhesion, and which presents good homogeneity, notably with the absence of cracks.

[0016] The ionomer is involved in electrochemical reactions, allowing the transport of protons and water. It also plays a role as a binder in the ink, giving the catalytic layer formed from it a certain mechanical resistance and adhesion properties to the base membrane or to the GDL, which combine advantageously with the properties provided by the polyalkylene glycol devoid of OH functions.

[0017] In particular, the ionomer comprises or consists of a perfluorosulfonated acid or perfluorosulfonic acid (PFSA) ionomer. It is in particular formed from a polytetrafluoroethylene backbone carrying side chains terminated by sulfonic acid groups. The ionomer used is preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether. Mention may be made of Nafion® and Aquivion®. These copolymers are known to be characterized by so-called long side chains (LSC for “long side chain”), an example being Nafion®, or by so-called short side chains (SSC for “short side chain”), an example being Aquivion®. These PFSA ionomers are also defined by their equivalent weight or “Equivalent Weight” in English (EW), representing the ratio of grams of polymer / moles of sulfonate (“grams polymer / mole sulfonate”). Nafion® has a high EW, between 1000 and 1100; Aquivion® has a low EW, between 720 and 790.

[0018] The catalyst comprises or consists of a noble metal, several noble metals or an alloy of noble metals. This metal, these metals or this alloy of metals is associated with a carbon support to form the catalyst.

[0019] The noble metal is in particular selected from: platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), gold (Au), osmium (Os), rhodium (Rh), osmium (Os), tungsten (W), lead (Pb), iron (Fe), chromium (Cr), cobalt (Co), nickel (Ni), manganese (Mn), vanadium (V), molybdenum (Mo), gallium (Ga), aluminum (Al) or any other metal having catalytic activity. Alloys of two or more of these metals include platinum (Pt)-palladium (Pd) alloys, platinum (Pt)-ruthenium (Ru) alloys, platinum (Pt)-iridium (Ir) alloys, platinum (Pt)-osmium alloys, platinum (Pt)-M alloys (M being Ti, V, Cr, Mo, W, Mn, Fe, Co, Rh, Ni, Cu, Ag, Au, Zn, Ga and / or Sn) or a combination thereof.

[0020] The noble metal or noble metal alloy is combined with a carbon support to form what is called the supported catalyst. The carbon support may comprise or consist of: carbon black, activated carbon, carbon powder, acetylene black, ketjen black, carbon nanotubes, carbon nanofibers, carbon nanocomes, carbon beads, carbon nanowires, carbon nanocomets, carbon aerogels, carbon crerogels or carbon nanorings, or a mixture of two or more of these elements.

[0021] Advantageously, the catalyst comprises or consists of a platinum-based catalyst supported by a carbon support. The catalyst may also comprise or consist, for example, of an alloy of platinum and cobalt supported by a carbon support (PtCo / C).

[0022] In one embodiment, the platinum or the platinum and cobalt alloy is supported on carbon nanoparticles. These may be carbon nanoparticles with a high specific surface area, and the metal or alloy is essentially located on the surface of the nanoparticles. They may also be porous carbon nanoparticles, and the metal or alloy is found in whole or in part in the pores of the nanostructure. The support nanoparticles, in particular made of carbon, have a nanometric size which may be between 10 and 100 nm.

[0023] The noble metal, in particular platinum or the platinum and cobalt alloy, can be in the form of nanoparticles. These nanoparticles have a nanometric size which can be between 1 and 10 nm.

[0024] The mass proportions of the different ingredients in the ink according to the invention may be, relative to the total mass of the ink resulting from this mixture: from 55 to 70% of water, from 2 to 15% of polyalkylene glycol devoid of OH functions, from 7 to 20% of alcohol comprising a single hydroxyl function, from 2 to 8% of ionomer, and from 5 to 7% of supported catalyst. According to a preferred method, in particular when uses PEGDME as a polyalkylene glycol devoid of OH functions, the following mass proportions are retained, relative to the total mass of the ink resulting from this mixture: from 61 to 69% water, from 2 or 4 to 14% polyalkylene glycol, from 7, 10 or 15 to 20% alcohol, from 3 to 6% ionomer, and from 5 to 7% supported catalyst. More preferably, it is a mixture: from 62 to 66% water, from 5 to 11% polyalkylene glycol, from 17 to 19% alcohol, from 3 to 4% ionomer, and from 5.5 to 6.5% supported catalyst. A typical example for PEGDME is: about 63.1% water, about 9% PEGDME, about 18% alcohol, about 3.7% ionomer, and about 6.2% supported catalyst.

[0025] The invention also relates to a method for preparing an ink capable of forming an electrode on a fuel cell membrane, in particular an ink as mentioned above, comprising:

[0026] form a dispersion by mixing i. an ionomer or polymer electrolyte, ii. water, iii. an alcohol comprising a single hydroxyl function, carried by a chain carbonaceous, this one including or not one or more aromatic cycles, and iv. a polyalkylene glycol devoid of terminal OH functions and having a number-average molecular mass Mn of between 200 and 1000, preferably between 200 and 500, v. a supported catalyst in the form of particles.

[0027] Preferably, this method comprises the following steps: a. Form a first dispersion A by mixing i., ii., iii., and iv., b. Form a second dispersion B by mixing ii., iii., iv., and v.,

[0028] alcohol iii. and polyalkylene glycol iv. which may be identical or different in dispersions A and B, a. mixing the two dispersions A and B, stirring, and obtaining the ink in the form of a dispersion of the ionomer i. and the supported catalyst v. in the mixture of water ii., alcohol iii. and polyalkylene glycol iv.

[0029] The compounds entering into the composition of the ink and used in this method under i., ii., iii., iv., and v. have been defined previously in the description of the inks according to the invention.

[0030] The method uses in particular, as alcohol iii.: 1-propanol, 2-propanol, or a mixture of the two, and / or as polyalkylene glycol iv.: polyethylene glycol dimethyl ether (PEGDME), and / or as ionomer i. a perfluorosulfonated acid or perfluorosulfonic acid (PFSA) ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether, and / or, as supported catalyst, carbon particles supporting platinum and / or cobalt.

[0031] According to a preferred method, in step a., the following mass proportions are used, relative to the total mass of dispersion A: from 55 to 70% of water, from 2 to 15% of polyalkylene glycol iv., from 10 to 35% of alcohol iii., and from 8 to 20% of ionomer i. According to an even more preferred method, in particular when PEGDME is used as ingredient iv., in step a., the following mass proportions are used, relative to the total mass of dispersion A: from 58 to 69% of water, from 2 to 14% of polyalkylene glycol iv., from 12 to 20% of alcohol iii., and from 8 to 17% of ionomer i. A typical example for PEGDME is: about 63.1% water, about 9.1% PEGDME iv., about 18% alcohol iii., and about 9.8% ionomer i.

[0032] According to a preferred method, in step b., the following mass proportions are used, relative to the total mass of dispersion B: from 55 to 70% of water, from 1 to 15% of polyalkylene glycol iv., from 15 to 25% of alcohol iii., and from 6 to 13% of supported catalyst v. According to an even more preferred method, in particular when PEGDME is used as ingredient iv., in step b., the following mass proportions are used, relative to the total mass of dispersion B: from 62-70% of water, from 5 to 11% of polyalkylene glycol iv., from 17 to 20% of alcohol iii., and from 8 to 11% of supported catalyst v. A typical example for PEGDME is: about 63.1% water, about 9% PEGDME iv., about 18% alcohol iii., and about 9.9% supported catalyst v.

[0033] According to a preferred method, in step c., the dispersions A and B are mixed so as to obtain the following mass proportions, relative to the total mass of the ink resulting from this mixture: from 55 to 70% of water, from 2 to 15% of polyalkylene glycol iv., from 7 to 20% of alcohol iii., 2 to 8% of ionomer i. and from 5 to 7% of supported catalyst v. According to an even more preferred method, in particular when PEGDME is used as ingredient iv., the dispersions A and B are mixed so as to obtain the following mass proportions, relative to the total mass of the ink resulting from this mixture: from 61 to 69% of water, from 2 or 4 to 14% of polyalkylene glycol iv., from 7, 10 or 15 to 20% of alcohol iii., from 3 to 6% of ionomer i. and from 5 to 7% of supported catalyst v. More preferably, it is a mixture: from 62 to 66% of water, from 5 to 11% of polyalkylene glycol, from 17 to 19% of alcohol, from 3 to 4% of ionomer, and from 5.5 to 6.5% of supported catalyst.A typical example for PEGDME is: about 63.1% water, about 9% PEGDME iv., about 18% alcohol iii., about 3.7% ionomer i. and about 6.2% supported catalyst v. .

[0034] Each dispersion, and the mixing of dispersions A and B can be carried out using a mechanical mixer, in particular a disperser, in particular an industrial disperser of the Ultra Turrax® type. The mixing can in particular be carried out at a temperature of between 15 and 50°C.

[0035] The invention also relates to an ink obtained by implementing the preparation method described herein. This ink is capable of forming an electrode on a base membrane or a fuel cell GDL.

[0036] The invention also relates to a dried ink, capable in particular of constituting or constituting a catalytic layer or electrode on a base membrane or a GDL of a fuel cell, comprising an ionomer, a supported catalyst, and a polyalkylene glycol devoid of terminal OH functions. The latter has in particular a number-average molecular mass Mn of between 200 and 1000, preferably between 200 and 500.

[0037] This dried ink comprises in particular: a polyalkylene glycol dialkyl ether, preferably chosen from: polyethylene glycol dimethyl ether (PEGDME), polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diglycidyl ether, polypropylene glycol / polyethylene glycol copolymer with dibutyl ether termination, polyethylene glycol / polypropylene glycol / polyethylene glycol block copolymer with dibutyl ether termination, preferably PEGDME; and / or a perfluorosulfonic acid or perfluorosulfonic acid (PFSA) ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether; and / or a supported catalyst formed from carbon particles supporting platinum and / or cobalt.

[0038] The invention also relates to a membrane-electrode which comprises a fuel cell base membrane. This membrane is a proton exchange polymer membrane, carrying on one or both of its faces a catalytic layer formed from an ink as described here, dried, or a catalytic layer as obtained by implementing the method for forming such a layer as described here. The base membrane comprises or is made of a polymeric or ionomeric material, especially a perfluorosulfonated acid or perfluorosulfonic acid (PFSA) polymer or ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether such as NAFION® or Aquivion®.

[0039] More specifically, a first catalytic layer forms the cathode and a second catalytic layer forms the anode.

[0040] The catalytic layer(s) have a thickness of the order of 0.001 to 0.010 mm.

[0041] The catalytic layer(s) generally have a supported catalyst loading of approximately 0.1 to 0.5 mg / cm2.

[0042] The invention also relates to a membrane-electrode assembly which comprises a fuel cell base membrane, or proton exchange polymer membrane, carrying on one or both of its faces a catalytic layer formed from an ink as described herein, dried, or a catalytic layer as obtained by carrying out the method of forming such a layer as described herein.

[0043] In particular, the base membrane comprises or is made of a polymeric material, in particular a perfluorosulfonic acid or perfluorosulfonic acid (PFSA) ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether such as NAFION®. The membrane thus coated can be held in a frame, thus forming the membrane-electrode assembly.

[0044] More specifically, a first catalytic layer forms the cathode and a second catalytic layer forms the anode.

[0045] The catalytic layer(s) have a thickness of the order of 0.001 to 0.010 mm.

[0046] According to one characteristic, this base membrane comprises or is made of a polymer material which is a perfluorosulfonated acid ionomer or perfluorosulfonic acid (PFSA), preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether such as NAFION™. It may in particular have a thickness of the order of 0.005 to 0.050 mm.

[0047] This base membrane may optionally be composed of several layers, one of which contains a perfluorosulfonic acid or perfluorosulfonic acid (PFSA) ionomer, alone or in association with one or more materials, of a polymeric nature or not.

[0048] A gas diffusion layer (GDL) is a porous and electrically conductive medium. It may be made, in particular, of carbon fibers which are woven or knitted together or are in the form of a non-woven or matt textile. According to one characteristic, a GDL may be treated to give it an additional property, such as hydrophobicity with a coating of hydrophobic polymer (PTFE for example), loaded with particles or carbon fibers to maintain the electrically conductive character.

[0049] The invention then relates to a GDL carrying on one of its faces a catalytic layer formed from an ink as described here, dried, or a catalytic layer as obtained by implementing the method for forming such a layer as described here. The catalytic layer has a thickness of the order of 0.001 to 0.010 mm.

[0050] The invention therefore also relates to a membrane-electrode or a membrane-electrode assembly associating at least one base membrane carrying a catalytic layer according to the invention, and a GDL carrying a catalytic layer according to the invention. The base membrane carries a catalytic layer on a first face, the second face being devoid of it. The GDL carries a catalytic layer on a first face. It is by this face carrying the catalytic layer that the GDL is applied to the base membrane, on the second face of the latter, devoid of catalytic layer.

[0051] The invention also relates to a fuel cell comprising several of these membrane-electrode or membrane-electrode assemblies.

[0052] The invention also relates to a method for forming a catalytic layer on the surface of a base membrane or a GDL of a fuel cell, and, preferably, on a sheet from which base membranes or GDLs will then be cut to the required dimensions. It may be a large sheet usable in a roll-to-roll process, typically a sheet from a supply roll (or reel) passing through the coating station before being wound onto a receiving roll (or reel). It may also be a sheet of smaller dimensions, for a sheet-to-sheet process.

[0053] The catalytic layer is formed by coating, comprising the deposition of a layer of ink according to the invention, then its drying. The coating or deposition of the ink is preferably carried out by techniques for depositing the dispersion by application means allowing the deposition of the dispersion on the supports across the direction of advancement thereof. This can be carried out in particular using a slot die, a doctor blade or a bar coater. For coating on both sides, the sheet will be turned over to apply the ink in the same way on the opposite side. This will involve, for example, unwinding the sheet from the receiving roll, winding it onto another roll; then, the sheet will be unwound again to apply the ink to the other side. The sheet coated with a catalytic layer on its two sides will then be received on a receiving roll, before being cut to size.Traditionally, the sheet is covered with a backing film, particularly PET, which must therefore be removed before applying the ink.

[0054] The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of embodiments of catalytic inks and their application to a base membrane for a fuel cell, given solely by way of example. Example 1

[0055] Step 1. Dilution of the ionomer

[0056] 4.54 grams of ionomer (sold under the brand name Aquivion®) are introduced into a 50 milliliter bottle, with 3.93 grams of deionized water, 2.10 grams of 1-propanol (Fisher, purity greater than 99%), and 1.05 grams of PEGDME (Sigma). This ionomer dilution is stirred by a magnetic stirrer for 1 hour.

[0057] Step 2. Dispersion of the catalyst

[0058] In a beaker, 2.47 grams of Pt / C catalyst (high surface area carbon) are mixed with 15.62 grams of deionized water, then mixed by a magnetic stirrer at room temperature. In a 150 milliliter beaker, 2.47 grams of Pt / C catalyst (high surface area carbon) are mixed with 15.62 grams of deionized water, then mixed by a magnetic stirrer at room temperature. With vigorous stirring, 4.44 grams of 1-propanol and 2.21 grams of PEGDME are introduced into the beaker. This dispersion containing the catalyst is stirred for 30 minutes at 1000 rpm by a dissolver.

[0059] Step 3. Preparing the ink

[0060] 11.05 grams of the ionomer dilution prepared in step 1 and 18.53 grams of the catalyst-containing dispersion prepared in step 2 are mixed in a 150 milliliter bottle for 30 minutes at 24,000 rpm by a rotor-stator mixer. The ink is then characterized by rheology to check whether it is suitable for the deposition process. The rheological measurement consists of a viscosity measurement, at a shear rate between 0.01 and 1000 s 1 (per second) and at a temperature of 20°C. The ink has a shear-thinning behavior and has a viscosity of 1 pascal second for a shear rate of 1 s 1 (per second), measured at a temperature of 20°C.

[0061] Step 4. Depositing the ink

[0062] The ink is deposited on a membrane (M775.15, Gore) using a bar coater. The desired amount of platinum is between 0.3 and 0.5 milligrams of platinum per square centimeter of membrane. In order to evaporate the solvent, the ink-coated membrane is heated to 40°C for several minutes. Example 2

[0063] Step 1. Dilution of the ionomer

[0064] 30.3 grams of ionomer (sold under the brand name Aquivion®) are introduced into a 150 milliliter bottle, with 26.4 grams of deionized water, 14.2 grams of 2-propanol (Fisher, purity greater than 99%), and 6.3 grams of PEGDME (Sigma). This ionomer dilution is stirred by a magnetic stirrer for 1 hour.

[0065] Step 2. Dispersion of the catalyst

[0066] In a 250 milliliter beaker, 12.7 grams of Pt / C catalyst (high surface area carbon) are mixed with 80.1 grams of deionized water, then mixed by a magnetic stirrer at room temperature. With vigorous stirring, 23.3 grams of 2-propanol and 10.3 grams of PEGDME are introduced into the beaker. This dispersion containing the catalyst is stirred for 15 minutes at 200 rpm by a propeller.

[0067] Step 3. Preparing the ink

[0068] 73.6 grams of the ionomer dilution prepared in step 1 and the entire The dispersion containing the catalyst prepared in step 2 is mixed in a 250 milliliter bottle for 30 minutes at 15,000 rpm by a rotor-stator mixer. The ink is then characterized by rheology to check if it is suitable for the deposition process. The rheological measurement consists of a viscosity measurement, at a shear rate between 0.01 and 1000 s 1 (per second) and at a temperature of 20°C. The ink has a shear-thinning behavior and has a viscosity of 1 pascal second for a shear rate of 1 s 1 (per second), measured at a temperature of 20°C.

[0069] Step 4. Depositing the ink

[0070] The ink is deposited on a membrane (M775.15, Gore) using a bar coater. The desired amount of platinum is between 0.3 and 0.5 milligrams of platinum per square centimeter of membrane. In order to evaporate the solvent, the ink-coated membrane is heated to 40°C for several minutes. Example 3

[0071] Step 1. Dilution of the ionomer

[0072] 30.4 grams of ionomer (sold under the brand name Aquivion®) are introduced into a 150 milliliter bottle, with 27.9 grams of deionized water, 14.6 grams of 2-propanol (Fisher, purity greater than 99%), and 4.4 grams of PEGDME (Sigma). This ionomer dilution is stirred by a magnetic stirrer for 1 hour.

[0073] Step 2. Dispersion of the catalyst

[0074] In a 250 milliliter beaker, 12.7 grams of Pt / C catalyst (high surface area carbon) are mixed with 82.7 grams of deionized water, then mixed by a magnetic stirrer at room temperature. With vigorous stirring, 23.9 grams of 2-propanol and 7.2 grams of PEGDME are introduced into the beaker. This dispersion containing the catalyst is stirred for 15 minutes at 200 rpm by a propeller.

[0075] Step 3. Preparing the ink

[0076] 73.6 grams of the ionomer dilution prepared in step 1 and the entire The dispersion containing the catalyst prepared in step 2 is mixed in a 250 milliliter bottle for 30 minutes at 15,000 rpm by a rotor-stator mixer. The ink is then characterized by rheology to check if it is suitable for the deposition process. The rheological measurement consists of a viscosity measurement, at a shear rate between 0.01 and 1000 s 1 (per second) and at a temperature of 20°C. The ink has a shear-thinning behavior and has a viscosity of 1 pascal second for a shear rate of 1 s 1 (per second), measured at a temperature of 20°C.

[0077] Step 4. Depositing the ink

[0078] The ink is deposited onto a membrane (M775.15, Gore) using a bar coater. The desired amount of platinum is between 0.3 and 0.5 milligrams of platinum per square centimeter of membrane. In order to evaporate the solvent, the ink-coated membrane is heated to 40°C for several minutes. Results:

[0079] In the 3 examples, the ink deposition was made on a membrane with a surface area of ​​36 cm2 and drying did not raise any flammability problems. The appearance of the ink layers was observed with the naked eye; the surface appearance was homogeneous with little or no cracking. The electrochemical performances proved satisfactory: > 0.65 V at 1 A / cm2.

Claims

Claims

1. Ink capable of forming an electrode on a base membrane or a gas diffusion layer of a fuel cell, comprising a dispersion of ionomer and supported catalyst in the form of particles, in a mixture of water, an alcohol comprising a single hydroxyl function, carried by a carbon chain, the latter comprising or not one or more aromatic cycles, and a polyalkylene glycol devoid of terminal OH functions and having a number-average molecular mass Mn of between 200 and 1000, preferably between 200 and 500, the polyalkylene glycol being chosen from: polyethylene glycol dimethyl ether (PEGDME), polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diglycidyl ether, polypropylene glycol / polyethylene glycol copolymer with dibutyl ether termination,polyethylene glycol / polypropylene glycol / polyethylene glycol block copolymer with dibutyl ether termination.,

2. Ink according to claim 1, wherein the alcohol has a boiling point between 75 and 130°C, preferably between 75 and 100°C.

3. V-. Ink according to claim 1 or 2, wherein: a. the alcohol is 1-propanol, 2-propanol, or a mixture of the two, and / or b. the polyalkylene glycol is polyethylene glycol dimethyl ether (PEGDME).

4. An ink according to any one of claims 1 to 3, wherein: a. the ionomer comprises or consists of a perfluorosulfonated acid or perfluorosulfonic acid (PFSA) ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether, and / or b. the supported catalyst comprises carbon particles supporting platinum and / or cobalt.

5. Ink according to any one of claims 1 to 4, in which the mass proportions of the different ingredients are, relative to the total mass of the ink resulting from this mixture: from 55 to 70% water, from 2 to 15% polyalkylene glycol devoid of OH functions, from 7 to 20% alcohol comprising a single hydroxyl function, from 2 to 8% ionomer, and from 5 to 7% supported catalyst.

6. Method for preparing an ink capable of forming an electrode on a fuel cell membrane, comprising: forming a dispersion by mixing i. an ionomer, ii. water, iii. an alcohol comprising a single hydroxyl function, carried by a carbon chain, the latter comprising or not one or more aromatic cycles, and iv.a polyalkylene glycol devoid of terminal OH functions and having a number-average molecular mass Mn of between 200 and 1000, preferably between 200 and 500, the polyalkylene glycol being chosen from: polyethylene glycol dimethyl ether (PEGDME), polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diglycidyl ether, polypropylene glycol / polyethylene glycol copolymer with dibutyl ether termination, polyethylene glycol / polypropylene glycol / polyethylene glycol block copolymer with dibutyl ether termination, v. a supported catalyst in the form of particles.

7. A method according to claim 6, comprising a. forming a first dispersion A by mixing i., ii., iii., and iv., b. forming a second dispersion B of ii., iii., iv., and v., alcohol iii. and polyalkylene glycol iv. which may be the same or different in dispersions A and B, a. mixing the two dispersions, stirring, and obtaining the ink in the form of a dispersion of the ionomer i. and the supported catalyst v. in the mixture of water ii., alcohol iii. and polyalkylene glycol iv.

8. A method according to claim 6 or 7, wherein the alcohol iii. has a boiling point of between 75 and 130°C, preferably between 75 and 100°C.

9. A method according to any one of claims 6 to 8, wherein: a. the alcohol iii. is 1-propanol, 2-propanol, or a mixture of both, and / or b. the polyalkylene glycol iv. is polyethylene glycol dimethyl ether (PEGDME).

10. A method according to any one of claims 6 to 9, wherein: a. the ionomer i. comprises or consists of a perfluorosulfonated acid or perfluorosulfonic acid (PFSA) ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether, and / or b. the supported catalyst comprises carbon particles supporting platinum and / or cobalt.

11. Method according to any one of claims 6 to 10, in which, in step a., the following mass proportions are used, relative to the total mass of dispersion A: from 55 to 70% of water, from 2 to 15% of polyalkylene glycol iv., from 10 to 35% of alcohol iii., and from 8 to 20% of ionomer i.

12. Method according to any one of claims 6 to 11, in which, in step b., the following mass proportions are used, relative to the total mass of dispersion B: from 55 to 70% of water, from 1 to 15% of polyalkylene glycol iv., from 15 to 25% of alcohol iii., and from 6 to 13% of supported catalyst v.

13. Method according to any one of claims 6 to 12, in which, in step c., the dispersions A and B are mixed so as to obtain the following mass proportions, relative to the total mass of the ink resulting from this mixture: from 55 to 70% of water, from 2 to 15% polyalkylene glycol iv., 7-20% alcohol iü., and 2-8% ionomer i. and 5-7% supported catalyst v.

14. Dried ink capable of constituting or constituting a catalytic layer or electrode on a fuel cell membrane, comprising an ionomer, a supported catalyst in the form of particles, and a polyalkylene glycol devoid of terminal OH functions and having a number-average molecular mass Mn of between 200 and 1000, preferably between 200 and 500, the polyalkylene glycol being chosen from: polyethylene glycol dimethyl ether (PEGDME), polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diglycidyl ether, polypropylene glycol / polyethylene glycol copolymer with dibutyl ether termination, polyethylene glycol / polypropylene glycol / polyethylene glycol block copolymer with dibutyl ether termination.

15. The dried ink of claim 14, wherein: a. the polyalkylene glycol is PEGDME, and / or b. the ionomer comprises or consists of a perfluorosulfonated acid or perfluorosulfonic acid (PFSA) ionomer, preferably a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether, and / or c. the supported catalyst comprises carbon particles supporting platinum and / or cobalt.

16. A method of forming a catalytic layer on the surface of a base membrane or a gas diffusion layer of a fuel cell, comprising depositing an ink layer according to any one of claims 1 to 5, on this surface using a slot die, a doctor blade or a bar coating machine, preferably in a roll-to-roll process.

17. Fuel cell membrane electrode or membrane electrode assembly, which comprises a fuel cell base membrane carrying on one or both of its faces a catalytic layer

18.

19. formed from a dried ink according to claim 14 or 15, or a catalytic layer as obtained by applying and drying an ink according to any one of claims 1 to 5. Membrane-electrode or membrane-electrode assembly of a fuel cell according to claim 17, in which the base membrane carries a catalytic layer on a first face, the second face being devoid thereof, the membrane-electrode further comprising a gas diffusion layer, one face of which is applied to this second face of the base membrane and the other face of which carries a catalytic layer formed from a dried ink according to claim 14 or 15, or a catalytic layer as obtained by applying and drying an ink according to any one of claims 1 to 5. Fuel cell comprising a membrane electrode or a membrane electrode assembly according to claim 17 or 18.