Fuel cell and electric generator comprising such a fuel cell

Abstract

The invention relates to a fuel cell comprising a proton exchange membrane (1) covered by a nanostructured anode electrode (2) and by a nanostructured cathode electrode (3). An anode current collector (4) and a cathode current collector (5) are respectively in contact with the anode electrode (2) and with the cathode electrode (3). The current collectors are porous as well as electrically and thermally conductive. The current collectors define a portion of the supply channels that connect the cathode electrode to an oxygen source and the anode electrode to a hydrogen source. The anode electrode (2) is fixedly mounted on the cathode current collector (5). The cathode current collector introduces a pressure loss such that the flow rate of the oxygen supply channel is at least five times greater than the flow rate in the cathode electrode (3).

Description

FUEL CELL AND ELECTRIC GENERATOR CONTAINING SUCH A FUEL CELL

[0001] The invention relates to a fuel cell and an electric generator comprising at least the fuel cell.

[0002] In a fuel cell, hydrogen is oxidized at the anodic electrode and oxygen is reduced at the cathodic electrode. The fuel cell typically consists of a proton exchange membrane, one side of which is covered by the anodic electrode and the other by the cathodic electrode. The electrodes contain catalytic materials, usually platinum, which are electrically connected to one of the current collectors to receive or emit electrons and are also connected to the proton exchange membrane by an ionic conductor or are in direct contact with it.

[0003] In addition to the electrodes, it is advantageous to have current conductors in electrical contact with the electrodes that possess good electrical conductivity to ensure efficient transfer of electrical charge carriers to the fuel cell's output terminals. These output terminals are designed to supply power to an electrical load, such as a motor, an electronic device, or any other appliance that operates using an electric current.

[0004] In order to supply an electric current, the fuel cell must be supplied with gas on both sides of the membrane. Conventionally, the anodic and cathodic electrodes are covered by a gas diffusion layer (GDL), which is porous and electrically conductive. The gas diffusion layer connects the current collector and the electrode.

[0005] The gas diffusion layer is typically a carbon felt. This carbon felt is porous enough to supply the fuel cell without introducing a pressure drop for the reactive gas volumes, thus generating redox reactions. It also exhibits a sufficiently low electrical resistance along the direction through the stack to allow current to reach a current collector. The current collector is a layer with higher electrical conductivity to avoid introducing significant series resistance. Typically, the current collector is a metallic layer.

[0006] The current collector has or defines a gas flow channel to supply the gas diffusion layer. The gas diffusion layer is configured to provide good gas diffusion along directions parallel to the interfaces between the membrane and the catalytic layers, thus utilizing the entire available surface area of ​​the catalyst material. The gas diffusion layer has low electrical conductivity, which encourages its reduction in thickness to avoid hindering current flow to the current collector.

[0007] During the redox reaction, a significant amount of heat is generated, along with the production of water. This heat must be removed from the fuel cell to prevent the temperature of its multiple layers from exceeding the degradation temperature. It is also necessary to remove some of the water to avoid saturating the surface of the catalytic layer and thus preventing the redox reaction from slowing down or even stopping. It is equally important not to remove all the water produced, as this could dry out the proton exchange membrane and risk its degradation.

[0008] When defining the components of a fuel cell, it is important to look for a configuration that must simultaneously ensure the supply of a large quantity of gas in order to deliver a large power output, allow the evacuation of reaction by-products and exhibit low electrical resistance.

[0009] It appears that the layers forming the fuel cell are subject to numerous compromises between their electrical performance, their thicknesses, their ability to allow or block a flow of gas, as well as their degradation temperatures and thermal conductivities.

[0010] The use of a carbon felt gas diffusion layer requires the application of a significant compression force between the two current collectors in order to have good sealing of the cell against gases and good contact between the different layers to ensure heat dissipation and current flow.

[0011] All these technical constraints make this configuration difficult to implement because sufficient compressive force must be applied between the two current collectors to achieve good electrical contact, but the gas diffusion layer must not be compressed too much to avoid blocking the gas flow, which reduces the power output. Furthermore, it appears that all these technological constraints tend to result in fuel cells with a relatively short lifespan. Object of the invention

[0012] One object of the invention is to provide a fuel cell whose configuration is simpler than that of prior art configurations in order to improve its durability and / or performance.

[0013] We tend to solve this problem by means of a fuel cell comprising: - a proton exchange membrane having an anodic face and an opposite cathodic face; - an electrically conductive anodic current collector and a cathodic current collector; - an anodic electrode electrically connected to the anodic current collector and a cathodic electrode electrically connected to the cathodic current collector; in which at least one of the anodic electrode and the cathodic electrode comprises electrically conductive nanotubes and / or nanowires, the nanowires and / or nanotubes extending predominantly in a direction perpendicular to the anodic face and / or the cathodic face; in which the nanowires and / or nanotubes are at least partially coated with a catalyst material; in which an ionically conductive layer connects the proton exchange membrane and the catalyst material.

[0014] The fuel cell is remarkable in that the cathode current collector is an open-pore metallic foam, the cathode current collector being in direct contact with the nanowires and / or nanotubes and exhibiting a compressive strength greater than the compressive strength of the cathode electrode and greater than the compressive strength of the proton exchange membrane.

[0015] In a particular configuration, the nanowires and / or nanotubes have an average diameter that is identical to the average diameter of the pores.

[0016] Preferably, the cathode current collector is at least partially covered by a layer of hydrophobic material.

[0017] According to one embodiment, the average size of the surface pores is less than 10 microns.

[0018] Preferably, the cathode current collector comprises particles of catalyst material and / or a coating of catalyst material ionically connected to the proton exchange membrane by the conductive ionic layer.

[0019] Advantageously, the cathode current collector is fixedly mounted with the cathode electrode to form a monolithic assembly deforming uniformly in one or more directions parallel to the interface between the cathode current collector and the cathode electrode.

[0020] Advantageously, the nanotubes and / or nanowires are curved and define a proximal part having a longitudinal axis perpendicular to a face of the cathode current collector fixing the nanotubes and / or nanowires and a proximal part having a longitudinal axis parallel to the cathode face and in which the proximal part is fixedly mounted with the proton exchange membrane.

[0021] In a preferred design, the nanotubes and / or nanowires are curved, defining a proximal portion with a longitudinal axis perpendicular to a face of the cathode current collector that holds the nanotubes and / or nanowires, and a proximal portion with a longitudinal axis parallel to the cathode face. The proximal portion slides along the proton exchange membrane.

[0022] In an advantageous embodiment, the high-temperature fuel cell comprises a first reservoir containing an oxygen precursor connected to a first feed channel, the first reservoir delivering a first flow of oxygen precursor into the first feed channel, the first feed channel being partially delimited by the cathode current collector; - a second reservoir containing a hydrogen precursor connected to a second feed channel, the second reservoir delivering a second flow of hydrogen precursor into the second feed channel.

[0023] Preferably, the cathode current collector introduces a pressure drop representative of a decrease in oxygen flow, with a flow ratio between the first feed channel and the cathode electrode greater than 2.

[0024] In an advantageous development, the cathode current collector introduces at least a pressure drop corresponding to a flow ratio between the first feed channel and the cathode electrode greater than 5.

[0025] In one particular embodiment, the fuel cell includes second nanotubes and / or nanowires in thermal connection with the cathode current collector and arranged in the first feed channel.

[0026] The invention also relates to an energy generator that is more efficient than prior art configurations.

[0027] This result is tended to be achieved by means of a power generator comprising at least two fuel cells according to any of the preceding configurations in which the at least two fuel cells are stacked in a stacking direction and two fuel cells of the at least two fuel cells have two anode current connectors or two cathode current connectors as nearest neighbor current collectors in the stacking direction, said two nearest neighbor current collectors being supplied by the same supply channel.

[0028] In a particular embodiment, said two nearest neighbor current collectors are separated by an electrically insulating separator elastically deformed by said two nearest neighbor current collectors along the stacking direction.

[0029] The invention also relates to a manufacturing process that is more efficient than the embodiments of the prior art.

[0030] This embodiment is to be achieved by means of a manufacturing process which includes the following steps: - providing a proton exchange membrane and a cathode current collector formed by a metallic foam; - growing nanowires and / or nanotubes from one face of the metallic foam; - depositing the nanowires and / or nanotubes against one face of the proton exchange membrane. Brief description of the drawings

[0031] Other advantages and features will become clearer from the following description of particular embodiments and implementations of the invention, given by way of non-limiting examples and shown in the accompanying drawings, in which:

[0032] : schematically illustrates an energy generator equipped with a fuel cell according to the invention;

[0033] : schematically illustrates an energy generator equipped with several fuel cells according to the invention;

[0034] : schematically illustrates an energy generator equipped with a fuel cell mounted on a frame according to the invention.

[0035] : schematically illustrates an energy generator equipped with several fuel cells mounted on several frames according to the invention.

[0036] Figures 1 to 4 illustrate a fuel cell and a generator equipped with fuel cells. The fuel cell comprises a membrane-electrode assembly which includes a proton exchange membrane 1, an anodic electrode 2, a cathodic electrode 3, an anodic current collector 4 and a cathodic current collector 5.

[0037] The fuel cell is preferably a high-temperature fuel cell, i.e., with an operating temperature above 80°C, preferably above 100°C, and even more preferably above 120°C. The proton exchange membrane 1 can be made of polybenzimidazole (PBI) or any other material suitable for high-temperature operation. Preferably, the operating temperature is above 100°C to ensure that water is in gaseous form within the pressure range used on the cathode side. Preferably, the degradation temperature of membrane 1 is above 100°C, or even above 150°C, and more preferably above 200°C. In a fuel cell operating at low temperature, the operating temperature is preferably below the evaporation temperature of water at the fuel cell's operating pressure, for example, below 100°C.

[0038] The proton exchange membrane 1 defines an anodic face and a cathodic face. The anodic face is covered by the anodic electrode 2, while the cathodic face is covered by the cathodic electrode 3. The anodic electrode 2 is located between the proton exchange membrane 1 and the anodic current collector 4. The cathodic electrode 3 is located between the proton exchange membrane 1 and the cathodic current collector 5.

[0039] At least one of the anodic electrode 2 and the cathodic electrode 3 is a nanostructured electrode, that is, a non-smooth electrode. The nanostructured electrode comprises filamentary nanoelements that extend primarily in the direction connecting the anodic current collector 4 and the cathodic current collector 5 and / or perpendicular to the cathodic or anodic face. The filamentary nanoelements consist of nanotubes and / or nanowires. Nanotubes are hollow filamentary elements, while nanowires are solid filamentary elements.

[0040] The wire nanoelements include a catalyst material which can be a cathodic catalyst material or an anodic catalyst material depending on whether the wire nanoelements belong to the cathodic electrode 3 or the anodic electrode 2. The wire nanoelements can be coated by particles of catalyst material or by a continuous layer of catalyst material.

[0041] Wired nanoelements are electrically conductive and are electrically connected to current collectors to enable electron transfer between the current collector and the catalyst material, thus carrying out electrochemical reactions. Wired nanoelements can be carbon nanotubes or nanowires made of a metallic or other material.

[0042] The use of a nanostructured cathode electrode 3 increases the exchange surface area between the gas and the catalytic material, the site of the electrochemical reaction. The same applies to the use of a nanostructured anodic electrode 2.

[0043] Preferably, the filamentary nanoelements extend primarily in a direction perpendicular to the cathodic face or perpendicular to the anodic face. The extension direction of the filamentary nanoelements is parallel to the thickness direction of the proton exchange membrane. The thickness direction corresponds to the stacking direction of the membrane-electrode assembly.

[0044] The catalyst material can be chosen from chromium, molybdenum, tungsten, manganese, rhenium, iron, copper, silver, zinc, tin, gold, aluminum, osmium, palladium, platinum, iridium, nickel, cobalt, rhodium, and osmium. It is also possible to use several of these elements and / or a mixture thereof.

[0045] Carbon nanotubes preferably have a diameter between a few nanometers and a few tens of nanometers. Preferably, the nanotubes have, on average, a diameter greater than 2 nm, or even greater than 5 nm, or greater than 10 nm, or even greater than 15 nm. It is advantageous for the nanotubes to have a diameter less than 200 nm, or even less than 150 nm, or even less than 100 nm, or even less than 80 nm, and more preferably less than 50 nm. In a preferred embodiment, the nanotube density is between 10 9 and 12 12 nanotubes / cm 2 , for a minimum surface area which is preferably greater than or equal to 0.5mm 2 .

[0046] When the nanowires are carbon nanotubes, the carbon nanotubes contain inclusions of a catalyst material, or particles of the catalyst material are attached to the carbon nanotubes. Alternatively, the nanostructured surface is formed by a mat of carbon nanotubes coated with a catalyst layer, preferably platinum. Preferably, the catalyst is deposited by atomic layer deposition (ALD). Advantageously, the catalyst layer thickness is less than 15 atomic layers, preferably less than 10 atomic layers. The same can be true for the nanowires.

[0047] The presence of a layer of filamentary nanoelements between the proton exchange membrane 1 and the current collector provides significant roughness, thus increasing the usable exchange surface area for a given volume. These filamentary nanoelements exhibit good electrical and thermal conductivity, enabling the layer to ensure efficient charge carrier flow during the redox phase and to ensure good temperature homogenization along directions parallel to the cathodic or anodic surface.

[0048] The use of wire-like nanoelements allows for good electrical and thermal conduction with the proton exchange membrane. The use of wire-like nanoelements also allows for good heat conduction in a direction perpendicular to the interface between the cathode electrode and the proton exchange membrane.

[0049] Preferably, the thickness of the anodic electrode 2 and / or the cathodic electrode 3 is between 5 microns and 200 microns, preferably between 5 microns and 100 microns, preferably between 5 microns and 50 microns.

[0050] To increase the efficiency of the catalyst material on the wire nanoelements, it is particularly advantageous to use an ionically conductive layer or an ionic conductor that partially covers the wire nanoelements, preferably a layer of a proton conductor. The ionically conductive layer connects the catalyst material and the proton exchange membrane to transfer the protons involved in the electrochemical reactions.

[0051] To avoid hindering the reaction between the catalyst material and the gas, it is advantageous for the ionically conductive layer to be in liquid form. The liquid attaches to the filament nanoelements by capillary action, allowing the use of a small amount of ionically conductive material and the easy formation of a thin layer over a large portion, or even the entire height, of the filament nanoelements to connect the largest possible surface area of ​​catalyst material.

[0052] The use of an ionically conductive layer in liquid form allows for better management of deformations related to differential expansions between the proton exchange membrane 1, the current collector (preferably the cathode current collector), and the wire nanoelements. Depending on temperature changes, the proton exchange membrane 1, the cathode current collector 5, and the wire nanoelements expand or contract. Since the proton exchange membrane 1, the cathode current collector 5, and the wire nanoelements have different coefficients of thermal expansion, the cathode electrode 3 is subjected to different sets of stresses. To maintain good performance throughout the fuel cell's lifetime, it is advantageous to have an ionically conductive layer in liquid form that can accommodate the relative deformations between the different layers of the fuel cell.

[0053] Because the fuel cell operates at high temperatures, much of the water produced by hydrogen reduction is present in its gaseous form, which tends to limit the dilution of the proton conductor. The proton conductor is preferentially an acid, more preferably a strong acid diluted with water, and even more preferably a solution of H3PO4.

[0054] The ionically conductive layer is formed by a first compound in liquid form. The first compound is preferably a copolymer fluoropolymer based on sulfonate tetrafluoroethylene, for example a compound known as Nafion®.

[0055] Preferably, the first compound has an evaporation temperature that is higher than the evaporation temperature of water by at least 20°C, preferably by at least 50°C and more preferably by at least 100°C at the operating pressure of the fuel cell.

[0056] Preferably, the first compound has an evaporation temperature that is higher than the fuel cell operating temperature by at least 10°C and more preferably higher than the fuel cell operating pressure by at least 50°C.

[0057] It is advantageous to choose the quantity of the first compound so that the thickness of the ionically conductive layer is less than the thickness of the catalyst material particles, thus avoiding complete coverage of the catalyst material. Preferably, the filamentous nanoelements have a coating that exhibits a first surface tension value with the first compound that is greater than a second surface tension value with the catalyst material. This facilitates the release of the catalyst material surface for the electrochemical reaction.

[0058] It is advantageous for the maximum thickness of the ionic conductor to be less than 20 microns to form the ionically conducting channels.

[0059] The cathode electrode 3 is a layer that receives oxygen. This cathode electrode 3 is a porous or perforated layer with perforations in one or more directions parallel to the surface of the anodic or cathodic face, allowing for good fluid circulation. This facilitates efficient use of the entire available surface area of ​​the catalyst material.

[0060] The presence of the catalyst material on the surface of the wire nanoelements allows for good heat conduction towards the current collector, particularly the cathode current collector 5. The ionically conductive layer does not form an obstacle to heat dissipation.

[0061] Preferably, the catalyst material can be in the form of particles or a thin porous layer.

[0062] When the filament nanoelement is a carbon nanotube, the catalyst material can be in the form of particles or a thin porous layer. Using particles prevents excessively reducing the gas's ability to pass through the carbon nanotube. The same is essentially true when the catalyst material is a porous layer. This configuration allows for a greater number of triple points—that is, interfaces between the catalyst, the carbon nanotube, and the ionically conductive layer—which are the most efficient points for electrochemical reactions.

[0063] To obtain a thin porous layer, an ALD type deposit is recommended.

[0064] In an advantageous embodiment, filamentary nanoelements are present on both sides of the cathode current collector 5. First filamentary nanoelements are arranged between the cathode current layer 5 and the proton exchange membrane 1 to form the cathode electrode 3. Second filamentary nanoelements are arranged on the opposite side of the cathode current layer 5 to be located in the oxygen precursor gas supply channel. These second filamentary nanoelements are thermally connected to the cathode current collector 5. The second filamentary nanoelements are swept by the oxygen precursor gas, which increases the heat exchange surface area between the oxygen precursor gas and the cathode current collector 5.If a portion of the oxygen precursor gas is not used in the electrochemical reaction and delivers heat to the second wire nanoelement or absorbs heat, this electrochemically inactive portion of gas can be used to regulate the temperature of the assembly formed by the proton exchange membrane 1, the cathode electrode 3 and the cathode current collector 5. It is advantageous for the second wire nanoelements to be nanotubes and preferably carbon nanotubes in order to have good heat exchange with the gas circulating in the feed channel without introducing too great a pressure drop.

[0065] The fuel cell may be equipped with a temperature sensor configured to measure the temperature of the fuel cell, the proton exchange membrane, or the assembly formed by the proton exchange membrane 1, the cathode electrode 3, and the cathode current collector 5. When the temperature exceeds a threshold value, a fuel cell control circuit can inject excess oxygen precursor gas, which is cooler. Conversely, when the temperature falls below a second threshold, which is lower than the first threshold, the control circuit can inject warmer oxygen precursor gas.

[0066] For example, if the oxygen precursor gas comes from a pressurized gas, the expansion of the gas out of the reservoir towards the feed channel 6 can be used to supply a gas whose temperature is below the threshold temperature, which allows the cathode current collector 5 to be cooled. Sending a larger quantity of gas allows the current collector 5 to be cooled.

[0067] Sending a larger quantity of gas generates greater electrochemical activity, it is advantageous for the cathode current collector 5 to introduce a pressure drop which allows only a small part of the gas to be sent to the cathode electrode, for example less than 70% of the gas beyond its nominal operating point, preferably less than 50%, more preferably less than 20%.

[0068] The same may apply to the anodic current collector 4.

[0069] In a preferred embodiment, the cathode current collector 5 is a metallic foam. The metallic foam has open pores such as to define channels connecting the two opposite walls along the thickness direction.

[0070] The use of metallic foam makes it possible to form a current collector which has good thermal conductivity along the thickness and good electrical conductivity.

[0071] It is advantageous for the cathode current collector 5 to define a wall of the feed channel 6 in oxygen precursor. The oxygen precursor gas flowing in the feed channel 6 passes through the cathode current collector and flows inside the cathode electrode 3 until it comes into contact with the catalyst material.

[0072] Metallic foam advantageously presents a porosity rate between X and Y% by volume.

[0073] Metallic foam has pores on its surface with an average diameter between X and Y microns.

[0074] The use of metallic foam is particularly advantageous because it has better compressive strength compared to the carbon felts commonly used in the prior art. Metallic foam compresses less than the carbon felt layer when a given force is applied, thus allowing less force to be applied to ensure good contact between the cathode electrode 3 and the cathode current collector 5, or between the cathode electrode 3 and the proton exchange membrane 1.

[0075] With fewer constraints applied, it is easier to manage differential expansion between the cathode current collector and the proton exchange membrane. It is also easier to form an electrical generator.

[0076] When the fuel cell has an ionically conductive layer in liquid form, it is advantageous to have a metallic foam with surface pores smaller than 10 microns in diameter, as this makes it difficult or even impossible for the liquid to pass through the metallic foam. This passage is further hampered when the fuel cell is operating and releasing an oxygen precursor gas that tends to push the liquid towards the proton exchange membrane.

[0077] When the ionically conductive layer is formed by a strong acid, the metal foam material is preferably inert to the strong acid and / or the external surface of the metal foam is covered with a protective coating, for example a carbon-based coating deposited by PVD (Physical Vapor Deposition). The coating is electrically conductive.

[0078] The metallic foam can be titanium foam, nickel foam, or preferably Monel nickel and copper foam. Aluminum foam, possibly with a protective coating, can also be used. Inconel (nickel-chromium alloy) or Hastelloy (nickel-molybdenum alloy) foam are also options.

[0079] It is still possible to use a stainless steel foam which is preferably coated with a protective coating, for example a layer of amorphous carbon.

[0080] The metallic foam is preferably free of catalyst material, and any inclusions of catalyst material are devoid of ionically conductive connections with the proton exchange membrane. The metallic foam is used solely as a current collector capable of efficiently conducting electrical current and extracting heat, taking advantage of its superior compressive strength compared to carbon felts.

[0081] Alternatively, the metallic foam has a surface containing or coated with catalyst material to increase the electrochemically active surface area. The ionic conductor forms ionically conductive channels to connect the proton exchange membrane and the active part of the cathode current collector 5. The ionically conductive channels are formed by capillary action. The channels can be formed by a suitable coating or texturization of the cathode current collector 5.

[0082] In a particularly advantageous embodiment, the metallic foam is used as a starting substrate for the growth of the wire nanoelements. The wire nanoelements of the cathode electrode 3 are attached to the metallic foam, and the installation of the cathode current collector facing the cathode wall of the proton exchange membrane 1 allows the cathode electrode 3 to be connected to the proton exchange membrane 1.

[0083] In another embodiment, the wire nanoelements are made from the cathode wall of the proton exchange membrane 1. The metallic foam is pressed against the wire nanoelements to make the electrical connection between the wire nanoelements and the cathode current collector 5.

[0084] In the cathode zone, the electrochemical reaction produces water, which, depending on temperature and pressure conditions, can be in liquid or gaseous form. When the ionically conductive layer is liquid and contains water, it is advantageous that the fuel cell's operating conditions do not significantly alter the composition of the ionically conductive layer. Such alterations would result in changes to the capillary characteristics between the ionically conductive layer and the filament nanoelements. The metallic foam can be coated with a hydrophobic coating, such as fluoropolymers or hydrophobic epoxy resins. The surface of the metallic foam can also contain titanium dioxide inclusions to further enhance its hydrophobicity. It is also possible to manipulate the surface texture, particularly the pore diameter, to either facilitate or hinder water evacuation.

[0085] Foam can be used as a starting substrate for the growth of filamentous nanoelements, preferably carbon nanotubes. The use of a metallic foam allows for the definition of one or more characteristics of the carbon nanotubes. The dimensions of the pores and / or the spacing between them define the diameters of the filamentous elements and their arrangement relative to one another. In one embodiment, the filamentous nanoelements are formed from the pores, and their diameter is substantially equal to the diameter of the pores from which they are formed. In another embodiment, the filamentous nanoelements are formed from the surface adjacent to the pores, and their diameter is substantially equal to the diameter of the surface adjacent to the pores from which they are formed.The growth of carbon nanotubes is disclosed in the documents “Direct Growth of Binder-Free CNTs on a Nickel Foam Substrate for Highly Efficient Symmetric Supercapacitors” by Isacfranklin et al. ACS Omega 2023, 8, 11700-11708 and “Direct synthesis of carbon nanotubes on metallic foams as a cathode material with high mass load for lithium–air batteries” by Ionescu RSC adv., 2017, 7, 30365-30369.

[0086] It is also known to grow nanotubes made of gallium nitride, boron nitride, WS2, MoS2, and Vo-type oxides X , MnO X. NiCo2S4 / NiMoO4.La croissance de tels nanotubes est connue des documents NiCo2S4@NiMoO4 Core-Shell Heterostructure Nanotube Arrays Grown on Ni Foam as a Binder-Free Electrode Displayed High Electrochemical Performance with High Capacity, Zhang et al., Nanoscale Research Letters (2017) 12:412. ; « Preparation of Co3O4 nanowires grown on nickel foam with superior electrochemical capacitance » Huang et al. Electrochimica Acta, Volume 75, 30 July 2012, Pages 273-278

[0087] The surface texture can differ between the anodic current collector 4 and the cathodic current collector 5 to achieve different behaviors with respect to water. The cathodic current collector 5 can have areas with different textures to form hydrophobic zones and less hydrophobic or even hydrophilic zones. The hydrophobic and hydrophilic zones are distinguished by different surface tension values. The hydrophobic zone has a lower capacity to retain water than the hydrophilic zone. The water formed by the fuel cell moves from the hydrophobic zone to the hydrophilic zone. The use of hydrophobic and hydrophilic zones on filamentary nanoelements can be advantageous in both low-temperature and high-temperature fuel cells.

[0088] In an even more advantageous embodiment, first filamentary nanoelements are formed on one side of the cathode current collector 5 and have inclusions of catalyst material and / or are coated with catalyst material. On the other side of the cathode current collector 5, second filamentary nanoelements are formed and are located in the oxygen precursor supply channel 6. These second filamentary nanoelements increase the exchange surface area between the oxygen precursor gas and the cathode current collector 5, which allows for better temperature regulation of the cathode current collector 5 and therefore better temperature regulation of the cathode electrode 3 and the proton exchange membrane 1.

[0089] The first and second filament nanoelements can be formed simultaneously from the two opposite faces of the cathode current collector. It is also possible to form them one after the other.

[0090] The second wire nanoelements are devoid of catalyst material and / or are devoid of ionically conductive connection with the proton exchange membrane 1.

[0091] In a particular embodiment, to facilitate the dissipation of heat produced by the cathode electrode 3, it is advantageous to enhance heat dissipation through the cathode current collector 5, and more preferably, through the oxygen precursor gas. The cathode current collector 5 exhibits good thermal conductivity along its thickness direction. Preferably, the cathode current collector 5 is made of a metallic material. The cathode current collector 5 has a good thermal connection with the cathode electrode 3; preferably, the cathode electrode 3 is fixed to the cathode current collector 5 or has a large contact surface with the cathode current collector 5.

[0092] As mentioned previously, the fuel cell can be equipped with a temperature sensor configured to measure the temperature of one or more of its components. Alternatively, the fuel cell may not have such a sensor, and the operating conditions may have been previously studied to define operating conditions that ensure good temperature control.

[0093] The cathode current collector 5 has an inner face that is in contact with the cathode electrode 3 and an outer face that is opposite it. The gas enters through the outer face and passes through the cathode current collector 5 to reach the cathode electrode 3. The outer face delimits at least part of a first oxygen precursor supply channel 6.

[0094] The anodic current collector 4 has an inner face in contact with the anodic electrode 2 and an outer face opposite it. The gas enters through the outer face and passes through the anodic current collector 4 to reach the anodic electrode 2. The outer face defines at least part of a second hydrogen precursor supply channel 7. It is advantageous for the supply channel to also serve as an exhaust channel.

[0095] In an advantageous embodiment, the cathode electrode 3 is integral with the proton exchange membrane 1. The deformations of the cathode catalytic layer 3 and the proton exchange membrane 1 are identical or substantially identical in directions perpendicular to the thickness direction. In another advantageous embodiment, the anodic electrode 2 is integral with the proton exchange membrane. The deformations of the anodic catalytic layer 2 and the proton exchange membrane 1 are identical or substantially identical in directions perpendicular to the thickness direction.

[0096] In an even more advantageous embodiment, the cathode electrode 3 is integral with the cathode current collector 5. The deformations of the cathode catalytic layer 3 and the cathode current collector 5 are identical or substantially identical in directions perpendicular to the thickness direction. Using a cathode electrode 3 that is integral with the cathode current collector 5 allows for efficient heat and current transfer from the catalytic layer to the current collector, even without applying a bearing force between the multiple layers of the stack. This improves the fuel cell's lifespan by minimizing the forces along the thickness direction required for close contact between the different layers. The same advantageous principle applies to the anodic electrode 2 with the anodic current collector 4.

[0097] A first feed channel 6 connects a first reservoir containing an oxygen precursor and the cathode electrode 3. A second feed channel 7 connects a reservoir containing a hydrogen precursor and the anodic electrode 2.

[0098] The first power supply channel 6 is partially delimited by the cathode current collector 5. The second power supply channel 7 is partially delimited by the anode current collector 4.

[0099] The reaction of the oxygen precursor with the cathode electrode 3 and the hydrogen precursor with the anodic electrode 2 is stoichiometric. At least one gas flow rate is predetermined and delivered to provide a predetermined current value by the fuel cell. It is advantageous for one gas to be delivered under superstoichiometric conditions so that the other gas limits the reaction and defines the amount of current to be delivered. To facilitate the removal of water produced in the cathode zone, it is advantageous for the oxygen precursor to be delivered under superstoichiometric conditions compared to the hydrogen precursor.

[0100] To facilitate the removal of water produced in the cathodic zone, a high gas flow rate on the cathodic side is advantageous. It is also advantageous to have an oxygen precursor flow rate that exceeds the stoichiometric flow rate. This excess oxygen provides a gas flow that ensures both the supply of oxygen precursor and the removal of water. Advantageously, the oxygen flow rate in cathodic electrode 3 is more than twice the stoichiometric flow rate.

[0101] The cathode current collector 5 and the anodic current collector 4 are openwork layers and they define a pressure drop between the flow which circulates between the feed channel and the associated electrode, i.e. in the direction of the anodic or cathodic electrode.

[0102] The flow rate of the gas emitted from the oxygen precursor reservoir is adjusted so that the pressure drop induced by the cathode current collector 5 does not prevent the oxygen precursor flow rate from exceeding the stoichiometric flow rate. Advantageously, the cathode current collector 5 defines a pressure drop that corresponds to a halving of the flow rate between the first feed channel 6 and the cathode electrode 5 within the nominal operating range of the fuel cell. The stoichiometric flow rate corresponds to the flow rate that ensures the reaction between the gas introduced on the anodic side and the gas introduced on the cationic side under stoichiometric conditions. Preferably, an oxygen precursor, such as dioxygen or air, can be introduced. Hydrogen or another precursor can also be introduced.

[0103] Advantageously, the pressure in the first supply channel 6 is greater than 1013 hPa, preferably greater than 2026 hPa. Preferably, the pressure in the first supply channel 6 is less than 10130 hPa. Advantageously, the pressure in the second supply channel 7 is greater than 1013 hPa, preferably greater than 2026 hPa. Preferably, the pressure in the second supply channel 7 is less than 10130 hPa. More preferably, the pressure in the second supply channel 7 is less than 2026 hPa, even more preferably less than 1520 hPa, even more preferably less than 1317 hPa, and even more preferably less than 1216 hPa.

[0104] Preferably, the gas flow rate from the oxygen precursor reservoir is also adapted to remove a significant amount of heat. The higher the gas flow rate, the greater the amount of heat removed. However, applying too high a flow rate results in the drying out of the proton exchange membrane 1. It is therefore advantageous to transform a very high flow rate in the feed channel 6 into a lower flow rate capable of supplying the amount of gas necessary for the electrochemical reaction and removing the water without drying out the proton exchange membrane 1. Advantageously, the cathode current collector 5 defines a pressure drop that corresponds to a fivefold reduction in the flow rate between the first feed channel 6 and the cathode electrode 5.More advantageously, the cathode current collector 5 defines a pressure loss which corresponds to a division by ten of the flow rate between the first feed channel 6 and the cathode electrode 5.

[0105] It is advantageous for the cathode current collector 5 to define a pressure drop which corresponds to a division of the flow rate equal to 2 between the flow rate of the first feed channel and the flow rate in the cathode electrode 3, but no more than a division by 20 of the flow rate in the nominal operating range of the fuel cell.

[0106] Pressure drop is introduced by means of a plurality of holes that pass through the cathode current collector. To obtain the desired pressure drop, it is possible to form a foam with a large number of small holes or a foam with a smaller number of larger holes. An increase in the porosity of the foam leads to a decrease in pressure drop. The smaller the pore size, the greater the pressure drop. The larger the specific surface area, the greater the viscous friction within the foam. The greater the tortuosity in the foam—that is, the more convoluted the channels—the greater the pressure drop. The greater the thickness of the foam, the greater the pressure drop.

[0107] Pressure loss can be defined as the maximum flow rate that can pass through the metallic foam for a given pressure difference between the two faces of the foam. Pressure loss also depends on the dynamic viscosity of the fluid passing through the foam. The higher the dynamic viscosity, the greater the pressure loss. Similarly, the higher the fluid density, the greater the pressure loss.

[0108] The pressure drop also depends on the flow conditions, i.e., the fluid's surface velocity. Depending on whether the fluid flows viscously or inertially, the pressure drop will be defined by Darcy's law or Forchheimer's law. Applying a high flow rate in the first supply channel 6 facilitates heat dissipation by means of the gas circulating against the outer face of the cathode current collector 5, which is a good thermal conductor in direct contact with the cathode electrode 3.

[0109] In one particular embodiment, the aim is to increase the contact area between the filament nanoelements and the proton exchange membrane 1 so as to enhance heat transfer between the proton exchange membrane 1 and the cathode electrode 3. Alternatively, the aim is to increase the contact area between the filament nanoelements and the cathode current collector 5 so as to enhance heat transfer and electrical conduction between the cathode current collector 5 and the cathode electrode 3.

[0110] Preferably, curved wire nanoelements are used. The wire nanoelements have a distal part attached to the cathode current collector 5 or to the proton exchange membrane 1 and the proximal part of the wire nanoelements is in contact respectively with the proton exchange membrane 1 or the cathode current collector 5. The wire nanoelements are curved between the proximal and distal parts.

[0111] Il est connu de réaliser des nanoélément filaires incurvés dans les documents suivants : « Electric field-oriented growth of carbon nanotubes and Y-branches in a needle-pulsed arc discharge unit: mechanism of the productionKia et al., Journal of Experimental Nanoscience, 2014 ; « Effects of magnetic and electric fields on the growth of carbon nanotubes using plasma enhanced chemical vapor deposition technique », Baghgar et al., Eur. Phys. J. Appl. Phys. 48, 20603 (2009) ; « Electric-field-directed growth of aligned single-walled carbon nanotubes », Zhang et al., Appl. Phys. Lett. 79, 3155 (2001) ; « Controlling nanowire growth through electric field-induced deformation of the catalyst droplet », Panciera et al., NATURE COMMUNICATIONS | 7:12271.

[0112] The proximal portion extends substantially perpendicularly to the face of the cathode current collector 5 or the face of the proton exchange membrane 1 to which the filament nanoelements are attached. More preferably, the growth of the filament nanoelements has occurred from this face. The proximal portion extends in a direction that is substantially parallel to the face receiving the distal portion.

[0113] Preferably, the distal part is arranged to slide relative to the proton exchange membrane 4 or the cathode current collector 5. During differential deformations between the proton exchange membrane 1 and the cathode current collector 5, the wire nanoelements are able to move and possibly deform to limit the stresses applied within the fuel cell.

[0114] In an alternative embodiment, a portion of the distal part is fixedly mounted to the proton exchange membrane 1 or to the cathode current collector 5. During differential deformations between the proton exchange membrane 1 and the cathode current collector 5, the wire nanoelements are able to deform to limit the stresses applied within the fuel cell.

[0115] At the end of their growth phase, the filamentous nanoelements do not all have the same length. The greater the desired length, the greater the length variations. The shortest filamentous nanoelements may not be active if the gap between the filamentous nanoelement and the proton exchange membrane 1 prevents the formation of an ionically conductive connection. If the filamentous nanoelement is not in contact with the cathode current collector 5, the catalyst present on the filamentous nanoelement will not interact electrochemically.

[0116] If the filament nanoelements are straight, a cutting step can be performed to reduce the gap between the longest and shortest filament nanoelements, thereby increasing the proportion of electrochemically active filament nanoelements. Alternatively, during growth, the filament nanoelements are curved, which increases the contact area of ​​the distal portion with the proton exchange membrane 1 or the cathode current collector 5. The length differences are partially eliminated.

[0117] If the distal portion is in contact with the proton exchange membrane 1 and a liquid ionic conductor is used, all or part of the distal portion may be covered by the liquid ionic conductor. The distal portion allows for significant contact with both the proton exchange membrane 1 and the liquid ionic conductor, resulting in efficient heat transfer. If the distal portion is in contact with the cathode current collector 5, the significant contact length enables efficient heat exchange and electron transfer.

[0118] Curved wire nanoelements can be nanotubes, for example carbon nanotubes, or nanowires, for example silicon nanowires, germanium nanowires, or cadmium sulfide nanowires.

[0119] It is particularly advantageous to use curved filament nanoelements when the length of the filament nanoelement is greater than 50 microns, more preferably greater than 100 microns or 200 microns.

[0120] The anodic current collector 4 and the cathodic current collector 5 each define at least one output terminal of electric current out of the fuel cell.

[0121] Preferably, the porous network is also through-through in at least one direction parallel to the interface between the cathode electrode 3 and the cathode current collector 5.

[0122] It is particularly advantageous that the anodic electrode 2 and the cathodic electrode 3 be fixedly mounted to the proton exchange membrane 1. It is even more advantageous that the anodic current collector 4 and the cathodic current collector 5 be fixedly mounted respectively to the anodic electrode 2 and the cathodic electrode 3.

[0123] The formation of a single-piece assembly extending from the anode current collector 4 to the cathode current collector 5 simplifies the fuel cell configuration by eliminating the means of compressing the stack.

[0124] The cathode current collector 5 can be a metallic layer perforated by holes along its thickness. The size, orientation, and distribution of the holes are chosen to achieve the expected pressure drop between the first feed channel 6 and the cathode electrode 5. The pressure drop value depends on the circulation conditions of the oxygen precursor in the feed channel (temperature, pressure, gas composition).

[0125] In a particular embodiment, the oxygen precursor supply channel 6 also forms the outlet channel for excess oxygen precursor and water. Preferably, at least one of the characteristic parameters of the holes is variable depending on the direction of oxygen precursor flow along the first supply channel 6 in order to have a decreasing pressure drop with respect to the direction of oxygen precursor flow and / or to account for the increase in water content in the gas mixture.

[0126] As an alternative or in addition, the porosity rate along the thickness direction is variable according to the direction of circulation of the oxygen precursor in order to have a decreasing pressure loss along the direction of circulation of the oxygen precursor.

[0127] The cathode current collector 5 can be a metallic foil defining a plurality of through holes. The cathode current collector 5 can be a metallic foam with through pores.

[0128] Since the fuel cell is designed to operate at a temperature above 80°C and more preferably above 100°C or even 120°C, the water can be in a gaseous or liquid form.

[0129] In a particular embodiment, the cathode current collector 5 is formed by a first porous layer and a second porous layer. The first porous layer is located between the cathode electrode 3 and the second porous layer. The first porous layer has an average pore size that is smaller than the average pore size of the second porous layer. For example, the first porous layer is a microporous layer and the second porous layer is a macroporous layer. The first porous layer has an average pore size that is less than 5 nanometers and the second porous layer has an average pore size that is greater than 25 nanometers, preferably greater than 50 nanometers. Both the first and second porous layers are good conductors of current and heat.The pore size refers to the pores extending in one or more directions parallel to the interface between the cathode electrode 3 and the cathode current collector 5. Preferably, the first and second porous layers are made of metal, for example, perforated metal or metallic foam. It is also possible to use carbon graphene or a felt formed by nanotubes extending parallel to the surface of the support substrate. The use of a carbon nanotube felt is particularly advantageous when the nanotubes contain catalyst inclusions, for example, platinum, and are impregnated with an acid, for example, phosphoric acid.

[0130] The use of large pores in the second layer allows for significant circulation of an oxygen precursor gas, such as air. This high gas circulation facilitates heat dissipation by utilizing a large exchange surface area between the gas and the second layer. Reducing porosity, and preferably pore size, limits the flow of oxygen precursor gas in the immediate vicinity of the catalyst. This reduction in airflow prevents the membrane surface from drying out during operation.

[0131] Depending on the desired operating conditions, namely the membrane temperature and the partial pressures of oxygen and hydrogen, it is possible to choose a second layer and a larger or smaller pore diameter.

[0132] The higher the operating temperature, the more the water will tend to be in a gaseous state, which encourages the use of small-diameter pores. The higher the oxygen flow rate, the greater the risk of drying out the proton exchange membrane, which also encourages the use of small-diameter pores. The higher the pressure or flow rate ratio between the oxygen precursor and the hydrogen precursor, the more advantageous it becomes to use small-diameter pores. A decrease in pore diameter can be offset, or combined with, an increase in the surface area of ​​hydrophobic material.

[0133] In a preferred embodiment, the average porosity in the cathode current collector 5 is less than 50%, more preferably less than 30%.

[0134] The cathode current collector 5 is preferably attached to the cathode electrode 3, for example by welding, brazing, or bonding. The cathode current collector 5 is attached by any suitable means that ensures electrical and thermal continuity between the cathode current collector 5 and the cathode electrode 3, regardless of deformations of the membrane-electrode assembly due to temperature and / or pressure changes.

[0135] What has been explained for the cathode current collector 5 can be applied to the anodic current collector 4. Preferably, the anodic current collector 4 is identical to the cathode current collector 5.

[0136] In a power generator, the fuel cell is arranged in an enclosure which partially defines the first feed channel 6 and the second feed channel 7. The enclosure has a first hood and a second hood which are separated by the membrane-electrode assembly.

[0137] The cathode current collector 5 is surmounted by a first cover 8, and the first cover 8 is advantageously separated from the cathode current collector 5 by a first separator 9. Preferably, the first separator 9 deforms elastically between the first cover 8 and the cathode current collector 5. The elastic deformation of the first separator 9 allows a predetermined force to be applied to one end of the membrane-electrode assembly. The first separator 9 may be in the form of a corrugated plate.

[0138] Advantageously, the anodic current collector 4 is surmounted by a second cover 10, and the second cover 10 is separated from the anodic current collector 4 by a second separator 11. Preferably, the second separator 11 deforms elastically between the second cover 10 and the anodic current collector 4. The elastic deformation of the second separator 11 allows a predetermined force to be applied to the other end of the membrane-electrode assembly. The second separator 11 may be in the form of a corrugated plate.

[0139] In another alternative, the membrane-electrode assembly is fixed to the enclosure by other means. In an embodiment illustrated in Figures 3 and 4, the enclosure has a frame 12 that defines a through hole. The peripheral portion of one face of the membrane-electrode assembly rests on the frame 10, which allows a gas to be applied to one face of the assembly through the frame. The seal between the anodic and cathodic faces is ensured by the peripheral portion of the membrane-electrode assembly that rests on the frame 12.

[0140] It is particularly advantageous for the enclosure to be made of electrically insulating material with a few electrical traces, resulting in a cost-effective and lightweight design. One end of the electrical traces contacts either the anode or cathode current collector. The other end of the electrical traces is intended to be connected to an electrical load or other suitable device. The enclosure can be made of plastic.

[0141] In a particularly advantageous embodiment, an energy generator comprises several fuel cells in one of the preceding configurations or in another configuration. Depending on the requirements, the fuel cells are connected in parallel or in series or a mixture of these two arrangements.

[0142] Several fuel cells are mounted opposite each other in a stacking direction parallel to the thickness direction of the individual fuel cells. This stacking direction runs through the multiple fuel cells. More specifically, it runs through the multiple cathode current collectors 5, the multiple anodic current collectors 4, the multiple anodic catalytic layers 2, the multiple cathodic catalytic layers 3, and the multiple proton exchange membranes 1. Preferably, each membrane-electrode assembly is mounted on a frame 12, and the multiple frames 12 are stacked one on top of the other.

[0143] The fuel cells are mechanically linked together so that two adjacent fuel cells share the same feed channel. In other words, two adjacent fuel cells have two anode current collectors 4 or two cathode current collectors 5 facing each other, which are nearest neighbor collectors. This arrangement facilitates gas flow management. It is also advantageous to share a separator, which then becomes common to two adjacent fuel cells. The separator is preferably electrically insulating to allow for greater flexibility in the available electrical configurations.

[0144] When the electric generator has three or more of three fuel cells, there are at least two adjacent fuel cells that have two cathode current collectors 5 as nearest neighbors and two adjacent fuel cells that have two anodic current collectors 4 as nearest neighbors.

[0145] Preferably, the fuel cells are mounted on or in frames 12, and the frames 12 are stacked one on top of the other to assemble the fuel cells facing each other. The frames 12 define a window for receiving a fuel cell and a through hole inside the window. Once the frames are stacked, the through holes are aligned along the stacking direction.

[0146] The fuel cells are arranged between the frames in such a way as to form an alternation between a fuel cell and a through hole according to the stacking direction, i.e. a window delimiting the through hole.

[0147] Advantageously, the 12 frames are stacked one on top of the other to define oxygen precursor supply channels and hydrogen precursor supply channels, as well as oxygen precursor exhaust channels and hydrogen precursor exhaust channels. The different gases flow from frame to frame. Preferably, the oxygen precursor flows in a channel configured to supply multiple cathode current collectors 5 in parallel.

[0148] When groups of two immediately adjacent fuel cells share the same feed channel to supply two current collectors with the same gas, it is advantageous to form two types of frame 12. Laillustrates an embodiment in which the plurality of frames 12 includes first frames that deliver the oxygen precursor to the cathodic current collectors and second frames that deliver the hydrogen precursor to the anodic current collectors.

[0149] Preferably, the first and second frames 12 each have through them the supply and / or discharge channel(s) for the oxygen precursor and the hydrogen precursor. However, a first frame allows only the supply of hydrogen precursor to a second frame, and a second frame allows only the supply of oxygen precursor to a second frame. The same may apply to the discharge channels.

[0150] In one configuration, the first hood 8 and the second hood 10 define an enclosure which encompasses the frame(s) 12. In an alternative, the enclosure is formed by the frame(s) 12 and is terminated at each end by the first hood 8 or the second hood 10.

[0151] In one particular embodiment, each frame 12 of a stack is mechanically linked to the two adjacent frames 12 by a connection that defines a bend zone, with the exception of the end frames. During the manufacture of the power generator, a fuel cell is mounted on or within each frame 12. The frames are arranged one on top of the other by bending the bend zones. The bending of the bend zones defines the supply channels as well as the discharge channels and the sealed portions around the multiple fuel cells.

[0152] Preferably, the frames 12 are provided with electrical tracks 13 which are connected to the anodic current collector 4 or the cathodic current collector 5. The frames 12 are made of an electrically insulating material, for example an electrically insulating plastic material, and are traversed by the electrical tracks.

[0153] All or part of the electrical tracks can cross the link in order to electrically connect one fuel cell with an adjacent fuel cell in an adjacent frame.

[0154] In one embodiment, at least some of the electrical tracks 13 of a frame make electrical contact with at least some of the electrical tracks 13 of an adjacent frame when the two frames are stacked one on top of the other. When the frames are not stacked, the electrical tracks 13 are not in contact.

[0155] The electrical tracks 13 are arranged along the frames 12 to connect the multiple fuel cells in a specific configuration, for example, in series, parallel, or a more complex arrangement. The electrical configuration of the individual fuel cells is defined by the tracks running within the frames before the fuel cells are installed.

[0156] It is particularly advantageous to use frames made of plastic or composite materials because this allows for the creation of lightweight frames whose mechanical performance within the operating temperature range of fuel cells ensures good sealing. The power generator can be manufactured economically. Furthermore, the use of a polymer frame is advantageous when the fuel cell contains a strong acid.

[0157] During operation, the redox reaction of the oxygen precursor and the hydrogen precursor occurs at the surface of the anodic and cathodic electrodes. A flow of protons crosses the proton exchange membrane 1 from the anodic face to the cathodic face. Electrons flow along the anodic electrode 2 and through the filament nanoelements until they reach the anodic current collector 4. The electrons then leave the fuel cell to be used in an electrical charge. Conversely, a flow of electrons enters the fuel cell via the cathodic current collector 5 and then reaches the cathodic electrode 3, notably by flowing through the filament nanoelements.

Claims

Fuel cell comprising: - a proton exchange membrane (1) having an anodic face and an opposite cathodic face; - an electrically conductive anodic current collector (4) and a cathodic current collector (5); - an anodic electrode (2) electrically connected to the anodic current collector (4) and a cathodic electrode (3) electrically connected to the cathodic current collector (5); wherein at least one of the anodic electrode (2) and the cathodic electrode (3) comprises electrically conductive nanotubes and / or nanowires, the nanowires and / or nanotubes extending predominantly in a direction perpendicular to the anodic face and / or the cathodic face; wherein the nanowires and / or nanotubes are at least partially coated with a catalyst material; wherein an ionically conductive layer connects the proton exchange membrane (1) and the catalyst material;characterized in that the cathode current collector (5) is an open-pore metallic foam, the cathode current collector being in direct contact with the nanowires and / or nanotubes and having a compressive strength greater than the compressive strength of the cathode electrode (3) and greater than the compressive strength of the proton exchange membrane (1). Fuel cell according to claim 1 wherein the nanowires and / or nanotubes have an average diameter that is identical to the average diameter of the pores. Fuel cell according to any one of claims 1 and 2 wherein the cathode current collector (5) is at least partially covered by a layer of hydrophobic material. Fuel cell according to claim 3 wherein the average surface pore size is less than 10 microns Fuel cell according to any one of claims 1 to 4 wherein the cathode current collector (5) comprises catalyst material particles and / or a catalyst material coating ionically connected to the proton exchange membrane (1) by the conductive ion layer. Fuel cell according to any one of claims 1 to 5 wherein the cathode current collector (5) is fixedly mounted with the cathode electrode (3) to form a monolithic assembly deforming uniformly in one or more directions parallel to the interface between the cathode current collector (5) and the cathode electrode (3). Fuel cell according to claim 6 wherein the nanotubes and / or nanowires are curved and define a proximal part having a longitudinal axis perpendicular to a face of the cathode current collector fixing the nanotubes and / or nanowires and a proximal part having a longitudinal axis parallel to the cathode face and wherein the proximal part is fixedly mounted with the proton exchange membrane (1). Fuel cell according to any one of claims 1 to 5 wherein the nanotubes and / or nanowires are curved and define a proximal part having a longitudinal axis perpendicular to a face of the cathode current collector fixing the nanotubes and / or nanowires and a proximal part having a longitudinal axis parallel to the cathode face and wherein the proximal part is mounted sliding along the proton exchange membrane (1). Fuel cell according to any one of claims 1 to 8 comprising a first reservoir containing an oxygen precursor connected to a first feed channel (6), the first reservoir delivering a first flow of oxygen precursor into the first feed channel (6), the first feed channel being partially delimited by the cathode current collector; - a second reservoir containing a hydrogen precursor connected to a second feed channel (7), the second reservoir delivering a second flow of hydrogen precursor into the second feed channel (7). Fuel cell according to claim 9 wherein the cathode current collector introduces a pressure drop representative of a decrease in oxygen flow, a flow ratio between the first feed channel (6) and the cathode electrode being greater than 2. Fuel cell according to claim 10 wherein the cathode current collector (5) introduces at least one pressure drop corresponding to a flow ratio between the first feed channel (6) and the cathode electrode (3) greater than 5. Fuel cell according to any one of claims 9 to 11 comprising second nanotubes and / or nanowires in thermal connection with the cathode current collector (5) and disposed in the first feed channel. Power generator comprising at least two fuel cells according to any one of the preceding claims wherein the at least two fuel cells are stacked in a stacking direction and two fuel cells of the at least two fuel cells have two anode current connectors (4) or two cathode current connectors as nearest neighbor current collectors in the stacking direction said two nearest neighbor current collectors being supplied by the same supply channel. Power generator according to claim 13 in which said two nearest neighbor current collectors are separated by an electrically insulating separator elastically deformed by said two nearest neighbor current collectors along the stacking direction. Method of manufacturing a fuel cell according to any one of claims 1 to 12 comprising the following steps:- providing a proton exchange membrane (1) and a cathode current collector formed by a metallic foam;- growing nanowires and / or nanotubes from one face of the metallic foam;- depositing the nanowires and / or nanotubes against one face of the proton exchange membrane.

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