Method for manufacturing flow guides for electrochemical reactors

Abstract

This invention relates to a method for manufacturing a flow guide (1, 1') for an electrochemical reactor, comprising the steps of: providing a substrate (10); providing a first mesh screen (11) including openings (111) configured to form a first pattern (21) of ribs (211) of the first flow guide (1); and providing a second mesh screen (12) including openings (121) configured to form a second pattern (22) of ribs (221) of the first flow guide (1). The invention utilizes screen printing technology to produce fluid loops with large channel depths and aspect ratios equal to or greater than 1.

Description

Technical Field

[0001] This invention relates to the optimization of the manufacture of at least one component of an electrochemical reactor, such as a fuel cell. More specifically, this invention relates to the manufacture of printed fluid circuits in the context of manufacturing electrochemical cells, particularly intended for use in fuel cells, and especially for use in fuel cells at temperatures below 250°C. Background Technology

[0002] For example, fuel cells are considered as power systems for future mass-produced motor vehicles and a wide range of other applications. A fuel cell is an electrochemical device that directly converts chemical energy into electrical energy. Combustible materials such as dihydrogen or methanol are used as fuels in fuel cells.

[0003] Proton exchange membrane fuel cells (PEMs) operate at low temperatures typically below 250°C and have a particularly interesting compactness.

[0004] The principle of fuel cells

[0005] A fuel cell is an electrochemical generator that allows chemical energy to be converted into electrical energy through redox reactions.

[0006] Reference Appendix Figure 1 The electrochemical core 5 of the battery is formed by two electrodes 110 separated by an ion exchange membrane 6. The electrodes 110 are supplied with appropriate reagents, namely a combustible material for the anode and a combustion-supporting material for the anode, thereby generating an electrochemical reaction on the surface of the electrodes 110, which will allow the generation of an electric current.

[0007] refer to Figure 2 A fuel cell can be formed by a stack of electrochemical cores 5, 5' arranged in series, referred to as a "stack". Between each stack of electrochemical cores 5, 5', a bipolar plate 3 can be formed to allow the supply of reagents to the electrode 110. Therefore, a fuel cell can be formed by a stack of unit cells separated in pairs by the bipolar plates 3.

[0008] More specifically, a proton exchange membrane fuel cell or PEMFC (“proton exchange membrane fuel cell”) includes at least one cell unit containing a membrane electrode assembly or MEA (110 / 6 / 110) formed by an electrolyte membrane 6 that allows protons to pass selectively, and electrodes 110 throughout the membrane 6.

[0009] Typically, membrane 6 is made of a perfluorosulfonate ionomer such as Nafion. Electrode 110, also known as the catalyst layer or active layer, contains a carbon-supported catalyst, advantageously platinum (Pt), and possible ionomers, which are generally the same as those forming membrane 6.

[0010] At the anode level, dihydrogen (H2), used as fuel, is oxidized to produce protons 6 that pass through the membrane. Electrons produced by this reaction migrate into the fluid loop and then through the circuit 5 outside the cell to form an electric current. At the cathode level, oxygen (O2) is reduced and reacts with the protons passing through the membrane 6 to form water.

[0011] A gas diffusion layer 120 or GDL (“Gas Diffusion Layer”) made of graphite fiber can traditionally be inserted between electrode 110 and bipolar plate 3.

[0012] The principle of bipolar plates

[0013] Bipolar plate 3 ensures a variety of functions, among which in particular:

[0014] - Dispensing reagents and expelling byproducts formed, possibly through channel 2 and / or orifices formed therein;

[0015] - The transfer of electrons generated at the anode of different cell 5 means that the bipolar plate 3 is conductive;

[0016] - Cooling of cell 5 may be achieved through the circulation of coolant within it;

[0017] - Mechanical support for electrochemical core 5.

[0018] You can consider such as Figure 3 The bipolar plate 3 shown is typical and includes three fluid loops, each dedicated to guiding the flow of anolyte fluid, cathode fluid, and cooling fluid (at the center of the plate). This flow guidance is achieved by incorporating obstructions (hereinafter referred to as ribs, such as walls or pillars) that influence the fluid flow. For example, these ribs could be in the form of a bundle of parallel channels 2, referred to herein as "fluid loops." These ribs, which enable electrical and thermal connections to the battery cell, should be conductive.

[0019] Typically, each fluid loop in a fuel cell is made of a conductive material, such as graphite, carbon fiber-reinforced plastic, or a metal, such as stainless steel, a metal alloy, or any other conductive material. Cathode and anode fluids are distributed across the entire active surface of each electrode via channels 2 of the fluid loops. Each fluid loop includes an inlet to allow fluid input and an outlet to allow the discharge of non-reagent fluids and byproducts of the electrochemical reaction.

[0020] To date, the channels 2 of the fluid circuit are still primarily manufactured through machining or by forming the conductive plate 130. In the first case, the material is removed, and in the second case, the channels 2 are created by deformation of the conductive plate 130. The channels 2 of the plate are designed to control the pressure drop of the flow circulating within them.

[0021] More specifically, for reasons related to cost, size, and performance, each fluid loop used in a proton exchange membrane fuel cell is primarily made of stamped metal. Generally, the thickness of the conductive plate 130 is between 1 and 4 mm, and the channel 2 preferably has a width between 0.2 and 2 mm, a depth between 0.2 and 0.5 mm, and a spacing (or tooth width) between 0.2 and 2 mm. The fluid diffusion surface is variable, depending on the cell size and the required power. For high-power applications, circuitry for cooling the fluid is typically inserted between the hydrogen diffusion surface of the anode and the oxygen (or air) diffusion surface of the cathode. Fluid loops can be stacked in two layers, or possibly three layers (e.g., ...). Figure 3 As shown), bipolar plate 3 is formed.

[0022] However, fluid circuits obtained through sheet metal stamping have some drawbacks, among which:

[0023] - Complex manufacturing methods and still high production costs, especially for low-volume production;

[0024] - The curvature of plate 130 caused by the forming process complicates the deposition of the seals used to ensure the sealing of battery 5;

[0025] - The difficulty in further reducing the thickness of plate 130 and its already highly optimized weight significantly impacts the volumetric and mass energy density of the fuel cell; and

[0026] -Due to the limitations in the forming of the metal plate used, it is difficult to reduce the width of channel 2 to improve battery performance.

[0027] To simplify manufacturing processes and reduce the cost of bipolar plates, which account for approximately 40% of the total cost of fuel cells, solutions implemented in the prior art specifically include creating flow barriers by printing flow guides onto a metal or composite planar substrate, and then forming bipolar plates from at least two flow guides. Alternatively, this method allows for the formation of a fluid loop on a gas diffusion layer 120 outside the bipolar plate 3.

[0028] Other arrangements of the fluid circuits not detailed here are possible. For example, the bipolar plate 3 may include only two fluid circuits, each dedicated to one of the two reagents. Furthermore, the bipolar plate 3, including two or three fluid circuits, may be formed from several separate subsets, each subset including at least one fluid circuit. The bipolar plate 3 with the aforementioned functions is then formed during battery assembly when the batteries are stacked and a compressive load is applied to it.

[0029] Fabrication of printed fluid circuits

[0030] refer to Figure 4The printing of the conductive fluid circuit is accomplished by using screen printing masks 11 and 12 containing an image of the fluid circuit to be printed. Conductive ink 7 with very high thixotropic properties passes through the masks 11 and 12 and prints a pattern 21 and 22 that allows the deposition of ribs (also called teeth) on the surface 101 of the substrate 10 to obtain the conductive fluid circuit.

[0031] More specifically, screen printing with a screen is based on the use of a mask or screen 11, 12 formed by two main components: a mesh and a latex. The mesh, stretched within a frame 8, provides mechanical support for the screen 11, 12. Its porosity is limited to allow ink to pass through easily. The latex is deposited on the mesh, and the mesh is impregnated at its deposition sites to form an ink-impermeable layer 7. The voids present in this latex layer are intended to be filled with ink 7 during screen printing. The thickness of the latex layer largely determines the thickness of the deposited ink layer.

[0032] Due to material limitations, printing is not possible with "mesh" screen printing deposits thicker than 200 μm, as this is the maximum latex thickness that "mesh" screen printing mask manufacturers can deposit. In fact, by depositing a thicker latex, the contact area between the ink and the latex increases, while the contact area between the mesh and the latex remains constant. Therefore, for latex thicknesses greater than 200 μm, there is a risk of poor latex retention on the mesh and poor ink retention on the substrate. This reasoning remains unchanged for any printing with a shape factor greater than 0.5, because with larger shape ratios, the contact area between the ink and the latex is too large compared to the contact area between the mesh and the latex.

[0033] For many years, screen printing has been used to manufacture conductive fluid circuits intended for use in PEMFCs. Various patent documents have described, to varying degrees, the printing possibilities in terms of height and width. Information has also been provided regarding the properties (solvents, conductive materials, etc.) and characteristics (viscosity, flow threshold) of the inks used to manufacture these fluid circuits.

[0034] All these documents claim that there are issues related to the height of the printing teeth when printing fluid loops via screen printing (the maximum achievable height is between 200 and 400 μm). Currently, mask manufacturers still cannot exceed a shape factor (printing height / width) of 1, and most screen-printed masks have a shape factor of 0.5 (e.g., corresponding to a 400 μm tooth width for a 200 μm height).

[0035] Some people use multi-layer or multi-layer printing techniques to increase this height, but the manufacturing process is not described in detail. This technique does not allow for the indefinite increase of the height of the printed deposit. In fact, once the substrate 10 is no longer planar, but includes at least one first print with ribs, which partially fill the space in the mask that is normally used to receive ink, each subsequent deposit exacerbates this phenomenon, and the thickness of the deposited layer quickly becomes negligible.

[0036] The problem with this limited printing height is that the smaller the depth of channel 2 in the fluid loop, the greater the voltage drop caused by the loop, thus reducing battery efficiency. However, in the case of printed circuits, there is considerable interest in reducing the width of the tooth / channel step, which inevitably reduces the depth of channel 2, as this is limited by the form factor, which is at most 1 and in most cases 0.5. For example, if the required channel 2 width is 100 μm, it is impossible to exceed a channel depth of 100 μm using current technology. In PEM applications, a fluid loop with both a channel 2 width and depth equal to 100 μm would result in an excessive voltage drop, rendering it unusable.

[0037] Therefore, one object of the present invention is to provide a method for manufacturing printed fluid circuits that allows overcoming at least one disadvantage of the prior art. More specifically, one object of the present invention is to provide a method for manufacturing printed fluid circuits that allows for reducing the width of the tooth / channel steps of the fluid circuit.

[0038] Other objects, features, and advantages of the invention will become apparent upon examination of the following description and drawings. It should be understood that other advantages can be combined. Summary of the Invention

[0039] To achieve this objective, a first aspect of the present invention relates to a method for manufacturing at least one flow guide for an electrochemical reactor, comprising the following steps:

[0040] a. Provide a base,

[0041] b. Providing a first mesh screen including openings, said openings being configured to form a first pattern of ribs in a first guide vane.

[0042] c. Providing a first mesh screen including openings, the openings being configured in a second pattern to form ribs of a first flow guide.

[0043] The second pattern allows the openings of the second screen to be positioned such that, when the second screen is superimposed on the first screen, each opening is simultaneously positioned with the other to align with the opening of the first screen, and the opening of the second screen has a reduced surface area compared to the opening of the first screen; then

[0044] On the first surface of the substrate:

[0045] d. The first layer of the first conductive ink is printed by screen printing using a first screen.

[0046] e. The first pattern of ribs is formed by drying the first layer.

[0047] f. Position the second mesh screen partially on each rib of the first pattern, with each opening of the second mesh screen positioned to align with a rib of the first pattern, then

[0048] g. A second layer of the second conductive ink is printed by screen printing using the previously positioned second screen.

[0049] Thus, after the second layer dries, the second pattern is superimposed on the first pattern.

[0050] Therefore, this invention is based on the innovative use of printing technology through screen printing to manufacture fluid circuits with significant channel depth (>200 μm) and aspect ratio equal to or greater than 1. In fact, by using two different printing masks or screens, printed fluid circuits with a tooth height exceeding 200 μm and an aspect ratio equal to or greater than 1 can be manufactured very simply and at very low additional cost (only one additional screen printing mask).

[0051] A second aspect of the invention relates to a method for manufacturing bipolar plates for electrochemical reactors, particularly for proton exchange membrane fuel cells, comprising:

[0052] - To manufacture at least three flow guides on at least two substrates by the manufacturing method according to the first aspect of the invention, and

[0053] - At least one component of the at least two substrates together, such that the component has one of the at least three flow channels between two of the at least two substrates, and the other two of the at least three flow channels on either side of the at least two substrates.

[0054] The third aspect of the invention relates to a flow guide for an electrochemical reactor, particularly for a proton exchange membrane fuel cell, obtained by implementing a manufacturing method according to the second aspect of the invention.

[0055] The fourth aspect of the invention relates to bipolar plates for electrochemical reactors, particularly for proton exchange membrane fuel cells, obtained by implementing a manufacturing method according to the second aspect of the invention.

[0056] According to other aspects thereof, the present invention may relate to at least one of the following:

[0057] - A flow guide for an electrochemical reactor, for example obtained by implementing a method according to a first aspect of the invention, comprising a substrate having ribs extending on at least one of its two faces defining flow channels, the ribs being made of at least one material different from the material on which the substrate is based and / or having a thickness strictly greater than the width of the flow channels.

[0058] - As described above, each rib extends at least one first portion from at least one of the two faces of the substrate, the thickness of the first portion being substantially equal to the width of the flow channel and made based on a first conductive layer material, and a second portion extending from the first portion having a reduced width compared to the width of the first portion of each rib and made based on a second conductive material, wherein, where appropriate, the second conductive material is different from the first conductive material.

[0059] - A flow guide according to the foregoing features, wherein each rib further includes extending from at least one side of the second portion, preferably from both sides, until it covers a third portion of the second portion where appropriate, the width of the third portion preferably being substantially equal to the width of the first portion and / or preferably extending in alignment with the first portion, the third portion being made of a third conductive material, wherein, where appropriate, the third conductive material is different from at least one of the first conductive material and the second conductive material;

[0060] - A bipolar plate for an electrochemical reactor, particularly for a proton exchange membrane fuel cell, comprising at least three flow guides as described above on at least two substrates assembled together, such that the assembly has one of the at least three flow guides between two of the at least two substrates, and the other two of the at least three flow guides on either side of the at least two substrates.

[0061] - A bipolar plate for an electrochemical reactor, particularly for a proton exchange membrane fuel cell, comprising at least two flow guides as described above on at least one substrate, such that one of the at least two flow guides is located on a first surface of the at least one substrate and another of the at least two flow guides is located on a second surface of the at least one substrate. Attached Figure Description

[0062] The objects, purposes, features, and advantages of the present invention will become more apparent from the detailed description of embodiments thereof, illustrated in the following figures, wherein:

[0063] Figure 1 An exploded perspective view schematically representing a portion of an electrochemical reactor according to one embodiment of the prior art.

[0064] Figure 2 Schematic representation based on Figure 1 The diagram shows a perspective view of the stacked assembly of two parts of the electrochemical reactor according to an embodiment of the invention.

[0065] Figure 3 Indicates according to Figure 1 The illustration shows a perspective view of at least a portion of a bipolar plate located between two electrochemical cores in an electrochemical reactor.

[0066] Figure 4 This is a schematic cross-sectional side view of the printing process, which involves creating a printed pattern through screen printing.

[0067] Figure 5A A top view schematically illustrating a first screen used in a method for manufacturing a flow guide according to a first aspect of the invention.

[0068] Figure 5B schematic representation Figure 5A The first screen shown is based on including Figure 5A The cross-sectional view of the plane of axis AA shown.

[0069] Figure 5C A top view schematically illustrating a second screen used in a method for manufacturing a flow guide according to a first aspect of the invention.

[0070] Figures 6 to 11 Cross-sectional views schematically illustrating different steps of an embodiment of a method for manufacturing a flow guide according to a first aspect of the present invention.

[0071] Figures 12 to 14 Schematic cross-sectional views are shown of examples of the construction of a flow guide obtained by implementing an embodiment of the manufacturing method according to the first aspect of the invention.

[0072] Figure 15 and 16 Each shows a schematic cross-sectional view of a construction example of a bipolar plate obtained by implementing an embodiment of the manufacturing method according to the second aspect of the invention.

[0073] Figure 17 A schematic cross-sectional view is shown of a construction example of a flow guide obtained by implementing an embodiment of the manufacturing method according to the first aspect of the present invention.

[0074] Figure 18 It shows Figure 17 The flow guide is associated with other components of the electrochemical reactor.

[0075] Figure 19A schematic cross-sectional view is shown of a construction example of a flow guide obtained by implementing an embodiment of the manufacturing method according to the first aspect of the present invention.

[0076] Figure 20 It shows Figure 19 The flow guide is associated with another component of the electrochemical reactor.

[0077] The accompanying drawings are provided by way of example only and do not limit the invention. They form illustrative representations of the principles intended to facilitate understanding of the invention and do not necessarily reflect the scale of practical application. In particular, the thickness and width of the different illustrated elements do not necessarily represent actual or real-world shape factors. Detailed Implementation

[0078] Before beginning a detailed review of embodiments of the invention, the following describes optional features that may be used in combination or alternatively.

[0079] According to an embodiment of the first aspect of the invention, the opening of the second screen is configured and positioned such that it can be substantially centered on the rib of the first pattern when the second screen is positioned.

[0080] According to another embodiment of the first aspect of the invention, the first conductive ink and the second conductive ink are identical.

[0081] According to an optional feature of the first aspect of the present invention, the manufacturing method described above may further include the following steps:

[0082] h. Position the first screen such that it is partially disposed on each rib of the second pattern, the opening of the first screen being partially occupied by at least a portion of the rib of the second pattern, and preferably substantially centered on the rib of the second pattern, and

[0083] i. Using the previously positioned first screen, print the third layer of third conductive ink via screen printing.

[0084] This results in the expansion of the ribs of the second pattern after the third ink layer dries, and thus the formation of enlarged ribs.

[0085] Therefore, there is no need to compromise on the mechanical strength of the conductive surfaces or ribs involved.

[0086] According to the aforementioned optional features, the manufacturing method according to the first aspect of the present invention may further include the sequence of at least one of the following steps:

[0087] j. Position the second screen so that it is partially positioned on each enlarged rib, then

[0088] k. Using the previously positioned second screen, another layer of conductive ink is screen-printed, resulting in a second pattern superimposed on the enlarged ribs after drying.

[0089] 1. Position the first screen such that it is partially positioned on each rib of the second pattern prior to printing, the opening of the first screen being partially occupied by at least a portion of the ribs of the second pattern superimposed on the enlarged ribs, and preferably substantially centered on the ribs of the second pattern.

[0090] m. Using the previously positioned first screen, another layer of conductive ink is printed via screen printing.

[0091] This results in the expansion of the ribs that form the second pattern after drying, and thus the formation of new, expanded ribs.

[0092] Based on the previous example, each screen includes mesh and latex, with the first screen positioned above the second pattern such that a portion of its mesh is placed on each rib of the second pattern.

[0093] Alternatively, the method may further include the optional features described above:

[0094] - Provide at least one third screen, the screen including openings in a third pattern configured to form ribs of the first guide.

[0095] - The third pattern allows the openings of the at least one third screen to be positioned such that, when superimposed on a previously used screen, each of the openings of the at least one third screen is aligned in a straight line with the openings of other screens and previously used screens, and the openings of the at least one third screen have a reduced surface area compared to the openings of the previously used screens.

[0096] - Position the at least one third screen such that it is partially disposed on each rib of the previously formed pattern, each opening of the at least one third screen being aligned with a rib of the previously formed pattern, then

[0097] - At least one third conductive ink layer is screen-printed using the previously positioned at least one third screen, such that after the at least one third layer dries, a third pattern is obtained superimposed on the previously formed pattern. Preferably, the opening of the at least one third screen is configured and positioned such that it can be substantially centered on the rib of the previously formed pattern when the at least one third screen is positioned. According to one example, the second conductive ink and the third conductive ink are the same.

[0098] According to an example of a first aspect of the invention, the surface difference between the opening of the second screen and the opening of the first screen is such that when the second screen is located above the first pattern, the second screen is disposed on the upper surface of the rib of the first pattern by more than 5% to 20%.

[0099] According to another embodiment of the first aspect of the invention, the surface difference between the opening of the second screen and the opening of the first screen includes the following and may consist of the following: the width difference between the opening of the second screen and the opening of the first screen is substantially greater than 40 μm, and when the second screen is positioned above the first pattern, the opening of the second screen is even more preferably substantially centered on the rib of the first pattern, because the width difference between the opening of the second screen and the opening of the first screen is close to its minimum value.

[0100] According to another embodiment of the first aspect of the invention, each screen includes mesh and latex, and a second screen is positioned above the first pattern such that a portion of its latex is partially disposed on each rib of the first pattern.

[0101] According to another embodiment of the first aspect of the invention, each screen comprises mesh and latex, the latex having a thickness substantially between 100 and 200 μm, preferably substantially between 150 and 200 μm, and more preferably substantially equal to 200 μm and / or the mesh having a thickness substantially between 50 and 150 μm, preferably substantially between 80 and 120 μm, and even more preferably substantially equal to 100 μm.

[0102] According to another embodiment of the first aspect of the invention, the first screen comprises mesh and latex, the latex of the first screen having a pattern that is a substrate of a first pattern and defines a flow channel for a first guide between ribs of the first pattern, the width of which is defined by the opening of the first screen, the width of the flow channel being substantially between 1 and 4 times the width of the ribs of the first pattern, preferably substantially between 1 and 2 times the width of the ribs of the first pattern, and more preferably substantially equal to the width of the ribs of the first pattern.

[0103] According to another embodiment of the first aspect of the invention, each print is performed by screen printing while applying shear stress to each layer of conductive ink, the viscosity of the printed ink being between 70 and 500 Pa·s (for 0.1 s). -1 The shear rate), and the viscosity of the printing ink is between 2.5 and 7 Pa·s (for 100 s). -1 (shear rate). Conductive inks with these properties exhibit very high thixotropy.

[0104] According to another embodiment of the first aspect of the invention, the provided substrate includes at least one of a gas diffusion layer of an electrochemical reactor, an electrode layer of an electrochemical reactor, and a conductive plate.

[0105] According to another embodiment of the first aspect of the invention, the provided substrate is a conductive plate, and steps d to g of the method are repeated on a second surface of the substrate to fabricate a second current conductor therein. Additionally, steps h and i, and possibly h to m, may be repeated on the second surface of the substrate to fabricate a second current conductor therein.

[0106] For a first element that can be superimposed on a second element, it should be understood that the projection of the first element in the superposition plane between the elements is completely tangent to the projection of the second element in the same superposition plane, and vice versa.

[0107] For a parameter that is substantially equal to / higher than / lower than a given value, it should be understood that the parameter is equal to / higher than / lower than the given value, within 20% of that value, and possibly within 10%. For a parameter that is substantially contained between two given values, it should be understood that the parameter is at least equal to the given minimum value, within 20% and possibly 10% of that value, and at most equal to the given maximum value, within 20% or even less than 10% of that value.

[0108] To address the printing height issue through mesh screen printing, particularly for manufacturing guides specifically for PEM applications, a technique was conceived and implemented: tapered printing.

[0109] Conical printing is carried out by performing a method according to the first aspect of the invention for manufacturing at least one flow guide for an electrochemical reactor.

[0110] refer to Figure 4 and 5A Up to 5C, the method according to the first aspect of the present invention first includes the following steps:

[0111] - Provides base 10,

[0112] - Provides a first mesh screen 11 including an opening 111, the opening 111 being configured to form a first pattern 21 of ribs 211 of a first guide 1, and

[0113] - Provides a second mesh screen 12 including an opening 121, the opening 121 being configured to form a second pattern 22 of the ribs 221 of the first guide 1.

[0114] Each screen 11, 12 includes meshes 112, 122 and latex 113, 123. Typically, each latex 113, 123 has a thickness substantially between 100 and 200 μm, preferably substantially between 150 and 200 μm, and more preferably substantially equal to 200 μm; and each mesh 112, 122 has a thickness substantially between 50 and 150 μm, preferably substantially between 80 and 120 μm, and even more preferably substantially equal to 100 μm. Nevertheless, the invention is not limited to such values ​​for the thickness of the latex and / or meshes. Furthermore, other parameters, such as the mesh size of each mesh, may be considered.

[0115] exist Figure 5B In the image, it is observed that the opening 111 of the first screen 11 corresponds to the area of ​​the first screen 11 not covered by the latex 113. At its opening 111, it is also observed that the mesh 112 of the first screen 11 is not soaked with the latex 113. Therefore, the ink to be printed through this screen 11 will pass through the mesh 112 and fill the blank space left by the latex 113.

[0116] The second screen 12 has a corresponding structure. Nevertheless, the second pattern 22 can overlap with the first pattern 21, and the opening 221 of the second screen 12 has a reduced surface area compared to the opening 211 of the first screen 21.

[0117] In other words, if we take Figure 5A and 5C Cut them open, stack them on top of each other (openings pointing in the same direction), and observe the stacking achieved through transparency. We notice that each opening 121 of the second screen 12 is inserted within an opening 111 of the first screen 11. Figure 5A and 5C In the example shown, only the ends of openings 111 and 121 overlap each other because the opening 121 of the second screen 12 is longitudinally centered relative to the opening 111 of the first screen 11. In fact, Figure 5A and 5C The superposition on top of each other will show that the longitudinal shape of each opening 111 has a midline along its length that coincides with the midline of the longitudinal shape of the opening 121 superimposed with it.

[0118] Having openings 111 and 121 of the same length, the surface difference between opening 121 of the second screen 12 and opening 111 of the first screen 11 is composed of the width difference between opening 121 of the second screen 12 and opening 111 of the first screen 12. Preferably, this difference is greater than 40 μm. Furthermore, the opening 121 of the second screen 12 is even more preferably substantially centered on the opening 111 of the first screen 11, because the width difference between the opening 121 of the second screen 12 and the opening 111 of the first screen is close to its minimum value, i.e., substantially 40 μm.

[0119] More specifically, the second printed layer 32 is preferably narrower than the first printed layer 31, at least 20m on each side, typically 50m on each side, so that the second screen 12 has sufficient support to stably bear the ribs 211 of the first pattern 21.

[0120] More generally, it is preferred that the surface difference between each opening 121 of the second screen 12 and each opening 111 of the first screen 11 superimposed thereon is between 5% and 20% of the surface area of ​​the opening 111. In this way, regardless of whether the openings 111 and 121 can be centered on top of each other, the second screen 12 is ensured to have supports that are stably supported on the ribs 211 of the first pattern 21.

[0121] It should be noted that openings 111 and 121, as well as ribs 211 and 221, are not limited to straight shapes or parallel distributions.

[0122] More specifically, the three circulation modes of the reagent or coolant in flow channel 2 can be substantially distinguished:

[0123] - Serpentine tunnel: One or more tunnels traverse the entire activity area in several round trips;

[0124] - Parallel passageways: A cluster of parallel and open passageways runs through the entire event area; and

[0125] - Cross-channel: A bundle of parallel and blocked channels runs through the entire active area. Each channel is blocked at either the inlet or outlet side. Fluid entering a channel is then confined to a later localized gas diffusion path to join an adjacent channel and subsequently reach the fluid outlet of that adjacent channel.

[0126] The manufacturing method according to the first aspect of the invention is suitable for manufacturing the flow guide 1 according to at least any one of the three circulation modes described above.

[0127] refer to Figures 6 to 9 The manufacturing method according to the first aspect of the present invention further includes the following steps, performing the following on the first surface 101 of the substrate 10:

[0128] - Using the first screen 11, a first layer 31 of the first conductive ink is screen-printed, for example, as shown in the image. Figure 6 As shown in the diagram,

[0129] - The first pattern 21 of the rib 211 is formed by drying the first layer 31, for example, as shown in the figure. Figure 7 As shown in the diagram,

[0130] - Position the second screen 12 such that it is partially placed on each rib 211 of the first pattern 21, then

[0131] - Using the previously positioned second screen 12, a second layer 32 of the second conductive ink is screen-printed, for example, with... Figure 8 As shown in the diagram.

[0132] Therefore, after drying the second layer 32, a second pattern 22 is obtained superimposed on the first pattern 21, for example, as shown in the figure. Figure 9 As shown in the diagram.

[0133] It should be noted here that, according to Figure 5A and 5C In the example shown, each opening 111 and each opening 121 superimposed thereon can be centered on each other. When the first and second screens 11 and 12 are superimposed on each other, when the second screen 12 is positioned on the rib 211 of the first pattern 21, the opening 121 of the second screen 12 is configured and positioned substantially centered on the rib 211 of the first pattern 21.

[0134] Therefore, it is demonstrated that implementation of the method according to the first aspect of the invention can indeed achieve conical printing, wherein the width of the conductive ink layer 32 to be printed on the existing layer 31 is small. During the printing of the second layer 32, the second screen 12 is positioned above the ribs 211 of the first pattern 21, rather than above the substrate 10, which allows for some printable height at a distance relative to the substrate 10 that is substantially equal to the thickness of the ribs 211 of the first pattern 21.

[0135] It should be noted that, such as Figure 8 As shown, the second mesh 12 is more specifically located on a portion of each rib 211 of the first pattern 21, and specifically on a portion of their top, through a portion of their latex 123.

[0136] Where appropriate, conical printed matter having more than two layers can be manufactured due to specific embodiments of the method according to the first aspect of the invention.

[0137] Therefore, the method according to the first aspect of the present invention may further include the following steps:

[0138] - A third screen is provided, which includes openings in a third pattern configured to form ribs of the first guide 1.

[0139] The third pattern can overlap with the second pattern 22, and compared with the opening 121 of the second screen 12, the opening surface of the third screen is reduced.

[0140] - Position the third screen so that it partially rests on each rib 221 of the second pattern 22, then

[0141] - Using the previously positioned third screen, a third conductive ink layer is printed by screen printing, thereby obtaining a third pattern superimposed on the second pattern 22 after the third layer dries.

[0142] like Figure 5A and 5C In the example shown, the opening of the third screen can also be configured and positioned such that when the third screen is positioned on the rib 221 of the second pattern 22, it can be substantially centered on the rib 221 of the second pattern 22.

[0143] Provided the width of the final printed layer is sufficient to support the new layer (typically, as long as the width of the final printed layer is substantially greater than 200 μm) and as long as a finer screen printing mask is available, the cone growth operation can be updated as desired multiple times.

[0144] This conical growth is characterized by increasing the speed of manufacturing by limiting the number of printing steps (potentially without steps to expand the previously formed ribs) without compromising the height of the formed ribs. The narrower top layer compensates, where appropriate, for the disadvantages inherent in this conical growth, namely, the reduction in the cross-sectional area of ​​the fluid channel at that level, starting from the bottom which must be wide enough to support at least two layers.

[0145] However, although the manufacturing method according to the first aspect of the invention makes it possible to have more than two layers of conical printing, it is more advantageous to consider that, from Figure 9 Starting with the construction shown, the first aspect of the invention, according to the method of the present invention, further includes, for example, as... Figure 10 As shown, the following steps are:

[0146] - Position the first mesh screen 11 such that it partially rests on each rib 221 of the second pattern 22, the opening 111 of the first mesh screen 11 being partially occupied by at least a portion of the rib 221 of the second pattern 22, and preferably substantially centered on the rib 221 of the second pattern 21, and

[0147] - Using the previously positioned first screen 11, the third layer 33 of the third conductive ink is screen printed.

[0148] In this way, after the third ink layer 32 dries, the ribs 221 of the second pattern 22 are enlarged, and thus the enlarged ribs 222 are obtained, for example, as shown in the figure. Figure 11 As shown.

[0149] It should be noted that, such as Figure 10 As shown, when the pattern is printed on the third layer 33, the first screen 11 is placed more specifically on each rib 221 of the second pattern 22 through a portion of its mesh 112, particularly on top of them.

[0150] It should also be noted that, such as Figure 11 As shown, the deposition of the third conductive ink layer 33 can also cause additional enlargement of the ribs compared to the height of the ribs 221 of the second pattern 22. However, this enlargement is limited by the thickness of the mesh 112 of the first screen 11.

[0151] The results showed that ribs 222 could be increased in height by doubling, tripling, or even quadrupling them, by repeating the following steps as many times as possible:

[0152] - Position the second screen 12 so that it rests partially on each of the enlarged ribs 222, then

[0153] - Using the previously positioned second screen 12, another layer of conductive ink is screen-printed to obtain a second pattern superimposed on the enlarged ribs 22 after drying.

[0154] - Position the first screen 11 such that it partially rests on each rib of the previously printed second pattern, the opening 111 of the first screen 11 being occupied by at least a portion of the ribs of the second pattern that overlap with the enlarged ribs 222, and preferably substantially centered on the ribs of the second pattern, and

[0155] - Use the previously positioned first screen 11 to screen print another layer of conductive ink.

[0156] Each repetition of the sequence of steps listed above ensures that the height of the rib enlargement is approximately equal to the height of the enlarged rib 222, without any compromise on the width of the upper layer of the rib.

[0157] For example, these variations of the conical printing technique described above are called "alternating conical printing".

[0158] This alternating conical printing technique allows for increased rib height while ensuring good support for each screen used to print new ink layers by adding at least one printing step using the first screen 11, or alternatively, screens with very similar opening widths. At each alternation, the fine ribs 221 already added to the first pattern 21 are finished with new conductive ink 33.

[0159] Therefore, ribs 222 with a width substantially the same as that of the ribs 211 of the first pattern are obtained. Layers can then be stacked again, always starting with ribs of the same width, without having more than two screens (or equivalent screen printing masks) and without being limited by the width of the first formed ribs 211 (unlike the so-called conical printing technique described above).

[0160] In particular, this enlarged rib 222 has better mechanical strength and a larger contact surface compared to the rib 221 of the second pattern 22, especially for electrical contact with other components of the electrochemical reactor, which are intended to be assembled on the first guide 1, as shown below. Figures 12 to 20 One of the ways shown and discussed.

[0161] exist Figures 6 to 11 In each of these, different textures are used to illustrate each used ink, indicating that each printing step can be performed with a conductive ink specific to it. Therefore, each enlarged rib 222 can be formed from one, two, or three conductive inks. Thus, the composition of the printed conductive inks can be adjusted, for example, to change their conductivity, their mechanical strength, or the manufacturing cost associated with implementing the method according to different variations of the first aspect of the invention.

[0162] More specifically, the possibility of varying the ink formulation for each layer allows for, for example:

[0163] - To vary the wet angle of the teeth along their height to improve water drainage from the electrochemical cell intended to integrate the guide tube 1, and / or

[0164] - The finest sediments (in Figure 11 In the example shown, the deposition of ribs 221 in the second pattern 22 can produce different mechanical properties, such as greater stiffness or better cohesion, where appropriate, at the expense of its conductivity, and / or

[0165] - The finest sediments (in Figure 11 The deposition of rib 221 in the second pattern 22 shown in the example may contain elements (e.g., metal particles) that are almost incompatible with the surrounding environment to which the fuel cell is intended to be integrated, because the deposition is encapsulated by the widest deposition (the deposition of the third layer 33) (particularly through at least three of its sides, such as...). Figure 11 (as shown), and if the widest sediment has sufficient protection.

[0166] Therefore, the present invention provides advantageous possibilities for variations in the conductive inks to be printed. Nevertheless, it is preferable to say that each of these inks possesses very high thixotropic properties. More specifically, such inks are characterized in that their printing via screen printing can be effectively carried out by applying shear stress, such as... Figure 4 As shown, the ink has:

[0167] - When applied to it, the force is approximately equal to 0.1s. -1 At a shear rate of [value missing], the viscosity is generally between 70 and 500 Pa·s, and [missing information].

[0168] - When applied to it, the force is approximately equal to 0.1s.-1 At a shear rate of 100 s, the viscosity is generally between 2.5 and 7 Pa·s.

[0169] Another parameter relating to the guide 1 manufactured by implementing the method according to the first aspect of the invention relates to the width of the flow channel 2. According to the above embodiment, the latter is defined by a first mesh screen 11. In fact, the latex 113 of the first mesh screen 11 has a pattern opposite (negative) to the first pattern 21 of the ribs 211, and the width of the flow channel 2 of the guide 1 is defined between these patterns. Furthermore, it should be noted that the width of the ribs 211 of the first pattern 21 is defined by the openings 111 of the first mesh screen 11. Therefore, it has been shown that, particularly when the first mesh screen 11 defines ribs 211 having a shape factor substantially equal to 1 (between width and height) and a flow channel 2 having a width substantially equal to the width of the ribs 211, by implementing the method according to the first aspect of the invention, the width of the flow channel 2 can ultimately be substantially based on between 1 and 4 times the width of the ribs 211 of the first pattern 21, preferably substantially between 1 and 2 times the width of the ribs 211 of the first pattern 21, and more preferably substantially equal to the width of the ribs 211 of the first pattern 21. Therefore, thanks to the manufacturing method according to the first aspect of the invention, the shape factor between the width and depth of the flow channel 2 is no longer limited to 1, thus reducing the width of the tooth / channel step ( Figure 11 The reference P in the figure does not inevitably lead to a reduction in the depth of the flow channel 2. Therefore, due to the different variations of the manufacturing method according to the first aspect of the invention described above, the interesting technical obstacles that have limited printed fluid circuits to date have been advantageously overcome.

[0170] The manufacturing method according to the first aspect of the invention can also be repeated on the surface 102 of the substrate 10 to manufacture the second guide 1' on the surface 102, for example, in one of the ways shown. Figures 12 to 14 One approach. It should be noted here that, unlike the electrode layer 110 and gas diffusion layer 120 of the electrochemical reactor, these embodiments are more particularly suitable for substrates including a purely conductive plate 130 or made of a purely conductive plate 130.

[0171] For example, this conductive plate 130 can be made based on a metal selected from, for example, stainless steel, aluminum, or titanium. The metal can be protected, for example, by carbonation or metallization deposition or by an electronically conductive composite polymer including a metallization layer, to protect the plate 130 from corrosion or reduce contact resistance. The plate 130 can be substantially rigid. Preferably, it has a thickness between 0.01 and 1 mm, more preferably between 0.02 and 0.1 mm.

[0172] exist Figure 12In the example shown, a first flow guide 1 is manufactured on the upper surface 201 of the conductive plate 130 by implementing the method according to the first aspect of the invention, and a second flow guide 1' is manufactured on the lower surface 202 of the plate 130. Thus, flow channels are formed on either side of the plate 130 between the ribs. In this example, the ribs on two opposing surfaces extend parallel to each other, have the same dimensions, and overlap: the ribs on the two surfaces are symmetrical to each other with respect to the plate 130.

[0173] exist Figure 13 In the example shown, the ribs on the two opposite faces extend parallel to each other and have the same dimensions, but are displaced in a direction transverse to their main extension direction.

[0174] exist Figure 14 In the example, the ribs on the two opposite sides extend in a vertical direction.

[0175] These examples are intended to illustrate that any variation between the first flow guide 1 manufactured on the first surface 101 of the substrate 10 and the second flow guide 1' manufactured on the second surface 102 of the substrate 10 can be considered to manufacture one of the flow guides 1 and 1' according to any variant of the first aspect of the invention, without limiting the manufacture of the other of any variant of the first aspect of the invention. For example, each of the first and second flow guides 1 and 1' manufactured on either side of the same plate 130 can have any of the three circulation patterns described above.

[0176] Examples of implementing the method according to the first aspect of the invention enable the manufacture of conductive fluid circuits having the following characteristics:

[0177] Tooth 222 with a width of -400μm

[0178] - Channel 2 with a width of 400μm, and

[0179] Teeth with a height of -400μm.

[0180] Therefore, the first screen 11 may have a latex thickness 113 of 200 μm and an opening width 111 of 400 μm, and the second screen 12 may have a latex thickness 123 of 200 μm and an opening 121 of 300 μm.

[0181] The first printing step allows for the formation of teeth 211 that are 400 μm wide and 200 μm high. The second and third printing steps allow for the formation of enlarged teeth 222 that are 400 μm wide and 400 μm high.

[0182] The second aspect of the invention relates to a method for manufacturing a bipolar plate, particularly for PEM applications. First, the manufacturing method according to the second aspect of the invention includes one of the above-described variations of the manufacturing method according to the first aspect of the invention. Then, it involves assembling a plurality of flow guides 1, 1' manufactured in this manner together. An example of such a bipolar plate 3 is shown in... Figure 15 and 16 Each of them is shown in the table.

[0183] Figure 15 A bipolar plate 3 is shown, which is formed by stacking guides 1, 1', and 1" obtained by implementing one of the above-described variations of the manufacturing method according to the first aspect of the invention. In this example, the three guides 1, 1', and 1" are manufactured from three substrates 10, 10', and 10" respectively. The three guides include ribs on one surface. The upper guide 1 has ribs projecting from the upper surface of the substrate 10. The middle guide 1' and the lower guide 1" have ribs 31 projecting from the underside of the substrates 10' and 10" respectively. When the three guides 1, 1', and 1" are stacked, the flow channels of the reagent converge between the ribs of the upper guide 1, the flow channels of the heat transfer liquid converge between the ribs of the middle guide 1', and the flow channels of another reagent converge between the ribs of the lower guide 1"

[0184] Figure 16 A bipolar plate 3 is shown, which is formed by stacking guides 1, 1', and 1" manufactured from two substrates 10 and 10', according to one of the above-described variations of the manufacturing method according to the first aspect of the invention. In this example, three guides 1, 1', and 1" are stacked together. The upper guide 1 and the middle guide 1' share the same substrate 10 and are formed as shown. Figure 4 The configuration shown 2 includes a substrate 10 that is a purely conductive plate 130. Therefore, as shown, this plate 130 includes ribs projecting from both of its surfaces. The lower guide 1” has ribs projecting from the lower surface of the substrate 10”. Figure 15 As shown, when the three guides 1, 1' and 1” overlap, the flow channels of the reagent converge between the ribs of the upper guide 1, the flow channels of the heat transfer liquid are formed between the ribs of the middle guide 1', and the flow channels of another reagent converge between the ribs of the upper guide 1''.

[0185] Figure 17 This is a schematic cross-sectional view of a flow guide according to another embodiment of the present invention. The substrate 10 on which a layer of conductive ink is printed by screen printing is herein a gas diffusion layer 120. The ink can be printed on one side 101 of the gas diffusion layer 120, with printing parameters similar to those described above. The flow guide 1 is obtained on the gas diffusion layer 120 by implementing one of the above-described variations of the manufacturing method according to the first aspect of the present invention.

[0186] Figure 18This is a schematic cross-sectional view of the flow guide 1 obtained by implementing one of the above-described variations of the manufacturing method according to the first aspect of the invention, in relation to other components of the electrochemical reactor. Conductive plate 130, as shown in the reference... Figures 12 to 14 As detailed in the described embodiment, it can be pressed against the top of the ribs of the flow guide 1. The membrane electrode assembly, including the membrane 6 and two electrodes 110, is pressed against the lower surface of the gas diffusion layer 120 that supports the flow guide ribs.

[0187] Figure 19 This is a schematic cross-sectional view of the flow guide 1 obtained by implementing one of the above-described variations of the manufacturing method according to the first aspect of the invention, in relation to other components of the electrochemical reactor. The substrate 110 on which at least the first two conductive ink layers 31 and 32 have been screen-printed herein is the electrode 110 fixed to the proton exchange membrane 6 of the membrane electrode assembly before or after printing. The ink can be printed on the surface of the electrode 110 with printing parameters similar to those described above.

[0188] Figure 20 yes Figure 19 The schematic cross-sectional view of the component shown is associated with another part of the electrochemical reactor, namely the conductive plate 130. The latter can be compared with the reference... Figures 12 to 14 Similarly, in the described embodiments, it can be pressed against the top of a rib extending from the surface of one of the electrodes 110.

[0189] The present invention is not limited to the embodiments described above.

[0190] For example, each conductive ink layer 31, 32, and 33 can be printed multiple times, and each then forms a multilayer. This allows for increased deposition density and / or height. In this case, the drying stage is repeated as many times as the number of layers in each multilayer.

[0191] It should be noted that the drying stage can be carried out, for example, in an oven at a temperature of approximately 80°C for a period of approximately 10 minutes.

[0192] This invention can be applied to any type of electrochemical reactor that requires at least one fluid loop, particularly for the feeding of reagents and the evacuation of reaction products and / or the circulation of cooling fluids. Among these electrochemical reactors, not only fuel cells, as mentioned above, can be mentioned, but also, as another example, electrolyzers.

[0193] Finally, it should be noted that the present invention can manufacture fluid circuits with narrow flow channels, i.e., widths less than 400 μm, which cannot be mass-produced by stamping.

Claims

1. A method for manufacturing at least one flow guide for an electrochemical reactor, comprising the following steps: a. Provide a base, b. Providing a first mesh screen including openings, said openings being configured to form a first pattern of ribs in a first guide vane. c. Provide a second screen, including openings in a second pattern configured to form ribs of the first flow guide. The second pattern allows the openings of the second screen to be positioned such that, when the second screen is superimposed on the first screen, each opening is simultaneously positioned with other openings to align with the openings of the first screen, and the openings of the second screen have a reduced surface area compared to the openings of the first screen; then On the first surface of the substrate: d. A first layer of the first conductive ink is printed by screen printing using the first screen. e. The first pattern of ribs is formed by drying the first layer. f. Position the second mesh screen partially on each rib of the first pattern, with each opening of the second mesh screen positioned to align with a rib of the first pattern, then g. A second layer of the second conductive ink is printed by screen printing using the previously positioned second screen. Thus, after the second layer dries, the second pattern is superimposed on the first pattern. The method further includes the following steps: h. Position the first screen so that it partially rests on each rib of the second pattern, the opening of the first screen being occupied by at least a portion of the rib of the second pattern, and i. A third layer of the third conductive ink is printed using screen printing on the previously positioned first screen. Thus, after the third layer dries, at least one of the ribs of the second pattern is enlarged, and thus an enlarged rib is obtained.

2. The method according to claim 1, wherein, The opening of the second screen is configured and positioned such that, when the second screen is positioned, it is substantially centered on the rib of the first pattern.

3. The method of claim 1, further comprising at least one sequence of the following steps: j. Position the second screen so that it partially rests on each of the enlarged ribs, then k. Print another layer of conductive ink using screen printing on the previously positioned second screen to obtain an overlay of the second pattern on the enlarged ribs after drying, then 1. Position the first screen so that it partially rests on each rib of the previously printed second pattern, the opening of the first screen being partially occupied by at least a portion of the ribs of the second pattern that overlap with the enlarged ribs, and m. Print another layer of conductive ink using screen printing on the previously positioned first screen. So that after drying, the ribs of the second pattern are enlarged, and thus new enlarged ribs are obtained.

4. The method according to claim 1, wherein, The surface difference between the opening of the second screen and the opening of the first screen is such that when the second screen is positioned on the first pattern, the second screen is located on 5% to 20% of the upper surface of the rib of the first pattern.

5. The method according to claim 1, wherein, The surface differences between the opening of the second screen and the opening of the first screen include the following: The width difference between the opening of the second screen and the opening of the first screen is greater than 40 μm.

6. The method according to claim 1, wherein, Each screen includes mesh and latex, and the second screen is positioned on the first pattern such that a portion of its latex partially lies on each rib of the first pattern.

7. The method according to claim 1, wherein, Each screen includes mesh and latex, with the first screen positioned on the second pattern such that a portion of its mesh is located on each rib of the second pattern.

8. The method according to claim 1, wherein, Each screen consists of mesh and latex. The thickness of the latex is between 100 and 200 µm, and / or The thickness of the mesh is between 50 and 150 µm.

9. The method according to claim 8, wherein, The thickness of the latex is between 150 and 200 µm.

10. The method according to claim 8, wherein, The thickness of the latex is approximately 200 µm.

11. The method according to claim 8, wherein, The thickness of the mesh is between 80 and 120 µm.

12. The method according to claim 8, wherein, The thickness of the mesh is 100 µm.

13. The method according to claim 1, wherein, The first screen includes mesh and latex, the latex pattern of the first screen is the reverse of the first pattern and defines a flow channel of the first guide between the ribs of the first pattern, the width of which is defined by the opening of the first screen, and the width of the flow channel is between 1 and 4 times the width of the ribs of the first pattern.

14. The method according to claim 13, wherein, The width of the flow channel is between 1 and 2 times the width of the ribs in the first pattern.

15. The method according to claim 13, wherein, The width of the flow channel is substantially equal to the width of the ribs in the first pattern.

16. The method according to claim 1, wherein, Each layer of conductive ink is printed by screen printing while applying shear stress to that layer, for 0.1 s. -1 The shear rate, the viscosity of the printing ink is between 70 and 500 Pa·s, and for 100 s -1 The shear rate is such that the viscosity of the printing ink is between 2.5 and 7 Pa·s.

17. The method according to claim 1, wherein, The provided substrate includes at least one of the gas diffusion layer of the electrochemical reactor, the electrode layer of the electrochemical reactor, and the conductive plate.

18. The method according to claim 1, wherein, The provided substrate is a conductive plate, and steps d to g of the method are repeated on the second surface of the substrate to fabricate a second current guide therein.

19. The method according to claim 1, wherein, The provided substrate is a conductive plate, and steps d to g and steps d to i of the method are repeated on the second surface of the substrate to fabricate a second current guide therein.

20. The method according to claim 3, wherein, Steps j to m are repeated on the second surface of the substrate to manufacture the second flow guide therein.

21. A method for manufacturing a bipolar plate for an electrochemical reactor, comprising: • To manufacture at least three flow guides on at least two substrates by the method according to any one of claims 1 to 20, and • At least one component of the at least two substrates together, such that the component has one of the at least three flow guides between two of the at least two substrates, and the other two of the at least three flow guides on either side of the at least two substrates.

22. The method of claim 21, wherein the electrochemical reactor is a proton exchange membrane fuel cell.

23. A flow guide for an electrochemical reactor, comprising a substrate, ribs extending from at least one of two faces of the substrate defining flow channels, the ribs being made of at least one conductive material different from the material on which the substrate is based, and the ribs having a thickness substantially greater than the width of the flow channels, wherein each rib extends at least one first portion from at least one of the two faces of the substrate, which is made of a first conductive material different from the substrate; at least one second portion extending from the first portion, having a reduced width compared to the width of the first portion of each rib, and being made of a second conductive material different from the substrate, wherein, where appropriate, the second conductive material is different from the first conductive material; and a third portion extending from at least one side of the second portion until, where appropriate, covering the second portion, the third portion being made of a third conductive material, which, where appropriate, is different from at least one of the first and second conductive materials.

24. The flow guide according to claim 23, wherein, The third portion extends from both sides of the second portion until it covers the second portion where appropriate.

25. The flow guide according to claim 23, wherein, The width of the third portion is substantially equal to the width of the first portion and / or extends in alignment with the first portion.

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