DE102018203406A1 - Gas distributor structure for a fuel cell - Google Patents

Abstract

The invention relates to a gas distributor structure (10) for a fuel cell (100), which serves for providing a reactant to the fuel cell (100) and which can be arranged between a bipolar plate (101) and a membrane electrode unit (MEA), comprising a first region (11 ) with a first, in particular channel-shaped, distributor structure (S1) for providing the reactant into the fuel cell (100) and a second region (12) with a second, in particular porous, distributor structure (S2) for forwarding the reactant in the fuel cell (100) in which, viewed in the gas flow direction (x) of the reactant, the second region (12) adjoins the first region (11).

Description

The invention relates to a gas distribution structure for a fuel cell, in particular a PEM fuel cell, or an electrolyzer, which serves to provide a reactant to the fuel cell, according to the independent device claim. Furthermore, the invention relates to a corresponding fuel cell according to the independent device claim.

State of the art

Fuel cells are electrochemical energy converters in which hydrogen H2 and oxygen 02 are converted into water H2O, electrical energy and heat. The 1a schematically shows a structure of a known fuel cell 100 *, for example. A PEM fuel cell with an operating temperature below 120 ° C. A stack or repeating unit of this structure forms a (fuel cell) stack, like the 1b shows. The reactants, hydrogen H2 and oxygen 02, for example from a simple ambient air, as well as cooling liquid, for example water H20, are introduced into the fuel cell 100 * via special gas distributor structures 10 *, 20 *. Known gas distributor structures 10 *, 20 * are usually either as a channel-shaped distributor structure S1 in an embossed sheet or as a porous manifold structure S2 , For example, from a wire mesh, mesh, metal foam or similar structures implemented. On one side of the gas distributor structures 10 *, 20 * flows a reactant (eg oxygen 02 of the air or hydrogen H2), on the other side flows the cooling liquid H2O. The gas distributor structures 10 *, 20 * in the form of embossed sheets are simple, inexpensive components. A disadvantage of embossed sheets, however, is that under the webs of such a channel structure on the cathode side K of the fuel cell 100 * product water can accumulate. This product water can be the mass transport of the reactants H2 or 02 towards a catalyst layer E1 on a membrane 103 block, whereby the performance of the fuel cell 100 * can break. The product water can better through the porous distribution structures S2 discharged or transported away. The gas distributor structures 10 *, 20 * in the form of porous distributor structures S2 However, they are more expensive and expensive to produce than embossed sheets. In addition, porous distribution structures effect S2 a large pressure drop during transport of the reactant, so that a larger compressor on the cathode side K is necessary, which in turn requires more energy for its operation.

Disclosure of the invention

The invention provides a gas distributor structure for a fuel cell, in particular a PEM fuel cell, or for an electrolyzer, which serves to provide a reactant to the fuel cell, having the features of the independent device claim and a fuel cell with at least one corresponding gas distributor structure with the characteristics of the independent independent Device claim before. Further advantages, features and details of the invention will become apparent from the dependent claims, the description and the drawings. In this case, features and details that are described in connection with the gas distributor structure according to the invention apply, of course, also in connection with the fuel cell according to the invention and in each case vice versa, so that with respect to the disclosure of the individual aspects of the invention always reciprocal reference is or may be.

The present invention provides a gas distributor structure for a fuel cell, in particular a PEM fuel cell, or an electrolyzer, which serves to provide a reactant to the fuel cell, comprising a first region having a first, in particular channel-shaped, for example embossed, distributor structure for providing the Reactants in the fuel cell, and a second region having a second, in particular porous, foam-shaped, distribution structure for forwarding the reactant in the fuel cell, wherein seen in the gas flow direction of the reactant, the second region is connected to the first region or is fluidly connected , For the purposes of the present invention, the term "porous" is understood to mean an open-pored, media-permeable structure.

The gas distributor structure according to the invention may be advantageous on the cathode side of the bipolar plate in order to avoid water accumulation on the membrane. On the anode side, a bipolar plate may further comprise an embossed metallic sheet. A coolant can be accommodated between the two distributor structures.

An idea of the invention lies in the fact that the gas distributor structure on the air side or cathode side of a fuel cell in the front first region has a first, in particular channel-shaped, distributor structure, which is formed from a cost-effective stamped sheet metal. In contrast, in the rear second area, a second, in particular porous, distribution structure is connected to the embossed sheet, which may optionally be joined to the first distribution structure. The first, in particular channel-shaped, distribution structure is advantageously inexpensive and completely sufficient in the front first region on the cathode side, since the air is typically supplied completely dry to the fuel cell, and the accumulation of product water tends to form in the rear second area of the gas distribution structure. There, in the second area, the somewhat more expensive second, in particular porous, distribution structure can now be provided, which avoids the accumulation of product water in the gas diffusion layer or on the catalyst layer and favors removal of the product water. The invention recognizes that with increasing gas flow through the fuel cell at high current density more and more product water is obtained, which can be liquid at low operating conditions (T <100 ° C). However, the second porous distribution structure, for example in the form of an open-pore metal foam, a metal mesh or a metal mesh, reliably ensures that the product water can be transported away with the gas flow of the reactant (for example air). With the use of a low-cost first distribution structure, the invention ensures that the costs in the gas distribution structure are optimized, in particular reduced. With the use of a more expensive, but also finer second distribution structure, the invention again ensures that the product water is safely discharged from the fuel cell. In addition, in the case of the gas distributor structure according to the invention, the advantage of a reduced pressure drop in the gas flow direction of the reactant arises, since the air is introduced into relatively wide channels of the first distributor structure with reduced flow resistance.

Furthermore, provision may be made for the first region to have an embossed sheet, through which the first distribution structure is formed. Such a first distribution structure can be produced inexpensively and easily. In addition, such a distribution structure ensures a reduced flow resistance in the first region of the gas distributor structure.

Furthermore, it is advantageous that the first distributor structure is made of titanium, copper, aluminum or stainless steel. Such materials help to make a reliable electrical contact. In addition, such materials are easy to process, form and electrically bond (eg, by welding, soldering, sintering, melting or the like). The production of the first distributor structure can thereby be facilitated. Furthermore, it is conceivable that the distributor structure can be provided with a coating.

It is also conceivable that the first distributor structure is periodically formed. By a periodic (same repetitive geometric design) first distribution structure, the gas flow can be set and predicted in a simple manner. For this purpose, a compressor can be controlled accordingly.

In addition, it may be provided in the context of the invention that the second region comprises a porous material. A porous material advantageously ensures that no large accumulations of water form. The pores can also be used to stir up the gas flow better, in order to better carry out the product water.

Moreover, in the context of the invention in a gas distributor structure, it is conceivable that the second distributor structure is formed from a metal foam, a metal mesh or a metal mesh. A metal foam can be produced, for example, by foaming a molten metal with the aid of a propellant or by coating a placeholder structure with a metal layer with a subsequent burn-out of the placeholder structure. Such second distribution structure can have a high porosity (in particular with open / permeable pores) of up to 95%. With a metal mesh or a metal mesh, certain ordered channels for the gas flow can be formed, and thus the pressure loss in the gas flow of the reactant through the gas distribution structure can be reduced.

In the context of the invention, it is also conceivable that the second distribution structure is formed periodically or stochastically. Due to the periodic second distribution structure, the pressure loss can be reduced. Due to the stochastic second distribution structure, a high porosity and better turbulence in the gas flow can be set for improved water removal.

It is likewise possible within the scope of the invention for a third region, viewed in the gas flow direction of the reactant, to follow a first, in particular channel-shaped, distributor structure for discharging the reactant from the fuel cell to the second region. In other words, the second porous manifold structure may be disposed at the beginning and at the end between a first manifold structure. In turn, channels can be formed through the third region, through which now the condensed product water can be more easily removed from the gas distributor structure. In addition, a channel-shaped third region can bring about a simplification in the connections in the fuel cell. This third region can not only extend above the active catalyst layer, but also be present in the edge regions and / or in the inlet regions (also called subgasket).

Furthermore, in the case of a gas distributor structure, the invention can provide for the first region to occupy 40% to 80%, in particular 50% to 60%, preferably 50%, of the total length of the gas distributor structure as viewed in the gas flow direction of the reactant. Thus, the costs in the system can increase an advantageous manner can be reduced. In addition, it is conceivable that seen in the gas flow direction of the reactant, the second region occupies 20% to 60%, in particular 40% to 50%, preferably 50% of the total length of the gas distributor structure. Thus, an improved water discharge can be ensured.

In addition, the invention provides a fuel cell, in particular a fuel cell stack, which has a gas distributor structure on a cathode side, which can be designed as described above. By means of the fuel cell according to the invention, the same advantages can be achieved, which have been described above in connection with the gas distributor structure according to the invention. In the present case, full reference is made to these advantages.

list of figures

• 1a eine beispielhafte Brennstoffzelle nach dem Stand der Technik,
• 1b eine Wiederholungseinheit bzw. ein Stack mit mehreren Brennstoffzellen gemäß der 1a,
• 2 eine schematische Darstellung einer erfindungsgemäßen Gasverteilerstruktur mit einer ersten kanalförmigen Verteilerstruktur und einer zweiten porösen Verteilerstruktur,
• 3 eine Seitenansicht auf eine erfindungsgemäße Gasverteilerstruktur, und
• 4 eine schematische Darstellung einer erfindungsgemäßen Gasverteilerstruktur in einem weiteren Ausführungsbeispiel.

The gas distributor structure according to the invention and the fuel cell according to the invention and their developments and their advantages are explained in more detail below with reference to drawings. Each show schematically:

• 1a an exemplary fuel cell according to the prior art,
• 1b a repeating unit or a stack with a plurality of fuel cells according to the 1a .
• 2 FIG. 2 a schematic representation of a gas distributor structure according to the invention with a first channel-shaped distributor structure and a second porous distributor structure, FIG.
• 3 a side view of a gas distributor structure according to the invention, and
• 4 a schematic representation of a gas distributor structure according to the invention in a further embodiment.

In the different figures, identical parts of the invention are always provided with the same reference numerals, which is why they are usually described only once.

The 1a shows a classic example of a known fuel cell 100 *, which has a membrane electrode unit MEA, which is a membrane 103 includes. The membrane 103 is on a cathode side K with a catalyst layer E1 and on an anode side A with a catalyst layer E2 executed. Furthermore, the membrane 103 between two gas diffusion layers GDL be embedded in a porous carbon paper. Either the membrane 103 or the gas diffusion layers GDL are each with a catalyst layer E1 . E2 coated on which the active zone of the membrane 103 to trigger the electrochemical reaction. On the cathode side K becomes increasingly a porous distribution structure S2 , For example, from a wire mesh, metal mesh or metal foam, used as a gas distribution structure 10 * to avoid water retention. On the anode side A will continue a channel-shaped distribution structure S1 , For example, from an embossed sheet used. However, porous manifold structures are costly components that also cause a relatively large pressure drop upon introduction of the reactant.

The assembly of several known fuel cells 100 * into a stack is in the 1b shown. Such assembly, however, is quite costly. The gas supply and gas removal takes place perpendicular to the plane of 1b ,

The invention will be explained below with reference to FIGS. 2 to 4.

The 2 shows a planar position as a bipolar plate 101 , in the sense of the invention in a cathode area K a fuel cell 100 can be used. The 2 shows a plan view of the bipolar plate 101 on which a gas distributor structure according to the invention 10 is arranged.

The gas distributor structure 10 in the sense of the invention has on the air side or cathode side K in gas flow direction x seen in the front or first area 11 a first, in particular channel-shaped, distribution structure S1 on. This first or channel-shaped distributor structure S1 can be made from a low-cost stamped sheet metal and overall to a cost reduction in manufacturing the gas distribution structure 10 to lead.

In the rear or second area 12 has the gas distribution structure 10 in contrast, a second, in particular porous, distribution structure S2 on, which conform to the first distribution structure S1 joins, like the 3 illustrated. The second or porous, in particular open-porous, distribution structure S2 ensures efficient discharge of the product water.

The invention recognizes that with continuous gas flow through the gas distributor structure 10 At high current density more and more product water is obtained, which can be liquid at low operating conditions (T <100 ° C). The second or porous distributor structure S2 , which is slightly more expensive than the first or channel-shaped distributor structure S1 , is thus used only where an accumulation of liquid product water is expected. With the use of a more expensive, but also filigree second distribution structure S2 The invention ensures that this danger is eradicated exactly where it exists.

The cost of the gas distribution structure 10 are thus optimized in an advantageous manner. In addition, the first or channel-shaped distributor structure provides S1 for a reduced pressure drop when introducing the reactant into the gas distributor structure 10 , Thus, costs associated with designing a compressor to provide the cathode-side reactant in a fuel cell 100 be reduced.

The first distribution structure S1 and the second distribution structure S2 can be electrically applied to the bipolar plate by compression, welding, soldering or sintering 101 be connected. The distribution structures can be arranged one below the other S1 . S2 also be joined.

The second distribution structure S2 For the purposes of the invention may be both periodically, for example. As a metal fabric, or stochastic, for example. As a metal foam, be formed.

The 3 shows the gas distributor structure according to the invention 10 in a side view. It can be seen that at an inlet K1 in the gas distributor structure according to the invention 10 the first or channel-shaped distributor structure S1 located. At the outlet K2 from the gas distributor structure according to the invention 10 is the second or porous distribution structure S2 , The gas distributor structure 10 is between a bipolar plate 101 in the form of a flat plate and a membrane electrode assembly MEA arranged.

Furthermore, it is conceivable within the scope of the invention for a third region to be seen in the gas flow direction x of the reactant 13 with a first, in particular channel-shaped, distribution structure S1 for discharging the reactant from the gas distributor structure 10 to the second area 12 can connect. Using the third area 13 can at the outlet K2 from the gas distributor structure 10 a simple removal of the product water and the product gas done. The 4 shows a view from above of such a gas distributor structure 10 attached to a flat bipolar plate 101 is appropriate. Through the end sections of the bipolar plate 101 can continue the respective inlets E1 (H2), E1 (H2O) and outlets E2 (H2), E2 (H2O) for cooling water H2O and hydrogen H2 perpendicular to the plane of 5 run.

In principle, it is conceivable within the scope of the invention for the first region to be seen in the gas flow direction x of the reactant 11 40% to 80%, in particular 50% to 60%, preferably 50% of the total length of the gas distributor structure 10 to reduce costs in the system. Moreover, it is conceivable within the scope of the invention for the second region to be seen in the gas flow direction x of the reactant 12 20% to 60%, in particular 40% to 50%, preferably 50% of the total length of the gas distributor structure 10 can take to improved water discharge from the fuel cell 100 sure.

Preferably, the gas distributor structure according to the invention 10 on the cathode side K a fuel cell 100 be used. Nevertheless, it is also conceivable that the gas distributor structure according to the invention 10 also on the anode side A a fuel cell 100 can be used to favor the gas flow there as well. The fuel cell 100 is not shown in detail. The fuel cell 100 can except for the gas distributor structure according to the invention 10 that instead of the known gas distributor structure 10 * is used, similar to the fuel cell 100 * according to the 1a and 1b being constructed.

The above description of 2 to 4 describes the present invention solely in the context of examples. Of course, individual features of the embodiments, insofar as it is technically feasible, can be freely combined with one another without departing from the scope of the invention.

Claims (10)

A gas distributor structure (10) for a fuel cell (100) for providing a reactant to the fuel cell (100) and which is arrangeable between a bipolar plate (101) and a membrane electrode assembly (MEA), comprising: a first region (11) having a first, in particular channel-shaped, distributor structure (S1) for providing the reactant into the fuel cell (100), and a second region (12) having a second, in particular porous, distributor structure (S2) for passing the reactant in the fuel cell (100), wherein, viewed in the gas flow direction (x) of the reactant, the second region (12) adjoins the first region (11). Gas distributor structure (10) according to Claim 1 , characterized in that the first region (11) comprises an embossed sheet, through which the first distribution structure (S1) is formed. Gas distributor structure (10) according to one of the preceding claims, characterized in that the first distributor structure (S1) made of titanium, copper, aluminum or stainless steel is formed. Gas distributor structure (10) according to one of the preceding claims, characterized in that the first distributor structure (S1) is formed periodically. Gas distributor structure (10) according to one of the preceding claims, characterized in that the second region (12) comprises a porous material. Gas distributor structure (10) according to one of the preceding claims, characterized in that the second distributor structure (S2) is formed from a metal foam, a metal mesh or a metal mesh. Gas distributor structure (10) according to one of the preceding claims, characterized in that the second distributor structure (S2) is formed periodically or stochastically. Gas distributor structure (10) according to one of the preceding claims, characterized in that viewed in the gas flow direction (x) of the reactant, a third region (13) with a first, in particular channel-shaped, distributor structure (S1) for discharging the reactant from the fuel cell (100 ) connects to the second region (12). Gas distributor structure (10) according to any one of the preceding claims, characterized in that in the gas flow direction (x) of the reactant, the first region (11) 40% to 80%, in particular 50% to 60%, preferably 50% of the total length of the gas distributor structure ( 10), and / or that seen in the gas flow direction (x) of the reactant, the second region (12) occupies 20% to 60%, in particular 40% to 50%, preferably 50% of the total length of the gas distributor structure (10). A fuel cell (100) having on a cathode side (K) a gas distributor structure (10) according to one of the preceding claims.

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