Device and Method for Extending the Service Life of HT-PEM Fuel Cells

Abstract

According to the invention, a device is provided for extending the service life of a high-temperature polymer electrolyte membrane fuel cell. This device includes an HT-PEM fuel cell with at least one cell. The cell is constructed according to the following sequence: a supply plate with an anode channel structure, an anode gas diffusion electrode, an electrolyte-containing polymer membrane, a cathode gas diffusion electrode, and a supply plate with a cathode channel structure. In addition, at least one acid-filled acid reservoir is provided, which is connected to a distributor channel extending in the supply plates approximately perpendicular to the channel structures, the distributor channel being connected to at least one of the gas diffusion electrodes and/or the polymer membrane of at least one of the cells of the fuel cell stack in such a way that acid can be supplied to at least one of the gas diffusion electrodes and/or the polymer membrane of at least one of the cells of the fuel cell stack.

Claims

1. A device for extending the service life of an HT-PEM fuel cell with an HT-PEM fuel cell stack, where one cell of the stack is constructed according to the following sequence: a supply plate with an anode channel structure, an anode gas diffusion electrode, an electrolyte-containing polymer membrane, a cathode gas diffusion electrode, a supply plate with a cathode channel structure, wherein at least one acid-filled acid reservoir is provided, which is connected to a distributor channel extending in the supply plates approximately perpendicular to the channel structures, the distributor channel being connected to at least one of the gas diffusion electrodes and/or the polymer membrane of at least one of the cells of the fuel cell stack in such a way that acid can be supplied to at least one of the gas diffusion electrodes and/or the polymer membrane of at least one of the cells of the fuel cell stack.

2-16. (canceled)

17. The device according to claim 1, wherein the acid reservoir contains phosphoric acid, sulfuric acid, or another electrolyte or electrolyte-containing mixture.

18. The device according to claim 17, wherein the distributor channel is connected to at least one of the gas diffusion electrodes and/or the polymer membrane of at least one of the cells of the fuel cell stack via a connecting means such as capillaries, a supply channel, a supply element, a transport aid, a reservoir, or a channel-like structure.

19. The device according to claim 18, wherein branching off from the distributor channel is a connecting channel, which is embodied in the plane of the channel structure and is connected to a supply channel lying in the same plane, which supply channel is embodied as an acid supply reservoir, and acid can be supplied to the fuel cell via these channels.

20. The device according to claim 1, wherein the distributor channel is connected to at least one of the gas diffusion electrodes and/or the polymer membrane of at least one of the cells of the fuel cell stack via a connecting means such as capillaries, a supply channel, a supply element, a transport aid, a reservoir, or a channel-like structure.

21. The device according to claim 1, wherein branching off from the distributor channel is a connecting channel, which is embodied in the plane of the channel structure and is connected to a supply channel lying in the same plane, which supply channel is embodied as an acid supply reservoir, and acid can be supplied to the fuel cell via these channels.

22. The device according to claim 21, wherein a reservoir is integrated into the connecting channel and/or the supply channel.

23. The device according to claim 22, wherein the distributor channel is composed of distributor channel sections of each cell and the distributor channel is connected to the acid reservoir.

24. The device according to claim 23, wherein a supply device is provided for supplying acid from an external storage tank, which constitutes the acid reservoir, into the distributor channel.

25. The device according to claim 24, wherein in the fuel cell stack, distributor channel sections for supplying and draining acid are embodied in such a way that it is possible to circulate acid through the fuel cell by means of a circulating device.

26. The device according to claim 25, wherein the supply device and/or the circulating device can be triggered by a control unit in such a way that a controlled supply of acid into the cells of the fuel cell stack takes place.

27. The device according to claim 26, wherein the supply element is connected to the acid reservoir and the electrolyte-containing polymer membrane and/or the gas diffusion electrode in such a way that acid from the acid reservoir can be supplied to the polymer membrane and/or the gas diffusion electrode, the supply element being situated between the polymer membrane and gas diffusion electrode or also in a region adjacent to the two.

28. The device according to claim 27, wherein the supply element is situated in the acid supply reservoir and/or in the supply channel.

29. The device according to claim 1 wherein the distributor channel is composed of distributor channel sections of each cell and the distributor channel is connected to the acid reservoir.

30. The device according to claim 1, wherein a supply device is provided for supplying acid from an external storage tank, which constitutes the acid reservoir, into the distributor channel.

31. The device according to claim 1, wherein in the fuel cell stack, distributor channel sections for supplying and draining acid are embodied in such a way that it is possible to circulate acid through the fuel cell by means of a circulating device.

32. The device according to claim 1, wherein the supply device and/or the circulating device can be triggered by a control unit in such a way that a controlled supply of acid into the cells of the fuel cell stack takes place.

33. The device according to claim 1, wherein the supply element is connected to the acid reservoir and the electrolyte-containing polymer membrane and/or the gas diffusion electrode in such a way that acid from the acid reservoir can be supplied to the polymer membrane and/or the gas diffusion electrode, the supply element being situated between the polymer membrane and gas diffusion electrode or also in a region adjacent to the two.

34. The device according to claim 33, wherein the supply element is embodied in the form of a wick or a net or of fibers, as capillaries between polymer film(s) and/or the membrane, or as an absorbent body, e.g. with a high diffusion resistance and a suitable porosity so that the acid can be released from the body slowly.

35. The device according to claim 1, wherein the supply element is situated in the acid supply reservoir and/or in the supply channel.

36. The device according to claim 1, wherein the distributor channel section is embodied as an independently delimited space in the supply plate and defines an acid reservoir.

37. A method for extending the service life of high-temperature polymer electrolyte membrane fuel cells, in which acid is supplied from an acid-filled acid reservoir, via a distributor channel extending approximately perpendicular to the channel structures of a supply plate, to one of the gas diffusion electrodes and/or a polymer membrane of at least one cell of a fuel cell stack.

38. The method according to claim 1, wherein the supply is carried out in such a way that the acid travels into the electrode layer of a gas diffusion electrode and from there into the polymer matrix of the polymer membrane, the acid is distributed in planar fashion across the electrode layer and/or the membrane and/or its boundary layer, and a part of it is released to the opposite GDE.

39. The method according to claim 35, wherein the supply is carried out in such a way that the acid travels into the electrode layer of a gas diffusion electrode and from there into the polymer matrix of the polymer membrane, the acid is distributed in planar fashion across the electrode layer and/or the membrane and/or its boundary layer, and a part of it is released to the opposite GDE.

40. The method according to claim 1, wherein the supply takes place by means of gravity in such a way that the acid is supplied slowly, with the entry of acid into the feed channels being hindered by the fact that the reservoir is situated beneath or at the same height as the supply channel and thus the force acting on the acid is lower and the flow of acid is slower.

41. The method according to claim 36, wherein the supply takes place by means of gravity in such a way that the acid is supplied slowly, with the entry of acid into the feed channels being hindered by the fact that the reservoir is situated beneath or at the same height as the supply channel and thus the force acting on the acid is lower and the flow of acid is slower.

Description

[0106] The invention will be explained in greater detail below based on the drawings. In the drawings:

[0107] FIG. 1 is a schematic depiction of a device according to the invention, having a fuel cell stack with an acid reservoir, a storage tank, a line section, and supply device,

[0108] FIG. 2 is a schematically depicted top view of a supply plate with an acid reservoir of a device according to the invention,

[0109] FIG. 3 is a schematically depicted top view of another embodiment of a supply plate with an acid reservoir of a device according to the invention,

[0110] FIG. 4 is a schematically depicted top view of another embodiment of a supply plate with an acid reservoir of a device according to the invention,

[0111] FIG. 5 is a schematically depicted top view of another embodiment of a supply plate with a gas diffusion electrode, a polymer film, a sealing frame, and an acid reservoir of a device according to the invention,

[0112] FIG. 6 shows the embodiment from FIG. 5 in a view cut laterally along the line A-A,

[0113] FIG. 7 is a schematically depicted top view of another embodiment of the embodiment shown in FIG. 5,

[0114] FIG. 8 is a schematically depicted top view of another embodiment of a supply plate with a polymer membrane, a gas diffusion electrode, a sealing frame, and an acid reservoir of a device according to the invention,

[0115] FIG. 9 is a schematically depicted top view of another embodiment of a supply plate of a device according to the invention,

[0116] FIG. 10 is a schematically depicted top view of an alternative embodiment of a supply plate with an acid reservoir,

[0117] FIG. 11 is a schematically depicted top view of an alternative embodiment of a supply plate with an acid reservoir,

[0118] FIG. 12 is a schematic, laterally sectioned detail view of a cell of a fuel cell stack according to another embodiment,

[0119] FIG. 13 is a schematic, laterally sectioned detail view of a cell of a fuel cell stack according to another embodiment, and

[0120] FIG. 14 is a schematic, laterally sectioned detail view of a cell of a fuel cell stack according to another embodiment.

[0121] A device 1 according to the invention for extending the service life of an HT-PEM fuel cell includes a HT-PEM fuel cell and an acid reservoir. The fuel cell 8 is preferably a fuel cell stack composed of a plurality of cells (FIG. 1).

[0122] The individual cells of the fuel cell stack 8 include a supply plate 2 with an anode channel structure 3, an anode gas diffusion electrode 17, an electrolyte-containing polymer membrane 13, a cathode gas diffusion electrode 17, and a supply plate 2 with a cathode channel structure 3.

[0123] The supply plates 2 are embodied in accordance with the supply plates 2 according to the invention described below.

[0124] In the fuel cell stack, distributor channel sections 4 of the supply plates 2 form a distributor channel 9 that is composed of the individual distributor channel sections 4 and is fluid-tight and gas-tight in relation to the outside (FIGS. 2 through 4).

[0125] The distributor channel 9 is connected to a storage tank 11 via a line section 10.

[0126] A supply device 12 such as a pump is integrated into the line section 10 and is embodied to pump acid from the storage tank 11 into the distributor channel 9.

[0127] The line section 10, the supply device 12, and the storage tank constitute a supply system 18.

[0128] A control unit (not shown) is provided to control the supply or metering of acid into the fuel cell stack.

[0129] A first embodiment of a supply plate 2 according to the invention is described below, which has a channel structure 3 and an acid supply reservoir 16 (FIG. 2).

[0130] The channel structure 3 can be an anode channel structure or a cathode channel structure.

[0131] The supply plate is embodied in a plate shape with two surface sides and four end faces and is composed of an electrically conductive material such as graphite or a graphite-containing material.

[0132] It can also be composed of a suitable metallic material. Furthermore, the channel structure 3 can be embodied on only one surface side or on both sides of the supply plate.

[0133] The channel structure 3 is open toward a surface side and for example extends in a meandering form.

[0134] In at least one corner of the supply plate 2, a distributor channel section 4 is provided, which is embodied in the form of a through bore.

[0135] The distributor channel section 4 is situated perpendicular to the plane in which the channel structure 3 is embodied.

[0136] The distributor channel section 4 is connected to a reservoir 7 for accommodating acid via a connecting channel 5, which extends in the same plane as the channel structure 3 and is likewise embodied as open toward a surface side.

[0137] For example, the reservoir 7 is a hemispherical or rectangular opening or a broader and/or expanded channel that is open toward the surface side.

[0138] Branching off from the reservoir 7 there is a supply channel 6, which extends approximately into the middle of the region of the channel structure 3 and is likewise embodied as open toward a surface side.

[0139] According to this embodiment, the supply channel 6 is the acid supply reservoir 16 via which a replenishing flow of acid is fed into a cell of a fuel cell stack 8. The replenishing occurs because the acid in the supply channel is in direct contact with the gas diffusion substrate.

[0140] A second embodiment of a supply plate 2 according to the invention, which has a channel structure 3 and an acid supply reservoir 16, is described below (FIG. 3). Provided that nothing to the contrary is described here, this supply plate has the same features as the above-described supply plate according to the first embodiment.

[0141] According to the second embodiment, the reservoir 7 is situated to the side of the supply plate and is likewise connected to the connecting channel 5.

[0142] The supply channel 6, which once again constitutes the acid supply reservoir 16, branches off at approximately half the length of the connecting channel 5 in the region of the channel structure 3 and extends into the latter.

[0143] A third embodiment of a supply plate 2 according to the invention will be described below, which has a channel structure 3 and an acid supply reservoir 16 (FIG. 4). Provided that nothing to the contrary is described here, this supply plate has the same features as the supply plate 2 according to the second embodiment.

[0144] Fuel cell stacks built into a system always have a support side A, which is oriented toward the surface of the earth. According to this embodiment, the support side is the lower end face shown in FIG. 4, i.e. the support side extends orthogonal to the plane in which the supply plates lie.

[0145] In the context of the present invention, it is also possible for the support side to extend parallel to the plane in which the supply plates lie.

[0146] The dashed line in FIG. 4 indicates the support region of a gas diffusion electrode 17.

[0147] The connecting channel 5 has two sections. The supply channel 6 or acid supply reservoir 16 extends between these two sections.

[0148] By contrast with the two above-described exemplary embodiments of the supply plate, the sections of the connecting channel 5 extend into the region in which the gas diffusion substrate 17 is supported.

[0149] Such an arrangement of the supply channel 6 prevents acid from traveling into the channel structure 3 of the supply plate 2 due to the force of gravity.

[0150] A fourth embodiment of a supply plate 2 will be described below, which has a gas diffusion electrode 17, a polymer film (subgasket) 19, a sealing frame 20, and an acid supply reservoir 16 (FIG. 5 and FIG. 6). Provided that nothing to the contrary is described here, this supply plate has the same features as the supply plates described above.

[0151] According to this embodiment, the polymer membrane 13 does not end approximately flush with the edge region of the gas diffusion electrode 17, but instead has an edge section 21 that protrudes from the circumference of the region of the gas diffusion electrode 17.

[0152] At the top and bottom, this edge section 21 of the polymer membrane 13 is covered by the frame-shaped reinforcing frame 19 (polymer film). The polymer film 19 has a thickness of approximately 25 m.

[0153] A sealing frame 20 is respectively provided against the polymer film 19 and the supply plate 2.

[0154] The supply plate 2 has a distributor channel section 4, which is connected to the acid supply reservoir 16 via a connecting channel 5.

[0155] The connecting channel 5 is embodied as an opening in the sealing frame 20.

[0156] The acid supply reservoir 16 is delimited at the top by the supply plate 2, at the side by the sealing frame 20, and at the bottom by the reinforcing frame 19which is provided with openings 22and the edge section 21 of the polymer membrane 13.

[0157] The openings 22 of the reinforcing frame 19 permit acid to pass through from the acid supply reservoir 16 into the edge section 21 of the polymer membrane 13. In this way, acid can travel from the acid supply reservoir 16 into the polymer membrane 13 and from there into the gas diffusion electrode 17.

[0158] The fact that several, for example four, small openings 22 are provided prevents a swelling of the membrane over a large area, which can lead to cracks and detachment.

[0159] An acid supply reservoir of this kind is preferably situated parallel to the support surface of the fuel cell stack in order to prevent the acid from draining into the channel structure of the supply plate.

[0160] The acid can thus travel on the one hand into the polymer membrane and on the other hand, also into a boundary layer that is formed between the polymer film 19 or subgasket and the polymer membrane, this flow being produced by capillary forces.

[0161] In addition, the polymer film serves to reinforce the membrane in the edge region.

[0162] A fifth embodiment of a supply plate 2 according to the invention is described below (FIG. 7). Provided that nothing to the contrary is described here, this has the same features as the embodiment shown in FIG. 5.

[0163] According to this embodiment, the sealing frame 20 has a partition 23 that also delimits the acid reservoir 16. This partition 23which extends approximately parallel to a support surface, from one side of the sealing frame 20 to a side opposite from this sideshould, by means of the pressure emanating from the sealing frame, prevent a swelling of the membrane and an unwanted flow of acid into the feed channels.

[0164] Also according to this embodiment, a reservoir 7 is provided; the dashed lines indicate corresponding openings in a supply plate (not shown) that rests on top of the sealing frame. The reservoir 7 is integrated into the connecting channel 5.

[0165] Another embodiment of a supply plate 2 is described below (FIG. 8), which, provided that nothing to the contrary is described here, has the same features as the supply plates 2 described above.

[0166] According to this embodiment, a distributor channel section 4 is embodied in the supply plate 2.

[0167] The sealing frame 20 has an opening embodied in the form of a connecting channel 5. According to this embodiment, the opening 22, the connecting channel 5, or the supply channel 6 constitutes the acid supply reservoir 16 since the opening is delimited by the polymer film 19 and consequently, acid contained in the acid supply reservoir 16 is in direct contact with the edge section 21 of the polymer film 19 and thus the polymer membrane 13. Furthermore, the acid is additionally or alternatively directly in contact with the gas diffusion electrode 17.

[0168] Another embodiment of a supply plate is described below (FIG. 9). Provided that nothing to the contrary is described here, this supply plate has the same features as the supply plates described above.

[0169] In the supply plate 2, a distributor channel section 4 is provided, which feeds via a connecting channel 5 into a reservoir 7 likewise embodied as a cavity in the supply plate. A supply channel 6 constitutes an opening from the reservoir 7 or a passage from the reservoir 7 to the gas diffusion electrode 17 and to the polymer membrane 13.

[0170] The region of the supply channel 6 situated in the edge section 21 of the polymer film 19 constitutes the acid supply reservoir 16.

[0171] A glass fiber wick 24 extends from the gas diffusion electrode 17 through the section of the connecting channel 5 into the reservoir 7, which according to this embodiment, is a component of the acid supply reservoir 16.

[0172] Acid that has been brought into the reservoir 7 can thus be drawn by capillary forces through the wick 24, which is for example a glass fiber wick, into the electrode layer of the gas diffusion electrode and/or into the membrane.

[0173] According to an alternative embodiment of a supply plate 2 (FIG. 10) that is described below, the supply plate 2 has two distributor channel sections 4.

[0174] These distributor channel sections 4 are each connected to a supply channel 6 via a respective connecting channel 5.

[0175] According to this embodiment, a circulating device (not shown) such as a pump is provided; one distributor channel section 4 is embodied as a supply distributor channel so that acid travels into the supply distributor channel by means of the circulating device and the other distributor channel section 4 is correspondingly embodied as a draining distributor channel via which the acid is drained.

[0176] According to this embodiment, the acid is not only supplied and replenished but also circulates in the fuel cell stack via distributor channels 9, which are embodied by the distributor channel sections 4.

[0177] The acid in the supply channel 6 that constitutes the acid supply reservoir once again directly contacts the gas diffusion electrode 17 and/or the polymer membrane 13.

[0178] Other embodiments of the present invention with subgaskets 19 are described below, which, provided that nothing to the contrary is described here, correspond to the embodiments with subgaskets 19 described above (FIGS. 12 through 14).

[0179] According to one of these embodiments, the acid is supplied to the cells via the distributor channel sections 4 and/or the distributor channel 9.

[0180] According to one embodiment, a subgasket 19 (polymer film; reinforcing frame) extends into the distributor channel 4 respectively above and below the polymer membrane 13.

[0181] In the region of the distributor channel 9, a corresponding opening 25, i.e. a hole, is provided in the subgaskets 19, in order not to hinder the flow of acid through the distributor channel 9.

[0182] In the boundary layers in which the subgaskets 19 contact each other, capillaries 26 are provided via which the acid travels into the reactive region of the gas diffusion electrodes 17 and/or the polymer membrane 13 of a cell.

[0183] These capillaries 26 are a transport aid as defined by the present invention.

[0184] According to another embodiment, the membrane 13 and at least one subgasket 19 can also extend into the distributor channel 9 (FIG. 13).

[0185] In the region of the distributor channel 9, a corresponding opening 25, i.e. a hole, is once again embodied in the subgasket and the membrane.

[0186] In the boundary layers in which the subgasket 19 and membrane 13 contact each other, capillaries 26 are provided via which the acid travels into the reactive region of the gas diffusion electrodes 17 and/or the polymer membrane 13 of a cell.

[0187] According to this embodiment, a subgasket 19 respectively situated above and below the polymer membrane 13and the membrane 13 itselfcan extend into the distributor channel 9. Then corresponding capillaries 26 are provided above and below the membrane 13, between the membrane 13 and subgasket 19.

[0188] In order to facilitate the introduction of the acid, according to another embodiment, a transport aid such as a net, a fleece, a wick, or a similar distributor structure can be provided between the boundary layers, FIG. 14.

[0189] Various embodiments of a method according to the invention for extending the service life of high-temperature polymer electrolyte membrane fuel cells are described below.

[0190] In the following, a distinction is drawn between an active replenishment of acid and a passive replenishment of acid.

[0191] With an active replenishment of acid, the pump 12 pumps acid from the storage tank 11, via the line section 10, into the distributor channel, and from there into the reservoir 7.

[0192] This is carried out until the reservoir 7 is completely filled with acid. Then the acid flows from the reservoir 7 into the supply channel 6. This has the advantage that a uniform phosphoric acid distribution takes place independent of the position of the individual cells since first, the reservoirs 7 with the same respective volume in the supply plates are completely filled and after they have been filled, the largest part of the acid supply into the membrane takes place.

[0193] From the supply channel 6 or the acid supply reservoir, the acid then flows slowly and in particular mainly only in the region in which the gas diffusion substrate contacts the supply channel via the gas diffusion substratealso in a locally restricted fashioninto the gas diffusion electrode and from there into the electrolyte-containing polymer membrane 13 in order to replace the expended electrolyte there (phosphoric acid, sulfuric acid). From the electrolyte-containing polymer membrane 13 and/or the electrode layer, the acid is then distributed in planar fashion across the active surface of the cell and then partially released to the opposite electrode layer.

[0194] All of the reservoirs 7 in the supply plates 2 have the same volume. A special case exists when individual cells have different operating temperatures. Then it is also possible to provide reservoirs with different volumes in order to be able compensate for the different acid consumption. The reservoirs 7 serve to homogenize the supply of acid to each individual cell of the fuel cell stack. In this way, each membrane electrode assembly (MEA), which is composed of the electrolyte-containing polymer membrane and the gas diffusion electrodes with the catalyst applied to the gas diffusion substrate, receives the same quantity of acid.

[0195] With a passive supply of acid, it is possible to eliminate the supply device 12.

[0196] With a supply of this kind, a replenishing flow of acid from the storage tank outside the fuel cell stack is automatically supplied to the fuel cell stack, for example due to a volume increase of the acid due to water absorption from the cell. This makes it possible to provide a continuous supply.

[0197] According to an embodiment of this kind, the reservoir 7 can also serve as a storage tank 11, making it possible to eliminate the storage tank and other external devices entirely.

[0198] According to another embodiment of this kind, it is also possible to eliminate the distributor channel 9 and supply channel 6. The acid then travels directly from the reservoir 7 embodied as a storage tank via the gas diffusion layer or the gas diffusion substrate into the electrode layer and from there, into the electrolyte-containing polymer membrane, in order to replace the electrolyte that has been removed from the fuel cell.

[0199] Consequently, the reservoir 7 is embodied as an independently delimited space in the supply plate 2 and/or in the sealing frame 20 (FIG. 11). With an embodiment in the sealing frame, an acid reservoir of this kind can also be considered to be a closed distributor channel section 5. An embodiment of this kind with an independent reservoir 7 constitutes a separate concept of the invention.

[0200] According to the invention, therefore, the acid can be either actively pumped to the gas diffusion electrode or passively transported by gravity, by volume increase, by adhesion forces or capillary forces, or by volume increase due to water absorption of the acid solution because of its hygroscopic properties. The water absorption from the product water of the fuel cell is accompanied by a volume increase, which promotes an introduction by the force of pressure.

[0201] According to the invention, the acid from an acid reservoiror from a chamber that is embodied in the supply plate and filled with acidtravels through the hydrophobic gas diffusion substrate and through the gas diffusion layer, into the electrode layer and from there, travels into the electrolyte membrane due to the high acid affinity or hydrophilicity of the membrane.

[0202] The affinity of the electrolyte is based not only on its absorptive capacity and the water that it contains, but also on the basic groups of the electrolyte, which absorb hydrogen ions, for example, and attract the acid anion by means of the resulting positive charge. Consequently the channel empties and can be refilled again continuously or discontinuously.

[0203] In order to reduce the viscosity or the surface tension of the acid or to embody the surface of the gas diffusion electrode to be more absorptive, additives such as alcohols can be provided or diluted acid can be used. This facilitates a penetration of acid into the porous structure of the gas diffusion electrode. Since the contact of concentrated acid with the PBI membrane can cause a swelling of the polymer membrane to occur due to locally excessive acid absorption in the polymer matrix and this can lead to irregular current density distribution in the operation of the fuel cell and to membrane damage, the acid can be diluted with a high-boiling solvent (e.g. ethylene glycol).

[0204] According to another embodiment, the acid can also be supplied directly to the polymer membrane. In this case, the acid travels from a reservoir and into the membrane via a supply element such as an edge section 21 that is embodied on the membrane or integrally formed onto it, a membrane strip, a tab, or a separate component such as a membrane section or wick. A variety of designs are possible for contacting the acid with the membrane. They will be explained briefly below.

[0205] In order to enable a better or faster distribution of acid directly onto the membrane, a wick, a net arranged in planar fashion, or fibers with a suitable orientation can be positioned between the electrode and membrane as a transport aid for the acid. The fibers are made in such a way that they conduct acid and if possible, absorb enough acid that they do not hinder the proton conduction of the combination of electrolyte membrane and transport aid. These transport aids can also be embodied so that they contact the acid reservoir or the reservoir.

[0206] A supply to the region of the polymer membrane can also be provided, said supply being embodied, for example, in a supply plate and the acid traveling directly to the membrane via holes in the gas diffusion electrode.

[0207] The supply of acid to the region of the polymer membrane can also take place by means of polymer films (subgaskets), which are situated at the edge of the cell surface and contact the membrane or rest on it, via the cavity situated between two or more polymer films or between a polymer film and the membrane, taking advantage of capillary forces.

[0208] In order to avoid an outflow of acid, for example from a supply channel through the gas diffusion layer into adjacent feed channels, a complete or partial sealing or compression of parts of the gas diffusion layer can be provided. The gas diffusion layer can, for example, be sealed by bonding cavities with a cross-linking polymer or by filling them with PTFE particles. A partition in the supply plate or a polymer seal allows additional pressure to be selectively applied to the gas diffusion layer, which compresses the gas diffusion layer and reduces the porosity in this region.

[0209] A positioning of the supply channel in the lower regions of the supply plate is advantageous for avoiding the outflow of acid from the supply channel into underlying feed channels due to the force of gravity.

[0210] The outflow of acid for example from the supply channel into adjacent feed channels, however, can also be used for a more extensive distribution of acid over the electrode surface. In this case, among other things, acid passes from the feed channels into the gas diffusion electrode or the polymer membrane.

[0211] A supply of phosphoric acid can take place both as the fuel cell is being fed with reactands and without a feeding, both with a current flow and without a current flow, as well as both with and without tempering.

[0212] Instead of phosphoric acid, it is also possible to use a different electrolyte such as sulfuric acid or an electrolyte-containing mixture (e.g. phosphoric acid with ethylene glycol and ionic liquids) and for a polymer membrane, it is possible to use a suitable HT-PEM membrane such as cross-linked AB-PBI, para-PBI, or an aromatic polyether. The electrolyte can also contain additives (e.g. salts, tensides, PBI).

REFERENCE NUMERAL LIST

[0213] 1 device [0214] 2 supply plate [0215] 3 channel structure [0216] 4 distributor channel section [0217] 5 connecting channel [0218] 6 supply channel [0219] 7 reservoir [0220] 8 fuel cell/fuel cell stack [0221] 9 distributor channel [0222] 10 line section [0223] 11 storage tank [0224] 12 supply device [0225] 13 electrolyte-containing polymer membrane [0226] 14 tab [0227] 15 end section [0228] 16 acid reservoir [0229] 17 gas diffusion electrode [0230] 18 supply system [0231] 19 polymer film [0232] 20 sealing frame [0233] 21 edge section [0234] 22 openings [0235] 23 partition [0236] 24 wick [0237] 25 opening [0238] 26 capillary