DE102010008304A1 - Method and device for loading a current collector of a fuel cell with catalyst material - Google Patents

Abstract

The invention relates to a method for loading a current collector of a fuel cell with catalyst material, wherein a substantially planar current collector is provided, a catalyst material extruded through at least one nozzle and along at least one path on a surface of the current collector so applied that along the at least one first web Sections containing catalyst material in a first concentration and second sections containing catalyst material in a second concentration, which is lower than the first concentration, alternately follow each other. The invention also relates to a device for loading a current collector of a fuel cell with catalyst material, having an applicator (28) for applying catalyst material (25) to the current collector in the form of at least one track on a surface of the current collector, wherein the applicator has at least one nozzle ( 26) for extruding a first medium (25) containing catalyst material and means for forming successive first and second portions (39, 40, 49, 50) of the at least one web, said first portions (39, 49) comprising catalyst material in a first Concentration, and the second portions (40, 50) contain catalyst material in a second concentration, which is lower than the first concentration, and conveying means (33) which are suitable to transport at least the first medium to the nozzle of the applicator for.

Description

The invention relates to a method and a device for loading a current collector of a fuel cell with catalyst material. The invention also relates to such a loaded current collector and a fuel cell stack equipped with such current collectors.

To generate electrical energy by means of fuel cells, a larger number of fuel cells is usually arranged in the form of a stack, the fuel cells each having an anode, a cathode and an electrolyte arranged between the anode and the cathode. The individual fuel cells of the stack are separated from each other by bipolar plates and electrically contacted. At the anodes and the cathodes each Storm collectors are provided which serve to electrically contact the anodes or cathodes on the one hand and on the other hand pass reaction gases to these. In the edge region of the anode, cathode and electrolyte matrix each sealing elements are provided which form a lateral seal of the fuel cell and thus the fuel cell stack against leakage of anode and cathode gas.

In a molten carbonate fuel cell, the electrolyte material typically consists of binary or ternary alkali carbonate melts (for example mixed melts of lithium and potassium carbonate) fixed in a porous matrix. In operation, molten carbonate fuel cells typically reach working temperatures of about 650 ° C. In this case, on the anode side, a reaction of hydrogen with carbonate ions to water and carbon dioxide takes place with electron release. On the cathode side, oxygen reacts with carbon dioxide to form carbonate ions with electron uptake. This heat is released. On the one hand, the alkali carbonate melt used as the electrolyte supplies the carbonate ions required for the anode half reaction and, on the other hand, absorbs the carbonate ions formed in the cathode half reaction. In practice, the anode side of the fuel cell is usually a hydrocarbon-containing energy source, such as methane, which can be derived for example from natural gas or biogas, and fed water from which is obtained by so-called internal reforming the hydrogen required for the anode half reaction. The anode exhaust gas is mixed with additionally supplied air and then catalytically oxidized to remove any residual components of the fuel gas. The resulting gas mixture now contains carbon dioxide and oxygen, that is, exactly the gases required for the cathode half-reaction, so that anode exhaust gas can be introduced directly into the cathode half-cell after fresh air supply and catalytic oxidation.

The hot exhaust air leaving the cathode outlet is free of pollutants and can be reused thermally. The electrical efficiency of the molten carbonate fuel cell is already 45 to 50% and using the heat released in the overall process, an overall efficiency of about 90% can be achieved.

The internal reforming to recover the hydrogen needed for the anode half reaction from a hydrocarbonaceous energy source can be carried out in the fuel cell stack in essentially two ways. In the so-called indirect internal reforming (IIR) several separate chambers, in which a reforming catalyst material is located within the fuel cell stack. The hydrocarbonaceous energy source to be reformed is first passed through these chambers. The hydrogen-gas-containing reformed energy carrier is then passed into the anode half-cells of the fuel cell stack. In the so-called direct internal reforming (DIR), the reformed catalyst is located inside the anode chambers of the fuel cell, so that the hydrogen gas released during the reforming is produced directly at the anode.

The anode half cell is bounded on the one hand by the anode and on the other hand by an electrically conductive bipolar plate which separates the anode chamber from the cathode chamber of the cell adjacent to the fuel cell stack. In the anode chamber there is also an anode current collector, which on the one hand must ensure an electrical connection between the anode and the bipolar plate and, on the other hand, a flow path for the fuel gas flowing through the anode half cell. In a fuel cell with direct internal reforming, the current collector must also accommodate the reforming catalyst material and provide for an effective contacting of the fuel gas with the reformed catalyst material. For direct internal reforming, different approaches have been developed in the prior art. This is how the German patent application describes DE 10358788 A1 Applicant a porous anode current collector which is coated with a porous layer of a catalyst material. Frequently, the anode current collector consists of a corrugated or corrugated sheet, so that a structure is formed which on the one hand electrically contacts the anode or the bipolar plate and on the other defines flow paths for the fuel gas flowing through the anode half-cell. The catalyst material is arranged in the wells of the anode current collector plate defined in this way. For example, the wells of the anode current collector may be coated with catalyst material. In the American patent US 5,468,573 becomes a corrugated Anode current collector having longitudinally extending recesses in which numerous prefabricated, cylindrical catalyst pellets are arranged. The introduction of numerous cylindrical catalyst pellets in large-scale current collectors is very expensive. To simplify the loading of the current collector with catalyst pellets is described in the international patent application WO 2008/141071 A1 proposed the use of a largely automated placement device. Such a system is very costly and prone to failure due to the required precision with which the catalyst pellets must be introduced into the wells. In contrast, the patent proposes US 6,942,943 instead of inserting the rectilinear wells of a current collector, instead of numerous, successively arranged, short cylindrical pellets, a continuous strand of the catalyst material in each elongated recess of the Stromkollektorbleches. According to US Pat. No. 6,942,943, a dough-like, very high-viscosity catalyst mass is used, which is extruded via a high-pressure punch and a nozzle as a defined cylindrical strand. The handling of this catalyst dough is therefore complicated and hampers rapid filling of the current collector with catalyst material. In addition, the concentration of the catalyst material within the strand is constant.

Since the reforming reaction is endothermic, the reforming of the hydrocarbon-containing gas can also be used to dissipate the heat generated during operation of the fuel cell. It has also been proposed to modify the temperature distribution of the fuel cell by an uneven catalyst distribution in the surface. So will in US 4,567,117 describes a sheet coated with catalyst material plate in which the amount of catalyst and / or the catalyst activity increases in the direction of the anode outlet. However, the generation of such an uneven catalyst distribution is complicated when using a catalyst material applied flat on a support.

In addition, in US 7,431,746 described an indirect internal reforming unit, which is divided into several zones with different catalyst loading. However, this document does not describe any way in which such an inhomogeneous catalyst distribution can be prepared simply, cheaply and quickly.

The present invention is therefore based on the technical problem of providing a method for loading a current collector of a fuel cell with catalyst material, which allows a cost-effective production of current collectors with inhomogeneous catalyst distribution. Furthermore, a suitable device for carrying out the method as well as a corresponding current collector or a fuel cell rod equipped with such current collectors should be provided.

This technical problem is solved by the method according to the present patent claim 1, the apparatus for loading a current collector according to claim 12, the current collector according to claim 14 and the fuel cell stack according to claim 15. Advantageous developments of the invention are subject matter of the dependent claims.

The invention accordingly relates to a method for loading a current collector of a fuel cell with catalyst material, wherein a substantially flat current collector is provided, a catalyst material extruded through at least one nozzle and along at least one path on a surface of the current collector so applied that along the at least one path first portions containing catalyst material of a first concentration and second portions containing catalyst material in a second concentration, which is lower than the first concentration, alternately follow one another. By suitable choice of the catalyst concentration in the first or second sections and the length of the first and second sections, the local loading of the current collector can be varied with catalyst material in a wide range. As one applies the sequence of the first and second sections to the current collector, both the length of the individual sections and the catalyst concentrations can vary.

However, according to a particularly preferred and inexpensive variant of the process according to the invention, only two media are provided, namely a first medium which contains catalyst material in a first concentration and a second medium which contains catalyst material in a second concentration and varies the catalyst coverage on the current collector merely by selecting the lengths of the first sections generated with the first medium or the second sections generated with the second medium. Of course, according to the invention, more than two media can be provided for producing more than two different sections, the catalyst concentration differing, at least in one of the media, from the catalyst concentrations of the other media.

The inventively provided extrusion of the catalyst material from a nozzle is a particularly effective and easy automatable method for loading the current collector an inhomogeneous distribution of catalyst material provided.

According to a preferred embodiment of the method according to the invention, at least one first medium containing catalyst material of the first concentration and at least one second medium containing catalyst material of the second concentration are ejected from the nozzle to form the second sections while moving the nozzle and the current collector along the at least one track relative to each other. However, in the present case, the relative movement of nozzle and current collector also includes the possibility that the relative velocity of nozzle and current collector may be 0 while applying the first or the second medium, for example when the first or the second medium is substantially point-like for generating an extremely short first or second section is to be applied.

Further, in the method of the present invention, the second concentration of catalyst material is not limited to the bottom. According to one variant of the invention, the second concentration may also be zero, which means that in this variant of the method according to the invention the second sections do not contain any catalyst material.

The second medium may be a gaseous, a liquid or a pasty fluid. For example, the second medium may also be a catalyst-free inert gas, for example air, or a catalyst-free paste. The fluid may consist of a thermally decomposable or thermally non-decomposable component or a combination thereof.

With the method according to the invention, moreover, the risk of poisoning of the catalyst material can be reduced. For example, if locally transferring electrolyte from the anode in liquid form to the catalyst material loaded side of the current collector, the liquid electrolyte is absorbed by the catalyst. When catalyst material, as in US 6,942,943 described, in the form of long strands, an entire strand is always poisoned. In the method according to the invention, by a suitable choice of one of the second medium, for example a medium impermeable to electrolyte, a transport of electrolyte along a path can be prevented, so that such an accident only leads to a poisoning of a few sections in the environment of the impurity.

According to a variant of the method according to the invention, the first sections can also be produced by operating with only one medium containing catalyst material in the first concentration, and ejecting this catalyst material intermittently from the nozzle, while the nozzle and the current collector along the at least moves a web relative to each other. In this variant of the method, the second sections, which contain no catalyst material, result from the fact that the nozzle and the current collector are moved relative to one another while no catalyst material is ejected from the nozzle.

According to a preferred variant of the method according to the invention, catalyst concentrations in the first and second materials or media are not changed, but the catalyst movement on the surface of the current collector is varied by changing the length of the first and second sections along the at least one path.

Alternatively or additionally, one may vary the catalyst coverage on the surface of the current collector by varying the lateral density of the adjacent web segment of the at least one web or the adjacent web segments of multiple webs. For the purposes of the present invention, the at least one web is not necessarily a straight-line web, but may have any desired shape. In particular, the web can have any desired curves and in some cases also run parallel to itself so that segments formed above the above-mentioned segments are formed, over whose lateral density the catalyst coverage can be varied. Likewise, a plurality of, for example, a plurality of mutually parallel tracks may be provided, in turn, for varying the catalyst movement, the density of the adjacent web segments of the plurality of webs can be varied.

According to a further variant of the method according to the invention, the first sections, ie the sections that contribute substantially to the catalyst occupancy, in the direction of at least one web has a length of no more than 10 mm, so that locally a very precise adjustment of the desired assignment of catalyst material can be achieved.

As the catalyst material for producing the first portions, any catalyst material extrudable by a nozzle can be used. However, an aqueous suspension of a catalyst powder is preferably used as the catalyst material. This can be, for example, the in US 6,942,943 , the entire disclosure of which is hereby incorporated by reference, described catalyst material act. However, the catalyst material described there is a highly viscous, doughy Material that can only be extruded from a nozzle under high pressure.

In the process according to the invention, by contrast, a pumpable aqueous suspension is preferably used.

The pumpable catalyst material preferably consists of an aqueous suspension comprising 38 to 50% by weight of a catalyst powder, 10 to 30% by weight of a polyhydric alcohol, preferably glycerol, and 0.5 to 5% by weight of fiber materials. The catalyst powder is preferably a nickel-based catalyst powder known per se used in internal reforming. The polyhydric alcohol is preferably glycerol. The fiber material may be a mixture of longer and shorter fibers. The catalyst powder consists of particles in which 10% have a diameter of less than 1.0 μm, 50% have a diameter of less than 4.0 μm and 90% have a diameter of less than 15.5 μm. A suitable reforming catalyst for the preparation of the pumpable catalyst material is described for example in the international patent application WO 2008/104536 described, the contents of which are hereby incorporated by reference. Preferably, the viscosity of the pumpable catalyst material is less than 6000 Pa · s.

Since the catalyst material has a low viscosity when leaving the nozzle, feed speeds of 200-400 mm per second can be achieved, for example, in the case of channels having a width or depth of 2-5 mm.

Depending on the material of the current collector plate and the composition of the cast-in catalyst material, it is already possible to achieve good adhesion of the catalyst material in the depressions. According to a preferred embodiment of the method according to the invention but before the introduction of the catalyst material, the recess is at least partially coated with an adhesive to further improve the maintenance of the catalyst material in the well. Various commercially available adhesives are suitable. As an example may be mentioned based on vinyl acetate and ethylene only polymer dispersions, such as those sold by the company. Wacker Chemie AG, Munich, Germany, under the trade name VINNAPAS ^®.

After introducing the catalyst material into the depression, the catalyst material is preferably dried at a temperature of 50 to 160 ° C., more preferably at a temperature of 80 to 120 ° C., for a period of 1 to 10 minutes, preferably 2 to 5 minutes , The current collectors with the dried catalyst material can then be conditioned by burning out the catalyst material so that the catalyst material is already present in the desired porosity. Usually, however, the current collectors with the dried catalyst material are first assembled into a fuel cell stack. The burning out of the catalyst material then takes place only when the fuel cell starts up.

Glycerine and fiber materials are eliminated upon burnout of the catalyst material. In the burned-out state, the catalyst material has a porosity of preferably 65 to 75%. The catalyst material then has pores, of which preferably 40 to 50% by volume have a diameter of less than 0.01 μm. Less than 1% by volume, preferably less than 0.5% by volume, of the pores have a diameter of more than 5 μm. The remainder of the pores have a diameter of 0.01 to 5 μm.

The invention also relates to an apparatus for loading a current collector of a fuel cell with catalyst material having an applicator for applying catalyst material to the current collector in the form of at least one track on a surface of the current collector, the applicator comprising at least one nozzle for extruding a first medium containing catalyst material and means for forming successive first and second portions of said at least one web, said first portions containing catalyst material at a first concentration and said second portions containing catalyst material at a second concentration lower than said first concentration, and conveying means as appropriate are to transport at least the first medium to the nozzle of the applicator. Any pump or screw conveyor suitable for conveying the selected catalyst material, that is to say in particular an aqueous suspension of a catalyst powder having a viscosity of up to 6,000 Pas, can be used as conveying agent. Preferably, the conveyor is an eccentric screw pump.

The means for forming successive first and second portions of the at least one web are preferably selected from the group consisting of valve means for controlling the nozzle, an injector for introducing a second medium containing catalyst material in the second concentration into the nozzle, and combinations thereof ,

The invention also relates to a current collector for a fuel cell, which has a substantially planar general shape and is loaded on at least one surface with at least one path of a catalyst material, along the at least one web alternately follow first portions containing catalyst material in a first concentration and second portions containing catalyst material in a second concentration lower than the first concentration, wherein at least the first portions consist of an aqueous suspension of a catalyst powder ,

Finally, the invention relates to a fuel cell stack which comprises numerous of the above-mentioned current collectors, wherein the catalyst material applied to the current collectors has dried.

The current collectors may have any suitable shape. If in the present application of a substantially flat current collector is mentioned, so are also planar current collectors meant that have a structured surface, such as depressions and / or ribs in which or between which the catalyst pellets are arranged. Such recesses and / or ribs are preferably produced in the form of expanded metal sheets.

The invention is explained in more detail below with reference to an embodiment described with reference to the accompanying drawings.

In the drawings shows:

1 a schematic representation of the automatic filling of a current collector with catalyst pellets;

2 a schematic plan view of a current collector according to the invention in partial excavation;

3 a schematic representation of a device according to the invention for loading the current collector with the first and second sections of catalyst material;

4 a schematic representation of the applicator head of 1 ; and

5 a cross-sectional view of the applicator head of 4 along the line VV the 4 ,

In 1 schematically is a device for automatically filling a current collector 10 represented with catalyst material by the process according to the invention.

The current collector 10 in the example shown consists of an approximately 0.2 mm thick, substantially flat, nickel-coated stainless steel sheet 11 with a top 12 and a bottom 13 , which is structured by sectional folding so that on the top recesses 14 and on the bottom recesses 15 be formed. The terms "top" and "bottom" refer only to the exemplary representation of 1 and are not intended to be limiting of the orientation of the current collector in a fuel cell stack. For example, the fuel cell stack according to the invention can be arranged in a horizontal stack or else in a vertical stack. The wells 14 are in the installed state on the side remote from the anode of a fuel cell element side of the sheet 11 , The outside of the bottom section 16 the depression 14 thereby forms a bearing surface for the anode, while the outside of the bottom portion 17 the depression 15 , in the presentation of 1 So the top of the through the depression 15 formed rib-like structure which forms contact surface with the Bipolarblech of the fuel cell element.

How to get in 1 recognizes, there is every depression 14 of individual longitudinally successive and transversely offset sections 18 - 21 wherein the offset of successive sections is equal but opposite so that a substantially longitudinal channel 22 is formed.

In the example shown, the recess 14 a width of about 4 mm and the recess 15 a width of about 2 mm. The wells 14 and 15 alternate in the transverse direction, so that numerous parallel to each other channels 22 in the plane of the sheet 11 be formed. Successive sections 18 to 21 a channel 22 are transverse to the longitudinal direction of the channel 22 each offset by an offset of about 1 mm to each other, which is 50% of the width of the recess 15 equivalent. In the present embodiment, the depth of the channel is 22 about 2 mm and the length of the individual successive sections is about 3 mm. Due to the staggered sections 18 to 21 arise openings 23 in the wells that allow gas exchange between top 12 and bottom 13 of the current collector plate 11 enable. If a further improvement of the gas exchange is required, as in the example shown, additional openings in the form of holes 24 in the bottom of the wells 14 be spared, in particular to improve the access of the reformed hydrogen gas to the anode. Because the width of the wells 14 greater than the width of the wells 15 is, the anode is effectively supported, so that creeping or sinking of the anode can be avoided in the current collector. The holes 24 which preferably has a diameter between 10 and 80% of the width of the deepening 14 , more preferably a diameter of 30 to 60% of the width of the recess 14 have, do not affect the support of the anode.

With the method according to the invention by the wells 14 formed channels 22 with catalyst material 25 filled. As in 1 shown schematically, immersed to introduce the catalyst material 25 a nozzle 26 that has a nozzle opening 27 in one of the wells 14 formed channels 22 one.

The nozzle 26 is on a movable applicator head 28 one in total with the reference number 29 designated device according to the invention for loading the current collector with catalyst pellets mounted. The movement of the applicator head 28 can be realized in many different ways. Only exemplary is in the schematic representation of 1 a fully mobile robot arm 30 represented with six degrees of freedom. Such complete mobility of the applicator head 28 is usually not required. Rather, it is usually sufficient, the applicator head 28 with an XYZ gearbox sequentially along each channel 22 of the current collector 10 to move. The applicator head 28 is via a support line 31 with a storage vessel 32 connected. A pump 33 transports the catalyst material from the storage vessel 32 to the applicator head 42 , Alternatively, of course, the current collector 10 be moved relative to a stationary applicator head. In contrast to that US 6,942,943 known prior art, however, the present invention is characterized in that in the present invention, a pumpable catalyst material is used, so that is dispensed with a complex movement of the large-area current collectors when filling with catalyst material, but the filling with catalyst material realized via a movable applicator head can be, which is technically much less expensive.

According to the invention, webs of catalyst material are extruded onto the current collector, which have first and second sections, each with a different catalyst concentration. In the example of 1 has form the catalyst segments 18 and 20 each a first section containing catalyst material and the intermediate catalyst segment 19 forms one of the second sections containing less or no catalyst material.

In 2 is a schematic plan view of another variant of the current collector according to the invention shown in partial section. The current collector 34 of the 2 For example, it can be a sheet metal, the slot bridges 35 has, for example, in US 6,942,943 or in DE 195 17 451 is shown. The slot bridges 35 are arranged so that between adjacent slot bridges recesses remain recessed, the channels 36 form, in which the tracks 37 of the catalyst material can be introduced. Every track 37 of the catalyst material consists of a sequence of first sections 39 (in 2 symbolized as filled rectangles) and second sections 40 (in 2 symbolized as open rectangles), each containing different catalyst concentration, the second sections may be in particular free of catalyst material. Unlike the variant of 1 are the first and second sections in 2 not offset against each other, but form a continuous strand. Due to the different lengths of the first and second sections in different regions of the current collector, a locally varying coverage of catalyst material can be achieved. In the example shown, the current collector is installed in the fuel cell stack so that the lower edge 41 of the current collector is located at the entrance of the anode half cell and the top edge 42 at the output of the anode half cell. The left side 43 of the current collector is in the representation of 2 oriented towards the entrance of the cathode half cell, while the right side 44 the current collector to the output of the cathode half cell has. With the in 2 shown occupancy can be achieved a more uniform temperature distribution during operation of the fuel cell. At the entrance of the anode half-cell in the lower half of the fuel cell, the current density is high due to the high hydrogen content in the anode gas and much hydrogen is needed and consumed in the electrochemical oxidation of hydrogen to water so that hydrogen depletion occurs at higher levels. In this lower area, no reforming catalyst is now provided, so that the cell heats up. Rather, the reforming catalyst is arranged in the middle region of the anode half-cell, so that there methane is converted endothermically to hydrogen. The catalyst thus partially compensates for the balance shifted due to the hydrogen depletion. Since, according to the invention, the strand is interrupted again by a section without catalyst after a certain length (for example of a maximum of 10 mm), not all of the methane introduced is converted into hydrogen. However, in this section without reforming catalyst, hydrogen is still consumed due to the electrochemistry of the fuel cell. After a freely selectable route, which may also depend on the specific position within the anode half-cell, the gas again meets a section of catalyst material and a further reforming process takes place. Thus, the gas is gradually cooled and partially converted to hydrogen. The remaining methane is routed to a hot spot on the anode exit / cathode exit area and is thus available for cooling in the upper area of the fuel cell available.

It is also possible to provide shorter and, on the cathode output side, longer catalyst-free sections within the anode half-cell on the cathode input side. This can also be significantly influenced on the homogenization of the temperature distribution in the cells, as well as the mass flow in the cathode half-cell, which is performed as a cross-flow to the current in the anode half cell, a certain amount of heat or cooling power is transported.

In order to achieve a constant pressure distribution on the anode half cell from cathode input to cathode output, the occupation of the current collector must be symmetrical. This can be achieved particularly simply by virtue of the fact that the first and second sections consist of a material of essentially the same cross-section and differ only in the concentration of the catalyst material. Then the lengths of the individual sections can be optimized exclusively with a view to a uniform temperature distribution, without influencing the pressure drop.

3 shows a schematic representation of a device according to the invention for loading the current collector with the first and second sections of catalyst material. Schematically is an applicator 28 for a first medium containing the catalyst material 25 Contains, in a first concentration, that of a continuous strand of the catalyst material 25 generated. Further, an injector 46 for a second medium 47 containing catalyst material in a second concentration, for example a catalyst-free second medium, shown intermittently the second medium 47 in the continuous strand of the first medium 25 injected. It then creates a strand 48 in which there are sections 49 of the first medium with sections 50 alternate the second medium.

As the second medium may be gases such as air, a curing or burn-out organic liquid or paste, such as adhesive based on vinyl acetate, or a hardening and non-burnable liquid or paste, for example based on an Al ₂ O ₃ paste. The 4 and 5 show a schematic representation of the applicator head 28 of the 1 , the one additional injector 46 for introducing the second medium 47 into the first medium 25 having. The applicator head 28 consists of two by screws 51 connected half-shells 52 . 53 which are closely connected along the plane indicated by the line VV. 4 shows the side view and 5 a cross-sectional view of the applicator head along the plane defined by the line VV. The about the support line 31 in the applicator head 28 directed catalyst-containing first medium 25 is, for example by means of the feed pump 33 of the 1 , continuously extruded. The injector 46 may be formed, for example, for a continuous promotion of the second medium in the strand, so the first sections may consist of a combination of first and second medium and the second sections consist only of the second medium. The injector may be formed, for example, as a piezo valve, since with piezo valves very short switching times and thus short interruptions can be generated. Piezo valves of this type are available, for example, as a piezo slide from PICO Dosiertechnik GmbH & Co. KG, 82110 Germering, Germany. Thus, very high feed rates and short application times can be realized. In the example shown is via the supply line 54 the catalyst-free second medium, for example by means of a (not shown) piezo valve in the needle opening 55 the nozzle 26 of the applicator head 28 injected intermittently. The catalyst strand is thus interrupted by catalyst-free reactive material. If longer second sections are to be produced, either the delivery rate of the pump 33 reduced or for the funded first catalyst-containing material (not shown) intermediate reservoir can be initiated, so that a time-consuming startup and shutdown of the feed pump can be avoided and a high order speed of the strand can be maintained.

Surprisingly, it has been found that the temperature differences within the cell from 80 Kelvin to about 40 Kelvin can be achieved due to the more uniform methane reforming possible with the current collector according to the invention or the methane reforming adapted to the current density distribution and temperature distribution.

With the more uniform temperature distribution, not only an increase in the life of the cells, but also an increase in cell performance of currently about 1-2% per cell is possible.

If the second sections are produced with a gaseous or burnable medium, a further advantage is a surface increase of the catalyst material accessible to the fuel gas and the formation of turbulence at the edges of the extrudates, resulting in a better mixing of the gases introduced into the cell.

In addition, if an adhesive is used as the second medium, it is also ensured without additional adhesive insertion that the strand adheres well to the current collector. For example, that can first medium not only comprise a catalyst slip, but also a bonding agent, so that the adhesive is applied simultaneously with the Katalysatorschlicker. It is also possible to use the coupling agent / adhesive as the second medium and to meter in the second medium not only to form the second sections, but also to release a small amount of the second medium during delivery of the catalyst-containing first medium, so that this small amount of second medium adheres to the geometric surface of the extrudate and is discharged with the extrudate. Depending on the geometry of the nozzle and the metered quantity of the second medium, the extrudate surface can be completely or partially coated with the adhesion promoter. The first sections thus produced adhere to the current collector due to the curing of the second medium contained in the first sections. To generate the second sections, the entry quantity of the second medium can be briefly increased.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10358788 A1 [0006]
• US 5468573 [0006]
• WO 2008/141071 A1 [0006]
• US 6942943 [0006, 0017, 0022, 0046, 0048]
• US 4567117 [0007]
• US 7431746 [0008]
• WO 2008/104536 [0024]
• DE 19517451 [0048]

Claims (15)

A method for loading a current collector of a fuel cell with catalyst material, wherein provides a substantially planar current collector extruding a catalyst material through at least one nozzle and applying it along at least one path to a surface of the current collector such that first portions containing catalyst material in a first concentration along the at least one path and second portions containing catalyst material in a second concentration lower than the first concentration is consecutive. A method according to claim 1, wherein at least a first medium containing catalyst material of the first concentration is ejected from the nozzle to form the first portions, and at least a second medium containing catalyst material of the second concentration is formed to form the second portions. ejects from the nozzle while moving the nozzle and the current collector along the at least one path relative to each other. Method according to one of claims 1 or 2, wherein the second sections do not contain a catalyst material. The method of claim 3, wherein the second medium is a gaseous, liquid or pasty fluid. The method of claim 1, wherein the catalyst material is expelled intermittently from the nozzle while moving the nozzle and the current collector along the at least one path relative to each other. A method according to any one of claims 1 to 5, wherein the catalyst coverage on the surface of the current collector is varied by varying the length of the first and second sections along the at least one path. A method according to any one of claims 1 to 6, wherein the catalyst coverage on the surface of the current collector is varied by varying the lateral density of the adjacent web segments of the at least one web or the adjacent web segments of multiple webs. Method according to one of claims 1 to 7, wherein the first portions have a length in the direction of the at least one path of at most 10 mm. Process according to one of claims 1 to 8, wherein the catalyst material used to prepare the first sections is an aqueous suspension of a catalyst powder. The process according to claim 9, wherein the aqueous suspension is a pumpable aqueous suspension comprising 38 to 50% by weight of catalyst powder, 10 to 30% by weight of a polyhydric alcohol and 0.5 to 5% by weight of fiber materials. A method according to any one of claims 9 or 10, wherein the pellets applied to the current collector are dried. Device for loading a current collector of a fuel cell with catalyst material, with an applicator ( 28 ) for applying catalyst material ( 25 ) on the current collector in the form of at least one track on a surface of the current collector, wherein the applicator at least one nozzle ( 26 ) for extruding a first medium containing catalyst material ( 25 ) and means for forming successive first and second sections ( 39 . 40 ; 49 . 50 ) comprising at least one track, the first sections ( 39 . 49 ) Contain catalyst material in a first concentration, and the second sections ( 40 . 50 ) Contain catalyst material in a second concentration, which is lower than the first concentration, and conveying means ( 33 ) capable of transporting at least the first medium to the nozzle of the applicator. Apparatus according to claim 12, characterized in that the means for forming successive first and second portions of the at least one web are selected from the group consisting of valve means for controlling the nozzle, an injector for introducing a second medium, the catalyst material in the second concentration contains, in the nozzle, as well as their combinations. A current collector for a fuel cell having a generally planar general shape and loaded on at least one surface with at least one lane of catalyst material, along the at least one lane comprising first portions containing catalyst material in a first concentration and second portions containing catalyst material in contain a second concentration, which is lower than the first concentration, follow one another alternately, wherein at least the first portions consist of an aqueous suspension of a catalyst powder. A fuel cell stack comprising current collectors according to claim 14, wherein the catalyst material is dried.

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