Methods for forming catalytic coating on a substrate

Abstract

The present invention is directed to methods for forming a catalytic coating on a substrate. The method comprises preparing a catalytic fluid and dispensing the catalytic fluid onto a substrate by using a direct writing instrument. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that is will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 10/201,828, filed Jul. 24, 2002.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to fuel cells and particularly, to methods for forming a catalytic coating on a substrate.

SUMMARY OF THE INVENTION

[0003] According to the present invention, methods for forming a catalytic coating on a substrate are provided.

[0004] In one embodiment, a method of forming a catalytic coating on a substrate is provided. According to the method, a catalytic fluid is prepared and dispensed onto a substrate using a direct writing instrument that has been programmed to dispense the catalytic fluid onto the substrate in a pattern that forms a catalytic coating on the first side of the substrate.

[0005] In another embodiment, a method of forming a catalytic coating on a substrate is provided. According to the method, a catalytic fluid is dispensed onto a substrate using a direct writing instrument that has been programmed to dispense the catalytic fluid onto the substrate in a pattern that forms a first coating on a first side of the substrate. A noncatalytic fluid is also dispensed onto the first side of the substrate using the same direct writing instrument in a shadow pattern of the first coating to form a second coating on the first side of the substrate.

[0006] In still another embodiment, a method of preparing an electrolyte membrane for use in a membrane electrode assembly is provided. According to the method a catalytic fluid is dispensed onto an intermediate material using a direct writing instrument that has been programmed to dispense the catalytic fluid in a pattern that forms a catalytic coating on the intermediate material. The catalytic coating is then transferred from the intermediate material to an electrolyte membrane.

[0007] In still yet another embodiment, a method of preparing an electrolyte membrane for use in a membrane electrode assembly is provided. According to the method, a catalytic fluid is dispensed onto an electrolyte material using a direct writing instrument.

[0008] In still another embodiment, a method of preparing a diffusion media for use in a fuel cell is provided. According to the method, a catalytic fluid is dispensed onto a diffusion media using a direct writing instrument.

[0009] In yet another embodiment, a system for preparing a membrane electrode assembly is provided. The system comprises first and second coating stations, first and second drying stations, a cutting station and a carrier device. The first coating station comprises a first substrate holding device, and at least one coating head for applying a coating to a first side of a substrate. The second coating station comprises a second substrate holding device, and at least one coating head for applying a coating to a second side of a substrate. The carrier device is configured to carry the substrate from station to station.

[0010] These and other features and advantages of the invention will be more fully understood from the following description of the invention taken together with the accompanying drawings. It is noted that the scope of the claims is defined by the recitations therein and not by the specific discussion of features and advantages set forth in the present description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following detailed description can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0012] FIG. 1 is a schematic illustration of a fuel cell system.

[0013] FIG. 2 is a schematic illustration of a vehicle including a fuel cell system.

[0014] FIG. 3 is a schematic illustration of a fuel cell stack employing two fuel cells.

[0015] FIG. 4 is an exploded view of a membrane electrode assembly.

[0016] FIG. 5 is a block diagram of a direct writing instrument according to one embodiment of the present invention.

[0017] FIG. 6 is an illustration of the nozzle and nozzle tip of a direct writing instrument forming a pattern on a substrate according to one embodiment of the present invention.

[0018] FIG. 7 is an illustration of a pattern according to one embodiment of the present invention.

[0019] FIG. 8 is an illustration of a pattern according to one embodiment of the present invention.

[0020] FIG. 9 is an illustration of a membrane electrode assembly according to one embodiment of the present invention.

[0021] FIG. 10 is an illustration of one side of a membrane electrode assembly having a first and a second coating according to one embodiment of the present invention.

[0022] FIG. 11 is an illustration of a membrane electrode assembly system according to one embodiment of the present invention.

[0023] FIG. 12a is an illustration of an ultrasonic probe applied above to a substrate.

[0024] FIG. 12b is an illustration of an ultrasonic probe applied below a substrate.

[0025] Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.

DETAILED DESCRIPTION

[0026] Referring to FIG. 1, a fuel cell system 2 for automotive applications is shown. It is to be appreciated, however, that other fuel cell system applications, such as for example, in the area of residential systems, may benefit from the present invention. As illustrated, the fuel cell system 2 includes a primary reactor 4, a water-gas shift reactor 6, a preferential oxidation (PrOx) reactor 7, at least one heat exchanger 8, a tail gas combustor 9, and a fuel cell 10. An explanation of these components and the operation of the fuel cell system 2 follows. It is to be appreciated that while one particular fuel cell system design is described, the present invention may be applicable to any fuel cell system design where catalytic coatings are utilized.

[0027] In the primary reactor 4 a hydrocarbon fuel, such as gasoline or methane, air and steam are mixed, heated, and delivered to a catalyzed substrate. Here, the mixture is split into hydrogen, carbon monoxide, and other process gases, as the mixture flows over and reacts with the catalyst, forming a hydrogen-rich stream. Suitable catalyst materials include platinum group metals and base metals. This reaction occurs at temperatures in the range between about 700° C. and about 800° C.

[0028] The hydrogen-rich stream leaving the primary reactor 4 enters the water-gas shift reactor 6. Oxygen from water is used to convert carbon monoxide to carbon dioxide leaving additional hydrogen and increasing system efficiency. Operating temperatures of the shift reactor 6 range from about 250° C. to about 450° C. The hydrogen-rich stream leaving the shift reactor 6 then enters into the PrOx reactor 7, where the final cleanup of carbon monoxide takes place before the hydrogen-rich stream enters the fuel cell stack. Air is added to supply the oxygen needed to convert most of the remaining carbon monoxide to carbon dioxide, leaving additional hydrogen behind. Operating temperatures in the PrOx reactor 7 range from about 80° C. to about 200° C. Combined, the three reactors extract hydrogen from the fuel, and reduce or eliminate harmful emissions.

[0029] The three reactors are quickly heated to their operating temperatures before the fuel is introduced. The heat exchanger 8 is therefore used to regulate the various temperatures throughout the fuel cell system 2. Typically, the heat exchanger 8 preheats the steam and air streams before entering into the primary reactor 4. The waste heat from the hydrogen-rich stream exits the primary reactor 4.

[0030] The hydrogen-rich stream then is supplied to the fuel cell 10, which may comprise a stack of fuel cells, and reacted with oxygen from a source, such as air, to produce electricity, which can be used to power a load 11. The small quantities of unused hydrogen that leave the fuel cell 10 are consumed in the tail gas combustor 9 which operates at a temperature between about 300° C. to about 800° C. It is to be appreciated that while a series of reactors is described as being the hydrogen source, any hydrogen source is applicable to the present invention.

[0031] Referring to FIG. 2, a vehicle is shown having a vehicle body 90, and a fuel cell system having a fuel cell processor 4 and a fuel cell stack 15. A discussion of the present invention as embodied in a fuel cell stack and a fuel cell, is provided hereafter in reference to FIGS. 3-9.

[0032] FIG. 3 depicts a fuel cell stack 15 having a pair of membrane-electrode-assemblies (MEAs) 20 and 22 separated from each other by an electrically conductive fluid distribution plate 30. Plate 30 serves as a bi-polar plate having a plurality of fluid flow channels 35, 37 for distributing fuel and oxidant gases to the MEAs 20 and 22. By “fluid flow channel” we mean a path, region, area, or any domain on the plate that is used to transport fluid in, out, along, or through at least a portion of the plate. The MEAs 20 and 22, and plate 30, are stacked together between clamping plates 40 and 42, and electrically conductive fluid distribution plates 32 and 34. Plates 32 and 34 serve as end plates having only one side containing channels 36 and 38, respectively, for distributing fuel and oxidant gases to the MEAs 20 and 22, as opposed to both sides of the plate.

[0033] Nonconductive gaskets 50, 52, 54, and 56 provide seals and electrical insulation between the several components of the fuel cell stack. Gas permeable diffusion media material 60, 62, 64, and 66 press up against the electrode faces of the MEAs 20 and 22. Plates 32 and 34 press up against the diffusion media material 60 and 66 respectively, while the plate 30 presses up against the diffusion media material 62 on the anode face of MEA 20, and against diffusion media material 64 on the cathode face of MEA 22.

[0034] An oxidizing fluid, such as O2, is supplied to the cathode side of the fuel cell stack from storage tank 70 via appropriate supply plumbing 86. While the oxidizing fluid is being supplied to the cathode side, a reducing fluid, such as H2, is supplied to the anode side of the fuel cell from storage tank 72, via appropriate supply plumbing 88. The reducing fluid may be derived from a mixture of methane or gasoline, air, and water according to a reforming process in the presence of a catalyst. Exhaust plumbing (not shown) for both the H2 and O2/air sides of the MEAs will also be provided. Additional plumbing 80, 82, and 84 is provided for supplying liquid coolant to the plate 30 and plates 32 and 34. Appropriate plumbing for exhausting coolant from the plates 30, 32, and 34 is also provided, but not shown.

[0035] Referring to FIG. 4, an exploded view of membrane electrode assembly 20 is shown comprising an anode layer 102, a cathode layer 106, and an electrolyte 104 separating the anode layer 102 and the cathode layer 106. Membrane electrode assembly 20 and membrane electrode assembly 22 are identical. For simplicity purposes, the present invention is being described in relation to membrane electrode assembly 20, it is to be appreciated that the present invention can be applied to membrane electrode assembly 22 and membrane electrode assemblies in general.

[0036] Generally, the anode layer 102 and the cathode layer 106 are coatings formed in such a manner that they are in intimate contact with the electrolyte material once the fuel cell 10 (FIG. 1) is assembled. Methods of forming a catalytic coating on a substrate will now be explained. The first step in the method is to prepare a catalytic fluid. Generally, the catalytic fluid is a solution of ionomer, precious metal catalyst, solvent and water. A solution of ionomer and precious metal catalyst istypically prepared on a support in a mixture of the solvent and water. Different amounts maybe used depending on the desired viscosity of the catalytic fluid and the carbon to ionomer ratio desired. Generally, between about 30 grams and about 250 grams of solvent is mixed with between about 130 grams and about 200 grams of water and between about 5 grams and about 30 grams of ionomer and between about 5 grams and about 20 grams of precious metal catalyst are mixed together to form a solution. The support used for the solution of the ionomer and precious metal catalyst is typically carbon having a high surface area. The amount of carbon is generally between about 5 grams and about 20 grams. More specifically, the catalytic solution comprises about 4% by wt. of precious metal, about 4% by wt. of ionomer, about 4% by wt. of carbon, about 28% by wt. of water and about 60% by wt. of solvent.

[0037] The precious metal catalyst can be selected from platinum, platinum alloys and combinations thereof. The solvent can be selected from isopropyl alcohol, ethanol, butanol, and combinations thereof. The catalytic fluid can be prepared to exhibit a viscosity between about 70 cp and about 2000 cp, and more specifically, a viscosity of about 300 cp. The catalytic fluid can be prepared to exhibit an ionomer to carbon ratio of about 0.8 to about 2.0. The amount of solid in the solution is between about 8% by wt. and about 20% by wt., and more specifically about 12% by wt.

[0038] Once the catalytic fluid is prepared, it is dispensed onto a substrate 110 using a direct writing instrument. By “direct writing,” we mean depositing fluid directly onto a surface of a substrate in a pattern defined by the motion of the instrument, the motion of the substrate, or both. In direct writing, the deposited fluid forms a relatively well-defined line or area of deposition, relative to the overall dimensions of the deposition surface or the deposited pattern. Relative motion between the fluid source and the deposition substrate increases the extent of the well-defined line or area of deposition to create a more extensive deposited pattern.

[0039] FIG. 5 shows one embodiment of a direct writing instrument according to the present invention. The direct writing instrument 150 comprises a design system 152, a writing system controller 154 and a writing system 160. The writing system 160 further comprises a fluid dispensing system 168, a nozzle 166, a nozzle tip 167, and a substrate holding device 162. The design system 152 stores a pattern that is drawn on a graphic display. The design system 152 electronically communicates with the writing system controller 154 such that the writing system controller 154 knows the pattern and controls the writing system 160 in a manner that allows the writing system 160 to draw the pattern stored in the design system 152 on the substrate 110.

[0040] Referring to FIGS. 5 and 6, the writing system controller 154 electronically communicates with the fluid dispensing system 168 and the substrate holding device 162. Therefore, the writing system controller 154 allows the fluid dispensing system 168 to deliver the catalytic fluid to the nozzle 166. The catalytic fluid is dispensed through the nozzle tip 167 onto the substrate 110. The catalytic fluid may be carried to the fluid dispensing system 168 by any suitable means.

[0041] The writing system controller 154 allows the substrate holding device 162 to move in a variety of positions that form the pattern 170 stored in the design system. By moving the substrate holding device 167 in various positions, the substrate 110 is accurately placed under the nozzle tip 167 while the catalytic fluid is being dispensed onto the substrate 110. In this manner, the nozzle 166 and the nozzle tip 167 do not move, but remain stationary while dispensing the catalytic fluid. Also, the pressure of the nozzle tip 167 is controlled such that no direct surface contact with the substrate 110 occurs. In another embodiment, the substrate holding device 162 remains stationary while the nozzle 166 and nozzle tip 167 move over the substrate 110 while dispensing the catalytic fluid.

[0042] The design system 152 may be any computer-aided-design (CAD) interface that allows the design of a pattern via a graphics editor, digitizing tablet, or interface through a generic photo plotter interface. The nozzle 166 may be heated to allow the catalytic fluid to remain in a molten state so that it will easily dispense through the nozzle tip 167. The width and thickness of the line, or lines, 169 forming the pattern 170 depend upon the nozzle tip diameter, the volumetric flowrate of the fluid to the nozzle tip, and the writing speed. The writing speed may vary depending upon the movement of the substrate 110 relative to the nozzle tip 167 or the movement of the nozzle tip 167 the substrate. Thus, the line thickness can be determined by the following equation: t=Q/(Vw), wherein Q=volumetric flow rate, w=line width, V=writing speed, and t=the line thickness. Viscosity of the fluid determines how close the line width is to the nozzle tip diameter, i.e. a low viscosity fluid will flow, therefore the line width is greater than the nozzle tip diameter while a high viscosity fluid does not flow as well, therefore, the line width is about equivalent to the nozzle tip diameter.

[0043] The nozzle tip 167 can produce at least one line having a width between about 0.002 inches to about 0.25 inches. If more than one line is desired, a space up to about 0.0005 inches can be made between the lines. The line thickness can be up to 0.010 inches per pass with the nozzle. The line can have tolerances of about +/−0.000025 inches. The instrument writes at a speed between about 0.05 inches per second to about 5.0 inches per second. The instrument 150 operates on a minimum grid pitch of 0.0005 inches.

[0044] The pattern 170 formed on the substrate 110 can be selected from a rectangular spiral, a straight line, a series of lines, or any suitable geometric pattern. An example of a pattern 170 having a line, or series of lines, 169 forming a rectangular spiral is shown in FIG. 7. The spacing between adjacent lines can be adjusted. For the case of no spacing between adjacent lines, the pattern 170 would form a single continuous coating over the entire substrate 110. FIG. 8 shows a pattern 170 having a series of lines 169 formed by a direct writing instrument according to one embodiment of the present invention.

[0045] Typically, after the pattern is formed on the substrate 110, the substrate 110 is dried by a heat source having a temperature between about 70° C. and about 100 ° C. The pattern, once dried, forms a coating on the substrate 110. The heat source is selected from an infrared heater, convective oven, heated jets, or any other suitable heating device for removing solvent from the catalytic fluid. The substrate 110 is subjected to the heat for a time sufficient to evaporate primarily all of the solvent in the coating, more specifically between about 2 minutes to about 10 minutes.

[0046] The method of making the membrane electrode assembly may vary depending upon the substrate upon which the catalytic fluid is dispensed. The substrate is generally selected from an intermediate material, a diffusion media material, or electrolyte membrane material.

[0047] If the substrate is an intermediate material then the catalytic solution is deposited in the programmed pattern onto the intermediate material by a direct writing instrument. The coated substrate is then dried at a temperature between about 70° C. to about 100° C., typically in an oven. After the substrate is dry, a secondary ionomer solution may be applied to the substrate and dried. The application of the ionomer solution is typically performed by spraying. The coating formed on the intermediate material is then transferred to an electrolyte membrane material typically using a hot-press transfer. In one embodiment of the present invention, a second fluid that is nonreactive may be applied onto the intermediate material after the deposition of catalytic fluid or simultaneously with the catalytic fluid. The coating formed on the intermediate material is then transferred to an electrolyte membrane material. The intermediate material is typically selected from polytetrafluoroethlyene, ethylene tetrafluoroethylene, or variations thereof. The noncatalytic fluid is described in detail below.

[0048] A second substrate that can be used in the present invention is a diffusion media material. If the diffusion media material is used, the catalytic fluid is prepared as described above and then deposited onto the diffusion media material using a direct writing instrument as described above in any of the patterns described above. The coated diffusion media material is then subjected to drying. The diffusion media material can be any suitable diffusion media material used in fuel cells. In one embodiment of the present invention, a second fluid that is noncatalytic fluid may be applied onto the diffusion media material after the deposition of catalytic fluid or simultaneously with the catalytic fluid.

[0049] As an alternative, the substrate can be the electrolyte membrane material. Therefore, the catalytic fluid is deposited directly onto the electrolyte membrane material. The coated electrolyte membrane material is then subjected to drying. The electrolyte membrane material may be a proton conducting membrane, such as perfluorinated sulfonic acid, or some variation thereof.

[0050] In one embodiment of the present invention, a second fluid that is noncatalytic may be applied onto the electrolyte membrane material after the deposition of catalytic fluid or simultaneously with the catalytic fluid, thereby forming a catalytic coating and a noncatalytic coating on one side of the electrolyte membrane material. Referring to FIG. 9, an MEA 180 having both the catalytic coating 182 and the noncatalytic coating 184 is shown. The noncatalytic fluid forms a noncatalytic coating 184 when dried. The noncatalytic fluid is deposited in such a manner that it “shadows” the catalytic fluid. By “shadow” we mean that one fluid follows the outline of the other fluid such that one fluid is not deposited directly over the other fluid. When used, the noncatalytic fluid fills in the spaces between the lines of catalytic fluid on the substrate 202.

[0051] The noncatalytic fluid comprises a material that exhibits a high electrical conductivity, a high thermal conductivity, and low porosity. The noncatalytic fluid may be a carbonaceous material, carbon black, graphite, or combinations thereof. The carbonaeous material may also comprise a polymeric binder such as polyimide, polyethylene terephthalate, and combinations thereof. The viscosity of the noncatalytic fluid can be adjusted as appropriate to readily fill regions between catalytic coatings illustrated in FIG. 9. Generally, the noncatalytic fluid exhibits a viscosity between about 300 cp and about 10,000 cp. The noncatalytic fluid can be dispensed such that it is thicker on the substrate than the catalytic fluid.

[0052] Referring to FIG. 10, one embodiment of an MEA 180 having a catalytic coating 182 and a noncatalytic coating 184 is shown. The catalytic fluid can be deposited in a pattern that allows the lines of the catalytic coating 182 to align with channels in a flow field plate. The noncatalytic fluid can then be deposited in pattern that allows the lines of the noncatalytic coating 184 to align with the lands 186 in the flow field plate. This can be accomplished on both sides of the substrate 202 such that the catalytic fluid forming the catalytic anode coating 182a is aligned with the channels 185 of the anode flow field plate. Therefore, the noncatalytic coating 184 lies between the spaces of the catalytic fluid or catalytic anode coating 182a, forming a noncatalytic coating 184 on the lands 186 of the anode flow field plate. Similarly on the cathode side of the MEA 180, the catalytic fluid forming the catalytic cathode coating 182b is aligned with the channels 187 of the cathode flow field plate. Thus, the noncatalytic fluid is deposited between the spaces of the catalytic fluid or catalytic cathode coating 182b, forming a noncatalytic coating 184 on the lands 186 of the cathode flow field plate. The catalytic anode coating 182a and catalytic cathode coating 182b are shown to be narrower than the opening of the channels 185, 187, respectively. It is to be appreciated that the catalytic anode coating 182a and the catalytic cathode coating 182b may be formed such that the coating is as wide as channels 185, 817 or wider. This concept is explained in more detail in application Ser. No. 10/201,828.

[0053] When the noncatalytic fluid is used, to form a noncatalytic coating 184 on the substrate 202 and the substrate is an electrolyte membrane material, the fuel cell may eliminate the use of the diffusion media material in a fuel cell. Thus, the resulting fuel cell would be identical to the fuel cell 10 shown in FIG. 3, however, the diffusion media 60, 62, 64, and 66 would not be present.

[0054] Referring to FIG. 11, an MEA fabrication system 200 according to one embodiment of the present invention is shown. The system has three primary stations: a first coating station, a second coating station, and a die cutting station. The substrate 202 is placed on a feed roll 212 where the substrate 202 is pulled from station to station by rollers 216, 218, 224, and 226. At the first coating station the substrate 202 is pulled over a first substrate holding device 214. Once over the first substrate holding device 214, a nozzle 210a dispenses catalytic fluid directly onto the first side 202a of the substrate 202. The catalytic fluid is typically dispensed in the form of a pattern, as described above. The substrate 202 is then pulled to first drying area 215. The first drying area 215 can be an array of heated jets, an infrared heater, convection oven, or any other suitable device for removing a majority of solvent from the catalytic fluid. The first drying area 215 typically maintains a temperature between about 70° C. and about 100° C. While in first drying area 215 the catalytic fluid dries to the substrate 202 and forms a catalytic coating on the substrate 202. The catalytic coating may be either an anode coating or a cathode coating.

[0055] Next, the substrate 202 is pulled to a second coating station. In the second coating station, the substrate 202 is pulled over a second substrate holding device 228. A catalytic fluid is deposited onto the second side 202b of the substrate 202. The catalytic fluid may be dispensed onto the substrate 202 in a manner that forms a pattern as discussed above. While being pulled through first drying area 215, the substrate 202 is turned in a manner that allows the first side 202a of the substrate 202 to face the opposite side such that nozzle 220a is placing catalytic fluid on the second side 202b of the substrate 202. After the catalytic fluid is placed onto the second side 202b of the substrate 202, the substrate 202 is pulled to a second drying area 222. The second drying area 222 can be an array of heated jets, an infrared heater, convection oven, or any other suitable device for removing a majority of solvent from the catalytic fluid. The second drying area 222 typically maintains a temperature between about 70° C. to about 100° C. While in second drying area 222, the catalytic fluid deposited on the second side 202b of the substrate 202 forms a catalytic coating over the substrate 202. The catalytic coating may be either an anode coating or a cathode coating.

[0056] The substrate 202 is then pulled to a cutting station 230 where the substrate 202 is cut into separate pieces such that each piece of substrate 202 has both an anode coating and a cathode coating. The substrate 202 may be further cut in such a manner as to not interrupt a pattern that may have been formed on the substrate 202 by the fluid.

[0057] As FIG. 11 shows, more than one nozzle 210a, 210b, 220a, and 220b can be used at each station to deposit more than one fluid onto the substrate 202 at a time. While only two nozzles are shown at each station, it is to be appreciated that an array of nozzles can be present. When more than one fluid is deposited at a time, one fluid may shadow the other fluid. Although the noncatalytic fluid is described above as being the second fluid, it is to be appreciated that the second fluid can be any desired fluid. For example, the second fluid can be a fluid containing a high amount of precious metal that is deposited near the inlet and exit of the MEA. Then a fluid have a lower amount of precious metal can be deposited in the center of the MEA, thereby, alleviating a portion of the durability and mass transfer losses.

[0058] The nozzles 210a, 210b, 220a, and 220b are typically attached to a direct writing instrument as described above. The fluid is typically dispensed onto the substrate 202 in the form of one of the patterns as described above. The catalytic fluid is prepared as described above. The first and second substrate holding devices 214 and 228 can be vacuum tables or any other suitable device for holding the substrate in place.

[0059] Referring to FIGS. 12a and 12b, an additional step to the method of applying more than one fluid to the substrate is shown. Ultrasonic energy can be applied to assist with coating of the substrate 202. An ultrasonic probe 250 can be placed over the catalytic fluid 240 and the noncatalytic fluid 242 as the fluids are dispensed from nozzles 210a and 210b onto the substrate 202. The ultrasonic probe 250 transmits acoustic energy 251 through the air above the contact line 241 of the catalytic fluid 240 and the noncatalytic fluid 242 as shown in FIG. 12a. Referring specifically to FIG. 12b, the ultrasonic probe 250 can be placed below the substrate 202 to transmit acoustic energy 251 through the substrate 202 as the catalytic fluid 240 and the noncatalytic fluid 242 are dispensed from nozzles 210a and 210b. The acoustic energy 251 is transmitted at the contact line 241 of the catalytic fluid 240 and the noncatalytic fluid 242.

[0060] The acoustic energy 251 is applied continuously to the contact line 241, such that surface tension at the liquid-liquid interface is continuously lowered at the point of application, thereby enabling better fluid flow and creating a smooth interface between fluids 240 and 242. It is to be appreciated that while FIGS. 12a and 12b are shown using nozzles 210a and 210b which operate at the first coating station, it is to be appreciated that FIGS. 12a and 12b also show nozzles 220a and 220b which operate at the second coating station. It is also to be appreciated that the acoustic energy 251 can be used in any suitable method system for making the MEA having two fluids, comprising both a catalytic and noncatalytic fluid, dispensed onto a substrate both a catalytic fluid and a noncatalytic fluid. It is further to be appreciated that while this step is explained using acoustic energy from an ultrasonic probe, any instrument or energy that can relieve surface tension at the liquid-liquid interface can be used.

[0061] While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.

Claims

1. A method of forming a catalytic coating on a substrate comprising:

preparing a catalytic fluid; and

dispensing said catalytic fluid onto a substrate, having a first side and a second side, using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said substrate in a pattern that forms a catalytic coating on said first side of said substrate.

2. A method as claimed in claim 1, wherein said method further comprises drying said catalytic fluid after said catalytic fluid is dispensed onto said first side of said substrate.

3. A method as claimed in claim 1, wherein said act of preparing a catalytic fluid comprises:

preparing a mixture of between about 30 grams and about 250 grams of solvent and between about 130 grams and about 200 grams of water; and

preparing a solution between about 5 grams and about 30 grams of ionomer and between about 5 grams and about 20 grams of platinum supported on a high surface area carbon in said mixture of solvent and water.

4. A method as claimed in claim 1, wherein said catalytic fluid comprises at least one ionomer, at least one precious metal, carbon, a solvent, and water.

5. A method as claimed in claim 4, wherein said at least one ionomer comprises a perfluorinated polymer.

6. A method as claimed in claim 4, wherein said at least one precious metal comprises platinum.

7. A method as claimed in claim 4, wherein said at least one ionomer and at least one precious metal are supported by said carbon.

8. A method as claimed in claim 4, wherein said solvent comprises isopropyl alcohol.

9. A method as claimed in claim 1, wherein said catalytic fluid comprises about 4% by wt. of platinum, about 4% by wt. of ionomer, about 4% by wt. of carbon, about 28% by wt. of water and about 60% by wt. of solvent.

10. A method as claimed in claim 1, wherein said catalytic fluid comprises perfluorinated polymer and carbon and exhibits a perfluorinated polymer to carbon ratio of about 0.8 to about 2.0.

11. A method as claimed in claim 1, wherein said catalytic fluid exhibits a viscosity between about 70 cp and about 2000 cp.

12. A method as claimed in claim 1, wherein said catalytic fluid exhibits a viscosity of about 300 cp.

13. A method as claimed in claim 1, wherein said catalytic fluid comprises between about 8% and about 20% solids.

14. A method as claimed in claim 1, wherein said catalytic fluid comprises about 12% solids.

15. A method as claimed in claim 1, wherein said catalytic fluid supports hydrogen oxidation.

16. A method as claimed in claim 1, wherein said catalytic fluid supports oxygen reduction.

17. A method as claimed in claim 1, wherein said substrate is selected from an electrolyte material, a polytetrafluoroethlyene sheet, and a gas diffusion media.

18. A method as claimed in claim 17, wherein said electrolyte material comprises a proton conducting membrane.

19. A method as claimed in claim 17, wherein said electrolyte material comprises perfluorinated sulfonic acid.

20. A method as claimed in claim 1, wherein said catalytic coating is dispensed such that it has a substantially uniform thickness across said first side of said substrate.

21. A method as claimed in claim 1, wherein said catalytic coating is configured to increase the probability of ionization of a hydrogen-based fuel.

22. A method as claimed in claim 1, wherein said catalytic coating is configured to increase the probability of a reaction of a hydrogen ion with oxygen.

23. A method as claimed in claim 1, wherein said direct writing instrument is configured such that the width and thickness of a line forming said pattern depends upon the diameter of the direct writing instrument from which said catalytic fluid is dispensed and the volumetric flowrate of said catalytic fluid.

24. A method as clamed in claim 23, wherein said line thickness t is determined by:

t=Q/(Vw),

wherein Q represents volumetric flow rate of said catalytic fluid,

wherein V represents writing speed of said direct writing instrument, and

wherein w represents line width.

25. A method as claimed in claim 1, wherein said pattern comprises a configuration selected from a rectangular spiral, a straight line, a series of lines, or a single continuous coating over the entire substrate.

26. A method as claimed in claim 1, wherein said pattern comprises a series of lines configured to align with at least one flow field channel of a fuel cell.

27. A method as claimed in claim 1, wherein said catalytic coating forms a conductive layer on said first side of said substrate.

28. A method as claimed in claim 1, wherein said method further comprises applying ultrasonic energy to said substrate.

29. A method as claimed in claim 28, wherein said ultrasonic energy is applied to said first side of said substrate after said dispensing of said catalytic fluid on said first side of said substrate.

30. A method as claimed in claim 28, wherein said ultrasonic energy is applied to said second side of said substrate after said dispensing of said catalytic fluid on said first side of said substrate.

31. A method as claimed in claim 1, wherein said method further comprises dispensing a second fluid onto said first side of said substrate using a direct writing instrument that has been programmed to dispense said second fluid onto said substrate in a pattern that forms a second coating on said first side of said substrate.

32. A method as claimed in claim 31, wherein said second fluid comprises a noncatalyic fluid.

33. A method as claimed in claim 31, wherein said second fluid comprises a precious metal.

34. A method as claimed in claim 33, wherein said precious metal comprises platinum.

35. A method as claimed in claim 31, wherein said second fluid is deposited at the periphery of the first side of said substrate.

36. A method as claimed in claim 1, wherein said method further includes dispensing said catalytic fluid onto said second side of said substrate using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said substrate in a pattern that forms a catalytic coating on said second side of said substrate.

37. A method as claimed in claim 36, wherein said method further comprises dispensing a second fluid onto said second side of said substrate using a direct writing instrument that has been programmed to dispense said second fluid onto said substrate in a pattern that forms a second coating on said second side of said substrate.

38. A method as claimed in claim 37, wherein said second fluid comprises a noncatalytic fluid.

39. A method as claimed in claim 38, wherein said noncatalytic fluid is dispensed in a shadow pattern of said catalytic fluid to form a second coating on said first side of said substrate.

40. A method as claimed in claim 37, wherein said second fluid comprises a precious metal.

41. A method as claimed in claim 40, wherein said precious metal comprises platinum.

42. A method as claimed in claim 40, wherein said second fluid is deposited at the ends of the second side of said substrate.

43. A method of forming a catalytic coating on a substrate comprising:

providing a catalytic fluid;

dispensing said catalytic fluid onto a substrate, having a first and second side, using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said first side of said substrate in a pattern that forms a catalytic coating on said first side of said substrate; and

dispensing a noncatalytic fluid onto said first side of said substrate using said direct writing instrument that has been programmed to dispense said noncatalytic fluid in a shadow pattern of said first coating to form a noncatalytic coating on said first side of said substrate.

44. A method as claimed in claim 43, wherein said noncatalytic fluid comprises a carbonaceous material.

45. A method as claimed in claim 44, wherein said carbonaceous material comprises a material exhibiting high electrical conductivity.

46. A method as claimed in claim 44, wherein said carbonaceous material comprises a material exhibiting high thermal conductivity.

47. A method as claimed in claim 44, wherein said carbonaceous material comprises a material exhibiting low porosity.

48. A method as claimed in claim 44, wherein said carbonaceous material comprises carbon black, graphite, and combinations thereof.

49. A method as claimed in claim 43, wherein said shadow pattern fills any spaces in the pattern of said first coating.

50. A method as claimed in claim 43, wherein said noncatalytic fluid is dispensed simultaneously with said catalytic fluid.

51. A method as claimed in claim 43, wherein said noncatalytic coating and said catalytic coating are formed simultaneously.

52. A method as claimed in claim 43, wherein said noncatalytic coating is formed after the formation of said catalytic coating.

53. A method as claimed in claim 43, wherein said catalytic and said noncatalytic coatings are dispensed independently from said direct writing instrument.

54. A method as claimed in claim 43, wherein said noncatalytic fluid has a higher viscosity than said catalytic fluid.

55. A method as claimed in claim 43, wherein said noncatalytic fluid exhibits a viscosity between about 300 cp and about 10,000 cp.

56. A method as claimed in claim 43, wherein said noncatalytic fluid is thicker than said catalytic fluid.

57. A method as claimed in claim 43, wherein said catalytic fluid exhibits a viscosity between about 70 cp and about 2000 cp.

58. A method as claimed in claim 43, wherein said catalytic fluid exhibits a viscosity of about 300 cp.

59. A method as claimed in claim 43, wherein said catalytic coating on said first side of said substrate is configured to align with flow field channels of a fuel cell.

60. A method as claimed in claim 43, wherein said noncatalytic coating on said first side of said substrate is configured to align flow field lands of a fuel cell.

61. A method as claimed in claim 43, wherein said catalytic coating on said first side of said substrate is configured to align with flow field channels of a fuel cell while said noncatalytic coating on said first side of said substrate is configured to align with flow field lands of a fuel cell.

62. A method as claimed in claim 43, wherein said method further comprises:

dispensing said catalytic fluid onto said second side of said substrate using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said second side of said substrate in a pattern that forms a catalytic coating on said second side of said substrate; and

dispensing said noncatalytic fluid onto said second side of said substrate using said direct writing instrument, wherein said direct writing instrument has been programmed to dispense said noncatalytic fluid on said second side of said substrate in a shadow pattern of said catalytic fluid to form a noncatalytic coating on said second side of said substrate.

63. A method as claimed in claim 62, wherein said catalytic coating on said second side of said substrate is configured to align with flow field channels of a fuel cell.

64. A method as claimed in claim 62, wherein said noncatalytic coating on said second side of said substrate is configured to align with flow field lands of a fuel cell.

65. A method as claimed in claim 62, wherein said catalytic coating on said second side of said substrate is configured to align with flow field channels of a fuel cell while said second coating on said second side of said substrate is configured to align with flow field lands of a fuel cell.

66. A method of preparing an electrolyte membrane for use in a membrane electrode assembly comprising:

preparing a catalytic fluid;

dispensing said catalytic fluid onto an intermediate material using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said intermediate material in a pattern that forms a catalytic coating on said intermediate material; and

transferring said catalytic coating from said intermediate material to an electrolyte membrane.

67. A method as claimed in claim 66, wherein said method further comprises drying said catalytic fluid after said catalytic fluid is dispensed onto said substrate.

68. A method as claimed in claim 66, wherein a secondary ionomer solution is applied to said intermediate material.

69. A method as claimed in claim 68, wherein said secondary ionomer solution is applied to said intermediate material by spraying.

70. A method as claimed in claim 68, wherein said intermediate material is dried after said secondary ionomer solution is applied.

71. A method as claimed in claim 66, wherein said intermediate material is selected from polytetrafluoroethylene or ethylene tetrafluoroethylene, or variations thereof.

72. A method as claimed in claim 66, wherein said transferring said first coating from said intermediate material to said electrolyte membrane is performed by a hot-press.

73. A method as claimed in claim 72, wherein said hot-press is set at a temperature between about 140° C. to about 165° C.

74. A method as claimed in claim 72, wherein said hot-press uses a pressure between about 1300 kPa to about 4000 kPa.

75. A method as claimed in claim 66, wherein said electrolyte membrane comprises perfluorinated sulfonic acid or some variation thereof.

76. A method as claimed in claim 66, wherein said method further comprises dispensing a noncatalytic fluid onto said intermediate material using said direct writing instrument that has been programmed to dispense said noncatalytic fluid in a shadow pattern of said first coating to form a noncatalytic coating on said intermediate material.

77. A method of preparing an electrolyte membrane for use in a membrane electrode assembly comprising:

preparing a catalytic fluid; and

dispensing said catalytic fluid onto an electrolyte material using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said electrolyte material in a pattern that forms a catalytic coating on said electrolyte material.

78. A method as claimed in claim 77, wherein said method further comprises drying said electrolyte material after said catalytic fluid is dispensed on said electrolyte material.

79. A method of preparing a diffusion media for use in a fuel cell comprising:

preparing a catalytic fluid; and

dispensing said catalytic fluid onto a diffusion media using a direct writing instrument that has been programmed to dispense said catalytic fluid onto said diffusion media in a pattern that forms a catalytic coating on said diffusion media.

80. A method as claimed in claim 79, wherein said method further comprises drying said diffusion media after said catalytic fluid is dispensed on said diffusion media.

81. A method as claimed in claim 79, wherein said diffusion media comprises carbon fiber, carbon cloth, and combinations thereof.

82. A system for preparing a membrane electrode assembly comprising:

a first coating station comprising a first substrate holding device, and at least one coating head for applying a coating to a first side of a substrate;

a first drying station;

a second coating station comprising a second substrate holding device, and at least one coating head for applying a coating to a second side of a substrate;

a second drying station;

a cutting station; and

a carrier device configured to carry said substrate to each station.

83. A system as claimed in claim 82, wherein said first substrate holding device comprises a vacuum table.

84. A system as claimed in claim 82, wherein said first coating station forms a conductive coating on said first side of said substrate.

85. A system as claimed in claim 82, wherein said second substrate holding device comprises a vacuum table.

86. A system as claimed in claim 82, wherein said second coating station forms a conductive coating on said second side of said substrate.

87. A system as claimed in claim 82, wherein said first drying station comprises a heat source.

88. A system as claimed in claim 87, wherein said heat source is selected from an infrared heat source, heated jets, convection oven, and combinations thereof.

89. A system as claimed in claim 82, wherein said second drying station comprises a heat source.

90. A system as claimed in claim 89, wherein said heat source is selected from an infrared heat source, heated jets, convection oven, and combinations thereof.

91. A system as claimed in claim 82, wherein said cutting station comprises a die-cutting station.

92. A system as claimed in claim 82, wherein said carrier device comprises a feed roll.

93. A system as claimed in claim 82, wherein said substrate is selected from an intermediate material, an electrolyte material, and a diffusion media material.

94. A system as claimed in claim 93, wherein said intermediate material is selected from polyfluorotetraethlyene or ethylene tetrafluoroethylene.

95. A system as claimed in claim 93, wherein said electrolyte membrane comprises perfluorinated sulfonic acid or variations thereof.

96. A system as claimed in claim 93, wherein said diffusion media comprises carbon fiber, carbon cloth, and combinations thereof.

97. A method of fabricating an article incorporating a fuel cell, said method comprising:

providing a fuel supply manifold;

providing an oxidant supply manifold;

preparing a membrane electrode assembly by acts comprising,

preparing a catalytic fluid,

dispensing said catalytic fluid onto an intermediate material using a direct writing instrument that has been preprogrammed to dispense said catalytic fluid onto said intermediate material in a pattern that forms a catalytic coating on said intermediate material,

transferring said catalytic coating from said intermediate material to a first side of an electrolyte membrane,

dispensing said catalytic fluid onto an intermediate material using a direct writing instrument that has been preprogrammed to dispense said catalytic fluid onto said intermediate material in a pattern that forms a catalytic coating on said intermediate material, and

transferring said catalytic coating from said intermediate material to a second side of said electrolyte membrane; and

positioning said membrane electrode assembly between said fuel supply manifold and said oxidant supply manifold.

98. A method as claimed in claim 97, wherein said article comprises a vehicle at least partially powered by said fuel cell.

99. A method as claimed in claim 97, wherein said article comprises a power supply at least partially powered by said fuel cell.

100. A method of fabricating an article incorporating a fuel cell, said method comprising:

providing a fuel supply manifold;

providing an oxidant supply manifold;

preparing a membrane electrode assembly by acts comprising,

preparing a catalytic fluid,

dispensing said catalytic fluid onto an electrolyte material, having a first and second side, using a direct writing instrument that has been preprogrammed to dispense said catalytic fluid onto said electrolyte material in a pattern that forms a catalytic coating on said first side of said electrolyte material, and

dispensing said catalytic fluid onto said electrolyte material using a direct writing instrument that has been preprogrammed to dispense said catalytic fluid onto said electrolyte material in a pattern that forms a catalytic coating on said second side of said electrolyte material; and

positioning said membrane electrode assembly between said fuel supply manifold and said oxidant supply manifold.

101. A method as claimed in claim 100, wherein said article comprises a vehicle at least partially powered by said fuel cell.

102. A method as claimed in claim 100, wherein said article comprises a power supply at least partially powered by said fuel cell.

103. A method of fabricating an article incorporating a fuel cell, said method comprising:

providing a fuel supply manifold;

providing an oxidant supply manifold;

dispensing a catalytic fluid onto a diffusion media using a direct writing instrument that has been preprogrammed to dispense said catalytic fluid onto said first diffusion media in a pattern that forms a catalytic coating on said first diffusion media;

placing said first diffusion media adjacent said first manifold;

dispensing said catalytic fluid onto a second diffusion media using a direct writing instrument that has been preprogrammed to dispense said catalytic fluid onto said second diffusion media in a pattern that forms a catalytic coating on said second diffusion media;

placing said second diffusion media adjacent said second manifold; and placing an electrolyte material between said first and second diffusion medias.

104. A method as claimed in claim 103, wherein said article comprises a vehicle at least partially powered by said fuel cell.

105. A method as claimed in claim 103, wherein said article comprises a power supply at least partially powered by said fuel cell.