Mti Microfuel Cells Inc.

University of California

The Gillette Company

Xiaoming Ren

Shimshon Gottesfeld

Frank W Kovacs

Gerhard B Beckmann

Juan J Becerra

Kevin James Shufon

Robert S Hirsch

Michael S DeFilippis

Jay K Neutzler

Eric J Brown

Paul F Mutolo

Lena A Guleserian

John Davey

Piotr Zelenay

Michael Patrick Manning

Cynthia A Rice

Steven Z Shi

Ashish K Modi

Sharon C Thomas

A simplified direct oxidation fuel cell system is provided. The fuel cell is constructed in such a manner that fuel is added to the cell anode as it is consumed and water is evaporated off at cell cathode so that there is no need for recirculation of unreacted fuel at the cell anode or water at the cell cathode. In addition, carbon dioxide generated from the anodic reaction is passively vented out of the system by using a CO2 gas permeable membrane material integrated as part of the anode chamber construction. It is thus possible that, the CO2 separation from the anode fluid occurs without the recirculation of the anode fluid outside the anode chamber. The passive system in which fuel is added as it is consumed and CO2 separated, both without pumping, ultimately will increase net power provided to the load due to low parasitic losses.

Method of controlling delivery of fuel to a direct oxidation fuel cell

Passive water management techniques are provided in an air-breathing direct oxidation fuel cell system. A highly hydrophobic component with sub-micrometer wide pores is laminated to the catalyzed membrane electrolyte on the cathode side. This component blocks liquid water from traveling out of the cathode and instead causes the water to be driven through the polymer membrane electrolyte to the cell anode. The air-breathing direct oxidation fuel cell also includes a layer of cathode backing and additional cathode filter components on an exterior aspect of the cell cathode which lessen the water vapor escape rate from the cell cathode. The combination of the well laminated hydrophobic microporous layer, the thicker backing and the added filter layer, together defines a cathode structure of unique water management capacity, that enables to operate a DMFC with direct, controlled rate supply of neat (100%) methanol, without the need for any external supply or pumping of water. The cell anode is provided with a hydrophilic backing layer. When the water is driven through the polymer membrane electrolyte from the cell cathode to the cell anode chamber, it is available for the anodic reaction, and any excess water is carried out along COventilation channels to the outside environment.

Passive water management techniques in direct methanol fuel cells

The present invention provides a viscous fuel, which includes a fuel substance held in a polymeric structure, where the viscous fuel has benefits over previous fuels, including performance enhancements and desirable physical characteristics. One embodiment of the formulation includes neat methanol, to which a thickening substance, such as that sold commercially under the trade name Carbopol&#xae;, is added to impart viscosity, as well as stabilizing and suspending properties. In addition to the thickening substance, a further substance can be added to balance the pH of the viscous fuel when needed.

Fuel formulation for direct methanol fuel cell

A fuel reservoir having a reticulated material, generally a felt or a foam, disposed therein is provided. The addition of this reticulated material, either alone or in combination with a viscous fuel, assists the prevention of undesired flow of the fuel, the minimization of undesired leakages, and assists in orientation independence and uniform distribution of the fuel in the reservoir. The reticulated material enables the use of a viscous liquid fuel that has fuel diffusion rates and fuel utilization characteristics that approach those of neat liquid methanol. The material also helps create a greater surface area for evaporation, thus allowing a highly concentrated, vaporous fuel substance to be delivered to an associated fuel cell.

Fuel container with reticulated material

A passive direct oxidation fuel cell system, which uses a high concentration fuel such as neat methanol as a direct feed to an anode aspect of the fuel cell, is provided. The fuel cell includes a passive water management capability, achieved by the combined functions of controlled fuel dosing, effective push back of liquid water from the cathode through the membrane electrolyte by a hydrophobic microporous layer well bonded to the cathode catalyst and the use of a thin ionomeric membrane. The rate of fuel delivery is controlled by a passive fuel transport barrier. Carbon dioxide management techniques are also provided.

Direct oxidation fuel cell operating with direct feed of concentrated fuel under passive water management

Fuel mixtures for direct methanol fuel cells are disclosed. The fuels include methanol and additives that react with water to produce methanol and other easily electro-oxidizable compounds including dimethyloxymethane, methylorthoformate, tetramethylorthocarbonate, trimethylborate, and tetramethylorthosilicate. Other additives to improve safety and efficiency of the fuel cell include sulfonated activated carbon particles and metal hydrides, such as LiAlH, NaBH, LiBH, (CH)NHBH, NaAlH, BH, NaCNBH, CaH, LiH, NaH, KH or sodium bis (2-methoxyethoxy) dihydridaluminate.

Fuel composition in fuel cartridges for DMFCs

A fuel cell diffusion layer for delivering a fuel mixture to the anode face of a catalyzed membrane and for resisting flow of carbon dioxide produced in the anodic reaction back into the associated fuel chamber. The diffusion layer contains either conduits or channels on one aspect thereof to redirect the carbon dioxide generated at the anode in the fuel cell reaction away from the catalyzed membrane and away from the fuel chamber. This avoids the volume replacement by carbon dioxide of fuel mixture in the anode chamber and enhances the concentration of methanol that can be used in the fuel mixture. It also serves to allow only that fuel that is consumed in the reaction to enter the space between the anode face of the catalyzed membrane and the diffusion layer adjacent thereto. The diffusion layer further includes perforations to increase the ability to deliver fuel to the anode aspect of the membrane electrode assembly of the fuel cell. In accordance with another aspect of the invention, the perforations can comprise Nafion-filled capillaries.

Anode diffusion layer for a direct oxidation fuel cell

The present invention provides a gel fuel, which includes a fuel substance held in a polymeric structure. One embodiment of the composition includes neat methanol, to which a thickening substance, such as that sold commercially under the trade name Carbopol&#xae;, is added to impart viscosity, as well as stabilizing and suspending properties. In addition to the thickening substance, a further substance can be added to balance the pH of the gel fuel when needed. In accordance with the invention, a fuel cell cartridge is provided that has at least one aspect that is methanol-permeable, and which may include a fuel vapor permeable layer and it may be comprised of one of a number of various alternative materials. Features within the fuel cartridge can be used to increase surface area of the gel fuel, and to maintain the gel fuel in a desired location within the cartridge.

Fuel substance and associated cartridge for fuel cell

A fuel cell diffusion layer providing a preferential path by which liquid reactants or byproducts may be supplied to or removed from a direct oxidation fuel cell is described. The modified diffusion layer will be typically on the cathode side of the fuel cell and its use is to eliminate or minimize flooding of the cathode diffusion layer area, which is a performance limiting condition in direct methanol fuel cells. In accordance with one embodiment of the invention, the diffusion layer includes a substrate that is coated with a microporous layer. A pattern may be embossed into the diffusion layer, to create preferential flow paths by which water will travel and thereby be removed from the cathode catalyst area. This avoids cathode flooding and avoids build up of potentially destructive pressure by possible cathodic water accumulation. This also provides a means for collecting cathode water for redirection In accordance with another aspect of the invention, the preferential path is established by applying a thicker microporous layer to the carbon cloth or carbon paper and drying it in such a fashion so that when it dries, the surface of the microporous layer cracks to provide the pathways.

Modified diffusion layer for use in a fuel cell system

A fuel cell stack has a plurality of polymer electrolyte fuel cells (PEFCs) where each PEFC includes a rectangular membrane electrode assembly (MEA) having a fuel flow field along a first axis and an air flow field along a second axis perpendicular to the first axis, where the fuel flow field is long relative to the air flow field. A cathode air flow field in each PEFC has air flow channels for air flow parallel to the second axis and that directly open to atmospheric air for air diffusion within the channels into contact with the MEA.

Fuel cell stack with passive air supply

A simplified direct oxidation fuel cell system is provided. The fuel cell is constructed in such a manner that fuel is added to the cell anode as it is consumed and water is evaporated off at cell cathode so that there is no need for recirculation of unreacted fuel at the cell anode or water at the cell cathode. In addition, carbon dioxide generated from the anodic reaction is passively vented out of the system by using a CO2 gas permeable membrane material integrated as part of the anode chamber construction. Other embodiments of the invention include a fuel container and delivery assembly.

Simplified direct oxidation fuel cell system

Methods for conditioning the membrane electrode assembly of a direct methanol fuel cell ('DMFC') are disclosed. In a first method, an electrical current of polarity opposite to that used in a functioning direct methanol fuel cell is passed through the anode surface of the membrane electrode assembly. In a second method, methanol is supplied to an anode surface of the membrane electrode assembly, allowed to cross over the polymer electrolyte membrane of the membrane electrode assembly to a cathode surface of the membrane electrode assembly, and an electrical current of polarity opposite to that in a functioning direct methanol fuel cell is drawn through the membrane electrode assembly, wherein methanol is oxidized at the cathode surface of the membrane electrode assembly while the catalyst on the anode surface is reduced. Surface oxides on the direct methanol fuel cell anode catalyst of the membrane electrode assembly are thereby reduced.

Methods of conditioning direct methanol fuel cells

A system and method for removal or oxidative decomposition of fuel from a fuel storage container for use in a direct oxidation fuel cell and direct oxidation fuel cell system wherein the fuel permeates through a material and can be exposed to a catalyst/enzyme which oxidizes the fuel as it leaves the storage container. The system includes a fuel storage container provided with a catalyst-coated material. An airtight seal is provided over the catalyzed area, which seal is broken to allow oxygen access, and consequently the catalytic reaction. The airtight seal may be broken by simple manual methods or automatic methods on removal of the container from the fuel cell system.

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Menands, NY, United States of America

Xiaoming Ren