United Technologies Corporation

The United States of America As Represented by the United States

International Fuel Cells, LLC

United States of America As Represented by the Secretary of the Air Force

Union Technologies Corporation

Murray Katz

Arthur Kaufman

Robin J Guthrie

Craig R Schroll

H Russell Kunz

Harold R Kunz

Donald L Maricle

Stanley P Bonk

Gary A Gruver

Martin L Abrams

A fuel cell stack is cooled by evaporation of water into a carrier gas such as fuel or oxidant. The coolant and the carrier gas are separately supplied to the cooler, and this allows the fuel cell to operate at high pressure without raising cell temperature.

Fuel cell evaporative cooler

The end plates (16) of a fuel cell stack (12) are formed of a thin membrane. Pressure plates (20) exert compressive load through insulation layers (22, 26) to the membrane. Electrical contact between the end plates (16) and electrodes (50, 58) is maintained without deleterious making and breaking of electrical contacts during thermal transients. The thin end plate (16) under compressive load will not distort with a temperature difference across its thickness. Pressure plate (20) experiences a low thermal transient because it is insulated from the cell. The impact on the end plate of any slight deflection created in the pressure plate by temperature difference is minimized by the resilient pressure pad, in the form of insulation, therebetween.

Fuel cell end plate structure

A fuel cell has a current collector plate (22) located between an electrode (20) and a separate plate (25). The collector plate has a plurality of arches (26, 28) deformed from a single flat plate in a checkerboard pattern. The arches are of sufficient height (30) to provide sufficient reactant flow area. Each arch is formed with sufficient stiffness to accept compressive load and sufficient resiliently to distribute the load and maintain electrical contact.

Fuel cell current collector

An electrolytic cell stack includes inactive electrolyte reservoirs at the upper and lower end portions thereof. The reservoirs are separated from the stack of the complete cells by impermeable, electrically conductive separators. Reservoirs at the negative end are initially low in electrolyte and the reservoirs at the positive end are high in electrolyte fill. During stack operation electrolyte migration from the positive to the negative end will be offset by the inactive reservoir capacity. In combination with the inactive reservoirs, a sealing member of high porosity and low electrolyte retention is employed to limit the electrolyte migration rate.

Electrolytic cell stack with molten electrolyte migration control

Electrolyte lost from a fuel cell, such as by evaporation, is replenished by introducing electrolyte from an external source into a reactant gas stream being delivered into the cell. The fresh electrolyte is vaporized or formed into droplets as it enters the cell such as by spraying the fresh electrolyte into the gas stream. If the electrolyte vapor pressure in the entering gas stream is made high enough, evaporation of the electrolyte from the cell can be halted or electrolyte can even be added to the cell from the gas stream.

Method for replacing lost electrolyte in fuel cells

Electrical short protection is provided in an electrolytic cell stack by the combination of a thin, nonporous ceramic shield and a noble metal foil disposed on opposite sides of the sealing medium in a gas manifold gasket. The thin ceramic shield, such as alumina, is placed between the porous gasket and the cell stack face at the margins of the negative end plate to the most negative cells to impede ion current flow. The noble metal foil, for instance gold, is electrically coupled to the negative potential of the stack to collect positive ions at a harmless location away from the stack face. Consequently, corrosion products from the stack structure deposit on the foil rather than on the stack face to eliminate electrical shorting of cells at the negative end of the stack.

Short protection device for stack of electrolytic cells

Ammonia gas is scrubbed from a gas stream in a bed of material soaked with acid, and the bed is regenerated by passing an oxygen containing gas therethrough. The preferred acid is phosphoric acid and the preferred support material is carbon in the form of porous particles. In a fuel cell system dual scrubbers alternately scrub ammonia from reform gas and are subsequently regenerated so as to provide the fuel cells with a continuous flow of substantially ammonia free hydrogen.

Regenerable ammonia scrubber

A porous conducting particle, hydrophobic bonded, substrate supported electrode is prewetted with the electrolyte. A D.C. voltage is applied to the electrode to assist in the prewetting with the electrolyte. A soluble catalyst-containing material is then introduced into the electrode structure and the catalyst deposited within the electrode. By appropriate selection of the porous conducting particles and the catalyst-applying techniques, precise control of the location of the catalyst can be obtained. If graphite materials are used as the conducting particles, a catalyst-containing salt is allowed to dissolve in the electrolyte in the prewetted electrode, and the catalyst-containing material is reduced to the metal. If the reduction is done by reaction with a reducing gas such as hydrogen, the catalyst will be deposited only in those regions of the electrode at which there is an electrolyte-reactant gas interface which is in electrical-conducting relationship with the substrate. Alternatively, extremely precise amounts of catalyst can be deposited within the electrode structure by use of a solution of a compound of the catalyst whose wettability with the hydrophobic material varies as the solution evaporates. By this technique almost 100% of the catalyst can be deposited within the electrode structure on the hydrophilic region, with virtually no losses in the hydrophobic material.

Method for catalyzing a fuel cell electrode and an electrode so produced

In a fuel cell stack utilizing an alkali metal electrolyte, the electrolyte is distributed in parallel between the electrodes of a plurality of fuel cells and is then fed to regenerator cell which converts carbonate ions to molecular CO.sub.2 gas which is discharged from the cell. Regeneration is effected through the establishment of a hydroxyl ion gradient within a regenerator cell. The regenerated electrolyte is then returned to the fuel cells. In this manner a carbonate buildup in the cells is prevented.

Electrolyte regeneration in a fuel cell stack

A porous conducting particle, hydrophobic bonded, substrate supported electrode is prewetted with the electrolyte. A D.C. voltage is applied to the electrode to assist in the prewetting with the electrolyte. A soluble catalyst-containing material is then introduced into the electrode and the catalyst deposited within the electrode. By appropriate selection of the porous conducting particles and the catalyst-applying techniques, precise control of the location of the catalyst can be obtained. If graphite materials are used as the conducting particles, a catalyst-containing salt is allowed to dissolve in the electrolyte in the prewetted electrode, and the catalyst-containing material is reduced to the metal. If the reduction is done by reaction with a reducing gas such as hydrogen, the catalyst will be deposited only in those regions of the electrode at which there is an electrolyte-reactant gas interface which is in electrical-conducting relationship with the substrate. Alternatively, extremely precise amounts of catalyst can be deposited within the electrode structure by use of a solution of a compound of the catalyst whose wettability with the hydrophobic material varies as the solution evaporates. By this technique almost 100% of the catalyst can be deposited within the electrode structure on the hydrophilic region, with virtually no losses in the hydrophobic material.

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Newington, CT, United States of America

Murray Katz