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Alkali Fuel Cells

Technology History Applications

The essay below outlines the technology and history of alkali fuel cells as currently understood by the project team. If you have artifacts, photos, documents, or other materials that would help to improve our understanding of these devices be sure to respond to the questionnaire:
Collecting Fuel Cell History


Alkali Fuel Cell Technology

Alkali fuel cells operate on compressed hydrogen and oxygen and generally use a solution of potassium hydroxide in water as their electrolyte. Operating temperatures inside alkali cells are around 150 to 200 degrees C (about 300 to 400 degrees F).

photo of soldier using a fuel cell powered drill, about 1965
A U.S. Army soldier demonstrates an alkali fuel cell.

In these cells, hydroxyl ions (OH-) migrate from the cathode to the anode. At the anode, hydrogen gas reacts with the OH- ions to produce water and release electrons. Electrons generated at the anode supply electrical power to an external circuit then return to the cathode. There the electrons react with oxygen and water to produce more hydroxyl ions that diffuse into the electrolyte.

Alkali fuel cells operate at efficiencies up to 70 percent and, like other fuel cells, create little pollution. Because they produce potable water in addition to electricity, they have been a logical choice for spacecraft. A major drawback, however, is that alkali cells need very pure hydrogen or an unwanted chemical reaction forms a solid carbonate that interferes with chemical reactions inside the cell. Since most methods of generating hydrogen from other fuels produce some carbon dioxide, this need for pure hydrogen has slowed work on alkali fuel cells in recent years. Another drawback has been the need for large amounts of a costly platinum catalyst to speed up the reaction. Researchers have worked to reduce the amount of platinum needed, and have eliminated the metal entirely from some designs.



Alkali Fuel Cell History

Francis Thomas Bacon (1904-1992) of Britain began experimenting with alkali electrolytes in the late 1930s, settling on potassium hydroxide (or KOH) instead of using the acid electrolytes known since Grove's early discoveries. KOH performed as well as acid electrolytes and was not as corrosive to the electrodes. Bacon's cell also used porous "gas-diffusion electrodes" rather than solid electrodes as Grove had used. Gas-diffusion electrodes increased the surface area in which the reaction between the electrode, the electrolyte and the fuel occurs. Also, Bacon used pressurized gases to keep the electrolyte from "flooding" the tiny pores in the electrodes. Over the course of the following twenty years, Bacon made enough progress with the alkali cell to present large scale demonstrations.

One of the first of these demonstrations consisted of a 1959 Allis-Chalmers farm tractor powered by a stack of 1,008 cells. With 15,000 watts of power, the tractor generated enough power to pull a weight of about 3,000 pounds. (The tractor was later donated to the Smithsonian.) Allis-Chalmers maintained a research program for some years, building a fuel cell powered golf cart, submersible, and fork lift. The U.S. Air Force also participated in this program.

photo of Karl Kordesch riding his fuel cell powered motorcycle.
Union Carbide's Karl Kordesch rides his alkali fuel cell motorcycle in 1967.

Union Carbide also experimented with alkali cells in the late 1950s and 1960s. Building on the work done in the 1930s by researchers G. W. Heise and E. A. Schumacher, Karl Kordesch and his colleagues designed alkali cells with carbon gas-diffusion electrodes. They demonstrated a fuel-cell-powered mobile radar set for the U.S. Army, a fuel-cell-powered motorbike (see photo), and drew up plans for an undersea base that would run on fuel cells. About the same time, Eduard Justi of Germany designed gas-diffusion electrodes using nickel sponge on a carbonyl nickel matrix.

In the early 1960s, aircraft engine manufacturer Pratt & Whitney licensed the Bacon patents and won the National Aeronautics and Space Administration (NASA) contract to power the Apollo spacecraft with alkali cells. Its successes notwithstanding, alkali technology has challenges ahead. Current alkali fuel cells still demand very pure hydrogen and expensive platinum catalysts, and other kinds of fuel cells are mounting stiffer competition.



Alkali Fuel Cell Applications

NASA selected alkali fuel cells for the Space Shuttle fleet, as well as the Apollo program, mainly because of power generating efficiencies that approach 70 percent. Alkali cells also provide drinking water for the astronauts. The cells are expensive -- perhaps too expensive for commercial applications -- but several companies are examining ways to reduce costs and improve the cells' versatility. Most of these alkali fuel cells are being designed for transport applications.
photo of Project Apollo fuel cell, 1964
A Pratt & Whitney alkali fuel cell being assembled for an Apollo spacecraft, 1964

In July 1998, the Zero Emission Vehicle Company (ZEVCO) launched its first prototype taxi in London, England. The taxi uses a 5,000-watt alkali fuel cell that produces no noxious fumes and much less noise than traditional internal combustion taxis. (The company reports one inquiry from an English police agency looking for a "stealth" cruiser that would allow them to sneak up on criminals.) The ZEVCO cells reportedly use cobalt catalysts instead of platinum reducing the high cost. The company has also introduced a series of other commercial vehicles including delivery vans, airport tow-tugs, and an associated company is demonstrating fuel-cell-powered boats.


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