In the hydrogen and oxygen fuel cell, hydrogen and oxygen gas are bubbled into separate compartments connected by a porous disk through which an electrolyte such as aqueous potassium hydroxide (KOH) can move. Inert graphite electrodes, mixed with a catalyst such as platinum, are dipped into each compartment. When the two electrodes are connected by a wire, the combination of electrodes, wire, and electrolyte form a complete circuit, and an oxidation-reduction reaction takes place in the cell: hydrogen gas is oxidized to form water at the anode, or hydrogen electrode electrons are liberated in this process and flow through the wire to the cathode, or oxygen electrode and at the cathode the electrons combine with the oxygen gas and reduce it. The modern hydrogen-oxygen cell, operating at about 250°C and a pressure of 50 atmospheres, gives a maximum voltage of about 1 volt.
A number of other fuel-cell technologies have been developed, but the fundamental design—anode catalyst, electrolyte, and cathode catalyst— remains the same hydrogen is the most commonly used fuel. Fuel cells are combined in a fuel-cell stack to create greater voltages or currents. Characterized by high efficiency, cleanliness, and lack of noise, fuel cells have been used to generate electricity in space flights, to produce electricity in remote locations or from landfill or waste treatement gases, and, more recently, to power automobiles.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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