(1) An electrochemical device for continuously converting chemicals—a fuel and an oxidant—into direct-current electricity. It consists of two electronic-conductor electrodes separated by an ionic-conducting electrolyte with provision for the continuous movement of fuel, oxidant, and reaction product into and out of the cell. The fuel can be gaseous, liquid, or solid; the electrolyte liquid or solid; the oxidant gaseous or liquid. The electrodes are solid but may be porous and may contain a catalyst. Fuel cells differ from batteries in that electricity is produced from chemical fuels fed to them as needed, so that their operating life is theoretically unlimited. The cell products can be regenerated externally into fuel for return to the cell, e.g., carbon dioxide from the cell can be reacted with coal to form carbon monoxide for feed to the cell. Fuel is oxidized at the anode (negative electrode), giving electrons to an external circuit; the oxidant accepts electrons from the anode and is reduced at the cathode. Simultaneously with the electron transfer, an ionic current in the electrolyte completes the circuit. One type of electrolyte is a solid polymer of perfluorinated sulfonic acid. The fuels range from hydrogen, carbon monoxide, and carbonaceous materials to redox compounds, alkali metals, and biochemical materials. Fuel cells based on hydrogen and oxygen have a significant future as a primary energy source. Cells of this type are under development for use as a power source for electric automobiles, the hydrogen being derived from methanol. Large-scale development of fuel cells for on-site power generation for housing units is well advanced, and research has been completed for construction of a 26-megawatt cell capable of serving the needs of a small community.(2) An aircraft fuel tank or container made of or lined with an oil-resistant synthetic rubber.
