Fuel cells are devices that convert the chemical energy of a fuel directly into electrical energy by electrochemical reactions. Fuel cells are considered to be one of the main solutions for the efficient utilization of fossil fuel-derived fuels. The concept of fuel cells was discovered by William R. Grove, a Scotsman, during the late 1830s. Grove discovered that by arranging two platinum electrodes with one end of each immersed in a container of sulfuric acid and the other ends separately sealed in containers of hydrogen and oxygen, a constant current would flow between the electrodes. The sealed containers held water as well as the gases, and Grove noted that the water level rose in both tubes as the current flowed. In 1800, William Nicholson and Anthony Carlisle in England had described the process of using electricity to decompose water into hydrogen and oxygen (the electrolysis of water). But combining hydrogen and oxygen to produce electricity and water was, according to Grove, "...a step further that any hitherto recorded." Grove realized that by combining several sets of these electrodes in a series circuit he might ".effect the decomposition of water by means of its composition." His device, which he named a "gas battery", was the first ever fuel cell.
However, the device remained a curiosity with no practical application in sight until, more than a century later, in 1953, Sir Francis T. Bacon constructed the first fuel cell prototype with a power output in the kW range. Bacon began experimenting with alkali electrolytes in the late 1930s, settling on potassium hydroxide (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 nickel 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 occurred. Bacon also used pressurized gases to keep the electrolyte from "flooding" the tiny pores in the electrodes. Over the course of the following 20 years, Bacon made enough progress with the alkali cell to present large-scale fuel cell demonstration units. The U.S. space agency, NASA selected alkali fuel cells for the Space Shuttle fleet, as well as for the Apollo program, mainly because of power-generating efficiencies that approach 70%. Importantly, alkali cells also provided clean drinking water for the astronauts. The cells use platinum catalysts that are expensive (perhaps too expensive for commercial applications), but several companies are examining ways to reduce costs and improve the cells' versatility by using less-expensive cobalt catalysts. Most of these alkali fuel cells are currently being designed for transport applications.
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