Hydrogen/oxygen (air) fuel cells with alkaline electrolytes

Alkaline fuel cells (AFCs) operate well at room temperature, yield the highest voltage at comparable current densities, but the use of potassium hydroxide requires the elimination of carbon dioxide from the fuel and oxidants. The electrodes can be built from low-cost porous materials (e.g., carbon, nickel-foam) with small amounts of catalysts. The components and accessories for a system with a circulating electrolyte are fully developed. AFCs excel in operating at intermittent duty cycles, for example in mobile service. But AFCs can also be used in stationary applications, such as houses (solar power) and on farms (with ammonia cracker). Military applications need sizes ranging from 150 W to several kilowatts for charging accumulators in the field. Very many different AFC systems have been developed, such as the bacon fuel cell, the Apollo/NASA space shuttle and the Russian systems, the Allis/Chalmers (static water control) H2/O2 tractor, the Union Carbide Corporation H2/O2 (150 kW) Electrovan, the Austin city car (H2/air and lead battery hybrid), the ELOFLUX system, the ELENCO system and the efforts to build an European Space Agency fuel cell power plant for the HERMES manned space vehicle, the Dornier/Siemens System and the efforts of the Swedish navy, Olle Lindstrom's work in Stockholm and his small bio-fuel cells in India, the bipolar AFC system developed in Graz and the falling film fuel cell by Hoechst. Whereby, compressed and liquid hydrogen was used or hydrogen was produced using hydrocarbon, methanol or ammonia reformers. Keywords: alkaline fuel cell systems, historical efforts, applications, electrode manufacturing