The articles in this issue of MRS Bulletin highlight the enormous potential of fuel cells for generating electricity using multiple fuels and crossing a wide range of applications. Fuel cells convert chemical energy directly into electrical energy, and as a powergeneration module, they can be viewed as a continuously operating battery.They take in air (or pure oxygen, for aerospace or undersea applications) and hydrocarbon or hydrogen fuel to produce direct current at various outputs. The electrical output can be converted and then connected to motors to generate much cleaner and more fuelefficient power than is possible from internal combustion engines, even when combined with electrical generators in today's hybrid engines. The commercialization of these fuel cell technologies is contingent upon additional advances in materials science that will suit the aggressive electrochemical environment of fuel cells (i.e., both reducing an oxidizing) and provide ionic and electrical conductance for thousands of hours of operation.
