Fuel cells are devices where electrical energy is produced by redox electrochemical reactions of hydrogen or enriched hydrogen fuels and oxygen, or simply air. Powerful fuel cells or stacks have emerged as potential replacements for the internal combustion engine in automobile vehicles, because the use of fuel cells implies clean and efficient use of energy, and the unique by-products are water and heat when pure hydrogen is used as fuel.
Fuel cells can find applications in transport, stationary power generation, supply of heat and electricity in buildings, in space missions for providing electricity and water, and military applications for providing electric power to electronic devices. The available energy of fuel cells is greater than the energy stored in primary or secondary batteries. This has led to a great interest in the development of fuel cells for many applications.