Fuel Cells and Hydrogen: From Fundamentals to Applied Research

The five major types of fuel cells (PEFC, PAFC, AFC, MCFC, and SOFC) are differentiated mainly on the basis of their electrolytes. International research and commercialization efforts in the low-temperature region are focused on PEFC development. This chapter provides a short introduction to additional low-temperature polymer electrolyte fuel cells (PEFCs).

The motivations to develop these different types of fuel cells are manifold. The requirement of higher operating temperatures for combined heat and power generation, as well as for efficient heat removal, leads to the development of high-temperature PEFCs, the possibility of replacing expensive noble metal catalysts to alkaline fuel cells, and the necessity of utilizing liquid fuels for direct fuel cells, such as direct alcohol fuel cells, direct borohydride fuel cells, or direct hydrazine fuel cells. The complex reaction mechanisms of liquid fuels increases the overvoltage losses, and the produced inert diluent CO2 has to be removed from the electrode, and vented from the system.