A whole family of fuel cells now exists that can be characterized by the electrolyte used — and by a related acronym as listed in Table 1.1. All of these fuel cells function in the same basic way. At the anode, a fuel (usually hydrogen) is oxidized into electrons and protons, and at the cathode, oxygen is reduced to oxide species. Depending on the electrolyte, either protons or oxide ions are transported through the ion-conducting but electronically insulating electrolyte to combine with oxide or protons to generate water and electric power.

Polymer Electrolyte Membrane Fuel Cells (PEMFC) are able to generate high power densities efficiently. This an attractive feature of these type of fuel cells for portable and mobile applications. Proton exchange membrane fuel cells differentiates itself from other fuel cell technologies with the use of a solid polymer phase as a gas separator and electrolyte. Membrane basically functions for proton conduction and details of these fuel cell components are briefly explained in the fuel cell components section.Because the cell separator is a polymer film and the cell operates at relatively low temperatures,
issues such as sealing, assembly, and handling are less complex than most other fuel cells. The need to handle corrosive acids or bases is eliminated in this system.

Proton exchange membrane fuel cells (PEMFCs) typically operate at low temperatures (60^oC to 80 ^oC), allowing for potentially faster startup than higher temperature fuel cells. The PEFC is seen as the main fuel cell candidate technology for light-duty transportation applications. While PEFC are particularly suitable for operation on pure hydrogen, fuel processors have been developed that will allow the use of conventional fuels such as natural gas or gasoline.

Typical cell components within a Polymer Electrolyte Fuel Cell stack include:
• proton exchange membrane (e.g. nafion membrane)
• an electrically conductive porous backing layer (gas diffussion layers)

• an electro-catalyst (the electrodes) at the interface between the backing layer and the
membrane
• cell interconnects and flowplates that deliver the fuel and oxidant to reactive sites via flow
channels and electrically connect the cells