Polymer Electrolyte Fuel Cell

Polymer Electrolyte Fuel Cells (PEFC) are used as the vehicular power source to eventually replace gasoline and diesel internal combustion engines. First used in the 1960s for the NASA Gemini program, PEFCs are currently being developed and demonstrated for systems ranging from 1W to 2kW. PEFC fuel cells use a solid polymer membrane (a thin plastic film) as electrolyte. This polymer is permeable to protons when it is saturated with water, but it does not conduct electrons. The fuel for the PEFC is hydrogen and the charge carrier is the hydrogen ion (proton). At the anode, the hydrogen molecule is split into hydrogen ions (protons) and electrons. The hydrogen ions permeate across the electrolyte to the cathode while the electrons flow through an external circuit and produce electric power. Oxygen, usually in the form of air, is supplied to the cathode and combines with the electrons and the hydrogen ions to produce water. The reactions at the electrodes are as follows:

Anode Reactions: 2H2 => 4H+ + 4e-

Cathode Reactions: O2 + 4H+ + 4e- => 2 H2O

Overall Cell Reactions: 2H2 + O2 => 2 H2O