The Proton Exchange Membrane Fuel Cell (PEMFC)
Figure 1. A cartoon of the Proton Exchange Membrane fuel cell.
A major thrust of the hydrogen economy is to replace carbon-based fuels in transportation with hydrogen. One of the most promising candidates for this particular application is the PEMFC (Proton Exchange Membrane Fuel Cell) as it operates at low temperatures (less than 110 oC), is rather efficient, can be miniaturized and can cover a large power range. Fuel cell buses are being trialed in a number of countries as a result of the extensive research and development of these fuel cells for the past few decades. The proton exchange membrane fuel cell was first developed by General Electric in the United States in the 1960's for use by NASA on their first manned space vehicles.
PEM fuel cells use a solid polymer membrane (a thin plastic film) as the electrolyte. This polymer is permeable to protons when it is saturated with water, but it does not conduct electrons.
The fuel for the PEMFC 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.
