Electrochemical device such as a battery stores chemicals inside converting these chemicals into electricity on demand. When the chemicals are all used up the battery is then dead and has to be recharged or throw away.
Fuel cells generate electricity efficiently and without pollution. Unlike power sources that use fossil fuels, the by-products from an operating fuel cell are heat and water. In a fuel cell there is a flow of Hydrogen which generates electricity and water for as long as there is Hydrogen flowing through. The Hydrogen is the chemical used.
Polymer exchange membrane fuel cell (PEMFC) uses a simple reaction to produce electricity
http://upload.wikimedia.org/wikipedia/en/5/5c/Fc_diagram_pem.gif
At the Negative Pole (the anode) excess electrons (negative charges) are released from the Hydrogen. These electrons will move through the electrical circuit. Hydrogen is removed from the surface of the catalyst.
At the Negative Pole (the cathode) Oxygen arrives from the atmosphere and pushes the electrons back to the catalyst where they combine with Hydrogen and Oxygen to form water.
The proton exchange membrane forms the Electrolyte. It is made of a thin plastic type of membrane containing only positive ions preventing electrons from passing through and must remain moist at all times to function correctly.
Platinum is an ideal metal to be used as the Catalyst as it is not used up in the reaction. It has a rough surface which increases the surface area for the reactions.
http://www.chfcc.org/images/hydrogenfuelcell.gif
Summary
Fuel cells produce electricity though an electrochemical process using hydrogen as fuel and oxygen from the air. The by-products of this reaction are heat and water vapor. There are several types of fuel cells. Altergy’s products utilize the Proton Exchange Membrane or PEM fuel cell.
In the simplest terms, here is the process by which a PEM fuel cell produces electricity:
1.Hydrogen gas enters a fuel cell at the anode (negative cathode) where it attaches to a catalyst layer.
2.The catalyst facilitates the disassociation of the hydrogen gas into electrons and protons (hydrogen ions).
3.The protons are able to pass freely through the membrane—hence Proton Exchange Membrane…
4….while the electrons pass through an external circuit creating usable electricity.
5.After passing through the membrane the hydrogen protons with the help of a catalyst…
6….recombine with electrons and oxygen resulting in water vapor.