Proton exchange membrane fuel cells (PEMs)

  Proton exchange membrane fuel cells (PEMs) were developed originally by General Electric in the 1960s for NASA's space explorations. Over the years, these fuel cells have been known under various names, such as ion exchange membrane, solid polymer electrolyte, proton exchange membrane, or simply, polymer electrolyte fuel cells. They use hydrogen as fuel, oxygen or air as oxidant, and a solid polymer membrane as electrolyte.

PEM fuel cells use a solid polymer as an electrolyte and porous carbon electrodes containing a platinum catalyst. The electrolyte layer acts as a one-way door, allowing either positive or negative ions to travel across, but not electrons. This forces electrons to travel through the external circuit (electric current). As operating temperatures are at a low temperature (approximate 80 degrees Celsius), PEM fuel cells are ideally suitable for devices that require quick start-ups such as vehicles, back-up power, and electronic devices. In a PEM fuel cell, hydrogen fuel is combined with oxygen from air to produce electrical energy. The conversion process is environmentally safe – only heat and water are emitted as by-products.

The core of the PEMFC design consists of a proton conducting membrane (the electrolyte), located between two platinum-impregnated porous electrodes. Teflon gaskets and current collectors are added to these components to complete a single fuel cell unit. The core of the fuel cell is usually less than a millimeter thick and is referred to as the membrane-electrode assembly (MEA). Depending on the mode of fabrication, MEA can include either the membrane along with the catalyst layers only, or the whole ensemble of the previously mentioned components plus the carbon electrodes

PEM fuel cells are usually stacked when they are used in vehicles. That means a number of identical fuel cells are put together to provide a significant amount of energy. The more fuel cells that are put together, the more voltage created. The number of fuel cells stacked in each vehicle varies by the amount of power needed.

There are numerous applications for fuel cells. Think of cases where batteries can't meet mounting demands of personal electronics, or where continuous fuel cell power would be advantageous. Wherever you need power, a fuel cell could be the solution.

Fuel cell vehicles are electric, similar to battery vehicles. Gaseous hydrogen is pumped into a tank in the car, similar to gasoline. The hydrogen is then fed into the fuel cell where it is electrochemically converted into electricity. There is no combustion and no emissions other than water vapour. The electricity generated is used to power the vehicle. A fuel cell is also 2-3 times more energy efficient than a gasoline engine

  Proton exchange membrane fuel cells (PEMs) copyright 2011