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What Are Fuel Cells
Fuel cells use gases to generate electricity directly from a chemical reaction. Unlike batteries they do not need recharging but run indefinitely as long as they are supplied with fuel. The fuel of choice is hydrogen.

The problem with early Fuel cells was the liquid electrolyte used, and the expensive catalysts required at both positive and negative electrodes.

Modern developments include the use of a very thin polymer membrane which transports protons. It is made from a polymer based on poly(tetrafluoroethene) with acid groups attached to make it capable of proton transport.

Anode reaction
H2 2H++ 2e-

Cathode reaction
½O2 +
2H+ + 2e- H2O

Overall reaction
H2 +½O2 H2O

Individual cells are assembled into stacks, capable of giving the desired voltages and currents.








































The catalyst used is still the very expensive platinum, but now in extremely finely divided form on a carbon support with a very high surface area, with as little as 0.1 mg of platinum per cm2.The whole membrane electrode assembly can be less than 1 mm thick. The process is animated in the diagram below - click on the image to start..