The two electrodes, cathode and anode, are separated by a polymer electrolyte membrane which permits protons to cross to reach the cathode while the electrons are made to flow as part of a circuit to carry an electrical current.

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In this, the electrolyte is a polymer membrane coated with platinum, a metal that acts as a catalyst for the chemistry involved.

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This 100-nanometer membrane, comprising the electrolyte and electrodes, has to be thin enough to allow ions to pass through it at a relatively low temperature (which, for ceramic fuel cells, lies in the range of 300 to 500 degrees Celsius).

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