The most common batteries are made up of negative and positive halves (the anode and the cathode), a material to separate them, and "current collector" layers at top and bottom to gather up the electric charges moving through.

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There are several sorts of fuel cell, but all consist of two electrodes (an anode and a cathode) separated by a material called an electrolyte.

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We know very well what is the best material to use as the cathode in those fuel cells.

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