Fuel cells are devices which electrochemically convert the chemical free energy of gaseous or liquid reactants into electrical energy in a continuous way. As in a battery the reactants are prevented from chemically reacting by separating them with an electrolyte, which is in contact with electro-catalytically active porous electrode structures. Apart from effectively separating the anode and cathode gases and/or liquids, in other words the fuel and air, the electrolyte mediates the electrochemical reactions taking place at the electrodes by conducting a specific ion at very high rates during the operation of the fuel cell. In the simplest case of a fuel cell, operating with hydrogen (fuel) and oxygen (air) as reacting gases, a proton or oxide ion current equivalent to the electronic current passing through the external load is driven through the electrolyte and parts of the heterogeneous electrode structures (Fig.1.1).
KeywordsCombustion Entropy Methane Enthalpy Platinum
I thank Giuliano Gregori and Linas Vilciauskas (both from Max-Planck-Institut für Festkörperforschung) for reading the proofs.
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