SOFC Cathode Materials and Performance

The oxygen anions created are selectively transferred through the oxygen-permeable membrane to the anode, where they experience a similar half-cell reaction with a gaseous fuel, either H2, syngas (CO + Hj), or a hydrocarbon, to produce H20 and C02. For example, if the fuel is CH4, the oxidation reaction in the anode is given by 

During this process, the electrons released and consumed at the anode and cathode produce some fraction of the reversible work of the reaction to the external circuit. 

In conclusion, the ideal cathode should be porous, electronically and ionically conducting, elec-trochemically active, and possess high surface areas. Given this, it is unusual for a single material to accomplish all of these functions, so a composite cathode, of which the electrocatalyst is one component, is often used [135], 

Transition-metal oxides were first studied as SOFC cathodes owing to their excellent electrical conductivity, and as a comparatively inexpensive option to Pt, which during the 1960s was the 

FIGURE 8.24 Electrode-electrolyte and the three-phase boundary. 

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