**1.4.2 Cathode**

The cathode of a fuel cell is the interface between air (or oxygen) and the electrolyte. Its main functions are to catalyze the reaction of oxygen reduction and to transport the generated electrons to the interconnect (external circuit).

In the same way of all the materials used in solid oxide fuel cells, the cathode must present certain general characteristics:


The materials, perovskite-type ABO3, commonly used as cathodes in fuel cells are solid oxide ceramics based on lanthanum manganite (LaMnO3) substituting A for Sr ions. This material fills most of the requirements for its use as cathode for ceramic fuel cells operating at temperatures around 1000 °C. The ionic conductivity of materials based on LaMnO3 is significantly smaller than the ionic conductivity of YSZ electrolytes, but the ionic conductivity increases significantly substituting Mn for Co. The diffusion coefficients of oxygen ions in lanthanum cobaltite can reach 4-6 orders of magnitude higher when compared to those of lanthanum manganites with similar doping (Carter, 1992). Other materials have been used as cathode in SOFC, such as: Lanthanum strontium ferrite (LSF), (LaSr)(Fe)O3, Lanthanum strontium cobaltite (LSC), (LaSr)CoO3, Lanthanum strontium cobaltite ferrite (LSCF), (LaSr)(CoFe)O3, Lanthanum strontium manganite ferrite (LSMF), (LaSr)(MnFe)O3, Samarium strontium cobaltite (SSC), (SmSr)CoO3, Lanthanum calcium cobaltite ferrite (LCCF), (LaCa)(CoFe)O3, Praseodymium strontium manganite (PSM), (PrSr)MnO3, Praseodymium strontium manganite ferrite (PSMF), (PrSr)(MnFe)O3 (Stambouli & Traversa, 2002b).
