Thin film microelectrodes in SOFC electrode research

Experimental studies using conventional (porous) solid oxide fuel cell (SOFC) electrodes are often rather difficult to interpret in terms of a mechanistic understanding of the electrochemical polarization phenomena. Owing to the complex morphology and structure of porous electrodes, a quantitative determination of the properties of the electrochemical materials rather than of the effective electrode properties is far from being straightforward. Micro-patterned epitaxially grown thin film electrodes offer new possibilities in this field of research. This is particularly true for microelectrodes of several 10 mu m diameter, fabricated lithographically from thin films. They allow well-defined geometry-dependent experiments, minimize the importance of ohmic drops, and avoid the necessity of a reference electrode. Further, they turn out to be particularly well-suited for statistical studies, as well as for the investigation of irreversible processes. Hence, thin-film microelectrodes are an excellent tool for the investigation of SOFC electrode materials. This is exemplified by p(O-2)-, voltage-, and geometry-dependent measurements on (La0.8Sr0.2)(0.92)MnO3 and La0.6Sr0.4Co0.8Fe0.2O3-delta microelectrodes on single-crystal yttria-stabilized zirconia electrolytes.