High-performance composite Bi2Ru2O7-Bi1.6Er0.4O3 cathodes for intermediate-temperature solid oxide fuel cells

Porous composite electrodes consisting of Bi2Ru2O7 (BRO7) and Er0.4Bi1.6O3 (ESB20) were synthesized and characterized using impedance spectroscopy on symmetrical cells. Electrode performance was manipulated compositionally by varying the weight percent of each phase in the composite. Microstructural influences on electrode resistance were examined by varying starting particle sizes of BRO7 and ESB20 powders and using a combination of sedimentation to further reduce particle size and size distributions as well as ultrasonication to break up soft agglomerates. The effect of electrode thickness was also studied by applying successive coats of the electrode inks to the electrolyte substrates. In addition, application of a pure BRO7 current collector was found to dramatically improve performance. Using these optimization techniques, a minimum electrode area specific resistance of 0.03 Omega cm(2) was attained at 700 degrees C. (c) 2007 The Electrochemical Society.