Ni-Based Cathodes for Low Temperature Solid Oxide Fuel Cells

Abstract

Cathodes are made with mixed ionic and electronic conductors (MIECS) to extend the triple phase boundary (TPB) for oxygen reduction. Specifically, we are investigating La 2 NiO 4 , an analogue of K 2 NiF 4 . These perovskite-related oxides exhibit useful properties, including a thermal expansion coefficient of 13.6×10 -6 K, which is close to that of yttria-stabilized zirconia (YSZ), thereby minimizing stresses at the YSZ/cathode interface. In addition, the oxygen diffusivity (D*) and surface exchange coefficients (k) of La 2 NiO 4 , which are indicative of high ionic conduction and good electrocatalytic properties, are comparable to or higher than those of La 1-x Sr x CoO 3-δ and La 0.6 Sr 0.4 Co x Fe 1-x O 3 . These attributes can enhance the performance of cathode material by extending the number of possible pathways for the oxygen reduction reaction.