High-throughput Characterization of Solid Oxide Fuel Cell Cathode Materials

Abstract

Solid oxide fuel cells are electrochemical devices which convert chemical energy directly to electricity. The extreme environments in which these devices operate require the use of expensive components to withstand degradation. To lower operating temperatures and therefore cost, materials discovery efforts have targeted new electrodes with high ionic and electronic conductivity, but these studies often convolute electrode morphology and performance, masking the inherent activity of electrode materials. In this work, a high-throughput experimental technique utilizing a robotic scanning impedance probe is applied to materials libraries to rigorously compare the performance of electrode materials and characterize fundamental electrode properties. Two cathode materials libraries are studied in-depth: the perovskite material La1-xSrxCo1-yFeyO3-δ (LSCF) and the double perovskite material PrBa0.5Sr0.5Co2-xFexO5+δ (PBSCF). Each materials library is investigated through the entire regime of cobalt and iron doping and results are obtained on both oxide-ion- and proton-conducting electrolyte materials. For LSCF, a four-fold increase in electrochemical resistance is observed from the cobalt-dominant endmember LSC64 to the iron-dominant endmember LSF64 on an oxygen-ion conducting substrate, concurrent with a decrease in chemical capacitance indicating lower oxygen vacancy concentration. For PBSCF, proton conductivity is observed through the bulk of the film, leading to its use in a real proton-conducting ceramic fuel cell that demonstrates exceptional performance at low temperatures (> 500mW/cm2 at 500°C) while remaining stable over hundreds of hours of testing. These results demonstrate the power and robustness of this high-throughput approach in characterizing both well-known and novel materials, and show great promise for future targeted searches of high-performance materials.