Composite Cathodes for Intermediate Temperature SOFCs

Solid Oxide Fuel Cells (SOFCs) have enormous potential to efficiently and cleanly produce heat and electricity. To fully tap this potential, we must first fully understand and engineer the catalytic properties of composite cathodes for lower temperature SOFCs, which have emerged as a critical parameter of cell performance Phenomenologically, it has been demonstrated that the key variables that can be modified to dramatically improve SOFC performance include: (1) the microstructure of the cathode, (2) the volume of the electronically or mixed ionic electronic conducting phase, (3) the overall porosity, and (4) the geometry of the composite cathode. However, a better understanding is needed of the nature of the chemisorption phenomena on the cathode surfaces as well as electrocatalytic pathways coupling electrons- and oxygen-transfer processes.

This research is expected to produce fundamental knowledge and understanding of the interrelationships between cathode composition and geometry, processing parameters, and catalytic performance of the composite cathodes under the real SOFC operational conditions. The catalytically active cathode surfaces will be probed by in-situ Raman and impedance spectroscopy. To accomplish the research objectives, we will (1) investigate dioxygen species adsorbed on a composite cathode surface, (2) study the dynamics of the surface restructuring and oxidation during the temperature programmed experiments, and (3) explore the reactivity of the surface dioxygen species toward the oxygen partial pressure and as a function of the phase composition of the cathode materials. We will also study the structural information as to the extent and nature of oxygen species adsorbed on the cathode surface as well as the vibrational properties of the cathode materials as a function of temperature, overpotential, and oxygen partial pressure. As a result of the proposed research, we will achieve a significant contribution to expanding knowledge and development of an innovative approach for in-situ Raman and impedance spectroscopy to characterize vibrational properties and oxygen mobility and reduction mechanisms on electrochemically active composite cathode surfaces.

B1.3: Composite Cathodes for Intermediate Temperature SOFCs: A Comprehensive Approach to Designing Materials for Superior Functionality