TUNING THE STRUCTURE AND CHEMISTRY OF SOLID OXIDE FUEL CELL ELECTRODES FOR HIGH PERFORMANCE AND STABLE OPERATION

Abstract

Their reliability, fuel-flexibility, and high specific power make solid oxide fuel cells (SOFCs) promising next-generation power conversion devices. These advantages are theoretically attainable, but current material and structural limitations on the electrodes restrict the true potential of SOFCs on a cell level. Furthermore, ceramic processing challenges hinder the large-scale implementation of SOFCs. Here, SOFC electrodes are redesigned to develop the device closer to its theoretical potential. First, a fundamental investigation into the nature of exsolution materials provides a platform for controlling electrocatalyst properties such as: particle size, population, composition, and contact angle on host. Next, this knowledge is used to design a stable and active anode for the first ever exsolution-anode-supported SOFC and the practical limitations of this approach are identified to lead future research routes. In parallel to this study, a new method for synthesizing cheap, effective catalysts is developed to enable long-term SOFC operation with hydrocarbon fuel without sacrificing performance. Additionally, a systematic study identifies oxygen diffusion as the rate limiting step in the high current regime, and when this limitation is removed with improved system and electrode design, world-class power densities are achieved. Finally, a methodical investigation into ceramic processing of full-scale (5x5cm) SOFCs uncovers that cell flatness can be improved by optimizing green-tape compositions, sintering time/rate/temperatures, and top plate selection. Likewise, electrolyte quality depends on the top plate used in sintering and a light-weight YSZ-coated top plate gives the best balance between flatness and electrolyte quality.