ENGINEERING CATHODE ARCHITECTURES FOR SOLID OXIDE CELLS: PATHWAYS TO SUPERIOR ACTIVITY AND STABILITY

Abstract

Solid oxide fuel cells (SOFCs) are a promising technology for efficient energy conversion, but their performance at lower temperatures is often limited by sluggish oxygen reduction reactions and cathode polarization. This dissertation investigates the engineering of nano-electrocatalyst infiltrated cathodes to address these challenges, focusing on both material composition and electrode architecture. Traditional high-temperature cathode processing can lead to particle agglomeration and reduced active surface area, limiting catalytic activity. Here, we show that pure-phase electrocatalysts are not essential for long-term stability or high catalytic performance, enabling low-temperature processing of multiphase nano-catalysts. Using a solution infiltration method, Pr–Sr–Co (PSC) oxide and cobalt-free alternatives Pr–Sr–Ni (PSN) and Pr–Sr–Fe (PSF) oxide-based nano-electrocatalysts were deposited onto Pr and Sm doped mixed-conducting GDC scaffolds as cathode. Optimization of infiltration loading revealed that both insufficient and excessive loading can limit performance. Electrochemical testing demonstrated that cobalt-free PSN and PSF achieve low polarization and high-power output, with PSN showing comparable performance to cobalt-based PSC and excellent long-term stability. These results highlight the importance of optimizing infiltrated electrocatalysts and demonstrate the potential of PSN as a robust, cobalt-free cathode alternative for advanced SOFCs. Beyond material optimization, the influence of scaffold architecture was examined. Engineering a functionally gradient-porosity scaffold enhanced electrocatalyst distribution, reduced mass transport limitations, and lowered overall cathode polarization. Gradient scaffolds achieved higher open-circuit voltages, which is critical for reversible operation in electrolysis mode. This also increased power output compared to non-gradient structures while maintaining stable performance during long-term operation. Overall, this dissertation demonstrates that careful design of nano-catalyst composition, infiltration loading, and scaffold architecture can substantially improve the activity, stability, and overall performance of SOFC cathodes, providing a versatile strategy for the development of high-performance, stable solid oxide energy conversion devices.