Solid Oxide Fuel Cell Interface Dynamics: Performance Degradation and Stabilization Study.

摘要

Solid oxide fuel cell (SOFC) technology has emerged as a potential alternative energy solution to the energy and environmental problems facing mankind. One key obstacle to widespread adoption of SOFCs as power generation systems is the high fabrication cost associated with their high operational temperatures. Materials with the perovskite crystal structure have been developed as cathode and electrolyte component materials, which allows for reducing the operational temperature without sacrificing the electrochemical performance. However, their long term stability under elevated operational temperatures has not been well understood.;In this study, the stability and degradation mechanisms of perovskite cathode/electrolyte interfaces were systematically investigated by correlating long term electrochemical performance change to the nano-scale structural and chemical evolution, assessed using advanced electron and X-ray characterization techniques. A significant increase in cathode polarization resistance was observed over the duration of testing, and the performance degradation was attributed to the formation of a less catalytic phase and a change in perovskite stoichiometry at the interface. The mechanisms underpinning the structural and chemical evolution revealed characteristics with strong diffusion related kinetics.;Based on the mechanistic understanding of factors that constitute interfacial instability, approaches to stabilize perovskite cathode/electrolyte interfaces were experimentally explored. One potential approach is to reduce cation mobility within cathode materials by using materials with an ordered, double perovskite structure; another approach is to minimize the cation diffusion driving force by tailoring the cation elements and doping levels within potential cathode materials; a third approach is to add a doped ceria diffusion barrier coating between the cathode and electrolyte layers. Exploratory studies with each approach are discussed.