Surface Modifications of Nano-structured Cathodes to Enhance Durability of Intermediate Temperature Solid Oxide Fuel Cells

摘要

The bulk-to-surface Sr-segregation can seriously compromise the stability of oxygen electrocatalysis in Sr-doped perovskite oxides such as La_(1-x)Sr_xCoO_(3-δ) and La_(1-x)Sr_xCo_(1-y)Fe_yO_(3-δ) and limit their practical applications as cathode materials in solid oxide fuel cells. This work aims to acquire fundamental knowledge of Sr-segregation process under practical conditions in solid oxide fuel cells and develop suppression method to ensure the long-term stability through surface modifications. In this work, the pristine and ZrO_2 atomic layer deposition (ALD) modified La_(0.6)Sr_(0.4)CoO_(3-δ) (LSCo) epitaxial films were used as the model systems to investigate how the temperature, time and surface coating affect the surface concentration of Sr via in situ synchrotron-based ambient pressure XPS. This information was also correlated with their electrochemical performances characterized by electrochemical impedance spectroscopy. We also report a Sr-segregation-free SrCo_(0.9)Ta_(0.1)O_(3-δ) (SCT) multifunctional coating on a benchmark cathode LSCF as a means of enhancing ORR activity and durability against Cr-poison.