Exploration of a Ce0.65Zr0.25Pr0.1O2-d-Based Electrocatalyst That Exhibits Rapid Performance Deterioration Despite Its High Oxygen Storage Capability

Abstract

Ceria-zirconia solid solution, having superior oxygen storage/release capability and carbon coking resistance, has long been used as a favorable catalyst or supporting material for various catalytic converters and membrane reactors. Recently, rare-earth-doped ceria-zirconia with an additional improvement in its ionic conductivity by doping is attracting attention as a promising electrocatalyst for solid oxide fuel cells (SOFCs). However, despite this promising prospect, the practical usefulness for fuel cell catalysts has not been verified yet. According to our electro-chemical analysis on a Pr-doped CZO (PrCZO)-based anode, the electrochemical performance does not remain stable; instead, the performance rapidly deteriorates over time even though it is initially much better than that of a conventional anode. From the thorough investigations to identify the cause of the rapid deterioration of PrCZO-based anode via computational analyses using density functional theory and defect chemical analysis, it can be concluded that the fast degradation of PrCZO-based anode is mainly due to the inactive substances precipitated on the PrCZO surface caused by the inherent thermodynamic instability and enhanced phase separation kinetics under SOFC operating conditions, where more mobile cationic defects (interstitial cations) are generated and an easier pathway with a lower migration energy is available.