Enhanced Oxygen Reduction Reaction in Nanocrystalline Surface of Samaria-Doped Ceria via Randomly Distributed Dopants

Abstract

The randomly distributed dopant effects in nanocrystalline samaria-doped ceria (SDC) interlayers were investigated by systematically varying the dopant distributions and grain-boundary densities via post-annealing process. Electrochemical analysis demonstrates that films having lower annealing or fabrication temperatures exhibit superior surface oxygen kinetics, particularly in the case of oxygen reduction reactions (ORRs). Further investigation through TEM-EELS shows that the typical segregation of dopants is not significantly present in SDC film deposited via the RF sputtering method, while post-annealed SDC film shows strong dopant accumulation near the grain boundary. The results indicate that the randomly distributed dopants, in addition to the nano grains, may further enhance surface reactions by providing more preferential reaction sites due to a higher content of defects at the interface.