Morphology evolution and exsolution mechanism of a partially decomposed anode for intermediate temperature-solid oxide fuel cells

Abstract

To develop new anode material for intermediate temperature-solid oxide fuel cells (IT-SOFCs), layered perovskite PrBaFe1.75Nb0.25O5+δ (PBFNO) is synthesized and evaluated. PBFNO is partially decomposed in wet H2 to form a composite including Fe, Pr2O3, PrBa2NbxFe1-xO6-δ and survival PBFNO. PBFNO anode not only exhibits good electrochemical performance, but also can keep activating during long-term operation which contributed by decomposition continuously. Numerous nanoparticles are exsolved upon the initial short-term reduction, but they are agglomerated severely after the subsequent long-term annealing. Therefore, exsolution mechanisms for stable parent perovskites and partially decomposed perovskites are investigated, and the difference mainly lies in their metal-oxide interfaces with different strengths. Finally, morphology evolutions of the partially decomposed PBFNO anode under electrochemical conversion and chemical reduction are compared to demonstrate that electrochemical conversion can accelerate the agglomeration of PBFNO anode. This work provides insights into morphology evolution and exsolution mechanism of partially decomposed perovskite anode for IT-SOFCs.