Promotion of Oxygen Reduction by Exsolved Silver Nanoparticles on a Perovskite Scaffold for Low-Temperature Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) have potential to be the cleanest and most efficient electrochemical energy conversion devices with excellent fuel flexibility. To make SOFC systems more durable and economically competitive, however, the operation temperature must be significantly reduced, which depends sensitively on the development of highly active electrocatalysts for oxygen reduction reaction (ORR) at low temperatures. Here we report a novel silver nanoparticle-decorated perovskite oxide, prepared via a facile exsolution process from a Sr_0.95Ag_0.05Nb_0.1Co_0.9O_3-δ (SANC) perovskite precursor, as a highly active and robust ORR electrocatalyst for low-temperature SOFCs. The exsolved Sr_0.95Ag_0.05Nb_0.1Co_0.9O_3-δ (denoted as e-SANC) electrode is very active for ORR, achieving a very low area specific resistance (0.214 cm² at 500 °C). An anode-supported cell with the new heterostructured cathode demonstrates very high peak power density (1116 mW cm^-2 at 500 °C) and stable operation for 140 h at a current density of 625 mA cm^-2. The superior ORR activity and stability are attributed to the fast oxygen surface exchange kinetics and the firm adhesion of the Ag nanoparticles to the Sr_0.95Nb_0.1Co_0.9O_3δ (SNC0.95) support. Moreover, the e-SANC cathode displays improved tolerance to CO₂. These unique features make the new heterostructured material a highly promising cathode for low-temperature SOFCs.