Ex‐Solved Ag Nanocatalysts on a Sr‐Free Parent Scaffold Authorize a Highly Efficient Route of Oxygen Reduction

Abstract The electrocatalytic value of nanoparticles has attracted substantial attention in relation to energy conversion devices, including solid oxide fuel cells. Among various forms of analogs, ex‐solved metal nanoparticles originating from their parent oxides display strong particle‐substrate interactions and thus have the benefits of extended durability and of course enhanced catalytic activity. Inspired by recent advances, here, novel air‐electrode materials based on BaCoO 3–δ perovskites decorated with socketed Ag nanoparticles are presented. Doping with niobium (Nb 5+ ) and tantalum (Ta 5+ ) can significantly promote the stability of the cubic perovskite phase. The developed oxides exhibit promising performance outcomes in the highly prized low‐to‐intermediate temperature regimes (450–650 °C). Moreover, the exclusion of Ag particles further activates the parent scaffold, thereby conveying record‐level area‐specific resistance (e.g., ≈0.02 Ω cm 2 at 650 °C). Coupled with the unique nanoarchitecture, the newly designed cathode showcases in this study hold great promise for future air‐electrodes in fuel cells.