Effective Promotion of Oxygen Reduction Reaction by in Situ Formation of Nanostructured Catalyst

Efficient electrocatalysts for oxygen reduction reaction (ORR) are critical to high-performance energy conversion and storage devices. As an important family of functional materials, alkaline earth metal oxides are generally considered inert toward electrochemical reactions. Here we report the remarkable enhancement of ORR activity and durability of electrodes enabled by surface modification with a precursor of barium nitrate. During cell start-up process, an ORR active cobaltite catalyst was in situ formed on the electrode surface, as confirmed by scanning transmission electron microscopy (STEM) analysis. A combination of in situ/operando Raman and electrochemical impedance study suggests that the transition from nitrate to cobaltite may occur at ∼565 °C. The peak power density of a single cell at 750 °C is increased from ∼0.85 to ∼1.15 W cm–2 (35% increase) by the surface modification, demonstrating the remarkable enhancement of electrocatalytic activity under realistic operating conditions.