Breaking the Ion Ordering in the Perovskite Anode for Enhanced High-Temperature Oxygen Evolution Reaction Activity

Ion ordering in the perovskite oxide plays a crucial role in governing the properties, such as magnetic behavior, electronic and ionic conductivity, and dielectric or ferroelectric characteristics. As the common anodes in solid oxide electrolysis cells (SOECs), perovskites exhibit remarkable high-temperature oxygen evolution reaction (OER) activity. However, the influence of ion ordering in the perovskite anode on the OER activity remains poorly understood. In this study, we demonstrate that the A-site ion in Pr_xBa_2-xCo₂O_5+δ perovskites transforms from ordered to disordered as the Pr content increases from 1.0 to 1.5. Comprehensive characterizations and density functional theory calculations reveal that this order-disorder transition significantly enhances d-p orbital hybridization, thereby enhancing the rates of oxygen exchange and oxygen ion transport. Electrochemically, the disordered Pr_1.5Ba_0.5Co₂O_5+δ anode exhibits notably reduced ohmic and polarization resistances, achieving superior OER performance with a current density of 2.29 A cm^-2 at 1.6 V and 800 °C. This work highlights the critical role of ion ordering in the OER performance and offers new insights into the design of efficient SOEC anode materials.