Kinetic Atomic-Scale Reproducibility of the Oxygen Reduction Reaction Process and a Newly Suggested Strong Correlation Descriptor: A Case Study of BaCo0.75Fe0.25O3-δ.

ABSTRACT

The sluggish oxygen reduction reaction (ORR) is a central issue for energy conversion technologies, particularly in the cathodes of solid oxide fuel cells. The recognition of atomic-level kinetics of the ORR is the key solution. Herein, we take BaCo0.75Fe0.25O3 (BCF) perovskite cathode as a model to investigate the ambiguous ORR mechanism by density function theory and ab initio molecular dynamics. The oxygen dissociation process was found as the rate-determining step, and the performance of BCF series perovskite could be well-characterized by the dissociation barrier energy. Further electronic structure analysis demonstrated that the Pr (Nd)-Odis bond accepted electrons during the oxygen dissociation process, resulting in reduction of the barrier energy. Finally, strong correlations between rare earth 4f electrons and B-site transition metal 3d electrons were found to be another underlying descriptor to determine the electrochemical activity. We expected that the method could be universally applied to design or screen other high-performance perovskite cathodes.