Effect of cationic species on the oxygen reduction reaction (ORR) activity of perovskite transition metal oxides in the alkaline environment: Elucidating the charge transfer mechanism on model oxide surfaces

The requirement for an efficient, inexpensive electrocatalysts for the ORR in hydrogen fuel cells represents one of the biggest scientific challenges for enabling hydrogen-based energy storage. Perovskite oxide (ABO₃ formula, where A is La, and B is a 3d transition metal) is one of the most promising materials with high catalytic activities, rivaling that of the state-of-the-art platinum in the alkaline environment. Recent work on the ORR activity of Pt catalyst in alkaline electrolytes with various cations such as Li⁺, Na⁺, K⁺ shows that the cations can interfere with the catalytic activity by bonding non € covalently to the surface oxide group(s), where it is hypothesized that the smallest cation, Li⁺ could strongly interact with the surface oxide and therefore reduce the ORR activity on Pt. In this study, we examine the effect of cations on ORR activity of LaMnO_3+δ and LaNiO₃ perovskite oxides in alkaline electrolytes (MOH, where M = Li, Na, K) using rotating disk electrode measurements, and compare with the cation effect reported previously on Pt.