First‐Principles Investigations on Effects of B‐Site Substitution (B═Mn, Fe, and Co) on La‐Based Perovskite Oxides As Bifunctional Electrocatalysts for Rechargeable Metal–Air Batteries

Abstract The effects of B‐site substitution (B═Mn, Fe, and Co) in La‐based perovskite oxides (LPOs); LaMnO 3 , LaFeO 3 , LaCoO 3 , as bifunctional electrocatalysts during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in metal–air batteries (MABs) under an alkaline electrolyte (pH = 13) are investigated using density functional theory (DFT). It is found that LaMnO 3 exhibits higher ORR activity than others with ORR overpotential ( η ORR ) of 0.57 V, but its OER activity is poor with OER overpotential ( η OER ) of 1.12 V. The η ORR (0.59 V) and η OER (1.13 V) of LaMn 0.75 Fe 0.25 O 3 closely resemble those of LaMnO 3 , suggesting that Fe substitution does not yield appreciable enhancements in activity. Fe substitution reduces the ORR and OER activity because the adsorption energies of intermediate species on Fe‐substituted LPOs surfaces are too strong to obtain a potential determining step for ORR and OER. According to Sabatier's principle, the LaMn 0.25 Co 0.75 O 3 demonstrates superior OER activity compared to the other composition, while ORR activity approximates that of LaMnO 3 , evidenced by η ORR of 0.65 V and η OER of 0.53 V. The Co‐terminated LaMn 0.25 Co 0.75 O 3 shows bifunctional activity higher than Mn/Co termination, indicating that Co is an active site for OER and Mn is a promoter for improved ORR activity.