A-site Excessive (La_0.8Sr_0.2)_1+<i>x</i>MnO₃ Perovskite Oxides for Bifunctional Oxygen Catalyst in Alkaline Media

Abstract

Nominal A-site excessive (La0.8Sr0.2)1+xMnO3 (x = 0, 0.05, and 0.1) (denoted as LSM, LS1.05M, and LS1.1M) perovskite oxides have been synthesized by the polymer-assisted chemical solution (PACS) method for bifunctional oxygen electrocatalysis, including both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) applications in alkaline media. LS1.05M exhibits 21% higher diffusion-controlled ORR current density, 87% higher OER current density at 0.8 V (vs Ag/AgCl 3.5 M), and ultralow electrochemical impedance compared to pristine LSM. LS1.1M has mixed performance relative to LSM due to structure instability. First-principles study by density functional theory (DFT) suggests that the free energy decrease from O* to *OOH is the rate-limiting step in OER. Transition metal d-band center and oxygen p-band center approaching the Fermi level are responsible for the enhanced electrochemical activity.