Unraveling the mechanism of K-doping on the enhancement of oxygen reduction reaction activity in LaMnO3 perovskite for Zinc-Air batteries

LaMnO 3 -based perovskites are considered as one of the most promising oxygen reduction reaction (ORR) catalysts to replace noble metals due to their excellent controllability and stability. A central strategy to enhance their electrocatalytic performance involves A-site doping. While divalent cation doping (e.g., Sr 2 + , Ca 2+ ) has been extensively explored, the mechanistic understanding of how lower-valence monovalent cations modulate the electronic structure and enhance ORR activity remains insufficient. This study systematically investigates the effect of monovalent potassium (K⁺) doping in La 1-x K x MnO 3-δ (LKM) as a model system to unravel the underlying enhancement mechanism. Among the series, La 0.8 K 0.2 MnO 3-δ (LKM20) demonstrates improved ORR activity with an onset potential of 0.924 V and a half-wave potential of 0.750 V (vs. RHE). The enhanced activity of LKM20 is attributed to: 1) K-induced tuning of the Mn 4+ /Mn 3+ ratio nearing 1.24; 2) Regulating oxygen vacancy concentration and optimizing intermediate adsorption performance; and 3) Reinforced Mn-O covalent bonding. Density Functional Theory calculations reveal that the introduction of K effectively reduces the energy barrier for the ORR. In the zinc-air battery, LKM20 exhibits a maximum power density of 122.5 mW cm −2 and maintains stable operation over 1800 h during charge-discharge cycles.