Tuning electrocatalytic activity via Mn doping in Ca2Fe2O5 for OER and ORR applications

Abstract

In this study, we report Mn-substituted Ca₂Fe₂O₅ brownmillerite oxides as efficient electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. The incorporation of Mn into the Ca₂Fe₂O₅ lattice significantly modulates the electronic structure and enhances charge transport, resulting in improved catalytic performance. Among the series of Mn-doped Ca₂Fe₂O₅ oxides, Ca₂Fe_1.5Mn_0.5O₅ exhibited the highest activity, delivering a high OER current density of 190 mA cm⁻² at 2.0 V vs. RHE, comparable OER overpotential of 0.39 V and higher intrinsic activity than IrO₂. For the ORR, the same composition follows a favorable four-electron pathway with low generation of H₂O₂ and depicting excellent durability. Post-electrocatalytic XRD and SEM analyses confirmed strong structural integrity with a minimal amount of surface amorphization and morphological stability. These findings highlight Mn-substituted brownmillerite oxides as promising, cost-effective, and earth-abundant bifunctional electrocatalysts for alkaline oxygen electrocatalysis in energy conversion applications.