Enhancing Oxygen Redox Reversibility in Li–O ₂ Batteries via Bimetallic Phosphide Catalysts with Tailored Surface Morphology and Electronic Structure

In this study, a manganese-cobalt-based bimetallic phosphide (MCP) catalyst is developed to address two major challenges of lithium-oxygen (Li-O₂) batteries: high overpotential and limited cycling stability. By systematically tuning the Mn: Co ratio, the optimized MCP12 catalyst exhibits the highest electrochemical activity, which is attributed to its increased surface area, enhanced electrical conductivity, and modulated adsorption affinity for oxygen intermediates. Particularly, the incorporation of Mn induces structural distortions and defect formation, resulting in a significant increase in the electrochemically active surface area, as validated via Brunauer-Emmett-Teller surface analysis and electrochemical double-layer capacitance measurements. Furthermore, X-ray photoelectron and electrochemical impedance spectroscopies reveal that electronic structure rearrangements contribute to improved charge-transfer properties. Consequently, the MCP12-based air electrode achieves a high discharge capacity of 6.33 mA cm^-2, a prolonged cycle life of 211 cycles, and a substantially reduced overpotential. Density functional theory calculations demonstrate that Mn incorporation upshifts the d-band center and increases the density of states near the Fermi level, thereby enhancing the adsorption of oxygen intermediates and facilitating charge transfer. This study highlights the synergistic effect of bimetallic phosphide catalysts and provides a promising strategy for developing high-performance electrocatalysts for next-generation Li-O₂ batteries.