Breaking the O₂ Activation Bottleneck via Synergistic Electronic Polarization at Adjacent Co–Mn Sites in N-Doped Carbon

Metal-nitrogen-carbon (M-N-C) catalysts with atomically dispersed metal sites have emerged as attractive non-precious alternatives to Pt/C for the oxygen reduction reaction (ORR). Among them, Co-N-C systems have received particular attention because of their favorable stability and low cost, yet isolated Co sites often exhibit insufficient O₂ adsorption and charge polarization, limiting further activity enhancement. In this study, we introduce Mn into a Co-N-C matrix via a confined adsorption approach to create adjacent Co–Mn sites. The presence of adjacent Mn electronically modulates the Co center, resulting in a CoMnNC catalyst with markedly improved ORR performance. The catalyst delivers half-wave potential (E_1/2) values of 0.80 V in 0.1 M HClO₄ and 0.919 V in 0.1 M KOH. Under Zn-air battery testing, its maximum power density reached 193.5 mW cm⁻², outperforming Pt/C under identical conditions. Density functional theory (DFT) calculations indicate Mn proximity enriches the electron density at Co and downshifts the Co d-band center. This electronic modulation enhances O₂ adsorption and charge polarization, weakens the adsorbed O─O bond and lowers the barrier for OOH* formation. This work clarifies how neighboring metal sites regulate the electronic structure of Co centers to facilitate O₂ activation and offers a reference for designing excellent M-N-C catalysts.