Spin-State Manipulation of Atomic Manganese Center by Phosphide-Support Interactions for Enhanced Oxygen Reduction.

Oxygen reduction reaction (ORR) kinetics are closely related to the electronic structure of active sites. Herein, a single-atomic Mn catalyst decorated with adjacent MoP nanocrystals (MoP@Mn-NC) is reported. The decoration of MoP drives the electronic structure transition of Mn sites from low-spin to high-spin states through an electronic phosphide-support interaction. The rearranged electron occupation in 3d and 3d orbitals of Mn sites leads to electrons occupying the σ orbital in Mn─*O, thereby favoring O adsorption to initiate the ORR mechanism. In situ characterizations confirm that Mn 3d orbital occupation state can activate molecular O₂ and optimize the adsorption of the *OOH intermediate. As a result, the MoP@Mn-NC displays an outstanding alkaline ORR half-wave potential (E = 0.894 V), excellent peak power densities (173/83 mW cm for liquid/solid-state Zn-air batteries, respectively), and long-term stability (840 h) superior to commercial Pt/C. This work provides profound insights into spintronics-level engineering, guiding the design of next-generation high-performance ORR catalysts.