Dynamic Spin Governing Asymmetric Coordination Fields in Trimetallic Single-Atom Catalysts for Optimal Oxygen Reduction

Abstract

Single-atom catalysts demonstrate theoretically superior oxygen reduction reaction (ORR) kinetics, the limited dynamic adaptability, however, poses a giant challenge to meet the multi-step proton-coupled electron transfer (PCET). Herein, we propose a "Dynamic Spin Engineering" strategy for the rational design of tri-metallic single-atom catalysts (FeZnTM-TACs) featuring asymmetric coordination fields (FeN₄ZnN₃TMN₄). Leveraging electron synergy and spatial functional decoupling among heterometallic sites, the optimized FeZnMn-TACs exhibit exceptional ORR performance (E_1/2 = 0.93 V versus RHE) and ultra-long stability (ΔE_1/2 = 24 mV after 90,000 cycles). Through operando X-ray absorption fine structure and spin-polarized density functional theory, we unveil the scalability of a ternary synergy encompassing dynamic reconstruction, charge compensation and spin-state transition, clarifying the roles of electron donors at the ZnN₃ sites and proton supply at MnN₄ sites. Dynamic FeN_xC_y evolution triggers a spin-state transition from medium spin (MS = 1.5) to low spin (LS = 1.0), accompanied by the d_xz/d_yz orbital occupancy degree from 50% to 100%. As a consequence, we synergize the dual optimization of *OOH formation and *OH desorption in PCET. Moreover, our work atomically deciphers the spin redistribution mechanism driven by dynamic reconstruction, establishing a new paradigm for designing self-adaptive electrocatalysts that ultimately unify ultrahigh activity with operational stability.

Keywords: Asymmetric coordination fields; Dynamic reconstruction; Proton–coupled electron transfer; Spin redistribution; d‐orbital occupancy.