Regulating the N-Coordination Structure of Fe-Fe Dual Sites as the Electrocatalyst for the O Reduction Reaction in Metal-Air Batteries.

Iron-nitrogen coordinated catalysts are regarded as efficient catalysts for the oxygen (O) reduction reaction (ORR), wherein the coordination environment of Fe sites is critical to the catalytic activity. Herein, we explored the effect of the nitrogen-coordination structure of dual-atomic Fe sites (i.e., Fe-N-C and Fe-N-C) on the performance of the ORR. The half-wave potential () of Fe-N-C is 0.880 V vs RHE, outperforming that of the tetracoordinate Fe-N-C (0.851 V) and commercial Pt/C (0.850 V) in alkaline electrolytes. The Fe-N-C-based zinc-air battery delivers a maximum power density of (258.6 mW/cm) and superior durability under 10 mA/cm. Theoretical calculations unveil that the moieties of Fe-N profits the d-electron rearrangement of the Fe sites. The electronic and geometrical structure of Fe-N promotes the O molecules adsorbed on the Fe site and reduces the dissociation energy barrier of O, benefiting fracture of O-O bonds and acceleration of the transformation of O to *OOH (the first step of the ORR process). Such exploration of modulating the local N-coordination environment of Fe dimers paves an in-depth insight to design and optimize dual-atomic catalysts.