Single Co Atoms Implanted into N-Doped Hollow Carbon Nanoshells with Non-Planar Co-N₄-1-O₂ Sites for Efficient Oxygen...

Facile synthesis of cost-effective carbon-supported Co single atoms (Co-SAs) exhibits huge potential applications in energy storage and conversion devices. We here report the implantation of Co-SAs into hollow carbon spheres (Co-SAs-HCS) via a facile wet-chemistry strategy followed by controlled pyrolysis. Electron-rich histidine acted as a Lewis base effectively immobilizing Co²⁺ (Lewis acid) via the electrostatic effect and hydrogen bonds, thus achieving the scalable synthesis of Co-SAs-HCS. We constructed a series of histidine-Co²⁺ structure models to elucidate the formation of histidine-Co²⁺ complexes by analyzing their binding energy. X-ray absorption fine-structure results verify that central Co atoms with four N coordination atoms possess a non-planar Co-N₄ structure. Electrochemical results indicate that the as-prepared Co-SAs-HCS catalyst shows a low potential difference (0.809 V) between the oxygen evolution reaction potential at 10 mA cm^-2 and the oxygen reduction reaction half-wave potential, outperforming the commercial Pt/C catalysts (0.996 V). Moreover, an assembled Zn-air battery based on Co-SAs-HCS exhibits an unexpected long-term durability. We have demonstrated that non-planar Co-N₄-1-O₂ sites are the source for highly efficient adsorption and dissociation of O₂ molecules and then reduction of the free energy of desorption of the intermediates by density functional theory. Our findings provide a new design insight into the exploration of advanced electrocatalysts, which will be applied in the design of green energy devices in the future.