From Cucurbit[7]Uril Armor-Equipped Ferrocene to Nitrogen Self-Doped Porous Carbon Hosting Fe Single Atoms and Atomic Clusters for ORR and Zinc-Air Batteries.

Achieving both high activity and metal loading of atomically dispersed metal sites in M─N─C catalysts remain a formidable challenge. Herein, we employ the macrocyclic supramolecule cucurbit[7]uril (CB[7]) as a nanocage precursor and ferrocene (Fc) as a metal source, respectively. Through spontaneous host-guest self-assembly, an angstrom-level space-confined precursor (Fc@CB[7]) was constructed, providing a well-defined molecular scaffold for oxygen electrocatalysts. The resulting Fc@CB[7] complex exhibits a cage-with-lid geometry, endowing it with the structural characteristics of a metal monatomic precursor. Upon coating the Fc@CB[7] complex with ternary eutectic salts (NaCl, KCl, ZnCl2, named TESs) and subjecting it to pyrolysis, we obtained a novel oxygen electrocatalyst, denoted FeAC─FeSA/N─CBC0.7, featuring coexisting Fe atomic clusters and Fe single atoms. The deliberately designed FeAC─FeSA/N─CBC0.7 catalyst delivers a remarkable half-wave potential (E1/2) of 0.915 V and outstanding Zn-air battery (ZAB) performance. Density functional theory (DFT) calculations identify the presence of Fe7 clusters that modulate the local electronic configuration of Fe─N4 sites and weaken *OH adsorption, thereby accelerating the oxygen reduction reaction (ORR) kinetics. This work not only paves a way between supramolecular chemistry and electrochemistry but also provides fundamental insights into the structure-activity relationship of FeAC─FeSA/N─CBC0.7 for ORR.