Interfacial Oxidation Nanoarchitectonics of Water-Soluble C₆₀ Towards High-Performance Fe-N-C Electrocatalysts

The chemical modification and self-assembly capability of fullerenes offer advantageous conditions for tailoring Fe/N-doped carbon-based catalysts. However, their strong π-π stacking tendency may partially restrict metal loading and the generation of active Fe species. Therefore, how to utilize the distinctive features of fullerenes to precisely regulate and optimize Fe-N active sites along with their local coordination environment remains challenging. In this work, water-soluble C₆₀ (wsC₆₀) was synthesized via a facile interfacial oxidation process. The presence of -OH on the C₆₀ cage may strengthen its binding affinity with Fe³⁺ ion and effectively modulate the incorporation of Fe/N into the C₆₀-derived carbon electrodes. By varying the wsC₆₀/Fe³⁺ mixing ratios followed by pyrolysis under NH₃, we obtained Fe/N-doped carbons (FeN@wsC₆₀-900) with distinct Fe/N-doping states, including FeN₄, O-FeN₄/Fe cluster, and FeN₄/Fe cluster. The abundant -OH in wsC₆₀ also promoted the formation of a highly porous network, enhancing active site accessibility. The resultant FeN@wsC₆₀-900 exhibited excellent oxygen reduction reaction (ORR) activity, outperforming both conventional C₆₀-derived carbons and commercial Pt/C. Structural characterizations and density functional theory (DFT) simulations revealed that the O-coordinated Fe-N₄ with adjacent Fe cluster could optimize the coordinate geometry and adsorption energies of key ORR intermediates.