Buckyball C60/Fe–N4 superstructured electrodes for efficient oxygen reduction reaction†

Fullerene-based materials are promising electrodes for various electrochemistry applications due to their specific electronic properties, easy functionalization, and self-assembly capability. To achieve good catalytic performance, fullerenes are always converted into unfolded fullerenes in the derived carbon electrodes. However, the potential of fullerene-based electrodes with closed-cage fullerenes, which may further reflect the fullerene's uniqueness, still needs to be explored. Here, we fabricated a new fullerene C₆₀-based electrode (C₆₀–FePc_500) by the co-assembly of C₆₀ and iron-phthalocyanine (FePc) and pyrolysis under the low temperature of 500 °C for the oxygen reduction reaction (ORR). C₆₀–FePc_500 could maintain the buckyball structure of C₆₀ with the binding of active Fe–N₄ derived from FePc. For the first time, this buckyball C₆₀/Fe–N₄ superstructured electrode with complete C₆₀s exhibited higher catalytic ORR performance than the unfolded C₆₀s electrodes from 900 °C heat treatment (C₆₀–FePc_900). Based on the structural analysis and the simulations, the excellent catalytic activity of C₆₀–FePc_500 is estimated due to the improvement of the closed-cage C₆₀s on the electronic density states of Fe–N₄ catalytic sites. This work may bring new insights into understanding the driven mechanism of fullerenes and the development of superior fullerene-based electrodes for electrocatalytic processes.