A Fullerene Seeded Strategy for Facile Construction of Nitrogen-Doped Carbon Nano-Onions as Robust Electrocatalysts

Carbon nano-onions (CNOs) as a novel form of carbon materials hold peculiar structural features but their electrocatalytic applications are largely discouraged by the demanding synthesis conditions (e.g., >= 1500 degrees C and vacuum). Using C-60 fullerene molecules as the sacrificial seeds and melamine as the main feedstock, herein, a novel strategy for the facile construction of CNOs nanoparticles is presented with ultrafine sizes (approximate to 5 nm) at relatively low temperatures (<= 900 degrees C) and atmospheric pressure. During the calcination, in-depth characterizations reveal that C-60 can retain the melamine-derived graphitic carbon nitride from complete sublimation at high temperatures (>= 700 degrees C). Owing to the N removal and subsequent pentagon generation, severely deformed graphitic fragments together with the disintegrated C-60 molecules merge into larger sized nanosheets with high curvature, eventually leading to the formation of N-doped defect-rich CNOs. Owing to the integration of multiple favorable structural features of pentagons, edges, and N dopants, the CNOs obtained at 900 degrees C present superior oxygen reduction half-wave potential (0.853 V-RHE) and zinc-air cathode performance to the commercial Pt/C (0.838 V-RHE). Density functional theory calculation further uncovers that the carbon atoms adjacent to the N-doped edged pentagons are turned into the ORR-active sites with O-2 protonation as the rate-determining step.