Novel Gram‐Scale Synthesis of Carbon Nano‐Onions from Heavy Oil for Supercapacitors

Abstract Carbon nano‐onions (CNOs), recognized as multilayered fullerenes, display superior electrical conductivity (comparable with carbon black) and large surface area due to the highly defective sp 2 carbon shells, making it a promising member of carbon nanomaterials for energy applications. However, the lack of efficient synthesis of CNOs in large‐scale production (gram quantities) has impeded their range of commercial applications. Herein, for the first time, it is demonstrated that the gram‐scale synthesis of CNOs is developed by simply annealing pitch‐coated petroleum coke for supercapacitors. Significantly, the CNOs with diameters of ≈5–30 nm and abundant micropores deliver outstanding specific capacitance of 312 F g −1 at 1 A g −1 and retain 251 F g −1 at 20 A g −1 . Moreover, the corresponding synthesis mechanism is proposed to gain a clear insight into the formation of CNOs from heavy‐oil‐based carbon precursors. This work provides a practical pathway to synthesize CNOs on a large scale.