Novel Gram-Scale Synthesis Of Carbon Nano-Onions From Heavy Oil For Supercapacitors

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 approximate to 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.