Oriented Graphenes from Plasma-Reformed Coconut Oil for Supercapacitor Electrodes

The utilization of vertical graphene nanosheet (VGN) electrodes for energy storage in supercapacitors has long been desired yet remains challenging, mostly because of insufficient control of nanosheet stacking, density, surface functionality, and reactivity. Here, we report a single-step, scalable, and environment-friendly plasma-assisted process for the fabrication of densely packed yet accessible surfaces of forested VGNs (F-VGNs) using coconut oil as precursor. The morphology of F-VGNs could be controlled from a continuous thick structure to a hierarchical, cauliflower-like structure that was accessible by the electrolyte ions. The surface of individual F-VGNs was slightly oxygenated, while their interior remained oxygen-free. The fabricated thick (>10 μm) F-VGN electrodes presented specific capacitance up to 312 F/g at a voltage scan rate of 10 mV/s and 148 F/g at 500 mV/s with >99% retention after 1000 cycles. This versatile approach suggests realistic opportunities for further improvements, potentially leading to the integration of F-VGN electrodes in next-generation energy storage devices.