Electrochemical Performance and Characterization of Supercapacitor Device Using Carbon Nanotube/Graphene Nanoplatelet Composites with Biomass-Derived Carbon Dots

Abstract

The commercialization of flexible electronic goods has driven interest in flexible wearable energy storage devices, notably supercapacitors (SC). The supercapacitive electrodes made from green, renewable materials are essential for facilitating an eco-friendly approach. This work focused on integrating doped carbon dots (CDs) on the surface of the carbon nanotube/graphene nanoplatelets (CNT:GNP), exhibiting excellent structural/electrochemical characteristics. The CNT was purified by thermal treatment in a CVD furnace, while the CDs were extracted and hydrothermally synthesized from the biowaste of black lentils. The CDs/CNT:GNP hybrid composite electrode and device demonstrated excellent electrochemical behavior in 1M Na2SO4 electrolyte. The combination of CNT and GNP was synergistic as CNTs dispersed evenly in the material prevented GNP from stacking, enhancing surface area, porosity, and conductivity. Additionally, CNT intercalation created a porous, linked network for electrolyte ion transfer. The resulting electrode materials S-doped CDs/CNT:GNP exhibited better electrochemical performance, with capacitance values of 888 F/g at a scan rate of 5 mV/s (recorded 0 to 0.8 V voltage window, with low solution resistance of 0.28 Ω). Moreover, the doped CDs/CNT:GNP device showed remarkable cyclic retention, i.e., ~80% after 10,000 cycles, due to the imparted structural stability, making them a good contender in SC.