Effect of Carboxyl-Doped Graphene Nanoplatelets as an Electrode for Supercapacitors According to Surface Property Changes via the Control of Conditions

Abstract

Energy storage systems (ESSs) are attracting increasing attention for the development of sustainable and renewable energy technologies owing to limited fossil fuels. Supercapacitors are gaining significant interest as energy storage devices owing to their high-power density and long-term cycle stability. The use of suitable electrode materials affects the performance of supercapacitors. In this study, we fabricated a carboxyl-doped graphene nanoplatelet (CGnP) via a mechanochemical reaction. Additionally, CGnP was activated by controlling parameters such as temperature, flow rate, and maintenance period and evaluated as an electrode material for supercapacitors. The effect of the specific surface area (SSA) and functional groups of the fabricated samples on the capacitance was confirmed by controlling the activation parameters. The activated CGnP with 300 mL/min of CO2 at 1173 K for 4 h exhibited a high SSA of 1300 m2/g. The activated CGnP (180 F/g), with a high SSA, showed an increased capacitance of 46% compared to pristine CGnP (123 F/g). Additionally, activated CGnP1100 demonstrated good wettability and exhibited excellent stability with a low capacitance decrease of 6.1%, even after 10,000 cycles.