Synthesis and Electrochemical Studies of 3D Reduced Graphene Oxide for Efficient Energy Storage

Abstract

Three-dimensional (3D) graphene-based materials are highly desirable for supercapacitor applications; however, their synthesis requires multiple time-consuming steps that involve templates and cross-linkers. Thus, chemically derived graphene through the reduction of graphene oxide is preferred for scalable synthesis. Here, a facile one-pot wet chemical synthesis for an improved highly interconnected 3D reduced graphene oxide (3D-rGO) was developed where the extent of oxidation and the temperature for reduction were optimized. These facile interconnected structures were achieved through covalent linkages via functional groups. The optimized 3D-rGO demonstrated a high C/O ratio (5.2) and nominal defect density (ID/IG = 0.90) due to its stable structure. Electrochemical characterization revealed that the 3D-rGO possessed a superior specific capacitance of 256 F g–1 in an aqueous electrolyte. Trasatti analysis revealed an 84% contribution from the electrical double-layer (EDL) mechanism, which implied a high sp2 carbon content and superior conductivity. This superb performance, which was further validated in a quasi-solid-state device in an aqueous gel electrolyte (H2SO4-PVA), revealing that an excellent gravimetric energy density of 24.4 Wh kg–1 could be delivered at a power density of 1 kW kg–1. A maximum power density of 28 kW kg–1 delivered a stable 18.8 Wh kg–1 of energy. Furthermore, the supercapacitor exhibited 184 F g–1, with a capacity retention of 91% following 10,000 cycles at 10 A g–1, which is promising for practical energy storage applications.