3-Dimensional ordered reduced graphene oxide embedded with N-doped graphene quantum dots for high performance supercapacitors

Abstract

The development of electrode materials with high energy and power densities is timely needed. In this study, the 0-dimensional N-doped graphene quantum dots (N-GQDs) embedded into 3-dimensional porous reduced graphene oxide (N-GQD/3DrGO) hybrid materials were hydrothermally fabricated for high performance supercapacitor application. The 2 – 6 nm N-GQDs with an average particle size of 4 ± 0.5 nm are homogenously dispersed onto the porous 3DrGO, resulting in the increase in the specific surface area with continuous meso‑macroporous channels. Moreover, the bimodal pore size distribution with a suitable meso‑macropore size range of 2.1 – 77.2 nm accelerates the electron and ion transports inside N-GQD/3DrGO to improve the electrochemical performance of supercapacitor application. N-GQD/3DrGO exhibits a superior specific capacitance of 361 F g − 1 at 2 A g − 1 in the presence of the voltage range of -1 – 1 V (vs Ag/AgCl) using Na2SO4 as the electrolyte. In addition, N-GQD/3DrGO hybrid materials show excellent long-term cycling stability, and 89.2% of the initial capacitance can be retained after 10,000 cycles. The embedded N-GQDs can minimize the re-stacking of rGO nanosheets as well as improve the pore texture and conductivity, while the 3D rGO serves as a carbon backbone to reduce the diffusion path of electrons and ions. This advantage results in a superior energy density of 111.2 − 24.2 Wh kg−1 at the power density of 260 − 5000 W kg−1. The excellent electrochemical performance clearly demonstrates that combination of different morphologies of graphene-based nanomaterials is a novel strategy to fabricate a superior electrode material for supercapacitor applications, which can provide a unique alternative to explore the new boundary of energy-related nanomaterials for high performance asymmetric energy storage devices.