Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors.

Yong-Qiang Dang,Shao-Zhao Ren,Jiangtao Cai,Guoyang Liu,Jieshan Qiu,Yating Zhang

doi:10.3390/nano6110212

Abstract

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H2SO4. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

Highlights

Because of the rapidly increasing demands for energy storage devices in electric vehicles, mobile electronic devices, and memory backup systems, supercapacitors—which have high power densities, fast charge-discharge rates, and long lifetimes [1,2,3]—have been the topic of much research interest
The morphologies of the as-prepared 50-carbon dots (CDs) were investigated with transmission electron microscopy (TEM)
According to the Fourier transform infrared (FTIR) analysis of 50-CDs (Figure 1b), an N–H bending vibration was observed at 1560 cm−1 for the 50-CDs, indicating that amino functional groups were successfully formed on their surfaces

Summary

Introduction

Because of the rapidly increasing demands for energy storage devices in electric vehicles, mobile electronic devices, and memory backup systems, supercapacitors—which have high power densities, fast charge-discharge rates, and long lifetimes [1,2,3]—have been the topic of much research interest. As one type of CDs, graphene quantum dots (GQDs) have been effectively improving supercapacitors’ performances in the electrochemical capacitive properties of GQDs supercapacitors [23], GQDs/MnO2 supercapacitors [24], GQDs/polyaniline nanofiber supercapacitors [25], and GQDs/polyaniline asymmetric micro-supercapacitors [26] These studies provide new insight for increasing specific capacitances of the electrode materials for high-performance supercapacitors. A composite electrode with a CDs-to-rGO ratio of 5:1 displayed a good reversibility, an excellent rate capability, fast charge transfer, and a specific capacitance of 211.9 F/g, which was 74.3% higher than that of rGO electrode (121.6 F/g) These encouraging results suggest that CDs/rGO supercapacitors have high performances

Results and Discussion

Chemicals

Electrochemical Measurements

Conclusions