Hydrothermal self-assembly and supercapacitive behaviors of Co(II) ion-modified graphene aerogels in H2SO4 electrolyte

Reduced graphene oxide (r-GO) aerogels decorated with divalent cobalt ions were synthesized via a one-pot hydrothermal self-assembly route. The interaction of Co(II) ions with 3D r-GO aerogels was investigated by spectroscopic techniques, including Raman, attenuated total reflectance infrared, and X-ray photoelectron spectroscopies. The excellent electrochemical properties of the aerogels were confirmed by cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy in an acid electrolyte (1 M H2SO4). The Co(II) ion-modified r-GO aerogels can be used as high-performance hybrid supercapacitor materials with a specific capacitance of 387.2 Fg(-1) at 1 Ag-1 current density and a good cycling stability without capacity decay over 1000 cycles. The mechanical integrity enhancement of the hybrid r-GO aerogel framework and the improvement in its unique capacitive performance are attributed to the efficient interconnection produced by electro-active Co(II) ions. (C) 2014 Elsevier Ltd. All rights reserved.This work was supported by the research fund of Hangyang University (HY-2013 year), the SRG-Fd (project no. of 7004081) of City University of Hong Kong, and the ITS/244/11 of Innovation and Technology Fund, HKSAR. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2013R1A1A2007365), the Korea Foundation for the Advancement of Science & Creativity (KOFAC), and the Korean Government (MOE) (201310870001). In this study, we acknowledged XPS measurements (ESCALAB 250 XPS system, Theta Probe XPS system) from KBSI, Busan Center