▎ 摘　　要

Alone, it is expected, and also was experimentally proved, that calcium carbonate and reduced graphene oxide do have negligible specific capacitance due to the chemical composition of both materials. However, synthesis of CaCO3 on the form of very thin sporadic layer attaching rGO results in dramatic increase in the specific capacitance of the obtained composite due to formation of the electrochemical double layer at the interfacial area. Moreover, the specific capacitance could be further enhanced by nitrogen-doping of the rGO sheets. Typically, a novel N-rGO/CaCO3 composite has been successfully synthesized by heat reflux strategy with graphite powder, calcium acetate and urea as raw materials. The composite was characterized by X-Ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FESEM), coupled with rapid EDAX (energy dispersive analysis of X-Ray) and X-ray photoelectron spectroscopy. The utilized physiochemical characterizations indicated that the final prepared composite can be demonstrated as N-doped rGO decorated by very thin discrete layer from calcium carbonate. Supercapacitive performance of N-rGO/CaCO3 composite has been investigated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M KOH solution. The results reveal that the N-rGO/CaCO3 composite delivers a large specific capacitance of as high as 214 Fg(-1) and 188 Fg(-1) at 5 mV s(-1) and 1.0 Ag-1, according to CV and galvanostatic charge-discharge tests, respectively; while the CaCO3, rGO, rGO/CaCO3, N-rGO based electrodes has a poor electrochemical performance at the same conditions. Moreover, the as-prepared composite exhibited excellent long cycle stability with about 88.7% specific capacitance retained after 10,000 cycles. (C) 2015 Elsevier Ltd. All rights reserved.