Intercorrelation between physical and electrochemical behavior of nitrogen-doping in graphene for symmetric supercapacitor electrode

Abstract

Graphene and heteroatom-doped graphene are potential candidates for high-performance energy storage applications, such as supercapacitors. Herein, we have studied the structure and defect generation in nitrogen-doped reduced graphene oxide (N-rGO), synthesized via pyrolysis of urea in a wide temperature range (600–900 °C). Nitrogen-doped defect densities were analyzed in detail by the deconvolution of the Raman spectrum, where we found the importance of additional I and D’’ peaks. I peak is found to be sensitive to the dopant, and D” peak is consistent with the crystallinity, which are further revealed by X-ray photoelectron spectroscopy and X-ray diffraction measurements. Synthesized N-rGO was then investigated for the supercapacitor electrode. N-rGO synthesized at 800 °C, having low crystallinity (crystallite size 3.44 nm), highest degree of reduction (C/O ratio = 23), high specific surface area (152.3 m2 g−1), and presence of both pseudocapacitive and electric double layer behavior, resulting in highest areal capacitance of 138.4 mF cm−2, lowest self-discharge rate, and exceptional capacity retention of 121.7% after 10,000 cycles of charge–discharge. The synthesized electrode material has also been tested for a symmetric supercapacitor cell showing high specific capacitance 66.8 F g−1 in 0.5 M H2SO4 electrolyte. This study is a first of its kind of structural evaluation and Raman characterization of N-rGO for application in supercapacitor cell.