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 m 2 g −1), and presence of both pseudocapacitive and electric double layer behavior, resulting in highest areal capacitance of 138.4 mF cm −2 , lowest selfdischarge 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 H 2 SO 4 electrolyte. This study is a first of its kind of structural evaluation and Raman characterization of N-rGO for application in supercapacitor cell.

New Insight into the Characterization of Graphene Oxide and Reduced Graphene Oxide Monolayer Flakes on Si-Based Substrates by Optical Microscopy and Raman Spectroscopy

“…Hence, depending on the properties of the material, such as defects, strain, doping, crystallinity, and the number or the orientation of layers (or walls), the spectral features show a significant variation, giving rise to additional peaks like the D-band (∼1350 cm −1 ) and D′band (∼1620 cm −1 ). 1,4,7,8 Therefore, Raman spectroscopy is an essential tool in the field of carbon research, and it is wellestablished in the road map of graphite to graphene.…”

“…As a fast, simple, and nondestructive tool, Raman spectroscopy provides valuable information on the structural properties of carbon-based materials, such as fullerenes, carbon nanotubes (CNTs), and graphene and its derivatives. − All these materials show some common Raman spectral features, yet the peak positions, widths, and intensities of the Raman spectra of each material have unique features to distinguish them from each other and predict their properties. , For example, the Raman spectra of sp 2 nanocarbons consist of two major features: the G-band (in the frequency range 1580–1600 cm –1 ) and the G′-band (also known as 2D-band – in the frequency range 2650–2800 cm –1 ). Hence, depending on the properties of the material, such as defects, strain, doping, crystallinity, and the number or the orientation of layers (or walls), the spectral features show a significant variation, giving rise to additional peaks like the D-band (∼1350 cm –1 ) and D′-band (∼1620 cm –1 ). ,,, Therefore, Raman spectroscopy is an essential tool in the field of carbon research, and it is well-established in the road map of graphite to graphene.…”

Effect of Nitrogen Doping on the Optical Bandgap and Electrical Conductivity of Nitrogen-Doped Reduced Graphene Oxide

“…The significance of D and G peaks has already been well addressed in previous reports [36,37], whereas the D" peak and I peak have not been well addressed. The I peak was observed as a shoulder to the D peak, which is ascribed to the nitrogen-doped carbon structure [38] or a highly disordered carbon [39]. Particularly, an increase in nitrogen doping concentration resulted in a decrease in the calculated area of the I peak, as shown in the Supplementary Materials (Table S1).…”

Dependence of Precursor Graphite Flake Size on Nitrogen Doping in Graphene Oxide and Its Effect on OER Catalytic Activity

“…N-doped graphene has been comprehensively analyzed in terms of its morphology, change in electronic structure, electrocatalytic applications, and theoretical simulations. 18 , 19 Our recent works show the applicability of nitrogen-doped reduced GO (N-rGO) as an advanced supercapacitor electrode 13 and as a catalyst support material for the OER. 20 , 21 N-rGO is similar in structure to N-doped graphene, excluding the presence of a few oxygen functional groups and defects in N-rGO that are not completely removed or restored during pyrolysis at high temperatures.…”

“…In a recent research work, Yadav et al explored the temperature-dependent synthesis of N-rGO, starting with natural graphite (flake size: 7 μm), and explained the structural effect on the supercapacitive behavior of N-rGO as an electric double-layer supercapacitor (EDLC). 13 In this study, the properties of N-rGO such as the degree of reduction, the extent of N-doping, formation of structural and lattice defects, specific surface area, and the crystallinity of rGO were investigated as a function of synthesis temperature. Furthermore, Hara et al demonstrated the use of N-rGO (starting from synthetic graphite, Sigma-Aldrich, flake size: < 20 μm) as the catalyst support and investigated its effect on the catalytic properties of IrO 2 nanoparticles (nps) as an electrocatalyst for the OER.…”