One‐Pot Synthesis of Sulfur and Nitrogen Co‐Functionalized Graphene Material using Deep Eutectic Solvents for Supercapacitors

Abstract

A green approach to the synthesis of sulfur and nitrogen co‐functionalized reduced graphene oxide (SN‐rGO) is presented; it involves the reduction of graphene oxide (GO) using a deep eutectic solvent (DES) as chemical reducing agent and dopant. For the first time, a DES of choline chloride and sodium sulfide comprising cheap and safe components is introduced, and is both highly effective and reusable as a reducing agent for the production of SN‐rGO. The DES is utilized as a solvent as well as reducing agent and dopant to generate SN‐rGO. This DES is highly efficient in removing oxygen functionalities from GO and for subsequent sulfur and nitrogen functionalization for high energy‐storage efficiency. The reduction ability of this DES is confirmed with five consecutive cycles, which adds to its sustainability and recyclability in the development of energy‐storage devices. SN‐rGO exhibits a high specific capacitance of 509 F g−1 at 1 A g−1, which corresponds to high energy and power densities of 57.3 Wh kg−1 and 1804.7 W kg−1, respectively. This simple and green method for direct reduction of GO with sulfur and nitrogen functionalization on the graphene surface can provide cost‐effective bulk production of a nanocarbon template for energy storage applications.

Waste‐Derived Heteroatom‐Doped Activated Carbon/Manganese Dioxide Trio‐Composite for Supercapacitor Applications

“…In the XPS survey scan of MnO 2 @N–AC (Figure a), four peaks were revealed corresponding to carbon (C1s), oxygen (O1s), nitrogen (N1s), and manganese (Mn2p 1/2 and Mn2p 3/2 ). The high‐resolution C1s XPS spectrum of MnO 2 @N–AC (Figure b) showed the peaks at 288.1 eV (OCO, CO), 286.2 eV (CN, CO), and 284.5 eV (CC, CC) . Further, the N1s spectrum was analyzed to confirm the binding of nitrogen in MnO 2 @N–AC (Figure c).…”

“…The heteroatoms and the metal oxide‐containing groups are deliberated as important in charge‐storing ability. N functionalization leads electrons into carbon as a carrier and permits convenient contact of the electrolyte ions for double‐layered formation . To increase the conductivity, the tactic to integrate MnO 2 into carbonaceous materials is of great effectiveness and importance, which offer a high electroactive surface area and consistent electrical connection for the maximum utilization of MnO 2 .…”

“…At high frequencies, the imaginary portion ( Z ″) is nearby zero of the impedance and the ( Z ′) measured portion is the ohmic resistance, which is the factual part of resistance arising due to electrolyte and the contact between current collector and electrode material. The lower standards of equivalent series resistance (ESR) predict the decent conductance of the electrochemical system . The quasicircle for MnO 2 @N–AC in the higher‐frequency part and line in the lower‐frequency region are due to the formation of EDL at the electrode and electrolyte edge .…”

“…A symmetrical two‐electrode setup was also applied for MnO 2 @N–AC materials . The 0–0.9 V potential window was applied for CV and GCD.…”

“…To approve of the performance of our electrode material, all tests (CV and GCD) were conducted at different scan rates (0.1–0.5 V s −1 ) and several current densities (1.0–5.0 A g −1 ). Specific capacitance calculations were conducted by GCD curves, using Equation …”