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

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.