L-cysteine-assisted synthesis of ruthenium sulfide/thermally reduced graphene oxide nanocomposites: Promising electrode materials for high-performance energy storage applications

Abstract

This paper describes a facile, single-step hydrothermal method to prepare ruthenium sulfide/thermally reduced graphene oxide (RuS₂/TRGO) nanocomposites. In this synthesis procedure, aqueous solutions of RuCl₃, L-cysteine, and graphene oxide are employed as the metal, sulfur, and graphene sources, respectively. The chemical structures and morphologies of the nanocomposites are characterized by Xray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Cyclic voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy are used to examine their electrochemical performances. The RuS₂ nanoparticles (similar to 10 nm) uniformly disperse on the surfaces of the TRGO layers to form the RuS₂/TRGO composite, which adequately inhibits aggregation of the RuS₂ to fully exploit its impressive electrochemical activity and capacitance as a pseudocapacitive electrode material. The combination of the TRGO interconnected conductive networks and uniformly anchored RuS₂ generates a specific capacitance of 193 F g(-1) at a 5 mV s(-1) scan rate, 150 F g(-1) at a 0.5 A g(-1) current density, good rate capability (57.3% retention at 6.25 A g(-1)), and reasonable cycle stability (90% retention of capacitance over 2000 cycles at a current density of 0.75 A g(-1)). Further, the RuS₂/TRGO-30 composite electrode achieves energy densities of 20.84 and 6.11 Wh kg(-1) at power densities of 250 and 3666.7 W kg(-1), respectively. The RuS₂/TRGO composites are promising for high-level energy storage applications because of their superior electrochemical activities.