Electrodeposition and Capacitance of WS2 Thin Films Onto ITO and Glassy Carbon from Aqueous and Non-Aqueous Electrolytes

Abstract

Two-dimensional (2D) layered materials, including graphene, metal oxides, metal chalcogenides and their composites have shown to be efficient and promising materials for high performance supercapacitor electrodes, with high surface area and large in-plane conductivity. Among the 2D layered supercapacitors, MoS2, MoSe2, WS2, and WSe2 are semiconductors with intriguing electronic, electrochemical and electrocatalytic properties. We have synthesized WS2 thin films onto both ITO and glassy carbon electrodes by the electro-reduction of (NH4)2WS4 from both aqueous and acetonitrile electrolytes. During cyclic voltammetry, a cathodic peak that overlaps with H2 evolution is observed at at -1.2V vs Ag/AgCl in aqueous solutions. In acetonitrile, no cathodic peak is observed on ITO, but a cathodic peak that overlaps with a background cathodic peak is observed on glassy carbon. The background peak appears to arise form TEA-BF4 reduction, since the current density scales with TEA-BF4 concentration. The standard reduction potential, effective diffusion coefficient and transfer coefficient for WS2 electrodeposition in acetonitrile are determined are estimated from cyclic voltammetry at different scan rates. Results will also be presented for the specific capacitance of WS2 films deposited atop glassy carbon electrodes (GCE) following application of potential sweep methods for activing GCE.