Effects of Impurities on the Electrochemical Characterization of Liquid-Phase Exfoliated Niobium Diselenide Nanosheets

Abstract

Commercially available bulk niobium diselenide (NbSe2) reduced into nanomaterials upon exfoliation typically contains oxide and carbide impurities. Liquid-phase exfoliated two-dimensional (2D) nanosheets of NbSe2 obtained from bulk powders provide high charge mobility and large surface area but become self-passivated and chemically inert as the presence of oxide impurities makes them behave more semimetallic. In this article, we report the effects of inherent impurities of liquid-phase exfoliated 2D NbSe2 (intended to be integrated as supercapacitor electrodes) on the electrochemical performance. The highest specific capacitances achieved using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and sulfuric acid (1 M H2SO4) electrolytes were 4955.5 ± 21.5 and 13\u2009361.6 ± 31.8% mF/cm2, respectively, which were affected by the impurities, oxophilicity of niobium defects, and moisture adsorption in the cell. Galvanostatic charge–discharge profiles show moisture adsorption affecting the high-energy char...