Abstract
Commercially available bulk niobium diselenide (NbSe 2 ) reduced into nanomaterials upon exfoliation typically contains oxide and carbide impurities. Liquid-phase exfoliated two-dimensional (2D) nanosheets of NbSe 2 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 NbSe 2 (intended to be integrated as supercapacitor electrodes) on the electrochemical performance. The highest specific capacitances achieved using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6 ) and sulfuric acid (1 M H 2 SO 4 ) electrolytes were 4955.5 ± 21.5 and 13 361.6 ± 31.8% mF/cm 2 , 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 charging procedure in the cell for BMIMPF 6 , resulting in leakage and decomposition of the electrolyte. Electrochemical impedance spectroscopy provides insights into the solid-electrolyte interphase and charge-transfer mechanisms at exfoliated 2D NbSe 2 nanosheets, which affect the ion intercalation through heterogenous phases of the nanosheets. Overall, the NbSe 2 nanosheets offer heterogenous phases because of the coexistence of Nb 2 O 5 that influences the charge-transfer mechanism at the exfoliated surfaces.
| Original language | English |
|---|---|
| Pages (from-to) | 8671-8680 |
| Number of pages | 10 |
| Journal | Journal of Physical Chemistry C |
| Volume | 123 |
| Issue number | 14 |
| DOIs | |
| State | Published - Apr 11 2019 |
| Externally published | Yes |
Funding
Authors would like to thank Dr. Fumiya Watanabe from the Center for Integrative Nanotechnology Sciences at the University of Arkansas at Little Rock for the XPS measurements and Prof. Jeffrey Halpern in the Department of Chemical Engineering at the University of New Hampshire for his assistance with the electrochemical characterizations. This work was supported in part by the Center for Advanced Materials and Manufacturing Innovation (CAMMI) at the University of New Hampshire.