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 13 361.6 ± 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 charging procedure in the cell for BMIMPF6, 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 NbSe2 nanosheets, which affect the ion intercalation through heterogenous phases of the nanosheets. Overall, the NbSe2 nanosheets offer heterogenous phases because of the coexistence of Nb2O5 that influences the charge-transfer mechanism at the exfoliated surfaces.

Tailoring Superconductivity in Large-Area Single-Layer NbSe2 via Self-Assembled Molecular Adlayers

“…The Se 3d core level spectrum in Figure 2d can be deconvolved into three components, with the main component stemming from Se 2in NbSe2. 42,43 The fitting procedure resulted in an atomic ratio Se/Nb of 2.1, in good agreement with the expected ratio of 2.0, corroborating the high quality of the NbSe2 monolayers. The other two minor components can be ascribed to residual amorphous Se and trigonal Se, which form as clusters on the surface that are imaged as bright protrusions in large area AFM maps (see Figure S1).…”

Incorporating Nb into MoSe2 Nanoflowers for Overall Electrocatalytic Water Splitting

“…The O-1 s XPS spectra (Figure 1d) show a significant change with higher Nb content -while MoÀ O bonds are seen in the pristine material, the growing fraction of oxygen in the modified samples exhibits a prominent peak at a binding energy of 530.6 eV which corresponds to Nb 2 O 5 . [54] To conclude: the XPS characterization probes the thin petals of the nanoflowers, showing that Nb-modified MoSe 2 , MoO 3 , and Nb 2 O 5 exist on the surface without evidence for niobium selenide phases. The shift observed in the binding energy of Mo and Se upon Nb doping suggests that the electronic structure is modified, which can potentially affect the chemical interaction with the reaction intermediates to promote catalytic activity.…”

Effect of pH on the Corrosion and Repassivation Behavior of TA2 in Simulated Seawater

“…where C is the capacitive constant, j is the imaginary unit, f is the frequency, and n is a CPE power that is between 0 and 1. Q is the pure capacitance when n = 1, and Q is the pure resistance when n = 0 [32]. R s is the solution resistance, Q f represents the CPE of the passive film, and R f is the resistance of film.…”