Two-Dimensional Water-Coupled Metallic MoS₂ with Nanochannels for Ultrafast Supercapacitors

Abstract

MoS is a promising electrode material for energy storage. However, the intrinsic multilayer pure metallic MoS (M-MoS) has not been investigated for use in supercapacitors. Here, an ultrafast rate supercapacitor with extraordinary capacitance using a multilayer M-MoS-HO system is first investigated. Intrinsic M-MoS with a monolayer of water molecules covering both sides of nanosheets is obtained through a hydrothermal method with water as solvent. The super electrical conductivity of the as-prepared pure M-MoS is beneficial to electron transport for high power supercapacitor. Meanwhile, nanochannels between the layers of M-MoS-HO with a distance of ∼1.18 nm are favorable for increasing the specific space for ion diffusion and enlarging the surface area for ion adsorption. By virtue of this, M-MoS-HO reaches a high capacitance of 380 F/g at a scan rate of 5 mV/s and still maintains 105 F/g at scan rate of 10 V/s. Furthermore, the specific capacitance of the symmetric supercapacitor based on M-MoS-HO electrodes retain a value as high as 249 F/g under 50 mV/s. These findings suggest that multilayered M-MoS-HO system with ion accessible large nanochannels and efficient charge transport provide an efficient energy storage strategy for ultrafast supercapacitors.

Metallic MoS2 for High Performance Energy Storage and Energy Conversion

“…Pan et al reported that metallic MoS 2 can also be fabricated by Na 2 MoO 4 •2H 2 O and L‐cysteine in a mixed solvent of DMF and water with a DMF to water ratio of 1.5:1 at 200 °C for 12 h (Figure b). The layer distance of the as‐prepared metallic MoS 2 is around ≈0.90 nm that is much larger than the traditional layer distance of ≈0.62 nm . Song et al proved that metallic MoS 2 could also be achieved by solvothermal method in the mixture of DMF and water of 1:50 .…”

“…The main two MoS 2 phases, metallic 1T phase and semiconducting 2H phase, due to the distinct structures, exhibit noticeable difference in their physical and chemical properties, especially the conductivity properties, where the metallic phase has ≈10 5 times electrical conductivity compared to the semiconducting phase . The low electrical conductivity of semiconducting MoS 2 is disadvantageous for electrochemical energy storage .…”

“…Furthermore, previous studies found that the basal plane of semiconducting 2H phase MoS 2 is catalytically inert for hydrogen evolution reaction (HER), whereas the basal planes of metallic 1T MoS 2 are rich in active sites, which has the benefit of higher reaction kinetics between electrons and protons (H + ) on the active sites, and makes the 1T MoS 2 more promising candidate on energy generation and conversion fields. Methods for re‐engineering MoS 2 through new metallic structures that can solve the intrinsic problems of conductivity and catalytic activities have been developed …”

Interlayer Nanoarchitectonics of Two‐Dimensional Transition‐Metal Dichalcogenides Nanosheets for Energy Storage and Conversion Applications

“…The excellent electrochemical performances of the M-MoS 2 are attributed to the high electrical conductivity benefiting the charge transfer and the expanded interlayer providing abundant nanochannels for fast diffusion of electrolyte ion. [131] Recently, An and co-workers , respectively and exhibit excellent cycling stability of over 1000 cycles (capacitance retention of 98% and 87% at current densities of 50 A g −1 and 100 A g −1 ). An asymmetric 1T′-MoTe 2 //activated carbon supercapacitor exhibits a maximum specific capacitance of 158.9 F g −1 with an energy density up to 56.4 W h kg −1 .…”

“…Zhu et al develop a hydrothermal route to synthesize metallic MoS 2 (M-MoS 2 ) with expanded nanochannels for ultrafast supercapacitors ( Figure 10G-K). [128,129] XRD analysis in Figure 10G reveals a peak at 7.5° corresponding to an interlayer spacing of 1.18 nm in the wet M-MoS 2 (M-MoS 2 −H 2 O) sample. It can be assigned to (001)-H 2 O for M-MoS 2 −H 2 O, in which a bilayer of water molecules is adsorbed between the adjacent layers of MoS 2 nanosheets, resulting expanded interlayer as nanochannels for ultrafast supercapacitors ( Figure 10I).…”