Fluid Dynamics-Induced Surface Engineering for Holey and Stable Metallic MoS₂ Nanosheets with High Pseudocapacitance and Ultrafast Rate Capability

Abstract

Two-dimensional molybdenum disulfide (MoS2) nanosheets have attracted great attention for electrochemical storage and conversion, but the scalable preparation of highly conductive and stable MoS2 nanosheets with a porous structure is challenging. Here, an efficient and high-throughput fluid dynamics process is presented for high-yield exfoliation of MoS2 with a phase transformation of 2H into 1T phase and basal activation of MoS2, resulting in ultrathin nanoporous nanosheets of MoS2 with a high-content 1T phase. The metallic and tailored porous structure in holey MoS2 nanosheets ensures a large ion-accessible area and rapid and efficient charge transport properties. The resulting MoS2 electrodes show an outstanding gravimetric capacitance of 572.6 F g–1 at 2 mV s–1, an impressive high capacitance retention of 71% measured in the 2–1000 mV s–1 range, and a good long-term stability with a capacitance retention of 96% over 10,000 cycles.

Microwave-Driven Exfoliation of Bulk 2H-MoS2 after Acetonitrile Prewetting Produces Large-Area Ultrathin Flakes with Exceptionally High Yield

“…This dispersion was prepared by ultracentrifuging the samples in NMP, discarding the supernatant and redispersing in ACN (the process was repeated three times, in order to remove the majority of the NMP). We note that the flakes obtained are apparently very uniform in height, as reflected in their uniform contrast (Figure a) . The flakes are also remarkably large in lateral size, with most flakes showing lateral sizes in the μm scale (1.2 μm ± 0.7 μm) (Figure SI 5).…”

High-Performance MnO2 Nanowire/MoS2 Nanosheet Composite for a Symmetrical Solid-State Supercapacitor

“… where E is the energy density, P is the power density, C sp is the gravimetric specific capacitance calculated through GCDs, V is the voltage window, and Δ t is the discharge time. 20 , 21 , 23 − 26 …”

“…The energy and power density were derived from galvanostatic charging–discharging at various current densities. The energy density and power density are evaluated using eqs and , respectively. where E is the energy density, P is the power density, C sp is the gravimetric specific capacitance calculated through GCDs, V is the voltage window, and Δ t is the discharge time. ,,− …”

“…It has been widely researched that a pseudocapacitor is an essential technological approach for superior electrochemical energy storage applications due to its excellent charge transfer reactions. − , Usually, transition metal oxides, such as MnO 2 , are promising for active substances in pseudocapacitors because of the striking cation exchange. The pseudocapacitors, such as the ruthenium oxide-based devices (RuO 2 ), have a large specific capacitance of 1580 F/g (at 1 mV/s).…”

“…The layered structure provides more surface area for charge storage and different oxidation states from +2 to +6 of the central Mo atoms to increase the pseudocapacitance. Generally, the 1T phase exhibits an improved hydrophilic behavior and an excellent electrical conductivity higher than that of 2H–MoS 2 , which directs to a higher specific capacitance in a liquid electrolyte. − Accordingly, 1T MoS 2 could be a suitable electrode material for manufacturing high-performance solid-state SCs. On the other hand, layered 1T-MoS 2 nanosheets lead to restacking due to the out-of-plane van der Waals (vdW) force of attraction between adjacent layers, reducing the active surface area and preventing effective electrolyte ion diffusion, ensuing in a faster decay of electrochemical performance. − To control the reaggregation and possible phase change of 1T-MoS 2 , which leads to poor performance, a solution-processable method to get MoS 2 nanosheets with stable dispersion is required to explore the spectrum of practical uses.…”