Ionic Liquid‐Intercalated Metallic MoS₂ as a Superior Electrode for Energy Storage Applications

Abstract

The development of MoS2 in the metallic phase (1T‐MoS2) is of paramount interest as it exhibits superior electrochemical activities compared to its semiconducting polymorph (2H‐MoS2). In this work, an ionic liquid (IL)‐assisted solvothermal method was employed to produce the thermodynamically metastable 1T‐MoS2. Structural characterization of the material suggests the intercalation of the IL into MoS2. De‐intercalation of ILs from 1T‐MoS2 leads to the formation of 2H‐MoS2. Carbon cloth‐supported 1T‐MoS2(1T‐MoS2@CC) shows higher electrocatalytic activity towards acidic hydrogen evolution reaction (HER) by delivering a current density of 50 mA/cm2 at an overpotential of 210 mV whereas 2H‐MoS2@CC requires an overpotential of 260 mV to reach the same current density. In addition, the 1T‐MoS2@CC electrode delivers a high electrochemical double‐layer storage ability compared to 2H‐MoS2@CC in 1 M Na2SO4. The enhanced electrochemical activity of 1T‐MoS2 over 2H‐MoS2 may be due to the existence of conducting basal planes and the high interlayer spacing (about 1 nm) caused by the intercalation of ILs into the MoS2 layers.

Molecular Understanding of Charge Storage in MoS2 Supercapacitors with Ionic Liquids

“…The gravimetric capacitance is of the same magnitude as the ILs-intercalation 1T-MoS 2 electrode used in the previous experiment (18 F g −1 ). [28] In particular, in this experiment, the interlayer spacing, obtained by [Emim] + insertion, is 1.006 nm, close to the simulation result (1.115 nm). The volumetric capacitance is also at the same magnitude with an experiment that 250 F cm −3 was obtained of a 1T-MoS 2 electrode with [Emim][BF 4 ]/ACN, [18] indicating that the simulation and experiment could be in agreement for comparison.…”

“…IL molecules into the MoS 2 layers led to an enhanced interlayer spacing (~1 nm) with the generation of conducting basal planes, which exhibits superior electrochemical properties. [28] Geng et al synthesized pure 1T-MoS 2 combined with an inserted monolayer of water, which results in an interlayer spacing of 1.18 nm, and utilized it for supercapacitor application. [23] They found that the capacitance of such a supercapacitor could reach 380 F g −1 in aqueous Li 2 SO 4 solution, and 88% of specific capacitance remained after 10 000 cycles at 5 A g −1 .…”

Cr3+ Ion‐Induced Phase Stabilization of 1T−MoSe2 with Abundant Active Sites for Efficient Hydrogen Evolution Reaction

“…Thus, the improved activity of the 1T/2H−MoSe 2 (2 Cr) is attributed to the conducting basal planes, high 1T phase content and the presence of additional active sites. The ECSA normalized polarization curves provide the insight about the per site catalytic activity [29] . Interestingly, the per site activity of 1T/2H−MoSe 2 (2 Cr) is lower compared to the 2H−MoSe 2 (Figure S7) which further complements the fact that the improved electrocatalytic activity of 1T/2H−MoSe 2 (2 Cr) is due to the presence of more number of active sites.…”

“…Similarly, the insertion of oxidized DMF species into MoS 2 layers also could stabilize the 1T phase [28] . Recently, we have shown that intercalation of ionic liquids into MoS 2 can stabilize the 1T phase MoS 2 [29] …”

Enhancement of 1T‐MoS2 Superambient Temperature Stability and Hydrogen Evolution Performance by Intercalating a Phenanthroline Monolayer

“…Molybdenum disulfide is a layered van der Waals solid with remarkable properties tunable for nanoelectronics, energy storage and catalysis [1–5] . Two kinds of MoS 2 layer structures are known, with the trigonal‐prismatic (called 2H) and octahedral (1T) coordination surrounding of Mo with S in the S−Mo−S sandwich‐like layers, resulting to semiconducting stable material or its metallically conducting metastable counterpart, respectively [6,7] .…”