Self-Assembled 1T-MoS₂/Functionalized Graphene Composite Electrodes for Supercapacitor Devices

Abstract

Two-dimensional (2D) materials such as graphene and molybdenum disulfide (MoS2) have been investigated widely for applications in energy storage, including supercapacitors, due to their high specific surface area, potential redox activity, and mechanical flexibility. However, electrodes comprising either pure graphene and MoS2 have failed to reach their potential due to restacking of the layered structure and poor electrical conductivity. It has been shown previously that composite electrodes made from a mixture of graphene and MoS2 partially counteract these issues; however, performance is still limited by poor mixing at the nanoscale. Herein, we form a true composite electrode by chemically functionalizing the graphene so that the negatively charged surface can self-assemble with the positively charged 1T-MoS2 to give an alternating layer structure. These alternately restacked 2D materials were then used to produce supercapacitor electrodes, and their energy storage properties were characterized. This stacked structure has increased the interlayer spacing of 1T-MoS2 which was indicated by the increase in the intensity of the (001) peak in the X-ray diffraction spectra. Furthermore, the typically metastable 1T-MoS2 was stabilized by the interaction with the functionalized graphene, preventing it reverting back to the 2H phase, which was observed when pristine graphene was used. The graphene was functionalized using either 4-bromobenzenediazonium or 4-nitrobenzenediazonium, with the latter giving optimal capacitance when mixed with the MoS2. The alternative layer graphene–MoS2 structure was confirmed by Raman spectroscopy and electron microscopy, leading to a high specific capacitance (290 F cm–3 at 0.5 A g–1) and 90% retention of capacitance after 10 000 cycles.

Gelatin-assisted co-exfoliation of graphene nanoplatelets/MoS2for high-performance supercapacitors

“…65 The electrochemical performance of GNP/MoS 2 is found to be better than that of the recently reported MoS 2 / graphene-based electrode. 38,42 The comparison (Table 1) is made to signify the electrochemical properties of the reported work. Also, as an individual, the specic capacitances of GNP and MoS 2 were calculated to be about 226.12 F g À1 and 216.13 F g À1 respectively at 1 A g À1 .…”

“…41 Zhuo et al prepared a 1T/MoS 2 /functionalized graphene electrode for energy storage having a specific capacitance of 290 F cm −3 at 0.5 A g −1 with a cyclic retention of 90% after 10 000 cycles. 42 Thus, the co-exfoliation of GNP/MoS 2 has not been reported so far by using biomolecules for super capacitive performance.…”

Advances in 2D Molybdenum Disulfide‐Based Functional Materials for Supercapacitor Applications

“…A symmetric SC fabricated using the composite electrode delivered an areal capacitance of 290 mF cm −2 at a current density of 0.5 A g −1 in a neutral 0.5 M Na 2 SO 4 electrolyte. The SC also retained 90 % of its initial capacitance even after 1000 charge/discharge cycles [111] …”

“…The SC also retained 90 % of its initial capacitance even after 1000 charge/discharge cycles. [111] From all these studies, it can be seen that the conducting carbons in these hybrid electrodes operate as efficient electron transfer routes that prevent the restacking of MoS 2 layers. In addition, the synergic effects exhibited by these binary and ternary composites boost the cycling stability and electrochemical performance of the electrodes.…”

Re Modulation of Metallic Ultrathin 2M-WS2 for Highly Efficient Hydrogen Evolution in Both Acidic and Alkaline Media

“…Notably, typical TMDs have a layered structure similar to graphite. The adjacent layers are weakly bound by van der Waals force, while the strong S-metal-S covalent bonds control the inner frame of the layer. − This unique structure endows TMDs with unique exfoliative characteristics and plenty of tunable active sites, which can be modulated to improve the electron transfer property, enhance the activity, and accelerate the catalytic reaction. ,− Compared with typical MoS 2 catalyst, WS 2 has longer W–S bonds with relatively small structural lattice stress and higher hydrogen adsorption activity on S-terminated edge sites, which is regarded as a promising HER electrocatalyst. − Different coordination forms of WS 2 will produce a variety of phase structures, such as 3R (orthorhombic structure), 2H (hexagonal structure), and 1T (trigonal structure). ,− The Jahn–Teller distortion of octahedral coordination in 1T-phase WS 2 will further cause the phase transition to form a triangular cluster stacking 1T″′ structure and a zigzag chain-like 1T′ structure (2M phase). − …”