Moiré Superlattice MXene Nanosheets Constructed from Twisted Hexagon-Ti₃AlC₂ by Microwave-Assisted Lewis Molten Salt Etching: Implications for Structural Stability in Electrochemical Energy Storage

Abstract

In order to solve the problem of instability of MXene nanosheet structure in electrochemical energy storage processes, inspired by the moireś uperlattice effect of magic angle graphene, a twisted hexagon-Ti 3 AlC 2 precursor was synthesized by an in situ reaction method using the molten pool effect of Lewis acid molten salt. In addition, moirésuperlattice MXene Ti 3 C 2 nanosheets with rotating moirépattern lattice structure were innovatively constructed by the substitution reaction etching of the twisted hexagon-Ti 3 AlC 2 precursor with different ionic Lewis acid salts and microwave-assisted etching. The microstructure evolution of moirésuperlattice Ti 3 C 2 nanosheets was characterized by a simple and intuitive method. The atomic arrangement and the rotating moirépattern were modeled. The formation mechanism and relationship between the rotation angle and rotating moirépattern were also analyzed. This contributes to the enrichment of the moirésuperlattice material family. It is expected to further promote the research progress of MXene nanomaterials in the field of electrochemical energy storage. KEYWORDS: MXene Ti 3 C 2 , moirésuperlattice, twisted hexagon-Ti 3 AlC 2 , microwave-assisted etching, electrochemical energy storage

Recent progress of MXene as an energy storage material

“…Adjusting the structural characteristics of MXene can not only be achieved by intervening in synthesis. Inspired by magic angle graphene, Wu et al successfully constructed double-layer twisted Ti 3 C 2 (Moiré superlattice MXene), 64,65 as shown in Fig. 14.…”

Stacking Order Engineering of Two-Dimensional Materials and Device Applications

“…On the other hand, the stacking engineering of layered materials can unleash the tremendous opportunities to create previously inaccessible structures for desired chemical functional properties. ,, For example, the energy storage capabilities of Ti 3 C 2 MXene are often hindered by structural collapse due to layer stacking, resulting in reduced capacitance. By mimicking the superlattice effect of magic angle graphene, Wu et al have created a more stable, hexagonal few-layered Ti 3 C 2 free-standing film through microscopical regulation of rotation mismatch. This not only mitigates structural issues but also greatly enhances Ti 3 C 2 ’s capacitance as a supercapacitor electrode under long charge–discharge cycles.…”

“…On the other hand, the stacking engineering of layered materials can unleash the tremendous opportunities to create previously inaccessible structures for desired chemical functional properties. ,, For example, the energy storage capabilities of Ti 3 C 2 MXene are often hindered by structural collapse due to layer stacking, resulting in reduced capacitance. By mimicking the superlattice effect of magic angle graphene, Wu et al have created a more stable, hexagonal few-layered Ti 3 C 2 free-standing film through microscopical regulation of rotation mismatch.…”

MXene-modified electrodes and electrolytes in dye-sensitized solar cells

“…MXenes are special structural and electrical two-dimensional (2D) transition metal carbides, nitrides, or carbonitrides. 13–35 They are created by carefully etching layers of MAX phases, where MAX stands for carbon or nitrogen, M for an early transition metal, and A for a group 13 or 14 element. 36,37 MXenes are appealing for various energy storage and conversion applications, including DSSCs, due to their high specific surface area, electrical conductivity, and tunable surface chemistry.…”