Scalable Manufacturing of Large and Flexible Sheets of MXene/Graphene Heterostructures

Abstract

been reported as potential electrodes for energy storage. These 2D materials demonstrate unique properties, including high electronic conductivity, high capacity, flexibility, strength, and electrochemical stability. However, all of these materials have limitations in energy storage, such as the low electronic conductivity of oxides and the limited redox activity of graphene-based materials, and limiting charge storage capacity. [1a,7] The challenge, therefore, is to fabricate electrodes that will combine all of the aforementioned characteristics in one structure. Due to this challenge, efforts have been devoted to build heterostructures by stacking different 2D sheets to mitigate the weaknesses of each component. [1a] For example, heterostructures of graphene/TMD, [8] graphene/TMO, [9] graphene/phosphorene, [3a,b] etc., have been fabricated and exhibit enhanced energy storage capability compared to their individual building blocks.In recent years, 2D transition metal carbides, nitrides, and carbonitrides, known as MXenes, have emerged as an attractive class of materials due to their combined properties of metallic conductivity, good mechanical strength, and pseudocapacitive charge storage. [6,10] A variety of MXene-based electrodes have been developed and shown promising performance in supercapacitors, [11] Li-ion, [12] Li-S, [13] and other batteries. [14] Like other 2D materials, the restacking of MXene nanosheets decreases the performance of MXene-based electrodes by hindering electrolyte accessibility and ion transport. Additionally, the electrochemical properties of MXenes strongly depend on the surface chemistry; their surface terminations need to be well controlled to minimize irreversible capacity. [15] To fully utilize the energy storage capability of MXenes, one of the most promising strategies is to combine MXene nanosheets with other nanomaterials to form a hybrid/heterostructured architecture, which would inherit the advantages of individual building blocks while eliminating their shortcomings. [6,10,16] For example, numerous carbon nanomaterials, [11c,17] oxide nanoparticles, [18] and polymer molecules [19] have been incorporated Stacking different 2D materials is a promising strategy to fabricate heterostructures that combine the advantages and eliminate the associated shortcomings of individual building blocks. When used for energy storage, 2D heterostructures provide the opportunity to manufacture flexible and conductive paper electrodes, which require no binders, conductive additives, or current collectors. Here, 2D MXene/graphene heterostructured papers are manufactured by alternately stacking Ti 3 C 2 T x MXene and reduced graphene oxide (rGO) nanosheets using spray-assisted layer-by-layer assembly. Up to letter paper-sized free-standing films can be manufactured within half an hour of spraying. When used directly as anodes for Na-ion storage, the MXene/ rGO heterostructured films exhibit improved electrochemical performance compared to pure MXene and rGO films in terms of capacity, ...

Electrochemical Behavior of Ti3C2Tx MXene in Environmentally Friendly Methanesulfonic Acid Electrolyte

“…However,t his is not surprising as it was previously reported that MXenes can undergo redox reactions and exhibit pseudocapacitive behaviors. Although it was previously reportedt hat rate performance of MXene electrodes can be greatly improved if open architectures are used, such as macroporouss tructures, [16] vertically aligned nanosheets, [23] or compositesw ith spacers between layers, [24] it is not the goal of this work. In 1 m,4m,a nd 8 m aqueous MSA electrolytes, two redoxr eaction couples can be distinguished, whereas only one redox couplew ith broader peaks can be identified in neat MSA.…”

“…This is attributed to the factt hat horizontally restacked nanosheets impede high ion diffusivity through the electrode. Although it was previously reportedt hat rate performance of MXene electrodes can be greatly improved if open architectures are used, such as macroporouss tructures, [16] vertically aligned nanosheets, [23] or compositesw ith spacers between layers, [24] it is not the goal of this work.…”

Recent progress in graphene‐based electrodes for flexible batteries

“…E and F, Schematic and digital images of flexible 2D MXene/graphene films. Reproduced with permission from Reference . Copyright 2019, Wiley‐VCH.…”

“…graphene films could be obtained by chemical vapor deposition (CVD) and transferred to flexible substrates by a roll‐to‐roll transfer method . Very recently, Gogotsi's group fabricated 2D graphene‐based heterostructured papers by spray‐assisted layer‐by‐layer assembly (Figure E). The rGO dispersion and MXene colloidal solution were sprayed alternately onto the polypropylene membrane and the obtained heterostructured film showed excellent flexibility, without structural damage under different bending states (Figure F).…”

Layer-by-Layer Assembly of Two-Dimensional Materials: Meticulous Control on the Nanoscale

“…Furthermore, the rich surface chemistries that are accessible by well-dispersed 2D materials are obstructed if restacking is prevalent. 60 For example, MoS 2 transitions from an indirect to a direct band-gap semiconductor as its thickness is reduced to a monolayer, and LbL techniques have been demonstrated as a method to drastically improve photoluminescence efficiency as a result of controlled separation of flakes (Table 1). 56 LbL also allows for versatile structuring of 2D materials into three-dimensional (3D) architectures and onto particulate surfaces.…”