Building Close Ties Between CO₂ and Functional Two‐Dimensional Nanomaterials with Green Chemistry Strategy

Abstract

Two‐dimensional nanomaterials represented an emerging class of nanomaterials that have attracted dramatically increasing attention in both academia and industries. With the development of green chemistry, supercritical carbon dioxide with unique properties can be used as excellent reaction media for two‐dimensional nanomaterials preparation and processing. In this review, we summarize the recent state‐of‐art progress on the ultrathin two‐dimensional nanomaterials fabricated with the assistance of supercritical carbon dioxide, including carbon dioxide‐induced liquid exfoliation, phase engineering, and the formation of amorphous materials, as well as the construction of heterostructures and novel functional nanomaterials. Based on the potential and versatility of supercritical carbon dioxide in materials processing and synthesis, we will also give some personal perspectives on the existing challenges and future research directions.

Supercritical CO2‐assisted Fabrication of Two‐dimensional Graphdiyne Oxide Nanosheets for Enhanced Photothermal Conversion

“…Supercritical CO 2 (SC CO 2 ) is an environmentally friendly solvent with the low viscosity, zero surface tension, and high gas‐like diffusivity, which can be used to exfoliate two‐dimensional (2D) layered materials with high‐yield [27–28] . Based on the driving forces stemming from the phase inversion, graphene and graphene analogues such as BN, MoO 3 , WO 3 , MoS 2 , WS 2 , layers can be efficiently exfoliated from their corresponding bulk phases [29–31] .…”

Supercritical Fluid‐Facilitated Exfoliation and Processing of 2D Materials

“…SCFs that are gaseous at ambient conditions offer an advantage of evaporation after decompression to ambient conditions. It has been used for exfoliating 2D crystals [18] because it is cheap, abundant, nontoxic, nonflammable, recyclable, and environmentally friendly. ScCO 2 is a well-known SCF with a readily accessible critical point ( Table 2).…”

“…ScCO 2 is a well‐known SCF with a readily accessible critical point (Table ). It has been used for exfoliating 2D crystals because it is cheap, abundant, nontoxic, nonflammable, recyclable, and environmentally friendly. ScCO 2 can provide a repulsive free energy barrier to inhibit exfoliated sheets from re‐stacking, affording good stability while maintained in a supercritical state.…”

Molecular Understanding of Charge Storage in MoS2 Supercapacitors with Ionic Liquids

“…2H-MoS 2 has the property of hexagonal symmetry, which is dominant in nature, while 1T-MoS 2 presents trigonal symmetry due to the sulfur transfer in its structure. [21] These two phases can be reversibly transferred by changing the stacking order of each layer. Compared with 2H-MoS 2 with a bandgap between 1.3-1.9 eV depending on the number of layers, [19] 1T-MoS 2 provides a nearly 10 7 times higher electrical conductivity (10-100 S cm −1 ), [18] which is beneficial for electron transfer.…”