Prospects of Supercritical Fluids in Realizing Graphene‐Based Functional Materials

Abstract

Supercritical-fluids science and technology predate all the approaches that are currently established for graphene production by several decades in advanced materials design. However, it has only recently been proposed as a plausible approach for graphene processing. Since then, supercritical fluids have emerged into contention as an alternative to existing technologies because of their scalability and versatility in processing graphene materials, which include composites, aerogels, and foams. Here, an overview is presented of such materials prepared through supercritical fluids from an advanced materials science standpoint, with a discussion on their fundamental properties and technological applications. The benefits of supercritical-fluid processing over conventional liquid-phase processing are presented. The benefits include not only better performances for advanced applications but also environmental issues associated with the synthesis process. Nevertheless, the limitations of supercritical-fluid processing are also stressed, along with challenges that are still faced toward the achievement of the great expectations from graphene materials.

Preparation and Characterization of Graphene Oxide Aerogels: Exploring the Limits of Supercritical CO2 Fabrication Methods

“…[12][13][14][15][16][17][18][19][20][21][22] In constructing graphene structures, scCO 2 has only recently been proposed as ap lausible medium for exfoliation and drying. [23][24][25][26] In as tep forward, the methodd evelopedi n this work is devoted to the formulation of stable 3D GO aerogel structures by direct self-assembly of dispersed GO sheets in ethanol in only one step, using exclusively low-temperature scCO 2 technology and avoiding the use of any cross-linking agent. The developed scCO 2 process is optimizedf or different experimental parameters, such as temperature and CO 2 flow.…”

Advances in Subcritical Hydro‐/Solvothermal Processing of Graphene Materials

“…The supercritical exfoliation of graphite using supercritical fluids (which are solvents at pressure and temperature higher than its critical point) exceeds in number among solvothermal graphite exfoliation reports. This was reviewed in details previously . Nevertheless, the solvothermal subcritical exfoliation of graphite (using solvents below their critical point and above the boiling point in a confined volume) is also shown comparably efficient.…”

“…However synthesis of graphene and of its related materials is still in infancy despite many promising reports which convincingly illustrate the great potential of solvothermally synthesized/exfoliated graphene sheets, heteroatom doped/reduced graphene sheets, graphene quantum dots, and graphene composites/aerogels/fibers ( Scheme ) . Very recently, we have reviewed the supercritical fluids methods for the processing of graphene and graphene‐based materials in detail . While, supercritical fluids methods require high temperature and high pressure stable reactors, subcritical hydro‐/solvothermal synthesis provides a low temperature alternative.…”

Exfoliation of 2D Materials for Energy and Environmental Applications

“…A supercritical fluid is a substance at conditions above its critical temperature and pressure and thus has characteristics between those of a liquid and gas; it can dissolve materials like a liquid and effuse through solids like a gas (Table ) . Importantly, the major physical properties of supercritical fluids affecting the exfoliation of 2D materials, such as solvation, polarity, and surface tension, are tunable by adjusting the temperature, pressure, or both or by the addition of a co‐solvent.…”