Graphene exfoliation with supercritical fluids

Abstract

Graphene is an unconventional material with a two-dimensional hexagonal crystalline array of elemental carbon atoms and outstanding properties; accordingly, a desirable objective in the line of research of graphene is the development of novel and more productive methods of synthesis, validating its properties and applications. In our exploratory research, we have effectively exfoliated graphene from graphite using supercritical fluids (water, ethanol and carbon dioxide). The exfoliated graphene was properly characterized; via scanning electron microscopy, the morphology of graphene was observed; Raman spectra confirmed the exfoliation of graphene depicting the characteristic shift towards smaller Raman number in the 2D band (2676 cm −1) compared to that of graphite (≈ 2700 cm −1); transmission electron microscopy analysis exhibited the crystalline structure of graphene attesting also the expected transparency of exfoliated layers. Graphene exfoliation from graphite by supercritical fluids promises to be a simple large-scale method for graphene production.

Application of supercritical fluid in the synthesis of graphene materials: a review

“…By adjusting the operating temperature and pressure, SCFs can achieve low interfacial tension, high diffusivity, high compressibility and excellent surface wetting properties (Padmajan Sasikala et al 2016) that are suitable for graphene synthesis by diffusing in between layers and expand for exfoliation. Conventional SCFs that are commonly used in the process industry include N-methyl-2-pyrrolidone (ScNMP) (Rangappa, et al 2010), N,N-dimethylformamide (ScDMF) (Liu et al 2012), water (ScH 2 O) (Morales Ibarra, et al 2020), carbon dioxide (ScCO 2 ) (Xu et al 2015) and various alcohols (Seo 2013;Nursanto 2011;Zhang 2010). The discussion in this section only focuses on reported works of SCFs as penetrants in intercalating and exfoliating graphite into its 2D form whilst reduction mechanisms of graphene oxide with SCFs are discussed at length in the subsequent section.…”

A new method for the preparation of cobalt nanoferrite/graphene composite

“…Raman spectra of multilayer graphene samples usually show three characteristic peaks denoted D (1350 cm -1 ), G (1580 cm -1 ) and 2D (2690 cm -1 ) [14]. Moreover, it is worth mentioning that graphene can be differentiated easily from graphite by Raman spectroscopy, since graphene would have aa higher relative intensity in the 2D band compared to that of graphite along with a 2D band shift towards lower wave number compared to that of graphite Moreover, it is worth mentioning that graphene can be differentiated easily from graphite by Raman spectroscopy, since graphene would have aa higher relative intensity in the 2D band compared to that of graphite along with a 2D band shift towards lower wave number compared to that of graphite [15]. Unfortunately, the spinel CoFe2O4 phase cannot been clearly seen due to the large amount of graphene [17].…”

Electrochemically exfoliated graphite as a highly efficient conductive additive for an anode in lithium‐ion batteries

“…The EG prepared through an electrochemical method has high electrical conductivity due to the low content of oxygen functional groups and impurities on the surface. [15][16][17][18] In addition, a stable electrical pathway can be preserved by the multidimensional contact between the EG and other components (active material, binder, and the current collector). The volume expansion during the lithiation of the active material can be effectively suppressed based on its excellent mechanical properties.…”

“…Electrochemical exfoliation is one of the efficient methods for the mass production of high‐quality EG due to its simplicity and environmental friendliness. The EG prepared through an electrochemical method has high electrical conductivity due to the low content of oxygen functional groups and impurities on the surface 15–18 . In addition, a stable electrical pathway can be preserved by the multidimensional contact between the EG and other components (active material, binder, and the current collector).…”