Direct evidence of exfoliation efficiency and graphene dispersibility of green solvents towards sustainable graphene production

Abstract

Achieving sustainable production of pristine high-quality graphene and other layered materials at low cost is one of the bottlenecks that needs to be overcome for reaching 2D materials applications at scale. Liquid Phase Exfoliation (LPE) in conjunction with N-methyl-2-pyrrolidone (NMP) is recognised as the most efficient method for both the exfoliation and dispersion of graphene. Unfortunately, NMP is neither sustainable nor suitable for up-scaling production due to its adverse impact on the environment. Here we show the real potential of green solvents by revealing the independent contributions of their exfoliation efficiency and graphene dispersibility to the graphene yield. By experimentally separating these two factors we show that the exfoliation efficiency of a given solvent is independent of its dispersibility. Here we show that isopropanol can be used to exfoliate graphite as efficiently as NMP. This finding is corroborated by the matching ratio between the polar and dispersive energy of graphite and that of the solvent surface tension. This direct evidence of exfoliation efficiency and dispersibility of solvents paves the way to developing a deeper understanding of the real potential of sustainable graphene manufacturing at scale.