Effects of hybrid surfactants on the quality and yield of graphene using a novel electrochemical-mechanical exfoliation process

In this study, a novel electrochemical–mechanical exfoliation (EME) process combined with hybrid surfactants was used to prepare graphene nanosheets (GNSs). The effects of hybrid surfactants and post-treatments on the yield and quality of the prepared GNSs were investigated. Before and after the EME process, X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy, and atomic force microscopy were conducted to evaluate the crystallinity, degree of defects, oxygen-to-carbon (O/C) ratio, surface morphology, size, and thickness of graphite powder and the prepared GNSs, respectively. The experimental results revealed that the maximum yield of the GNSs was 19.68% when 1 wt.% polydimethyldiallylammonium chloride (PDDA) and 0.005 wt.% sodium dihexyl sulfosuccinate (SDSS) were mixed in deionized water for graphite pretreatment and high-speed shear exfoliation and when 1 wt.% PDDA and 0.01 wt.% SDSS were mixed in H₂SO₄ solution for electrochemical intercalation. The lowest O/C ratio, highest I_2D/I_G ratio, and lowest I_D/I_G ratio of the supernatant centrifuged at 3000 rpm were 1.12, 1.085, and 0.274, respectively. The FE-SEM images of the GNSs clearly indicated the effectiveness of exfoliation. Moreover, the average diameter and thickness of the prepared GNSs were approximately 5.2 µm and 2.4 nm, respectively.