Improved efficiency of liquid-phase shear exfoliation of expanded graphite with mica plates as bifunctional additives

Abstract

Liquid-phase shear exfoliation (LPSE) is a potential method of large-scale production of good-quality graphene. Obtaining few-layer (<10) graphene with large lateral sizes and high yields remains a challenging issue. Here, we report an improved LPSE processing method involving the addition of mica plates, which serve as bifunctional agents. With the addition of 100 g L⁻¹ of mica, the LPSE (9000 rpm/0.24 mm/1 h) of expanded graphite offers ∼100% few-layer graphene with average lateral sizes (ALSs) of ∼2.8 μm and yields of up to 27% (the highest ever reported). The graphene produced by LPSE without any additives, however, contains only ∼77% few-layer nanosheets, and has ALSs of ∼1.3 μm and yields of 8%. Significantly, the addition of SiO₂ microspheres as a comparison has almost no influence on the LPSE. The mica plates control the vector of fluids in LPSE and guide the oriented arrangement of the layered materials (e.g., expanded graphite), leading to significantly improved LPSE efficiency. 2D transition metal dichalcogenides (TMDs) with improved yields were also successfully prepared using LPSE with the addition of mica.