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

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 similar to 100% few-layer graphene with average lateral sizes (ALSs) of similar to 2.8 mu m and yields of up to 27% (the highest ever reported). The graphene produced by LPSE without any additives, however, contains only similar to 77% few-layer nanosheets, and has ALSs of similar to 1.3 mu m 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.