Scalable exfoliation and dispersion of few-layer hexagonal boron nitride nanosheets in NMP-salt solutions

Efficient and large-scale production of boron nitride (h-BN) nanosheets is very important for their applications. Here, we have developed a facile strategy for liquid-phase exfoliation of h-BN nanosheets in organic electrolyte solutions where N-methyl-pyrrolidinone (NMP) is used as an organic solvent, and sodium citrate, sodium tartrate, ammonium oxalate, potassium sodium tartrate or ethylenediaminetetraacetic acid disodium salt is used as a salt. It is found that the dispersion content of h-BN nanosheets has been greatly improved by using organic electrolyte solutions. For example, by addition of ethylenediaminetetraacetic acid disodium salt into NMP, the content of the exfoliated h-BN is 36 times that in neat NMP. Furthermore, approximately 85% of the h-BN nanosheets obtained in such a strategy is 1-4 layers. Mechanism study indicates that the strength of Lewis basicity of anion and size of cation of the salts play an important role in the exfoliation of h-BN by organic electrolyte solutions. The liquid exfoliation strategy reported here shows great promise for the mass production of high-quality few-layer h-BN nanosheets.