▎ 摘　　要

The yield of graphene sheets from supercritical N,N-dimethylformamide (DMF) exfoliation of natural graphite is not high. It was found that using natural graphite which had been slightly treated by nitric add as a starting material for supercritical DMF exfoliation could enhance the yield of graphene sheets and maintain high quality (with the least defects). The yield of graphene sheets is 1.5 times greater than that from supercritical DMF exfoliation of natural graphite. Raman result indicates that the I-D/I-G of graphene sheets is 0.19. The atomic force microscopy image shows that the thickness of graphene sheets is 0.72 nm. Moreover, the possible mechanism of supercritical DMF exfoliation of nitric acid slightly treated natural graphite (NT-NG) is proposed.