Tuning electrochemical behaviors of N-methyl-2-pyrrolidone liquid exfoliated graphene nanosheets by centrifugal speed-based grading

We report on the study of the electrochemical behavior of liquid exfoliated graphene nanosheets (GS) with varied sizes and thickness by controlling centrifugal speed. GS were prepared via a solvent exfoliation and centrifugation separation method from graphite powder using N-methyl-2-pyrrolidone (NMP) as the solvent and with the assistance of sodium citrate. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra , UV–Vis spectra and particle size measurements were employed to characterize the size and structural changes of GS under different centrifugal speeds. And, the electrochemical properties of these GS materials like redox behaviors, standard heterogeneous rate constant ( k 0 ) and electrochemical impedance were studied using potassium ferricyanide as the probe. Our results suggested that the size and concentration show obvious effects on the electrochemical properties of the solvent exfoliated GS.