Applied Surface Science, Vol.469, 951-961, 2019
Effect of electrolytes and sonication times on the formation of graphene using an electrochemical exfoliation process
The exfoliation of graphite is an intriguing approach for simple, fast and large-scale production of graphene. In the present study, three types of electrolytes were investigated, namely an ionic liquid (H2SO4), aqueous acid (H3PO4) and inorganic salt ((NH4)(2)SO4). Different sonication times (15, 30, 45 and 60 min) at room temperature were used to assist the electrochemical exfoliation. The graphene that was produced was characterized by the zeta potential, surface electrical conductivity, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). From the XRD analysis, it was observed that the graphene flakes had a broad peak centred at 26.5 degrees, which corresponds to the (0 0 2) plane of graphene crystal. The FTIR spectrum revealed that the prominent peak was in conjunction with exfoliated graphene. The characteristic Raman bands were observed for the D, G and 2D bands and the ratio of I-2D/I-G was 1.7, which indicated that the exfoliated graphene was a multilayer structure. From the results, it was found that graphene obtained with the H2SO4 electrolyte that used a 45 min sonication time had the highest stability, best electrical conductivity, lowest crystallite size, fewer defects and lowest interlayer distance.