Reductant-free synthesis conditions for water-dispersible reduced graphene oxide

Reduced graphene oxide (rGO) is the demanded material for large-scale graphene applications due to the relative ease of preparing sufficient quantities with the desired properties. Herein, optimized preparation conditions for water-dispersible rGO using the one-step chemical exfoliation method are reported. The rGO samples were obtained from graphite under different controlled reaction conditions, i.e., temperature (120, 140, and 160 °C) and time (16, 20, and 24 hrs). The microstructural, chemical, wetting, and electrical properties of samples were characterized using Raman spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, contact angle measurement, current-voltage (I–V) characteristic, and electrochemical impedance spectroscopy (EIS), respectively. The Raman parameter (i.e., the ID/IG values) was used to assess the quality of rGO materials. Accordingly, rGO160@20 showed the smallest ID/IG value (0.57) compared to the rest of the samples, followed by rGO160@16 and rGO120@24 with 0.75 and 0.77 values, respectively. The observed broad and diffused peaks centered at 2θ = 25° from XRD are the finger-print characteristics of rGO samples. FT-IR (mainly due to -OH) and lower contact angle values (≤ 33 °C) analysis confirmed the hydrophilic nature of these samples. The samples' non-linear I-V characteristics were attributed to disordered dielectric barriers. The charge transfer resistances (Rct) at the electrode/electrolyte interface were 21.65 for rGO160@20 and 25.65 for rGO160@16 and rGO120@24. EIS analysis also confirmed the rGO samples have supercapacitor behavior. Experimental parameters' synergistic effects influenced sample microstructure. Optimal processing conditions of rGO samples were also achieved for energy storage and applications that need graphene water dispersion.