Gamma radiation assisted reduction of graphene oxide in Persea americana Mill. seed extract: characterization and oxygen reduction reaction in alkaline and neutral media

Abstract

Reduced graphene oxide (rGO) exhibits salient properties and thus are applicable in various fields. The major bottleneck to its applications, however, is the long synthesis method that also requires the use of toxic chemicals and high temperatures. Moreover, the surface area of the obtained rGO is often less than that of the starting material, graphene oxide (GO), a phenomenon that compromises its application. In the current study, gamma (γ) irradiation technique where aprotic solvents were substituted with Persea americana Mill. seed extract was investigated for its efficacy in reducing GO to rGO by optimizing the total irradiation dose. The successful synthesis of rGO was confirmed with UV-vis spectrophotometry (UV-vis), Fourier Transform Infrared (FTIR) spectroscopy, and Transmission Electron Microscopy (TEM), among others. The X-ray diffraction (XRD) suggested the dominace of reduction on GO with the icrease of the irradiation dosage to 100 kGy (rGO@100). Brunauer–Emmett–Teller (BET) showed that the green reduced GO surface area (60.345 m² g⁻¹) is 6 times larger than that of GO (9.586 m² g⁻¹). This was confirmed by an enhanced current response on the cyclic voltammetry (CV) of rGO@100 compared to that of GO. The average number of electrons transferred as calculated from the Kotouckey–Levich's (K–L) equation in alkaline and neutral media were 2.04 and 2.26 respectively. This indicates that the electrode (rGO@100/GCE) follows a 2e⁻ pathway mechanisms in both media. The 2e⁻ reaction pathway is also reported when conventional reduction methods are used, therefore the reduction method used in this study is potentially applicable for the development of advanced graphene-based composites for ORR.