Petroleum coke derived reduced graphene oxide as an electrocatalyst for water splitting

One of the by-products produced in the petroleum refinery industry is Petroleum coke or pet coke (PC). To make its use in the development of high-cost value-added carbon products apart from electrodes in steel and aluminium extraction is one of the areas of research interest among the scientific community. The present investigation optimized processing parameters to synthesize graphene oxide (GO) using the well-known Hummers method from different heat treated (450 °C, 1400 °C, and 2200 °C) PC. The derived GO was thermally reduced into the reduced GO (rGO). Both GO and rGO were characterized by various spectroscopic techniques to ascertain ultimate GO and rGO synthesis. The FE-SEM images demonstrated that the surface morphology of the GO and rGO is highly exfoliated and has a thin sheet-like structure that is synthesized from 2200 °C heat-treated PC. The HR-TEM image shows a few layers of sheet-like structure for both GO and rGO and the SAED pattern shows fused for GO and the hexagonal ring pattern for rGO, indicating the presence of both amorphous and crystalline structures. The obtained rGO possesses a low band gap (2.45 eV) that is attributed to the semiconducting behavior. BET analysis reveals that synthesized GO possesses a decent specific surface area (211.2 m2/g). The upshot shows that PC has the potential to replace the costly natural graphite for the synthesis of GO and rGO having excellent properties. The obtained rGO demonstrates excellent bifunctional electrocatalyst materials for hydrogen and oxygen evolution reactions (HER and OER). The rGO/Ni-Foam electrode shows a low overpotential of 169 mV for HER and 400 mV for OER at 10 mA/cm2 current density in 1.0 M KOH electrolyte solution along with the lowest Tafel slope of 108.23 mV/dec and 104 mV/dec for HER and OER respectively shows faster kinetic rate towards water splitting. This study displays the vast possibility of utilizing PC to synthesize value-added products and its application as an electrocatalyst.