Comparative electrochemical performance evaluation of chemically (CRG) and hydrothermally (HRG) reduced graphene oxide as supercapacitor electrode material

Graphene was synthesized from graphene oxide (GO) precursor using two distinguished methods, namely, chemical (CRG) and hydrothermal (HRG) reduction. Electrochemical characterizations were performed in three- and two-electrode configurations. In 3-electrode studies, HRG and CRG have shown specific capacitances of 464 and 272 F g(-1), respectively, in 0.5 M H2SO4 solution, whereas in 2-electrode studies, HRG had shown a high specific capacitance of 124 F g(-1) compared to 72 F g(-1) of CRG in 6 M KOH solution. HRG had shown a high energy density of 3.5 Wh kg(-1), at a power density of 3 kW kg(-1). Further, the HRG has retained 81.6% of capacitance during its endurance study of 5000 cycles at 2 A g(-1), whereas CRG had retained 78.1%. The superior performance of HRG may be attributed to the efficient hydrothermal method adopted and resulted in large graphene edges, defects, high surface area, wettability, and low impedance.