Binder-free supercapacitor electrode with composite of graphene quantum dots and gold nanoparticles

We fabricated binder-free energy storage supercapacitor using two-dimensional graphene quantum dots (GQDs) and a composite of GQDs and gold nanoparticles (Au NPs) through facile hydrothermal and photochemical methods. The structures were analyzed using X-ray diffractometry and Raman spectroscopy , while transmission electron microscopy was used to observe their morphologies. Cyclic voltammetry , galvanostatic charging/discharging, and electrochemical impedance spectroscopy were used to investigate the electrochemical properties . Our findings suggest that the GQDs/Au nanocomposite demonstrates a higher specific capacitance (480 F/g) in comparison to GQDs (203 F/g). The nanocomposites exhibited a specific power of 106 W/kg and a specific energy of 10.6 Wh/kg at a current density of 1 A/g. Moreover, the nanocomposite displayed reasonable charge/discharge stability after 2000 charge-discharge cycles with a capacitance retention of ~79 %. Besides, a density functional theory study showed that an internal electric field is formed across the interface of Au and graphene, which is beneficial for charge storage. • Synthesized GQDs and GQDs/Au composite for supercapacitor energy storage. • Higher specific capacitance (480 F/g) of GQDs/Au nanocomposite vs. GQDs (203 F/g). • Nanocomposites exhibit 106 W/kg power, 10.6 Wh/kg energy at 1 A/g current density. • Reasonable charge/discharge stability after 2000 cycles with ~79 % retention. • Density functional theory calculations confirms electron transfer from GQDs to Au.