Impact of electrode drying time on capacitive performance of honey-derived graphene nanosheets for supercapacitors

Graphene nanosheets have a significant impact in the energy storage field, particularly in the realm of supercapacitors and capacitive deionization, due to their exceptional properties. This research aims to develop a facile method for preparing graphene nanosheets from biomass and examine the influence of the electrode drying time on the electrochemical properties of the prepared electrodes. Honey, as a carbon source, offers advantages over typical biomass because of its uniform composition, high carbon content, and ability for controlled low-temperature carbonization, which improves porosity and wettability. This chemical process was followed by KOH chemical activation with N₂ gas injection. The physical and chemical properties of graphene nanosheets were examined with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Transmission Electron Microscope (TEM), low-temperature nitrogen adsorption-desorption for isothermal characterization, zeta potential, and particle size measurements. The honey-based graphene nanosheets have a specific surface area of 1427 m² g⁻¹ and a pore volume of 0.654 cm³g⁻¹. Consequently, the electrochemical performance of the prepared electrodes was assessed via galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). However, the optimum drying time (24 h) had a significant effect on the specific capacitance of electrodes (maximum of 240 Fg⁻¹), which was achieved at a current density of 0.3 Ag⁻¹ when tested in a 0.5 M Na₂SO₄ aqueous electrolyte. These results present promising rate capability and competitive performance for supercapacitor applications compared with other graphene-based supercapacitor electrodes. Moreover, this sustainable and cost-effective method may enhance the performance of supercapacitor electrodes.