Biomass-Derived Potassium-Doped Reduced Graphene Oxide-like Material for High-Performance Supercapacitors: Experimental and Computational Analysis

Abstract

With the growing energy demand and limited resources, the development of costeffective and efficient materials is essential. Among these, carbon-based nanomaterials offer promising characteristics for energy applications. Bio-based carbon nanomaterials are particularly promising for energy storage devices like supercapacitors due to their sustainability and performance characteristics. This study presents a cost-effective method for synthesizing bio-based reduced graphene oxide (rGO)-like material using persimmon fruit, a readily available resource in east Asia. A clean two-step thermal process was employed to synthesize rGO-like material, eliminating the need for toxic chemicals commonly used in conventional approaches. The material is derived from persimmon and naturally doped with potassium, which contributes to enhanced supercapacitor performance. A systematic optimization of carbonization temperature (600-1000 °C) and heating rate (5-15 °C min⁻¹) was carried out using residual yield analysis, Raman spectroscopy, XRD, and TGA, identifying 800 °C and 10 °C min⁻¹ as the optimal synthesis conditions. Density Functional Theory (DFT) calculations were performed to elucidate the electronic structure and validate the improved electrochemical properties observed experimentally. Electrochemical analysis in a three-electrode system revealed a high specific capacitance of 302.8 F/g at a scan rate of 2 mV/s. Furthermore, a symmetric supercapacitor device fabricated using the synthesized material demonstrated exceptional performance, with a specific capacitance of 322 F/g, an energy density of 44 Wh/kg, and a power density of 372 W/kg at a current density of 0.2 A/g. Remarkably, the device maintained its original capacitance even after 5000 charge-discharge cycles. These results highlight the potential of potassium-doped, biomass-derived rGO-like materials as effective electrode materials for supercapacitor applications.