Date Seed-Derived Supercapacitor Electrodes in Aqueous Electrolyte: Unveiling High Capacity and Coulombic Efficiency

Date seeds, often considered byproducts of date fruit processing, represent a significant bio-waste stream. Despite their abundance, these seeds are underutilized and typically regarded as agricultural waste. Rich in carbon content, date seeds have the inherent potential to serve as precursors for hard carbon electrodes in supercapacitors. Free-standing electrodes were fabricated to enhance cyclic stability and improve Coulombic efficiency, showcasing superior electrochemical performance. The activation process with a 1:3 KOH-to-bio-char ratio yielded a specific capacitance of 204 F/g at 0.2A/g for the symmetric cell with an energy density of 6.5 Wh/kg and a power density of 47.70 W/kg, highlighting the effectiveness of this approach in advancing both structural integrity and electrochemical attributes. To elucidate the electrochemical performance of KOH-activated hard carbon, BET analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Raman Spectroscopy were employed. BET analyses revealed a higher surface area for the hard carbon activated with a 1:3 KOH ratio. This enhancement in structural integrity was further corroborated by cyclic voltammetry (CV) and charge-discharge curves, emphasizing the favorable electrochemical attributes of the proposed method. While previous investigations into date seed supercapacitors revealed promising results, achieving near 100% Coulombic efficiency remained challenging. In this study, the implementation of free-standing electrodes marked a significant advancement, resulting in a remarkable Coulombic efficiency of 99.97%. This nuanced approach underscores the effectiveness of our methodology in addressing and improving the Coulombic efficiency of date seed-derived supercapacitors.