Upcycling food waste into activated hydrochar: A sustainable and high-performance electrode material for supercapacitors

Abstract

The transition towards sustainable energy sources necessitates advancements in energy storage technologies. This study addresses environmental concerns by transforming waste materials-specifically, using food waste (FW) as a precursor and landfill leachate (LL) as a moisture source in hydrothermal carbonization-to produce hydrochar. This hydrochar is subsequently activated and evaluated for its electrochemical performance. Thermal and chemical activation methods were employed to augment the surface properties of the hydrochar. Various characterization techniques, including CHNS, FESEM, FTIR, XRD, and BET, were utilized to comprehend the impact of the thermal and chemical activation on the morphology and physicochemical properties of the hydrochar. Electrochemical experiments were performed to evaluate the energy storage capabilities of the fabricated electrodes. The findings demonstrate that chemically activated hydrochar based electrodes exhibit superior electrochemical performance compared to thermally activated ones, showcasing nearly double specific capacitance values and enhanced cyclic stability. The symmetric cell based on chemically activated hydrochar demonstrates a specific capacitance of 362.5 F g⁻¹, along with impressive cyclic stability. It retains approximately 95 % of its capacitance after 2000 cycles, with over 98 % coulombic efficiency maintained throughout. Additionally, this cell achieves energy density of 32 Wh/kg at 800 W/kg power density. This remarkable performance of chemically activated electrodes highlights the potential of activated hydrochar derived from food waste as a sustainable and high efficiency material for supercapacitor applications.