Sustainable production of MnO2/activated carbon hybrid electrodes from pomegranate peels for efficient energy storage

To meet the enhanced demand for renewable energy sources, high-performance and sustainable energy storage devices are needed. In this study, KOH activation and the controlled redox deposition of MnO2 at different mass loadings (10, 25, and 40 wt.%) were used to synthesize biomass-based activated carbon (AC) and hybrid AC/MnO2 electrodes from pomegranate peel biomass. The porous structure of the uniformly distributed MnO2 nanoparticles was confirmed by detailed structural analysis using field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, and X-ray diffraction (XRD) techniques. Electrochemical analysis was performed using a three-electrode system with 1M Na2SO4 as the electrolyte. The results showed that the AC/MnO2-25 electrode possessed the highest electrochemical response with a specific capacitance of 394 Fg-1 at 1 Ag-1, along with good rate capability and low internal resistance. Even after 5000 cycles, the capacitance retention was 94.5%. The results confirmed a good electrochemical response with a Coulombic efficiency of approximately 98%. The enhanced electrochemical response was due to the combination of high-surface-area activated carbon with MnO2 nanoparticles, which contributes to electric double-layer capacitance and pseudocapacitance. The results confirmed the suitability of pomegranate peel biomass as a sustainable source of biomass to produce high-performance electrode materials for the fabrication of high-performance supercapacitor devices.