Zinc Oxide/Multiwalled Carbon Nanotubes Composites Modified with Bowstring Hemp for Enhanced Supercapacitive Performance

Abstract This paper describes an ecofriendly and cost‐effective method for the synthesis of high‐performance energy storage materials through biogenic synthesis of zinc oxide–modified multiwalled carbon nanotube (ZnO/MWCNT) nanocomposites. Calotropis gigantea (bowstring‐hemp) leaf extract was employed as a biogreen reducing and capping agent to synthesize ZnO/MWCNT composites with varied MWCNT loadings of 1%, 2%, and 3%, labeled as ZOM‐1, ZOM‐2, and ZOM‐3, respectively. Structural integrity and mesoporous character of the materials were confirmed by thorough characterization with XRD, FTIR, FESEM, BET, and HRTEM. Among the samples, ZOM‐2 (ZnO:MWCNT = 1:2) possessed the maximum surface area of 70.419 m²/g and an excellent specific capacitance of 563.19 F/g at a scan rate of 1 A/g. It retained 98% of the capacitance even after 10,000 charge–discharge cycles at 10 A/g, which indicates excellent stability. Apart from that, ZOM‐2 also registered a power density of 364.5 W/kg and an energy density of 63.35 Wh/kg. These findings are promising in C. gigantea‐aided green synthesis as a process for the fabrication of sustainable, cost‐efficient, and high‐performance supercapacitor materials for next‐generation energy storage devices.