Sheet-like ZnCo2O4 microspheres and pomelo peel waste-derived activated carbon for high performance solid state asymmetric supercapacitors

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Reddygunta, Kiran Kumar Reddy and Šiller, Lidija and Ivaturi, Aruna (2024) Sheet-like ZnCo2O4 microspheres and pomelo peel waste-derived activated carbon for high performance solid state asymmetric supercapacitors. Sustainable Energy and Fuels, 8 (12). pp. 2751-2761. (https://doi.org/10.1039/D4SE00182F)

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Abstract

A novel asymmetric supercapacitor based on zinc cobalt oxide (ZnCo 2O 4) as a positive electrode and pomelo peel-based activated carbon (PPAC-4) as a negative electrode was fabricated. ZnCo 2O 4 was synthesized using hydrothermal method and shows a distinct sheet-like structure clubbed together to form microspheres. PPAC-4 was synthesized via the chemical activation of pomelo peel hydrochar using KHCO 3 as the activation agent. The as-prepared ZnCo 2O 4 microspheres displayed maximum specific capacitance of 422 F g −1 at an applied current density of 1 A g −1, whereas PPAC-4 demonstrated a capacitance of 356 F g −1 at a current density of 1 A g −1. Moreover, the novel ZnCo 2O 4//PPAC-4 asymmetric solid-state supercapacitor with hydroxyethyl cellulose/potassium hydroxide (HEC/KOH) gel electrolyte displayed maximum operating voltage of 1.6 V with a superior energy density of 29.8 W h kg −1 at a power density of 796.3 W kg −1. Besides, a long-term cycling stability of 83% was achieved after 10 000 charge/discharge cycles, indicating its promise for future energy storage applications.

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