A High‐Energy Asymmetric Supercapacitor Based on Tomato‐Leaf‐Derived Hierarchical Porous Activated Carbon and Electrochemically Deposited Polyaniline Electrodes for Battery‐Free Heart‐Pulse‐Rate Monitoring

Abstract

Abstract A simple and scalable method to fabricate a novel high‐energy asymmetric supercapacitor using tomato‐leaf‐derived hierarchical porous activated carbon (TAC) and electrochemically deposited polyaniline (PANI) for a battery‐free heart‐pulse‐rate monitor is reported. In this study, TAC is prepared by simple pyrolysis, exhibiting nanosheet‐type morphology and a high specific surface area of ≈1440 m 2 g −1 , and PANI is electrochemically deposited onto carbon cloth. The TAC‐ and PANI‐ based asymmetric supercapacitor demonstrates an electrochemical performance superior to that of symmetric supercapacitors, delivering a high specific capacitance of 248 mF cm −2 at a current density of 1.0 mA cm −2 . The developed asymmetric supercapacitor shows a high energy density of 270 µWh cm −2 at a power density of 1400 µW cm −2 , as well as an excellent cyclic stability of ≈95% capacitance retention after 10 000 charging–discharging cycles while maintaining ≈98% Coulombic efficiency. Impressively, the series‐connected asymmetric supercapacitors can operate a battery‐free heart‐pulse‐rate monitor extremely efficiently upon solar‐panel charging under regular laboratory illumination.