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

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 m2 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. The as‐prepared tomato‐leaf‐derived hierarchical porous activated carbon‐ and polyaniline‐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. 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.