Green synthesis of polypyrrole tubes using curcumin template for excellent electrochemical performance in supercapacitors

In this study, polypyrrole (PPy) having a unique hollow tubular structure was prepared through a simple and scalable one-step method of in situ chemical oxidative polymerization, employing curcumin, a plant-derived material, as a readily removable and eco-friendly template. PPy tubes (PPyT: PPyC1T1, PPyC1T2, PPyC1T4, PPyC2T2, and PPyC3T2) prepared under various conditions were then combined with functionalized carbon nanotubes (f-CNTs) to form freestanding electrodes. Among the tested composite electrodes, the PPyC3T2/f-CNT freestanding electrode exhibited the greatest morphological uniformity, a favorable hierarchical porous structure, the largest surface area, and excellent electrochemical properties. A record areal capacitance of 11830.4 mF cm(-2) at a current density of 2 mA cm(-2) was obtained for the PPyC3T2/f-CNT-thick freestanding electrode at a high mass loading of 30 mg cm(-2). In addition, a symmetric supercapacitor fabricated using the PPyC3T2/f-CNT-thick freestanding electrode exhibited an excellent areal capacitance (2732 mF cm(-2) at a current density of 2 mA cm(-2)), an outstanding cycling stability (retention of 118.18% of its initial capacitance after 12500 charge/discharge cycles), and a high energy density (242.84 mu W h cm(-2)) and maximum power density (129.35 mW cm(-2)). These characteristics highlight the potential applicability of PPyT/f-CNT freestanding electrodes in high-performance supercapacitors.