Preparation and comparison of polyaniline composites with lotus leaf-derived carbon and lotus petiole-derived carbon for supercapacitor applications

Biomass carbon is a class of economical and sustainable materials for supercapacitor electrode materials, while the low energy density restricts its development. Herein, lotus leaf-derived carbon (LLDC) and lotus petiole-derived carbon (LPDC) were prepared via carbonization and KOH activation processes. Then LLDC and LPDC were further modified with polyaniline to synthesize the polyaniline@lotus leaf-derived carbon (PANI@LLDC) and polyaniline@lotus petiole-derived carbon (PANI@LPDC) composites by the in-situ polymerization approach. The synthesized PANI@LPDC exhibited an ultra-large specific capacitance of 1332.5 F·g−1 at 0.3 A·g−1 and outstanding electrochemical stability of 89.2% after 5000 cycles in the KI active electrolyte (1 M H2SO4 + 0.05 M KI), showing better electrochemical performance than PANI@LLDC (1190.3 F·g−1 at 0.3 A·g−1; 87.1% after 5000 cycles). This is mainly due to the natural tubular structure of LPDC being more conducive to the movement of electrons, the introduction of Faradic capacitance by PANI and KI, and the porous structure of LPDC providing enough space for performing redox reactions. Moreover, a symmetric supercapacitor device assembled with two PANI@LPDC electrodes showed a superb energy density of 75.7 Wh·kg−1 at the power density of 540 W·kg−1. This study provides guidance for selecting different parts of biomass to prepare high-performance supercapacitor electrode materials.