Eco-friendly Polypyrrole-coated Cocozelle Composites for Supercapacitor Application

Cocozelle is essentially consisted of hemicellulose and lignin with a hierarchically porous structure. Herein, cocozelle slices after freeze-drying were employed as green substrates to support the growth of polypyrrole (PPy) via a facile oxidative polymerization approach. The cocozelle surface was densely covered with sheet-like PPy due to the hydrogen bonding between PPy and cocozelle. The PPy/cocozelle composites could be facilely utilized as supercapacitor electrodes, which showed a high specific capacitance of 1108 F g−1 with an energy density of 70.5 Wh kg−1 and a power density of 398 W kg−1 at a charge/discharge current density of 0.8 mA cm−2 as well as desirable cycling life with a capacitance retention rate of 76.9 % after 1000 cycles. Moreover, 95.3 % of the initial specific capacitance obtained at 0.2 mA cm−2 could be reached as the current density increased to 1.6 mA cm−2. These results demonstrate that cocozelle could be used as a superior alternative biomass-derived substrate for the developments of eco-friendly and renewable energy storage devices.