Nitrogen-doped hierarchical porous carbons from used cigarette filters for supercapacitors

Millions of tons of used cigarette filters (UCF) are worldwide discarded in the environment as toxic waste. This study provides a new application of UCF for energy storage in order to contribute to solution to environmental concerns by UCF. We have developed a facile method to fabricate nitrogen-doped hierarchical porous carbons by a combination of UCF and polypyrrole (PPy). The carbonization and activation of the as-obtained composite by KOH afforded the carbon material of very high surface area (3420 m(2)/g) with micro-, meso-, and macroporous structures. The nitrogen content measured by X-ray photoelectron spectroscopy was 2.34%, which is derived from PPy. The formed carbon showed large specific capacitance of 263 Fig at 1 A/g and good capacitance retention of 90% even after 5000 cycles at the current density of 5 A/ g. These excellent data are owing to the 3D hierarchical porous structure and nitrogen-doped functionality of the present carbon and UCF is regarded as a potential candidate of a carbon precursor for high-performance supercapacitors. Furthermore, this study affords a new way to recycle UCF with valuable applications, contributing to reduction of environmental pollution by UCF. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.