Supercapacitor performance of spherical nanoporous carbon obtained by a CaCO3-assisted template carbonization method from polytetrafluoroethene waste and the electrochemical enhancement by the nitridation of CO(NH2)2

How to properly dispose plastic wastes is still urgent and challenging for scientists nowadays. In this work, polytetrafluoroethene waste has been successfully converted into nanoporous carbon spheres by a simple template carbonization method, using CaCO3 as hard template. It is revealed that the carbonization temperature and the mass ratio of polytetrafluoroethene and CaCO3 play crucial roles in the determination of pore structures. The sample obtained with the ratio of polytetrafluoroethene-to-CaCO3 as 2:1 at 700 °C, the carbon-2:1 sample, exhibits BET surface area of 646.3 m2 g−1, and pore volume of 0.65 cm3 g−1. The resulting specific capacitance is 179.9 F g−1 when measured at 1 A g−1 in a three-electrode system, using 6 mol L−1 KOH as electrolyte. Next, to modify the pore structures as well as the resultant electrochemical behaviors, CO(NH2)2 has been added to make the carbon matrix nitrogen-containing. The sample produced with the mass ratio of polytetrafluoroethene, CaCO3 and CO(NH2)2 as 2:1:2 at 700 °C, the carbon-2:1:2 sample, exhibits BET surface area of 1048.2 m2 g−1, and pore volume of 1.03 cm3 g−1. As a consequence, its specific capacitance has been improved to be 237.8 F g−1 at 1 A g−1. The present CaCO3-assisted template carbonization method is simple, reproducible and scalable and can be readily extended to treat with other halogen-containing plastic wastes.