Transforming polystyrene waste into 3D hierarchically porous carbon for high-performance supercapacitors

Polystyrene (PS) is usually discarded as a solid waste after a short lifespan. Thus the disposal of waste PS is an inevitably worldwide issue because of their stable and non-biodegradable nature. Herein, a facile method was proposed to carbonize PS waste into novel three-dimensional (3D) hierarchically porous carbon using Fe₂O₃ particles as both catalyst and template. Furthermore, KOH activation was applied to generate microporous and mesopores on the wall of macropores. As a result, the obtained 3D hierarchically porous carbon exhibits a high specific capacitance of 284.1 F g^-1 at 0.5 A g^-1 and good rate performance of 198 F g^-1 at 20 A g^-1 in a three-electrode device. Moreover, the assembled symmetrical capacitor displays a high energy density of 19.2 W h kg^-1 at the power density of 200.7 W kg^-1 in aqueous electrolyte. Therefore, the present research develops a sustainable way to recycle waste plastics into 3D hierarchically porous carbon for supercapacitors.