Sustainable recycling of waste polystyrene into hierarchical porous carbon nanosheets with potential applications in supercapacitors.

Herein, polystyrene waste was carbonized into mesoporous carbon nanosheets (CNS) using the template method. The pore structure of the obtained CNS was further tuned by KOH activation, resulting in the formation of hierarchical porous carbon sheets with a specific surface area of 2650 m ² g ^-1 and a pore volume of 2.43 cm ³ g ^-1 . Benefiting from these unique properties, in a three electrode system, the hierarchical porous carbon sheets displayed a specific capacitance of 323 F g ^-1 at 0.5 A g ^-1 in a 6 M KOH electrolyte, good rate capability (222 F g ^-1 at 20 A g ^-1 ) and cycle stability (92.6% of capacitance retention after 10 000 cycles). More importantly, an energy density of 44.1 Wh kg ^-1 was also displayed with a power density of 757.1 W kg ^-1 in an organic electrolyte. In this regard, the present strategy demonstrates a facile approach for recycling plastic waste into high value-added products, which will potentially pave the way for the treatment of plastic waste in the future.