Transforming waste polystyrene foam into N-doped porous carbon for capacitive energy storage and deionization applications

We have utilized cheap and readily available expanded polystyrene (EPS) foam waste as a raw material for the synthesis of a hypercrosslinked polymer. Using this polymeric scaffold, we have synthesized a series of nitrogen-doped porous carbons (PSC-3-X) via KOH activation at different temperatures. The optimized carbon material (PSC-3-700) exhibits a specific surface area of 810 m(2) g(-1) and optimum porosity suitable for capacitive applications such as supercapacitors and capacitive deionization. Moreover, the high nitrogen (5.23%) and oxygen (8.93%) contents present in the material enhances the electrochemical performance. PSC-3-700 exhibits the highest specific capacitance of 327 F g(-1) at 1.0 A g(-1) in 1 M H2SO4 aqueous electrolyte and 100% capacitance retention even after 10,000 charge-discharge cycles. It also displays a high electrosorption capacity of 34.8 mg g(-1) for 500 mg L-1 NaCl solution at an applied voltage of 1.6 V in capacitive deionization application. The charge storage mechanism and electrosorption kinetics of the material have been investigated in detail.