Novel strategy for preparation of highly porous carbon sheets derived from polystyrene for supercapacitors

Polystyrene (PS) derived porous carbon sheets (CSs) were synthesized through the MgO template coupled with KOH activation. The influence of KOH ratio on the morphology, surface area and pore structure of the obtained carbon sheets was studied and discussed in details. Subsequently, the prepared carbon materials were used as the electrodes for symmetric supercapacitors. Benefiting from KOH activation, PCSs showed outstanding electrochemical performance using 1 M H2SO4 as the electrolyte. The optimal mass ratio of CSs:KOH was 1:3 (PCS-3). This sample displayed specific capacitances of 135 and 97 F g(-1) at the scan rate of 1 mV s(-1) and the current density of 1 A g(-1). An excellent rate performance of 82.9% retention even when current density increased up to 20 A g(-1) was detected. Moreover, the energy density of 3.4 W h kg(-1) with the corresponding high-power density of 250 W kg(-1) in the aqueous electrolyte was achieved. In particular, PCS-3 showed an excellent capacitance retention of 92.41% even after 10,000 charge/discharge cycles, clearly demonstrating the robust long-term stability.