Dual doping of sulfur and nitrogen induces hierarchical porous carbon from wastes medical masks for supercapacitor electrodes

Demand for battery and supercapacitor materials rapidly increases as energy storage deployments accelerate. Waste-based supercapacitors have become a point of interest to accommodate growing demand and awareness of environmentally friendly products. This work aims to examine how doping with sulfur and nitrogen affects the morphology and structure of porous carbon synthesized from waste medical masks and the electrochemical performances of the prepared electrodes. Nitrogen- and sulfur-doped porous carbon (a-C:NS) is successfully obtained by solvothermal and hydrothermal processes in an autoclave followed by chemical activation using potassium hydroxide (KOH) and a carbonization procedure. Sulfur- and nitrogen-doping increase the yield compared to the directly carbonized process of the waste medical mask. The a-C:NS sample has a porous feature, showing the presence of S, N, O, and dominant C elements and the formation of C-S and C-N bonds. The supercapacitor electrode prepared from a-C:NS shows an electric double layer capacitor (EDLC)-like characteristic with a high specific capacitance (CS) of 300 F/g at the scanning rate of 5 mV/s. This study shows a possible route to transform polypropylene waste into functional materials for supercapacitor electrodes.