Facile Synthesis of a Highly Value-Added High-Performance Carbon Material from Waste Masks for Advanced Supercapacitors

The practical use of supercapacitors necessitates the development of efficient carbon electrodes. Currently, the recycling of discarded masks (polypropylene, PP) produced during the COVID-19 epidemic has become a social problem that has attracted widespread attention. Converting these waste materials into high-performance electrode materials offers a sustainable and cost-effective solution, paving the way for resource-efficient energy storage technologies. Herein, through a simple sulfonation cross-linking strategy to improve the thermal stability of polypropylene (PP) molecular chains and followed NaOH activation, we successfully transformed the discarded masks into a highly value-added activated carbon material (SMAC). The process of sulfonation introduces oxgen-containing functional groups, which serves to improve both the wetting properties of the interface between the electrode and electrolyte, as well as contributes to the increase in pseudocapacitance. Therefore, the optimal SMAC-2 with a large specific surface area of 2629.7 m2 g–1 demonstrated an adequate specific capacitance of 338.1 F g–1 in 6 M KOH electrolyte, while maintaining a capacitance of 203.7 F g–1 even at a current density of 50 A g–1. In an organic electrolyte (1 M Et4NBF4/AN) with an expanded voltage window of 0–2.7 V, the SMAC-2 electrode delivered a specific capacitance of 138.1 F g–1 at 0.5 A g–1. Furthermore, the sodium-ion hybrid capacitor assembled with SMAC-2 and commercial hard carbon as the cathode and anode, respectively, reached an energy density of 117.3 Wh kg–1 at a power density of 257.3 W kg–1, highlighting the promising application prospects of the mask-derived activated carbon.