Plastic Waste-Upcycled Nanoporous Carbon-MoS2 Composite for High-Performance Supercapacitor Electrode-Enriched Pseudocapacitive Behavior via Interfacial Bonds

Abstract

The global energy crisis, along with the accumulation of plastic waste (PW), has increased the upcycling of PW for energy storage. Here, we synthesize and investigate the supercapacitance (SC) properties of a waste polyethylene terephthalate-derived porous activated carbon-MoS2 composite via a one-pot hydrothermal method (HT-W-PET-AC-MoS2) and by physical mixing (PM-W-PET-AC + MoS2). The HT composite with 80 wt % MoS2 exhibits the highest specific capacitance (Csp) of 445 and 272 F g–1 at 0.50 and 1 A g–1, whereas W-PET-AC, MoS2, and the PM-analogue deliver 188, 190, and 295 F g–1 at 0.50 A g–1. Trasatti’s analysis reveals 93% electrochemical double-layer capacitor (EDLC) contribution for the PM and 47% pseudocapacitance (Cpseudo) and 53% EDLC in HT. The enhancement in the Csp value (51% increase) of HT compared to PM is attributed to additional conductivity by electron transfer via chemical bonds between W-PET-AC and MoS2, activating the Cpseudo of MoS2. Conversely, the cyclic stability showed that the PM composite exhibited 100% capacitance retention, whereas HT showed only 63% over 5000 cycles. Thus, this study provides clear evidence that the pseudobehavior of MoS2 in the HT-W-PET-AC-MoS280 composite is enriched through bond formation and emphasizes the role of molecular-level electron transfer in activating pseudobehavior in the HT composite, while the PM composite exhibited lower Csp and higher cyclic stability, indicating EDLC dominance. Further, a two-electrode symmetric coin cell device is fabricated for HT and PM, which delivers an energy density (Ed) of 23.20 Wh kg–1 and a power density (Pd) of 4896 W kg–1 for HT and 12.10 Wh kg–1 and 4800 W kg–1 for PM.