1D WO3@CNFs modified with sulphur for fabricating self-supported flexible supercapacitors with enhanced performance

The industrial sector relies on devices that can rapidly charge and discharge on a large scale. Supercapacitors (SCs) have demonstrated exceptional potential in fulfilling this critical role. In this study, we successfully fabricated a flexible self-supporting electrode of S-modified tungsten oxide carbon nanofibers (S0.075WO3@CNFs) using a combination of electrospinning and hydrothermal methods, eliminating the need for conductive agents and adhesives. The S0.075WO3@CNFs obtained after incorporating the S modification demonstrated enhanced electron transfer and exceptional electrochemical properties. Furthermore, density functional theory (DFT) calculations revealed that the introduction of S enhances the interactions with W and O, resulting in a pronounced interaction between S0.075WO3 and CNFs, characterised by an adsorption energy of -4.52 eV. These results suggest that the adsorption of S0.075WO3 and CNFs resulted in enhanced durability, facilitating charge adsorption/desorption processes and involving significant charge transfer. This unique interaction promotes the oxidation state change of W, accelerating the conversion between W4+ and W6+ and creating a triangular electron transfer between W, O, and S. The S-0.075-WO3@CNFs exhibited the best electrochemical performance, with an optimum specific capacitance value (718.33 F g(-1) at 0.5 A g(-1)) that was 2.4 times higher than that of the WO3@CNFs (298.08 F g(-1) at 0.5 A g(-1)). Moreover, by utilising S-0.075-WO3@CNFs as the cathode, CNFs as the anode, and polyvinyl alcohol (PVA)/KOH gel as the solid electrolyte, the fabricated flexible asymmetric supercapacitor (ASC) exhibits a remarkable energy density of 46.45 Wh kg(-1) and an impressive power density of 375.01 W kg(-1). The present study introduces a novel perspective on enhancing electrode performance through S modification of WO3, offering valuable insights into the field of energy.