Controlling of Crystal Facets by Dysprosium-Modified WO₃/Carbon Nanofibers Enhance the Flexible Supercapacitor Performance

Dysprosium-modified tungsten oxide/carbon nanofibers (Dy-WO₃/PCNFs) are fabricated via electrospinning combined with high-temperature calcination to synthesize a flexible, self-supporting electrode material that does not require a conductive agent or binder. XRD and TEM analyses showed that introducing dysprosium promoted the preferential growth of WO₃ crystals along the preponderance crystal planes involved in the electrochemical reaction, enhancing the exposure of the (002) and (200) crystal planes. Furthermore, DFT calculations demonstrated that the incorporation of Dy resulted in enhanced adsorption of Dy-WO₃ by PCNFs, with an adsorption energy of -1.21 eV. The Bader charge results indicate a transfer of 1.70 |e| from PCNFs to Dy-WO₃. DFT calculations demonstrate that strong adsorption facilitates charge adsorption/desorption, which contributes to charge transfer and enhances storage capacity. The prepared Dy-WO₃/PCNFs exhibited a high specific capacitance (557.28 F g^-1 at 0.5 A g^-1). Supercapacitors assembled with Dy-WO₃/PCNFs as the positive electrode and CNFs as the negative electrode have high energy density (29.8 Wh kg^-1 at a power density of 363.48 W kg^-1). This study demonstrates the successful synthesis of Dy-WO₃/PCNFs with exceptional electrochemical properties and offers significant insights into the design and application of flexible electrodes by incorporating dysprosium to modulate the crystal surface of WO₃.