Iron/vanadium co-doped tungsten oxide nanostructures anchored on graphitic carbon nitride sheets (FeV-WO3@g-C3N4) as a cost-effective novel electrode material for advanced supercapacitor applications

Abstract

In this work, we studied the effect of iron (Fe) and vanadium (V) co-doping (Fe/V), and graphitic carbon nitride (g-C₃N₄) on the performance of tungsten oxide (WO₃) based electrodes for supercapacitor applications. The lone pair of electrons on nitrogen can improve the surface polarity of the g-C₃N₄ electrode material, which may results in multiple binding sites on the surface of electrode for interaction with electrolyte ions. As electrolyte ions interact with g-C₃N₄, they quickly become entangled with FeV-WO₃ nanostructures, and the contact between the electrolyte and the working electrode is strengthened. Herein, FeV-WO₃@g-C₃N₄ is fabricated by a wet chemical approach along with pure WO₃ and FeV-WO₃. All of the prepared samples i.e., WO₃, FeV-WO₃, and FeV-WO₃@g-C₃N₄ were characterized by XRD, FTIR, EDS, FESEM, XPS, Raman, and BET techniques. Electrochemical performance is evaluated by cyclic voltammetry (CV), galvanic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). It is concluded from electrochemical studies that FeV-WO₃@g-C₃N₄ exhibits the highest electrochemical performance with specific capacitance of 1033.68 F g⁻¹ at scan rate 5 mV s⁻¹ in the potential window range from −0.8 to 0.25 V, that is greater than that for WO₃ (422.76 F g⁻¹) and FeV-WO₃ (669.76 F g⁻¹). FeV-WO₃@g-C₃N₄ has the highest discharge time (867 s) that shows it has greater storage capacity, and its coulombic efficiency is 96.7%, which is greater than that for WO₃ (80.1%) and FeV-WO₃ (92.1%), respectively. Furthermore, excellent stability up to 2000 cycles is observed in FeV-WO₃@g-C₃N₄. It is revealed from EIS measurements that equivalent series resistance and charge transfer values calculated for FeV-WO₃@g-C₃N₄ are 1.82 Ω and 0.65 Ω, respectively.