Eco-friendly green synthesis of Fe-doped WS using neem leaf extract: unlocking large interlayer spacing for improved capacitance and rapid ion transport.

Iron-doped tungsten disulfide (Fe-WS) nanoparticles were synthesized a green method using neem leaf extract. X-ray diffraction (XRD) confirmed structural changes, with the formation of a hexagonal structure. The -spacing is increased by Fe doping (6.05-6.08 Å). Fourier-transform infrared (FTIR) spectroscopy identified W-S and S-S bond vibrations, crucial for material integrity. The Brunauer-Emmett-Teller (BET) analysis confirmed the increased surface area and pore radius as a result of enhanced ions diffusion. The morphology study through Scanning Electron Microscopy (SEM) revealed enhanced porosity of Fe-WS, as evidenced by the more granular and disordered structure. UV-vis spectroscopy (UV-vis) showed a blue shift and an increased energy band gap from 2.48 eV to 2.64 eV, indicating improved optical properties. Methyl blue (MB) dye adsorption spectra showed that the Fe-WS is porous, and as a result, more electrolyte adsorbs within the electrode. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) revealed enhanced specific capacitance and energy density. Electrochemical impedance spectroscopy (EIS) demonstrated a significant reduction in charge transfer resistance and a substantial increase in the ion diffusion coefficient. These findings underscore the potential of Fe-WS for high-performance energy storage devices.