Enhancing the super-capacitive properties of Zinc Sulfide nanospheres by multivalent Vanadium dopant ions

Zinc sulfide materials doped with different vanadium concentrations were prepared using a chemical coprecipitation technique. The undoped and vanadium-doped ZnS nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, and UV-visible spectroscopy, which demonstrate that the samples have a small crystallite size with a well-defined homogeneous spherical structure ( ∼ 70 nm in diameter), and a small reduction of the band gap due to doping. The defect structure of the ZnS-based materials and oxidation state of the dopant ions were assessed using photoluminescence, electron paramagnetic resonance, and photoelectron spectroscopy, which indicate the coexistence of zinc and sulfur vacancies along with the doping vanadium ions that show a multivalence state of / / with an increased concentration of centers. The electrochemical performance of the synthesized nanocomposite was evaluated to determine its suitability for supercapacitor applications. The results indicate that moderate levels of vanadium doping, specifically within the 0.3 to 0.7% range, significantly enhance the electrochemical performances of ZnS-based Supercapacitors by simultaneously increasing conductivity and specific capacitance while maintaining structural stability. Doping ZnS with multivalence vanadium ions improved the specific capacitance values from ∼ 55 F/g to 90 F/g, thus increasing the energy and power densities to 12.5 Wh/kg and 1.46 kW/kg, respectively. The developed supercapacitor devices showed great cycling ability, with capacitance retention values above 95% for all materials, evidencing the potential of V-doped ZnS materials for applications in energy storage even without using any carbon-based booster materials.