Electrochemical Analysis Of Vanadium Doped Zinc Sulfide

This thesis investigates the structural, optical, and electrochemical properties ofvanadium-doped zinc sulfide (ZnS:V) nanoparticles synthesized via precipitationsynthesis for application as electrode materials in supercapacitors. ZnS, a widebandgap semiconductor with limited intrinsic conductivity and capacitance, wasdoped with varying concentrations of vanadium (0.3–1%) to enhance its electrochemicalperformance. X-ray diffraction (XRD) analysis confirmed the cubic sphaleritestructure with slight lattice distortions induced by vanadium incorporation,while UV–Vis spectroscopy revealed band gap modulation due to sp–d exchange interactionsand the Burstein–Moss effect. Scanning transmission electron microscopy(STEM) demonstrated well-dispersed nanoparticles with spherical morphology, andelectron paramagnetic resonance (EPR) spectroscopy detected characteristic signalsindicating successful doping and defect formation. Photoluminescence (PL)analysis showed defect-related emissions, supporting the presence of intrinsic anddopant-induced states influencing carrier recombination. Electrochemical characterizationwas performed using cyclic voltammetry (CV), potentiostatic electrochemicalimpedance spectroscopy (PEIS), and galvanostatic charge–discharge (GCPL) techniques.CV and Dunn analysis revealed a substantial increase in both capacitiveand diffusive contributions upon vanadium doping, attributed to enhanced redoxactivity and improved ion diffusion. PEIS results demonstrated a marked reductionin charge-transfer resistance and Warburg impedance in doped samples, indicatingimproved electronic conductivity and facile ion transport. Overall, vanadium dopingsignificantly enhanced the specific capacitance, rate capability, and charge storagemechanisms of ZnS electrodes. This study highlights the potential of defect engineering and vanadium doping as effective strategies to enhance the electrochemicalperformance of ZnS-based electrodes for high-performance supercapacitor applications.