Abstract
The increasing demand for sustainable, high-power, and cost-effective energy storage systems has driven extensive research into advanced electrode materials for electrochemical energy storage devices. Among these, supercapacitors have attracted significant attention due to their high-power density, long cycle life, and rapid charge-discharge capability. This doctoral thesis focuses on the design, synthesis, characterization, and application of bismuth-based nanostructured materials as efficient electrode materials for supercapacitor devices, with emphasis on their device performance and integration into functional electronic circuits.
A range of bismuth-based electrode materials, including carbon nitride-supported bismuth sulfide, nanostructured bismuth fluoride, and nanostructured bismuth phosphate, were synthesized using controlled chemical routes. Structural, morphological, and chemical characterization was performed using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy to confirm phase purity, crystallinity, surface chemistry, and nanostructural features.
The electrochemical performance of the synthesized materials was evaluated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in both three-electrode and two-electrode configurations. The bismuth-based materials exhibited pronounced pseudocapacitive behaviour, high specific capacitance, good rate capability, and excellent cycling stability in aqueous electrolytes. Symmetric and asymmetric supercapacitor devices were fabricated, with asymmetric configurations enabling an extended operating voltage window and improved energy density while maintaining stable long-term performance.
The practical applicability of the fabricated supercapacitor devices was further demonstrated through their integration into basic electronic circuits, including low-pass filters and oscillator systems. Overall, this thesis establishes bismuth-based materials as promising electrode candidates for high-performance supercapacitor applications and highlights their potential in multifunctional energy storage and low-power electronic systems.