Abstract
Nanomaterials are an important class of materials because they possess several enhanced physicochemical properties as compared to their bulk counterparts. In the present thesis, synthesis, characterization, and a few applications of tungsten oxide (WO3)-based nanomaterials are reported. WO3 and it’s hydrate (WO3·nH2O) have generated interest of research community for their applications in chromism, water splitting, photodegradation of organic contaminants, supercapacitor, and sensing. Here, the phase and size-controlled synthesis of hydrated WO3 is demonstrated via a simple precipitation method at room temperature. The as-synthesized hydrated WO3 and WO3 nanoplates are employed for the photocatalytic reduction of Cr(VI) under visible light irradiation and adsorption of methylene blue. The WO3·H2O and WO3 nanoplates are also tested as electrocatalysts for hydrogen evolution reaction. In addition, the morphology evolution of WO3 nanowires from WO3·H2O nanoplates in a solvothermal process is demonstrated. Those nanostructures are used as anode materials for photoelectrocatalytic (PEC) water splitting reaction. The photocurrent density of WO3 nanowires is found ~21 times higher than that of WO3·H2O nanoplates at 1.0 V versus saturated calomel electrode (SCE). The superior PEC performance of WO3 nanowires is justified on the basis of its one-dimensional morphology, large surface area, and small interfacial charge transfer resistance. Furthermore, a facile and green solvothermal approach is employed to synthesize graphene supported WO3
nanowires as an active electrode material for supercapacitor application. The graphene-WO3
nanowires nanocomposite with an optimized weight ratio has shown excellent electrochemical performance with specific capacitance of 465 F g1 at 1 A g1 and good cycling stability of 97.7% specific capacitance retention after 2000 cycles in 0.1 M H2SO4 electrolyte. A solid-state asymmetric supercapacitor is also fabricated which delivered an energy density of 26.7 W h kg1 at 6 kW kg1 power density. It could retain 25 W h kg1 at 6 kW kg1 power density after 4000 cycles. This thesis works primarily emphasize on the synthesis of WO3-based nanomaterials and their applications in environment remediation and electrochemical energy conversion/storage.
Keywords: WO3H2O; WO32H2O; WO3;nanoplates; nanowires; Cr (VI) detoxification;
hydrogen evolution; water splitting; asymmetric supercapacitor
