Metal Doped Nanocomposites of Tin Dioxide (SnO2) and Zinc Oxide (ZnO) for Photocatalytic Removal of Organic Dye and CuO-SnO2/rGO Hybrid Nanocomposite for Supercapacitor Applications

Abstract

In this dissertation work, Cu-SnO2/ZnO and Co3O4/Sn-ZnO nanocomposite was synthesized using a simple sol-gel method for efficient photocatalytic removal of methylene blue dye in an aqueous basic medium, and hydrothermally synthesized CuO-SnO2/rGO hybrid composite for supercapacitor applications. The structural, optical, morphological, and compositional properties of both Cu-SnO2/ZnO and Co3O4/Sn-ZnO nanocomposite were studied using different spectroscopic techniques. The XRD results of Cu-SnO2/ZnO nanocomposite show that SnO2 was tetragonal rutile and ZnO was hexagonal wurtzite which is similar to the HRTEM and SAED. The crystallite sizes of Cu-SnO 2, SnO2/ZnO and Cu-SnO2/ZnO were decreased compared to the pristine SnO2. The XRD result of Co3O4/Sn-ZnO nanocomposite revealed hexagonal structured ZnO and cubic spinel structure of Co3O4 were fused together to form it, and its crystallite size was greater than the constituent pristine oxides. In CuO-SnO2/rGO hybrid composite, the tetragonal rutile structure of SnO2 amalgamated with monoclinic structure of CuO. The simultaneous incorporation of CuO and rGO restrained the crystal growth of SnO2 host without changing its preferential growth directions. The Uv-DRS analysis showed that the band gap energy of SnO2 and ZnO hosts were reduced after modifications. PL analysis exhibited a higher defect density, strong quenching and lower swift of charge carriers in Cu SnO2/ZnO, Co3O4/Sn-ZnO and CuO-SnO2/rGO composites. The Fourier Transform Infrared (FTIR) spectroscopy identifies the functional groups attached to Cu-SnO2/ZnO and Co3O4/Sn-ZnO nanocomposites. The EDS results of Cu-SnO2/ZnO and Co3O4/Sn-ZnO nanocomposites revealed the presence of all its components. The morphology of both Cu-SnO2/ZnO and Co3O4/Sn-ZnO nanocomposites were investigated by SEM. The TEM, HRTEM and SAED analysis further confirmed the XRD result, and polycrystalline nature of the synthesized nanomaterials. The photocatalytic efficiencies of Cu-SnO2/ZnO and Co3O4/Sn-ZnO nanocomposite photocatalysts were 78 % and 95.1% recorded for MB dye removal. The enhancement of their photocatalytic performance compared to the pristine oxides could be attributed to more absorption of visible light and reduction of charge carrier recombination rate. In Co3O4/Sn-ZnO composite, the electrons and hydroxyl active radicals plays the major role in degrading the MB dye into CO2 and H2O. We conclude that Co3O4/Sn-ZnO composite Photocatalyst is a good photocatalytic material recommended for further investigation and practical applications. Moreover, CV and GCD analysis revealed that CuO-SnO2/rGO hybrid composite exhibited enhanced specific capacitance and energy density compared to pristine SnO2. Therefore, it can be recommended as alternative electrode materials for supercapacitor applications.