Application of green-synthesized cadmium oxide nanofibers and cadmium oxide/graphene nanosheet nanocomposites as alternative and efficient photocatalysts for methylene blue removal from aqueous matrix.

For the first time, cadmium oxide (CdO) nanofibers (NFs) and graphene nanosheet (GNS)-doped CdO nanocomposites (NCs) have been synthesized by a simple green route using green tea (Camellia sinensis) extract, for subsequent application as photocatalysts for methylene blue (MB) removal from an aqueous matrix. In addition, the materials were tested as working electrodes for supercapacitors. The prepared samples were analyzed by FESEM, UV-Vis spectroscopy, FTIR, and X-ray diffraction (XRD). FESEM revealed that the obtained NPs and NCs show fiber-shaped nanostructure. FTIR confirmed the presence of biomolecules on CdO and carbon compounds on CdO/GNS, while XRD exhibited the cubic crystalline structure of obtained NPs and NCs. The Rietveld refinement using XRD data was performed to ascertain the crystallographic characteristics of the produced samples and look into lattice imperfections. UV-Vis spectroscopy evaluated the optical bandgap energies of CdO and CdO/GNS NCs. The CdO/GNS NCs demonstrated a fast cleavage of the dye molecule under UV irradiation, resulting in 97% removal in 120 min. In addition, CdO/GNS NCs showed remarkable chemical stability as an electrode material, with a high specific capacitance of 231 F g-1 at a scan rate of 25 mV s-1. These observed NCs characteristics are higher when compared to pristine CdO NPs. Finally, we found that the investigated NCs showed enhanced multifunctional properties, such as photocatalytic and supercapacitor characteristics, which can be useful in practical applications.