Abstract
The photocatalytic activity of CeO2 nanoparticles in the visible spectrum can be greatly improved via incorporating of narrow band gap semiconductors like CdSe and CdTe into CeO2 structure bringing out a new heterojunction structure to boost the visible-light absorption efficiency. Therefore, CeO2/CdSe and CeO2/CdTe nanocomposites were felicitously fabricated through a simple and effective hydrothermal route without using any expensive surfactant or capping agent keeping a molar ratio of 1:1:1 (Ce:Cd:Se/Te). The as-synthesized materials were identified utilizing different spectroscopic investigation techniques such as X-ray diffraction (XRD), Raman spectroscopy and Solid-state UV-diffuse reflectance spectroscopy (UV-DRS). Transmission electron microscopy (TEM) confirmed the semi-spherical structure of all as-synthesized samples with deposition of CdSe and CdTe particles on CeO2 surface leading to binary composites formation. The specific surface areas (BET) were explored to be 55.2 m2/g and 20.8 m2/g for CeO2/CdSe and CeO2/CdTe nanocomposites, respectively. The photocatalytic performance of CeO2/CdSe and CeO2/CdTe nanocomposites was tested under visible-light irradiation on an aqueous solution of Congo red (CR) dye using an energy-saving lamp (LED). The degree of degradation was monitored by UV-Vis spectroscopy and verified by chemical oxygen demand (COD) studies. The photocatalytic degradation efficiency of CeO2/CdSe nanocomposite (97.3%) was about 3.5 times greater than of bare-CeO2 NPs (28.2%) within only 150 min of irradiation. Photo-induced electrons were found to be the primary active participating species that was verified using the relevant radical scavengers and a clear photocatalytic mechanism was proposed. The recycling test confirmed that CeO2/CdSe is a highly photostable catalyst with four-repeating cycles displaying degradation efficiencies, respectively, at 97.3%, 96.1%, 95.5% and 95.1%. The structural stability of the operated catalyst was confirmed by XRD studies.