Characterization of structural and optical properties of the mesoporous Ce-MCM-41 hybrid materials

摘要

Ce-modified mesostructured MCM-41-type hybrid materials with different Si/Ce molar ratios (Si/Ce = 10, 30 and 50) were synthesized by the surfactant-assisted hydrothermal method and their structural and optical properties were characterized by small angle X-ray scattering (SAXS), field emission scanning electron microscopy (FE-SEM) equipped with embedded EDS system, ultraviolet and visible diffuse reflectance (UV–vis DR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Ce-MCM-41 samples show highly ordered 2D porous hexagonal mesostructures and oval and spherical morphologies with particle size between 300 and 600 nm, depending on the incorporated Ce amount. Incorporation of Ce_(4+)into ordered mesoporous silica generates oxygen defects in ceria-silica composites with the formation of Ce_(3+)species as confirmed by the XPS analyses. Cerium incorporation modified their structural regularity and resulted in an effective red shifting of the band gap (2.82 eV at 2.64 eV) due to the creation of intermediate energy states. Both asymmetry and broadening of Raman active F~(2g)mode confirmed the presence of the structural defects. These ordered mesoporous Ce-MCM-41 hybrid materials are potentially attractive for their use as novel photocatalysts in the degradation of organic pollutants present in wastewater employing UV and visible light.