Characterization of Titania Loaded V-, Fe-, and Cr-Incorporated MCM-41 by XRD, TPR, UV−vis, Raman, and XPS Techniques

Abstract

Transition metal (Me = V, Fe, and Cr) incorporated into MCM-41 mesoporous molecular sieves (Si/Me = 80) have been synthesized by hydrothermal methods and were loaded with TiO2 utilizing a sol−gel technique. These materials were found (refs 22, 23) to be photoactive for the destruction of organics with visible light. A combination of various physicochemical techniques such as N2 physisorption, O2 chemisorption, diffuse reflectance UV−vis (DR−UV−vis), X-ray diffraction (XRD), Raman, temperature program reduction (TPR), and X-ray photoelectron spectroscopy (XPS) were used to characterize the chemical environment of these transition metals in the prepared photocatalysts. The dispersion of transition metals as determined by O2 chemisorption suggests that they are well dispersed inside the MCM-41 framework, but the dispersion values decreased with the loading of TiO2. This indicates that the loaded titania promotes the transformation of incorporated metal ions into different phases. DR−UV−vis spectra of the Me-...