SYNTHESIS OF MESOPOROUS OF NyTi1–xCexO2–y STRUCTURES AND ITS VISIBLE LIGHT INDUCED PHOTOCATALYTIC PERFORMANCE

Abstract

The present work was addressed to study the visible light induced performance as photocatalysts of mesoporous N y Ti 1–x Ce x O 2–y structures obtained under microwave irradiation. The titanium dioxide ( TiO 2) was doped with cerium and nitrogen in order to improve the quantum efficiency of the TiO 2 and to shift its adsorption spectra to the visible region. The prepared meso-powders were analyzed by means of X-ray diffraction (XRD), scanning Electron microscopy (SEM), infrared (IR) spectroscopy, transmission electronic microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The surface area was evaluated by means of the Brunauer-Emmett-Teller (BET) method and ultraviolet (UV)-visible diffuse reflectance measurements were performed in order to determine the band gap energy. In addition, the photocatalytic activity of the samples was evaluated by monitoring the photodegradation of methylene blue (MB) under UV and visible light energy irradiation. The results show that our methodology is an effective way for incorporating cerium and nitrogen into TiO 2 compound, which in turn, increases its photocatalytic activity. The diffuse reflectance analysis confirms that the absorption edge was shifted towards the visible region of the optical spectrum. The XRD diffraction patterns indicate homogeneous solid solutions in which prevails the anatase phase. It was observed a reduction in crystal size from 13.1 nm to 7.7 nm for N y Ti 0.98 Ce 0.02 O 2–y in comparison to TiO 2. The textural properties of the synthesized compounds were determined, by means of adsorption isotherms indicating the formation of mesoporous structures. IR spectra show characteristic vibration signals attributed to Ti–O–Ti bonds, as well as vibrations assigned to cerium and nitrogen bonds. The XPS analyses evidence the presence of Ce 3+/ Ce 4+ redox couple and Ti–N bonds. The photocatalityc efficiency was evaluated in the degradation of MB monitoring the absorbance change at 664 nm. The degradation of this compound was 91.4% using N y Ti 0.98 Ce 0.02 O 2–y as photocatalyst under UV energy in 90 min. Also 38.7% of MB degradation was achieved in 150 min under visible light radiation.