Micro and nanodomains on structured silica/titania photocatalysts surface evaluated in RhB degradation: Effect of structural properties on catalytic efficiency

Abstract

Mesoporous nanoparticles and mixed-structure silica with existing nanometric and micrometric domains on their surface were prepared using SiCl4. TiCl4 was used as precursor to obtain nano- and mixed heterogeneous supported titania photocatalysts. The systems and, for comparative reasons, commercial (P25) were evaluated for Rhodamine B (RhB) photodegradation in deionized and lake water solution. The structural differences between nano- and mixed photocatalysts were observed and are due to the degree of particles structural organization, according to small-angle X-ray scattering (SAXS) profiles. The structural analysis obtained by fractal dimension (pL) showed that photocatalysts which were organized as mass fractal structures presented higher catalytic activity than the photocatalysts of rough surface fractal or non-fractal. A compressive discussion on surface topology, size, band gap, surface area, surface charge density, and catalysts amount was done to explain the effect of these features on the photocatalysts performance. The distribution of Ti-O-Si species on the support surface was determined by X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). The higher photocatalytic activity for the degradation of RhB dye was achieved by SNCl5Ti sample. This catalyst achieved high efficiency factor, EF = mg of RhB degraded/ mg of catalyst, equal to 0.020 and 0.0132, under UV and Vis radiation, respectively, which is lower catalyst amount than the similar TiO2-SiO2 based systems reported in the literature. These findings broaden the opportunities to degrade other harmful pollutants in wastewater. This work also provides an insight on how structural properties are correlated to the efficiency of titania supported nano/micrometric catalysts.

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