Iron–sulfur codoped TiO2 anatase nano-materials: UV and sunlight activity for toluene degradation

Iron and sulfur single- and co-doped TiO2 nanocrystals were prepared and characterized by a multitechnique approach. The presence of sulfur affected drastically the crystal size of anatase as well as other morphological characteristics such as BET surface area, pore volume and pore size. Significant differences were also detected on the isolated OH species concentration as a function of sulfur content. On the contrary, X-ray absorption spectroscopy (XAFS) showed that sulfur did not alter substantially the structural and electronic properties of Fe on TiO2. The photocatalytic activity of the synthesized TiO2 powders was studied in the gas-phase oxidation of toluene. The trials showed that the co-doped S/Fe-TiO2 nanomaterials have enhanced photo-activity compared to the reference single-doped Fe-TiO2 under both sunlight and UV-light irradiation. This is not however the case if compared with the single S-doped materials. Sulfur additionally modifies the selectivity of toluene photo-oxidation toward partial oxidation products. The partial vs. total oxidation yield ratio increased with increasing S content in both co-doped S/Fe-TiO2 or single-doped S-TiO2 series and was attributed to differences in surface properties related to both S-containing and OH entities.

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► S affected significantly the morphological characteristics of TiO2 catalysts.
► S/Fe co-doped TiO2 show enhanced photoactivity compared to Fe single-doped TiO2.
► Selectivity of partial oxidation products was increased with increasing S-content.
► The differences in photoactivity and selectivity are surface properties related.