TiO2 nanopowders doped with boron and nitrogen for photocatalytic applications

TiO2-based systems have attracted an increasing interest for their potential use as photocatalysts under visible-light irradiation. In thiscontext, the present work was dedicated to the tailored synthesis of TiO2 nanopowders doped with boron, nitrogen or both species forthe photocatalytic degradation of organic dyes. In particular, the systems were synthesized by a sol-gel route starting from titanium(IV)butoxide as a Ti source and thoroughly characterized by the combined use of N2 physisorption, X-ray diffraction (XRD), Raman spectroscopy,X-ray photoelectron spectroscopy (XPS), UV-Vis reflectance spectroscopy and temperature-programmed oxidation (TPO).Finally, the photocatalytic performances in the decomposition of the azo-dye methyl orange (MO) were investigated.The obtained results suggest that both dopants promote the photocatalytic activity with respect to pure TiO2 systems. Nevertheless,while our surface N-doping does not appreciably modify the titania structure and texture, B incorporation inhibits the TiO2 crystallitegrowth and induces an increase in the surface area. As regards the codoped systems, a remarkable reactivity improvement was observedonly when B is present in excess with respect to N. A rational interpretation of the observed behaviour was attempted by calculationsbased on the density functional theory (DFT). We suggest that the presence of B in molar excess with respect to N generates reactiveTi(III) sites, which, in turn, might induce the formation of reactive superoxide species.