Bi–Y doped and co-doped TiO2 nanoparticles: Characterization and photocatalytic activity under visible light irradiation

• Bi and Y have a synergetic effect on photocatalytic efficiency of co-doped TiO2.
• (Y, Bi) or Bi doping induces a large shift of energy gap, Eg, to the visible.
• Bi and (Bi, Y) doping decreases the recombination rate of photogenerated e–h.
• A decrease of crystallinity seems to occur for high loadings of doping.

TiO2 nanoparticles, doped or co-doped with bismuth and/or yttrium (Bi/Y), were obtained by a sol–gel approach. GXRD and Raman revealed that TiO2 is under the form of anatase and that the introduction of the doping elements decreases its crystallinity. XPS studies confirmed, directly, the presence of dopant-OTi bonds, at least for the Y case. Ground state diffuse reflectance absorption studies revealed that the Bi-doped and co-doped samples exhibit a large shift to the visible. The time resolved laser induced emission revealed that Bi and (Bi, Y) doping induces a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic efficiency under visible irradiation of the unsupported and supported catalysts, in the form of thin film deposited on glass beads, was evaluated using benzoic acid, toluidine and alachlor as pollutant compounds. A meaningful enhancement in the photocatalytic activity was observed upon the co-doping with Y–Bi and is here assigned to the effect of the dopants on the recombination rate of the photogenerated holes and electrons.

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