Highly Tuning of Sunlight-Photocatalytic Properties of SnO₂ Nanocatalysts: Function of Gd/Fe Dopants

Gd/Fe-SnO₂ nanopowders as novel photocatalysts for the active removal of Rose Bengal dye and methyl parathion pesticide were synthesized with a low-cost coprecipitation route. The X-ray diffraction analysis of SnO₂, Sn_0.96Gd_0.02Fe_0.02O₂ and Sn_0.94Gd_0.02Fe_0.04O₂ nanopowders proved the formation of a tetragonal phase of tin oxide with average crystallite sizes in the range of 13–18 nm. The Fourier transform infrared (FTIR) spectra of all samples displayed the characteristic absorption bands of SnO₂. The nanopowder of the pure SnO₂ sample, as seen in its transmission electron microscope (TEM) image, contains spherical-like particles of variable sizes. The TEM images of the Sn_0.96Gd_0.02Fe_0.02O₂ and Sn_0.94Gd_0.02Fe_0.04O₂ powders revealed the synthesis of fine spherical nanoparticles. Based on the TEM images, the average particle size of the pure, (Gd, 2 wt% Fe) and (Gd, 4 wt% Fe) codoped SnO₂ nanopowders was estimated to be 14, 10 and 12 nm, respectively. After the addition of (Gd, 2 wt% Fe) and (Gd, 4 wt% Fe) to the SnO₂ structure, the band gap energy of SnO₂ was reduced from 3.4 eV to 2.88 and 2.82 eV, respectively. Significantly, the Sn_0.96Gd_0.02Fe_0.02O₂ nanocatalyst exhibited a high removal efficiency of 98 and 96% for Rose Bengal dye and methyl parathion pesticide after activation by sunlight for 35 and 48 min, respectively. Furthermore, this catalyst has shown perfect mineralization as well as high stability properties for the treatment of Rose Bengal dye and methyl parathion pesticide. These results suggest the suitability of the Sn_0.96Gd_0.02Fe_0.02O₂ nanocatalyst for the treatment of agriculture and industrial effluent under sunlight light energy.