On the synthesis, characterization and photocatalytic applications of nanostructured TiO_2

摘要

Nanocrystalline semiconducting materials are attracting much attention due to their potential applications in solar energy conversion, nonlinear optics, and heterogeneous photocatalysis. In the present investigation, we have synthesized nanostructured TiO_2 photocatalysts, which have been used in the photocatalytic degradation of phenol (one of the most common water pollutants). These catalysts have been prepared through sol-gel technique using titanium tetra-isopropoxide as a raw material for synthesis. Characterization techniques such as XRD, SEM and TEM have been employed for structural/microstructural investigations. XRD results show that the as synthesized TiO_2 nanopowder exhibit anatase phase, TiO_2. The average sizes of the TiO_2 nanopowders are approx 5-10 nm. The optical properties of the samples were investigated through UV-visible and fluorescence techniques. It has been observed that absorption edge corresponds to approx 410 nm (band-gap, approx 3 centre dot 02 eV). The emission peak in the fluorescence spectrum at - 418 nm corresponds to the bandgap energy of approx 2 centre dot 97 eV. Concentration of phenol (initial concentration, approx 100 ppm) with illumination time was monitored by measuring the absorbance of pure and illuminated phenol through UV-visible spectrophotometer. Salient feature of this study relates to the fact that the present sol-gel synthesized TiO_2 nanopowders have been found to be better photocatalysts for phenol degradation than the presently employed commercial TiO_2 (P-25, Degussa) photocatalyst. Thus, whereas phenol concentration, with the presently synthesized TiO_2 nanopowders, the concentration of phenol decreases up to approx 32 percent but for commercial TiO_2 nanopowder (P-25, Degussa), it decreased only up to approx 25 percent. The improved surface area is considered as an important factor for the aforesaid decrease in phenol concentration.