A novel approach for enhanced visible light activity in doped nanosize titanium dioxide through the excitons trapping

Abstract

Titanium dioxide doped with iron oxide (0–10 mol%) has been synthesized by an aqueous sol–gel method. The extent of phase transformation is higher in presence of up to 1 mol% of Fe3þ ions in doped titania. A further increase in Fe3þ content was found to decrease the phase transformation. A composition which contains 90% rutile and the remaining anatase phase shows the highest photocatalytic activity. Even though surface area values are dramatically decreased by the modification of TiO2 by Fe3þ doping, crystallinity plays a major role in photocatalytic activity enhancement. UV–vis reflectance spectra indicate a red-shift in band gap energy and thus an enhanced photoactivity in visible light, suitable for application in photodegradation of toxic industrial effluents as well as other organic contaminants, is achieved. Low concentrations of Fe3þ ions act as excitons trapping centers, while higher concentrations act as recombination centers. The synergy between the rutile–anatase ratios and optimum amount of Fe3þ ions improve the interfacial charge transfer and trapping which enhanced the photochemical degradation of MB dye. The Fe3þ doped TiO2 composition has the highest photoactivity, having an apparent rate constant of 11.1 10 3 min 1, which is much higher than that of commercial P25 Degussa titania (6.03 10 3 min 1)