High photocatalytic activity of Fe₂O₃/TiO₂nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid

Abstract

Two series of Fe2O3/TiO2 samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe2O3/TiO2 for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe2O3/TiO2 nanocomposites prepared by impregnation showed lower activity than the unmodified TiO2, mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe2O3/TiO2 nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO2. Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe2O3(0.5)/TiO2. The improved activity of TiO2 after photodeposition of Fe2O3 was contributed to the formation of a heterojunction between the Fe2O3 and TiO2 nanoparticles that improved charge transfer and suppressed electron–hole recombination. A further investigation on the role of the active species on Fe2O3/TiO2 confirmed that the crucial active species were both holes and superoxide radicals. The Fe2O3(0.5)/TiO2 sample also showed good stability and reusability, suggesting its potential for water purification applications.

Cobalt Oxide-Modified Titanium Dioxide Nanoparticle Photocatalyst for Degradation of 2,4-Dichlorophenoxyacetic Acid

“…4(a), it was confirmed that the P25 TiO 2 showed strong emission spectrum with emission peaks at 410, 465, and 544 nm. It has been reported that the peak around 410 nm would correspond to the radiative recombination of self-trapped exciton and the other two emission peaks at 465 and 544 nm would be due to the charge transfer of an oxygen vacancy trapped electron [11]. Addition of CoO did not give the formation of any new emission peaks, but decreased the emission intensity of the bare P25 TiO 2 ( Fig.…”

“…The excited electrons would react with adsorbed oxygen to produce superoxide radicals, while holes would oxidize 2,4-D. Holes could also oxidize water to produce hydroxyl radicals. However, the contribution of hydroxyl radicals to degrade 2,4-D would not be as high as those of superoxide radicals and holes due to the low formation of hydroxyl radicals [11]. In addition to this pathway, electrons could be also trapped by cobalt species, which in turn caused a better separation of electrons and holes, and thus, higher photocatalytic activity.…”

“…Another approach to improve the activity of TiO 2 photocatalyst for degradation of 2,4-D is by introducing transition metal and rare earth oxides, such as copper [5][6][7][8], lanthanum [9][10], and iron oxides [11]. In particular, it has been shown that cobalt species has the potential of enhancing the photocatalytic activity of TiO 2 for various reactions [19][20][21].…”

“…As for photocatalytic degradation of 2,4-D, the most widely used photocatalysts were also TiO 2 and its modifications [2][3][4][5][6][7][8][9][10][11]. As a photocatalyst, TiO 2 has a range of useful features, including high photocatalytic activity, stability, low toxicity, ready availability and low cost.…”

“…Therefore, the efficient treatment to remove 2,4-D in water still needs to be investigated. There are various methods that have been reported to degrade 2,4-D. One of the most promising methods is by photocatalytic reaction [2][3][4][5][6][7][8][9][10][11][12][13][14].…”