Endowing single-electron-trapped oxygen vacancy self-modified titanium dioxide with visible-light photocatalytic activity by grafting Fe(III) nanocluster

Nanotubular titanic acid (denoted as NTA) was calcined in air to generate TiO2 containing a large amount of single-electron-trapped oxygen vacancy (abridged as SETOV and denoted as V-0(center dot)). Resultant V-0(center dot) self-modified (or self-doped) TiO2 (denoted as V-0(center dot)-TiO2), visible light responsive but photocatalytically inactive under visible-light irradiation, was grafted with Fe(III) nanoclusters via an impregnation method to afford Fe(III)-V-0(center dot)-TiO2 possessing visible-light phtocatalytic activity. The photocatalytic performance of as-prepared Fe(III)-Ve-TiO2 photocatalysts was evaluated and compared with that of N-doped TiO2, and the experimental results were further discussed based on density functional theory calculations. Results reveal that grafting Fe(III) leads to nearly no changes in the crystalline structure as well as morphology and grain size of Ve-TiO2 but results in good visible-light photocatalytic performance for the photodegradation of gaseous propylene under visible-light irradiation. This is because the grafted Fe(III) nanoclusters act as efficient electron trapping centers to significantly enhance the electron transfer from oxygen vacancy state and the conduction band of TiO2 to the adsorbed oxygen, thereby inducing the rapid separation of the photogenerated electrons and holes. Besides, the photocatalytic activity of Fe(III)-V-0(center dot)-TiO2 photocatalysts is dependent on the dosage of grafted Fe(III), and it is critical to maintain a good matching between the energy level of V-0(center dot) and surface-grafted Fe(III) cocatalyst so as to facilitate fast and efficient charge transfer. Thanks to the good availability, low cost, and nontoxicity, Fe as the cocatalyst could find promising applications in the development of high-performance photocatalysts. (C) 2015 Elsevier B.V. All rights reserved.