Core–shell structured α-Fe2O3@TiO2 nanocomposites with improved photocatalytic activity in the visible light region

Abstract

The core–shell structured Fe₂O₃@TiO₂ nanocomposites prepared via a heteroepitaxial growth route using the Fe₂O₃ spindle as a hard template display improved photocatalytic degradation activity for Rhodamine B dye under visible light irradiation. The ratio of α-Fe₂O₃ : TiO₂ in the α-Fe₂O₃@TiO₂ core–shell nanocomposites can be tuned by etching the α-Fe₂O₃ core via controlling the concentration of HCl and etching time. An appropriate concentration of the Fe₂O₃ core could effectively induce a transition of the optical response from the UV to the visible region and decrease the recombination rate of photogenerated electrons and the holes of the core–shell structured catalyst, greatly contributing to the enhancement of visible light response and visible light photocatalytic activity of the Fe₂O₃@TiO₂ catalysts. It is revealed that the optical response and photocatalytic performance of the core–shell α-Fe₂O₃@TiO₂ nanocomposites can be tuned by adjusting the molar ratio of Fe₂O₃ : TiO₂ of the α-Fe₂O₃@TiO₂ nanocomposites. The α-Fe₂O₃@TiO₂ core–shell nanocomposite with an optimal molar ratio of 7% for Fe₂O₃ : TiO₂ exhibits the best photocatalytic performance under visible light irradiation. It is shown that the Fe₂O₃/TiO₂ heterojunction structure is responsible for the efficient visible-light photocatalytic activity. As the concentration of Fe₂O₃ is high, Fe³⁺ ions will act as recombination centres of the photogenerated electrons and holes. The present core–shell Fe₂O₃@TiO₂ nanoparticles displaying enhanced photodegradation activity could find potential applications as photocatalysts for the abatement of various organic pollutants.