Enhanced photoelectrochemical and photocatalytic behaviors of MFe2O4 (M = Ni, Co, Zn and Sr) modified TiO2 nanorod arrays.

Xin Gao,Xiangxuan Liu,Xuanjun Wang,Zuoming Zhu,Zheng Xie

doi:10.1038/srep30543

Abstract

Modified TiO2 nanomaterials are considered to be promising in energy conversion and ferrites modification may be one of the most efficient modifications. In this research, various ferrites, incorporated with various cations (MFe2O4, M = Ni, Co, Zn, and Sr), are utilized to modify the well aligned TiO2 nanorod arrays (NRAs), which is synthesized by hydrothermal method. It is found that all MFe2O4/TiO2 NRAs show obvious red shift into the visible light region compared with the TiO2 NRAs. In particular, NiFe2O4 modification is demonstrated to be the best way to enhance the photoelectrochemical and photocatalytic activity of TiO2 NRAs. Furthermore, the separation and transfer of charge carriers after MFe2O4 modification are clarified by electrochemical impedance spectroscopy measurements. Finally, the underlying mechanism accounting for the enhanced photocatalytic activity of MFe2O4/TiO2 NRAs is proposed. Through comparison among different transition metals modified TiO2 with the same synthesis process and under the same evaluating condition, this work may provide new insight in designing modified TiO2 nanomaterials as visible light active photocatalysts.

Highlights

Modified TiO2 nanomaterials are considered to be promising in energy conversion and ferrites modification may be one of the most efficient modifications
The following researches proposed similar theory to explain the role of ZnFe2O4 in enhancing photoactivity of TiO218,19, that is, the adoption of ZnFe2O4 makes the ZnFe2O4/TiO2 composite could use visible light, and the good match of band edges between ZnFe2O4 and TiO2 is in favor of charge carriers separating effectively
By changing the incorporated cations in the MFe2O4, we have found that NiFe2O4 modification can greatly enhance the photoelectrochemical and photocatalytic performance of TiO2 nanorod arrays (NRAs), while CoFe2O4 has relative limited effect

Summary

Introduction

Modified TiO2 nanomaterials are considered to be promising in energy conversion and ferrites modification may be one of the most efficient modifications. Transition metal ferrites with molecular formula of MFe2O4 (M =Zn, Co, Ni, etc.) go into the vision of researchers considering its outstanding attributes These materials possess an important characteristic of narrow band gap, which could absorb the visible light efficiently[7] and promote the photocatalytic reactions. Magnetic property of transition metal ferrites[13,14,15] It is scarce on study of the visible responsiveness of MFe2O4 to increase utilization of solar energy as well as to enhance the photoelectrochemical and photocatalytic performance of TiO2. The following researches proposed similar theory to explain the role of ZnFe2O4 in enhancing photoactivity of TiO218,19, that is, the adoption of ZnFe2O4 makes the ZnFe2O4/TiO2 composite could use visible light, and the good match of band edges between ZnFe2O4 and TiO2 is in favor of charge carriers separating effectively. NiFe2O4, CoFe2O4, ZnFe2O4 and SrFe2O4 are four common transition metal ferrites which have been frequently studied with their magnetism, but except for ZnFe2O4, the other three are not common in modifying TiO2 to enhance its photoactivity, we select the four as research objects, making a comparision between the common one (ZnFe2O4/TiO2) and the uncommon ones (CoFe2O4, ZnFe2O4 and SrFe2O4 modified TiO2)

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Results

Conclusion