Effects of N Doping on Phase Transition and Visible-Light Photocatalytic Activity of ZnO/Zinc Titanate Core-Shell Nanorod Arrays

N-doped ZnO/zinc titanate core-shell nanorod arrays (CSNAs) were prepared via simple aqueous solution methods and microwave nitrogen plasma treatment. The impacts of nitrogen doping on the phase structure, band gap and photocatalytic efficiency of the CSNAs were also investigated. After nitrogen plasma treatment, the phase transition of zinc titanate shell layer from cubic Zn2TiO4 to hexagonal ZnTiO3 was demonstrated. X-ray photoelectron spectroscopy indicates that the atomic percentage of the interstitial N is almost unchanged with the increase of the plasma treatment time, while the atomic percentage of the substitutional N increases significantly. It has been found that the optical band gap of N-doped CSNAs is obviously decreased with the increasing of the concentration of the substitutional N. The photocatalytic efficiency of the N-doped CSNAs increases with the concentration of substitutional N under visible-light irradiation. However, when the concentration of substitutional N exceeds 2.34%, the photocatalytic efficiency decreases. The high visible-light photocatalytic efficiency is attributed to the enhancement of visible-light absorption and effective separation of the photogenerated carriers. And the excessive oxygen vacancies introduced by higher concentration of substitutional N lead to the decrease of the photocatalytic activity.

Automated summary

N-doped ZnO/zinc titanate core-shell nanorod arrays were synthesized and their phase structure, band gap, and photocatalytic efficiency were investigated. It was found that moderate substitutional N doping can enhance the visible-light photocatalytic efficiency, while excessive substitutional N concentration leads to a decrease in photocatalytic activity.