Flow controlled fabrication of N doped ZnO thin films and estimation of their performance for sunlight photocatalytic decontamination of water

To address the technological aspect of photocatalyst removal after decontamination, radio frequency (RF) magnetron sputtered nitrogen (N) doped zinc oxide (ZnO) nanoparticles films on glass substrates were fabricated by varying the flow rate of nitrogen. The optical characterization of N-doped ZnO films revealed the shifting of the spectral response to the visible region. The shift of (002) reflections of the films as compared to pure ZnO, in X-ray diffraction (XRD) analysis confirmed the insertion of N in the lattice. The cross-section measurements by FESEM revealed the uniform thickness of ~70 nm of each film. Compared to pure ZnO, the as-fabricated N-doped films showed significantly enhanced degradation/mineralization of 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenoxyacetic acid in natural sunlight exposure. The applicability of Langmuir-Hinshelwood kinetic model was also evaluated. The measurement of Zn2+ ions in the solution during the course of exposure revealed significantly lower magnitude of photocorrosion for the fabricated films compared to pure ZnO. The consistent activity of the films in three successive cycles for the removal of 2-CP established their consistent performance without any loss of activity.