N-Doped TiO Photocatalyst Coatings Synthesized by a Cold Atmospheric Plasma.

This work presents a simple, fast (20 min treatment), inexpensive, and highly efficient method for synthesizing nitrogen-doped titanium dioxide (N-TiO) as an enhanced visible light photocatalyst. In this study, N-TiO coatings were fabricated by atmospheric pressure dielectric barrier discharge (DBD) at room temperature. The composition and the chemical bonds of the TiO and N-TiO coatings were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The results indicate that the nitrogen element has doped the TiO lattice, which was further confirmed by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The doping mechanism was investigated using OES to study the plasma properties under different conditions. It suggests that the NH radicals play a key role in doping TiO. The concentration of nitrogen in the N-TiO coatings can be controlled by changing the concentration of NH in the plasma or the applied power to adjust the concentration of NH radicals in the plasma. The band gap of N-TiO was reduced after NH/Ar plasma treatment from 3.25 to 3.18 eV. Consequently, the N-TiO coating showed enhanced photocatalytic activity under white-light-emitting-diode (LED) irradiation. The photocatalytic degradation rate for the N-TiO coating was about 1.4 times higher than that of the undoped TiO coating.