Synthesis of TiN/N-doped TiO₂ composite films as visible light active photocatalyst

Titanium nitride/nitrogen-doped titanium oxide (TiN/N-doped TiO$2$⁠) composite films were synthesized for visible light photodegradation applications. Thin films of TiN were sputter-deposited on precleaned glass substrates in an admixture of argon and nitrogen gases. The grown TiN films were subsequently oxidized in air at 350 $°$C at 15, 30, and 60 min. Raman spectral analysis revealed the formation of TiO$2$ with anatase structure at 15 min and transitioned to the rutile structure at longer oxidation times. X-ray photoelectron spectral analysis revealed the formation of N-doped TiO$2$ from the oxidized Ti. Visible light-induced photodegradation of methylene blue as test analyte showed 30% removal efficiency after exposure to visible light after 2.5 h. The highest degradation efficiency was observed when the anatase phase of TiO$2$ is the dominant phase in the film. Moreover, N-doping realized the visible light sensitivity of TiO$2$⁠. This makes the composite film ideal for solar light-driven photodegradation of organic contaminants in wastewater.