Photocatalytic properties of C, N-doped TiO2 films prepared via ion-assisted RF magnetron sputtering

Abstract

Titanium dioxide (TiO₂) is considered one of the most valuable photocatalytic materials due to its unique properties and versatility in various applications. C- or N-doped TiO₂ has been shown to exhibit narrowed band gaps, but codoping of C and N into TiO₂ has seldom been studied. In this study, C, N-doped TiO₂ films were prepared using ion-assisted RF magnetron sputtering. The anatase phase of these films was attained under a substrate temperature of 500 °C in the plasma containing a mixture of CO₂ and N₂. The prepared samples were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Vis spectrophotometer, X-ray photoelectron spectroscopy (XPS), and methylene blue degradation experiments. XRD analysis indicated that the crystallinity of the TiO₂ film was weakened when N-doped, while the anatase phase transitioned to rutile after C-doped. XPS analysis revealed the presence of the atomic β-N state in the film, which contributed to the narrowing of its band gap. In the methylene blue degradation experiments, the C, N-doped TiO₂ film prepared with ion-assisted deposition showed the best visible light (460 nm) photocatalytic activity, in accordance with the reduction in its optical band gap. This study demonstrated that the proposed process is effective in reducing the band gap and enhancing the photocatalytic activity of TiO₂ films.