Visible light photocatalysis of Boron & Nitrogen co-doped TiO2 films by Reactive co-Sputtering

• Main Authors: Yan-Yu Lee, 李晏伃
• Other Authors: Ming-Show Wong
• Format: Others
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/47583613549378238474

碩士 === 國立東華大學 === 材料科學與工程學系 === 101 === Titania based phtocatalysts of pure (TiO2), boron-doped (B-TiO2) and boron- and nitrogen-co-doped (B,N-TiO2) thin films were prepared by reactive co-sputtering of Ti and TiB2 targets in O2+Ar or N2+O2+Ar plasma at 100℃. The composition of the films was modulated by the power of TiB2 target and the relative flow rates of oxygen and nitrogen. The as-deposited films were amorphous and became crystalline after subsequently annealed at 600℃ in air or in Ar atmosphere. The effects of annealing on the films were systematically studied in terms of composition, phase, crystallinity, bonding in relation to their photocatalytic properties. Boron in the as-deposited films does not form bonding with titanium; instead it forms boron oxide (B2O3) or boron nitride. The B2O3 has a relatively low melting point at 450oC and at 600oC, the B2O3 component in the films melts and vaporizes to form porous thin films, resulting in higher specific surface area and leading to enhanced photocatalytic properties. When the B,N-TiO2 films were annealed in Ar, some of B2O3 formed and remained on the surface of the porous TiO2 thin film, which increased further the photocatalytic activity. Extending annealing time could improve the crystallinity of the films which also enhanced their photocatalytical performance. In general, the argon-annealed films performed better photocatalytical properties than the air-annealed. With increasing nitrogen content in the B,N-TiO2 films, the amount of Ti3+ or Ti-N bonding increases and significant red-shift is observed in their UV-VIS spectra. The photocatalytical performance of some of the annealed B,N-TiO2 films was greatly enhanced both in the ultraviolet and in the visible light region and their reaction rate constants of degradation of methylene blue increase a factor over ten as compared to the optimal pure TiO2 under UV light and the optimal N-TiO2 under visible light.