A Low-Band Gap, Nitrogen-Modified Titania Visible-Light Photocatalyst

Abstract

Low-Band gap nitrogen-modified titania photocatalysts were prepared by calcining titanium hydroxide and urea at 400 °C. Different from previously known nitrogen-doped titania (TiO2−N), which exhibits a strong band-to-band absorption in the ultraviolet and only a weak shoulder in the visible, the new materials (TiO2−N1 and TiO2−N2) have an intense band-to-band absorption in the range of 400−500 nm, resulting in corresponding band gaps of 2.46 and 2.20 eV. As compared to unmodified titania, the quasi-Fermi level of electrons is anodically shifted by 0.07−0.16 eV. Whereas TiO2−N is inactive in visible-light mineralization (λ ≥ 420 nm) of formic acid, TiO2−N1 is highly active.