A low-band gap, nitrogen-modified titania visible-light photocatalyst

Low-Band gap nitrogen-modified titania photocatalysts were prepared by calcining titanium hydroxide and urea at 400 degrees 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 (lambda >= 420 nm) of formic acid, TiO2-N1 is highly active.