Low-temperature hydrothermal synthesis of N-doped TiO2 from small-molecule amine systems and their photocatalytic activity.

Nitrogen-doped TiO2 nanopowders have been successfully synthesized by a one-step hydrothennal route under soft-chemistry conditions (150 degrees, 8 h) without high-temperature calcination using seven different types of nitrogen dopants: methylamine, ethylamine, diethylamine, ethylenediamine, triethylamine, triethanolamine and ammonia. X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption isothenns and Fourier transform infrared spectroscopy were used to analyse the as-synthesized TiO2 powders. The results indicated that nitrogen was doped effectively and the structure and morphology of the titania samples were strongly influenced by the nitrogen sources. Among the investigated nitrogen sources, the diethylamine system was clearly superior to the other small-molecule amine or ammonia systems due to the broad-spectrum response (between 400 and 700 nm) of the interstitial nitrogen-doped TiO2 nanopowders. The diethylamine N-doped TiO2 had the largest pore volume (0.39 ml x g(-1)) and showed a well-aligned anatase phase. The visible-light photocatalytic degradation of liquid X-3B used as a probe reaction demonstrated that the removal rate over the diethylamine material reached 99.7% in 90 min.