Preparation Of Nitrogen-doped/Bismuth Modified TiO₂Catalysts By Hydrothermal Method And The Visible Light Photocatalytic Activity

Environmental contamination has been one of the biggest problems which always blockup the sustainable development of the society. So a large number of man power and resourceshave been used to find a method for that. There are always this or that disadvantages with thecommon means of physical, chemical and biological, such as: complex operation, secondarypollution or an expensive cost. Until the last70s, it took us new hopes after the turning up ofsemiconductor technology. Among the so many semiconducting metal oxides, TiO₂has beenpaid much attention for a good deal of advantages, such as strong oxidability, stabilizechemical properties, environmentally friendly and obtained easily. But there are somedisadvantages of TiO₂itself as follows. Firstly, only4%-5%ultraviolet light in the sun couldbe used. Secondly, photogenerated carriers always recombine quickly. So, a big discount hadbeen given when the solar energy was obtained through the origin TiO₂products.Modified TiO₂could extend the visible light absorption and suppress the recombinationof photogenerated carriers. In the so many modified TiO₂photocatalysts, doping with metaland nonmetal ion could extend the visible light absorption and promote the activity so thatdoping is always a good method. The nitrogen doped TiO₂could enhance the absorption inthe visible light area and the photocatalytic activity, so it attracts more attention than othersover long terms. Bismuth lies on the same column with nitrogen, and the bismuthphotocatalysts relating with TiO₂have become a research hot spot, recently.In this paper，nitrogen doped TiO₂（N-TiO₂） and bismuth modified TiO₂were prepared byhydrothermal method with nanotube titanic acid （NTA） as the precursor. The samples werecharacterized by X-Ray diffraction （XRD）, transmission electron microscope （TEM）, X-rayphotoelectron spectroscopy （XPS）, fourier transform infrared （FTIR） and diffused reflectancespectra （UV-Vis DRS）. And then the photocatalytic property was discussed under visible light.The mechanism was discussed after comparing the N-TiO₂/bismuth modified TiO₂. Thespecific contents include： （1） N-TiO₂samples were prepared with urea or ammonium bicarbonate as the nitrogensource. The samples obtained were anatase and rutile mixed phase with a nearly50nm scaleparticles. It was proved that the best doping quantity were both N/Ti （mol）=1/2for urea andammonium bicarbonate. And the pseudo first order reaction constant was586times ofcommercial TiO₂（German, P25） when urea was used as the nitrogen source. The resultsshowed that the using of the precursor NTA was in favour of the absorption of visible light.What’s more, the doped N and mixed phase suppressed the recombination of photogeneratedcarriers effectively.（2） Bismuth modified TiO₂samples were prepared with BiCl3or Bi（NO3）3·5H₂O as thebismuth source. The samples were made up of anatase phase and the corresponding bismuthsalt with a part of10-20nm diamond sheets. And the results showed that the best preparationcondition was the hydrothermal temperature at130℃with Bi/Ti molar ratio1%. Moreover,some BiOCl was prepared when the bismuth source was BiCl3. The BiOCl phase was infavour of visible light absorption, but it would be the combination centre of photogeneratecarriers. But, only a little BiONO3phase and a handful of interval doped nitrogen （N-O-Tiband） were found in the bismuth modified TiO₂with Bi（NO3）₃·5H₂O as the bismuth source.So, it likes that the visible light photocatalytic activity maybe attribute to the compositestructure.