Effect of formamide on microstructre and photocatalytic activity of mesoporous N-TiO ₂

A visible-light-driven nitrogen-doped titanium dioxide (N-TiO ₂) photocatalyst was synthesized by sol-gel method, using titanium tetrabutoxide as Ti-precursor and formamide as nitrogen source. The effect of formamide on the microstructrue and the visible light absorption activity was also studied by means of XPS, XRD, low temperature nitrogen adsorption-desorption, UV-Vis techniques. The results show that when the molar ratio of formamide to titanium terabutoxide is 2, 4, 8 or 13, nitrogen-doped titanium dioxide will be obtained and the grain size, mesoporous pore size and porosity will be in the range of 8-12 nm, 9-16 nm and 54% -63%, respectively. Especially, when the molar ratio is 13, the materials show excellent visible light absorption, the absorption band is shifted, to about 570 nm and the band gap is reduced to 2.18 eV, which is 1.02 eV less than that of pure TiO ₂. Furthermore, the grain size, pore size, porosity of the material increase and the band gap decreases with the increase in the concentration of formamide. The photocatalytic activity evaluation using methyl orange as model pollutant shows that nitrogen-doped titanium dioxide is a better photocatalytic catalyst, and over 98.3% of methyl orange could be degraded under indoor natural light after 7 h reaction when the photocatalyst is prepared with molar ratio of 13 for formamide to titanium terabutoxide.