甲酰胺对介孔N-TiO2微结构及光催化性能的影响

Effect of Formamide on Microstructre and Photocatalytic Activity of Mesoporous N-TiO_2

以钛酸四丁酯为前躯体,甲酰胺为氮源,采用溶胶凝胶法制备了具有可见光活性氮掺杂二氧化钛(N-TiO2)光催化剂。通过XPS、XRD、低温N2吸附-脱附和UV-Vis等表征,考察甲酰胺加入量对样品微结构和可见光活性的影响。当甲酰胺与钛酸四丁酯的物质的量的比为2、4、8、13时,制备的样品晶粒粒径在8～12nm范围内,孔径在9～16nm范围内,孔隙率在54%～63%之间。甲酰胺与钛酸四丁酯的物质的量的比为13时,所制备样品具有较强的可见光吸收性能,其最大吸收边扩展到570nm左右,禁带宽度减小至2.18eV,比纯二氧化钛禁带宽度3.20eV降低了1.02eV。结果表明:随着甲酰胺加入量的增加,样品的晶粒粒径、孔径、孔隙率明显变大,禁带宽度减小。对甲基橙的室内自然光降解实验证明,氮掺杂二氧化钛具有良好的光催化活性,当甲酰胺与钛酸四丁酯的物质的量的比为13时,催化剂对甲基橙的降解率最高,为98.3%。

A visible-light-driven nitrogen-doped titanium dioxide （N-TiO2） 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 TiO2. 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.