Ag/N-TiO2/SBA-15光催化剂的制备及其可见光催化还原CO2
收稿日期: 2014-07-17
修回日期: 2014-09-24
网络出版日期: 2014-09-24
基金资助
项目受国家自然科学基金(No. 21003150)、山西省自然科学基金(No. 2011011006-2)和煤转化国家重点实验室自主研究项目(No. 2011BWZ011)资助.
Synthesis of Ag/N-TiO2/SBA-15 Photocatalysts and Photocatalytic Reduction of CO2 under Visible Light Irradiation
Received date: 2014-07-17
Revised date: 2014-09-24
Online published: 2014-09-24
Supported by
Project supported by the National Natural Science Foundation of China (No. 21003150), the Natural Science Foundation of Shanxi Province (No. 2011011006-2) and Independent Research Foundation of the State Key Laboratory of Coal Conversion (No. 2011BWZ011).
以钛酸四正丁酯(TB)，羧基改性的SBA-15 (COOH/SBA-15)，尿素和AgNO3为原料，利用溶剂热及焙烧处理制得Ag/N-TiO2/SBA-15催化剂. 采用X 射线衍射(XRD)，低温N2吸脱附，X 射线光电子能谱(XPS)，紫外-可见漫反射光谱(UV-vis DRS)，荧光(PL)光谱，电感耦合等离子体原子发射光谱(ICP)和元素分析(EA)等表征. 结果显示：Ag/N-TiO2/SBA-15样品具有介孔结构，TiO2以单一的锐钛矿晶型均匀的分散在载体表面，Ag以单质形态沉积在TiO2表面，N则掺入到TiO2晶格中，并以取代N(O-Ti-N)和间隙N(Ti-O-N)两种方式共存. Ag/N-TiO2/SBA-15催化剂中单质Ag既可以捕获光生电子提高量子效率，又促进了TiO2对可见光的吸收. N掺杂拓宽了TiO2吸收光谱的吸收范围，并且适量的N掺杂有助于光生电荷的分离，提高了光催化效率. 以光催化还原CO2为探针反应，考察了催化剂在可见光下的催化活性. 结果表明：Ag/N-TiO2/SBA-15系列催化剂均表现出了可见光催化还原CO2性能，发现当Ag的质量分数为2%，N与Ti的物质的量比为3时，催化剂光催化活性最佳，产物甲醇产量高达45.7 μmol·g-1·h-1.
高梦语 , 姜东 , 孙德魁 , 侯博 , 李德宝 . Ag/N-TiO2/SBA-15光催化剂的制备及其可见光催化还原CO2[J]. 化学学报, 2014 , 72(10) : 1092 -1098 . DOI: 10.6023/A14070535
Silver-loaded together with nitrogen-doped highly dispersed TiO2/SBA-15 mesoporous catalysts were successfully synthesized through solvothermal treatment and calcination method by using titanium n-butoxide (TB), carboxylate-modified SBA-15 (COOH/SBA-15), urea and silver nitrate as raw materials. The detailed preparation procedure was as follows: 1.0 g COOH/SBA-15 powder was dispersed in solution containing 0.82 mL titanium n-butoxide (TB) and 20.0 mL acetic ether. The mixture was stirred for 30 min at room temperature, then 0.031 g AgNO3 was added into the solution by further stirring for 30 min and a certain amount of urea was added. After being stirred continuously for 3 h, the resultant solution was transferred into a teflon-lined stainless autoclave and solvothermally treated at 220 ℃ for 12 h. After naturally cooling to room temperature, the resultant product was washed three times with absolute ethanol and then dried under vacuum at 80 ℃ for 12 h. Finally the solids were calcined in air at 550 ℃ for 4 h at a heating rate of 1.5 ℃/min. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), UV-Visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectra (PL), inductively coupled plasma atomic emission spectrum (ICP) and elemental analysis (EA). It was revealed that the highly dispersed samples consist of anatase crystalline phase were mesoporous structure. The anatase phase was retained without phase change after silver loading and nitrogen doping. Silver was deposited on the surface of catalysts in the form of metallic silver and served as an effective electron trapper which could prevent the fast recombination of the photo-generated electrons and holes, at the same time, visible light absorption of samples were enhanced by silver nanoparticle based on its surface plasmon resonance effect. Nitrogen was doped into TiO2 matrix in the form of both interstitial nitrogen and substitutional nitrogen, nitrogen dopants might be presented in the chemical environment of Ti-O-N and O-Ti-N. On one hand, nitrogen doping could extend the adsorption of catalysts to the visible light region (λ>400 nm); on the other hand, appropriate amount of nitrogen doping could inhibit the recombination of the photo-generated charge carriers and increase the efficiency of the photocurrent carriers. The high photocatalytic performance could be attributed to the synergistic effect of nitrogen doping and the loaded silver nanoparticles over TiO2. The nitrogen doping concentration had an optimal value. When the loading amount of Ag was 2 wt% and the theoretical mole ratio of nitrogen to Ti was 3, the photocatalyst had the highest photocatalytic activity. The methanol yield was 45.7 μmol·g-1·h-1.
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