低量La^(3+)掺杂S-TiO_2光催化剂的制备、表征及其光催化活性

Preparation、Characterization and Photocatalytic Activities of Low Amount La^(3+)-doped S-TiO_2 Photocatalysts

采用溶胶-凝胶-浸渍法制备了La3+/S-TiO2纳米光催化剂,通过XRD、BET、XPS、UV-Vis等手段进行了表征.以甲基橙溶液为光催化降解反应的模型化合物,考察了光催化剂的活性,探讨了低量La3+掺杂对TiO2纳米粒子光催化活性的影响机制.实验结果表明:S改性TiO2后明显提高了TiO2纳米粒子的光催化活性,而La3+掺杂S-TiO2后,进一步提高了TiO2纳米粒子的光催化活性,La3+的最佳掺杂量(相对于TiO2的质量分数)为0.369%;La3+/S-TiO2(ω(La3+)=0.369%)为纳米光催化剂时,甲基橙的脱色率达到92.4%(光照120min);XRD和BET分析表明,低量La3+掺杂抑制了TiO2由锐钛矿向金红石的转变,阻碍了TiO2晶粒的生长,提高了TiO2的比表面积;XPS分析表明,S、La3+掺杂可以导致粉体的表面羟基含量增加,掺杂S以S6+形式置换TiO2晶格中的Ti4+;UV-Vis分析表明,光催化剂La3+/S-TiO2比纯TiO2具有较强的紫外光吸收性能.与纯TiO2相比,La3+掺杂TiO2纳米粒子光催化氧化活性的提高应归因于La3+掺杂增加了表面羟基含量,增大了比表面积,增强了样品表面的紫外光吸收能力.

La3＋/S-TiO2 were prepared by sol-gel-impregnation method and characterized by means of XRD,BET,XPS and UV-Vis. Activities of prepared nano-photocatalysts were evaluated by de- colorizing methyl orange solution as model compound to photoeatalytic degradation. The mechanisms of effects of low amount La^3＋ -doping on the photocatalytic activity of TiO2 nano-particles were discussed. The results show that S-doping can significantly enhance the photocatalytic activity of TiO2 nano-particles and La^3＋ -doped S-TiO2 can further enhance the photocatalytic activity of TiO2 nano-particles. Under optimal addition amount of La^3＋ into TiO2 0.369% （mass fraction）, decolorizing rate of methyl orange on La^3＋/S-TiOz nano-photocatalyst was 92.4 % after 120 min irradiation. The analytical results of XRD show that the presence of low amount of La^3＋ in TiO2 can inhibit the phase transformation from anatase to futile, suppress the growth of TiO2 grains and raise the specific surface area. The analytical results of XPS indicate that S, La^3＋ doping can result in the increase in the density of the surface hydroxyl, and cationic S^6＋ is incorporated into TiO2 lattice and substitutes a part of Ti^4＋. The analytical results of UV-Vis indicate that the La^3＋/S-TiO2 catalyst has stronger absorption in the ultraviolet region than the pure TiO2. Compared with pure TiO2, the enhanced photocatalytic activity of the La^3＋ doped TiO2 nano-powders can be due to the increase of the density of the surface hydroxyl and the specific surface area, and the improvement of the ultraviolet light absorption properties of the particle surface.