Gd^(3+)掺杂TiO_2纳米粉体的晶粒尺寸、表面特性和光催化活性

Crystallite size, surface properties and photocatalytic activity of Gd^(3+)-doped TiO_2 nano-powder

利用酸催化的溶胶-凝胶法制备了纯的和不同Gd3+掺杂量的TiO2纳米粉体,并用XRD、BET、XPS、SPS等技术对样品进行了表征.研究了Gd3+掺杂量和焙烧温度对样品光催化降解亚甲基蓝的活性、相结构、晶粒尺寸和表面织构特性的影响,并结合表面光电特性和表面组成等探讨了Gd3+掺杂对纳米TiO2的光催化活性的影响机制.结果表明:与纯TiO2相比,适量掺杂Gd3+可以显著提高其光催化活性.当Gd3+掺杂量为0·5%(质量),焙烧温度为500℃时,TiO2复合纳米粉体的光催化活性最佳,其锐钛矿含量为100%,平均晶粒粒径为15·55nm,比表面积为12·81m2·g-1.Gd3+掺杂强烈地抑制TiO2由锐钛矿相向金红石相的转变,减小晶粒尺寸,提高光响应阈值,这三方面均有利于提高光催化活性.XPS分析表明,Gd3+掺杂导致TiO2纳米粉体的表面羟基含量降低.

Pure and Gd^3＋-doped TiOz nano-particle with different amounts of Gd^3＋-doping were prepared by the acid-catalyzed sol-gel method using Ti（OC4H9）4 and Gd（NO3 ）3 as precursors and characterized with XRD, BET, XPS and SPS. The effects of the amount of Gd^3＋-doping and calcination temperature on the photocatalytic activity for photocatalytic degradation of methylene blue （MB） in aqueous solution, phase structure, crystallite size, surface texture properties of the nanopowders were investigated, and the mechanism of the effects of Gd^3＋-doping on the photocatalytic activity of TiOz nano-particles was also discussed in combination with the surface photoelectric properties and surface composition of the nano- particle. The results indicated that Gd^3＋-doping could enhance the photocatalytic activity of TiOz nano- powder as compared with pure TiO2. 0.5% （mass） Gd^3＋-doped TiOz nano-powder calcined at 500℃ for 2 h show the highest photocatalytic activity. The presence of Gd^3＋ in TiO2 could inhibit the phase transformation from anatase to rutile, restrain crystal grain growth, and enhance the threshold value of photoresponse, which resulted in increase in the photoactivity. XPS result showed that Gd^3＋-doping can lead to decrease in the density of surface hydroxyl groups.