Fe掺杂TiO_2催化剂制备及其光催化脱汞机理  

Preparation of Fe-Doped Titania by Sol-Gel Method and Photocatalytic Removal of Gaseous Mercury

作　　者：代学伟[1] 吴江[1] 齐雪梅[2] 吴强[2] 何平[1] 李忺[1] 

机构地区：[1]上海电力学院能源与机械工程学院,上海200090 [2]上海电力学院环境与化学工程学院,上海200090

出　　处：《环境科学研究》2014年第8期827-834,共8页Research of Environmental Sciences

基　　金：国家自然科学基金项目(50806041);上海市科学技术委员会科技创新行动计划项目(11dz1203402)

摘　　要：采用溶胶-凝胶法制备Fe-TiO2(Fe掺杂纳米二氧化钛)催化剂,通过XRD(X射线衍射仪)、SEM(扫描电镜)、EDX(能量色散X射线光谱仪)和UV-Vis谱对其形态、结构、组成和性质进行表征.采用Fe-TiO2催化剂脱除气态Hg0(元素汞),研究了该催化剂在紫外光和可见光下的脱汞效果,并考察了Fe3+的最佳掺杂比.结果表明:在Fe-TiO2光催化剂中,TiO2以锐钛矿相形态存在,当Fe3+掺杂浓度〔以n(Fe)n(Ti)计〕达到0.010时,所制备的Fe-TiO2在紫外光和可见光下的脱汞率均达到最大,分别为54.76%和18.92%.提出了Fe-TiO2光催化脱汞的可能机制:Fe3+掺入TiO2结构中,使TiO2的导带与Fe3+的d轨道发生重叠,导致TiO2能带变窄,从而扩展了可见光的响应范围;Fe3+在TiO2中作为一个浅俘获阱,当其俘获光生电子以后,光生空穴能够继续扩散到TiO2表面发生表面化学反应,生成具有强氧化性的超氧自由基O2-和·OH,对Hg0进行氧化;当Fe3+掺杂浓度大于0.010时,由于过多的Fe3+成为了光生电子和光生空穴的俘获位,从而使俘获的电子-空穴对通过量子隧道效应复合的概率增加,同时,活性氧化物种O2-和·OH相互消耗,抑制了光催化效率.Fe-doped titanium dioxide（ Fe-TiO2） nanoparticle catalysts were prepared by the sol-gel method,and their morphological structures,compositions and properties were characterized by XRD（ X-ray diffraction）,SEM（ scanning electronic microscopy）,EDX（ energy dispersive X-ray spectroscopy） and UV-Vis spectrophotometry. Fe-TiO2 nanoparticles were used to remove gaseous elemental mercury under UV light and visible light respectively,and the optimum doping content of Fe3 ＋was determined. The results showed that Fe-TiO2 nanoparticles are an anatase,and that when the doping mole ratio of Fe/Ti was 0. 010,the Fe-TiO2 catalyst had the highest Hg0 removal ability under both UV light（ removal efficiency 54. 76%） and visible light（ removal efficiency 18. 92%）. The probable mechanism by which Fe-TiO2 nanoparticles remove gaseous elemental mercury was proposed： Fe3 ＋ions doped into the TiO2 structure may overlap the conduction bands of TiO2 and the d orbital of Fe3 ＋,which results in the narrowing of the band gap and the extension of the visible light response. Fe3 ＋in TiO2 was a shallow trap,so after Fe3 ＋captured the photo-generated electrons,the photo-generated holes could continue to spread to the surface of TiO2 and accomplish surface chemical reactions,which produced reactive oxidative radicals O-2and·OH for the oxidation of Hg0. When Fe3 ＋doping molar concentration exceeded 0. 010,the excessive Fe3 ＋became the trapping position of photo-generated electrons and photo-generated holes,increasing the probability of recombination of trapped electron-hole pairs via the quantum tunneling effect. Accompanied with the selfconsumption of excessive reactive oxidative radicals O2-and·OH,the photocatalytic efficiency was accordingly reduced. This is the mechanism by which there existed an optimum Fe/Ti doping molarratio. The results provide some help for exploring ion modified method of TiO2 and its application in the visible light photocatalytic field.

关 键 词：Fe3+掺杂 TiO2 溶胶-凝胶 光催化 汞 可见光响应 

分 类 号：X513[环境科学与工程—环境工程]