Synthesis of Visible Light Active Photocatalyst Controlling the Nanostructure of Layered Titanate

制备了层状钛酸盐、CdS、Fe_2O_3和TiO_2掺杂的H_2Ti_4O_9、Cu^<2+>和Nb^<5+>或Ta^<5+>同时掺杂的H_2Ti_4O_9以及TiO_2和Pt掺杂的层状HTaWO_6，并研究了它们在可见光照射下的光催化活性。在可见光照射下（λ 0 x（3E）400 nm），所有样品对硫化钠和甲醇水溶液的析氢反应都具有光催化活性。紫外光照射下HTaWO_6在甲醇水溶液中不稳定，而HTaWO_6/（TiO_2，Pt）纳米复合材料在甲醇水溶液中稳定，并表现出可见光活性。半导体粒子的光催化活性是由于电子转移引起的电荷分离。通过对CdS和TiO_2在H_2Ti_4O_9和H_4Nb_6O_6中的荧光寿命的分析<17>，证实了中间层中CdS和/或TiO_2中的光生电子迅速转移到基质层。测得CdS与H_2Ti_4O_9和/或H_4Nb_6O_3之间的电子转移速率常数<17>为ca.从<-1>TiO_2到H_2Ti_4O_9和H_4Nb_6O_3的转化率分别<17>为10^8秒/小时<-1>。

Layered titanate, H_2Ti_4O_9 incorporating CdS, Fe_2O_3 and TiO_2, H_2Ti_4O_9 simultaneously alloyed with Cu^<2+> and Nb^<5+> or Ta^<5+>, and layered HTaWO_6 incorporating TiO_2 and Pt were prepared and their photocatarytic activities under visible light irradiation were investigated. All samples possessed photocatalytic activity for the hydrogen evolution from sodium sulfide or methano aqeous solution under visible light irradiation (λ 0x(3E) 400 nm). HTaWO_6 was unstable in methanol aqueous solution under UV light irradiation, but HTaWO_6/(TiO_2,Pt) nanocomposite was stable and showed visible light active photocatalytic activity for evolving hydrogen gas from methanol aqueous solutionn. The excellent photocatalitic activity of semiconductor particles incorporated was attributed to the charge separation by guest to host electron transfer. By analyzing the fluorescence life times of CdS and TiO_2 incorporated in H_2Ti_4O_9 and H_4Nb_6O_<17>, it was confirmed that photoinduced electron in CdS and/or TiO_2 in the interlayer quickly transfer to the host layers. The electron transfer rate constant from CdS to H_2Ti_4O_9 and/or H_4Nb_6O_<17> were determined as ca. 10^6 sec^<-1> and those from TiO_2 to H_2Ti_4O_9 and H_4Nb_6O_<17> were 10^8 sec^<-1>.