新規エネルギー変換型光触媒による水分解のダイナミクス

K_4Nb_6O_2<17>是一种层状光催化剂，可将水分解为氢和氧。二维夹层为化学反应提供了极大的区域。合适的染料分子在层之间的嵌入实现了光催化反应的可见光响应。在这些情况下，层和染料分子之间的电荷转移被认为是整个光催化化学反应中重要的主要过程。利用飞秒瞬态吸收光谱研究了K_4Nb_6O_2和染料插层K_4Nb_6O_2中光激发引起的超快过程<17><17>。阐明了带隙激发产生的载流子的动力学过程，如电子-空穴复合和电子转移。研究了Ru（bpy）_3^&lt;2+&gt;嵌入K_4Nb_6O_2的动力学过程，揭示了Ru（bpy）_3^&lt;2+&gt;在K_4Nb_6O_2中的快速正、背电子转移过程。在K_4Nb_6O_2中，Ru（bpy）_3 ^&lt;2 +&gt;的吸收峰宽，且吸收峰的宽度大于K_4Nb_6O_2的吸收峰。在K_4Nb_6O_2中，Ru（bpy）_3^&lt;2+&gt;<17>嵌入K_4Nb_6O_2的吸收峰宽，且吸收峰的宽度大于K_4Nb_6O_2的吸收峰宽。 关于我们 在K_4Nb_6O_3中观察到了离子，离子的产生可归因于K_4Nb_6O_3中的电子陷阱<17>。对衰减过程进行了二级动力学分析，表明载流子在二维层中迁移，并发生了电子-空穴复合。还观察到存活时间长于纳秒的长寿命物种，这对于高催化反应性将是重要的。当<17>Ru（bpy）3 ^&lt;2+&gt;插入K_4Nb_6O_2薄膜中时，在400 nm激发下观察到Ru（bpy）3 ^&lt;2+&gt;基态吸收带的瞬态漂白，而K_4Nb_6O_2不能被激发<17>。Ru（bpy）_3^&lt;2+&gt;在水中的漂白行为与在水溶液中不同，表现为快速的非指数衰减。根据样品在可见光照射下的光催化活性，推测Ru（bpy）_3^&lt;2+&gt;的电子转移是通过Ru（bpy）_3^&lt;2+&gt;的光激发进行的。因此，所观察到的动力学可以讨论在皮秒和纳秒以上的时间范围内发生的相对快速的电子转移和随后的复合。超快光谱可以成功地揭示实际使用的光催化剂中的一些重要的初级事件。这些结果有望为新型催化剂的设计提供参考。少

K_4Nb_6O_<17> is known to be a layered photocatalyst to split water into oxygen and hydrogen. The two-dimensional interlayer provides an extremely large area for chemical reactions. Intercalation of suitable dye molecules between the layers achieves visible light response for the photocatalytic reaction. In these cases, charge transfer between the layer and dye molecules is considered to be an important primary process in a whole photocatalytic chemical reaction. By using femtosecond transient absorption spectroscopy, we have investigated ultrafast processes induced by photoexcitation in K_4Nb_6O_<17> and dyeintercalated K_4Nb_6O_<17>. Dynamics of charge carriers generated by bandgap excitation, such as electron-hole recombination and electron transfer was elucidated. The dynamics of Ru(bpy)_3^<2+> intercalated in K_4Nb_6O_<17> was investigated to make clear how fast forward and back electron transfer processes take place.A broad transient absorption band covering the whole visible reg … More ion, which could be ascribed to trapped electrons in K_4Nb_6O_<17>, was observed. The decay was essentially analyzed by second order kinetics, which indicates that the carriers can migrate in the two-dimensional layer and then electron-hole recombination occurs. Long lifetime species surviving longer than nanoseconds was also observed, which would be important for high catalytic reactivity. It the case of the K_4Nb_6O_<17> film intercalated with Ru(bpy)_3^<2+>, transient bleaching of the ground state absorption band of Ru(bpy)_3^<2+> was observed by excitation at 400 nm which cannot excite K_4Nb_6O_<17>. The bleaching of Ru(bpy)_3^<2+> showed fast and non-exponential decay different from that in water. From the fact that this sample shows photocatalytic reactivity under visible light irradiation, electron transfer from Ru(bpy)_3^<2+> should take place by photoexcitation of Ru(bpy)_3^<2+>. Therefore, observed dynamics can be discussed in terms of relatively fast electron transfer and following recombination occurring in the time regions of picosecond and longer than nanosecond.Ultrafast spectroscopy could successfully reveal some important primary events in the practically used photocatalysts. These results are expected to contribute for design of new catalysts. Less