Remarkable Enhancement of Photocatalytic Hydrogen Evolution Efficiency Utilizing An Internal Cavity of Supramolecular Porphyrin Hexagonal Nanocylinders Under Visible-Light Irradiation
Remarkable Enhancement of Photocatalytic Hydrogen Evolution Efficiency Utilizing An Internal Cavity of Supramolecular Porphyrin Hexagonal Nanocylinders Under Visible-Light Irradiation
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DOI：
10.1021/jp400381h
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发表时间：
2013-03-07
影响因子：
3.7
通讯作者：
Fukuzumi, Shunichi
中科院分区：
文献类型：
--
作者：
Hasobe, Taku;Sakai, Hayato;Fukuzumi, Shunichi
利用超分子卟啉六方纳米柱将Pt胶体沉积的TiO 2纳米颗粒（Pt/TiO 2）封装在其内腔中，开发了一种高效的可见光诱导析氢体系.首先，卟啉纳米柱的结构控制封装Pt/TiO 2通过溶剂混合物技术制备。在表面活性剂十六烷基三甲基溴化铵（CTAB）的作用下，在DMF/H2O混合溶液中形成了由Pt/TiO 2和meso-四（4-吡啶基）卟啉锌[ZriP（Py）（4）]组成的棒状结构[记为Pt/TiO 2-ZnP（Py）（4）纳米棒]。在扫描电子显微镜（SEM）测量中，观察到具有大中空结构的ZnP（Py）（4）原始六方纳米圆柱体[表示为ZnP（Py）（4）纳米圆柱体]，而在Pt/TiO 2-ZnP（Py）（4）纳米棒的情况下中空孔完全闭合。X射线衍射（XRD）分析还表明，ZnP（Py）（4）在纳米棒中的排列是基于ZnP（Py）（4）配位六方结构的堆叠组装。这些结果清楚地表明，Pt胶体沉积的TiO 2纳米颗粒（Pt/TiO 2）被成功地封装在ZnP（Py）（4）六方纳米圆柱体。Pt/TiO 2-ZnP（Py）（4）由于ZnP（Py）（4）的聚集，在可见光区也表现出较宽的吸收。然后，Pt/TiO 2-ZnP（Py）（4）在可见光照射下表现出有效的析氢，而在没有ZnP（Py）（4）的Pt/TiO 2的情况下没有析氢。此外，单位质量Pt的Pt/TiO 2-ZnP（Py）（4）纳米棒的析氢效率比未包封的Pt/TiO 2和ZnP（Py）（4）纳米柱复合物[Pt/TiO 2 + ZnP（Py）（4）复合物]的析氢效率高两个数量级。最后，利用飞秒时间分辨瞬态吸收光谱研究了Pt/TiO 2 ZnP（Py）（4）纳米棒的激发态光动力学，以阐明其光催化机理。
An efficient visible light-induced hydrogen evolution system has been developed by using supramolecular porphyrin hexagonal nanocylinders that encapsulate Pt-colloids-deposited TiO2 nanoparticles (Pt/TiO2) in the internal cavity. First, porphyrin nanocylinders structurally controlled by encapsulated Pt/TiO2 are prepared via a solvent mixture technique. The bar-shaped structure composed of Pt/TiO2 and zinc meso-tetra(4-pyridyl)porphyrin [ZriP(Py)(4)] is formed with the aid of a surfactant: cetyltrimethylammonium bromide (CTAB) in a DMF/H2O mixture solution [denoted as Pt/TiO2-ZnP(Py)(4) nanorocls]. In scanning electron microscopy (SEM) measurements, ZnP(Py)(4) pristine hexagonal nanocylincler with a large hollow structure [denoted as ZnP(Py)(4) nanocylinder] was observed, whereas the hollow hole was completely closed in case of Pt/TiO2-ZnP(Py)(4) nanorods. X-ray diffraction (XRD) analyses also revealed that ZnP(Py)(4) alignment in the nanorod was based on the stacked-assemblies of ZnP(Py)(4) coordinated hexagonal formations. These results clearly indicate that Pt colloids-deposited TiO2 nanoparticles (Pt/TiO2) were successfully encapsulated within a ZnP(Py)(4) hexagonal nanocylinder. Pt/TiO2-ZnP(Py)(4) also shows a broadened absorption in the visible region because of aggregation of ZnP(Py)(4). Then, Pt/TiO2-ZnP(Py)(4) exhibited efficient hydrogen evolution under visible light irradiation, whereas no hydrogen was evolved in the case of Pt/TiO2 without ZnP(Py)(4). In addition, the hydrogen evolution efficiency of Pt/TiO2-ZnP(Py)(4) nanorods per unit weight of Pt was two orders magnitude greater than that of the nonencapsulated system: Pt/TiO2 and ZnP(Py)(4) nanocylinder composites [Pt/TiO2 + ZnP(Py)(4) composites]. Finally, the photodynamics of the excited state of Pt/TiO2 ZnP(Py)(4) nanorods was examined by ferntosecond time-resolved transient absorption spectroscopy to clarify the photocatalytic mechanism.