Visible light-driven water oxidation by Ir oxide clusters coupled to single Cr centers in mesoporous silica
Visible light-driven water oxidation by Ir oxide clusters coupled to single Cr centers in mesoporous silica
复制标题
DOI：
10.1021/ja0625632
复制
发表时间：
2006-08-23
影响因子：
15
通讯作者：
Frei, Heinz
中科院分区：
文献类型：
--
作者：
Nakamura, Ryuhei;Frei, Heinz
可见光诱导的水氧化已在与 MCM-41 介孔二氧化硅孔表面上的单个 CrVIsite 偶联的氧化铱纳米团簇中得到证实。该光催化单元是通过表面 CrO 基团与 Ir(acac)3 前体反应组装而成，然后在 300 °C 下煅烧，并通过 FT-拉曼和 FT-IR 光谱监测键的形成。煅烧材料的高分辨率 Z 对比电子显微照片与能量色散 X 射线点分析相结合，证实了氧化铱纳米粒子在中孔内的闭塞。通过质谱法监测 CrVI-O 配体到金属电荷转移吸收的可见光照射下 IrxOy−CrMCM-41 水悬浮液的析氧情况。低 Cr 含量 (Cr/Si ≤ 0.02) 和高 Cr 含量 (Cr/Si = 0.05) 样品的产物产率比较表明，只有孤立的 Cr 中心能够从 Ir 氧化物簇中提取电子，而二铬或多铬酸盐物质则不能。以前从未证明过与单个金属中心偶联的多电子转移催化剂上的水氧化。使用单个金属中心作为电子泵驱动水氧化的能力为将放氧光催化单元与纳米多孔支架中的还原位点偶联提供了机会。
Visible light-induced water oxidation has been demonstrated at an Ir oxide nanocluster coupled to a single CrVIsite on the pore surface of MCM-41 mesoporous silica. The photocatalytic unit was assembled by the reaction of surface CrO groups with Ir(acac)3precursor followed by calcination at 300 °C and bond formation monitored by FT-Raman and FT-IR spectroscopy. High-resolution Z-contrast electron micrographs of the calcined material combined with energy-dispersive X-ray spot analysis confirmed the occlusion of Ir oxide nanoparticles inside the mesopores. Oxygen evolution of an aqueous suspension of the IrxOy−CrMCM-41 upon visible light irradiation of the CrVI−O ligand-to-metal charge-transfer absorption was monitored mass-spectrometrically. Comparison of the product yields for samples with low Cr content (Cr/Si ≤ 0.02) and high Cr content (Cr/Si = 0.05) indicates that only isolated Cr centers are capable of extracting electrons from Ir oxide clusters, while di- or polychromate species are not. Water oxidation at a multielectron-transfer catalyst coupled to a single metal center has not been demonstrated before. The ability to drive water oxidation with a single metal center as electron pump offers opportunities for coupling the oxygen-evolving photocatalytic unit to reducing sites in the nanoporous scaffold.