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人工催化剂催化水裂解产生氧气

已有 5045 次阅读 2009-4-5 00:51 |个人分类:科研|系统分类:科研笔记

    绿色植物的光合作用能够利用光能,将水裂解成O2和H+,这一步对于光合作用的后序步骤是必须的。光合作用提供了地球几乎所有生命呼吸所需的氧气,以及食物和能源等。因此,通过模拟光合反应中心裂解水的机制,寻找一种能裂解水的催化剂也成为众多催化学家的关注,可以说寻找裂解水的人工催化剂的研究一直都是“炙手可热”的。以下便是两例。
1. In Situ Formation of an Oxygen-Evolving Catalyst in Neutral Water Containing Phosphate and Co
2+

    From Science,321:1072-0175(2008)
    AuthorsMatthew W. Kanan and Daniel G. Nocera*
    AbstractThe utilization of solar energy on a large scale requires its storage. In natural photosynthesis, energy from sunlight is used to rearrange the bonds of water to oxygen and hydrogen
equivalents. The realization of artificial systems that perform “water splitting” requires catalysts
that produce oxygen from water without the need for excessive driving potentials. Here we report such a catalyst that forms upon the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions. A variety of analytical techniques indicates the presence of phosphate in an approximate 1:2 ratio with cobalt in this material. The pH dependence of the catalytic activity also implicates the hydrogen phosphate ion as the proton acceptor in the oxygen-producing reaction. This catalyst not only forms in situ from earth-abundant materials but also operates in neutral water under ambient conditions.


2. Consecutive Thermal H2 and Light-Induced O2 Evolution from Promoted by a Metal Complex
     From Science,324:74-77(2009)
    AuthorsStephan W. Kohl, Lev Weiner, Leonid Schwartsburd, Leonid Konstantinovski,
Linda J. W. Shimon,2 Yehoshoa Ben-David,1 Mark A. Iron,2 David Milstein1*

    AbstractDiscovery of an efficient artificial catalyst for the sunlight-driven splitting of water into
dioxygen and dihydrogen is a major goal of renewable energy research. We describe a solution-phase reaction scheme that leads to the stoichiometric liberation of dihydrogen and dioxygen in consecutive thermal- and light-driven steps mediated by mononuclear, well-defined ruthenium complexes. The initial reaction of water at 25°C with a dearomatized ruthenium (II) [Ru(II)] pincer complex yields a monomeric aromatic Ru(II) hydrido-hydroxo complex that, on further reaction with water at 100°C, releases H2 and forms a cis dihydroxo complex. Irradiation of this complex in the 320-to-420–nanometer range liberates oxygen and regenerates the starting hydrido-hydroxo Ru(II) complex, probably by elimination of hydrogen
peroxide, which rapidly disproportionates. Isotopic labeling experiments with H217O and H218O show unequivocally that the process of oxygen–oxygen bond formation is intramolecular, establishing a previously elusive fundamental step toward dioxygen-generating homogeneous catalysis.



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