Visible light water splitting using dye-sensitized oxide semiconductors.
Visible light water splitting using dye-sensitized oxide semiconductors.
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DOI：
10.1021/ar9002398
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发表时间：
2009-11
影响因子：
18.3
通讯作者：
W. J. Youngblood;Seung-Hyun Anna Lee;K. Maeda;T. Mallouk
中科院分区：
文献类型：
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作者：
W. J. Youngblood;Seung-Hyun Anna Lee;K. Maeda;T. Mallouk
研究人员正在深入研究光化学水分解作为将太阳能转化为燃料形式的化学能的一种手段。氢是一种重要的太阳能燃料，因为它可以直接用于内燃机或燃料电池，或者与 CO(2) 催化结合以制造含碳燃料。太阳能水分解的不同方法包括作为光催化剂和光电极的半导体颗粒、与析氢和析氧催化剂连接的分子供体-受体系统，以及直接或间接与电催化剂耦合的光伏电池。尽管经过了数十年的研究，太阳能制氢仅在使用昂贵的光伏电池为水电解提供动力的系统中才有效。直接光催化水分解是一个具有挑战性的问题，因为该反应在热力学上是艰难的。光吸收导致分子供体-受体系统和半导体颗粒中高能电荷分离态的形成。不幸的是，能量上有利的电荷复合反应往往比水氧化和还原的缓慢多电子过程快得多。因此，可见光水分解最近才在基于半导体的光催化系统中实现，并且仍然是一个低效的过程。本报告描述了我们解决太阳能水分解中两个问题的方法：将分子组织成促进长寿命电荷分离的组件，以及电解反应的催化，特别是水的四电子氧化。我们的人工光合作用系统的组成部分是宽带隙半导体颗粒、光敏剂和电子中继分子以及纳米颗粒催化剂。我们将层状金属氧化物半导体与金属纳米粒子嵌入。这些插层化合物，当用[Ru(bpy)(3)](2+)衍生物敏化时，催化牺牲电子供体(EDTA(2-))或非牺牲供体(I(-))光产生氢。通过层状金属氧化物半导体的剥离，我们构建了多层电子供体-受体薄膜或敏化胶体，其中单个纳米片介导光驱动的电子转移反应。当敏化剂分子“连接”到IrO(2).nH(2)O纳米粒子时，染料敏化TiO(2)电极成为水分解光电化学电池的光电阳极。尽管该系统是一个有趣的概念验证，但这些电池的性能仍然很差（量子产率约为 1%），并且染料会迅速光降解。我们可以根据水氧化、反电子转移和氧化染料分子分解的竞争动力学途径来理解量子效率和降解。激光闪光光解实验使我们能够测量这些竞争速率，并且原则上可以通过改变电子转移链的结构来提高电池的性能。
Researchers are intensively investigating photochemical water splitting as a means of converting solar to chemical energy in the form of fuels. Hydrogen is a key solar fuel because it can be used directly in combustion engines or fuel cells, or combined catalytically with CO(2) to make carbon containing fuels. Different approaches to solar water splitting include semiconductor particles as photocatalysts and photoelectrodes, molecular donor-acceptor systems linked to catalysts for hydrogen and oxygen evolution, and photovoltaic cells coupled directly or indirectly to electrocatalysts. Despite several decades of research, solar hydrogen generation is efficient only in systems that use expensive photovoltaic cells to power water electrolysis. Direct photocatalytic water splitting is a challenging problem because the reaction is thermodynamically uphill. Light absorption results in the formation of energetic charge-separated states in both molecular donor-acceptor systems and semiconductor particles. Unfortunately, energetically favorable charge recombination reactions tend to be much faster than the slow multielectron processes of water oxidation and reduction. Consequently, visible light water splitting has only recently been achieved in semiconductor-based photocatalytic systems and remains an inefficient process. This Account describes our approach to two problems in solar water splitting: the organization of molecules into assemblies that promote long-lived charge separation, and catalysis of the electrolysis reactions, in particular the four-electron oxidation of water. The building blocks of our artificial photosynthetic systems are wide band gap semiconductor particles, photosensitizer and electron relay molecules, and nanoparticle catalysts. We intercalate layered metal oxide semiconductors with metal nanoparticles. These intercalation compounds, when sensitized with [Ru(bpy)(3)](2+) derivatives, catalyze the photoproduction of hydrogen from sacrificial electron donors (EDTA(2-)) or non-sacrificial donors (I(-)). Through exfoliation of layered metal oxide semiconductors, we construct multilayer electron donor-acceptor thin films or sensitized colloids in which individual nanosheets mediate light-driven electron transfer reactions. When sensitizer molecules are "wired" to IrO(2).nH(2)O nanoparticles, a dye-sensitized TiO(2) electrode becomes the photoanode of a water-splitting photoelectrochemical cell. Although this system is an interesting proof-of-concept, the performance of these cells is still poor (approximately 1% quantum yield) and the dye photodegrades rapidly. We can understand the quantum efficiency and degradation in terms of competing kinetic pathways for water oxidation, back electron transfer, and decomposition of the oxidized dye molecules. Laser flash photolysis experiments allow us to measure these competing rates and, in principle, to improve the performance of the cell by changing the architecture of the electron transfer chain.