Departament de Química, Universitat Autònoma de Barcelona , Cerdanyola del Vallès, 08193 Barcelona, Spain.
Acc Chem Res. 2014 Feb 18;47(2):504-16. doi: 10.1021/ar400169p. Epub 2013 Dec 11.
One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for these catalysts.
一种替代化石燃料的清洁方法是利用阳光分解水。然而，要实现这一目标，研究人员仍需要充分理解和控制几个关键的化学反应。其中之一是水的催化氧化反应生成氧气，这也发生在绿色植物和藻类的光系统 II 的氧释放中心。尽管它对生物学和可再生能源很重要，但该反应的机制尚未完全了解。均相中的过渡金属水氧化催化剂为研究人员提供了一个极好的平台，可以研究和提取关键信息，以准确描述这一复杂反应所涉及的不同步骤。在分子水平上提取的机理信息使研究人员能够理解控制该反应的因素以及导致系统分解的因素。因此，可以开发出具有潜在技术应用的坚固高效的水氧化催化剂。在本述评中，我们根据我们实验室的工作，并结合其他小组的研究，讨论了均相相过渡金属催化的水氧化反应的当前机理理解。我们没有综述迄今为止描述的所有催化剂，而是系统地关注在均相介质中研究的几个关键要素及其基本原理。我们根据关键的氧-氧键形成步骤的方式，即通过水分子的亲核攻击还是通过两个 M-O 单元的相互作用，来组织这些催化剂，而不是根据水氧化催化剂的核性。此外，我们还使用 DFT 方法来描述关键的中间体和过渡态。理论和实验的结合使我们能够全面了解不同催化剂的水氧化循环。最后，我们还描述了这些催化剂的各种失活途径。
