具有金属中心协同效应的铁配合物作为水氧化催化剂的设计合成与性能研究

Hydrogen is the most ideal environment-friendly renewable energy resource. Extraction of hydrogen from water is considered to be one of the most promising strategies to sustainably tackle the problems of energy shortage as well as the related issues. However, some hurdles in the water oxidation reaction must be overcome while hydrogen is taken from water. To this end, water oxidation catalysts based on transition metal complexes have become the focuses of many research groups. In the present study, the multidentate chelating ligands 2,6–dbtapR and tpXnR will be prepared and employed together with some auxiliary bidentate ligands to form mono-, di- and trinuclear iron complexes. The structures and the properties of the resulting complexes will be investigated. Especially, the catalytic activity of these complexes for water oxidation in homogeneous solutions will be studied by using chemical, photochemical, and electrochemical oxidation methods. Complexes with better activity will be screened out. To further explore the potential application of the catalysts in electrochemical or photoelectrochemical devices, we will introduce those with better activity onto the surfaces of carbon nanomaterials to prepare the composite systems and survey their catalysis in heterogeneous conditions. The catalytic mechanism will be elucidated based on the data of experiments and the theoretical calculations. We try to improve the catalytic effeciency, the overptential, and the durability by using the intramolecular synergetic effect between the iron metal centers in di- and trinuclear complexes, the redox potentials of metal centers adjusted by the auxiliary ligands and the substituent groups of 2,6–dbtapR and tpXnR, and the chelating effect of ligands 2,6–dbtapR and tpXnR, respectively. Iron is one of the earth-abundant non-precious metals. Our research will pave a way for the preparation of environmentally benign, cost-effective, and highly efficient catalysts for water oxidation.

氢气是最理想的零污染的可再生能源。从水中获取氢气是最有前途的可持续发展的解决能源问题的方法之一，但主要困难来自水的氧化半反应。因此，过渡金属配合物催化水氧化成为目前国际研究前沿。我们设计合成多齿配体2,6–dbtapR和tpXnR，以它们为主配体，和辅助配体一起与铁离子反应，制备单、双和三核配合物，表征其结构与性质。用光化学、化学氧化和电化学三种方法考察配合物在均相溶液中对水氧化的催化作用，筛选出稳定高效的催化剂。选择活性较好的吸附到碳纳米材料上并研究其在非均相体系中的活性，探索在电化学或光电化学器件中的应用。结合理论计算推测催化机理。我们尝试通过2,6–dbtapR和tpXnR的螯合效应、配体的取代基与辅助配体对铁离子的氧化电位的调节以及双、三核配合物中的金属中心的协同作用，改善催化效率、过电位和稳定性等。铁元素在地壳中储量丰富，我们为获得高效率低成本的水氧化催化剂进行积极的探索。

水氧化反应是能源转化过程中的重要环节，也是一个瓶颈问题。在本项目的研究工作中，设计合成了新型多齿配体2,6-dbtapR，2,6-dbR和tpXnR，用它们作为主配体，在辅助配体（1，10-邻菲罗啉， 2，2’-联吡啶及其衍生物等）的参与下，与铁、钴、镍、铜等第一过渡系金属离子反应，制备了多个系列新型金属配合物，分析鉴定了配合物的组成与结构，并表征了它们的性质。用化学氧化和电化学等方法研究了配合物在均相溶液中对水氧化的催化作用，筛选出了一些稳定的高效催化剂，例如Fe2O-2,6-dbe-bpy, Cu-tpbn-bpy和Co-tpbn等。把部分活性较好的催化剂吸附到碳纳米材料上并研究了它们在非均相体系中的活性，探索在电化学或光电化学器件中的应用。利用理论计算推测催化机理。实验结果表明，可以利用2,6–dbtapR, 2,6-dbR和tpXnR的螯合作用、主配体上取代基和辅助配体对中心金属离子的氧化电位的调节作用，以及双、多核配合物中的金属中心的协同作用，改善催化剂的效率、过电位和稳定性。本工作的研究结果为研发低成本高效率的以铁、钴、镍、铜等金属为基础的水氧化催化剂提供了很好的借鉴意义。