Artificial Photosynthesis: Molecular Catalysts for Water Oxidation

Abstract: Artificial photosynthesis provides a promising solution to the future sustainable energy system. Water is the only suitably sufficient protons and electrons supplier by the reaction of water oxidation. However, this reaction is both kinetically and thermodynamically demanding, leading to a sluggish kinetics unless the introduction of a catalyst.The theme of this thesis is to design, synthesize and evaluate molecular catalysts for water oxidation. This thesis consists of seven parts:The first chapter presents a general introduction to the field of homogenous catalysis of water oxidation, including catalysts design, examination and mechanistic investigation.The second chapter investigates the electronic and noncovalent-interaction effects of the ligands on the activities of the catalysts.In the third chapter, halogen substitutes are introduced into the axial ligands of the ruthenium catalysts. It is proved that the hydrophobic effect of the halogen atom dramatically enhanced the reactivity of the catalysts.Chapter four explores a novel group of ruthenium catalysts with imidazole-DMSO pair of axial ligands, in which the DMSO is proved to be crucial for the high efficiency of the catalysts.Chapter five describes the light-driven water oxidation including the three-component system and the sensitizer-catalyst assembled system. It is found that the common Ru(bpy)32+ dye can act as an electron relay and further benefit the electron transfer as well as the photo-stability of the system.In chapter six, aiming to the future application, selected ruthenium catalysts have been successfully immobilized on electrodes surfaces, and the electrochemical water oxidation is achieved with high efficiency.Finally, in the last chapter, a novel molecular catalyst based on the earth abundant metal ?nickel has been designed and synthesized. The activities as well as the mechanism have been explored.