Hybrid Supramolecular Water Oxidation Catalysts for Massive Electrochemical Response

• Applicant: Dr. Jan Christian Oldengott
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2018 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 404574441

The regenerative storage of solar energy in chemical bonds is performed by nature for millennia in photosynthesis. The development of artificial photosynthetic devices can have a huge share in changing the energy production from fossil fuels towards renewable energy sources. Energy stored in chemical bond has a high energy density and is easy to transport. Thus, chemical energy carriers can be easily stored and used decentralized by established techniques, which is a crucial advantage over electric generated energy, e.g. from solar cells. The bottle neck in the development of artificial photosynthetic systems is the oxidation of water to dioxygen. The synthesis of molecular catalysts for water oxidation has made huge advantages over the last years and reaction rates are now comparable to those in nature. The project intents to further increase the reaction rates and the stability of molecular water oxidation catalysts for application in water splitting devices. Increased understanding of the reaction mechanisms in water oxidation catalysis led to the development of the, up to now, best molecular water oxidation catalyst [Ru(tda)(py)2] by Prof. Llobet and his coworkers at the ICIQ in Spain. The dioxygen bond is built by this catalyst via an electrophilic attack of a polarity inversed Oxygen atom on a water molecule. In nature, the activation energy for this electrophilic attack is reduced by the pre-organization of water molecules by a protein environment. In the first part of the project this pre-organization should be introduced by a macrocyclic arrangement of Ru-tda catalysts. Therefore, I want to combine the Ru-tda catalyst with different bipyridyl ligands, to create supramolecular catalysts with varying cavity sizes. The obtained coordination oligomers will then be subject to intense structural and electrochemical investigation to determine the influence of the cavity size on the catalytic properties. I want to use the results from this first part to design 1D, 2D, and 3D coordination polymers with defined, optimal pore sizes based on the Ru-tda catalyst linked by polypyridyl ligands. Such porous metal organic frameworks will be ideally fit to pre-organize water molecules in their cavities, which should enhance the reaction rate of the catalyst while providing elevated stability. Thus, polymeric water oxidation catalysts can make a huge contribution to the development of artificial photosynthetic devices.

• DFG Programme: Research Fellowships
• International Connection: Spain
• Host: Professor Dr. Antoni Llobet