Photooxidation of organic substrates coupled to the reduction of protons:Sustainable hydrogen production – HYPHO

Hydrogen is called to play a crucial role in the energetic future of the world. However, an economy based on hydrogen is not ready yet. This for several reasons, for instance, its production, storage, transport, safety and efficiency need to be mastered. Among these problems, perhaps the most important one is the production of H2. For now, polluting cracking of organic compounds and expensive electrolysis methods are available to do so. It is therefore urgent to develop sustainable production of hydrogen. In this project, we want to invent new non polluting processes for the production of H2 to replace these short terms production processes mentioned above. The strategy we want to follow is based on the use of sunlight to drive on one hand the photooxidation of organic substrates leading to high value added compounds and on the other hand to recover the electrons from this process to reduce protons to hydrogen. This project involves synthetic chemists, solid state chemists and photophysicists. The synthetic chemistry part of the project is composed of two main parts: I. In one, we want to elaborate novel mixed Ruthenium-Transition metal (Manganese, Iron ...) complexes to perform the oxidation of organic substrates driven by light excitation of a Ru(II) polypyridine type complex. These systems can be considered as supramolecular devices, where the ruthenium(II) polypyridine type complex is responsible for the conversion of the light energy into chemical energy (charge separation) and the transition metal ion complex covalently tethered to the lumophore is the catalytic site for the oxidation process. Under irradiation the ruthenium complex ejects an electron (captured by an electron acceptor) and the highly oxidising Ru(III) ion strips one electron from the transition metal ion complex through an intramolecular electron transfer process thereby rendering the latter oxidising. This process can be repeated twice to generate high oxidation states capable to oxidise organic substrates such as alcohols, alkene ...etc II. We will also develop transition metal complexes capable to reduce protons to hydrogen. In our lab we have already in hand a cobalt complex capable to reduce protons at quite high potential. We need to fine-tune the electrochemical properties of this family of complexes through chemical modifications at the periphery of the ligand. The final step will be the construction of a solid state device where our photocatalysts will be fixed on electrodes allowing to recover the electrons from the photooxidation part and to reduce the protons in the second half cell at a modified electrode containing our coordination metal complexes as electrocatalyst.