Thesis presented March 28, 2023
Abstract: This thesis is devoted to the development of molecular or hybrid (molecular/inorganic) photocatalytic systems for the photo-induced reduction of protons to dihydrogen (H
2) in purely aqueous solution. The aims were: to identify new efficient and robust catalysts for H
2 evolution, to increase the stability and efficiency of existing photosensitizers and finally to test new photosensitizer/catalyst combinations.
A new rhodium complex with a terpyridine ligand ([Rh(tpy)(CH
3CN)Cl
2]
+) was first isolated and characterized. This complex showed interesting performance as a catalyst for H
2 production under visible light irradiation in the presence of the benchmark photosensitizer, the ruthenium tris-bipyridine complex ([Ru(bpy)
3]
2+) and ascorbate as a sacrificial electron donor. In order to increase the stability of the catalytic systems using the photosensitizer [Ru(bpy)
3]
2+, the latter was substituted by the water-soluble ruthenium tris-dibenzenesulfonate-phenanthroline complex ([Ru((SO
3Ph)
2phen)
3]
4-) which exhibits a twofold higher absorption coefficient and a longer lifetime of its excited state while maintaining quite similar potentials. Combined with a tetraazamacrocyclic cobalt catalyst ([Co(CR
14)Cl
2]
+) and ascorbate, this photosensitizer was shown to be more stable leading to a higher H
2 production during photocatalysis compared to [Ru(bpy)
3]
2+, with nearly 5000 catalytic cycles performed per catalyst molecule in 24 h of irradiation. The last part of this manuscript describes hybrid systems combining inorganic photosensitizers based on semiconductor nanocrystals of cadmium-free CuInS
2/ZnS quantum dots with a molecular catalyst. In order to increase the emission quantum yield of the CuInS
2/ZnS quantum dots, the CuInS
2 core of the latter has been doped with zinc. It was also shown that these quantum dots are capable of activating, in addition to the tetraazamacrocyclic cobalt catalyst, other families of catalysts for H
2 production such as rhodium with polypyridinyl ligands and nickel complexes with phosphine ligands.
Keywords:
Photocatalytic production of dihydrogen, H
2 evolving molecular catalysts, Molecular photosensitizers, Cadmium-free Quantum Dots, Three-component photocatalytic systems
On-line thesis.