Catalytic Properties Of Non-Noble Metal Complexes Containing Bipyridyl-Derived Ligands For Visible-Light-Driven Hydrogen Production

The development of our society is limited by the shortage of energy and environment pollution. Therefore, more and more scientists pay their attention toward the artificial photosynthesis of the conversion of solar energy into stored chemical potential in the form of fuel. The light-driven conversion of protons into H2is one of the important issues in the artificial photosynthesis as H2is a recyclable green energy source with high energy density.A homogeneous photocatalysis system generally consists of a photosensitizer, a catalyst, and a sacrificial electron donor. Catalysts based on platinum, rhodium, ruthenium, and palladium have been frequently employed because of their high activity; however, high material cost has limited their application. Therefore, exploring less expensive and high active catalysts based on non-noble metals is important for the production of H2in a large scale.For these problems existing in the present homogeneous photocatalysis systems, we choose the complexes [M(L1)2(H2O)2](BF4)2(L1=2-(2’-pyridyl)-1,8-naphthyridine; M=Ni,(1); M=Co,(2); M=Fe,(3)) and [Cu(L1)2(H2O)](BF4)2)(4) containing internal base(s) as catalysts and fluorescein (Fl) as photosensitizer to construct completely noble-metal-free catalytic systems for photochemical H2production.In this thesis, firstly, we choose complex1as catalyst to explore the property of the homogeneous photocatalysis system. The results of experiments are as follows:a) The optimized conditions for photocatalytic H2production by these systems are [1]=2.5×10-6M,[Fl]=2.0mM, pH=10.54, TEA (5%v/v) in CH3CH2OH/H2O (1:1,5.0mL); b) Studies on the homogeneous system show that hydrogen formation proceeds through electron transfer from PS*to catalyst in the photochemical process; c) Under optimal conditions, the activities of complexes1-4were explored and the results show that the H2-evolving activity of1is higher than complexes2-4. This result shows that the metal center is a key factor to influence of the activity for homogenous system for hydrogen production; d) Compared with the hydrogen production activity of [Ni(L2)3](BF4)2)(5)(L2(2-(2’-pyridyl)-quinoline) without internal base, the activity of complex1is better than complex5. The result displays that the internal base of1may act as a proton relay that is convenient for delivering protons so as to improve the rate of hydrogen production; e) The deactivation of the systems is mainly caused by the decomposition of complex1.