Design, Synthesis and Study of Multi-Component and Integrated Systems for Light-Driven Hydrogen Generation

Abstract

The final technical report for DE-FG02-90ER14125 (021) covers the period 2006-2009 since the grant represented a one year phase down of the project DE-FG02-90ER14125 (A020). The work during the final year involved completion and publication of studies that are listed at the end of this report. Notable progress was made over the four year period ending February 28, 2010, and the results have contributed to a greater understanding of the complexities and subtleties of this seemingly simple process. In these studies we concentrated on the use of solution luminescent Pt(II) complexes that contain a bi-or terpyridyl ligand for light absorption. These complexes, like the more extensively studied d 6 Ru(II) complexes with similar hetero-aromatic ligands, possess solution luminescent 3 MLCT excited states that can undergo electron transfer reactions.Two different lines of inquiry were followed in the research conducted during the past four years. The first deals with the photo-generation of H 2 employing a multiple component system consisting of a platinum(II) chromophore, an electron relay, a sacrificial electron source and colloidal Pt as the actual H 2 -generating catalyst, while the second concentrates on photoinduced charge separation (PICS) using a similar platinum(II) chromophore covalently connected to spatially specific electron donor and acceptor moieties. The latter has included collaborative transient absorption (TA) measurements on the ns timescale with Professor Russell Schmehl of Tulane University. Photogeneration of Hydrogen.In 2006, we reported that, like [Ru(bpy) 3 ] 2+ , complex 1 can promote the photochemical generation of H 2 in a system containing methyl viologen (MV 2+ ) as the electron relay, triethanol amine (TEOA) as the sacrificial electron donor and colloidal Pt as the H 2 -generating catalyst. The kinetic dependences of both pH and [MV 2+ ] on H 2 generation were found to be non-monotonic, suggestive of the involvement of these