Development of visible light photolytic systems for hydrogen generation employing platinum square planar complexes or nanoparticulate nickel as catalysts
Description
The current world demands for energy are continuously increasing. In order to minimize CO2 emission and become independent of foreign oil, it is a crucial time to develop renewable energy sources. Virtually all (non-nuclear) fuel consumption involves oxidation processes. In the search for solar fuels, there is a need to find good reducing agents utilizing sunlight as the energy source. The sun is the most abundant renewable source of energy on earth, delivering a vast amount of energy every day. It is our goal to use sunlight to reduce water to molecular hydrogen, which can then be employed to make liquid fuels through Fischer-Tropsch or other related chemistry. This process will require a catalyst; the best catalyst presently available for water reduction to molecular hydrogen is metallic platinum. Several square planar divalent platinum species have been proven to be quite interesting in regard to their ability to generate molecular hydrogen catalytically during photolysis Platinum is a good catalyst, but the earth's supply of platinum is limited, thus making it an expensive and scarce resource. Nickel, a potential catalyst, is the 18th most abundant element on earth, and is approximately 10,000 times more abundant than platinum. While metallic nickel is known to be orders of magnitude less effective than platinum for hydrogen generation from water, it may still be possible to make functional nickel based systems by exploiting advantages commonly associated with nanoparticulate catalysts such as high surface to volume ratios. Stabilized nickel nanoparticles (2-5nm) are a very desirable catalyst for photolytic hydrogen generation because they form a uniform colloidal suspension with minimal light scattering Photolytic systems utilizing a ruthenium chromophore, nanoparticulate nickel with polymer support, and an electron donor in methanol as the solvent are investigated. This system when photolyzed generates molecular hydrogen with a total turnover number (TN) of 44 (relative to the Ru complex chromophore). The ultimate goal is to modify this system to use water as the solvent with a non-sacrificial donor and to ultimately have a catalytic system for water cleavage to hydrogen and oxygen