Application Of Organic Photosensitizers In Photoinduced H₂Production System

The current global energy crisis and environmental pollution are more and more serious. Hydrogen has long been considered as an ideal substitute for fossil fuels because it is a clean and efficient energy source. It has attracted more and more attention in recent years. Scientists are sparing no efforts to find ways for conversion of solar energy into molecular hydrogen. Designing and constructing of efficient and cheap homogeneous systems for photocatalytic hydrogen production is one of the ways to this goal. In this dissertation, two organic photosensitizers coumarin organic dye P1and this is the first time to use a coumarin organic dye as a photosensitizer in photocatalytic H2production system; xanthene organic dye P2. Some cobaloximes were used as catalysts, which are the functional mimics of the active site of hydrogenases. Their structures are similar to the cobalt complex in vitamin B12. These cobalt complexes exhibit good activity in photocatalytic hydrogen production.First, the coumarin organic dye P1was applied as a photosensitizer in photoinduced H2production system with cobaloxime complex Cl and C2as catalysts. Hydrogen was detected by GC analysis from the photocatalytic reaction system. Under optimal condition, the lifetime of system is about12h. Through the thermodynamic analysis, it was feasible that electron transfer from photosensitizer to catalyst. The quenching of fluorescence emission studies show that the electron transfer from the singlet state of P1to catalyst was not an effective way. The formation of a reduced Co1intermediate was evidenced by UV-vis spectroscopic monitoring of the reaction. The electron transfer from the triplet state of PI to catalyst, which was proposed on the basis of the results obtained from laser flash photolysis spectroscopic studies. Second, xanthene organic dye P2was applied as a photosensitizer in photoinduced H2production system with cobaloxime complex C1, C2and C3as catalysts. Hydrogen was detected by GC analysis from the photocatalytic reaction system. Under optimal conditions, the TON of system is up to51. The lifetime of the system is about5h; the system can also produce H2in the photocatalytic reaction in fully aqueous solution. The photoinduced H2generation reaction was monitored by UV-vis spectrascopy.