| This work is aimed at building a zeolite based hydrogen evolving artificial photosynthetic system. Toward this goal, we have adopted the well-known sacrificial DS-A model, EDTA Ru(bpy)32+-bipyridinium-catalyst scheme. The stability of the sensitizer, Ru(bpy)32+ was evaluated under photolytic conditions by developing a chromatographic method to separate, quantitate and identify the decomposition products. Effect of various photolytic parameters like zeolite encapsulation, pH, photolysis time, quencher concentration, nature and concentration of buffers were studied to find the optimum conditions where the decomposition could be minimized. It was found that the extent of decomposition is dependent on the nature and concentration of the buffer anion and decreases with increasing quenching efficiency in the presence of quenchers.; It is well known that the electron acceptor employed in this system, bipyridinium is susceptible to decomposition under H2 evolving photolytic conditions, limiting the practical applicability. The catalyst involved in the electron transfer from the relay is widely believed to be responsible for this limiting condition. Our research group has earlier developed a zeolite-based RuO2 catalyst for the photooxidation of water to O2. This catalyst was evaluated for the photoreduction of water to H2 using the above-mentioned system and was found to be effective. Performance of this catalyst was compared with other known catalysts as for as rate of hydrogen evolution, stability and the rate of bipyridinium decomposition. Attempts were made to selectively poison the sites responsible for the bipyridinium reduction, while keeping the sites involved in the H2 evolution unperturbed. The sensitizer was also covalently linked to the zeolitic surface that also contains the catalyst as a first step toward a proposed integrated solar water splitting assembly.; Intrazeolitic electron transfer was studied with zeolite encapsulated Ru(bpy)32+ and bipyridinium ions. Molecular modeling of guest species in constrained zeolitic cages involved in photoelectron transfer allowed to gain insight into their restricted rotational and diffusional mobility. A systems dynamics modeling approach was employed to simulate the intrazeolitic electron transfer processes and the developed model allowed the extraction of various kinetic parameters. We propose that the zeolite architecture plays a crucial role in aiding long-lived charge separation. |
