Theoretical modeling of heterolytic mechanism for H2 production: A detailed investigation of Cobalt(II)-polypyridyl catalyst

Hydrogen (H2) molecule is a remarkable carrier of energy that is found naturally in biomass, water, and hydrocarbon. Solar energy is the most abundant energy source, which plants inherently uses to feed their photosynthesis mechanisms. Hereupon, researchers gain inspiration of these nature's great event, the light reactions of impeccable H2 production pathway of photosynthesis. In order to mimick the water reduction mechanism of photosynthesis, various transition metals have been employed. However, a satisfactory solution couldn't been found in the terms of price/performance ratio. Recently, researchers have investigated photocatalytic water reduction by taking advantage of Cobalt based photocatalysts. In this connection, by applying Ab-initio Molecular Dynamics simulations as well as Density Functional Theory, and Free Energy Perturbation Theory, we investigate water reduction, also known as H2 production, mechanism of Co-based poly-pyridyl catalyst having perfect octahedral coordination. At this thesis, our aim is to clarify the effect of regulation at octahedral coordination and compare the two pathways of, ECEC and EECC, H2 production mechanism. Consequently, for the hydrogen production cycle, both ECEC and EECC mechanisms are utilized and each intermediate step is simulated in order to determine the allowed spin states as well as solvent response around the reaction center of Co-based water reduction catalyst investigated. Furthermore, by performing additional simulations the electronic structures of each intermediate step of both mechanisms have been analyzed. Reduction free energies have been calculated using Marcus theory of electron transfer.