Computational Study and Design of Transition Metal Complexes for Ammonia-Borane Dehydrogenation

Gogoi, Amrita (2024) Computational Study and Design of Transition Metal Complexes for Ammonia-Borane Dehydrogenation. PhD thesis, Indian Institute of Science Education And Research Kolkata.

Text (Phd thesis of Amrita Gogoi (18RS022)) 18RS022.pdf - Submitted Version Restricted to Repository staff only Download (7MB)

Abstract

“Hydrogen Economy” has been addressing the world’s increasing energy demands. Despite being one of the sustainable sources of energy, there is a prominent struggle for its approaches towards practical applications, e.g., on-board storage processes and methods. Out of many such procedures, Chemical Dehydrogenation of molecules/materials has been a promising outlook. Here, compounds such as chemical hydrides are favourable because of their high hydrogen content in which non-metal hydrides are preferred more and one such example is Ammonia-Borane (NH3BH3, AB). Apart from having a high gravimetric hydrogen content, AB is known to be light-weighted, non-flammable and air-stable, having an abundant AB chemistry. In this thesis, the contribution of AB towards hydrogen storage has been highlighted through the Dehydrogenation of AB using transition metal-based catalysts. Herein, a computational investigation using Density Functional Theory (DFT) has been carried out to study and analyse the transition metal complexes in terms of their efficacy towards AB dehydrogenation and also model them further for better efficiency in terms of cost and energy. Initially, a Ru-based complex was chosen which shows promising results for AB dehydrogenation and has been backed by both experimental and computational studies, but it lacked some of the in-line explanations between them. In this, the gap between the experimental and theoretical findings has been bridged and the final picture of the catalytic activity of the complex has been shown. Thereafter, an Fe-based transition metal complex has been studied which is a modelled counterpart of the previously studied Ru-based complex and in here the comparison of the catalytic activity of the original and the modelled catalyst has been demonstrated. And finally, a series of high-valent transition metal complexes which are precisely known for C-H activation have been investigated for AB dehydrogenation and have been designed further to understand and boost their catalytic activity.

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