This thesis describes a strategy for deciphering the mechanism for Ru and Os polypyridyl complexes in electrocatalytic ammonia oxidation, a field with significant potential for the future of electrochemistry. Utilizing ammonia as an H2 storage medium and a power source to drive ammonia fuel cells is a promising avenue, but the sluggish reaction kinetics and high overpotentials of electrocatalytic ammonia oxidation reactions present significant obstacles. Overcoming these challenges by developing efficient catalysts will be a milestone in accelerating the adoption of large-scale applications. Mechanism study is key, allowing us to identify favorable pathways and optimize reaction conditions. Understanding how the structure of the catalyst influences its performance and activity will serve as a blueprint for designing the next generation of molecular catalysts. Building on our group's success in using Ru polypyridyl ammine complexes as homogeneous electrocatalysts for ammonia oxidation, we extend this framework to explore insight stoichiometry and prepare Os complexes described in this dissertation. The first chapter introduces the importance of ammonia and the motivation behind developing catalysts for its oxidation. The second chapter details our stoichiometric study for [RuIII(tpy)(dmabpy)NH3]3+, leading to the identification of new intermediates and the proposal of a HAT disproportion mechanism. The third chapter exhibits stoichiometry of [RuIII(tpy)(dmabpy)NH3]3+ derivatives, which strongly support our proposed mechanism. In the fourth chapter, we study the complexes that do not bear coordinated NH3 on polypyridyl complexes, where we learn more about the structure and activity in the stoichiometric aspect, which will be valuable knowledge to electrochemistry. The fifth chapter marks the beginning of our work in using molecular osmium complexes for ammonia oxidation catalysis. Two Osmium polypyridyl complexes were prepared, and their stoichiometries were deeply studied to unveil possible reaction pathways and obstacles in electrochemistry and to understand the influence of chemical structures (metal centers and ligands) in catalytic activity and performance.
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