Doctor of Philosophy
Solar hydrogen production via artificial photosynthesis has the potential to provide clean and renewable fuel for the worlds increasing energy demands. The availability of efficient, robust, and low-cost catalysts capable of splitting water into oxygen and hydrogen is critical for future applications. There has been significant progress in designing molecular catalysts for hydrogen production based on earth-abundant metals such as Ni, Co, and Fe. Hydrogen production based on metalorganic-framework (MOF) templates has also received great interest over the past few years. Among the reported catalysts for H2 production, cobalt complexes with polypyridyl groups have gained much attention because of their stability in aqueous solutions, avoiding the use of organic solvents for electro- and photolytic production of hydrogen. In this dissertation, recent development of metal complexes for photochemical and/or electrochemical H2 evolution was summarized. Herein five novel cobalt complexes for photocatalytic and electrocatalytic H2 production were reported. Based on complex [Co(DPA-1-MPI)(H2O)](PF6)3 (3b) and [Co(DPA-3-MPI)(H2O)](PF6)3 (4b) with similar structures while displaying significant reactivities difference, it is demonstrated that a conjugated and planar bipyridyl unit or its isoquinoline analogue plays a key role for H2 evolution catalysis, and such a planar and conjugated structural feature could promote stability to the low valent CoI species. Besides, the substitution of a tertiary amine with a softer pyridine group, in combination with a conjugated bpy unit to afford complex [Co(Py3Me-Bpy)(OH2)](PF6)2 (7b) significantly improves the stability and activity of catalyst for both electro- and photocatalytic hydrogen production reaction (HER) in neutral aqueous solutions, which may provide new guidelines for the design of next-generation catalysts.
Dissertation or thesis originally submitted to ProQuest
Wang, Ping, "Electro- and Photocatalytic Hydrogen Production by Molecular Cobalt Complexes with Pentadentate Ligands in Aqueous Solutions" (2020). Electronic Theses and Dissertations. 2976.