Synthesis and Connection of Iridium Hydrogen Evolution Catalyst to Chlorella vulgaris Photosystem I for Light-Driven Hydrogen Evolution
Hydrogen gas has been shown to be a promising energy source as options other than fossil fuels are being looked at in the face of anthropogenic climate change. It is known that anthropogenic climate change is caused by the production of greenhouse gases being let into the atmosphere, specifically a common reason for this is the burning of fossil fuels for energy. The overall goal of this project is to design a biochemical hybrid system that will be used to make H 2 gas and does not require the use of fossil fuels. Burning hydrogen as fuel produces only water as a byproduct, making it a clean and renewable source of energy. Hydrogen bonds are known to store a large amount of chemical potential energy. When this bond is broken, typically through burning the gas, this energy is released and able to be used. There is technology currently available such as hydrogen fuel cell cars, but the main source of hydrogen gas comes from the burning of fossil fuels. In order for this technology to benefit the environment, a clean way to make hydrogen fuel must be found. The specific goal of this project was to covalently attach an iridium catalyst to photosystem I (PSI), which is a complex that is involved in energy production via photosynthesis. The catalyst was covalently attached to Cys 33 of photosystem I (PSI) which has been isolated from Chlorella vulgaris . When light hits PSI, electrons become excited and go through the system, reaching the iridium catalyst which converts protons into H 2 gas. PSI is photosynthetic, and acts in photosynthesis to take energy from the light produced by the sun and transform it into energy that is useable for the plant. This same mechanism is what makes it a good fit for this system, as the sunlight will provide the
energy needed and this protein will do the same job it normally does, just with different components after it, rather than the rest of the photosynthetic electron transport chain. Similar to its role in photosynthesis, plastocyanin will be used to carry electrons to PSI. The difference here is that these electrons will be coming from an electron donor, sodium ascorbate. After going through PSI, the electrons will travel through the connected [Cp*Ir(bpy)(Cl)][Cl] catalyst where it converts to protons (H + ) to H 2 gas. This system was able to produce 1.3 mmol of hydrogen gas after being assembled and exposed to light at a level of 6050 Lux for 19 hours.
Biology and Chemistry
Dr. Sarah Soltau, Thesis Advisor
Dr. Heather Marella, Thesis Advisor
Dr. Edward Brush, Committee Member
Dr. Jonathan Roling, Committee Member
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Original document was submitted as an Honors Program requirement. Copyright is held by the author.
Ramirez, Anna. (2019). Synthesis and Connection of Iridium Hydrogen Evolution Catalyst to Chlorella vulgaris Photosystem I for Light-Driven Hydrogen Evolution. In BSU Honors Program Theses and Projects. Item 306. Available at: https://vc.bridgew.edu/honors_proj/306
Copyright © 2019 Anna Ramirez