Update 6: pH Problems and a New Project

Last week, I ran into problems when using my third catalyst and chromophore combination. Over the weekend I learned that the chromophore I was using works best at pH = 7. The solution of sacrificial electron donor that I use is pH = 7, but I have been diluting it with deionized water. The pH of deionized water is closer to pH = 6, so the lower concentrations have less optimal pH. Therefore, I started the week by running one photochem experiment as-is and one photochem experiment with pH adjustment for each dilution. However, gas chromatography analysis of these experiments showed no hydrogen production. I keep a lab notebook (as record of the work I do in lab), and that day’s entry is “No hydrogen. Only air. Morale is low.”

Unsure of how else I could improve this system, I put this part of my project on hold. One of my peers in lab had synthesized a complex and had been running cyclic voltammetry to verify its activity as an electrocatalyst. As Resident Photochem Person (RPP) for the summer, I was asked to start testing its ability as a photocatalyst. I ran one experiment with this catalyst overnight.

The next day, I added methane gas as a standard to the previous photochem experiment. After gas chromatography analysis, I was able to integrate the hydrogen and methane peaks and calculate turnover numbers (TONs) for hydrogen production. TONs were relatively inconsistent, so I plan on repeating the experiment next week for more data points.

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