Update 5: Putting the Error in Trial and Error

Last week I performed concentration studies with a sacrificial electron donor (SEC) in hopes of establishing a photocatalytic system that produces hydrogen gas. Unfortunately, these experiments were unsuccessful and produced no hydrogen. This may be a result of incompatibility between the catalyst and chromophore used and the sacrificial donor. Luckily, there are many other catalyst/chromophore combinations available to experiment with.

This week I experimented with another combination, as detailed in this JACS (Journal of the American Chemical Society) paper. First, I ran the experiment as detailed in the paper to ensure I was setting everything up correctly. This went smoothly, so I set up an experiment with the same conditions but replaced the sacrificial donor with the lowest concentrations of SEC from last week’s experiments and used blue LED lights. Gas chromatography analysis (GC) showed no production of hydrogen so I repeated the experiment using green LED lights instead. Again, GC analysis showed no hydrogen.

After getting these results, I returned to the JACS paper. I noticed that they cited the optimal pH for the system as pH = 6. pH analysis of my photochem test tubes showed pH = 4. I repeated the experiment with adjustment to pH = 6. To my disappointment, GC analysis still showed no hydrogen production. Maybe this combination of catalyst/chromophore is the problem.

At the end of the week I began experimenting with catalyst/chromophore combo #3. First, I used a sacrificial donor known to work with this system to verify that it works and make sure I don’t butcher the procedure. GC analysis of this initial experiment showed small amounts of hydrogen gas. Are there better conditions in which this catalyst and chromophore work? Next week I want to work towards optimizing this before introducing the SEC into the system.