• Holly M. Fruehwald

How I've spent the last 2 years of my life

I wanted to introduce my research and what I've been doing almost everyday of my life for the past two years of graduate studies. In my research I study materials for clean electrochemical energy systems. In my first year I focused mainly on the study of non-precious metal fuel cell catalysts. For those unfamiliar with the types of catalysts used in fuel cells, they are typically platinum-based. Platinum is a rare and expensive earth metal and thus is not (in my opinion) sustainable to use for wide-spread commercial applications in fuel cells. Thus my research is focused on using abundant and cost efficient materials for the development of non-precious metal catalysts. So I used a nitrogen containing ligand (terpyridine) to molecularly attach it to the surface of a carbon support. I could then add iron to create iron-nitrogen coordination motifs on the surface and test that as a catalyst for the oxygen reduction reaction- which is the sluggish reaction in fuel cells that usually requires the most amount of platinum to make the reaction efficient.

To test my materials I used a rotating-ring disk electrode to measure the activity of my materials at the disk, then using a platinum ring I did a collection experiment where I also collected any hydrogen peroxide that was formed in the reaction. By doing this I could determine the number of electrons transferred during the reaction which gives us an idea about how efficient the reaction is. If 2-electrons are transferred that means there is a lot of hydrogen peroxide being formed which is not ideal for oxygen reduction reaction in fuel cells as it can be a catalyst poison. A 4 electron process is ideal as the product of this reaction is only water. So by collecting the amount of hydrogen peroxide produced I could determine how well my catalysts performed. By rotating the electrode at different rpms I was also able to do kinetic studies by plotting the inverse limiting current versus the inverse square root of the rotation rate used.

If you'd like to read more about what I did and the results of these tests, the doi is listed in the publications tab and it is an open access publication :)

The rotating-ring disk electrode set up I used to test my catalysts

More recently I have been using the same catalysts that I described above, but now using them in another clean electrochemical application- Supercapacitors. Similarly to the fuel cell, supercapacitors often use precious metals such as ruthenium oxide as a faradaic reaction to increase the overall capacitance of the material. Using a similar idea as with the fuel cell catalysts can we use nitrogen and iron to increase the capacitance of the material without requiring precious metals? I think so. To determine if my materials could be a good candidate I perform 3-electrode cell tests to assess the charge storing capabilities. Some of the tests I do include cyclic voltammetry at various sweep rates, galvanostatic charge-discharge curves, and electrochemical impedance spectroscopy. Each of these methods (after various calculations) tell me the specific capacitance of my materials and help me to assess if they could be a good candidate or not. Hoping for a publication to come soon on this work!

The 3-cell electrode set up I use to test my materials as a supercapacitor

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