Author: Lucy Vaughn | Major: Biochemistry | Semester: Fall 2024

Lucy Vaughn presenting her research at the Honors Chemistry Symposium

Blog Post: During the 2024 fall grant term, I continued working with my mentors Dr. Stefan Kilyanek and Dr. David Paul, assessing the ability of polymer Nafion to act as a conductive film to trap phosphomolybdic acid (PMA) atop a glassy carbon electrode. My goal for this semester was to refine the technique for enclosing PMA on an electrode within the Nafion polymer, then to pivot towards using another polymer to compare their capabilities. As a biochemistry major, I have greatly enjoyed the hands-on lab work with various compounds and machinery. Learning the properties of PMA in different polymer films as it acts as a catalyst for water electrolysis will assist in the overall goal of maximizing the efficiency of leveraging polyoxometalates (POMs) – like PMA – in hydrogen generation.

As a sophomore taking Organic Chemistry lab, I met my lab TA Cody Canote, who was a graduate student in Dr. Kilyanek’s lab. He introduced me to Dr. Kilyanek, who presented me the opportunity to work in his lab on the project of suspending phosphomolybdic acid in conductive polymers (CPs).

I began research in the Kilyanek lab in the summer 2023 semester, and began studying the effects of solution pH on the redox potentials of PMA. Trials from these studies showed that PMA was easier to reduce in acidic conditions as opposed to basic conditions. During the fall 2023 semester, I studied the ability of PMA to accept protons from water. This study yielded information about the solubility of PMA in water along with useful electron transfer data.

I worked alongside Dr. David Paul during the summer 2024 semester to successfully suspend PMA in Nafion, a conductive polymer used as a film to cover the surface of a glassy carbon electrode. Dr. David Paul has been an immense help in my thesis research; he is extremely knowledgeable in the electrochemistry field and it has been such a blessing to work alongside him for this past year. Dr. Stefan Kilyanek, my thesis mentor, has also been a tremendous help in determining what direction to shift my project in as new challenges arise.

Over the summer, we tested out various dilutions of Nafion, and struggled to find one that fully trapped the PMA onto the electrode. In high concentrations of Nafion, the film has cracked, through which the PMA falls through and into the solution. In low concentrations of Nafion, the PMA is barely detectable. During the fall semester we discovered, through several avenues of trial and error, that diluting the Nafion with ethanol and sonicating this solution after adding the PMA was the solution to our problem. With this obstacle eliminated, we continued to test the capacity of Nafion to support PMA in oxygen evolution and hydrogen evolution reactions.

My studies have shown that the potential at which oxygen is reduced is consistently smaller in pH 7 (phosphate buffer solution) than pH 0 (perchloric acid buffer solution), while hydrogen reduction occurs much quicker in acidic solutions than it does in basic solutions. Though these results are promising, we ran into some issues with our cyclic voltammetry scans. As we continued to test the efficiency of the Nafion/PMA film while adjusting factors like the concentration and electrolyte, we discovered that these reactions were resulting in unusual oxidation peaks on the electrode. Through a process of elimination, we found that the glassy carbon substrate was not inert for oxygen evolution reactions, as the carbon oxidizes to another form. Though the Nafion/PMA film showed promise as a catalyst for hydrogen and oxygen reduction, the scans were unreliable on the glassy carbon electrode.

Due to the issue with the carbon substrate, we decided to pivot to using a platinum electrode, which is generally more electrochemically inert. With this platinum electrode, we decided to begin working on entrapping the PMA in a eugenol film. Eugenol is another conductive polymer that can be electropolymerized to entrap catalyzing compounds like PMA. This polymer was quickly ruled out as an option to work in, as it was far too insulating to allow the PMA to have any effect on the onset potentials. With eugenol ruled out as a promising CP, we are now aiming to trap the PMA in polypyrrole following procedures found in literature for electro-polymerization.

For the spring semester, I plan to wrap up my research by working with polypyrrole as a polymer to entrap the PMA in for the water splitting half-reactions. Should this polymer also be quickly eliminated as an option, we will shift to using polyaniline or poly(3,4-ethylenedioxythiophene) to construct other polymer/PMA films to compare their efficacy with the Nafion/PMA film.  As this is my final semester at the University, I plan to present my findings in my thesis defense this semester.

While working on my project in this lab, I have come to view unexpected challenges as valuable data rather than delays. The PMA has rarely performed as anticipated, often requiring meticulous testing to pinpoint the issue. Although the lab work can sometimes be challenging to interpret, these experiences have provided me with countless opportunities for learning and growth that I hope to apply in my future career.

The Honors College Research Grant has graciously allowed me the flexibility to continue my studies on this topic that has become an integral part of my education. I have learned about the promising properties of polyoxometalates as water electrolysis catalysts and I am eagerly looking forward to presenting my findings this semester. I am extremely grateful for the opportunities I have been kindly presented with by Dr. Kilyanek and Dr. Paul and for the support of the Honors College in my research endeavors for the past two semesters.