Analysis of Diffusion Coefficient Data using Rotating Ring Disk Electrode for Symmetric Non-Aqueous Redox flow Batteries

Nathan Barr and Thomas Guarr

As the world becomes more electrically focused, the resources needed for manufacturing batteries are in lower supply, and the collection of raw materials causes adverse effects on the environment.  Due to this, interest in more sustainable batteries, such as nonaqueous redox flow batteries (RFBs), has dramatically increased.  Recent research efforts have focused on improving the energy density and power density, two key measures of battery performance.  In RFBs, these two parameters depend on numerous factors, including the solubility, redox potential, electron transfer kinetics, and diffusion coefficient of the active material.  Previous work in our lab demonstrated a wide range of pyridinium electrolyte redox potentials, as well as the ability to drastically alter their solubilities through minor structural modification.  This work presents diffusion coefficient data of a structurally diverse set of pyridinium salts using a rotating ring-disk electrode (RRDE), with the goal of analyzing how different functional groups may have positive or negative effects on the diffusion coefficient, and how these pyridiniums can be modified to achieve greater stability in the reduced state without sacrificing other important attributes.

Nate is studying Chemical Engineering at Calvin University.  I always appreciate having an engineer to contrast with our chemists and Nathan did not disappoint!  He brought a lot of enthusiasm to his project and made some very interesting and unexpected discoveries.  Nate is thoughtful and thorough with his experiments and we really enjoyed having him in the lab to counteract our synthesis-heavy summer.

Increasing the Energy Density of Redox Flow Batteries Using Pyridinium Compounds Displaying Two Reversible Reductions

Sophia Valdivia, Madison Shaffer, Andrii Varenikov, Thomas Guarr

Redox flow batteries (RFBs) are gaining interest to make energy storage more affordable and efficient.  RFBs are an energy storage device that relies on the oxidation and reduction of soluble electroactive chemical species for charging, storing, and discharging energy.  Redox-active organic molecules (ROMs) are promising electroactive materials due to their low production costs, low molecular weights, and the ability to achieve significant electrochemical potential differences between the anolyte and catholyte.  Previous research has shown that pyridiniums with 1-electron systems provide reduction potentials between -1.5 V and -1.8 V, but they were not sufficiently stable.  This work aims to increase the battery’s energy density by synthesizing a pyridinium with a 2-electron system while stabilizing the first reduction.  Using cyclic voltammetry, the reduction potential is determined, and insight is gained about the stability of the radical.

Sophia first heard about our lab when Tom Guarr visited his alma mater, Benedictine College, to give a talk about his research.  She attends Benedictine in Kansas, but she is from Texas and she had never been to Michigan before.  She was very interested, applied, got accepted, packed up and came to Holland for the summer.  She did some great synthesis work and we loved having her here!  Thanks to Benedictine for sharing her.

Increasing Electrochemical Versatility by Linking Ferrocene to Pyridinium Salts

Riley Clark, Madison Shaffer, Thomas Guarr

Flow batteries have become increasingly popular due to their increased lifespan and ethical sourcing of raw materials.  While aqueous flow batteries have been studied for decades, nonaqueous organic flow batteries are generating new interest because of their higher cell voltages, greater structural diversity, and low manufacturing costs.  This work focuses on linking ferrocene catholytes to pyridinium anolytes to produce molecular systems that can be both reduced and oxidized.  By using this approach, the expensive ion-selective membrane normally used in flow batteries can be replaced with a simple, inexpensive porous separator.  Numerous synthetic pathways to such compounds have been explored, however the most promising of these involves the synthesis of substituted nitrophenyl ferrocenes via Suzuki coupling, followed by the reduction to produce an amine, and finally condensing the ferrocenyl amines with a pyrilium salt.  Further work involves testing the electrochemical properties, solubility, and stability of these compounds.

Riley is our first highlighted intern and she comes to us from Clemson University.  One of her mentors there was a former intern of ours and she came to us highly recommended.  Riley did some great synthesis work and her accomplishments are even more amazing when you consider she has only completed one year of undergrad!  We appreciate that she spent her summer with us when most people her age are working summers part-time scooping ice cream or something.  You are a very impressive person, Riley!  When the winter gets too long up here, we are going to take a field trip to South Carolina to visit.

Thanks again to Hope College for inviting us participate in the 2024 Chemistry Summer Symposium.  Our group presented 6 posters and 1 talk.  We enjoyed all of it!

Summer isn’t over yet, but I want to talk about all the great things that have been happening since my last post.  We are so fortunate here at the OESLab to enjoy so many different, fun and interesting people that come through the lab.  This summer is certainly no exception!  I will highlight each intern in future posts, but here are some fun pics of the group…