Viologen-Mediated Direct Carbohydrate Fuel Cell 1

Dear Dr. Dean Wheeler,

My name is David Brosnahan and I was a undergraduate research assistant with Dr. Gerald Watt from 1997 to 2000 and a graduate student from 2000 to 2002. After completing a masters degree in biochemistry, I went on to medical school and on to complete an emergency medicine residency. However, today while surfing the web, I came across the following abstract regarding Methyl Viologen and Glucose Fuel Cells at the website for an 2008 electrochemical meeting in Japan (see link below). I saw your name first of the abstract and I wanted to give you some background into how Dr. Watt got involved with this project.

Dr. Watt had two main projects. His primary project was Nitrogenase. He wanted to understand how Nitrogenase worked so he could replace the inefficient Haber-Bosh process to fix nitrogen into ammonia. His secondary project was ferritin, which is involved in iron metabolism in the body. When I started with the lab in 1997, our lab had national grant funding for both projects. But a year later, the government agency funding our nitrogenase research categorically withdrew funds in this area. Several years after that our ferritin funding ran out. We had been in a publishing drought because we had the correct but conflicting result with another lab who held the political and publishing high ground. The lean years that followed in the Watt Lab were very frustrating but resulted in our expanding our research into new areas. We had to evolve, publish, and compete for grants or die. The best way I and Dr. Watt saw to becoming competitive was to develop projects in the areas of nano-technology and fuel-cells. These were the emerging fields then as they still are today. Before I left,we began to collaborate with with the ChemE department and with other in our department on the nano-battery project. I was pleased that Dr. Watt had the opportunity to take a sabbatical at Langley Research Center to develop his idea. It was fun to brainstorm at the beginning of the project how the heat-stable and self-assembling ferritin protein could be arranged to work as a nano battery.

It was about this time when issues or global climate change and energy independence were rising in the public consciousness when a mishap in the lab got me thinking about fuel cells. We were anaerobically separating the nitrogenase protein using ion-affinity column chromatography when another hydrogenase enzyme in the mixture together with sodium dithionite catalyzed the electrolysis of water and the evolution of large amounts of hydrogen which completely interrupted the separation and the column. Upon observing the hydrogen evolution I kinda had an ah-hah moment and started thinking along the lines of a microbial or enzymatic (hydrogenase) fuel cell that would evolve hydrogen from dithionite. However, the idea of continually having to ferment bacteria, over-express and purify enzyme, and continually replace biological catalysts didn't seem to me like it was a system that would meet the global power demands of the planet (I could be wrong).

So, I started thinking about more direct methods to evolve hydrogen or directly reduce organic molecules. While working with Dr. Watt on a project related to the redox properties of ferritin and other metaloproteins, we routinely used a Coulometer to measure redox properties of redox-active metaloproteins. However, enzymes do not interact with metal electrodes directly, so Methyl Viologen or Paraquat was used to mediate the interaction. I thought, If methyl viologen could mediate between protein and anode, they maybe it could mediate between a hydrocarbon or partially oxidized hydrocarbon and the anode. Methyl viologen works because it its singly and doubly reduced states its heterocyclic, aromatic, conjugated, pi-electron system stabilizes a free radical state which then freely interacts with the anode. This is similar to how the body does it using biological mediators such as NADH, FAD, etc.

So, I started playing around in the lab and MacGyvered a table-top anaerobic fuel cell using methyl viologen added to various hydrocarbons. I tried hexanes, phenol, methanol, formaldehyde, and formic acid as well as glucose under various pH and temperature conditions. Glucose seemed to work the best. However, I didn't know at the time to what extent the glucose was being oxidized. Glucose is a reducing sugar and it is not difficult to get an electron pair out of it. I had tried to measure evolved carbon dioxide without success using GC. However, I stumbled upon the following abstract for a 2008 electrochemical meeting (see link below) and I was excited that your abstract mentioned that you and Dr. Watt had fully oxidized glucose to carbonate. I am excited that someone from the BYU ChemE Department took an interest in this problem. Before leaving BYU, I unsuccessfully tried to get Dr. John Harb involved with the project. However, I think Dr. Harb was more interested in collaborating with Dr. Watt on the ferritin nano-battery project then the fuel cell idea.

The purpose of this email is to verify that you are working on the MV fuel cell project. And if it is, I just wanted to let you know where I left off, and some of the problems I had talking this project any further. As you already alluded to in your abstract, designing a fuel cell which runs on glucose would be a historic breakthrough. Glucose derived from switch grass and other cellulose-based sources is 100% renewable. In addition, as you alluded to in your abstract, designing a fuel cell without needing gold or platinum in the reforming system, anode, or membrane (PEM) is a major hurdle to making fuel cells a viable answer to global energy needs and energy independence here in the US.

However, the major hurdle I faced was developing a fuel cell with adequate current per area. I could get 0.5 V short circuit voltages, but no milliamps. And this is because the reaction in solution is rate limited by the concentration of the MV. For a current to be generated a molecule of glucose would have to collide with a MV molecule which would then need to collide with the anode. That would result in a second order reaction dependent on a small concentration of MV in solution. However, if the MV mediator could be somehow directly associated with the anode, then the reaction would become first-order and dependent only on the concentration of glucose in solution. And glucose is very soluble. It seems from the abstract that you and your team figured out how to make this work. I couldn't think of a way to make a MV anode. I didn't know how to create a MV thin film, or polymerize MV. I discussed with Dr. Harb talking solid MV salt and mixing it straight with plasticizer and seeing if that worked. According to the chemical equations, I'm not sure if water was involved in the redox reaction. Looking up in Google, there are several groups that have discovered how to polymerize MV. If the polymerized MV is conductive or can be directly associated with an anode material, this may be a breakthrough.

Also, one more interesting characteristic of MV is that it can be doubly reduced into a quinoid form is soluble in organic solutions. Both the singly and doubly reduced MV forms carry out the electrolysis of water and form hydrogen gas using a variety of catalysts and photo-catalysts.

I apologize for the length of this email. I would appreciate any reply or information on the progress of this project. I am 100% into medicine now, but like to follow the progress of the research I was once briefly a part of.

Sincerely,
David D. Brosnahan

1. MV thin film patent: http://www.freepatentsonline.com/4144143.html
2. MV doped silicate anode and methanol Optical Materials Volume 22, Issue 3, May 2003, Pages 221-225 Electroreduction of methyl viologen in methanol and silicate thin films prepared by the sol–gel method
3. MV polymers Journal of Polymer Science: Polymer Chemistry Edition Volume 21 Issue 1, Pages 293 - 300 Preparation of viologen polymers from alkylene dipyridinium salts by cyanide ion
4. MV vs. MV polymers and electroysis J. Chem. Soc., Faraday Trans. 2, 1982, 78, 1937 – 1943Viologen/platinum systems for hydrogen generation
5. MV nanoparticles Electrochimica Acta Volume 53, Issue 26, 1 November 2008, Pages 7655-7660 Electrochemical formation of viologen nano/microsized wires and tubes by potential sweep technique combined with micellar disruption method
6. MV polymer Bioelectrochemistry Volume 60, Issues 1-2, August 2003, Pages 57-64 Voltammetric and spectroelectrochemical characterization of a water-soluble viologen polymer and its application to electron-transfer mediator for enzyme-free regeneration of NADH