Biological Catalysis in the Future of Energy: Molecular Design for O-O Bond Breaking Films
Friday, December 13, 2013 – ( 2:00 pm to 3:00 pm )
Location: Babbio 219, Stevens Institute of Technology
Dr. Joshua Gallaway
The CUNY Energy Institute
It is generally recognized that large-scale energy storage is needed to achieve the societal-scale use of renewable energy. Next-generation, large-scale energy storage systems will need to be composed of low-cost, easily acquired materials, which will also be safe when used at scale. It is likely a portfolio approach will be adopted, incorporating batteries, supercapacitors, mechanical methods, and others. Storing energy as hydrogen is anticipated to be attractive, as hydrogen can also be used as a feedstock for liquid fuels. However, hydrogen production and conversion is often a cost-limiting process due to the price of precious metal catalysts such as platinum and palladium.
Compared to humankind, nature makes more efficient use of catalytic metals by incorporating individual metal atoms in enzymes. Enzymes can be used to build novel power sources that have no common analog, but this results in new engineering challenges. The transport of electrons from an electrified interface to an enzyme’s active site is one such problem. Enzymes are found in nature that accomplish all aspects of catalysis needed for hydrogen storage: formation and breaking of both H-H and O-O bonds. For example, the enzyme laccase is used by fungi to reduce oxygen in ambient air, breaking O-O bonds and electrochemically forming water.
In this talk I describe a hydrogel composite laccase electrode designed to catalyze oxygen reduction while simultaneously conducting electrons when in contact with a liquid electrolyte. The rates of the underlying transport and kinetic phenomena were characterized to identify the factors limiting the film’s maximum catalytic rate. This revealed that molecular changes to the hydrogel precursors used to cast the laccase electrode would result in doubled performance. This was confirmed experimentally, demonstrating that enzyme electrodes can be designed to operate at high rates.
Joshua Gallaway is a research scientist at the CUNY Energy Institute who specializes in the electrochemistry of advanced energy materials. His research focuses on energy storage to meet emerging societal needs such as electrical peak shaving, grid-scale load leveling, and stabilizing renewable sources such as wind and solar power. He received his PhD in chemical engineering from Columbia University in 2007. Working with his advisor Scott Calabrese Barton, he characterized the electron transfer rates of biological catalysts embedded in oxygen-reducing hydrogels. Using both experimental and modeling methods, this established that individual molecular structures in an electron transport series could be designed to maximize the current of the resulting electrode. After his PhD work he completed a postdoctoral appointment studying non-uniform current distributions in sub-micron interconnect features for the semiconductor industry. Building on this experience he then joined the newly-formed CUNY Energy Institute in a research position funded by the Wallis Foundation. Non-uniform current distributions are relevant in all electrochemical energy storage devices such as batteries and fuel cells. His recent research has focused on using high-flux synchrotron techniques to visualize these non-uniform reactions within large battery electrodes during cycling.