An Advance In Fuel Cell Technology Ryan Steed Future Directions in Chemistry Current Fuel Cells: Basics •Proton Exchange Membrane (PEM) Fuel Cell Current Fuel Cells: Fuel Reforming •Major sources of H2 for fuel cells are hydrocarbons •Endothermic ‘reforming’ of hydrocarbons C2O2H6 + 2H2O 5H2 + 2CO2 (+ CO) O2 Gas stream C2O2H6 PEM H2, CO, CO2 Cell CO2 H2O Electricity Current Fuel Cells: Fuel Reformation •CO bad for PEM fuel cells •CO reacted with steam at >500 K to complete oxidation O2 Gas stream C2O2H6 PEM H2, CO, CO2 H2, CO2 Cell CO2 H2O (g) @ 500K H2O Electricity Current Fuel Cells: Pros and Cons •Pros •More efficient than combustion of hydrocarbons •Relatively clean •Cons •High temperature requirement •CO poisoning •Expensive platinum requirement •CO poisoning is the major restriction in fuel cell development. New Technology •Use CO as an energy source •Polyoxometalate (POM) Fuel Cells O2 Gas stream C2O2H6 POM PEM H2, CO, CO2 Cell H2, CO2 Cell CO2 Electricity H2O Electricity Polyoxometalate H3PMo12O403- H3PMo12O405- reduction In aqueous solution The POM Fuel Cell System POM electricity recycled POMred POMox H2 H2, CO2 The POM Fuel Cell System Redox Exchange CO +H2O + POMox CO2 + POMred • 2H+ Anode POMred • 2H+ 2e- + 2H+ + POMox Cathode 2e- + 2H+ + O2 H2O requires Pt 2e- + 2H+ + POMox POMred • 2H+ no Pt Advantages of POM Fuel Cells •High temperature steam eliminated (also reduces size) •CO poisoning eliminated •Produce electricity directly from fuel (rather than carrying a high pressure H2 tank) •Reduced precious metal requirement Future of POM Fuel Cells •Optimization is required to increase power output •Decreased size, cost, and temperature make POM fuel cells more practical for portable applications. References PEM Fuel Cell Diagram. “Fuel Cell Basics: How they Work.” http://www.fuelcells.org/basics/how.html. Accessed 10/26/04. National Research Council. 2003. Beyond the Molecular Frontier. Washington, DC: National Academies Press. POM Fuel Cell Diagram. “Wisconsin Engineers Clear Bottleneck in Production of Hydrogen.” http://www.engr.wisc.edu/news/headlines/2004/Aug26.html. Accessed 10/26/04. Kim, B. W., T. Voitl, G. J. Rodriguez-Rivera, and J. A. Dumesic. 2004. “Powering Fuel Cells with CO via Aqueous Polyoxometalates and Gold Catalysts.” Science. 305: 1280. Nice, Karim. “How Fuel Cells Work.” HowStuffWorks.com. http://www.howstuffworks.com/fuel_cell.htm. Accessed 10/26/04. ---. “How Fuel Processors Work.” HowStuffWorks.com. http://www.howstuffworks.com/fuel_processor.htm. Accessed 10/26/04.
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