POM Fuel Cells by HC12083117156

VIEWS: 52 PAGES: 12

									      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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