E. Bryan Coughlin

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Honors 391D Section 6 Why is Renewable Energy
not a Reality Today
E. Bryan Coughlin Polymer Science and Engineering
UMass Amherst Coughlin_at_mail.pse.umass.edu Conte
A612 ext. 7-1616
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Todays Discussion Topics Why Isnt There a
Hydrogen Economy? and Will There Ever Be a
Hydrogen Economy?
August 24 Article on Physorg.com http//www.physor
g.com/news170326193.html
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A Global Challenge
Human development index vs. per capita
electricity use for selected countries. Taken
from S. Benka, Physics Today (April 2002), pg 39,
and adapted from A. Pasternak, Lawrence
Livermore National Laboratory rep. no.
UCRL-ID-140773.
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World Population Energy Demand and Supply
Energy is the single most important challenge
facing humanity today. Nobel Laureate Rick
Smalley, April 2004, Testimony to U.S. Senate
http//www.plasma.inpe.br/LAP_Portal/LAP_Site/Figu
res/Energy_Demand.gif www.iea.org
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Renewable Energy
World Coal Institute Reserve Estimates at
Todays Consumption Levels Coal 130
years Natural Gas 60 years Oil 42 years
Hydrogen Power
http//www.martinot.info/
http//www.nrel.gov/
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Types of Fuel Cells and their Application
Direct Methanol Fuel Cell Alkaline Fuel
Cell Molten Cabonate Fuel Cell Solid Oxide Fuel
Cell Phosphoric Acid Fuel Cell Proton Exchange
Membrane Fuel Cell
J. Larminie, A. Dicks, Fuel Cell Systems
Explained, Wiley, 2nd edition, 2003
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Fuel Cell Types
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Energy Devices
Lithium ion Battery
Ion conducting Polymer Electrolyte membrane is
needed
OH-
Kerr,J.B. Berkeley, ppt.
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Why fuel cells?

• Polymer electrolyte fuel cells (PEMFCs) can be
  used as highly efficient, non polluting power
  sources for vehicles and electronic devices.

PEMFCs Advantages Low operation
temperatures High power and energy
density Different fuel sources (commonly hydrogen
or methanol) may be employed Portable
energy Highly efficient energy conversion (35
for PEMFCs compared to 15 for internal
combustion engines)
For a review see Whittingham, M.S, Savinell,
R.F., Zawodzinski, T (editors), Chem. Rev., 2004,
104, 10.
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How do PEM Fuel Cells Work?
Electrons traveling from anode to cathode produce
an electrical current
Cathode Oxygen from air combines with H and e-
to form H2O
Anode Hydrogen is catalytically dissociated to
H and e-
Proton H
Conductive membrane Protons diffuse from the
anode to the cathode through a polymer
electrolyte membrane.
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How do PEM Fuel Cells Work?
Electrons traveling from anode to cathode produce
an electrical current
Cathode Oxygen from air combines with H and e-
to form H2O
Anode Hydrogen is catalytically dissociated to
H and e-
Proton H (H3O) (H3O)(H2O)3-5
Conductive membrane Protons diffuse from the
anode to the cathode through a polymer
electrolyte membrane.
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Image from Caterpillar.com

• High Temperature Operation Goals
• Improvement in catalyst efficiency
• Increased kinetics
• Improved CO tolerance
• 20 ppm at 80 ºC vs. 30,000 ppm at 200 ºC
• Simplification (Elimination) complex hydration
  systems
• Reduced fuel cell cost and operating cost

Reforming
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Proton Exchange Membrane Fuel Cells

• Proton Exchange.
• Membrane fuel cells (PEMFCs) can be used as
  highly efficient, non polluting power sources

• PEMFCs Advantages
• Low operation temperatures
• High power and energy density
• Different fuel sources (commonly hydrogen or
  methanol)
• Highly efficient energy conversion (40 for
  PEMFCs compared to 15 for internal combustion
  engines)

http//www.carlist.com/autonews/2004/toyota_fchv.h
tml
For a review see Whittingham, M.S, Savinell,
R.F., Zawodzinski, T (editors), Chem. Rev., 2004,
104, 10.
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State of the Art Membranes
Cluster Network Model (Gierke Model)
Nafion consists of a network of spherical water
clusters (inverted micelles) connected by
channels. Increase in temperature results in
more channel like character and increase in
conductivity.
Nafion The most widely used polymer electrolyte
for the manufacturing of fuel cells
Schmidt-Rohr Model

• Perfluorinated backbone provides mechanical
  stability
• Current standard against which other membranes
  are measured
• Proton conductivity up to 10-1 S/cm can be
  achieved.

Nafion consists of long parallel randomly packed
water channels surrounded by partially
hydrophilic side branches forming inverted
micelles.
Nafion can be used only in hydrated environment
due to vehicular mechanism of proton conduction
Gierke,T.D. et al.J.Poly.Sci.Poly.Phys.
1981,19,1687-1704 Gebel,
G., Polymer 2000, 41, 5829-5838
Schmidt-Rohr,K.
Chen,Q. Nature Materials,2008,7,75-83
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Grotthuss Mechanism
Vehicular Mechanism
Proton Conduction by transport of (H3O)(H2O)n
Nafion Most widely used Polymer for PEMFCs
(Proton Conduction by hopping)
As hydrogen bonded network tightens, proton
transfer barriers become
negligible.
Nafion consists of a network of spherical water
clusters (inverted micelles) connected by 1nm
dia. channels. Increase in temperature results
in more channel like character and increase in
conductivity.
Video Clip From Wikipedia
Schmidt-Rohr Model
Nafion consists of long parallel randomly packed
water channels surrounded by partially
hydrophilic side branches forming inverted
micelles.
Gierke,T.D. et al.J.Poly.Sci.Poly.Phys.
1981,19,1687-1704 Gebel, G., Polymer 2000, 41,
5829-5838
Schmidt-Rohr,K. Chen,Q. Nature Materials,2008,7,75
-83
van Grotthuss, C. J. D. Ann. Chim. 1806, 58, 54.
Kreuer, Chem. Mater. 1996, 8, 610-641 Schuster
and Meyer, Annu. Rev. Mater. Res., 2003, 33,
233-261
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DOE Targeted Research Areas
Critical Path Barriers

• Fuel cell cost
• Catalyst design
• Proton exchange membranes

• Hydrogen cost
• Solar hydrogen production
• Bio-inspired hydrogen production

• Hydrogen storage
• Novel materials
• Metal hydrides
• Carbon nanotubes

DOE Hydrogen Program Review
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(No Transcript)
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Toyotas Estimations
http//www.carlist.com/autonews/2004/toyota_fchv.h
tml
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Anhydrous Proton Conduction

• Advantages of High Temperature
• Membranes 120-200 C
• Improvement in catalyst efficiency
• Increased kinetics
• Eliminate complex water management systems
• Decrease size of thermal management system
• Reduce the fuel cell cost operating cost

Grotthuss Mechanism (Proton transport in
anhydrous environment)
Heterocycles such as imidazole benzimidazole,
possess properties similar to water
As hydrogen bonded network tightens, proton
transfer barriers become negligible.
Imidazole
Benzimidazole
Complex network of hydrogen bonds provides proton
transfer pathways
van Grotthuss, C. J. D. Ann. Chim. 1806, 58, 54.
Kreuer, Chem. Mater. 1996, 8, 610-641 Schuster
and Meyer, Annu. Rev. Mater. Res., 2003, 33,
233-261
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Heterocycles 1,2,3-triazole vs. imidazole
1,2,3-triazole
Imidazole
pka1 1.17, pKa2 9.26
More parasitic proton transfer occurs in
triazole than in imidazole
Woudenberg,R.C. Univ of Mass. 2007
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Conductivity of Polyvinyl Triazole
Tg PVT
38 PVT-6DMF
25 PVT-12DMF 18 Poly(vinyl imidazole
) 160
As solvent content ?,Tg ? Residual solvent can
increase s up to 4 orders of magnitude.

• A dramatic improvement in conductivity could be
  due to the reduced pKa and
• a lower number of conformational changes
  necessary for proton hopping.
• Triazole has a better electrochemical stability.

Zhou et al. J. Am. Chem.Soc. 2005, 127,
10824-10825. Zhou et al. J. Phys. Chem. A 2006,
110, 2322-2324. Subbaraman et al. J. Am. Chem.
Soc. 2007, 129, 2238-2239.
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Solid state MAS NMR Results
1H MAS NMR
The NH-NH contact is less than 3.5 Å.
13C CP MAS NMR
1H_at_ 30kHz (700 MHz)
a 15-17, b 66-70, c 15-17
S. Toppet,et al. J.Poly.Sci.Poly.Letters.Ed.1976,1
4,389
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1H DQ MAS NMR at different temperatures

• K
• (Tg 70K)

3o0 K
1H_at_30 KHz (700.1 MHz) Variable
Temperature 215 K 419 K
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Acknowledgement
UMASS MRSEC on Polymers
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Todays Discussion Topics Why Isnt There a
Hydrogen Economy? and Will There Ever Be a
Hydrogen Economy?
August 24 Article on Physorg.com http//www.physor
g.com/news170326193.html
26
Dual Mechanism
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Conductivity Measurements

• Conductivity obtained using AC electrochemical
  impedance spectroscopy

Voltage lags behind current by ?. Z is
frequency dependent
Z Z jZ
Z R Z 1/?C
l sample thickness A contact surface area
Polymer Electrolyte Reviews, Elsevier Applied
Science New York, 1987 pp 237-274.
http//www.gamry.com/App_Notes/EIS_Primer/EIS_Pri
mer.htm
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Energy Demand and Supply
Annual Global oil consumption and reserves
Lux research webinar http//www.plasma.inpe.br/LAP
_Portal/LAP_Site/Figures/Energy_Demand.gif
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Gasoline Vehicle
H2 Vehicle
3 Seconds After Ignition
60 Seconds After Ignition