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2006 DOE Hydrogen Program Review
MEA & Stack Durability for PEM Fuel Cells
3M/DOE Cooperative Agreement No. DE-FC36-03GO13098
Project ID # FC8
3 Mike Hicks
3M Company May 16, 2006
This presentation does not contain any proprietary or
confidential information
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Overview
Timeline 9/1/2003 6/30/2007* 70% complete * Revised end date
subject to
DOE approval
Budget Total $10.1 M
DOE $8.08 M Contractor $2.02 M
Funding received in FY05: $2.43 M
Funding for FY06: $2.60 M
Barriers & Targets A. Durability: 40k hrs
Team Members Plug Power Case Western Reserve
University University of Miami
Consultant Iowa State University
MEA & Stack Durability for PEM Fuel Cells 2 3 Fuel Cell
Components
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Objectives Develop a pathway/technology for stationary PEM fuel
cell systems for enabling
DOEs 2010 objective of 40,000 hour system lifetime to be met
Goal: Develop an MEA with enhanced durability Manufacturable in
a high volume process Capable of meeting market required targets
for lifetime and cost Optimized for field ready systems 2000 hour
system demonstration
Focus to Date MEA characterization and diagnostics MEA component
development MEA degradation mechanisms MEA nonuniformity studies
Hydrogen peroxide model Defining system operating window MEA and
component accelerated tests MEA lifetime analysis
MEA & Stack Durability for PEM Fuel Cells 3 3 Fuel Cell
Components
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Approach To develop an MEA with enhanced durability .
Optimize MEAs and Components for Durability
Optimize System Operating Conditions to Minimize
Performance Decay
Utilize proprietary 3M Ionomer Improved stability over baseline
ionomer
Utilize ex-situ accelerated testing to age MEA components Relate
changes in component physical properties to changes in MEA
performance Focus component development strategy
Optimize stack and/or MEA structure based upon modeling and
experimentation
Utilize lifetime statistical methodology to predict MEA lifetime
under normal conditions from accelerated MEA test data
MEA & Stack Durability for PEM Fuel Cells 4 3 Fuel Cell
Components
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Accomplishments GDL Characterization
Developed new test equipment to measure capillary pressure in
GDLs Membrane
Completed investigation of reinforced membranes reinforcement
may not be necessary for membrane durability
Identified membrane failure mode and implemented solution to
mitigate it Ongoing monitoring of membrane properties in
accelerated tests
Membrane Degradation Mechanism Analyzed experimental and
literature data more than just end group degradation Utilized
ionomer model compounds to identify likely points of attack and
provide insight
into ionomer degradation mechanism Developed initial hydrogen
peroxide model to study peroxide in operating fuel cell
MEA Nonuniformity Studies Completed 121-channel segmented cell
and investigated the effects of flow rate, load
setting and GDL type; determined high gas stoichiometry yields
current uniformity Utilized theoretical 3D fuel cell model to
investigate effects of catalyst, membrane and
GDL nonuniformity; determined that electrode defects result in
highly, nonuniform current distribution
System Test Initiated Saratoga system test with a preliminary,
durable MEA design
MEA Lifetime Modeling Demonstrated that load profile affects MEA
durability Developed initial lifetime prediction model to estimate
MEA lifetime relative to DOEs 2010
stationary system goals Related initial fluoride ion to lifetime
method to increase sample throughput
MEA & Stack Durability for PEM Fuel Cells 5 3 Fuel Cell
Components
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GDL Characterization Capillary Pressure Background Solution
Measured GDL permeability in humid and Design your own
instrument
dry air CWRU has designed, machined and Humid air yields lower
gas permeability assembled the sample holders, load cell
Pores fill with water and strain sensor CWRU collaborated with
Porous Materials
Problem Inc, Ithaca, NY to fabricate the instrument Need
technique to characterize water PMI will integrate the syringe
pump, the
transport in GDL pores press and automation There are no
available instruments for
measuring capillary pressures for hydrophobic porous media
measuring Capillary Forces in hydrophobic GDLs
GDLs
Developed an instrument for
New method to characterize
MEA & Stack Durability for PEM Fuel Cells 6 3 Fuel Cell
Components
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Reinforced Membrane Activities Membrane Stress Model Evaluation
of Various Reinforcing Members
Highest Stress Lowest Stress
Lands
Channels
Hypothesis 0 20 40 60 80
100 120 140 160 180 200
0 5 10 15 20 25 30 35 40
Tear (MPa)
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conductivity than neat Nafion
with 3M Ionomer
- Need reinforcing member to carry stress to eliminate
mechanical failure or reduce mechanical failure rate
Desired Result stronger and higher
Lines 3M Cast Nafion Membrane Symbols Various reinforced
membranes
RH Cycle Test to Evaluate HypothesisTest Conditions: 80C Cycle
equally between 0 and 150% RH
MEA (electrode and GDL) made Time to failure with: (hours)
DuPont Nafion (NR-111)1 260 330 Ion Power Nafion (N111-IP)1 1330 +
Gore Primea1 400 470 3M Cast Nafion (1000 EW) 1200 +
Neat membrane most durable
props and durability predict
mechanical durability predict
mechanical durability Less shrinking does not correlate to
more mechanical durability
No relationship between mechanical
Tensile test does not
Tear resistance does not
What is the benefit of reinforcement? 1. Gittleman et al, Fall
AIChE Meeting, October 2005.
MEA & Stack Durability for PEM Fuel Cells 7 3 Fuel Cell
Components
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Mitigation of Membrane Edge Failure in Modules Problem In module
testing, observe infant
Active Area
Site of mortality of MEAs due to edge failure at edge the
membrane catalyst interface failure
Solution Developed edge protection component
for MEA
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40 No Failures
20
0
w/o Edge Protection w/ Edge Protection
failure mode
solution to significantly reduce infant mortality failure
rate
Identified MEA
Implemented a
MEA & Stack Durability for PEM Fuel Cells 8 3 Fuel Cell
Components
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3M Ionomer Membrane Properties vs Decay Membrane Aging
Procedure
Pre-condition w/
Received H+ Form Membrane H+ Form
H2SO4 (0.1M) Ion exchange w/ FeSO4 (0.1M) 70C, 1 hour Fe(II)
Form
70C, 1 hour
Degraded MembraneFe(II) Form
H2O2 (0.1M) 70C, ~ 35 hours H2SO4 (0.1M) Ion exchange w/
70C, 2 hours
Measure degraded membrane properties over time
As Received H+ Form Degraded Sample @ 125 hrs
132C
125C
131C
Mechanical
20 40 60 80 100 120 140 160 180 0.0
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Temperature [C]
experiments in progress
after 125 hrs
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120
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Temperature [C]
Thermal Gravimetric
Dynamic
Analysis
Aging
No change Analysis
MEA & Stack Durability for PEM Fuel Cells 9 3 Fuel Cell
Components
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Membrane Decay Mechanism Via Model Compounds 208th ECS Meeting,
Abstract 1195,
Non-zero intercept
mechanism(s)
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dConventional Wisdom: Los Angeles, CA, October 2005 H2O2
generated during fuel cell
operation HO or other radicals are
attacking species -COOH end group unzipping
primary route 0 0
Demands other degradation
[ -COOH] Investigate alternative degradation mechanism(s)
via
model compounds reactive sites
Utilize analytical capabilities Better isolation of effect from
different Age MCs via Fentons test or UV light (200 - 2400 nm @
100W)
MC1 MC2 MC3 O O O
F F2 F2 F F2 F2 F2 F2 F2 F2 F2HO C C O C C CF3 HO C C O C C C C
SO3H HO C C C C SO3H
CF3 CF3
MC4 MC7 MC8
F3C F2 C C6 OH F3C
F2 C O
F2 C
F2 C
F2 C SO3H F3C
F2 C O
F2 C
F C O
F2 C
F2 C SO3H
O CF3
MEA & Stack Durability for PEM Fuel Cells 10 3 Fuel Cell
Components
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MC3 > MC1 MC2 > MC4 > MC7 & MC8 MC3 MC1 MC2
Model Compounds Relative Degradation Rates
HO C
O
F2 F2 F2 > C F C O O
CF3
HO F2 F2 HO C F C O
CF3
O
F2 F2 F2 F2 C C C SO3H C C CF3 C C C C SO3H
MC4 MC7 MC8
O F2
O F2 F
C O
CF3
F2 F2F2 F2C OH
O
F2 F2 F2> C C C SO3HCF3C F3C C C C C SO3H F3C C>6
effect
products?
& MC2
hydrolysis
COOH containing MCs exhibit low stability Comparison of MC3
& MC4
Is it really a reactivity effect or solubility
Is there a change in reactivity hydrolysis
Hydrolysis observed (by NMR) for MC1
Need to evaluate MC7 & MC8 for
Identified MC1 & MC2 Reaction Products O O O
C C F3C
COH F3C CF2
MC3 Isomer Degradation6 7 11
O CF3O F F 1 3
HO CF2 CF2
CF2 4 CF 10 SO3H
2 SO3H HO CF SO3H HO
O CF3 F F 8 95
Same degradation rate Decarboxylation is rate determining
step
MEA & Stack Durability for PEM Fuel Cells 11 3 Fuel Cell
Components
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Membrane Decay Mechanism Hydrogen Peroxide Model Objective To
define simple model to study peroxide behavior in an MEA
Equations:
(CH O ) = Rate of production electrochemical +Chemical
recombination )d (dt 2 2+ Rate of consumption
+ electrochemical reductionIonomer degradation + catalytic
disproportionation
+ Transport through the electrode Diffusion +Convection )(
Peroxide to membrane
Peroxide Concentration Profile as f(L) O2 inlet No peroxide 0.75
V =
Z= Z= 0 1
Experiments to Determine Input Parameters 1. Rate of Peroxide
Production2. Rate of Peroxide Disproportionation
Model provides insight into hydrogen peroxide distribution in an
operating fuel cell and the degradation of ionomer by hydrogen
peroxide
Geometry Model Output
MEA & Stack Durability for PEM Fuel Cells 12 3 Fuel Cell
Components
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MEA Nonuniformity Studies Motivation - MEA Durability Is MEA
durability a function of current
distribution/uniformity?
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2.5
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0.0
Increasi urrentng avg. cV. Gurau, H. Liu and S. Kakac, A Two
Dimensional Non-Isothermal Mathematical Model for Proton Exchange
Membrane Fuel Cells, AIChE Journal, Vol. 44 (11), pp. 2410 2422,
1998
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Dimensionless Channel
Length
Approach Measure experimentally segmented cell Theoretical
modeling
MEA & Stack Durability for PEM Fuel Cells 13 3 Fuel Cell
Components
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Segmented Cell
Inlet
Outlet A B C D E F G H I J K
1 2 3 4 5 6 7 8 9 10 11
0 5 10 15 20 25
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Current (A)
100 sccm Air 200 sccm Air 500 sccm Air
1000 sccm Air
210 sccm O2
50 cm2, 121 segments
Validation of Cell Design
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95 Filled Symbols Sum of Individual Segments Hollow Symbols
Fuel Cell (Segments shorted together)
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Effect of Air Flow Rate on Current Distribution
O2 Utilization = 0.99 0.96 0.56 0.31
200 sccm100 sccm 500 sccm 1000 sccm0.00
0.04
0.08
0.12
0.16
0.20
0.24
Inlet Outlet MEA & Stack Durability for PEM Fuel Cells 14 3
Fuel Cell Components
at high stoichiometry for uniformity
load
Cell design validated Design fuel cell systems to operate
Recently completed 121 channel
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MEA & Stack Durability for PEM Fuel Cells 15 3 Fuel Cell
Components
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0.78590.68110.57630.47160.36680.26200.15720.0524
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CL -1/2
Hydrogen
Air
Collector Plate
Membrane
x
y
z
Cathode catalyst layerGas diffusion layer
Anode catalyst layer Gas diffusion layer
Collector Plate
Gas channel
Gas channel
MEA Nonuniformity StudiesVariables Investigated Ionic
Conductivity Catalyst Loading GDL Porosity Electrode Thickness
Membrane Thickness GDL Thickness
Electrode Thickness
Surface defects resulted in highly non-uniform current
distribution
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MEA & Stack Durability for PEM Fuel Cells 16 3 Fuel Cell
Components
Objective Investigate possible interaction between system design
and durable MEA design
0
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0 100 200 300 400 5000
0.2
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1
Stack DC voltage System Efficiency
Cell Ratio
Saratoga System Test First Durable MEA TestingS
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Run Hours No negative MEA System interaction Program approach
validated
System Restarts
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Statistical MEA Lifetime Predictions from Accelerated Test
Data
00
0.50.5
Solid Lines Dashed Lines
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Dotted Lines
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Time Time Time
MEA & Stack Durability for PEM Fuel Cells 17 3 Fuel Cell
Components
Model Assumes Class model load profiles
Accelerated Lifetime (Hrs)
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Decreasing Stress
Predicted Lifetime 70C 100% RH
ibution
.001
.003
.005
.01
.02
.03
.05
.1
.2
.3
.5
.7
.9 .98
10^01 10^02 10^03 10^04 10^05 10^06
Censored data No censored data
Baseline Components
.001
.003
.005
.01
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Comparison of MEA Designs
~ 4x New 3M PEM MEAs
Baseline MEAs
Weibull distribution Arrhenius for temp Humidity model for
RH
Lifetime probability distrReasonable predictive values No OCV
load cycle offers ~ 13X lifetime improvement New MEAs with 3M
ionomer ~ 4x more durable
200 1000
Accelerated Lifetime (Hrs)
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Fluoride Ion Mapping of Accelerated Test Data 1.0E+05
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Predicted Lifetime New 3M PEM MEAs 70C 100% RH Hollow symbols:
In-Progress
R2 = 0.77
R2 = 0.89
R2 = 0.83
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1.0E+04
0.00 0.01 0.10 1.00 10.00
Initial Fluoride Release (g/min)
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3M PEM MEAs under accelerated, near-OCV load cycle test
conditions
Time
Pathway towards ~ 20,000 hour MEA lifetime with
Means to increase sample throughput
Near-OCV Load Cycle
MEA & Stack Durability for PEM Fuel Cells 18 3 Fuel Cell
Components
0
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Future Work To the End of the Project MEA & Stack
Development & Testing
MEA Component optimization & integration 3M Saratoga stack
tests Plug Power Complete MEA evaluation in modules/single cells
Plug Power Select Final stack and MEA design and test Plug
Power/3M
MEA Degradation Studies Peroxide model CASE
Incorporate realistic kinetic and transport parameters Model
compounds CASE
Determine degradation kinetic constants MEA nonuniformity
studies 3M/Plug/University of Miami
Determine operating conditions/MEA designs that yield current
distribution uniformity
Post mortem analysis CASE/Plug Power Mechanical
properties-morphology relationship CASE
MEA Statistical Lifetime Predictions MEA lifetime modeling
3M/Plug Power
MEA & Stack Durability for PEM Fuel Cells 19 3 Fuel Cell
Components
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Project Summary Relevance:
Approach:
Progress:
Developing MEA and system technologies to meet DOEs year 2010
stationary durability objective of 40,000 hour system lifetime.
Providing insight to MEA degradation mechanisms.
Two phase approach (1) optimize MEAs and components for
durability and (2) optimize system operating conditions to minimize
performance decay.
Demonstrated pathway towards 20,000 hour MEA lifetime with 3M
PEM MEAs under accelerated near-OCV load cycle test conditions.
Initiated durable MEA-stack system tests.
DOE 2010 FY 05 FY 06 Goal (hrs)
Accelerated Lifetime Predictions (hrs) 16,000 > 20,000
40,000
Technology Transfer/Collaborations: Active partner with CWRU,
Plug Power and the University of Miami. Presented 9 presentations
and 2 papers on work related to this project in last 12 months.
Future Work: Complete studies on MEA degradation mechanism.
Select final MEA and stack design and test system for 2,000
hours.
MEA & Stack Durability for PEM Fuel Cells 20 3 Fuel Cell
Components
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Publications and Presentations M. Yandrasits, Mechanical
property measurements of PFSA membranes at elevated temperatures
and
humidities, 2nd International Conference on Polymer Batteries
and Fuel Cells, Las Vegas, NV, June 2005. D. Stevens, M. Hicks, G.
Haugen, J. Dahn, Ex situ and in situ stability studies of PEMFC
catalysts: Effect of
carbon type and humidification on degradation of the carbon, J.
Electrochem. Soc., 152 (12), A2309 (2005). D. Schiraldi and C.
Zhou, Chemical durability studies of PFSA polymers and model
compounds under mimic
fuel cell membrane conditions, 230th ACS Meeting, Washington,
D.C., August 2005. M. Hicks, D. Pierpont, P. Turner, T. Watschke,
M. Yandrasits, Component Accelerated Testing and MEA
Lifetime Modeling, 2005 Fuel Cell Testing Workshop, Vancouver,
BC, September 2005. J. Dahn, D. Stevens, A. Bonakdarpour, E.
Easton, M. Hicks, G. Haugen, R. Atanasoski, M. Debe,
Development
of Durable and High-Performance Electrocatalysts and
Electrocatalyst Support Material, 208th Meeting of The
Electrochemical Society, Los Angeles, CA, October 2005.
D. Pierpont, M. Hicks, P. Turner, T. Watschke, Accelerated
Testing and Lifetime Modeling for the Development of Durable Fuel
Cell MEAs, 208th Meeting of The Electrochemical Society, Los
Angeles, CA, October 2005 (presentation and paper).
M. Hicks, K. Kropp, A. Schmoeckel, R. Atanasoski, Current
Distribution Along a Quad-Serpentine Flow Field: GDL Evaluation,
208th Meeting of The Electrochemical Society, Los Angeles, CA,
October 2005 (presentation and paper).
G. Haugen, D. Stevens, M. Hicks, J. Dahn, Ex-situ and In-situ
Stability Studies of PEM Fuel Cell Catalysts: the effect of carbon
type and humidification on the degradation of carbon supported
catalysts, 2005 Fuel Cell Seminar, Palm Springs, CA, November
2005.
D. Pierpont, M. Hicks, P. Turner, T. Watschke, New Accelerated
Testing and Lifetime Modeling Methods Promise Development of more
Durable MEAs, 2005 Fuel Cell Seminar, Palm Springs, CA, November
2005.
M. Hicks, R. Atanasoski, 3M MEA Durability under Accelerated
Testing, 2005 Fuel Cell Durability, Washington, DC, December
2005.
Z. Qi, Q. Guo, B. Du, H. Tang, M. Ramani, C. Smith, Z. Zhou, E.
Jerabek, B. Pomeroy, J. Elter, "Fuel Cell Durability for Stationary
Applications - From Single Cells to Systems, 2005 Fuel Cell
Durability, Washington, DC, December 2005.
MEA & Stack Durability for PEM Fuel Cells 21 3 Fuel Cell
Components
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Response to 2005 Reviewers Comments Need to evaluate catalyst
degradation; how does catalyst degradation affect
overall MEA durability? Reported results of commercial Pt/C
catalyst durability and degradation at 2004
HFCIT Review Project not focused on development of Pt/C
catalyst; separate 3M/DOE project
focused on catalyst durability (3M NSTF catalyst) Need
additional characterization of membrane physical properties and
effect of
aging on these properties Initiated task on measuring membrane
mechanical properties & morphology as a
function of aging Need to relate effect of component
improvements to overall MEA improvements.
What component improvement added most value to MEA lifetime?
Integration of components is critical in terms of obtaining good
MEA durability Considering possible patent applications
Need to work on reinforced membranes. Have evaluated reinforced
membranes; results to be presented in the future Development out of
scope of project some work done at expense to 3M
Better description of lifetime model Using std lifetime
statistical analysis techniques; see W.Q. Meeker and L.A.
Escobar, Statistical Methods for Reliability Data, John Wiley
and Sons, Inc. (1998) Need to address other targets
(cost/performance) in concert with durability
Reported performance at the 2005 DOE Hydrogen Program Review
Cost not a primary objective; it is used as a metric when deciding
options
Too much emphasis on fluoride ion release. Disagree Very strong
relationship between fluoride release and MEA lifetime
MEA & Stack Durability for PEM Fuel Cells 22 3 Fuel Cell
Components
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Critical Assumptions and Issues Validation of lifetime model
analysis method
Testing baseline samples at normal test conditions Comparison to
field test data
Increasing sample throughput of improved durability MEAs New,
durable MEAs last too long Use initial fluoride ion release as
metric (reduces test time) Plug Power test equipment online (adds
more test equipment)
Understanding role of peroxide Initial peroxide lifetime model
established
Demonstrate benefit of new, more durable MEAs Start lifetime
accelerated tests of new MEAs Apply lifetime model to new MEAs
MEA & Stack Durability for PEM Fuel Cells 23 3 Fuel Cell
Components
MEA & Stack Durability for PEM Fuel
CellsOverviewObjectivesApproachAccomplishmentsGDL Characterization
Capillary PressureReinforced Membrane ActivitiesMitigation of
Membrane Edge Failure in Modules3M Ionomer Membrane Properties vs
DecayModel Compounds Relative Degradation RatesMEA Nonuniformity
StudiesSegmented CellMEA Nonuniformity StudiesVariablesSystem Test
First Durable MEAFluoride Ion Mapping of Accelerated Test
DataFuture Work To the End of the ProjectProject
SummaryPublications and PresentationsResponse to 2005 Reviewers
CommentsCritical Assumptions and Issues