2005 DOE Hydrogen Program Review
MEA & Stack Durability
for PEM Fuel Cells
3M/DOE Cooperative Agreement
No. DE-FC36-03GO13098
Project ID # FC12
3 Mike Hicks
3M Company May 24, 2005
This presentation does not contain any proprietary or confidential information
Overview
Timeline
• 9/1/2003 – 8/31/2006
• 40% complete
Budget
• Total $10.1 M
– DOE $8.08 M – Contractor $2.02 M
• FY04 – $1,650,000 from DOE (47% of FY04 PMP)
• FY05 – Projected $2,350,000 from DOE(88% of FY05 PMP)
Barriers & Targets
• A. Durability: 40k hrs • B. Cost: $400 - 750/kW
Partners
• Plug Power • Case Western Reserve
University Subcontract
• University of Miami Consultant
• Iowa State University
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
2 Components
Objectives
Develop a pathway/technology for stationary PEM fuel cell systems for enabling
DOE to meet its year 2010 objective of 40,000 hour system lifetime
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 • Degradation mechanisms • Defining system operating window • MEA and component accelerated tests • MEA lifetime analysis
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
3 Components
Approach To develop an MEA with enhanced durability ….
• 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
Optimize MEAs and Components for Durability
Optimize System Operating Conditions to Minimize
Performance Decay
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
4 Components
Accomplishments
• Component Characterization
• GDL permeability • Membrane properties vs decay • Segmented cell
• Model Compound Study – Membrane Decay Mechanism • Component Development
• Membrane (improved oxidative stability) • End group modified • Additive studies
• GDL (improved oxidative stability) • Stability factor
• Electrode design – Start-up, performance and fluoride release • System Study – CO and Air Bleed • MEA Accelerated Testing
• Effect of load settings • Relationship between fluoride release and MEA lifetime • Statistical analysis of accelerated test data • New MEAs with significant durability improvement
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
5 Components
GDL Permeability Measurements
• Measure GDL permeability under both humid and dry air
• Humid permeability lower than dry • Pores fill with water
• Humid conditions represent fuel cell conditions
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 100 200 300 400 500 600 700 800 900 1000
Current Density (A/cm2)
Cel
l Vol
tage
(V)
Control 0.8V 1.4V 2.0V 2.6V
Aging Procedure: • 0.5M H2SO4 • Age at X Volts for
10 minutes 70°C Cell 100% RH CF 800 H2 CF 1800 Air
0.0E+00
2.0E+05
4.0E+05
6.0E+05
8.0E+05
1.0E+06
1.2E+06
1.4E+06
1.6E+06
1.8E+06
0 0.05 0.1 0.15 0.2 0.25 Gas Velocity (m/s)
∆P/
leng
th (P
a/m
)
0.8V 1.4V 2.6V
Increasing Permeability
GDL Permeability – Dry Gas
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
3.0E+07
3.5E+07
4.0E+07
4.5E+07
5.0E+07
0 0.05 0.1 0.15 0.2 0.25 Gas Velocity (m/s)
∆P/
leng
th (P
a/m
)
GDL Permeability – Humid Gas 2.6V Aged GDL
Increasing Permeability
Performance of Aged GDLs
Dry Gas
Humid Gas
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
6 Components
Relationship Between Membrane Chemical
Degradation and Mechanical Failure
Peroxide Test Critical
John Nairn, Polymer Engineering and Science, 38 (1998) 186-193.
Mec
hani
cal P
rope
rty
Cel
l Vol
tage
Membrane Breach • 50ºC • 95% RHTime
• 1M H2O2threshold • 90ºC
value
Strength Test • Double notch tear test
Strength Loss as a Function of Peroxide Degradation
50
60
70
80
90
100
110
120
% O
rigin
al T
ear S
tren
gth A method of aging membrane
in a way that degrades mechanical properties is under development
Tear strength constant up toNo Fe(II) 25% membrane weight loss10 ppm Fe(II)
10 ppm Fe(II) - 2
0 10 20 30 40 Weight Loss (%)
3MEA & Stack Durability for PEM Fuel Cells –
DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
7 Components
Segmented Cell Outlet A B C D E F G H I J K 0.7
Inlet (11) 1
2
3
4
5
6
7
8
9
10
11 C
urre
nt D
ensi
ty @
0.5
V (A
/cm
2 )
0.65 10
9
8
0.6 7
6
0.55 5
4
30.5 2
Outlet (1)
0.45
Inlet 0.4 0 200 400 600 800 1000 1200 1400 1600 1800
Time (Secs)
• Printed circuit board technology • Divides 50cm2 active area into 121
segments which follow flow field
• Quad serpentine flow field • Inlet current 30% higher than outlet • 121 channel load under
development
MEA & Stack Durability for PEM Fuel Cells – 3
DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
8 Components
Model Compound (MC) Study – Membrane Decay MechanismMC1
MC2
MC3 MC4
MC5 MC6
MC7
MC8
C F C O
F2 C
F2 C CF3
O
CF3
HO
HO C F C O
F2 C
F2 C
F2 C
F2 C SO3H
CF3
O
F3C F2 C CF35
F3C F2 C
F2 C
F2 C SO3H F3C
F2 C
F2 C H6
F3C F2 C O
F2 C
F2 C
F2 C SO3H
F3C F2 C O
F2 C
F C O
F2 C
F2 C
CF3
SO3H
6HO C F2 C CF3
O
• –SO3H stable • –COOH unstable
• Ether linkages & tertiary C–F positions alpha to –COOH accelerate decay
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120 140 160 180 Time (hrs)
F - R
elea
sed/
Tota
l F- i
n M
C (
%)
MC1 MC2 MC4 MC5 MC6 MC7 MC8
Solution • 100mM MC • 400mM Fe2+ • 400mM H2O2 • 70ºC
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
9 Components
Stability of End Group Modified 3M Ionomer Accelerated Test Conditions: 90ºC cell 70ºC gas dew points H2/Air Anode over pressure Load Profile:
F2 C
F2 C
F2 C
F C
O F2 C
F2 C
F2 C
F2 C SO3H
x y COOHHOOC
End Group Modification • Eliminates –COOH groups
Statistically significant difference
• ANOVA => p=0.000 @ 90% confidence interval
Accelerated lifetime test • 89% improvement • 396hrs vs 210hrs
YN
700
600
500
400
300
200
100
0
Lifetime under accelerated conditions
Tim
e to
800
mV
OC
V (li
fetim
e)
End Group Modified
0
0.5
TimeI (A
/cm
2 )
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
10 Components
3M Membrane Stability – Ex-situ Tests
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
Ionomer Lot (w or w/o added Fe)
Mas
s Lo
ss D
urin
g So
ak T
est No Additive
Additive 1 Additive 2
3M Ionomer Lot 6 with no added Fe
3M Ionomer Lot 9 with 500ppm added
Fe
3M Ionomer Lot 6 with 500ppm added
Fe
Additives significantly mitigate membrane degradation via hydrogen peroxide
Procedure: • 1M H2O2 • 90°C • 5 days
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell Additive 1 – DOE Contract No. DE-FC04-02AL67621 11 Components
0.1
0.2
GDL Stability ImprovementsApplied Voltage = 1.4V vs. SHE
Log (Coulombs)
Stat
ic C
onta
ct A
ngle
543210-1-2-3-4
140
130
120
110
100
90
80
70
60
50
ID GDL 1 GDL 4
Scatterplot of Static Contact Angle vs Log (Coulombs) 0.9 0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
GDL 1
70°C Cell 100% RH CF 800 H2 CF 1800 Air
Time
Cel
l Vol
t ag e
(V)
0 200 400 600 800 1000 1200 1400 0.9
70°C Cell 100% RH CF 800 H2 CF 1800 Air
GDL 4
Time
0.8
0.7
0.6
0.5
0.4
0.3 Stability Factor (SF) = ƒ(GDL, Voltage)
Time to 50 C [GDL X, Volts]
=
Time to 50 C [GDL 1, Volts]
0
0 200 400 600 800 1000 1200 1400 Voltage (V) GDL 5 SFCurrent Density (A/cm2)
• Age at voltage for 1, 10,
New GDLs more stable
• GDL5 > 1500X improvement
2.0 87 100 or 1000 minutes 1.6 1549
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
12 Components
2.5 6Aging Procedure:
2.3 13• 0.5M H2SO4
1.2
Electrode Design – Start-up, Performance and Fluoride Release Test Conditions: 70°C Cell, 100% RH, 800/1800 sccm of H2/Air
0.3V 0.5V 0.6V 0.7V 0.8V
Electrode A
1.2
1 1
0.8 0.8
0.6 0.6
0.4 0.4
0.2 0.2
0.3V 0.5V 0.6V 0.7V 0.8V
Electrode C
Cur
rent
Den
sity
(A/c
m2 )
0 0 2 4 6 8 10
1.2
1
0.8
0.6
0.4
0.2
0
0.3V 0.5V 0.6V 0.7V 0.8V Electrode B
0 2 4 6 8 10
Time (hrs)
0 0 2 4
Electrode I (A/cm2) @ 0.6V 80°C, 100% RH, 260/850 sccm H2/Air F- Release (µg/day/cm2)
6
A B
8
C
10
0.571 0.535 0.563
0.10 ±0.02
0.17 ±0.02
0.16 ±0.02
Need to balance start-up, performance & fluoride release when selecting electrode design
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
13 Components
System Studies – CO/Air Bleed and Their Effect on F- Release
0
5
10
15
20
25
30
35
40
45
50
4 5 6 7 8 9 10 11 Air Bleed Level (% H2)
F - R
elea
se (n
g/hr
cm
2 )
0
10
20
30
40
50
60
70
80
90
100
Volta
ge D
ecay
( µV/
hr)
0
20
40
60
80
100
120
140
160
0 50 100 150 200 250 CO Concentration (ppm)
F - R
elea
se (n
g/cm
2 hr)
Total
Cathode
Anode
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.0 0.5 1.0 1.5 2.0 2.5 3.0 Air Bleed Level (v% of H2) for 10 ppm CO Reformate
Cel
l Vol
tage
- 10
ppm
CO
(V)
0.40
0.45
0.50
0.55
0.60
0.65
0.70 0 2.5 5 7.5 10 12.5 15
Air Bleed level (v% of H2) for 100 ppm CO Reformate
Cel
l Vol
tage
- 10
0ppm
CO
(V)
10 ppm CO 100 ppm CO
Typical Cell Performance vs Air Bleed
Fluoride Release & Voltage Decay vs Air Bleed
Fluoride Release vs CO Level
• Fluoride release increases with CO level
• Both anode and cathode • Performance and fluoride release
increase with air bleed • System design must account for
these competing factors
(Hol
low
Sym
bol) 100ppm CO
Total Cathode Anode
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
14 Components
Accelerated Testing: Effect of Load on Lifetime
Lo
ad (A
/cm
2 )
Load Profiles A0.5
0 0.5 B
0 C0.5
0 Time
Accelerated Test Conditions: 90ºC cell 70ºC gas dew points H2/Air Anode over pressure Same MEA construction
Average F-Lifetime Ion Release
Load Profile (hrs) (µg/min) A (14 samples) 260 +/- 110 2 +/- 1
B (4 samples) 1548 +/- 120 0.13 +/- 0.1 C > 2500 (2 samples) (ongoing) < 0.04
Load profile significantly affects lifetime • OCV setting results in a > 8X reduction in
MEA lifetime under accelerated conditions
• Systems should be designed to reduce total time spent at OCV
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
15 Components
100
1000
10000
Relationship Between F- Release & MEA Lifetime
Initial Fluoride Data Average Fluoride Data10000
y = 294.0x-0.45
R2 = 0.95 B C
A
y = 29.95x-0.42
R2 = 0.73
y = 285.4x-0.47
R2 = 0.95 B
A C
y = 27.99x-0.50
R2 = 0.74
Life
time
(hou
rs)
1000
100
1010
11 0.00 0.01 0.10 1.00 10.00 0.00 0.01 0.10 1.00 10.00
Fluoride Ion Release Rate (µg/min) Accelerated Test Conditions: H2/Air Anode over pressure Various membranes • Strong relationship between Load profile: fluoride release rate and MEA
lifetime • Relationship independent of
membrane type
Time
MEA & Stack Durability for PEM Fuel Cells – 3
0
0.5
I (A
/cm
2 )
DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
ComponentsA portion of the data from DOE Contract No. DE-FC04-02AL67621 16
Frac
tion
Faili
ng
Lifetime (hours)
.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 10^07
Analysis B Accelerated Conditions
Predicted Lifetime 70°C, 100%RH
.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 10^07
Accelerated Conditions Analysis A
Predicted Lifetime 70°C, 100%RH
.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 10^07
Analysis C Accelerated Conditions
Predicted Lifetime 70°C, 100%RH
Baseline MEAs - no newly developed components
• Predicted lifetime depends on analysis methodology
• Analysis C worst fit to data • Need to determine correct analysis
method by comparing predicted lifetime to real data
00
0.5 0.5 Load Profiles:
Solid Lines Dashed Lines
I (A
/cm
2 )
TimeTime
Statistical Analysis of Accelerated Test Data
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
17 Components
New 3M MEA Designs with Enhanced Lifetime
Accelerated Test: 90°C Cell, 60°C Dew Points, Anode Overpressure, H2/Air1.00 10
‘Knee’ EOL 0.95 OCV Metric
OC
V (V
)
0.90
0.85 MEA Design C 1 0.80
0.75
0.70 MEA Design A MEA Design B Initial Baseline 0.1 0.65 MEA F- Level 0.60
0.55 0.01
0.50 Baseline MEA
0.45 Lifetime
0.40 0.001
Fluo
ride
Rel
ease
( µg/
min
) (H
ollo
w S
ymbo
ls)
0 40 80 120
160
200
240
280
320
360
400
440
480
520
560
600
640
680
720
760
Load Profile: Time (hrs)
I (A
/cm
2 ) 0.5 Significant improvement in MEA lifetime • Design C 775% Improvement
0 • 700hrs vs 80hrs Time
MEA & Stack Durability for PEM Fuel Cells – 3
DOE Hydrogen Program Review May 23 - 26, 2005
MEA Design B – DOE Contract No. DE-FC04-02AL67621 18
Fuel Cell
Components
Response to 2004 Reviewers’ Comments
• Incorporate automotive conditions; define durability requirements for
automotive operation. – Accelerated stationary MEA tests are close to actual automotive operating
conditions – Accelerated component tests valid for both stationary and automotive
• No collaboration outside of team members. Program only valuable to 3M and Plug Power.
– “Critical mass” of collaboration established with CASE, Plug Power, and 3M as required in the solicitation
• Subcontract with University of Miami • Working with consultant from Iowa State University
– R&D addresses fundamental issues – Knowledge gained and successful demonstration of progress will benefit entire
fuel cell industry • Need MEAs and systems less sensitive to operating conditions.
– Only reported results with baseline materials and system in 2004 – New designs are still under development
• First system test w/new MEAs underway in 2005 • Catalyst support degradation critical barrier. How will it be solved?
– Not a critical barrier; commercially available catalysts address this issue MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
19 Components
Future Work
• Remainder of 2005
– Ongoing MEA component development – Pilot scale-up of new components
– MEA component integration – Ongoing accelerated MEA lifetime testing
– Initiate MEA accelerated testing with new components – Ongoing 3D model and segmented cell work – Ongoing studies on interactions between system
parameters and MEA durability – Start system testing using newly developed MEAs
• 2006 – Complete activities started in 2005 – Select MEA components for final system tests – Final system demonstration
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
20 Components
Publications and Presentations
• C. Zhou, T. Zawodzinski, Jr., D. Schiraldi, “Chemical changes in Nafion® membranes under
simulated fuel cell conditions,” 228th ACS Meeting, Philadelphia, PA, August 2004. • M.T. Hicks, “Accelerated testing – Application to fuel cells”, 2004 Fuel Cell Testing Workshop,
Vancouver BC, Canada, September 2004. • A. Agarwal, U. Landau and T. Zawodzinski, Jr., “Hydrogen peroxide formation during oxygen
reduction on high surface area Pt/C catalysts,” 206th ECS Meeting, Honolulu, HI, October 2004. (Presentation and Paper)
• C. Zhou, T. Zawodzinski, Jr., D. Schiraldi, “Chemical changes in Nafion® membranes under simulated fuel cell conditions,” 206th ECS Meeting, Honolulu, HI, October 2004.
• M. Pelsozy, J. Wainright and T. Zawodzinski Jr., “Peroxide production and detection in polymer films,” 206th ECS Meeting, Honolulu, HI, October 2004. (Presentation and Paper)
• J. Frisk, W. Boand, M. Hicks, M. Kurkowski, A. Schmoeckel, and R. Atanasoski, “How 3M developed a new GDL construction for improved oxidative stability,” 2004 Fuel Cell Seminar, San Antonio, TX, November 2004.
• D. Schiraldi, “Chemical durability studies of model compounds and Nafion® under mimic fuel cell conditions,” Advances in Materials for Proton Exchange Membrane Fuel Cells, Pacific Grove, CA, February 2005.
• S. Hamrock, ”New membranes for PEM fuel cells“, Advances in Materials for Proton Exchange Membrane Fuel Cells, Pacific Grove, CA, February 2005
• C. Zhou, T. Zawodzinski, Jr., D. Schiraldi, “Chemical durability studies of model compounds and Nafion® under mimic fuel cell conditions,” 229th ACS Meeting, San Diego, CA, March 2005.
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell “Nafion” is a registered trademark of DuPont 21 Components
Hydrogen Safety
The most significant hydrogen hazard associated
with this project is: ¾ Accidental H2 release in cylinder closet leading
to ignition from: • H2 line or manifold breach • Accident during replacement of tank cylinders
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
22 Components
Hydrogen Safety
Our approach to deal with this hazard is: ¾Design
• Hydrogen cylinder closet and gas distribution system adhere to codes. • Reduction in number of cylinders in the tank closet • 2-step regulators (less susceptible to failure and designed to fail
closed) • H2 sensors in all labs and tank closet, alarm system • Automatic shut-off of H2 gas supply if sensors detect H2 release
¾Procedures • SOP’s for tank changing, alarm responses, test station operation • Tank changing restricted to highly trained personnel • Regular maintenance checks – sensors, leak check of valves etc.
¾Installing H2 Generator (in non-inhabited mechanical room) to significantly reduce total volume of H2 in facility
MEA & Stack Durability for PEM Fuel Cells – 3 DOE Hydrogen Program Review May 23 - 26, 2005 Fuel Cell
23 Components
MEA & Stack Durability for PEM Fuel CellsOverviewObjectivesApproachAccomplishmentsGDL Permeability MeasurementsRelationship Between Membrane Chemical Degradation and Mechanical FailureSegmented CellModel Compound (MC) Study – Membrane Decay MechanismStability of End Group Modified 3M Ionomer3M Membrane Stability – Ex-situ TestsGDL Stability ImprovementsElectrode Design – Start-up, Performance and Fluoride ReleaseSystem Studies – CO/Air Bleed and Their Effect on F- ReleaseAccelerated Testing: Effect of Load on LifetimeRelationship Between F- Release & MEA LifetimeStatistical Analysis of Accelerated Test DataNew 3M MEA Designs with Enhanced LifetimeResponse to 2004 Reviewers’ CommentsFuture WorkPublications and PresentationsHydrogen Safety
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