MEA and Stack Durability for PEM Fuel Cells

2005 DOE Hydrogen Program Review

MEA & Stack Durability for PEM Fuel Cells

3M/DOE Cooperative AgreementNo. DE-FC36-03GO13098

Project ID # FC12

3 Mike Hicks

3M Company May 24, 2005

This presentation does not contain any proprietary or confidential information

OverviewTimeline

• 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

ObjectivesDevelop 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


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


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


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


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 • 90ºCvalue

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) 1234567891011 C

urre

nt D

ensi

ty @

0.5

V (A

/cm

2 )

0.65 10

9

80.6

7

60.55 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


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 - Rel

ease

d/To

tal F

- in M

C (

%)

MC1 MC2 MC4 MC5 MC6 MC7 MC8

Solution • 100mM MC • 400mM Fe2+

• 400mM H2O2 • 70ºC


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 )


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


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


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 - Rel

ease

(ng/

hr c

m 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 - Rel

ease

(ng/

cm2 h

r) 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


14 Components

Accelerated Testing: Effect of Load on LifetimeLo

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


15 Components

100

1000

10000

Relationship Between F- Release & MEA LifetimeInitial 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 CellComponentsA 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


.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


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


17 Components

New 3M MEA Designs with Enhanced LifetimeAccelerated Test: 90°C Cell, 60°C Dew Points, Anode Overpressure, H2/Air

1.00 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, 2005MEA Design B – DOE Contract No. DE-FC04-02AL67621 18

Fuel CellComponents

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


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 SafetyThe 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


22 Components

Hydrogen SafetyOur 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


23 Components

MEA and Stack Durability for PEM Fuel Cells

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