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1DOE Hydrogen, Fuel Cells and InfrastructureTechnologies Program Review 24 May 2004

Enabling Commercial PEM Fuel Cells WithBreakthrough Lifetime Improvements

Jayson W. BaumanE.I. du Pont de Nemours and Company, Inc.

2004 DOE Hydrogen, Fuel Cells andInfrastructure Technologies Program Review

24 May 2004

This presentation does not contain any proprietary or confidential information

©2004 E.I. du Pont de Nemours and Company, Inc.




Project Overview / Objectives

Road to SuccessRoad to Failure

IMPROVEMENTS

ME

A L

IFE

TIM

EBase

Polymer

Chemical

Stabilization

Membrane

Reinforcement

MEA and UEA

Design

“Ideal” PFSA

Standard PFSAH2O2

formationRadical formation

Attack of polymer weaksites

Material propertiesdegrade

Localized stresspromotes cracks,fissures

Crossover failureoccurs

Peroxideprevention

Peroxidedecomposition

Stabilize polymer

Membranereinforcement

Membrane reinforcement

Edge seal design andoptimization

Eliminate Fentoncontaminants

Through both experiments and modeling, we

have developed an understanding of potential

mechanisms than can lead to membrane

failure

Individually, each of these strategies

improves membrane durability. This

program will optimize each and incorporate

them, in toto, into fuel cell products.




Team--Interactions & Collaborations

DuPont Wilmington

Fayetteville

Towanda

Other Sites

UTRC

UTC FC

UTC USM

UConn

Laying the groundwork….

The core DuPont / UTC team has been jointly

investigating MEA durability improvement

techniques for over 3 years. Consequently, while

still in the first year of this program, we have

already demonstrated the feasibility of several

durability enhancement strategies.

Raw materials

Nafion® membranes

DuPont Fuel Cells MEAs

UTC Cell StackAssemblies

UTC Power Plants

This team encompasses all aspectsof the supply chain from rawmaterials to power plants. Ourtight integration allows quick,reliable validation of any durabilityenhancement strategies.




Approach

Process Map for a Given Potential Improvement (e.g. Mechanical Reinforcement)

BestProduct

Task 1. Materials Synthesis

Task 2. Accelerated Aging Tests

Task 3. Analysis and Modeling

Task 4. Stack Testing

Task 5. Materials Char. and Analysis

Task 6. Cost Analysis

MaterialsSynthesis

AcceleratedAging Tests

Analysis &Modeling

Mat. Char. &Analysis

BaselineProducts

ImprovedProducts




Approach

Chemically Strengthen

Mechanically Strengthen

GDL

Peroxide Mitigation

Seal Improvement

StackTesting DurableDurable

MEAMEABest of Each

Strategy

Down-Select

We are optimizing several proven durability

enhancements in parallel. At various down-

select points, we shall incorporate the best of

each mitigation strategy into fuel cell stacks

to validate improvements.




Budget Projections

0

200

400

600

800

1000

1200

MaterialsSynthesis

AcceleratedAging Tests

Analysis andModeling

Stack Testing Materials Charand Analysis

Cost Analysis ProgramManagement

$1000 p

er

An

nu

m

Year 1

Year 2

Year 3

FY 2004FY 2005FY 2006

Total

$Total

2905295829288792

$DOE

2324236723437033

5815925861758

$DuPont1000 $




Technical Barriers and Targets

• DOE Technical Barriers for Fuel Cell Components

• O. Stack Material and Manufacturing Cost

• P. Durability

• DOE Technical Target for Fuel Cell Stack System for2010

• Cost not greater than current Nafion® projections

• Durability > 40,000 hours (stationary), 5000 hours (auto)




• Working and living safely is pervasive throughout DuPont culture

• Consequently, all fabrication and testing is subject to a rigorous Safety,

Health, and Environment review before commencement of any work.

Any safety incidents are thoroughly investigated to capture learnings.

• Our safety record validates the effectiveness of our acute attention to

detail

Safety is a DuPont Core Competency

Total Reportable Incidents(per 100 employees)

0

1

2

3

4

5

6

DuPont Chemical Industry Industry Average

Lost Work Cases(per 100 employees)

0.0

0.5

1.0

1.5

DuPont Chemical Industry Industry Average

Source: U.S. Bureau of Labor Statistics,2002 Data--Injuries and Illnesses

H2 Detector

DuPont Fuel Cells has never had a hydrogen-related safety

incident. We attribute this to careful planning of both operating

procedures and facilities installation.

“Open Space”around test

stationplumbing

All fuel cell hardware contained withinventilated enclosure




Project Schedule

Materials Synthesis

Accelerated Aging Tests

Analysis and Modeling

Stack testing

Materials Characterization and Analysis

Cost Analysis

2003 2004 2005 2006

ProgramStart

10/01/03

ProgramEnd

9/29/06

DesignLock-In5/31/05

Today




Resistance to Peroxide Attack

We have demonstrated that polymer chain end-groups are susceptible to peroxy radicals

• Correlation exists between polymer degradation and number of polymer chain end groups

• Reduction of end-groups shown to improve chemical stability

Processing conditions reduce undesirable

end group count to non-detect quantities

Fenton’s Test proves that materials with

reduced undesirable end groups exhibit

increased resistance to chemical attack

GOAL: Design membrane that is completely resistant to chemical attack

0

5

10

15

20

NR111 Chem Stable NR111

mg

Flu

ori

de / g

ram

po

lym

er

0

20

40

60

80

100

120

Process A Process B

No

rma

lize

d E

nd

Gro

up

Co

un

t

As Made

After Stabilization




Increasing Mechanical Stability

Desirable Membrane Properties:

• Increased Tensile Strength (>100% improvement over current product NR111)• Isotropic Properties (tensile strength, tensile modulus, coefficient of moisture expansion)

We have made significant progress in membrane properties (mechanical strength and isotropy) through:• Process design• Material design

We are establishing correlation between these properties and durabilityWe will improve tensile strength by an additional 50% by 3Q’04We will optimize our materials to minimize CME below 5%.

Improvements in Tensile StrengthThrough Membrane Design

Improvements in Tensile StrengthThrough Process Conditions

A B C

Process

Ten

sile S

tren

gth

Machine Direction

Transverse Direction

Control

A B C D

Membrane Design

Te

ns

ile

Str

en

gth

Machine Direction

Transverse DirectionControl




Accelerated Test Validation

0

200

400

600

800

1000

1200

1400

1600

A B C D E F

Membrane

Av

era

ge

OC

V D

ec

ay

/ µ

V h

r-1

Accelerated chemical degradation Accelerated mechanical degradation

• MEA is held in situ at conditions known to be

conducive to H2O2 formation

• Effluent water is measured for fluoride ions

• As expected, strengthened membranes give

lower fluoride emission rates

• We have confirmed that OCV is indicator of

membrane integrity

• Test developed to reproducibly accelerate

membrane degradation

• As expected, strengthened membranes give

lower OCV decay rates

0

5000

10000

15000

20000

0 10 20 30 40 50 60

Time / hour

Cu

mu

lati

ve F

io

n e

mis

sio

n Control

Strengthened




Peroxide Mitigation Technology

UTC Peroxide Mitigation Design Strategy:

• Identify mechanisms of peroxide-engendered attack of the PEM membrane• Use physics-based modeling to design mechanism-based mitigation strategies

Progress:• Designed and optimized mitigation strategies using physics-based models• Qualified in accelerated tests (sub-scale) w/ fluoride emission rate (FER) / membrane leak current:

• Multiple 200 hr highly accelerated tests (>100x)• Attained 3000 hrs in ~25x accelerated tests with no membrane failure

UTC peroxide

mitigation

added

Baseline

membrane

100x acc test

>100x acc test

25x acc testND

In 25-100x accelerated tests, UTC mitigation strategies :- Reduced fluoride emission rates (FER) by 10-100x- to FER levels comparable to membrane lasting 16,000 hrs in non-accelerated tests

Relative fluoride emission rate




Mitigation Technology Optimization

0.000 0.050 0.100 0.150 0.200 0.250

Version 3

Version 2

Version 1

Fluoride Emission Rate (umol/cm2-hr)

Version 1

mitigation

Version 2

mitigation

Version 3

mitigation

Issue – Peroxide mitigation strategies have some impact on cost, performance

UTC Strategy:

• Identify improved mitigation structures to reduce impact on cost, performance• Use physics-based modeling to optimize these structures before testing

Progress:• Have experimentally demonstrated improved structures:

• Version 1 used in previous slide• Version 2 has 50% less impact on cost, performance• Version 3 has >50% impact on cost• Versions 2&3 actually better despite lower impacts on cost, performance

Future mitigation structures for 40,000 hr. life attainable with negligible cost & performance impact

Relative fluoride emission rate




Future Work

Chemically Strengthen

Mechanically Strengthen

GDL

Peroxide Mitigation

Seal Improvement

• Evaluate under long-term 10x accelerated conditions in full-size

parts and short stacks

• Continue structural improvements to lower cost, increase

performance

• Investigate other potential degradation mechanisms

• Study end group vs. membrane decomposition correlation

• Correlate ex situ test data to in situ test data

• Optimize chemically stabilized membrane

• Optimize composition and processing conditions

• Evaluate under both accelerated and real-time testing

conditions

• Continue durable GDL scouting

• Study affects of PTFE coating on macroporous layer durability

• Physics-based modeling for durability-based seal design

• Continue seal materials evaluation

enabling commercial pem fuel cells with breakthrough ...• version 1 used in previous slide •...

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