Membranes and MEA's for Dry, Hot Operating ConditionsC. Performance Budget • Total Project funding $11.4 million - $8.9 million - DOE - $2.5 million - contractor cost share (22%)

Membranes and MEA's for Dry, Hot Operating Conditions

Steven Hamrock

May 19, 2009

FC_13_HamrockThis presentation does not contain any proprietary, confidential, or otherwise restricted information

3 Fuel Cell Components

2

Overview

Timeline• Project start 4/1/07• Project end 3/31/11• 50% complete

BarriersA. DurabilityC. Performance

Budget• Total Project funding $11.4 million

- $8.9 million - DOE- $2.5 million - contractor cost share

(22%)• Funding in FY 2008• $2.5 Million• Funding in FY 2009 • $2.5 Million

PartnersCase Western Reserve Univ.* Professors T. Zawodzinski and D. SchiraldiColorado School of Mines* Professor A. HerringUniv. of Detroit Mercy* Professor S. SchlickUniv. of Tennessee* Professor S. PaddisonGeneral Motors C. GittlemanBekktech Inc. T. Bekkedahl3M S. Hamrock (Project lead)

* denotes subcontractor

3

Project Objectives-Relevance• To develop a new proton exchange membrane with:

• higher proton conductivity• improved durabilityunder hotter and dryer conditions compared, to current membranes.

4

Project Approach• New polymers, fluoropolymers, non-fluorinated polymers and composite/hybrid systems

with increased proton conductivity and improved chemical and mechanical stability

• Developing new membrane additives for both increased conductivity and improved stability/durability under these dry conditions

• Experimental and theoretical studies of factors controlling proton transport both within the membrane and mechanisms of polymer degradation and membrane durability in an MEA

• New membrane fabrication methods for better mechanical properties and lower gas crossover.

• Focus on materials which can be made using processes which are scalable to commercial volumes using cost effective methods

• Testing performance and durability. Tests will be performed in conductivity cells, single fuel cells and short stacks using realistic automotive testing conditions and protocols.

• 2008/2009 Milestones

Q1 2008: 3M will develop new test methods and install and modify new equipment as appropriate. Screening of new materials will be underway.

Q3 2009: 3M will identify a first set of new, more conductive and durable materials.

5

Collaborations – Flow Of Samples And Information

Polymer Development3M, CWRU

Inorganic conductor/stabilizer developmentCSoM, 3M

Membrane Fabrication3M

Membrane Coating Process Development3M

Conductivity, Transport, Morphology Studies3M, CWRU, CSoM, UT

Fuel Cell Testing3M

Durability Testing3M

Ex Situ Stability TestsDetroit Mercy, 3M

Final MEA Fabrication3M

Stability ModelingUT

MEAs for Testing3M

Model Compound Stability Studies

CWRU

Performance and Durability Testing

3M

Short Stack Test

6

1.0E-03

1.0E-02

1.0E-01

1.0E+00

30 40 50 60 70 80 90 100Relative Humidity (%RH)

Con

duct

ivity

(S/c

m)

650 EW 700 EW825 EW 900 EW980 EW 1100 EW

Conductivity vs Relative Humidity @ 80CComparing to Nafion at 120C 230 kPa

1

10

100

1000

10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110%

Relative Humidity (%RH)

Con

duct

ivity

(mS/

cm)

3M 650EW (10-30-08) 120C

NRE-212 (3-20-07) 120C

Conductivity C alculatedbased on dry dimensions

and no swelling

Conductivity vs Relative Humidity @ 30C

1.0E-03

1.0E-02

1.0E-01

1.0E+00


Cond

uctiv

ity (S

/cm

)

650 EW 700 EW825 EW 900 EW 980 EW 1100 EW

• Conductivity vs. temperature for EW ionomers in 640 – 1100 EW range.

• The 2 lowest EW ionomers shown, 650 and 700 EW, meets DOE milestone for RT conductivity (ca. 80 mS/cm at 80%RH, 25C).

AC 4-point probe measurement.

Conductivity w/ Low EW

OCF2CF2CF2CF2

SO3H

(CF2CF)n(CF2CF2)m

3M Polymer

OCF2CF2CF2CF2

SO3H

(CF2CF)n(CF2CF2)m

3M Polymer

OCF2CF2CF2CF2

SO3H

(CF2CF)n(CF2CF2)m

OCF2CF2CF2CF2

SO3H

(CF2CF)n(CF2CF2)m

3M Polymer

Tim Bekkedahl - Bekktech

Low EW PFSA’s

• The 650 EW almost meets the 120ºC interim milestone (ca. 93 mS/cm at 120ºC, 50%RH)

7

1.0E-03

1.0E-02

1.0E-01

1.0E+00

20 30 40 50 60 70 80 90 100Relative Humidity (%RH)

Con

duct

ivity

(S/c

m)

3M PFSA, 800 EW

3M PFSA, 650 EW

3M PFSA, 580 EW

80ºC

Going To Even Lower Ew’s (<600) Can Provide Conductivity That Meets The DOE 2010/2015

Conductivity Targets At 80ºC• EW’s below about

600 will meet conductivity requirements at 80ºC, even at 40% RH.

• The conductivities at these very low EW’s are slightly higher than expected.

Low EW PFSA’s

Target %RH

8

Transport Pathways• Probed by NMR Diffusion and

Relaxation Studies• Plot shows Diffusion Coefficient vs.

Water Content for two samples• D levels off at low water content;

significantly higher for 700 EW than for other PFSA samples to date

Low EW PFSA’s

Lambda at 80C

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100

Relative Humidity (%RH)

Lam

bda

(mol

es w

ater

/ m

oles

aci

d) 3M 700 EW3M 825 EW3M 900 EW3M 980 EW3M 1100 EWNafion 112 In the range from 700 to 1100 EW,

these polymers show similar water absorption at 80ºC.

Tortuosity or Intrinsic Interactions?

Diffusivity vs Activity chart

1.00E-07

1.00E-06

1.00E-05

1.00E-04

0 0.2 0.4 0.6 0.8 1Ac tivity (LiCl+H2O)

Dif

fusi

on C

oeff

icie

nt [

cm2/

s

EW 825

EW 700

9

• Lower EW ionomer have higher conductivity than CF3CF2CF2CF2SO3H (300 MW/EW) at a given lambda value, showing the importance of the phase separated morphology.

In- Plane Conductivity At 80ºC• At lower % RH or λ, the conductivity increases by a much larger factor when the EW is

lower compared to the more humidified state.• This is consistent with the hydrated acid groups being more accessible to one another in

the lower EW ionomer, allowing proton transport even with little or no “free” water.

Low EW PFSA’s

0.001

0.01

0.1

1

200 300 400 500 600 700 800 900 1000 1100 1200EW

S/cm

λ = 14λ = 9λ = 5λ = 3λ = 2

Perfluorobutanesulfonic acid

λ = 9

λ = 5

λ = 3

λ = 2

Large Increase 16.6 X

Small Increase 3.6 X

10

Wide Angle X-Ray Scattering• Crystalinity from TFE in the polymer backbone is important for good mechanical properties and low water solubility

• WAXS shows little crystalinity below about 800 EW

The Bad News - Loss of CrystalinityLow EW PFSA’s

11

More Bad News - Loss of Crystalinity

• Solubility is determined by boiling, filtering an aliquot of filtrate, and determining fraction of membrane “dissolved”.

• Solubility starts near where crystalinity is gone.

• Many mechanical properties parallel this effect

Understanding “true” solubility helps defining possible mechanical stabilization methods

Low EW PFSA’s

Membrane Solubility*

0

10

20

30

40

50

60

70

80

90

100

400 500 600 700 800 900 1000 1100 1200

Eq, Wt (g/mol)

% D

isso

lved Water Solubility

* Can vary w ith process conditions

Range where crystallinity index goes to zero

12

02468

101214161820

0 5000 10000 15000 20000

RH Cycles

Cros

s-ov

er (s

ccm

) .

730 EW730 EW3M Cast Nafion™ 10003M Cast Nafion™ 1000825 EW Process 1825 EW Process 1825 EW Process 1825 EW Process 2825 EW Process 3

RH CyclingLow EW ionomers do poorly in humidity cycle testing.Performance of 825 EW depends on membrane processing conditions.

Craig Gittleman - GM

Low EW PFSA’s

13

So, we can make low EW that can give great conductivity, but mechanical properties and

durability can be compromised.Some possible solutions:

blends crosslinking

reinforcementpolymer modifications

We are looking at all of these

Low EW PFSA’s

14

Blends of Water Soluble and Insoluble Ionomers

• In miscible blends of soluble and insoluble ionomers there is little to no evidence of the insoluble ionomer captivating the soluble ionomer.

• We are still evaluating blends with not-so-low EW ionomers and high EW ionomers or non-ionic polymers.

Low EW PFSA’s

583 and 1000EW blends

0

20

40

60

80

100

120

0 20 40 60 80 100 120Fraction of 583 EW polymer

% w

ater

sol

uble

15

Polymer Modification – one approach

• Bis-sulfonyl imides are very chemically stable and highly acetic.

• Aromatic R groups can be substituted with additional functionality for stable cross-linking and/or adding additional acid groups including HPA’s.

Imide sidechains

16

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

O

OO

H

• Changing the nature of the acid group

Sulfonic acid• Lowest EW limited by monomer MW

Imide sidechains

17

SF3CO

O

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

N

OO

H


Perfluoro imides • Similar polymers prepared at Clemson via

polymerization of imide monomers with TFE*• Stronger acids than sulfonic acids

* Creager, S.E et.al., Electrochem. and Solid State Lett. 2(9) 434-436 (1999)

Imide sidechains

18

SO

O

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

N

OO

H


Aromatic imides • Useful synthetic handle• Similar pKa to sulfonic acids• Very hydrolytically stable in aqueous acid at

elevated temperatures

Our interest is using this as a synthetic handle for attachment of

additional protogenic groups, cross-links, etc.

Imide sidechains

19

ClSO2

Polymer-SO2HN2 Polymer-SO2HNSO2

(sulfonamide)

Sulfonic acid

• 19F NMR of CF2group next to sulfur allows following the reaction

• This is a “poor” sample to show peak separation

Imide sidechains

20

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00


Con

duct

ivity

(S/c

m)

Sulfonic acid, 800 EWSulfonic Acid 650 EWTrifluoromethyl imide,808 EWSPES 770 EWPhenyl imide, 802 EW

• Conversion of a 650 EW sulfonyl fluoride to the trifluoromethyl imide provided a 808 EW ionomer. The conductivity remained the same (stronger acid but higher EW) as the sulfonic acid

• Conversion of the same sulfonyl fluoride to the an 802 EW phenyl imide resulted in lower conductivity at lower %RH.

New Protogenic Groups

80ºC

Imide sidechains

21

SO

O

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

N

OO

HHO3S


Aromatic imides • Multiple acid groups• Two examples have been prepared

Imide sidechains

22

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

20 30 40 50 60 70 80 90 100Relative Humidity (%RH)

Con

duct

ivity

(S/c

m)

3M PFSA, 800 EW3M PFSA, 650 EWOrtho Bis Acid, 550 EWMeta Bis Acid 550 EWPhenyl imide, 802 EWSPES 770 EWBPSH 100 (EW 280)

• Multiple acid groups allow raising the conductivity of starting ionomer• 800 EW starting PFSA precursor with crystalline backbone can be used to make

low EW ionomer with higher conductivity.• These swell much less in liquid water than the PFSA’s with the same EW

Multiple Acid Groups On A Single Side-chain

CF2CF2

CF2

O

CF2

CF2CF2

CF2

n

n

SN

S

OO

OO

HSO3H

CF2CF2

CF2

O

CF2

CF2CF2

CF2

n

n

SN

S

OO

OO

H

SO3H

Ortho bis acid

Meta bis acid

80ºC

Imide sidechains

23

Imide sidechains

Thermal Gravimetric Analysis

• As is the case with di-sulfonated aromatics, the ortho substitution is less thermally stable than the meta.

• Neutralized samples have much better stability.

Ortho bis acid

Meta bis acid

24

SO

O

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

N

OO

H

HO3S

HO3S

Future Work - Other Polymers Are Being Prepared And Evaluated For:•Adding higher levels of acid groups, sulfonic or inorganic (HPA)•Impact of imide on morphology•Cross-linking through multi imide groups, backbone or Zr phosphonate linkages

SO

O

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

N

OO

H

H2O3P

CF2

CFCF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S OO

X

R

R= OH or imide

SO

O

O2S

CF2

CF2

CF2

CF

O

F2C

CF2

F2C

CF2

S

N

OO

H

NHO2S

Polymer

Attach sulfonated oligomers and/or polymers

Imide sidechains

25

Phenylphosphonate Attached to SiW11 KegginAromatic phosphonates attach to lacunary HPA’s, potentiality allowing immobilization. Membranes must be stable to liquid water!

Imide sidechains

8.2 8.0 7.8 7.6 7.4 PPM

Phenyl phosphonate in DMSO

Modified Keggin in DMSO

Modified keggin in DMSO spiked with phenyl phosphonate

Linewidth differences indicative of slower rotating species (attached to keggin)

PO3H2

+2PO3H2

+2

HPA’s can increase proton conductivity and oxidative stability (AMR 2008)

26

Equilibrated morphologies: PFSA Chemistry

(PTFE in red,

–CF2SO3 – green

and water in blue)

D. Wu, S.J. Paddison, and J.A. Elliott, Energy and Environmental Science 1 284-293 (2008).

(Water density)

Simulation Box

(32 nm)3

• These mesoscale DPD simulations are able to capture differences in the hydrated morphology as both EW and monomer chemistry is changed.

• At the same EW and water content, the water domains in the 3M ionomer are larger and to some extent less connected than in the SSC ionomer.

Polymer morphology

λ = 16

27

Increasing EWD

ryB

oile

d

733 EW 825 EW 900 EW 1082 EW

Representative Morphologies from analysis of SAXS data

SAXS analysis shows structure which appears similar to mesoscale DPD simulations

Polymer morphology

28EW = 678, λ = 15

Water contour plots from simulations - Effects of the protogenic group on hydrated morphology

3M PFSA 3M PFSulfonylImideEW = 450, λ = 7.5

• Initail simulations have been done on the Ortho-bis acid with an EW of 450 and 600.

• Mesoscale DPD modeling suggest that polymer with an imide sidechain bearing 2 acidic protons may have a quite different structure

Polymer morphology

CF2CF2

CF2CF2

O

F2C

CF2

F2C

CF2

SO O

OH

CF2CF2

CF2CF2

O

F2C

CF2

F2C

CF2

SO O

NHS

O

O

SO3H

29

ESR: Competition Reactions for HO• in the Presence of DMPO as the Spin Trap

HO• + DMPO → DMPO/OH

HO• + A → A• (A is membrane or Ce(III), A• is membrane-derived fragment or Ce(IV))

][][1

DMPOkaka

vV

DMPO

=−

V and v are reaction rates for the formation of the DMPO/OH adduct in the absence and in the presence of the competitor A. Plot of vs gives the ratio , and a measure of the ability of the competitor to be attacked by hydroxyl radicals.

1−vV

][][

DMPOa

DMPOkka

kDMPO

ka

The formalism of “parallel reactions” leads to the expression:

Polymer Stability

30

Competition by Perfluorinated Membranes

Inhibition of DMPO/OH formation by the different membrane concentrations (0-10%) in Nafion® (A) and 3M membrane (B). [DMPO]= 9·10-

5 M, [H2O2]=9·10-3 M. Downward red arrow on the left shows the ESR signal that was monitored as a function of irradiation time. The black line on the right is for the formation of the DMPO/OH adduct in the absence of membranes.

3380 3400 3420 3440 3460

Magnetic Field / G

0%

2.5%

5%

7.5%

10%

0 5 10 15 20 25 300,0

0,2

0,4

0,6

0,8

1,0

Rel

ativ

e In

tens

ity o

f DM

PO

/OH

/ au

UV-Irradiation Time / s

3M/H2O2/DMPO/UV(B)

0%

2.5-10 %

0 5 10 15 20 25 300,0

0,2

0,4

0,6

0,8

1,0

Rel

ativ

e In

tens

ity o

f DM

PO

/OH

/ au


Nafion/H2O2/DMPO/UV(A)

0%

2.5%5%

7.5%

10%

3380 3400 3420 3440 3460

Magnetic Field / G

0%

2.5%

5%

7.5%

10%

Polymer Stability

31

Reaction Rates of Nafion®, Stabilized Nafion® and 3M

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0

1.2

(V/v

)-1

[SO-3]/[DMPO]

Nafion

Stabilized Nafion

3M

Slope ka•10-9 M-1s-1

Nafion® 1.124 4.0

Stab Nafion®

0.678 2.4

3M 0.034 0.17

ka (3M) / ka (Nafion®) ≈ 0.04

ka (S-Nafion®) / ka (Nafion®) ≈ 0.6

3M membranes appear more stable to attack by hydroxyl radicals compared to Nafion® and to stabilized (end group modified) Nafion®. We do not see such a large difference in longer term Fentons tests or fuel cell testing.

Polymer Stability

32

Ce(III) as Competitor

0 10 20 30 40 50 600.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

/ a.

u.


No Ce(III)

1.2 mM

0.24 mM

0.48 mM

0.72 mM

0.96 mM

(A)

0 2 4 6 8 10 12 140.0

0.5

1.0

1.5

2.0

2.5

3.0

(V/v

) -1

[Ce(III)]/[DMPO]

Slope = 0.17

(B)

(A) Effect of Ce(III) addition on the formation of the DMPO/OH adduct in solutions (pH=5.3) containing the indicated Ce(III) concentrations. (B) Inhibition of DMPO/OH formation by addition of Ce(III). Slope = kce/kDMPO = 0.17, kDMPO = 3.6·109 M-1s-1

(deduced in competition kinetics with methanol as the competitor for hydroxyl radicals) and kCe = 6·108 M-1s-1. This value can be compared with kCe = 3·108 M-1s-1 quoted in Coms, F.D.; Liu, Han; Owejan, J.E. ECS Transactions 2008, 16, 1735-1747.

Polymer Stability

33

n

MC1 MC2

MC3

MC4 MC5

MC6

MC7 MC8

MC5‐S

Model Compounds and Degradation Test Conditions

100mM MC + Solvent + 100mM H2O2 : exposed to UV light for 1hr

100mM MC + Solvent + 11mM H2O2 + 1.25mM Fe(II) : Fenton’s degradation test

Technique: Liquid chromatography-Mass spectrometry (LC-MS)Biphenyl ColumnNegative-ion electrospray ionization MS

Polymer Stability

34

UV/Peroxide and Fenton’s Degradation Products of AMCs

AMC1

HO OHAMC4

AMC5‐S

AMC7

AMC8

AMC Structures Degradation Products

Polymer Stability

• Aromatic compounds do degrade in the presence of peroxides.

• Major products mono- or di-hydroxylated AMCs.

• No aromatic-ring breaking observed. • AMCs containing more that one

sulfonic acid groups may show loss of one of the sulfonic acid groups.

• No biphenyl link breaking observed in AMC4 ; extensive hydroxylation and dimerization observed.

• Ether link breaking observed in AMC5.

Progress on Aromatic Model Compounds Study

35

Electrode Resistance and Performance

• Lower EW membranes provide better Fuel cell performance under hotter, drier conditions.

• Not all due to Ohmic losses.• Our screening electrode resistance, as

determined by transmission line measurements (TLM), is the dominant resistance. TLM method yields membrane resistances consistent with conductivity values.

Fuel cell testingPerformance

0

10

20

30

40

50

60

70

80

90

100

95 100 105 110 115 120 125

Cell Temperature (C)

Res

ista

nce

(mO

hm-c

m2)

Electrode 10um 733ew PEM15um 733ew PEM25um 733ew PEM

H2Air CS2/2x/8080oCCounterflowAmbient Pressure

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0

50

100

150

70 80 90 100 110 120 130

700 ew 1.0mil

800 ew 1.0mil

900 ew 1.2mil

1000 ew 1.2mil

1100 ew 1.2mil

RH %

Volta

ge (V

olts

)

@ 0

.5 A

mps

/cm

2 Outlet G

as RH

%

Cell Temperature (oC)

H2/Air CS 2.0

80oC DewpointsAmbient Pressure OutletsCounterflow

0.45

0.5

0.55

0.6

0.65

0.7

0.75

70 80 90 100 110 120 130

700ew 1.0mil800 ew 1.0mil900 ew 1.2mil1000 ew 1.2mil1100 ew 1.2mil

IR F

ree

Volta

ge (v

olts

)

@ 0

.5 a

mps

/cm

2

Cell Temperature (oC)

H2/Air CS 2.0

80oC DewpointsAmbient Pressure OutletsCounterflow

36

Oxidative Stability Gains

OCV, H2/Air, 95C, 7 PSIG, 50% RH

OCV, H2/O2, 90C, 0 PSIG, 30% RH

Fuel cell testingDurability

• Stabilizing additives can have a large effect on MEA lifetimes and fluoride release rates

• We continue to evaluate peroxide mitigation additives. Studies are ongoing to look at the effect of the location of the additive in the MEA.

• In addition, other variables have shown dramatic influences on FRR such as:

– Different PEM constructs.– Electrode effects.

37

Humidity Cycle Lifetime Durability Testing

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 2000 4000 6000 8000 10000 12000Time (hours)

Volta

ge

825 EW - 20 Micron, 0.4/0.4 Disp. Cat., New additive

825 EW - 0.2/0.2 NSTF w/ 20 micron mechanically stabilized membrane

825 30 Micron, 0.4/0.4 Disp. Cat., 3M stablizing addtive

3M Cast Nafion 1000, 0.4/0.4 Disp. Cat.

• New additive package provides over 10,000 lifetime in automotive accelerated durability protocol

From AMR 2006

Fuel Cell Durability Testing

New Data

Test Point

J (A/cm

2)

Duration (m

in)

Stoich.

1 0.20 5 5

2 0.02 20 15

3 0.80 15 1.7

4 0.80 10 3

5 0.02 20 15

6 0.80 15 1.7

7 0.20 20 5

8 1.00 20 1.7

From AMR 2008(ran to >8,000 hours)

Cast Nafion® Control

Cell Temperature: 80 oCInlet Dew points: 64/64 oCOutlet Pressures: 175kPa

End of life = < 800 mV OCV w/ 7 PSIG anode overpressure.


38

New Durability ProtocolCycles/Day Cell Temp Conditions Description Time

1 80 Long scan @ 0.6A/cm2 to used collect fluoride data 4.5 hrs

1 80 Short anode overpressure OCV to monitor lifetime 5 min

4120 Hot Temperature Low RH to degrade MEA (up to 80ºC dewpoint)

15 hrs30 Low Temperature to Thermal and Humidity Cycle MEA

2 80 Load Cycle at Various RH to monitor performance 4.5 hrs

Our old protocol was getting too long as material stability improved. New protocol with higher temp conditions (up to 120ºC) shows MEA lifetimes of about 1,000 to 2000 h for MEA’s which have lifetimes >5,000 h. in old test (3-5 X faster).

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800 1000 1200 1400 1600 1800

Time (hours)

Volta

ge

0.00

0.20

0.40

0.60

0.80

1.00

1.20

Fluo

ride

Ion

Rele

ase

(ug/

dayc

m2)

GREEN COLORS STILL RUNNING

Data To Be Measured


39

Future Work• Continue preparation and evaluation of the conductivity and durability of low EW

PFSA’s, new imide containing polymers (Slide 15-24), cross-linked polymers (Slide 24) and membrane additives (Slide 25,36,37).

• Evaluate membranes crosslinked in both the hydrophilic and hydrophobic regions (Slide 24).

• Evaluate additional polymer blends for ionomer stabilization (Slide 14)• Continue to probe factors in transport using NMR relaxation and diffusion, SAXS,

conductivity and other spectroscopic measurements. Continue to develop a better understanding of effect of low lambda on proton transport (Slides 6-9, 20, 22, 26-28).

• Undertake first principles modeling of crystallinity through a comparison of different ionomers (Slides 26,28).

• Develop a better understanding of role of crystalinity on swelling in new polymers using X-ray scattering, mechanical properties testing and modeling (Slides 10-12, 26-28).

• Evaluate impact of new protogenic groups and additives on membrane oxidative and chemical stability using ESR, ex-situ tests and fuel cell tests (Slides 29-34,36-38).

• Investigate the structural basis for the higher stability of 3M membranes compared to Nafion® in ESR experiments. Better understand what this is telling us about membrane stability in a fuel cell (Slides 29-31).

• Evaluate additional stabilizers for perfluorinated membranes (Slides 29-31, 36-37).• Describe degradation pathways and rates for current group of model compounds and

correlate with membrane stability (Slides 33-34).• Design MEA’s for larger scale testing (Slide 35).

40

Summary3M

2009 Status 2010 target 2015 target

Conductivity at 120º C S/cm

0.146 (46%RH)

580 EW PFSA 0.1 0.1


0.1 (40% RH)0.13 (50%RH) 0.50 (92%RH)580 EW PFSA 0.1 0.1


0.1 (80% RH)580 EW PFSA 0.07 0.07

Conductivity at -20º C S/cm

0.014 S/cm700 EW PFSA 0.01 0.01

O2 cross-over mA/cm2

<0.520 micron 2 2

H2 cross-over mA/cm2

<220 micron 2 2

Durability w/ cycling hours

10,000 (80ºC) 1000 (120ºC)

825 EW PFSA5000 (80ºC) 2000 (120ºC)

5000 (80ºC) 5000 (120ºC)

• This project involves using experiment and theory to develop an understanding of factors controlling proton transport and the chemical/physical durability of the membranes.

• New materials are being synthesized based on this understanding, and evaluation of these materials will further our understanding.

• This “feedback loop” will ultimately allow for materials “designed” to meet performance and durability targets.

• Several approaches or pathways to improving membranes are being investigated. We expect the final membrane will have attributes resulting from some or all of these. We will not “down select” just one approach.

Documents

Membranes and MEA's for Dry, Hot Operating ConditionsC. Performance Budget • Total Project funding $11.4 million - $8.9 million - DOE - $2.5 million - contractor cost share (22%)