design and development of high-performance polymer fuel

Design and Development of High-Performance Polymer Fuel Cell Membranes

Ryo TamakiJoyce HungSteve RiceJoe Suriano

GE Global ResearchMay 16th 2007

Project ID# : FC19

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

2007 DOE Hydrogen Program Annual Merit Review / Tamaki 5/16/2007

Project start date: 4/2006

Project end date: 4/2011

Percent complete: 25%

Barriers addressed• Membrane cost• Membrane durability

Total project funding• DOE share: $1.5M• GE share: $0.5M

Funding received in FY06• DOE share: $150k• GE share: $50k

Funding for FY07 • DOE share: $300K• GE: $100K

Timeline

Budget

BarriersOverview

Partners

GE Energy


Objectives

FY06• Design and synthesize new high performance polymer structures• Design and synthesize hydrophilic organic additives• Evaluate membrane performance with and without additives

FY07• Design and synthesize cross-linked system • Prepare high acid density PEM in porous supports• Integrate hygroscopic inorganic additives• Evaluate membrane performance at different relative humidity• Improve chemical and thermal stability

FY08• Improve conductivity at low RH and high temperature (0.1S/cm 50%RH/120°C).

Design and develop novel polymer electrolyte membrane materials for fuel cell operation at high temperature

(up to 120 °C) and low relative humidity (25-50 %RH)


Approaches

• High acid concentration with no leaching• Cross-link chemistry design• Control of the cross-link density• Selection and fabrication of the porous supports• Impregnation• Evaluation of properties

• Improvement in the conductivity, especially at low RH

Gen 1Gen 1

Gen 2Gen 2

Gen 3Gen 3Gen 4 : Cross-linked system in porous supportGen 4 : Cross-linked system in porous support

Hygroscopic additives

Gen 5 : with inorganic additivesGen 5 : with inorganic additives

Copolymer architecture

Cross-linked system in porous support

Introduction of the inorganic additives

• Thermally stable aromatic hydrocarbon polymers • Balance proton conductivities, water uptake, and mechanical properties via material design


Control in copolymer architecture

100 nm100 nm100 nm

Gen 1 : random copolymer

σ ~ 10-3 S/cm (50 %RH)

100 nm100 nm100 nm

Gen 2 : block copolymer

σ ~ 10-2 S/cm (50 %RH)

• Hydrophilic-hydrophobic phase separation is observed in Gen 2.

• The phase separated hydrophobic segment is expected to work as a scaffold and suppress the water uptake.

• Higher conductivity in Gen 2 through formation of efficient hydrophilic channels.

• Hydrophilic-hydrophobic phase separation is observed in Gen 2.

• The phase separated hydrophobic segment is expected to work as a scaffold and suppress the water uptake.

• Higher conductivity in Gen 2 through formation of efficient hydrophilic channels.


Water Uptake

• Water uptake was reduced in Gen3.

• Gen 2 demonstrated conductivity at the same level as Nafion.

• Within Gen 3, higher acid concentration resulted in the higher conductivity.

• Water uptake was reduced in Gen3.

• Gen 2 demonstrated conductivity at the same level as Nafion.

• Within Gen 3, higher acid concentration resulted in the higher conductivity.

020406080

100120140

20 40 60 80 100 120Temperature (°C)

Wat

er U

ptak

e (%

) Nafion 117Gen1Gen2Gen3AGen3B

Conductivity at 80°C

0.0001

0.001

0.01

0.1

0 25 50 75 100 125

% Relative Humidity

Con

duct

ivity

[S/c

m] Nafion 117

Gen1Gen2Gen3AGen3B


Conductivity vs. Water Uptake

0 30 60 90 120 1500.00

0.04

0.08

0.12

0.16

0.20

Con

duct

ivity

at 8

0C a

nd 1

00%

RH

(S/c

m)

Water uptake at 30°C (wt%)

Gen 1Gen 2AGen 2BGen 3Nafion

0 30 60 90 120 1500.00

0.04

0.08

0.12

0.16

0.20

Con

duct

ivity

at 8

0C a

nd 1

00%

RH

(S/c

m)

Water uptake at 30°C (wt%)

Nafion

• Good balance of water uptake and conductivity was achieved in Gen3.

• Further increase in the conductivity is required to meet the Y3 DOE target (0.1S/cm 50%RH/120°C).

• However, higher increase in the acid groups make the polyelectrolyte soluble in water.

• New approaches (Gen 4 and 5) were investigated.

• Good balance of water uptake and conductivity was achieved in Gen3.

• Further increase in the conductivity is required to meet the Y3 DOE target (0.1S/cm 50%RH/120°C).

• However, higher increase in the acid groups make the polyelectrolyte soluble in water.

• New approaches (Gen 4 and 5) were investigated.


Selection of cross-linkable electrolyte unitsCritical factors for the electrolyte units

1. Thermal / oxidative stability2. Acid density3. Controllable cross-link density4. Compatibility with the pore supports

H

HH

H

H

H

H

H

H H

H H H H

H H

H

H

H HH H

H

H

H

H

+

Acid unit Cross-link unit

Number of arms / size

Type / number of

acid groups

Cross-link chemistry

Proton conductivity Morphology

Thermal / oxidative stability

Hydrolytic stability

Dimensional stability

VariablesVariables

PropertiesProperties


Fabrication of cross-linked PEM in porous support

Cross-linked system provides : 1. Increase in acid concentration 2. Dimensional stability3. Thermal stability

Porous support provides : 1. Mechanical strength 2. Dimensional stability3. Thermal stability4. Morphology (hydrophilic channel)

control by template effect

polyelectrolytes


Selection of porous supports

100μm

Pore support APorosity ~45%

Pore support BPorosity ~90%

goodneutralbad

Critical factors A B1. Mechanical strength2. Thermal / oxidative stability3. Porosity / pore size / surface area4. Pore morphology5. Compatibility with the polyelectrolytes6. Scalability 7. Ease of handling8. Cost


Control in the cross-link density – Gen 4A

-Wt loss (100°C/2h) 70%

• Higher conductivity was obtained by incorporating acid units (100%) in a porous support.

• But the electrolyte was extracted out from the support by boiling for 2h due to the high acid concentration and the solubility in water.

• Higher conductivity was obtained by incorporating acid units (100%) in a porous support.

• But the electrolyte was extracted out from the support by boiling for 2h due to the high acid concentration and the solubility in water.

- cross-link chemistry A / acid unit A -

Conductivity at 80 °CConductivity at 80 °C

0.0010

0.0100

0.1000

1.0000

20 40 60 80 100

RH (%)

S/c

m Acid unit-ANafion 112

H

H

Acid unit


Control in the cross-link density – Gen 4AEffect of the cross-linker content on the leaching and the proton conductivity

Extraction at different temperaturesExtraction at different temperatures

• Leaching was suppressed by increasing the cross-linker content.

• The decrease in conductivity with increase in cross-linker content is due to lower acid concentration.

• Leaching was suppressed by increasing the cross-linker content.

• The decrease in conductivity with increase in cross-linker content is due to lower acid concentration.


-80%-70%-60%-50%-40%-30%-20%-10%

0%10%20%

0.00 5.00 10.00 15.00

[crosslinker] / [acid unit]

wei

ght l

oss

30C60C85C100CTotal

0.0001

0.0010

0.0100

0.1000

1.0000

0.00 5.00 10.00 15.00[crosslinker] / [acid unit]

S/cm

25 %RH100 %RHNafion at 25% RHNafion at 100% RH

H

H

+


Incorporation of inorganic additives – Gen 5A

• Addition of the inorganic additive decreased acid group leaching at low temperatures.• The conductivity improved with the inorganic additive, especially at low RH.

(Exceeds the Y2 DOE target 0.07 S/cm at 80 %RH)• Weight loss was still observed at high temperature and needs to be improved.

• Addition of the inorganic additive decreased acid group leaching at low temperatures.• The conductivity improved with the inorganic additive, especially at low RH.

(Exceeds the Y2 DOE target 0.07 S/cm at 80 %RH)• Weight loss was still observed at high temperature and needs to be improved.

Extraction at different temperaturesExtraction at different temperatures Conductivity at 80 °CConductivity at 80 °C

-60%

-40%

-20%

0%

20%

40%

60%

1 2 3 4 5

Weight Loss

30C60C85C100CTotal

Gen 4A

Gen 5A

-60%

-40%

-20%

0%

20%

40%

60%

1 2 3 4 5

Weight Loss

30C60C85C100CTotal

Gen 4A

Gen 5A

0.0001

0.0010

0.0100

0.1000

1.0000

0 20 40 60 80 100 120

RHS/

cm

Gen4ANafion 112Gen5A


0.0001

0.0010

0.0100

0.1000

1.0000

0 20 40 60 80 100 120

% Relative Humidity

Con

duct

ivity

[S/c

m]

Gen4BNafion 112

Alternative cross-link chemistry – Gen 4B

-Wt loss (100 °C/2h) 0%

H

H

+


Cross-link chemistry was re-evaluated and optimizedCross-link chemistry was re-evaluated and optimized

• Membrane experiences no leaching.

• The conductivity is comparable to Nafion.


• The conductivity is comparable to Nafion.



0.0001

0.0010

0.0100

0.1000

1.0000

0 20 40 60 80 100 120

% Relative Humidity

Con

duct

ivity

[S/c

m] Nafion 112

R423-15-1R423-17-4R423-17-5R423-17-6R423-17-7R423-17-8R423-17-9

Alternative cross-link chemistry – Gen 4BH

H

+



• The conductivity exceeds Nafion.


• The conductivity exceeds Nafion.


OptimizationOptimizationPorous Support


Alternative cross-link chemistry – Gen 4B

Before acidificationBefore acidification After acidificationAfter acidification

Td = 563°C Td (1) = 285°C Td (2) = 550°C

• Very high thermal stability (Td = 550°C) was achieved.

• No Tg observed before decomposition.

• Very high thermal stability (Td = 550°C) was achieved.

• No Tg observed before decomposition.


0%

5%

10%

15%

20%

25%

30%

35%

40%

Gen 4B Gen 2

XYZ

0%

50%

100%

150%

200%

250%

300%

Gen 4B Gen 2

Alternative cross-link chemistry – Gen 4Bwater uptake and dimensional changes

Water uptake (30°C)Water uptake (30°C) Dimensional changes (30°C)Dimensional changes (30°C)

• High water uptake in Gen4B compared to Gen2.

• Dimensional changes are at the same level as Gen2, but the thickness change for Gen4B is much smaller.

• High water uptake in Gen4B compared to Gen2.

• Dimensional changes are at the same level as Gen2, but the thickness change for Gen4B is much smaller.

Gen 4B

(Cross-linked)

Gen 2

(Not cross-linked)

Gen 2

(Not cross-linked)

Gen 4B

(Cross-linked)

Very small thickness change


Future work FY07/FY08

Materials synthesis• Demonstrate feasibility of cross-linked electrolytes in porous supports• Evaluate the effect of acid/cross-linker ratios on the conductivity• Study the effect of inorganic additives on the conductivity• Evaluate the effect of pore size, porosity and thickness of porous

supports on the conductivity

Membrane evaluation• Evaluate membrane properties (proton conductivity, water uptake,

mechanical properties)


Summary

Relevance : Apply new concepts in polymer membrane design to resolve challenging technical issues related to membrane performance over a wide range of temperatures and humidities.

Approach : Design and synthesize new polymer architectures by formation of the cross-linked electrolytes in porous supports with controlled structures. Explore hygroscopic additives to improve performance at high temperature, low RH.

Progress : Developed completely aromatic hydrocarbon based polymer architectures with concentrated proton conducting functionalities, demonstrating improved balance of water uptake and proton conductivity.

Developed cross-linked electrolytes in porous supports with or without hygroscopic inorganic additives. Demonstrated higher conductivity than Nafionover wide range of relative humidity.

Future research : Continue design and evaluation of new materials. Develop further understanding of the effect of membrane architecture on performance.


Summary Table

Parameters FY06 target FY06 results FY07 target FY07 resultsConductivity (S/cm) 0.07 0.17 0.07 0.11 0.37Temperature (°C) rt 80 rt 80 80RH 100% 100% 80% 80% 100%

Results and DOE high temperature membrane targets


Acknowledgment: “This material is based upon work supported by the Department

of Energy under Award Number DE-FG36-06G0 16034"

Disclaimer: “This report was prepared as an account of work sponsored by an

agency of the United States Government. Neither the United States Government

nor any agency thereof, nor any of their employees, makes any warranty, express

or implied, or assumes any legal liability or responsibility for the accuracy,

completeness, or usefulness of any information, apparatus, product, or process

disclosed, or represents that its use would not infringe privately owned rights.

Reference herein to any specific commercial product, process, or service by trade

name, trademark, manufacturer, or otherwise does not necessarily constitute or

imply its endorsement, recommendation, or favoring by the United States

Government or any agency thereof. The views and opinions of authors expressed

herein do not necessarily state or reflect those of the United States Government or

any agency thereof.”

design and development of high-performance polymer fuel

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