Development of Nanocomposite Membranes

for

High Pressure PEM Fuel Cell/Electrolyzer Applications

Michael Pien, Marvin Warshay, Steven Lis, Radha JalanElectroChem, Inc 400 W. Cummings Park Woburn, MA 01801

Christine Felice, Deyang Qu Dept of Chemistry, University of Massachusetts Boston, Boston, MA 01225

AIAA

Denver, COAugust 5, 2009

Advance in Polymer Nanocomposites US 2,531,396 1950 Elastomer Reinforced with a

Modified Clay

US 3,084,117 1963 Organoclay Polyolefin Compositions

US 4,739,007 1988 Composite Material and Process for Manufacturing

Clay-based Thin Film as Gas Barrier - Claist

Perfluorinated Sulfonated Polymer as Proto Exchange Membrane

- high temperature fuel cell - direct methanol fuel cell

Structure of Platelets for Barrier

Gallery Height

(exchangeable)

Tetrahedral

Octahedral

Tetrahedral

Different Types of Composites

Conventional Composite

Intercalated Nanocomposite

Exfoliated Nanocomposite

Polymeric Proton Conductive Membrane

O2 H2

e-

H+

Proton Exchange Membrane (PEM)- perfluorinated sulfonate polymer

2 e- + 2 H+

H2O

2 e- + 2 H+

V

Hydrogen Crossover

• Development of mixed potential

• Decrease current efficiency

• Different thermal and water management

• Hot spots

Objectives

• Develop Low H2 Crossover proton conductive polymer membranes for High pressure and Low current density operating electrolyzers

• Retain high proton conductivity of the new membranes

• Investigate the morphology of the new membranes for the reduction of H2 crossover

Selection of Platelets

• Swelling properties

• Capacity of host water and organic molecules

• High cation exchange capacities

• High aspect ratio

• Large surface area

H2 Permeation Evaluation

• Electrochemical method• Limiting current density

H2

Referenceelectrode

Workingelectrode

Counterelectrode

V

H2 N2

H2 = 2 H+ + 2 e-

Conductivity Evaluation

• In-the-plane conductivity - impedance - various humidity and temperature

• Through-the-plane conductivity - impedance

H2 Permeation of the Nanocomposite Membranes

Initial Results of the New Nanocomposite membranes

Membrane wt% clay Thickness10-3 in

H2 crossover

mA/cm2

ConductivitymS/cm

Nafion 211 0 1 0.923 11.9

Nafion 115 0 5 0.385 11.1

Membrane A 10% 1.5 0.385 8.9

Membrane B 10% 3 0.231 8.8

Membrane C 20% 1.5 0.269 5.8

Fuel Cell Evaluation

Membrane D : hot-pressing a Membrane A (10% clay) between two Nafion 212 membranes Membrane F : hot-pressing a Membrane C (20% clay) between two Nafion 212 MembranesThe thickness of membranes D and F is about 5 mils similar to the thickness of Nafion 115 membrane

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.00 0.10 0.20 0.30 0.40 0.50

Voltage, V

H2

cro

sso

ver

curr

ent,

mA

/cm

2

2 mil thick

5 mil thick

Nafion 211

Nafion 212

Nafion 115

Nafion 211

Nafion 115

Nafion 212

5% Clay

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0

C onduc tivity, mS /c m

H2

Cro

sso

ver

Cu

rren

t, m

A/c

m2

NP 0902-003

NP 0902-004

NP 1001-003

NP 1001-013

NP 05003

NP 05004

NP 1201-002

NP 1203-001

NP 1203-002

NP 1204-004

NP 1201-003

NP 1204-002

NP 1201-004

Which Composite ?

Conventional Composite

Intercalated Nanocomposite

Exfoliated Nanocomposite

Nanocomposite Membranes Optimization

• Selection of materials

• Design of Experiment

Pretreatment

Particle size

Loading

Mixing

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.0 0.1 0.2 0.3 0.4 0.5 0.6

Voltage, V

H2

cro

sso

ver

curr

ent,

mA

/cm

2

1.5 mils

2.5 mils

4 mils

5% Clay

Methods of Melt Process

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80

Voltage, V

H2

cro

sso

ver

curr

ent,

mA

/cm

2

Mechanical Stir

Sonication

10% Clay

Thickness: 3 mils

Conclusions

• Polymer Nanocomposite based on platelets can reduce the hydrogen permeation

• Polymer nanocomposite membranes can keep good proton conductivity

Future work

• Optimize new polymer nanocomposites based on a Design of Experiment

• New polymer nanocomposites that allow durability characterization

Acknowledgement

This work is funded by

NASA under Contract NNX09CA92C

Electrolyzer Evaluation

0

0.5

1

1.5

2

2.5

0 200 400 600 800 1000 1200

current density, mA/cm2

Cel

l Vo

ltag

e, V

Nafion Clay Composite Membrane Electrochem Supplied JPL Electrolysis MEA Process with Pt cathode /IrO2 anode

70 oC , Ambient Pressure

C onductivity * L imiting C urrent T hickness/A pply C lay(mS/cm) (mA /cm2 ) (mils/coating times) wt%

N P0 9 0 2 -0 0 3 0 .0 8 7 0 .4 6 7 2 .3 / 1 1 0N P0 9 0 2 -0 0 4 0 .0 8 8 0 .1 0 5 5 / 1 1 0N P1 0 0 1 -0 0 3 0 .8 7 6 0 .3 0 7 3 / 1 sonicate 1 0N P1 0 0 1 -0 1 3 0 .5 7 8 0 .6 0 1 2 / 1 1 0N P0 5 0 0 3 5 .5 6 3 0 .5 6 0 2 / 1 1 0N P0 5 0 0 4 7 .2 1 0 0 .2 7 1 4 / 2 1 0N P1 2 0 1 -0 0 2 7 .7 6 0 0 .8 8 2 1 .5 / 1 5N P1 2 0 1 -0 0 3 8 .6 1 1 0 .4 4 3 3 / 3 5N P1 2 0 1 -0 0 4 6 .4 4 5 0 .4 0 0 2 .5 / 2 5N P1 2 0 3 -0 0 1 1 6 .2 6 1 0 .7 4 7 2 / 1 5N P1 2 0 3 -0 0 2 9 .5 5 0 0 .4 1 8 3 .6 / 2 5N P1 2 0 4 -0 0 2 2 5 .6 1 2 0 .5 3 7 2 / 2 5N P1 2 0 4 -0 0 4 1 4 .1 0 5 0 .5 1 9 2 / 2 sonicate 5

Membrane ID Mixing