Advanced Fuel Cell Membr

Based on Heteropolyaci

John A. Turner and F. J. John Pern

Hydrogen and Electricity, Systems and Infrastructure G

National Renewable Energy Laboratory

Golden, CO 80401-3393

Andrew M. Herring* and Steven F. Dec*

* Department of Chemical Engineering and 

** Department of Chemistry and Geochemistry

Colorado School of Mines

Golden, CO 80401-1887

May 18, 2006 

This presentation does not contain any proprietary or confidential infor

NREL/PR-560-39972Presented at the 2006 DOE Hydrogen, Fuel Cells & Infrastructure Technologies Program Review in Washington, 
Disclaimer and Government License

This work has been authored by Midwest Research Institute (MRI) under Contract No. DE-AC36-99GO10337 wDepartment of Energy (the “DOE”). The United States Government (the “Government”) retains and the publishethe work for publication, acknowledges that the Government retains a non-exclusive, paid-up, irrevocable, worldpublish or reproduce the published form of this work, or allow others to do so, for Government purposes.Neither MRI, the DOE, the Government, nor any other agency thereof, nor any of their employees, makes any wor implied, or assumes any liability or responsibility for the accuracy, completeness, or usefulness of any informaproduct, or process disclosed, or represents that its use would not infringe any privately owned rights. Referenc

specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does noimply its endorsement, recommendation, or favoring by the Government or any agency thereof. The views and authors and/or presenters expressed herein do not necessarily state or reflect those of MRI, the DOE, the Goveagency thereof. 
Overview

Timeline

• Project start date: FY 2005• Project end date: tbd• Percent complete: tbd

Budget

• Total project funding

– DOE share: $300k

• Funding received in FY05: 

– $150K (0.3 FTE)

• Funding for FY06: 

– $150K (0.3 FTE)

Targets

• Low humidity operation (25% 

RH).

• High conductivity ~0.1 S/cm• Cost $40/m2

Barriers

• Barriers addressed

O. Stack materials and 

costs

P. Durability

Partner/Subco

• Colorado School of M

– Prof. Andrew M. He– Dr. Steven F. Dec
Objectives

• Develop the methodology for the fabrication o

linked, hydrocarbon-based membranes using immobilized heteropolyacids (HPAs) as the proconducting moiety.

– Conductivity ~0.1 S/cm at 120oC and <1.5 kPa H2O

• Develop immobilization technology based on c

attachment of HPAs to oxide nano-particles. 

• Acquire an improved understanding of HPAs a

salts made by custom synthesis. 

– HPAs make up a class of inorganic proton conductors th

high proton conductivity at low humidity (below 25% RHelevated temperatures (well above 100°C). 

• Conduct relevant characterizations of the mem

better understand their structural, chemical, anproperties/stability and proton conductivity. 
HPAs: High H+ Conductivity, H

Thermal Stability; Vast Struct

Diversity; Known Redox Catal

Keggin

[SiW12O40]4-

H4SiW12O40-26H2O 

(W12-STA)

La

(allows e

p

[Si

H8SiW

(W

Dawson

[P2W18O62]6-

H6P2W18O62-xH2O
Strategies for Immobilizing H

A. Binding Approaches:

1. Covalent bonding to oxide nano-particles insitu, which can b

to, or embed physically in, a polymeric matrix

2. Direct embedding in a polymeric matrix 3. Covalent bonding directly to a polymeric matrix (CSM/3M co

poster #FCP-6)

B. Modification of Lacunary HPAs:

1. By bonding with functional silanes that can then be cross-lin

polymerized

C. Fabrication Approaches:

1. Sol gel method2. Immobilized via silylation 

onto supporting particles

3. Simple blending

D. Polymeric Matrix:

1. Organic2. Inorganic 3. Organic-inorganic hybrid

Ref. 14: “Heteropoly and 

by M. T. Pope, Springer-

C
Key Concept and Compone

in Composite Membrane Fabr
Procedure for Fabricating 3D Cross-

HPA/SiO

2/Functional Silane Sol G

Composite & PEM Membrane with 

TEOS + Functional Silane 

+ pH = 1.35 H

2O + HPA

Sol Gel 

Composite

Sol 

Solution

Host Polymer 

THF or 

diluted with THF or EtOH

Liquid Mixture

solution cast

As-cast Film

thermal or UV X-linking

Cured PEM

aged (gelled) solution

Bonded STA%, IEC, & Other Analyses/Tests

Curing A

Silanes: Methacrylate

Epoxy-type: 

HPAs:

H

4SiW12

O40 (

H

8SiW11

O39 (

K

8SiW10

O36 (

Polymer: P

(3D Network of SiO
Formation of SiO

Particles in Com

Matrix upon Th

Treatments (

Analysis

As grown with 10x diluted PEM-#9D solution

Annealed at 80°C for 20 min

Annealed at 140°C for 5 min

Anneale190°C fo

50 nm 50 nm 

50 nm
Flexibility of PEM Membra

Fabricated with High HPA Lo

PEM-#9B,C,D Films: W12-STA/(PMG + Cross-Linker) = 1
-0.2

 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Absorbance

 4000 3000 2000 

Wavenumbers (cm-1)

Immobilizing the HPA

Binding HPA with Z-6030 Silane in Sol Gel Com

Î W12-STA Retained

W12-STA/SiO2/Z-6030

As-made

H2O-washed

Z-6030

12-HSiW

SiO2

(W12-STA washed off easily without Z-6030)
Chemical Stability of Memb

and Composite PEM

2030405060708090

100

0 5 10 15 20 

Exposure Time (h)

Normalized Weight %

Chemical Stability Test of PEM Films in Fenton 

Control 

(no W12-

PEM-#5

PEM-#6 

PEM-#6

Fenton’s Reagent: 4 ppm Fe2+ + 3% H

2

O2 

at 68

o

C

PEM-#5: W12-STA at 165 wt%, cured at 145

oC/2-ton

/5

PEM-#6: W12-STA at 153 wt%, cured at 145

oC/1-ton

/5

Weight losW12-STA e
 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.026 0.028 0.030 0.032

Absorbance

 4000 3500 3000 2500 2000 1500 

Wavenumbers (cm-1)

Control (no W12-STA &SiO2)

Control (no W12-STA)

PEM-#7 (W12-STA at 174 wt%)

PEM Mechanical Strength and Flex

Reduced by Increasing HPA Load

FTIR-ATR Spectra of Cured Control Blanks and PEM-#7

(H2O)

Film 

Flexibility

Reduced

Low STA wt%

High STA wt%
H

+ Conductivity as a Functio

Cell Temperature at 100% 

05

1015202530

1 11 21 31 41 51 61 71 81 9

CV Scan Sequence

H+ Conductivity (mS/cm) Forward Scan (-0.50V - 0.0V)

Return Scan (0.0V - -0.50V)

Proton Conductivity of PEM-#9D, Film #1, Stri

Scan Ra

-0.50V - +

Scan Rate (mV/s):

10 50 100

10 50 100

10 50 100

10 50 100 10

27

oC/100%RH

80

oC

70

oC/100%RH

60

oC/100%RH

40

oC/100%RH
Improving H+ Conductivity with Hig

Loading and Better Membrane Fab

Table 1. PEM Compositions vs Proton Condutivity Derived from I-V Curv

Weight Ratio

PEM ID HPA Host Polymer X-Linker HPA/(PMG + X-Linker) 80oC/100%RH 100oC/46

1 HSiW12Ox BSPPO No 0.56 0.152 HSiW12Ox PMG Yes 0.81 6.93 HSiW11Ox PMG Yes 1.09 6.4, 10.46 2.41 4 KSiW10Ox PMG Yes 1.05 7.56, 13.3 1.61 5 HSiW12Ox PMG Yes 1.50 8.86 HSiW12Ox PMG Yes 1.54 15.577 HSiW12Ox PMG Yes 1.74 14.55 2.18 HSiW12Ox PMG Yes 1.74 19.17 3.81

9B HSiW12Ox PMG Yes 1.74 22.28

9C HSiW12Ox PMG Yes 1.74 21.159D HSiW12Ox PMG Yes 1.74 25.45 [28.25 at 

Nafion 112 SO3H 149.9 98.9

1 Values of the proton conductivity at 120oC/23%RH are with large uncertainty because of rapidly los

Components Best Proton Condu
High H

+ Diffusion Coefficien

Composite Membrane

0.0E+00

5.0E-061.0E-051.5E-052.0E-052.5E-053.0E-05

20 40 60 80 100 

Temperature (

oC)

H+ Diffusion Coefficient (cm 2/s)

(8.8 mS/cm at 80

oC

Na

PEM-#5

Proton Diffusion Data from PFG-NMR Measu

(W12-STA at 150 wt%)
-1.50-1.25-1.00-0.75-0.50-0.25

0.00

25 50 75 100 125 150 175 200 225

Temperature (oC)

Heat Flow (W/g)

DSC Thermograms of W12-STA, SiO2, and Two Sol Gel Composites

W12-STA

SiO2 Sol Gel

TEOS-0303A 

(Z-6030)

TEOS-0304 

(A-186)

6065707580859095

100

25 75 125 175 225

Temperature (

oC)

Weight (%)

-0.35-0.25-0.15-0.050.050.150.25

Heat Flow (W/g)

TGA and DSC Thermograms for PEM-20050823 Membrane

TG

A

DSC

22o

C

80o

C

145o

C

145o

C

22o

C

80o

C

TGA and cast, 80

oC

and 145

oC

W12-STA/SiO

2/Z-

W12-STA/SiO

2/A-

PEM-#6: W1level at 153 wlinker)

Moisture 

Capabilit

STA an

Comp

(DSC A
Summary of Accomplishme

PEM Fabrication and Performance

• We have shown the ability to retain HPAs into a 

composite matrix of our design.

• Properties of HPA-based composite PEMs:

– high chemical stability (Fenton’s reagent test)– good thermal stability (with highly reactive W12-STA)– good mechanical flexibility– effective binding of silicotungstic acids (Wn-STA) with se

silanes (n = 10, 11, 12)

– high Wn-STA loading [HPA/(PMG + X-Linker) > 150 wt%– moderate proton conductivity (25 mS/cm at 80

oC/100%R

• Clear progress towards meeting the DOE targe
Achieving Fundamental Go

Future Work

• To continue to improve/modify/optimize the cu

composite formulation, fabrication, and procesconditions

– to enhance PEM’s thermal stability in the 90-120

oC rang

– to improve mechanical strength and flexibility– to reduce membrane thickness and improve film uniform

• To continue to develop immobilization strategi

various HPAs, custom-synthesized at CSM, thahigh proton diffusion coefficients and thermal 

• To understand the binding mechanism of HPA 

functional silanes and SiO

2 nano-particles in th

matrix.

• To understand the proton conduction mechani

3D cross-linked composite membranes in ordefurther improve proton conductivity at low hum

elevated temperatures.
2005 Reviewers’ Commen

“One of the few new, alternative ideas for membranes in the 

program”

• Issues:

– ...needs to present conductivity values for membranes with “fix

• Done

– HPA approach is sound as a demonstration but water solubil

addressed...

• Excellent progress has been made in this regard

– Nafion doped in HPAs has been shown to be feasible...the PI i

insight.

• Not part of our project, those figures were for introduction t• Our project is focused on developing a composite hydrocarbon 

HPAs as the proton conducting moiety that will meet the DOE 

operation at low RH and higher temperatures

• Future:

– Need durability studies in actual operating fuel cell conditions a

and RH cycling...gas crossover measurements

• PEMs of 3D cross-linked PMG matrix were not available yet at • These subjects will be investigated for HPA-based PEMs this 
Presentations and Publicati

1. A. M. Herring, J. A. Turner, S. F. Dec, M. A. Sweikart, J. L. Malers, F. Meng, F. J. Pern, J. Horan

Use of Heteropoly Acids in Composite Membranes for Elevated Temperature PEM Fuel Cell Ope

from Three Different Approaches," 2004 Joint International Meeting, W1 - Fourth International Sy

Conducting Membrane Fuel Cells, 206th ECS Meeting, October 3-8, 2004, Honolulu, HI.

2. F. J. Pern, J. A. Turner, and A. M. Herring; "Hybrid Proton-Carrier Polymer Composites for High-T

Applications," in Na

nostructured Materials in Alternative Energy Devices, edited by Erik M. Kelder

Jean-Marie Tarascon, and Yet-Ming Chiang (Mater. Res. Soc. Symp. Proc. 822, Warrendale, PA 

S.8.6.6.

3. A. M. Herring, J. A. Turner, S. F. Dec, M. A. Sweikart, J. Malers, F. Meng, J. Pern, J. Horan, and 

Heteropoly Acids In Composite Membranes for Elevated Temperature PEM Fuel Cell Operation; 

Thr

ee Different Approaches.” Fuel Cell Seminar, 2004.

4. F. J. Pern, J. A. Turner, Fanqin Meng, and A. M. Herring; “Sol-Gel SiO2-Polymer Hybrid Heteropo

Exchange Membranes,” MRS 2005 Fall Meeting, Energy and The Environment Symposium, Sess

Cycle—Generation, Storage, and Fuel Cells. In press.

5. F. J. Pern, J. A. Turner, and A. M. Herring; “Hybrid Proton Exchange Membranes Based on Heter

Sulfonic-Acid Proton Conductors,” ECS 2006, Abstract (accepted for oral presentation)

6. J. L. Horan , J. Turner , A. M. Herring, and S. Dec; “Structure and Dynamics of Non-Commercial 

Fuel Cell Applications,” ECS 20

06, Abstract 

7. N. V. Aieta, M. Kuo, F. Meng, J. Turner, and A. M. Herring; “The Use of Heteropolyacids as Addi

Operation of Nafion Membranes for PEM Fuel Cell Applications,” ECS 20

06, Abstract 

8. A. M. Herring, R. J. Stanis, J. Ferrell III, M. Kuo, J. Turner, and M. Samaroo; “The Use of Heterop

Electrocatalysts for the Oxygen R

eduction Reaction in PEM Fuel Cells,” ECS 2006, Abstract 

9. R. J. Stanis, A. M. Herring, M. Kuo, and J. Turner; “Increased CO Tolerance of Pt Electrodes by A

Heteropoly Acids and Salts in PEM Fuel Cell Anode Catalysts,” ECS 2006, Abstract