Advanced Fuel Cell Memb

Based on Heteropolyac

John A. Turner and John Pern

Hydrogen and Electricity, Systems and Infrastructure G

National Renewable Energy Laboratory

Golden, CO 80401-3393

Andrew M. Herring,* Steven F. Dec

x,

Fanqin Meng,* Jennifer L. Malers,* and James 

Department of Chemical Engineering* and 

Department of Chemistry and Geochemistry

x

Colorado School of Mines

Golden, CO 80401-1887

May 24, 2005 

This presentation does not contain any proprietary or confidential inform

NREL/PR-560-38191Presented at the 2005 DOE Hydrogen, Fuel Cells & Infrastructure Technologies Program Review
Overview

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

• Barriers addre

– Thermal, Air 

Management

– Cost.– Durability • Total project funding

– DOE share: $150k

Budget

• 3M• Colorado Sc

Mines.

Partner

Timeline Barriers
Objectives and Approa

• To demonstrate dry inlet gas operat

HPA-based PEMs in FC at T 

≥ 80

oC.

• Synthesize and characterize selecte

“saturated” and lacunary heteropoly 

(HPA) that have high potential for thfabrication of FC membranes 

• Fabricate heteropoly acid-based pro

exchange membrane (PEM)

– Mechanically strong – Stable operation– Low-cost– Higher temperature/low humidity operat
Example Structures of Three 

[SiW12

O40

]4-

H

4SiW12

O40-22H

2O 

(12-HSiW)

[SiW11

O39

]8-

H

8SiW11

O39-26H

2O 

(11-HSiW) [P

2

W

H

6P2W

(18-

1. Keggin(saturated)

2. Lacunary(vacant sites)

3. D
TGA for Various HPAs

(after heating to 110 °C)

HPA Water of 

crystallization 

Secondary structure 

water 

Neutralizatio

Equiv. 

H

2O 

Temp.

°

C 

Equiv. 

H

2O 

Temp.

°C Equiv. 

H

2O 

Tem

H3PW12

O40 1 50 6 164 1 4

H8SiW11

O39 2 60 7 152 6 4

H6SiV

2

W10

O40 6 129 2 2

H8SiV3W10

O40 7 183 

H6ZnW12

O40 10 90 10 160 2 4

H6P

2

W18

O62 4 114 3 2

Na

x

H

y P

2

W18

O62 7 60 5 114 

H6As

2

W21

O69 12 129 4 4

2 316 

H6P

2

W21

O71 4 170 3 3

H21

B3W39

O132 17 59 7 203 4 3
Proton Diffusion Coefficien

HPAs Determined by PF-N

HPA Max 

diffusion 

coefficent x 

10-6 cm2

s-1

Temperature of 

maximum D, oC 

Ea 

before 

Max T, 

kJ mol-1

IR Hbond 

strength 

Second

12-HPW 25 117 13 20 H

+(H2O)

12-HSiW 30 130 20 40 H

+(H2O)

12-HZnW 2 108 27 30 H5O2

+

, O

12-HGeW 0.7 90 35 11-SiW11 3 108 6 35 H5O2

+

, O

39-HB3W 7 128 8 18 H

+(H2O)

18-HP2W 1.2 >150 20 20 H3O

+ 

21-HAs2W 3.7 >150 18 18 H5O2

+

21-H2Rb4As2W 30 25 - H

+(H2O)

21-HP2W 2.3 110 24 27 H3O

+
Polarization curves of PEM made 

HPW physically blended in PVD

0

0.10.20.30.40.50.60.7

0 200 400 600 800 1000 1200 1400 

I (mA/cm2

)

E (V)

2HC

F2 * C

F2C

FC *

CF3

x

y
Diffusion coefficient data for 

doped Nafion

® 112 proton

0.00.20.40.60.81.01.21.41.61.8

20 40 60 80 100 

T (°C)

D (x105 cm

2

/s)

Nafion12-HSiW18-HP2W21-HAs2W12-HPW21-HP2W
Polarization curves comparing 

and HPA-doped Nafion

®

0.10.20.30.40.50.60.70.80.9

0 200 400 600 800 1000 1200 

I mA/cm2

E(V)

cHHH

120 oC Nafion

® 112, 25% RH, No ionomer in electrod

(ELAT) 0.5 mg/cm

2 20% Pt on carbon. 
Strategies for Immobilizing H

A. Bonding Approaches:

1. Covalent bonding directly to a polymeric matrix2. Covalent bonding to oxide nanoparticles, which ca

bond covalently to, or embed physically in a polym

3. Direct embedding in a polymeric matrix

B. Modification of Lacunary HPAs:

1. By bonding with functional silanes that can then c

be 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
Multiple Approaches for M

HPA-based Hybrid PEM

Sol gel composite 

having HPA covalently 

bonded to, or physically 

embedded, in SiO2 

─

silane matrix

Film forming 

of polymer 

and meth

forming 

polymeric m

HPAs synthesis 

and 

characterization

Sol gel synt

method a

conditio

mechanically strong, thermally 

stable, high performance, 

hybrid FCPEM membranes
Polymerization Methods for immo

H

+ Carrier/Transmitter Compos

1. Post-Polymerization:2. Pre-Polymerization3. Co-Polymerization:

C=C---Si-O-(H

+)-O-Si- C-C---Si-O-(H

+)-O

C-C---Si(OR)

3 (+ SiO

2) + (H

+

) C-C---Si-O-(H

C=C---Si(OR)

3 + (H

+) 

(+ SiO

2) (+ Modifier) C-C---Si-O-(H

(H

+): proton 
Procedure for Fabricating Hy

Composite PEM Membran

TEOS + Functional Silane

+ pH=1.35 H

2O + HPA

Sol gel film 

or powders

Sol solution Polymer dissolve

solvent (EtOH 

diluted with EtOH or THF

Liquid Mixture

solution cast

As-cast film

thermal press/X-link or UV 

Cured PEM

aged (gelled) solution

Bonded STA%, IEC, & other analyses/tests

Curing A

Silanes: Methacryla

Epoxy-type: A

HPAs:

H

4SiW12

O40 

H

8SiW11

O39 (11

K

8SiW10

O36 (10
“Bonding HPA”: Sol Gel Com

(No Silane

)

Î 12-HSiW Wash

FJP-0108, SiO2-HSiWOx as-made; Tue Jan 21 10:58:29 2003FJP-0108 (TEOS-HSiWOx) Powder Washed; Sat Jan 25 14:17:50 2003HSiWOx powder in KBr Thu Nov 14 12: 27:07 2002TEOS-02 SiO2 Powder Washed; Sat Jan 25 15:05: 02 2003

-0.0

 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Absorbance

 3500 3000 2500 2000 1500 

Wavenumbers (cm-1)

As-made

H

2O-washed

12-HSiW

SiO

2 sol gel

12-HSiW/SiO

2
“Bonding HPA”: Sol Gel Compos

Z-6030 silane

)

Î 12-HSiW Reta

TEOS-0111 (TEOS+Z6030+HSiWOx) Air-dried Film; Tue Jan 21 11:29:01 2003TEOS-0111 (TEOS+Z6030+HSiWOx) Powder Washed; Sat Jan 25 14:47:12 2003HSiWOx (IPA) on KBr Thu Nov 21 17:23:06 2002Z-6030 pure in KBr Thu Nov 14 17:03:05 2002TEOS-02 SiO2 Powder Washed; Sat Jan 25 15:05: 02 2003

-0.15-0.10-0.05

 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Absorbance

 3500 3000 2500 2000 1500 

Wavenumbers (cm-1)

12-HSiW/SiO

2/Z-6030

As-made

H

2O-washed

Z-6030

12-HSiW

SiO

2
HSiWxOy Bonded/Embedded to Silic

Network and IEC of Sol Gel Compo

Table 1. Molar Ratios vs. Weight% of Bonded HSiWOx and IEC of Composite 

Sample Composition Molar Ratio Normaliz. to SiO2 Bonde

ID SiO2/Silane/HPA COS/TEOS Silane HSiWOx Rat

Cab-O-Sil Approach

W12-STA

FJP-1004 COS/Z-6030/HSiWOx 1.00 0.62 0.016 39FJP-1012 COS/HSiWOx 1.00 0.00 0.016 6FJP-1126* COS/Z-6030/HSiWOx 1.00 0.33 0.04 0Sol Gel ApproachFJP-0108 TEOS/HSiWOx 1.00 0.00 0.04 15TEOS-0111 TEOS/Z-6030/HSiWOx 1.00 0.63 0.04 36TEOS-A186 TEOS/A-186/HSiWOx 1.00 0.90 0.03 88

TEOS-A187 TEOS/A-187/HSiWOx 1.00 1.01 0.03 79

TEOS-0303A TEOS/Z-6030/HSiWOx 1.00 1.88 0.06 95TEOS-0304 TEOS/A-186/HSiWOx 1.00 1.80 0.06 99

W11-STA

TEOS-0403 TEOS/Z6030/HSiW11Ox 1.00 0.94 0.06 97

TEOS-0404 TEOS/A-186/HSiW11Ox 1.00 0.90 0.06 95

* Final solution pH~4.3; all others pH 

≤ 1.0. IEC are for H

2O-washed 
-1.5-1.0-0.5

0.0

Heat Flow (W/g)

25 50 75 100 125 150 175 

Temperature (°C)

––––––– P-HSiWOx.001 Powder HSiWOx– – – – TEOS-02-H2O.000 TEOS-02 SiO2 Powder H2O-Washed––––– · TEOS-0304.000 TEOS-0304––– – – TEOS-0303A.000 TEOS-303A

11/27/2003 John Pern

DSC Thermograms of SiO2 sol gel (from TEOS), W12-STA,

and sol gel composites TEOS-0303A and TEOS-0304

Exo Up 

Water-retention capability of SiO2, 12

and two 12-HSiW/SiO2/Silane sol 

composites (DSC Analysis)

SiO2

12-HSiW

TEOS-0304 

(A-186)

TEOS-0303A 

(Z-6030)
 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040

Abs

 2000 

cm-1

PEM-0105 as-cast film; 

12-HSiW Sol Gel C

BSPPO Hybrid 

TGA-FTIR Analysis:PEM-0105 Oven-heated 

50556065707580859095

100

25 75 125 175 

Temperature (oC)

Weight (%)

PEM-0105.APEM-0105.B

1. As-Cast Film2. 120oC Oven-Heated for 1 

1

12-HSiW/BSPPO = 44 wt% SiO2/BSPPO = 13.5 wt%

BSPPO: a specialty 

polypropylene oxide
6065707580859095

100

Weight (%)

25 75 125 175 225 275 325 

Temperature (°C)

––––––– PEMAGMA DP PEMAGMA DP– – – – AX-8950 AX-8950––––– · STA12#2 SiO2 12WO3 26H2O #2––– ––– TEOS-0304#2 TEOS-0304#2 washed, oven dried––––– – PEM-0624A.001 PEM-0624A #2–– –– – PEM-0624ADP PEM-0624ADP––––––– Nafion117 08-07-03 Nafion 117 8/07/03

8/08/2003 TGA Data Files

TGA Thermograms of PEM-0624A Membrane and its Key Components

TGA Analysis of a Hybrid Mem

and its Key Components

PEMAGM

12-HSiW

Uncured PEM-0410A

Cured 

PEM

TEOS-0304

Nafion 117

12-HSiW/SiO2/A-186/
Flexible, high-HSiW-loading hy

PEMs are obtained for the first 

PEM-20050404A: 11-HSiW/TEOS/Z6030/PEMAGMA, STA/PPEM-20050404B: 12-HSiW/TEOS/Z6030/PEMAGMA, STA/P

145C/10m Cured
Accomplishments/Progres

– HPA and Doped Nafion

• HPAs: A large number of HPAs based on the Keggin, Daws

more complex skeletons have been synthesized and their stproperties relevant to proton conduction elucidated by IR, NThermal stability of all proton conducting phases determined 

• Proton diffusion properties are characterized by pulse field g

echo NMR. Many HPA have high diffusion coefficients and activation energies for diffusion.

• HPA /PVDF: HPA high proton conduction under dry conditio

demonstrated in a PVDF matrix.

• HPA Doped Nafion

®: Nafion

® was doped with various HPA 

interact strongly with the –SO

3H groups and in some cases 

improved proton diffusion.

• These doped Nafion

® membranes were incorporated in ME

tested in a fuel cell, showing dramatic improvements at 120the HPA in these systems are not immobilized this may be a improvements to the membrane/electrode interface.
Accomplishments/Progress 

-- PEM Fabrication and Perfor

• SiO

2 Sol Gel Composite-Polymer Hybrids:

– by simple mixing method– by “Two-Step” method

– by direct copolymerization method– various host polymers– on-going work

• Sol-gel synthetic methods: Several are establis

making HPA-containing sol gel composites with thsilanes

• HPA-containing hybrid PEM membranes: Phys

blending, two-step and direct copolymerization medeveloped.

• Analytical procedures are established for IEC, b

structural, thermal stability analysis, electrical (conand fuel cell performance tests.
Summary

• A variety of HPAs have been succe

synthesized, characterized, and usePEM fabrications.

• A variety of methods for immobilizi

in different polymer matrices have bsuccessfully demonstrated:

– Physical blending/embedding– Sol gel composite-polymer hybr– Flexible, cross-linked, high-STA-loading 

PEMs are obtained for the first time

• FC performance test results indicat

HPA-based PEMs are very promisinhigh-temp operations without the nhumidification.
Future Work

• Understand the synergistic interac

HPA with ionomers in terms of improton conduction at low humidity/elevated temperatures

• Continue to develop immobilizatio

strategies and optimize hybrid HPproton conduction
Hydrogen Safety

The most significant, potential hydrogen associated with this project is fire and/oexplosion due to either leak, ignition, or impact of the highly pressurized H

2 gas 

cylinders, resulting in personnel injuries loss of equipment in the laboratory.
Hydrogen Safety

Our approach to deal with the potential hazard:• A Standard Operating Procedure (SOP) has been implement• All personnel involved in the use of compressed H

2 cylinders 

to take pertinent ES&H training at NREL and familiar with the being authorized for work.

• Personnel protective equipment (PPE) such as safety goggle

are required when present in the lab. Wearing a face shield iwhen changing the pressure regulator.

• The H

2 cylinders are well secured and properly capped when 

NFPA warning labels (e.g., High Pressure Gas, Flammable CH

2) are attached to the cylinders. Valves are only opened to t

pressure.

• No hot work, open fire, and compressed O

2 cylinders are allo

the H

2 cylinders or fuel cell test station.

• Regular check of leaking is conducted with soapy water solu• Fire extinguishers are available in the laboratory.• Emergency response and exit are clearly stated in the SOP a

marked in the lab.