CNR-ITAE Advanced Energy Technologies Institute “ Nicola Giordano”

Messina - Italy

High temperature membranes forDMFC

(and PEFC) (and PEFC) applications.Vincenzo Antonucci

FC Research Manager

PhiladelphiaPhiladelphia , , May May 25, 200425, 2004

CNR-ITAE Advanced Energy Technologies Institute “ Nicola Giordano”

Messina - Italy

High temperature membranes forDMFC

(and PEFC) applications.Vincenzo Antonucci

FC Research Manager

Philadelphia , May 25, 2004

High Temperature Components

CATALYSTS and MEAs MEMBRANES

•resistance to CO up to percentage level •ultra-low loading •chemical and electrochemical stability •low cost •suitability for mass production and scale-up •air oxidant efficient •reciclability, CO2 production analysis •development and assembling of electrodes & MEAs (electrode support, structure and morphology optimisation for HT application, low cost, automated production)

•low resistance •long term chemical and mechanical stability •suitable mechanical strength •resistance to swelling •pinhole free •low cross-over •minimal or no dependence on external humidification •low cost •suitability for mass production and scale-up •reciclability, •CO2 life cycle.

HT MembranesDMFC (dreamcar)

Advantages Drawbacks • Enhanced methanol and oxygen • High pressure requirements

reaction kinetics to maintain good hydration • Lower CO poisoning (coverage) inside the membrane • Better thermal management • cross over?

PEFC (hit cell)

Advantages • Enhanced CO and oxygen

reaction kinetics • Lower CO purification level • Better thermal management • Reduction of radiator size

Drawbacks • New Polymer with no/very

low humidification constrains (high risk)

Membranes APPROACH CRITICAL ASPECTS

1. Composite membranes: Functionalised polymer + inorganic igroscopic Functionalised polymer + inorganic proton

conductor

•T limit 150-180°C determined by functional groups

•High pressure

2. Liquid electrolyte embedded membranes: Polymer matrix PBI + phosphoric acid Polymer matrix PEO + sulfuric or TFMSA

•T limit 150-200°C determined by boiling point of free acid

• Dilution of acid during operation •Corrosion

3. Composite membranes 2: Non functionalised thermal stable polymer matrix + inorganic proton conductive material

High risk •percolation paths, humidity content

T limit ~300°C determined by polymer matrix

4. Ceramic •inorganic ceramic proton conductive electrolytes •inorganic ceramic proton conductive electrolytes embedded in polymeric inorganic matrix

and working T

High risk percolation paths (2nd case)

T limit 350-800°C determined by transport number

Dreamcar EU projectDIRECT METHANOL FUEL CELLS SYSTEM FOR CAR APPLICATIONS

1. realisation and testing of 1.25 kW module Total Power [W] 1250Power Density [mW /cm2] 210Current density [mA /cm2] 500Single cell voltage [V] 0.42Cathode feed airAnode feed Methanol 1M/2MStack temperature [°C] 130

2. realisation and testing of 5 kW module Total Power [W] 5000 Power Density [mW /cm2] 300 Current density [mA /cm2] 600 Single cell voltage [V] 0.5 Cathode feed air Anode feed Methanol 1M/2M Stack temperature [°C] 130/140

Dreamcar EU project

The major overall innovation of the project lies in the development of new materials (especially membranes and catalysts) able to work at

high temperature with reduced metal loading.

225 cm² ACTIVE AREA SINGLE CELL DESIGNpartners

THALES E & C

CR FIAT

CNR – ITAE

SOLVAY

TAU / RAMOT

DMFCCOOLING CHAMBER COOLING CHAMBER

MEAaluminum end-plate

soft PTFE gasket

SS anodic terminal plate

current collector

hard thermoplastic gasket

aluminum end-plate

soft PTFE gasket

SS cathodic terminal plate

current collector

hard thermoplastic gasket

Figure 2

Two mains research routes : - Radiochemical grafting on fluorinated films - Polymers chemical modifications

Improvement of the membranes developed in the frame of the NEMECEL JOE3-CT-0063 Contract

Standard procedure : • β Irradiation of fluorinated films • Grafting : Monomer + Barrier polymer + cross-linking

agent • Functionalisation : Sulfonation and hydrolysis.

Membranes development approach

Sample reference : DREM 03 ( Surface modified membrane)

• Radio-chemical grafting on fluorinated base film (ETFE) • Thickness : 175 µm • Exchange sites: Sulfonic acid • Exchange capacity : 2.1 meq/g • Area resistance: 70 to 90 mΩ.cm² (25°C; HCl 0.1 M; 1000

Hz) • Conductivity: 190 mS/cm • Water absorption : 60 % w

Membranes development approach

Membrane AssessmentMembrane Assessment

90°C 100°C 110°C 120°C 130°C 140°C

Air Feed 1 M MeOH

0.3090°C 100°C 110°C 120°C 130°C 140°C

Air Feed 1 M MeOH

255 mW cm-2

@ 130°C

cm -2

0.25

Cel

l pot

entia

l / V

Pow

er d

ensi

ty /

W

0.20

0.15

0.10

0.05

0.000 0.2 0.4 0.6 0.8 1 1.2 1.4

Current density / A cm-2 0 0.2 0.4 0.6 0.8 1 1.2 Current density /A cm-2

Anode Catalyst 85% PtRu/C Cathode Catalyst 60% Pt/C

Membrane DREM 04(100microns)

Hyflon

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

1.4

MembraneMembrane AssessmentAssessment

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 20 40 60 80 100 120 140 160 180

Time / min

C ur

rent

de n

s ity

/ A c

m-2

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Pow

e r d

e ns i

ty /

W c

m -2

Current density Power Density

0.4 V

T= 130°C

Stability test @ 130°C

Membrane Membrane AssessmentAssessment

0.3

0.4

0.5

0.6

0.7

0 50 100 150 200 250 300Time / min

Cur

rent

den

sity

/ A

cm-2

0

0.05

0.1

0.15

0.2

0.25

Pow

er d

ensi

ty /

W c

m-2

Current density Power density

0.4 V

Stability test @ 140°C

Membrane AssessmentMembrane Assessment Composite recast Nafion®-inorganic filler membranes

•Enhanced water retention properties at high temperatures • DMFC operation up to 145 °-150 °C • Good chemical and electrochemical stability • Reduced methanol cross-over

•Better understanding of the operation mechanism of these electrolytes •Effects enhancing the proton conductivity at 150 °C•Role of surface chemistry (filler) and morphology (filler and membrane)•Effect of pressure

PWA-SiO2

SiO2

Variation of cell resistance values as a function of temperature in DMFCs Effect of the inorganic filler

0.18

0.16

0.14

Nafion-SiO2/PWA (3%) Nafion-SiO2 (3%) Nafion-ZrO2 (3%)Nafion-Al2O3 n (3%) Nafion-Al2O3 b (3%) Recast Nafion

Cel

l re

sist

ance

/ oh

m c

m2

0.12

0.1

0.08

0.06

0.04

0.02

0

80 100 120 140 160 Temperature / °C

T = 145°C oxygen feed

0

0.2

0.4

0.6

0.8

0 .5 1 .5 2 .5

Current density / A cm-2

Cel

l pot

entia

l / V

Nafion-SiO2-PWA (3%) Nafion-SiO2 (3%) Nafion-ZrO2 (3%) Nafion-Al2O3 n (3%) Nafion-Al2O3 b (3%)

DMFC polarization curves at 145 °C

0 1 2

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 0.4 0.8 1.2 1.6 2 2.4 Current density / A cm-2

Pow

er d

ensi

ty /

W c

m-2

Nafion-SiO2-PWA (3%) Nafion-SiO2 (3%) Nafion-ZrO2 (3%) Nafion-Al2O3 n (3%) Nafion-Al2O3 b (3%)

Oxygen feed T = 145°C

DMFC power densities curves at 145 °C

100

150

200

250

300

350

400

450

2 4 8 pH slurry

Max

imum

pow

er d

ensi

ty /

mW

cm

-2

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Cel

l re

sist

ance

/ o

hm c

m2

Maximum power density

Cell resistance

Maximum power density and cell resistance of composite membranes-based DMFCs at 145 °C as a function of the pH of slurry of the inorganic filler.

Composite recast Nafion®-inorganic filler membranes

3 7 6 5 9

Acid-base properties of and conductivity of composite membranes at 150 °C

Acidic surface OH groups facilitate water co-ordination which acts as vehicle for proton migration

DMFC performance increases as the pH of slurry of the inorganic filler in the membrane decreases

Operation at low pressure does not influence significantly hydration/conductivity characteristics of composite membranes at 150 °C

High oxygen partial pressures are needed for proper cathode operation in the presence of methanol cross-over.

The ionic conductivity of the composite membranes at high temperatures may be increased by appropriate tailoring of the surface characteristics of the added ceramic oxides

Composite recast Nafion®-inorganic filler membranes

inorganic fillers play a key role for the water uptake

0.3 CNR catalys ts

E-Te k catalysts 255m Wcm -2

Air Feed 1 M MeOH

Comparison @T= 130°C

Pcat= 2.5 bar

210m Wcm -2

DREM 04 Me m brane (100 m icron in thickness)

Catalysts developments0.25

Pow

er d

ensi

ty /

W c

m-2

Pow

er d

ensi

ty /

W c

m -2

0.2

TP

Stirrer Burette

pHmeter

ATC Liquid Pump

Tank

Reactor temperature control

Vent

Tank

Vent

Filter

0.15 Tank

0.1

0.05

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4

Current density / A cm -2

0.35

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Current density / A cm-2

1.5 bar

2 bar 2.5 bar 3 bar

Comparison @T= 140°C

287m Wcm -2 @ 3 bar

248m Wcm -2 @ 2 bar

271m Wcm -2 @ 2.5bar

187m Wcm -2 @ 1.5 bar

Anode: 85%PtRu/C Cathode: 60%Pt/C

DREM 04 Mem brane

Air Feed 1 M MeOH

0.30

0.25

0.20

0.15

0.10

0.05

0.00

High Temperature HiT Cell (proposal)

MEMBRANES Cooperative action :

DC, VW, Toyota E, Opel A

Time frame S M L Operation temperature 20°C - 100 °C -10 °C - 120 °C -30°C - 160°C

Electric propertiesProton conductivity [S/cm] @ 20 % RH stable for 48H 0.1 S/cm @ 100°C

0.05 S/cm @ 20°C

0.1 S/cm @ 120°C

0.05 S/cm @ -10°C

0.1 S/cm @ 120°C

0.05 S/cm @ -30°C @ 0 % RH, stable for 48H 0.1 S/cm @ 120°C

Mechanical properties Minimum tensile Strenght [Mpa]

measured in 90 °C water in 2 directions thickness 25 µ

25 25 25

Elongation at break [%] measured at 90 °C

dried during 1 hour @ 100 °C in 2 directions thickness 25 µ

> 100% > 200% > 200%

Max swelling in water at 95 °C < 10 % < 5 % < 5 %

Tg fully soaked in water 20 ° above max

operating temperature thermal cycle stability to

be defined thermal cycle stability to be defined

Cost

cost per m² low lower 20 /m² @ 1000000 m² volumes per year