advanced fluorinated materials for low and high temperature ...advanced fluorinated materials for...

Advanced fluorinated materials for low and high temperature PEM water

electrolyser E. Moukheiber, D. Jones, N. Van Dijk, A. Aricò and L. Merlo

Outline

2

1. Electrohypem: project overview2. Development of innovative PFSA membranes for

PEMWE application :- Short side chain Aquivion® PFSA with high EW- Aquivion ® PFSA composite membranes

3. Conclusion

Enhanced performance and cost-effective materials for long-term operation of PEM water electrolysers coupled to renewable power

sources

• Start date and end date : 01-07-2012 / 30-06-2015

• Consortium :

• Aim : Develop cost-effective components for proton conducting membrane electrolysers with enhanced activity and stability in order to reduce stack costs and to improve efficiency, performance and durability.

3

Electrohypem : Project overview

4

• Membrane activity

Development of short side chain PFSA, hydrocarbon membranes and theirinorganic/organic composite derivatives

• Membrane targets

High conductivity High gas barrier properties (under pressure) Maintain performance at high temperature operation (up to 150⁰C) High mechanical resistance at pressurized operation

Electrohypem : Project overview

Outline

5


PEMWE application :- Short side chain Aquivion® PFSA with high EW- Aquivion ® PFSA composite membranes

3. Conclusion

6

Aquivion® PFSA free radical polymerization scheme:

CF2=CF2

(TFE)

O

CF2

SO2F

CF2

CF2=CF

(SFVE)

O

CF2

SO3H

CF2

(CF2CF )h (CF2CF2 )k

Commonly known as the Short Side Chain (SSC) ionomer

+

+ hydrolysis

The ratio h / k defines the composition of the ionomer, usually described bythe Equivalent Weight = # of grams to have 1 mole of –SO3H groups

SSC Aquivion® PFSA membranes with high EW

7

Different equivalent weights determine different polymer properties:

-—―—―—―—―—-—

-

—

-

Different crystallizable portion

-—―—―—―—―—-

- -

EW crystallinity

hydration swelling

——


8

0

1

2

3

4

5

600 800 1000 1200 1400EW (g/mol)

Hea

t of f

usio

n (c

al/g

)

Membrane Hydration (100°C)

0

20

40

60

80

100

120

140

500 700 900 1100 1300 1500Equivalent Weight (g/eq)

Hyd

ratio

n %

Aquivion extruded membranes

ImprovedBaseline ImprovedBaseline

Expected advantage : higher mechanical resilience given by higher crystallinity and lower hydration (=higher resistance to pressurized operations in liquid water). Higher gas barrier properties (=lower crossover)


Developement of new brand E100-xxS (EW=1000 g/mol):

9

T=80⁰C 1 mg/cm2 IrO2 on TiO20,5 mg Pt (Pt on C)

0

0,2

0,4

0,6

0,05 0,15 0,25 0,35

‐Z" / oh

m.cm

2

Z'/ ohm.cm2


The performances are dependent on membrane area resistance. Some Aquivion® grades behave better than the state of art. Main advantages?

Selected membrane E100-09S :

46 mΩ.cm2 @ 95⁰C

26 mΩ.cm2 estimated at 140⁰C

Selected membrane E100-09S:

46 mΩ.cm2 at 95°C

26 mΩ.cm2 estimated at 140°C

Single cell performance

@ 1,5 V

*216th ECS Meeting, Abstract #830, © The Electrochemical Society Electrochemical Measurement of O2 PermeationRate through Polymer Electrolyte Membranes. Jingxin Zhang, Ruichun Jiang, Wenbin Gu, and Hubert Gasteiger

H2 and O2 Crossover

00,10,20,30,40,5

E100-05S E100-09S E100-18S N115

H2

cros

sove

r [m

A/c

m2 ]

00,81,62,43,2

4

E100-05S E100-09S E100-18S N115

O2

cros

sove

r [m

A/c

m2 ] T40°C, 1bar

T95°C, 2,9 bar

Pt/C (Cathode), IrO2 (anode)*


10

Thin Aquivion membranes presented better permeationproperties than the state of art. Why?


0.2 (mA/cm2) @ 1 bar, 80°C T=80⁰C, Pt/C electrodes,

Fixed Gas Flow: 800 Sccm N2 ‐250 Sccm H2 / 0 barG N2 /H2

11

Differencial pressure testing system ∆P 15bars + Hyoptima

sensor (palladium film) to detect H2 in exhaust O2 stream.

H2 and O2 Crossover


Similar EW but higher crystallinity for SSC


1.51 % H2 in O2 (15 bar ∆P, 55°C) < 2% ( Project target)

11

SSC

LSC

12

Aquivion® PFSA composite membranes

Why ePTFE? - Chemical and thermal resistance

- Compatibility with PFSA material

- Nodes-fibrils structure that guarantees very high vacuum degree (80 to 90 % vaccum)

12

ePTFE structure ePTFE reinforced membrane

Development of ePTFE reinforced R95-04S (EW=950 g/mol, 50µm):

R95-04S (50µm) Vs E100-09S (90µm):

52 mΩ.cm2 Vs 46 mΩ.cm2 at 95°C

13


13

0

20

40

60

80

0 50 100 150 200 250 300St

ress

, (M

Pa)

Strain, (%)

Machine direction (MD)

E100-05SE100-09SE100-18SR95-04S

0

20

40

60

80

0 50 100 150 200 250 300

Stre

ss,

(MPa

)

Strain, (%)

Transversal direction (TD)


Improved mechanical properties for R95-04S : higher young modulus and stress at break

Tensile tests 23⁰C, 50% RH ASTM D638

MEA conductivity from 90⁰C to 150⁰C measured and stability (24hours) at 150⁰C demonstrated. what about ePTFE effect on permeation?

1414




15

00,10,20,30,40,5

E100-05S E100-09S E100-18S N115 R95-04S

H2

cros

sove

r [m

A/c

m2 ]

00,81,62,43,2

4

E100-05S E100-09S E100-18S N115 R95-04S

O2

cros

sove

r [m

A/c

m2 ] T40°C, 1bar

T95°C, 2,9 bar

The presence of the ePTFE does not help substantially in permeability reduction. inorganic fillers or hydrogenated supports?


Pt/C (Cathode), IrO2 (anode)*T=80⁰C, Pt/C electrodes,

Fixed Gas Flow: 800 Sccm N2 ‐250 Sccm H2 / 0 barG N2 /H2

*216th ECS Meeting, Abstract #830, © The Electrochemical Society Electrochemical Measurement of O2 PermeationRate through Polymer Electrolyte Membranes. Jingxin Zhang, Ruichun Jiang, Wenbin Gu, and Hubert Gasteiger

<1.8 V @ 2 A cm-²reached at 80 °C

<1.6 V @ 1 A cm-²reached at 80 °C

1.55 V at 140 °C

Composite membrane of Aquivion and electrospun polysulfone nanofibre mats

0 500 1000 1500 2000

1400

1600

1800

80oC 120oC 140oC

Cell

Volt

age

/ m

V

Curent density / mA cm-2


16

Development of PSU reinforced membranes

Outline

17


PEMWE application :- Short side chain Aquivion® PFSA with high EW- Composite PFSA membranes

3. Conclusion

Conclusion

18

• Short side Chain Aquivion® ionomer with high EW allowed the use of thin membrane with good proton conductivity while maintaining low H2& O2 crossover

• Thin ePTFE composite PFSA membranes (50µm) showed improved mechanical properties and thermal stability however..

• ePTFE support wasn’t effective H2 & O2 crossover reduction. other solutions are under investigation such as ionorganic fillers or electrospun hydrogenated supports (PSU)

• Electrohypem’s selected membrane for scale up E100-09S will bevalidated in terms of performance and stability in an electrolyzer stackat ITM with nominal hydrogen rate production capacity of 1 Nm3 h-1.

19

The authors acknowledge the financial support of the EU through the FCH JU Electrohypem Project.

“The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2010-2013)

for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement Electrohypem n°300081.”

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