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Preparation and characterization of composite PBI membranes for high temperature PEMFC applications

E.C. van de Ven, Z. Borneman, M. Wessling European Membrane Institute Twente

EUROMEMBRANE 2009

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Contents

• ZEOCELL project, theme Energy, FP7
• PBI membrane preparation
• Membrane characterization
• Conclusions

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EU Project, theme Energy, FP7

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Aim of the ZEOCELL project

Traditional Proton Exchange Membrane Fuel Cell:

• expensive

catalyst (noble metal)

• sensitive to impurities

in fuel High temperature PEMFC (130-200°C):

• reaction rate and CO-tolerance increase,
• reduction of operating voltage,
• cogeneration is possible

Challenges: corrosion, electrolyte evaporation, fuel cross over

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• Composite membrane made by synergic combination of

Polymers Ionic liquids Zeolites

Introduction: approach

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• chemically, mechanically

and thermally stable up to 200°C

• porosity

between 15-75%

• pore

size

• f 60 –

500 nm

• proton conductivity

≥ 100 mS/cm at 100°C

• thickness

between 15-150µm

Membrane requirements

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PBI polymer

Membranes based

• n:

Polybenzimidazole (PBI) poly(1,4-phenylene-5,5 (6 )-bisbenzimidazole-2,2 -diyl) A high temperature resistant material (Tg = 327°C) Applied in gas separation and solvent resistant nano filtration

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PBI membrane

Phase separation is needed to prepare porous membranes

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PBI membrane

Preventing

• f macro-void

formation in PBI membranes by delayed phase inversion H2 O H2 O/NMP Macro-voids No Macro-voids

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Membrane morphology results Porosity 65%

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Proton conductivity - pretreatment of the PBI membrane Immersed in ethanol during 1 hour Immersed in hexane during 24 hrs Vacuum oven at 50°C 4 hrs Immersed in IL at 20°C, 24 hrs, atmospheric Vacuum during 15 min. Wiping off excess of IL Measurement with 3 preselected imidazole based ionic liquids

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Proton conductivity – Impedance spectroscopy

PTFE St ai nl ess st eel el ect r

• des

St eel Far adai c cage M em br ane sam pl e BNC connect

• r

s Ther m ocoupl e BNC connect

• r

s

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Proton conductivity – Fitting procedure

T= 20°C

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Proton conductivity- Measurements

Measurements are usually performed at 20°C but we need data in the range of 130-190°C. Solution: measurements done at 60, 50, 40 and 20°C and determine if the proton conductivity shows Arrhenius behavior.

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Proton Conductivity - Results

0.01 0.1 1 10 2.9 3.1 3.3 3.5

1000/T [1/K]

Ln proton cond. [mS/cm]

20°C 40°C 50°C 60°C IL C IL A IL B

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0,001 0,01 2,4 2,5 2,6 2,7 2,8 2,9 3 3,1 3,2

1000/T [1/K] p ro to n c o n d u c tiv ity [m S /c m ]

Proton Conductivity – Results

Ionic Liquid C

40 [°C] 50 60 130 100

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Status

Membrane requirements

• chemically, mechanically

and thermally stable up to 200°C 

• porosity

between 15-75% 

• pore

size

• f 60 –

500 nm 

• proton conductivity

≥ 100 mS/cm at 100°C onwards to 

• thickness

between 15-150µm 

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Conclusions

• Porous PBI membranes have been prepared by delayed phase

separation

• No macro-voids
• Regular porous structure
• Becomes proton conductive by addition of Ionic Liquid
• Proton conductivity shows Arrhenius behavior

confirmed by high temperature measurements

• PBI membranes with Ionic Liquids are a promising candidate for

applications in PEMFC

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Acknowledgements

The Zeocell project was funded by the European Commission under the 7th Framework Program. It was a response on the EC call: Energy Topic 2007.1.1.1: Basic research for materials and processes for PEMFC’s. Grant Agreement nº: 209481.