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1 Claudia Leißner November 1st, 2006 About my research work august/september 2006. Prof. Steven Holdcroft Chemistry Department Simon-Fraser-University.

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Presentation on theme: "1 Claudia Leißner November 1st, 2006 About my research work august/september 2006. Prof. Steven Holdcroft Chemistry Department Simon-Fraser-University."— Presentation transcript:

1 1 Claudia Leißner November 1st, 2006 About my research work august/september Prof. Steven Holdcroft Chemistry Department Simon-Fraser-University Burnaby Canada „Fuel cells and proton exchange membranes“ Source:

2 2 Why we need new technologies for producing and saving energy? … and we all know, most of them don`t last for ever (not even the next 50 years)!!! It´s time to change our view Source:

3 3 Thermodynamic efficience for fuel cells and Carnot efficiency for heat engines Source:

4 4 Current  chemical Energy Storage Chemical Energy  Current Renewable energy (e.g. wind mill, solar cells)Cars, notebooks, …

5 5 Current  chemical Energy Storage Chemical Energy  Current Electrolysis Fuel cell Storage Water fuels Renewable energy (e.g. wind mill)Cars, notebooks, … Source:

6 6 We proudly present: our fuel cell car, 100 m with 9.5 cm 3 H 2 !!! You see, it works! Hydrogen producing station (electrolysis) Fuel cell and hydrogen tank inside A driving car The hydrogen tank

7 7 Fuel cell stacks Source:

8 8 PEMFC - Proton exchange membrane fuel cells Source:

9 9 Mission of the membrane… What the proton exchange membrane should do: Proton conductance What the proton exchange membrane should not do: Let pass hydrogen, oxygen, electron and water Swelling too much in the presence of water Working conditions:T<120°C and RH<30%

10 10 Nafion ® – chemical structure Fluorinated backbone (hydrophobic) Side chain with sulfonic acid group at the end (hydrophilic) -> phase separation in the polymer Hydrophobic Hydrophilic

11 11 Water absorption by Nafion ® : phase separated structure hydration Dry Nafion ® membrane cluster-network model Hydrated Nafion ® membrane continuous ionic pathway model

12 12 Proton transport in the pore: Surface conductivity Bulk conductivity Pyoungho Choi, Nikhil H. Jalani, and Ravindra Datta, Fuel Cell Center, Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA. Abs. 864, 205th Meeting, © 2004 The Electrochemical Society, Inc.

13 13 Disadvantages of Nafion ®: Working conditions: at the moment:T>100°C and RH>50% required: T<120°C and RH<30% - Life span is too short - Too expensive - Nafion can hardly be recycled  demand on new membranes with new structures

14 14 Hydrocarbons – new materials? SPEEK – Sulfonated poly(ether ether ketone) cheaper recyclable shorter side chain less hydrophobic backbone (ether and ketone bridges, aromatic rings)

15 15 My research goal: Is this material better than or equal to Nafion ® in respect to? - Water uptake - Conductivity - Concentration of Protons - Proton mobility

16 16 Water Uptake:

17 17 Water Uptake: DVS – Dynamic Vapor Sorption

18 18 DVS Data for Nafion ® PTFE at 25°C - Sorption

19 19 DVS Data for Nafion ® PTFE at 25°C - Sorption

20 20 DVS Data for Nafion ® PTFE at 25°C - Sorption

21 21 DVS Data for Nafion ® PTFE at 25°C – Sorption at 98% RH

22 22 Water Uptake / Lambda Water uptake (WU) = the amount of water absorbed by the dry polymer Lambda (λ) = the number of water molecules per SO 3 H- Group

23 23 Water uptake vs. RH for Nafion ® at 25°C WU RH

24 24 Conductivity:

25 25 Conductivity: Impedance Spectroscopy Measurement system construction Proton conductivity = ability to conduct protons

26 26 Water uptake and conductivity for Nafion ® PTFE at 25°C WU RH Conductivity, S/cm

27 27 Ion Exchange Capacity (IEC) MembraneIEC Nafion PTFE0.54 SPEEK PTFE1.04 Ion exchange capacity = number of sulfonate group/protons per dry mass polymer

28 28 Proton concentration [H + ] Before and after absorbtion = the amount of protons per volume of the wet polymer

29 29 Water uptake, conductivity and proton concentration for Nafion ® at 25°C WU RH Conductivity, S/cm Proton concentration, mmol/cm 3

30 30 Proton mobility, μ = velocity of the protons in an electric field velocity electric field

31 31 Water uptake, conductivity, proton concentration and proton mobility for Nafion ® at 25°C RH WU Conductivity, S/cm Proton concentration, mmol/cm 3 Proton mobility, cm 2 /Vs

32 32 Water uptake vs. RH RH WU Water uptake (WU) = the amount of water absorbed by the dry polymer

33 33 Lambda vs. RH RH Lambda Lambda (λ) = the number of water molecules per SO 3 H-Group

34 34 Conductivity vs. RH RH Conductivity, S/cm Proton conductivity = ability to conduct protons

35 35 Proton concentration vs. RH RH Proton concentration, mmol/cm 3 Proton concentration= the amount of protons per volume of the wet polymer

36 36 Proton mobility vs. RH RH Proton mobility, cm 2 /Vs Proton mobility= velocity of the protons in an electric field

37 37 Proton transport in the pore: Surface conductivity Bulk conductivity Pyoungho Choi, Nikhil H. Jalani, and Ravindra Datta, Fuel Cell Center, Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA. Abs. 864, 205th Meeting, © 2004 The Electrochemical Society, Inc.

38 38 Conductivity vs. and [H + ] RH for Nafion PTFE RH Conductivity, S/cm Proton concentration, mmol/cm 3

39 39 Conductivity and [H + ] vs. RH for SPEEK PTFE RH Conductivityy, S/cm Proton concentration, mmol/cm 3

40 40 Conclusion Different sorption mechanism for Nafion and SPEEK For all membranes and temperatures, the conductivity is increasing with decreasing proton concentration, because of the increasing water uptake -> bigger pores Higher water uptake for SPEEK at 80°C -> lower proton concentration and a higher proton conductivity.  At the moment SPEEK does not provide the same proton conductivity like Nafion and more work on this field has to be done!

41 41 If you want to know more about the best place (one of the best places…) on earth and want to see pictures of the incredible Canadian nature, ask me! THE END THANK YOU FOR LISTENING


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