Dynamic Water Management Studies by means of Perforated GDLs and In-situ ESEM Observations

Transcription

1 Dynamic Water Management Studies by means of Perforated GDLs and In-situ ESEM Observations Robert Alink, Dietmar Gerteisen, Christian Sadeler, Christopher Hebling Fraunhofer Institute for Solar Energy Systems ISE Freiburg, Germany Diagnostic Tools for Fuel Cell Technologies , Trondheim

2 Overview Test scope: Examination of the water transport properties of laser perforated of gas diffusion layers In-situ single cell experiments and stack experiments Ex-situ visualizing of water transport in untreated and perforated GDLs in ESEM 2

3 The Fraunhofer Society Itzehoe Rostock Bremen Hannover Berlin Braunschweig Golm Teltow Oberhausen Paderborn Magdeburg Cottbus Dortmund Halle Duisburg Leipzig Schmallenberg Aachen St. Augustin Schkopau Dresden Jena Euskirchen Ilmenau Chemnitz Darmstadt Würzburg Kaiserslautern St. Ingbert Erlangen Nürnberg Saarbrücken Pfinztal Karlsruhe Stuttgart Freising München Freiburg Efringen-Kirchen Holzkirchen DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES Institutes Employees 1.2 Bio Budget 7 Alliances Mikroelectronics Production Technology Information and Communication Technology Materials, Devices Life Sciences Surface Technology and Photonics Defense and Security Research 3

4 Fraunhofer ISE Research & Development, Services DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Research Materials Modelling Methods Development Components Products, Prototypes Systems, Processes Services Consulting, Tests Monitoring Quality Assurance 4

5 Fuel Cell Systems Development of fuel cell systems, stacks and autonomously controlled systems Characterizing and modelling single cells, stacks and systems Control and safety technology 5

6 How can perforation of GDLs help to enhance the performance? Water is generated in the catalyst layer Water flows through small cavities Small filled cavities merge to larger cavities Void space gets filled by liquid water As consequence: water hinders oxygen diffusion 6

7 How can perforation of GDLs help to enhance the performance? Pressure needed for through-plane transport of liquid water is higher than that for in-plane transport Water transport channels (WTCs) support the through-plane transport Decrased saturation and increased oxygen diffusivity 7

8 Investigation of single cell DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Investigation of single cell with an active area of 1 cm 2 Cathode GDL under the channel was perforated by laser treatment Holes have a diameter of 80 μm and a gap distance of 1 mm 8

9 In-situ characterising of GDL water transport properties Dynamic polarisation different operating conditions sweep rate 10 mv/s show hysteresis effect forward backward * without anode polarization 9 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

10 Improving the liquid water transport in the GDL Potential sweep measured with nonmodified GDL 10 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

11 Improving the liquid water transport in the GDL Potential sweep measured with nonmodified GDL Hysteresis knee due to flooding effects 11 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

12 Improving the liquid water transport in the GDL Potential sweep measured with nonmodified GDL Hysteresis knee due to flooding effects Perforated GDL shows lowered pore flooding 12 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

13 Improving the liquid water transport in the GDL Chronoamperometriy mv 13 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

14 Improving the liquid water transport in the GDL Chronoamperometriy Performance improvement ~15% mv 14 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

15 Improving the liquid water transport in the GDL Chronoamperometriy mv 15 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

16 Improving the liquid water transport in the GDL Chronoamperometriy Performance improvement ~20% mv 16 Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell Journal of Power Sources, Vol 177, Issue 2, 1 March 2008, P D. Gerteisen, T. Heilmann, C. Ziegler

17 Investigation of fuel cell stack DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Air cooled stack 6 cells Active area of 6 x 31 cm 2 17

18 Cell stability at 0.71 A/cm 2 DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Stability test at 0.71 A/cm 2 and 63 C 18

19 Cell stability at 0.71 A/cm 2 DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Stability test at 0.71 A/cm 2 and 63 C Voltages of outer cells tend to collaps due to flooding Higher overall performance 3 times less purging steps Increased stability and performance 19

20 Polarisation curve Higher Voltage at constant current Less variation of single cell-voltage Increased stability and performance 20

21 Chronovoltametry Higher Voltage after switching to higher current Lower temperature due to lower mass transport losses Increased stability and performance 21

22 Examination of degradation by freezing water in ESEM ESEM working in water vapor athomsphere All 3 phases of water possible by adjusting temperature and pressure 22

23 Examination of degradation by freezing water in ESEM Freeze / thaw cycling of GDLs before 23

24 Examination of degradation by freezing water in ESEM Freeze / thaw cycling of GDLs 10 x freeze / thaw after before 24

25 Examination of degradation by freezing water in ESEM Freeze / thaw cycling of GDLs 10 x freeze / thaw 10 x freeze / thaw Freeze / thaw cycling of MEAs before after 25

26 Examination of degradation by freezing water in ESEM Freeze / thaw cycling of GDLs 10 x freeze / thaw 10 x freeze / thaw 10 x wet / dry Freeze / thaw cycling of MEAs Wet / dry cycling of MEAs as reference before after 26

27 Liquid water examination in ESEM DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 ESEM working in water vapor athomsphere All 3 phases of water possible by adjusting temperature and pressure 27

28 Ex-situ visualization of liquid water breakthrough in ESEM 800 Pa Water is sucked through a porous membrane and the GDL Visulization of water breakthrough near the GDL surface ESEM E-beam 800 Pa absolute GDL GDL GDL porous membrane 1 C water 1x10 5 Pa absolute 28

29 Transportation of water within an untreated GDL 29

30 Transportation of water within an untreated GDL 30

31 Transportation of water within an untreated GDL 31

32 Transportation of water within an untreated GDL 32

33 Transportation of water within an untreated GDL 33

34 Transportation of water within an untreated GDL 34

35 Transportation of water within an untreated GDL 35

36 Transportation of water within an untreated GDL 36

37 Transportation of water within an untreated GDL 37

38 Transportation of water within an untreated GDL 38

39 Transportation of water within a perforated GDL 39

40 Transportation of water within a perforated GDL 40

41 Transportation of water within a perforated GDL 41

42 Transportation of water within a perforated GDL 42

43 Transportation of water within a perforated GDL 43

44 Transportation of water within a perforated GDL 44

45 Transportation of water within a perforated GDL 45

46 Transportation of water within a perforated GDL 46

47 Transportation of water within a perforated GDL 47

48 Transportation of water within a perforated GDL 48

49 Summary Single cell experiments consistant with stack experiments Significant increase in cell performance and stability achieved New method found to visualize water transport in GDLs in ESEM 49