Dynamic Water Management Studies by means of Perforated GDLs and - PowerPoint PPT Presentation

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 24.06.2009, Trondheim

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 The The Fraunhofer Society raunhofer Society 58 Institutes - 12 600 Employees – 1.2 Bio € Budget Itzehoe Itzehoe Rostock Rostock 7 Alliances Bremen Bremen � Mikroelectronics Hannover Hannover Berlin Berlin Golm Golm Teltow Teltow Braunschweig Braunschweig � Production Technology Oberhausen Oberhausen Paderborn Paderborn Magdeburg Magdeburg Cottbus Cottbus Dortmund Dortmund Halle Halle Leipzig Leipzig Duisburg Duisburg Schmallenberg Schmallenberg Schkopau Schkopau � Information and Communication Technology Dresden Dresden St. Augustin St. Augustin Aachen Aachen Jena Jena Euskirchen Euskirchen Chemnitz Chemnitz Ilmenau Ilmenau � Materials, Devices Darmstadt Darmstadt Würzburg Würzburg Kaiserslautern Kaiserslautern Erlangen Erlangen � Life Sciences St. Ingbert St. Ingbert Nürnberg Nürnberg Saarbrücken Saarbrücken Pfinztal Pfinztal Karlsruhe Karlsruhe � Surface Technology and Photonics Freising Freising Stuttgart Stuttgart München München Freiburg Freiburg Holzkirchen Holzkirchen � Defense and Security Research Efringen-Kirchen Efringen-Kirchen 3

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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Investigation of single cell � 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 μ m and a gap distance of 1 mm 8

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 In-situ characterising of GDL water transport properties Dynamic polarisation curves @ � different operating backward conditions � sweep rate 10 mV/s forward show hysteresis effect * 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL � Potential sweep measured with non- modified 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL � Potential sweep measured with non- modified 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL � Potential sweep measured with non- modified 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL � Chronoamperometriy 700 � 400 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL Performance improvement ~15% � Chronoamperometriy 700 � 400 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL � Chronoamperometriy 600 � 300 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Improving the liquid water transport in the GDL Performance improvement ~20% � Chronoamperometriy 600 � 300 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 348-354 D. Gerteisen, T. Heilmann, C. Ziegler

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

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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Cell stability at 0.71 A/cm 2 � 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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Polarisation curve � Higher Voltage at constant current � Less variation of single cell-voltage Increased stability and performance 20

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Chronovoltametry � Higher Voltage after switching to higher current � Lower temperature due to lower mass transport losses Increased stability and performance 21

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Examination of degradation by freezing water in ESEM � Freeze / thaw cycling of GDLs before 23

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Examination of degradation by freezing water in ESEM � Freeze / thaw cycling of 10 x freeze / thaw GDLs before after 24

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Examination of degradation by freezing water in ESEM � Freeze / thaw cycling of 10 x freeze / thaw 10 x freeze / thaw GDLs � Freeze / thaw cycling of before MEAs after 25

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Examination of degradation by freezing water in ESEM � Freeze / thaw cycling of 10 x freeze / thaw 10 x freeze / thaw 10 x wet / dry GDLs � Freeze / thaw cycling of before MEAs � Wet / dry cycling of MEAs as reference after 26

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

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Ex-situ visualization of liquid water breakthrough in ESEM 800 P 80 0 Pa ESEM � Water is „sucked“ E-beam through a porous membrane and the GDL 1 °C 1 °C 800 Pa absolute 800 Pa absolute � Visulization of water GDL GDL GDL GDL breakthrough near the GDL GDL surface porous porous membrane embrane water water 1x10 5 Pa absolute 1x10 Pa absolute 28

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Transportation of water within an untreated GDL 29

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Transportation of water within an untreated GDL 30

DIAGNOSTIC TOOLS FOR FUEL CELL TECHNOLOGIES 2009 Transportation of water within an untreated GDL 31