Bipolar concept for alkaline fuel cells

Alkaline fuel cell stacks are mostly build in monopolar configuration of the cells. At the German Aerospace Center a bipolar plate for alkaline fuel cells has been developed and characterized in a short stack. As a consequence of the sealing concept of the stack two different bipolar plate types are needed. Therefore, the number of cells can only vary by 2 if the end plates are not changed. The single cell as well as the short stack is characterized by various methods, e.g. V–i characteristics, electrochemical impedance spectroscopy (EIS). As a result of the specific electrodes used the differential pressure between electrolyte and gas phase is limited to a few 10 mbar. At higher differential pressures gas crossover through the electrodes and electrolyte takes place with the result that the electrolyte may flood the flow fields. In contrast to PEFC, electrode supported by a metal net as conductor and mechanical support can be used in the AFC. Therefore, the structure of the flow field can be quite simple, this means flow fields with channels with large width and depth are possible. Consequently, the pressure loss over the flow field is very low. The single cell as well as the short stack was operated at overpressures of a few 10 mbar. The AFC can be operated without a compression but with a simple fan. The developed cell design is also used for the characterization of the fuel cell components like electrodes and diaphragms. The test facility for the single cell and for the stack is fully computer controlled and allows the variation of the operation conditions, e.g. flow of the electrolyte, hydrogen flow, oxygen or air flow and cell temperature.

[1]  Mathias Schulze,et al.  Degradation of nickel anodes in alkaline fuel cells , 2004 .

[2]  A. S. Al-Zakri,et al.  Deactivation studies on the porous Ni-gas diffusion electrode in H2/O2 alkaline fuel cell , 1996 .

[3]  N. Wagner,et al.  Preparation of Gas Diffusion Electrodes with Silver Catalysts for Alkaline Fuel Cells , 2003 .

[4]  Karl V. Kordesch,et al.  Fuel cells and their applications , 1996 .

[5]  Mathias Schulze,et al.  Dry layer preparation and characterisation of polymer electrolyte fuel cell components , 2000 .

[6]  Mathias Schulze,et al.  Investigation of the degradation of different nickel anode types for alkaline fuel cells (AFCs) , 2002 .

[7]  Mathias Schulze,et al.  LONG TERM OPERATION OF AFC ELECTRODES WITH CO2 CONTAINING GASES , 2004 .

[8]  R. Savinell,et al.  Methanol-tolerant electrocatalysts for oxygen reduction in a polymer electrolyte membrane fuel cell , 1998 .

[9]  K. Bolwin,et al.  Carbon Dioxide Tolerance of Gas Diffusion Electrodes for Alkaline Fuel Cells , 1994 .

[10]  E. Roduner,et al.  EPR investigation of HO/ radical initiated degradation reactions of sulfonated aromatics as model compounds for fuel cell proton conducting membranes , 1999 .

[11]  N. Wagner,et al.  Degradation of PEFC components , 2000 .

[12]  K. Bolwin,et al.  XPS analysis of PTFE decomposition due to ionizing radiation , 1995 .

[13]  Joachim Nitsch,et al.  Wasserstoff als Energieträger , 1986 .

[14]  Erich Gülzow,et al.  Alkaline fuel cells: a critical view , 1996 .

[15]  Shimshon Gottesfeld,et al.  Low platinum loading electrodes for polymer electrolyte fuel cells fabricated using thermoplastic ionomers , 1995 .

[16]  Mathias Schulze,et al.  PTFE-Bonded Gas Diffusion Electrodes for Alkaline Fuel Cells. , 1992 .

[17]  E. Gülzow,et al.  XPS analysis of the degradation of Nafion , 1999 .

[18]  W. Engelen,et al.  An oxygen electrode for air-consuming proton exchange membrane fuel cells for transportation applications , 1995 .

[19]  N. Wagner,et al.  Innovative production technique for PEFC and DMFC electrodes and degradation of MEA components , 1998 .

[20]  Mathias Schulze,et al.  Long term investigations of silver cathodes for alkaline fuel cells , 2004 .

[21]  P. Adcock,et al.  Stainless steel as a bipolar plate material for solid polymer fuel cells , 2000 .

[22]  Franciska Sundholm,et al.  Degradation of a fuel cell membrane, as revealed by micro-Raman spectroscopy , 2000 .

[23]  Paul Leonard Adcock,et al.  Bipolar plate materials for solid polymer fuel cells , 2000 .

[24]  A. S. Al-Zakri,et al.  Preparation of Raney–Ni gas diffusion electrode by filtration method for alkaline fuel cells , 1997 .

[25]  M. Clifton,et al.  Electrolyte and water transfer through the porous electrodes of an immobilised-alkali hydrogen-oxygen fuel cell , 1996 .

[26]  M. Schulze,et al.  Activation of nickel-anodes for alkaline fuel cells , 2001 .

[27]  Yohannes Kiros,et al.  Long-term hydrogen oxidation catalysts in alkaline fuel cells , 2000 .

[28]  Günther G. Scherer,et al.  Study of radiation-grafted FEP-G-polystyrene membranes as polymer electrolytes in fuel cells , 1995 .