Transient Techniques for Investigating Mass-Transport Limitations in Gas Diffusion Electrodes I. Modeling the PEFC Cathode

The use of electrochemical impedance spectroscopy and current-interruption techniques with the scope of determining mass-transport limitations in PEFC gas-diffusion electrodes is investigated. The porous electrode is assumed to be composed of spherical agglomerates consisting of a homogeneous mixture of the electrolyte and the electronic phase. The model is applied to the O 2 reduction reaction in the cathode and includes Tafel kinetics for the O 2 reduction, Ohm's law for proton migration, Fick's law for O 2 diffusion, and capacitive current due to the contribution of the double layer. A novel impedance is defined, enabling the results to be presented in a simpler manner than with the usual one. It is shown how these transient techniques can be employed to qualitatively separate diffusion from migration effects. The parameter groups that can be quantitatively determined from the processing of experimental data are presented. The effect of O 2 pressure and electrode thickness on the predicted electrode response is also investigated.

[1]  Stuart B. Adler,et al.  Reference Electrode Placement in Thin Solid Electrolytes , 2002 .

[2]  H. Takenouti,et al.  Impedance of a porous electrode with an axial gradient of concentration , 1984 .

[3]  Göran Sundholm,et al.  A Novel Polymer Electrolyte Fuel Cell for Laboratory Investigations and in situ Contact Resistance Measurements , 2001 .

[4]  T. Springer,et al.  Characterization of polymer electrolyte fuel cells using ac impedance spectroscopy , 1996 .

[5]  A. Kornyshev,et al.  Electrochemical impedance of the cathode catalyst layer in polymer electrolyte fuel cells , 1999 .

[6]  C. Cachet,et al.  Couple axial gradients of potential and concentration in a cylindrical pore electrode: an impedance model , 1985 .

[7]  T. E. Springer,et al.  Electrical Impedance of a Pore Wall for the Flooded‐Agglomerate Model of Porous Gas‐Diffusion Electrodes , 1989 .

[8]  E. Gonzalez,et al.  Effect of membrane characteristics and humidification conditions on the impedance response of polymer electrolyte fuel cells , 2001 .

[9]  Yuko Aoyama,et al.  Investigation of the Microstructure in the Catalyst Layer and Effects of Both Perfluorosulfonate Ionomer and PTFE‐Loaded Carbon on the Catalyst Layer of Polymer Electrolyte Fuel Cells , 1995 .

[10]  Göran Sundholm,et al.  In-situ measurements of gas permeability in fuel cell membranes using a cylindrical microelectrode , 2002 .

[11]  I. Raistrick.  Impedance studies of porous electrodes , 1990 .

[12]  J. Selman,et al.  Application of ac impedance in fuel cell research and development , 1993 .

[13]  J. R. Selman,et al.  The Polarization of Molten Carbonate Fuel Cell Electrodes II . Characterization by AC Impedance and Response to Current Interruption , 1991 .

[14]  K. Beccu,et al.  Abschätzung der porenstruktur poröser elektroden aus impedanzmessungen , 1976 .

[15]  J. Jindra,et al.  Porosity and catalyst utilization of thin layer cathodes in air operated PEM-fuel cells , 1998 .

[16]  G. Lindbergh,et al.  Investigation of Mass-Transport Limitations in the Solid Polymer Fuel Cell Cathode II. Experimental , 2002 .

[17]  S. Srinivasan,et al.  Microelectrode Investigation of Oxygen Permeation in Perfluorinated Proton Exchange Membranes with Different Equivalent Weights , 1996 .

[18]  A. Parthasarathy,et al.  Temperature Dependence of the Electrode Kinetics of Oxygen Reduction at the Platinum/Nafion® Interface—A Microelectrode Investigation , 1992 .

[19]  Y. Bultel,et al.  Modeling impedance diagrams of active layers in gas diffusion electrodes: diffusion, ohmic drop effects and multistep reactions , 2002 .

[20]  G. Lindbergh,et al.  Investigation of Mass-Transport Limitations in the Solid Polymer Fuel Cell Cathode I. Mathematical Model , 2002 .

[21]  Shimshon Gottesfeld,et al.  Thin-film catalyst layers for polymer electrolyte fuel cell electrodes , 1992 .

[22]  J. R. Selman,et al.  The Polarization of Molten Carbonate Fuel Cell Electrodes I . Analysis of Steady‐State Polarization Data , 1991 .

[23]  Göran Lindbergh,et al.  Investigation of Porous Electrodes by Current Interruption Application to Molten Carbonate Fuel Cell Cathodes , 1995 .