Structure and performance of different types of agglomerates in cathode catalyst layers of PEM fuel cells

Abstract In this work, we investigate transport and reaction kinetics in agglomerates of cathode catalyst layers used in proton-exchange membrane fuel cells. Two types of spherical agglomerates are evaluated, which represent limiting structures that can be obtained by distinct synthetic procedures. One type consists of a mixture of carbon/catalyst particles and a proton conducting perfluorosulfonated ionomer (PFSI). The other type consists of carbon/catalyst particles and water-filled pores. The performance of the former type is rationalized on the basis of the well-known Thiele-modulus. Characteristics of the latter type are studied using Nernst–Planck and Poisson equations. Aspects of current conversion, reactant and current distributions and catalyst utilization are explored. In general, the PFSI-filled agglomerates exhibit more homogeneous distributions of reaction rates. Effectiveness factors for these are close to one. However, it was found that proton penetration depths in water-flooded agglomerates could be quite substantial under certain conditions, resulting in unexpectedly high catalyst utilization. The effects of agglomerate radius and of boundary conditions on the agglomerate surface are studied. An approximate analytical solution was obtained for a planar geometry of agglomerates. The significance of these results for the optimization catalyst layers in the light of operation conditions and synthesis methods is discussed.

[1]  H. Ha,et al.  Effect of the catalytic ink preparation method on the performance of polymer electrolyte membrane fuel cells , 2002 .

[2]  E. Passalacqua,et al.  Influence of Nafion loading in the catalyst layer of gas-diffusion electrodes for PEFC , 1999 .

[3]  H. S. Fogler,et al.  Elements of Chemical Reaction Engineering , 1986 .

[4]  G. Lindbergh,et al.  Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode , 2003 .

[5]  T. Springer,et al.  Modeling and Experimental Diagnostics in Polymer Electrolyte Fuel Cells , 1993 .

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

[7]  Yann Bultel,et al.  Electrocatalysis, diffusion and ohmic drop in PEMFC: Particle size and spatial discrete distribution effects , 1998 .

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

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

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

[11]  Y. Bultel,et al.  Catalyst gradient for cathode active layer of proton exchange membrane fuel cell , 2000 .

[12]  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 .

[13]  Jianfu Ding,et al.  Ionic conductivity of proton exchange membranes , 2001 .

[14]  A. Damjanović,et al.  New evidence supports the proposed mechanism for O2 reduction at oxide free platinum electrodes , 1979 .

[15]  P. Pickup,et al.  Ionic Conductivity of PEMFC Electrodes Effect of Nafion Loading , 2003 .

[16]  J. Newman,et al.  Mass Transport in Gas‐Diffusion Electrodes: A Diagnostic Tool for Fuel‐Cell Cathodes , 1998 .

[17]  Mark W. Verbrugge,et al.  A Mathematical Model of the Solid‐Polymer‐Electrolyte Fuel Cell , 1992 .

[18]  Xianguo Li,et al.  Composition and performance modelling of catalyst layer in a proton exchange membrane fuel cell , 1999 .

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

[20]  M. Verbrugge,et al.  Mathematical model of a gas diffusion electrode bonded to a polymer electrolyte , 1991 .

[21]  Shimshon Gottesfeld,et al.  High Performance Catalyzed Membranes of Ultra‐low Pt Loadings for Polymer Electrolyte Fuel Cells , 1992 .

[22]  G. Squadrito,et al.  Nafion content in the catalyst layer of polymer electrolyte fuel cells: effects on structure and performance , 2001 .

[23]  M. Eikerling,et al.  Size effects on reactivity of Pt nanoparticles in CO monolayer oxidation: the role of surface mobility. , 2004, Faraday discussions.

[24]  A. A. Kornyshev,et al.  Modelling the performance of the cathode catalyst layer of polymer electrolyte fuel cells , 1998 .

[25]  Yuko Aoyama,et al.  New Preparation Method for Polymer-Electrolyte Fuel-Cells , 1995 .

[26]  E. Samson,et al.  Modelling ion diffusion mechanisms in porous media , 1999 .