Mathematical modelling of the MCFC cathode on the linear polarisation of the NiO cathode

Experimental polarisation curves for the porous lithiated NiO cathode used in molten carbonate fuel cells very often exhibit a linear shape over a wide potential range. It is shown by means of mathematical modelling that this linear behaviour can be explained by the interplay of intrinsic electrode kinetics, diffusion of electroactive species through an electrolyte film and the effective ohmic resistance of the pore electrolyte, providing that the cathodic transfer coefficient has a value of about 1.5. In contrast, with the generally assumed value of 0.5 of this transfer coefficient and with reasonable values of the effective electrolyte conductivity, predicted polarisation curves will always bend downwards over the overvoltage region of interest. The evolution of the polarisation curves with increasing electrolyte fill can be simulated by a model according to which the electroactive surface area becomes gradually blocked with the increasing amount of electrolyte.

[1]  Magnus Fontes,et al.  Effects of different design parameters on the performance of MCFC cathodes , 1996 .

[2]  Leis J.M,et al.  Proceedings of the Symposium , 1997 .

[3]  Carina Lagergren,et al.  Mathematical modelling of the MCFC cathode , 1993 .

[4]  K. Hemmes,et al.  A Comparative Study of NiO ( Li ) , LiFeO2, and LiCoO2 Porous Cathodes for Molten Carbonate Fuel Cells , 1994 .

[5]  H. Livbjerg,et al.  A new model for gas diffusion electrodes : application to molten carbonate fuel cells , 1992 .

[6]  J. R. Selman,et al.  Polarization of the Molten Carbonate Fuel Cell Anode and Cathode , 1984 .

[7]  H. Minoura,et al.  Electrophoretically Deposited CdS and CdSe Anodes for Photoelectrochemical Cells , 1983 .

[8]  H. R. Kunz,et al.  A Homogeneous/Agglomerate Model for Molten Carbonate Fuel Cell Cathodes , 1984 .

[9]  Gerald Wilemski.  Simple Porous Electrode Models for Molten Carbonate Fuel Cells , 1983 .

[10]  J. Jewulski,et al.  Model of the isotropic anode in the molten carbonate fuel cell , 1984 .

[11]  A. Appleby,et al.  Reduction of oxygen in alkali carbonate melts , 1977 .

[12]  A. Appleby,et al.  The reduction of oxygen in molten lithium carbonate , 1974 .

[13]  Reduction of oxygen in lithium-potassium carbonate melt , 1980 .

[14]  J. Selman,et al.  Gas Electrode Reactions in Molten Carbonate Media Part V . Electrochemical Analysis of the Oxygen Reduction Mechanism at a Fully Immersed Gold Electrode , 1990 .

[15]  D. Simonsson,et al.  A heterogeneous model for the MCFC cathode , 1995 .